Dr. Albert Einstein
Dr. Carl Sagan
History of Rocket Development - Space Exploration
By: Dr. Frank J. Collazo
July 18, 2005
Dr. Wernher Von Braun
Dr. Robert Hutchings Goddard
Dr. Edwin Powell Hubble
Introduction: This report reflects on the history of rocket development, its growth to date, and some of the principal contributors through the years.
Early Military Rockets: In the early 1800s, British inventor William Congreve noted reports of Indian rockets employed against British forces. Congreve greatly improved rockets as weapons by attaching warheads or bombs that would explode after the rocket was launched, and by increasing the range of rockets. These Congreve rockets were accurate and powerful enough to use against the firearms of the early 1800s. The rockets still used poles, or sticks, to stabilize the rockets in flight. Britain used Congreve rockets against the United States in the War of 1812 (1812-1815), and other countries copied the rocket design.
Development of Rockets: Despite their stabilizing poles, Congreve rockets were often inaccurate. In the 1880s, Russian teacher Konstantin Tsiolkovsky theorized that rockets might be useful for space-flight. In 1844 British inventor William Hale invented the stickless or spin-stabilized rocket, in which the exhaust gases caused the rocket to spin in flight. The spinning helped stabilize the rocket, eliminating the need for the clumsy guide-stick and making the rocket more accurate. By the 1890s, the gunpowder war rocket finally fell out of use as guns improved and again became more accurate weapons than rockets. Although Sir Isaac Newton wrote his third law of motion in the 1680s, few scientists recognized that this law applied to rocket motion.
Isaac Newton discovered the law of universal gravity, which shows that the strength of gravity declines according to the square of the distance between objects. Thus when you go twice as far away from an object, you feel one-fourth the strength of its gravitational force. But each object in the universe retains some gravitational pull, however minuscule. If you go nine-tenths of the distance toward the Moon, the Moon’s gravity becomes stronger than Earth’s gravity. If you go one-hundredth of the distance toward the Sun, the Sun’s gravity becomes stronger than Earth’s gravity.
French mathematician Joseph Louis Lagrange (1736-1813) worked out a set of solutions to describe how the gravitational attraction between two large objects and their orbital velocities balance each other such that a small body placed in the orbital plane of the larger bodies will remain balanced there. He found five such points at which smaller objects remain balanced.
Most scientists still believed that rockets moved because their exhaust gases pushed against air, so rockets could not be used in the vacuum of space. In 1903 Tsiolkovsky began publishing his theories, but his early writings were not circulated outside his native Russia.
In World War I (1914-1918), rockets were used only as signals and simple anti-balloon weapons. Meanwhile, American physicist Robert H. Goddard evolved his own theories, independently of Tsiolkovsky, about the use of the rocket for space flight. Goddard also began experimenting with new solid-fueled rockets.
After World War I, the Treaty of Versailles prohibited Germany from building and using heavy artillery. For this reason, the German Army Ordnance Department tried to replace this missing link in German armaments by rockets. Such an endeavor seemed reasonable, based on advances shown by many amateur rocket groups operating in several European cities. One group in the Berlin area had become well known having Hermann Oberth, Rudolf Nebel, and Wernher von Braun as their members. Demonstration firings at the private rocket field at Reinickendorff convinced the German Army to employ a small nucleus of this group and to support their work with funding to be provided from the Ordnance Department.
The German Army decided to relocate these efforts to an Army base at Kummersdorf. It soon became apparent that the Berlin environment was not conducive to rocket flights, and it was decided in the mid-thirties to establish a rocket development facility at Peenemünde on the Baltic Sea Island of Usedom at the mouth of the Oder River.
In spite of the wartime conditions and many ups and downs, the work progressed rather satisfactorily, and at the end of World War II a new potent weapon had been developed, the ballistic missile known by its builders as the A-4.
It was designed to use liquid propellants (incl. LOX) to make it easily transportable. The use of a turbo pump for the pressurization of the propellants was a major advance to realize this need. This permitted lightweight tanks, so that the missile could be erected in the field at almost any launch location. The German rocket troops were trained to erect 3 missiles at a time, and to fuel, align, and launch them in a matter of two hours. About 1,000 of these missiles were fired at the cities of London and Norwich, while about 2,000 more were fired at targets on the European continent. Another 500 or so were used in test and training launchings, while a total of about 10,000 had been built and shipped from a central German assembly facility located in the Hartz Mountains, in the vicinity of Nordhausen, also known as the Mittelwerke. Many missiles were still in the pipeline to the front, or had been rejected by the troops because of problems and damage.
These accomplishments impressed the Allied Forces to such a degree that they became interested in learning more about the design, operations, and tactical uses of the A-4, which had meanwhile been renamed the V-2 by Hitler's propaganda Minister Josef Goebbels.
The British launched three V-2's from the Cuxhaven area. They used captured German soldiers who had served in missile firing units. A small group of German engineers from Peenemünde had also been brought to the launch site. They had to supervise testing and preparation of the captured V-2's and had to approve the final assembly and use for a flight. Only a few German rocket engineers joined the British missile program. The Russians reactivated the Mittelwerk facility and assembled V-2's at that location but relocated this activity soon to an area near Moscow. The Russians had already started an active rocket development program during the war. The French eventually hired several former Peenemünde workers and initiated their own missile program shortly after the war's end.
In 1919 the Smithsonian Institution published Goddard’s findings in a small booklet called A Method of Reaching Extreme Altitudes. In this booklet, Goddard wrote about his use of smokeless powder as an improvement over gunpowder and how instrumented rockets could help explore the upper atmosphere. He also briefly mentioned the theoretical possibility of an unpiloted solid-fueled rocket reaching the Moon. Goddard’s theory was widely published in newspapers and helped make the world conscious of the possibility of rocket-powered space flight. Goddard, a shy man, continued his experiments with more secrecy.
In 1921 he began experimenting with liquid propellants. On March 16, 1926, Goddard launched the world’s first liquid-fueled rocket, though few people knew about it at the time. Goddard’s overall impact was therefore less than generally believed.
During this same time period in Germany, Rumanian-born mathematics teacher Hermann Oberth independently developed his own theories on space-flight. In 1923 Oberth published Die Rakete zu den Planetenräumen (The Rocket into Interplanetary Space), which was about liquid-propellant rockets for piloted space flight. Die Rakete had an even larger impact than Goddard’s booklet and led to an international space flight movement, which was especially strong in Germany.
In the 1920s and 1930s space flight and rocketry clubs sprang up in Europe (especially Germany) and the United States and undertook their own experiments. The most important of these groups was the Verein für Raumschiffahrt (VfR, or Society for Spaceship Travel). The VfR started their experiments in 1930. During the same year, Goddard moved his experimental work away from populated areas to a location near Roswell, New Mexico. He was looking for privacy, safety, and good launching weather.
World War II: In 1932 the German Army hired Wernher von Braun, a bright young member of the VfR, for its own secret rocket program. The program started modestly, but funding increased with the approach of World War II (1939-1945). In 1937 the German Rocket Research Center opened at Peenemünde with von Braun as its technical director. Contrary to a popular misconception, the Germans were unaware of the details of Goddard’s work and developed their rockets independently.
During World War II, the Germans developed a variety of solid- and liquid-fueled missiles that were more sophisticated than those of the Allies. The most important of these missiles was the A-4, later called the V-2, the world’s first large-scale liquid-fueled rocket with a thrust of 250,000 N (56,000 lb) and a range of about 300 km (about 200 mi). At the war’s end, both the United States and the Union of Soviet Socialist Republics (USSR) scrambled to capture V-2 parts, plans, and scientists. United States troops brought V-2 material and personnel, including von Braun, back to the United States.
Rocket Pioneers: Goddard, Robert Hutchings (1882-1945), American rocket engineer, was born in Worcester, Massachusetts and educated at Worcester Polytechnic Institute and Clark University. From 1909 to 1943 Goddard taught physics at various institutions, including Worcester Polytechnic Institute and Princeton and Clark universities. His interest in rocketry began in childhood, and in 1919 he published a short book, A Method of Reaching Extreme Altitudes, proposing a rocket that might reach the moon. In 1923 he tested the first rocket engines to utilize liquid fuel; previously only solid fuels had been used. In 1926 he launched the first liquid-fuel rocket, using a mixture of gasoline and liquid oxygen. In 1929 he sent up the first instrument-carrying rocket, which bore a barometer, a thermometer, and a small camera.
From 1930 to 1942, with the aid of a Guggenheim Foundation grant, he worked in New Mexico. His experiments included the construction of rockets that reached a velocity of 885 km/h (550 mph) and heights of up to 2 km (1.5 mi), and he accumulated more than 200 patents related to rocketry. During World War II (1939-1945), for two years he was director of research for the Bureau of Aeronautics of the U.S. Department of the Navy, and for the last two years of his life he served as a consulting engineer for the Curtiss-Wright Corporation aircraft manufacturers.
Goddard’s work was virtually ignored in his own country during his lifetime. His rocket designs shared many similarities with the weaponry developed by German rocket engineers during the 1930s and World War II. This caused many people to believe that the Germans had obtained and used copies of Goddard’s work in their development of the V-2 rocket. However, Goddard’s secrecy had prevented the Germans from learning much about his work, and the similarity of design was mostly coincidence. It was not until after the war that Goddard’s work was publicized and subsequently became the foundation for later space exploration. See also Rocket; Space Exploration.
Rocket pioneer Walter Dornberger died in July. During World War II, Dornberger served as a German officer in charge of advanced rocket research, including the awesome V-2 ballistic missile. Wernher von Braun served under Dornberger's command during V-2 research and production. After the war, Dornberger became an adviser to the U.S. Air Force and an executive at Bell Aerosystems. James S. McDonnell, head of McDonnell Douglas Corporation, a giant of the aerospace industry, died August 22 at the age of 81. In Switzerland, alpine rescue expert Fritz Buehler died August 22 at the age of 71. A veteran alpinist and flier, he became head of the Swiss Air Rescue Service in 1959, building it into an organization that became a model of its kind.
Von Braun, Wernher (1912-1977), German-American engineer, was known for his development of the liquid-fuel rocket. Von Braun was born in Wirsitz (now Wyrzysk, Poland). He received a Ph.D. degree from the University of Berlin in 1934. Von Braun began experimenting with rockets in his youth. From 1937 to 1945 he was director of the German Rocket Research Center at Peenemünde on the Baltic Sea, in charge of developing the V-2 long-range liquid-fuel rocket used to bombard England during World War II (see Rocket). In 1944, Dr. Von Braun led the effort of the V2 rocket for Germany in which he was recognized as the inventor of the V2 rocket.
In 1945 he came to the U.S. as technical adviser to the U.S. rocket program at the White Sands Proving Grounds in New Mexico. In 1950 he was transferred to Huntsville, Alabama, where for ten years he headed the Redstone Missile program. Von Braun was naturalized a U.S. citizen in 1955. He encouraged the Board of Trustees to establish a University in Huntsville to train engineers in the field of the hard sciences. From 1960 to 1972, as associate director of NASA's space program, he helped develop the Saturn rocket used in the Apollo moon flights. The Von Braun Civic Center houses the Huntsville Museum of Art. The U.S. Space and Rocket Center, a complex with a large collection of missiles, models, working simulators, and the Mercury 7 and Apollo 16 spacecraft, is located nearby and hosts the U.S. Space Camp devoted to teaching children about space exploration. He was admitted to the National Hall of Fame in 1982.
The Redstone missile stood over 19 m (64 ft) tall, measured 1.8 m (6 ft) in diameter, and weighed about 18,200 kg (40,100 lb) at liftoff. It had one stage, or engine, adapted from the V-2, fueled by a combination of ethyl alcohol and liquid oxygen. Although it was capable of carrying a nuclear or conventional warhead (bomb) to a target 640 km (400 mi) away, Department of Defense restrictions limited Redstone’s operational range to 320 km (200 mi). The United States began stationing Redstone missiles in Western Europe in 1958. These missiles were part of an effort to support U.S. allies during the Cold War, the power struggle between the United States and the Union of Soviet Socialist Republics (USSR) that followed World War II.
In 1957 the U.S. Army modified the missile to create Jupiter C, a three-stage version of the Redstone capable of traveling higher and farther into space. Jupiter C stood 21 m (69 ft) tall and, like its predecessor, burned ethyl alcohol and liquid oxygen. Later that year the Army incorporated a fourth stage and renamed the rocket Juno I. The Juno 1 Redstone rocket burned higher energy Hydyne fuel. The first U.S. rocket capable of launching an artificial satellite into Earth orbit, a Juno I launched Explorer I, the first U.S. satellite to orbit Earth, in 1958.
In 1960 the National Aeronautics and Space Administration (NASA) ordered further changes to create a launch vehicle for use in the Mercury Program, the United States’ first piloted space program. Improvements included lengthening the first stage and again increasing Redstone’s power. The Mercury-Redstone, as the upgraded rocket was called, could launch a single-passenger Mercury capsule weighing 1.9 metric tons to a maximum distance of 480 km (300 mi) above Earth’s surface. The rocket stood over 25 m (82 ft) tall with a Mercury capsule on top and burned alcohol and liquid oxygen.
The first Mercury-Redstone launch failed in November 1960 when the engine shut down immediately after takeoff. Mercury-Redstone 2 successfully carried Ham, a chimpanzee, into space in January 1961. Ham survived the trip, indicating that humans could endure space travel in the Mercury capsule. Four months later, Mercury-Redstone 3 took Shepard to a height of 187 km (116 mi) above the Earth. The Mercury-Redstone 4 flight by American astronaut Virgil I. Grissom in July of that year marked the last Redstone space launch. The more powerful Atlas rocket launched subsequent Mercury missions. The Army retired the Redstone in 1964, but Redstone components were used in the Saturn IB rocket until 1975.
Post World War II Era: Shortly after the end of World War II, the USSR and the United States disagreed over the control of Europe and entered a period of tense relations called the Cold War. The Cold War included a race to develop rockets as weapons and as launch vehicles for the space race, a contest for “firsts” in space. The Cold War also gave rise to increasingly advanced missiles, which led to an uneasy balance of power between the two nations for several decades.
Goddard’s Stability Control System: In order to build safe launch vehicles and accurate missiles, engineers needed to improve rocket stability and control. Robert Goddard used aerodynamic air vanes for his early liquid-fueled rockets. These air vanes helped stabilize and steer rockets by deflecting in desired directions the air through which the rockets moved. Goddard also succeeded with another control—a battery-operated gyroscope within the rocket. The gyroscope was linked to exhaust vanes and straightened the rocket when it began to tilt.
The V-2 rocket used a similar method of control. The exhaust gases passed over a set of four heat-resistant, movable, gyro-controlled graphite exhaust vanes. When the rocket swerved, the vanes were moved to deflect the exhaust, forcing the rocket back to a straight path.
Operation Paper Clip: The Allied Forces showed, after the war, great interest in learning more about this new weapon and its military applications. The U.S. War Department decided to bring a number of German scientists and engineers to this country for interrogation, as well as to demonstrate through actual experimentation the use and operation of these new systems. About 500 specialists were brought here under "Operation Paperclip" for this purpose.
The story of 118 of these rocket scientists after arrival in this country is recorded in history. During a period of five years in Fort Bliss, Texas, these scientists taught a team of U.S. Army personnel and people from General Electric, a support contractor, the skills for testing, assembling, and finally launching a V-2 ballistic missile. The launchings took place at the U.S. Army Missile Range of the White Sands Proving Ground in New Mexico. After extensive modifications, two of the last few missiles were taken to Florida where they were launched from what is now known as the Cape Canaveral Test Range.
After the White Sands firings, the Army relocated the group of scientists to the Redstone/Huntsville Army Ordnance Arsenal. There, the first large U.S. ballistic missile, the Redstone, was designed, developed, and deployed. So was the Jupiter, with its increased firing range. The Jupiter was the first U.S. IREM (Intermediate Range Ballistic Missile) and was successfully deployed in Italy, Turkey, and Great Britain.
In 1948 the experimental U.S. MX-774 missile pioneered the technique of gimballing, in which the liquid-fueled rocket engine could be tilted for precise steering and stability in its flight. The following year, the Viking sounding rocket started using small maneuvering thrusters around the vehicle. This method was widely adopted and is often used in conjunction with gimballing.
The U.S. Army provided the Redstone missile with a booster stage for the launching of the first U.S. satellite, the Explorer. It also "boosted" the first manned missions, and provided the first basic transportation into space for Alan Shepard and Gus Grissom. In 1961 President John F. Kennedy announced the intention of landing the first man on the Moon. The Saturn series of space boosters helped to fulfill this dream. The Saturn I flew several missions, demonstrating the capability of the "cluster design" principle of rocket engines, as well as other features.
The huge Saturn V, which eventually carried men to the Moon, was proof of the feasibility of space travel, not only to the Moon but also to the planets. The role of the German "Rocket Team" in this achievement will be discussed in the perspective of its far-reaching importance for the future of mankind.
Rockets for Space Flight: In the early 1950s, more than 60 captured V-2 rockets were tested at the U.S. Army’s White Sands Proving Grounds in New Mexico. The V-2s gave the Americans valuable experience in handling large rockets, while von Braun’s team helped the Americans develop their own missile program. The first American von Braun rocket was the Redstone, developed in 1951. The engine in the Redstone was a great improvement over that in the V-2. The V-2 had a cumbersome arrangement of 16 cup-shaped injectors, leading some rocket engineers to dub the V-2 “a plumber’s nightmare.” The Redstone used an engine that was originally meant for the Navaho missile and had a flat plate into which the injectors were set.
The task of the German group was to instruct the Army personnel and the support contractor (General Electric) in the handling, operation, and launch procedures, so that the Americans could eventually take over this entire process without any support from the Germans. The launched missiles were used for scientific purposes and measured, for the first time, temperatures, pressures, air composition, and radiation levels at these unexplored altitudes. These missiles, especially the warheads research program, had to undergo in many cases major modifications. Thus, the U.S. space research program got its start at that time and concluded in the launch of 66 modified V-2's. Eight missiles were eventually modified for the use of a second stage, the JPL-developed WAC Corporal as an upper stage. This configuration, also called the Bumper-WAC, established an altitude record of almost 250 miles, which remained a record for many years.
But we have gotten ahead of ourselves! Let's go back to Fort Bliss and White Sands. Another task of the group of rocket people was to propose follow-on projects. After von Braun had made some most ambitious proposals with little chance for obtaining the necessary funding, one proposal was to attach a ramjet as a second stage to a modified V-2, or possibly a future Army missile. Due to many technical and political difficulties, this project never sustained life, although some follow-on work was taken to Huntsville and continued there for a few years. Projects of this type are now being discussed again.
The Army was apparently impressed with the work of this group, as well as with the performance of the launched V-2's, and it was decided to establish a permanent Army facility for the research and development of guided missiles and rockets. This triggered the move to Huntsville, Alabama, in the summer of 1950. At that time, several members departed from the group and joined private industry (General Dynamics, Convair, NAA, Lockheed), where they eventually took leading positions. Another small group that had worked on the Loki Project moved north in order to continue their development work there for an Army contractor.
The city fathers of Huntsville were initially reluctant to welcome the rocket people since they had hoped to attract an Air Force facility for the testing of high-speed vehicles, which later on became the Arnold Engineering and Development Center near Tullahoma, Tennessee. This Air Force facility eventually attracted a number of Paperclip personnel. As it turned out, the Army rocket work grew into a much larger and economically more important activity than originally anticipated.
Original tasks at the new location were the continuation of the ramjet work started at Fort Bliss. But the Army wanted mostly to pursue the development of an American ballistic missile, which later on became known as the Redstone. It had many features very similar to the V-2: it used the same propellants, and an improved but still similarly designed power plant. But it featured an advanced guidance and control system, especially a warhead that could be separated in order to overcome a major problem of the V-2, which was the disintegration of the vehicle during the re-entry phase, the feared re-entry bursts. The Redstone was deployed by the U.S. Army for several years in Europe. It was the U.S.'s first medium-sized ballistic missile.
From the progress in rocketry, it became apparent that it would be possible by the use of upper stages to put a payload into an Earth orbit and to create an Earth satellite. In the framework of the International Geophysical Year (IGY), the United States and the Russians agreed to proceed with such a project and to launch earth satellites for scientific purposes. President Eisenhower decided not to use a military missile system like the Redstone for these U.S. satellite carriers, and he ordered the Navy to undertake the development of the Vanguard Project for the IBY launches.
In the meantime, the Russians had proceeded with great success with the development of their missiles, leading up to an ICBM launch in the summer of 1957. To meet their part of the IGY agreement, they used this same vehicle with minor modifications for the launch of their Sputnik satellite on October 4, 1957, to the surprise of the world. The second Sputnik launch even demonstrated the survivability of living beings in space, with the launch of the dog Laika. This happened before the United States could launch its first IGY mission.
After these two Russian successes, the first two launch attempts by the United States within the IGY framework using the Vanguard launch vehicle were dismal failures. After these two mishaps, the Army Ballistics Missile Agency (ABMA) was finally given approval to prepare a modified Redstone missile for the launch of a satellite as the U.S. contribution to the IGY.
This launch vehicle had been in storage for several years; it had originally been prepared for test launches of ablative nose-cones to demonstrate the capability to survive re-entry from space. Several launches of this type had already proven this feature using Redstone vehicles with two solid propellant upper stages furnished from the Jet Propulsion Lab in Pasadena, California. This demonstration was to verify the re-entry capability of the Jupiter-IRBM nose cone. This vehicle had been prepared for the same purpose, and the simple addition of an extra solid propellant upper stage gave it an orbital capability. A proposal to use this combination under the name "Project Orbiter" had been turned down by the Administration. With it, a U.S. satellite could have been orbited a year or two prior to the Russian launch.
This Explorer I launch put Huntsville, Alabama, for the first time, on the map. Further feats were to come. The launch of the dog Laika indicated that one Russian goal would be manned space flight. To demonstrate the U.S. capability of a safe re-entry from space flight, a modified Jupiter warhead carried two monkeys during a ballistic flight. They both survived and had thereby shown that the ablative system for nose-cone re-entry would also be safe for human survival during return from space.
Based on these experiences, the Redstone vehicle, which was now known as "Old Reliable," was called upon again, this time to carry Alan Shepard and Gus Grissom as the first two U.S. astronauts into space on top of a Redstone-Mercury configuration, and to recover them. Unfortunately, the Russians again had launched their cosmonaut Yuri Gagarin, a few weeks earlier. And Gagarin also orbited the Earth, something the one-stage Redstone-Mercury could not do. John Glenn was the first American to orbit; he used a modified Atlas-ICBM almost a year after Shepard's flight for that purpose.
These two Redstone missions--the Explorer and the Redstone-Mercury flights--opened the door for the von Braun rocket team to participate in more ambitious missions of the future. When President Kennedy announced the intention of landing men on the moon and bringing them back alive, he called on NASA's Marshall Space Flight Center to furnish a new NASA to furnish the transportation to the Moon. The Center had just been established as a new NASA Field Center. It was staffed by most of the people on the Rocket Team, now including many American technicians, engineers, and scientists. Marshall is located on Federal property managed by the U.S. Army Redstone Arsenal's Support Agency.
While still with the U.S. Army, the rocket team had already started the development of a large booster by "clustering" eight Jupiter engines underneath a central Jupiter tankage and a set of eight Redstone tanks arranged in a circle around it. This design created a powerful first stage for multi-stage missions, and became finally the Saturn I booster, which made a series of early test flights for the Apollo lunar landing program. This booster was improved later on, and finally propelled about a dozen additional Saturn IB flights for practice missions prior to traveling all the way to the Moon for landing.
Since people doubted the reliability and dependability of such an eight-engine cluster. It was decided to develop a new, and very powerful engine. It was named the F-1 engine and became the main booster element of the Saturn V launch vehicle. Without all these early activities, the lunar landing would most likely not have taken place in the sixties, as President Kennedy had wanted.
In order to try out the newly developed J-2 engine, which had been developed for the use of hydrogen and oxygen, it was decided to modify the second stage of the Saturn I for its initial use. Since this change resulted in a much more powerful rocket, it was named the Saturn IB. This configuration found extensive use in several demanding pre-lunar missions, since it permitted testing of all systems required for the lunar landing; except that all these preliminary tests had to be done in Earth orbits, not in the vicinity of the Moon. This permitted the program to proceed with utmost assurance that all components performed well, and no major design flaws were hidden in this most complicated system of components and software.
In summary, it can be said that the impact of the presence of the Rocket Team on American space technology has been impressive. Most of the credit for these accomplishments has to go, of course, to the leader of the group: Dr. Wernher von Braun. His charisma, his vision, his technical and managerial abilities were the driving force behind all the described activities. He enticed the team members to stay with the group, although they all could have doubled their pay by joining private industry. Wernher von Braun could convince his superiors that his ideas were realistic, deserving of support, and should be implemented as proposed. The successful and timely completion of the lunar landing is the most impressive accomplishment of the German-American team of rocket engineers and space scientists and will be noted in the annals of human history for all time to come.
Besides their technical contributions, the Rocket Team and its work also had a great impact on the city of Huntsville, Alabama and surrounding areas. In the beginning, the town had a population of about 16,000 people. Today, Huntsville and Madison County itself have a population of about 180,000 people.
In addition, there have been other improvements. The city now has a symphony orchestra, established with the help of several German members. Members of the team also built on the top of Monte Sano, just north of the city, the Von Braun Astronomy Facility. The Von Braun Civic Center, was built as a result of the economic improvements brought by the space program in Huntsville. Educational needs in the town were initially served by a branch of the University of Alabama. This branch has now grown into a major Alabama University, which is endeavoring to be a leader in many areas of space sciences. The U.S. Space and Rocket Center, a complex with a large collection of missiles, models, working simulators, and the Mercury 7 and Apollo 16 spacecraft, is located in Huntsville, AL and hosts the U.S. Space Camp, devoted to teaching children about space exploration.
It all started with the desire to travel into the Solar System, and eventually to conquer the universe. The first small steps had to be fostered by financial support from government sources for military purposes--in this country as well as at Peenemünde. This was realistically the only approach which could be taken, and which finally paved the way to the Moon.
Konrad Dannenberg was former director of rocket motor development in Peenemünde; former director, Redstone Rocket production in Huntsville; former deputy program manager of the Saturn booster project that put first men on the Moon and later, a space station program manager until 1973. He now serves as consultant to the Alabama Space and Rocket Center in Huntsville.
Missile Cold War: At the same time that the USSR and the United States were racing to build rockets to get them farther into space, the two countries were constantly striving to build bigger ballistic missiles. Ballistic missiles with the power to travel between the two countries are typically three-stage rockets carrying nuclear warheads. Ballistic missiles are designed to destroy targets in enemy countries, but the sheer number and power of the missiles that both countries had in their possession acted as a deterrent to either country ever launching one. The energy put into the ballistic missile programs did benefit the space program, because many rockets designed for missiles were ultimately used as launch vehicles.
The first U.S. Intercontinental Ballistic Missiles (ICBMs), such as the Atlas and the Titan, used liquid propellants. The preparation time, including fueling, of these missiles was long, causing military planners to consider the missiles vulnerable to attack. The next generation, Titan II, saw improvements in its safe, ordinary temperature, hypergolic (meaning that the oxidizer and fuel ignite on contact) liquid propellant, which cut down the preparation time to a minute. Titan IIs were also kept and launched from underground bombproof structures called silos. Sliding doors in the silo roof opened just prior to launch. The next generation ICBM, the solid-fueled Minuteman, required even less maintenance than its liquid-fueled predecessors, but also launched from silos. During the Cold War, plans were made to carry and launch missiles from specially equipped trains to make detection of the missiles’ location more difficult for the enemy. These schemes were never enacted.
Reusable Rockets - The Space Shuttle: Rockets such as the large missiles and launch vehicles in the U.S. Atlas or Titan families, were first introduced in the 1950s and were expendable. Each rocket could be used only one time, and each was very expensive. The world’s first reusable rocket engines were those that propelled the space shuttle, which was first flown in 1981. The solid rocket boosters that launch the shuttle into orbit can be retrieved and refurbished but are not really reusable. The reusable engines are actually part of the orbiter (the planelike craft often thought of as the shuttle). The space shuttle’s main engine has a built-in electronic controller computer that automatically monitors, regulates, and records all phases of the engine. This computer insures utmost reliability and makes the engine the most sophisticated liquid-fueled rocket engine ever developed. Each of the shuttle’s three engines, clustered at the rear of the orbiter, generates about 1.65 million N (about 375,000 lb) of thrust.
October 4, 1957 - The Soviet Union launched Sputnik I, the first artificial satellite to be placed in orbit around the earth.
June 1958 - Selection of the Mercury Astronauts: The seven original Mercury astronauts were selected, having been culled from a total of 69 prospective candidates. The seven original Mercury astronauts were Scott Carpenter, Gordon Cooper, John Glenn, Virgil "Gus" Grissom, Walter Schirra, Alan Shepard, and Donald "Deke" Slayton.
January 31, 1961 - Chimpanzee Ham: A Redstone rocket launched a Mercury space vehicle from Cape Canaveral with Ham, a 37-pound chimpanzee, as its passenger in a sub orbital flight.
April 12, 1961 - The Soviet cosmonaut, Yuri Gagarin, became the first human to be launched into orbit around the earth aboard the Vostok I spacecraft.
On May 5, 1961 - Alan Shepard made the first manned sub orbital flight in the Freedom 7 spacecraft.
July 21, 1961 - Virgil Grissom became the second American to make a sub orbital flight aboard the Liberty Bell 7 spacecraft.
August 6, 1961 - The Soviets launched the second man to orbit the earth, Gherman S. Titov, aboard the Vostok II spacecraft.
September 13, 1961 - An unmanned Mercury spacecraft was successfully launched into orbit with a mechanically simulated pilot on board. The Atlas booster, which had a series of earlier launch failures, performed well.
February 20, 1962 - Astronaut John Glenn became the first American to be launched into orbit by an Atlas rocket booster aboard the Friendship 7 spacecraft, with some 60 million persons watching live on television.
August 11, 1962 - Andrian Nikolayev was launched into orbit aboard the Vostok III, and on August 12, Pavel Popovich joined him in orbit aboard the Vostok IV. In orbit, the two spacecrafts achieved a near-rendezvous.
October 3, 1962 /May 15, 1963 - Gordon Cooper was launched aboard the Faith 7 spacecraft on a 22-orbit flight. Walter Schirra was launched aboard the Sigma 7 spacecraft on a six-orbit flight.
June 12, 1963 - James E. Webb, NASA Administrator, announced that there would be no more Project Mercury flights, scrubbing one final flight that had been planned.
November 1966 - Edward White II, on the second Gemini mission, became the first American to perform a space walk outside of his spacecraft.
July 16, 1969 - There were 4 manned Apollo missions before Apollo 11 was launched on July 16, 1969, on its way to landing the first men, Neil Armstrong and Edwin Aldrin, on the moon (Michael Collins remained in orbit in the command module).
How Many People Have Walked on the Moon: Six National Aeronautics and Space Administration (NASA) Apollo missions reached the Moon from 1969 to 1972. Many people at that time hoped that the Apollo program would lead to a permanent station on the Moon, and it is very disappointing to realize that nobody has been to the Moon in about 30 years. Each lunar-landing Apollo mission (which began with Apollo 11) carried three people into orbit around the Moon. One of the astronauts then remained in the command module, while two others used the lunar module to descend to the Moon’s surface.
Apollo 11/ First Moon Landing: The first Moon landing was made by Neil Armstrong and Buzz Aldrin in Apollo 11’s lunar module, named Eagle, on July 20, 1969. Armstrong’s first words on the Moon were “That’s one small step for man, one giant leap for mankind.” There has been much discussion over the years as to why he didn’t say “for a man,” and there has been speculation that the word “a” was merely swallowed by a radio glitch, but the consensus seems to be that Armstrong just said “step for man,” perhaps out of nervousness. Armstrong became a professor of engineering and shunned public appearances, although he was arguably the most famous person in the world. Aldrin has recently coauthored a novel, The Return, which is a murder mystery involving the commercialization of space tourism.
Apollo 12: Pete Conrad and Alan Bean landed on the Moon in Apollo 12’s lunar module, Intrepid, in November 1969. Conrad quipped, “That may have been a small one for Neil, but it’s a long one for me.” Conrad, always a daredevil, died in a motorcycle accident in 1999. Bean, an artist, has painted space scenes.
Apollo 13: Apollo 13 suffered an explosion en route to the Moon. The astronauts were able to return safely to Earth, but they missed their chance to walk on the Moon.
Apollo 14: Apollo 14’s lunar module, Antares, shuttled Alan Shepard and Ed Mitchell to the Moon’s surface in February 1971. The long hiatus was the result of the commission of inquiry over the cause of the Apollo 13 explosion. Shepard was chief of the Astronaut Office until he retired from NASA and later went into business. He died in 1998.
Apollo 15: Apollo 15’s lunar module, Falcon, carried Dave Scott and Jim Irwin to the lunar surface in July 1971. They were able to go farther on the Moon than earlier astronauts because they had a vehicle, the Lunar Rover. With it, they were able to cover 27.3 km (17 mi). Scott had the idea of demonstrating the physics experiment of dropping a feather and a hammer in the Moon’s airlessness. Confirming Galileo’s experiment (which traditionally involved dropping weights off the Leaning Tower of Pisa), the feather and the hammer landed simultaneously, something shown in video clips to generations of science students since. Irwin retired from NASA to form a religious organization. He has since died.
Apollo 16: John Young and Charles Duke went to the lunar surface in April 1972 in Apollo 16’s lunar module, Orion. They landed in the highlands, a rougher and therefore more dangerous region to explore than the smoother areas that NASA had chosen for the earlier flights. Young later became chief of NASA’s Astronaut Office. Duke retired from the astronaut corps to go into business; he also has a religious ministry.
Apollo 17: Apollo 17’s lunar module, Challenger, carried Gene Cernan and Jack Schmitt to the Moon’s surface in December 1972. Schmitt was the only Ph.D. scientist and the only trained geologist to walk on the Moon. He later became a United States senator. Cernan went into business and is currently president of Cernan Energy Group, an energy and aerospace consulting company.
Apollo 18 to 20: Scientists looked for Apollo 18 to 20 for those scientific opportunities, but these missions were cancelled for financial reasons.
Originally, NASA planned for longer missions to eventually take place, once the Apollo program got the bugs out. These longer missions were intended to accomplish more scientific investigations. A few spacecraft went back to the Moon in the 1990s, notably the Clementine and Lunar Prospector missions in 1994 and 1998, respectively. President Bush’s vision for NASA’s space exploration includes a human visit to the moon and following that, human exploration of Mars.
Rockets also have numerous peaceful purposes. Upper atmospheric research rockets, or sounding rockets, carry scientific instruments to high altitudes, helping scientists carry out astronomical research and learn more about the nature of the atmosphere.
Jet-Assisted-Take-Off (JATO) rockets help lift heavily loaded planes from runways. Lifesaving rockets carry lifeline ropes to ships stranded offshore. Ships in distress can launch signal rockets to signal for help. Rocket ejection seats safely boost pilots out of jet planes during emergencies. Fireworks have provided entertainment for centuries, and model rockets form the basis of a popular hobby.
People use all kinds of rockets for the same basic purpose: to carry objects through air and space. Missiles carry explosive devices to targets, while sounding rockets carry scientific instruments into the upper atmosphere. Launch vehicles boost satellites and other spacecraft into space, and smaller thruster rockets steer or stabilize spacecraft in space.
Sounding Rockets: Scientists use sounding rockets to carry scientific instruments into the upper atmosphere to take measurements of air quality, radiation from space, and other data. Many countries use sounding rockets to monitor weather and pollution. Engineers enable a rocket to reach its target altitude by shutting down the rocket at a specific height. The rocket then coasts upward until air friction and gravity stop its upward movement and cause it to fall back to Earth. The instruments usually include a radio transmitter that sends measurements back to Earth. Some sounding rockets carry parachutes that allow their controllers to recover the rocket and the instruments, but some fall back to Earth without a parachute. Engineers design a sounding rocket’s flight path so that the rocket will fall into the ocean or into an uninhabited area in order to avoid damaging property or hurting people.
Solid–fueled sounding rockets are far simpler to launch than missiles. Sounding rockets are usually light and portable, often requiring only a rail to stabilize the rocket for its first seconds of flight. An early type of sounding rocket called Aerobees used launch towers that were small enough to carry aboard ships. The ships carried the rockets to good positions from which to observe solar eclipses or other phenomena that scientists wished to study.
Tactical Deployment: The term missile actually means any object thrown at an enemy and includes arrows, bullets, and other weapons. In modern military usage, however, missile usually means an explosive device propelled through the air by a rocket or an air-breathing engine. (Air-breathing engines differ from rockets in that rockets carry their own oxygen, while air-breathing engines get their oxygen from the air as they fly through it.)
Missiles can be launched from the ground, from airplanes, and even from submarines. Some missiles are designed to hit targets in the air, while others are built to hit targets on the ground. Some missiles, called guided missiles, have steering systems that guide them to their target.
The most important consideration in launching missiles is minimizing the opportunity that the enemy will have to attack the missile while it is on the ground. Missiles launched from open ground are usually solid-fueled or storable liquid-fueled rockets, because they require much less preparation time than cryogenic liquid-fueled rockets. Cryogenic liquid-fueled rockets take too long to fuel to be safe in the open. Some missiles are launched from within silos (covered, bombproof underground tubes). Cryogenic liquid-fueled missiles are often stored in and launched from silos.
Some rockets that perform as missiles can be launched from airplanes. Air-launched missiles are fired from special racks called pylons underneath the plane. When ready to launch, the missiles fall from the pylons until they are a safe distance from the airplane, then they ignite. This method prevents the missile’s hot exhaust from harming the aircraft.
Some surface-to-air missiles, such as the Hawk, are carried and launched on mobile launchers. Trident missiles are launched from huge, upright tubes inside a submerged submarine. A blast of gas forces the rocket through the top of the tube and out of the water. When safely clear from the submarine, the missile automatically ignites and heads toward its target.
LaunchVehicles: Launch vehicles send satellites and other spacecraft into space. These vehicles must be far more powerful than other types of rockets, because they carry more cargo farther and faster than other rockets. To place an object into orbit around Earth, the launch vehicle must reach a velocity of about 30,000 km/h (about 18,500 mph). To escape Earth’s gravitational pull entirely and head into deep space, these rockets must attain a velocity, called an escape velocity, of about 40,000 km/h (about 25,000 mph). Engineers have found that the most efficient way for launch vehicles to reach this speed is to use staged rockets, or rockets divided into different stages, one atop another.
Launches to the Moon of the Saturn V vehicles, which were 111 m (363 ft) tall, used larger, more streamlined mobile launch platforms. Today, the space shuttle uses the fixed Launch Umbilical Tower (LUT), which has elevators and swing arms for servicing the shuttle. The largest land vehicles ever built, the 2,700-metric-ton giant crawler transporters, carried the Saturn V to the launch pad. Giant crawlers still carry the space shuttle to its launch pad.
Thrusters: Many spacecraft use small rockets called thrusters to move around in space. Thrusters can change the speed and direction of a spacecraft. They allow a spacecraft to steer in space, to jump to a higher orbit, or to fall back to Earth.
Newton’s Laws Application to Space - Stability and Control
First Law of Motion: Engineers apply Sir Isaac Newton’s first law of motion to control rocket stability. This law states that an object in motion tends to stay in motion. The specific case of this law used in rocket stability is that a spinning body tends to keep spinning in the same orientation. One application of this law is to make the rocket spin. A spinning rocket is resistant to directional changes, making its flight more stable. Spin-stabilized rockets use special fins, or vanes, in the path of their exhaust. The vanes are oriented so that the rocket spins as the hot exhaust passes over the vanes.
Many rockets use gyroscopes (instruments that also employ Newton’s first law) to track their orientation. Gyroscopes consist of a spinning disk mounted in a base that allows the disk to move freely, but the mounted base moves with the rocket. A power source, such as a battery, keeps the disk spinning. Because spinning objects tend to maintain their orientation, the angle of the disk to the base changes when the rocket and subsequently the gyroscope base change orientation. Automatic systems track the relative positions of the parts of the gyroscope to track changes in the rocket’s orientation. The system can make movable exhaust vanes direct the flow of the exhaust to change the rocket’s direction based on gyroscope readings.
Some rockets can change the orientation of their engines to direct the flow of the rocket exhaust. This technique, called gimballing, can be used with movable exhaust vanes and small thrusters along the rocket edge to provide even better stability and control.
For each action there is an equal and opposite reaction: The motion of a rocket is much like the motion of a balloon losing air. When the balloon is sealed, the air inside pushes on the entire interior surface of the balloon with equal force. If there is an opening in the balloon’s surface, the air pressure becomes unbalanced, and the escaping air becomes a backward movement balanced by the forward movement of the balloon.
Rockets produce the force that moves them forward by burning their fuel inside a chamber in the rocket and then expelling the hot exhaust that results. They carry their own fuel and the oxygen used for burning their fuel. In liquid-fueled rockets, the fuel and oxygen-bearing substance (called the oxidizer) are in separate compartments. The fuel is mixed with the oxygen and ignited inside a combustion chamber. The rocket, like the balloon, has an opening called a nozzle from which the exhaust gases exit. A rocket nozzle is a cup-shaped device that flares out smoothly like a funnel inside the end of the rocket. The nozzle directs the rocket exhaust and causes it to come out faster, increasing the thrust and efficiency of the rocket.
Some early scientists believed that rocket exhaust needed something to push against (such as the ground or the air) in order to move the rocket. Rockets traveling in the vacuum of space, however, demonstrated that this belief was not true. In fact, rockets produce more thrust in the vacuum of space than on Earth. Air pressure and friction with the air reduce a rocket’s thrust by about ten percent on Earth as compared to the rocket’s performance in space.
Thrust/Propellant Efficiency: Thrust is a measurement of the force of a rocket, or the amount of “push” exerted backward to move a rocket forward. Thrusts vary greatly from rocket to rocket. Engineers measure thrust in units of weight or force (Newton’s [N] in the metric system and pounds [lb] in English measurements).
Specific impulse measures the efficiency and power of rocket engines and propellants. Specific impulse (Isp) is the thrust produced per kilogram or pound of propellant per second. Measuring Isp is similar to measuring the efficiency of cars in kilometers per liter or miles per gallon. Modern solid propellants have specific impulses of about 3,400 to 3,900 N per kg per second (about 350 to 400 lb per lb per second) and advanced liquid propellants typically have Isps of about 4,200 to 4,400 N/kg/second (about 425 to 450 lb/lb/second).
Exhaust velocity, or the speed at which exhaust leaves the rocket, is another way to measure rocket performance. The higher the exhaust velocity, the greater the thrust. Propellants with higher exhaust velocities also have higher specific impulses. Exhaust velocities can range from 600 to 900 m/sec (2,000 to 3,000 ft/second) for gunpowder, 2,000 m/sec (8,000 ft/second) for a mixture of liquid oxygen and gasoline, to 4,000 m/second (12,000 ft/second) or more for a mixture of liquid oxygen and liquid hydrogen. Rocket engine performance also depends on the design of the combustion chamber and nozzle and the pressure of the propellant.
Staging: Rockets are very powerful, but it is often more efficient to use several rockets rather than a single rocket to move an object to the desired place. Launch vehicles often use more than one rocket engine, or stage, during a mission. In rockets that use stages, the stages are stacked on top of each other. The stage on the bottom of the stack is the first one to fire. In some rockets that use stages, the first stage has additional rockets attached to the outside, acting as boosters to further increase the thrust. Rockets can theoretically use any number of stages, but the complications caused by coordinating the firing times of the stages make it impractical to have too many. The huge Saturn V rocket that sent Apollo astronauts to the Moon had four stages, including the Apollo spacecraft’s own rocket.
The first and most powerful stage lifts the launch vehicle into the upper atmosphere. The first stage then separates from the rest of the rocket and falls toward Earth. Some first stages, such as the space shuttle’s booster rockets, can be recovered. Others, such as the first stage of the huge Saturn V Moon rocket, burn up in the atmosphere once their fuel is expelled. Then they drop off the launch vehicle.
The second stage carries less weight than the first stage, because the first stage has dropped off the rocket. When the second stage takes over, the vehicle reaches a much higher speed; the second stage, however, also uses up its fuel and drops off. The third stage fires and places the spacecraft into orbit (for a mission designed to orbit Earth). On deep space missions, the third stage allows the spacecraft to reach escape velocity and head away from Earth. For some missions, three stages are not adequate.
Types of Rocket Propulsion: There are three basic types of rocket propulsion: chemical, nuclear, and electrical. Chemical rockets use chemicals, in solid or liquid form, for fuel and oxidizer, or the chemical that contains the oxygen needed to burn the fuel (together, the fuel and oxidizer are called the propellant). Nuclear rockets use the heat of nuclear reactions to heat chemical propellants for combustion. Electrical rockets use electric and magnetic fields (regions of space affected by electrical and magnetic energy) to accelerate and expel ions and elementary particles. Ions are atoms with positive or negative electrical charges, and elementary particles such as protons, neutrons, and electrons are the tiny building blocks of matter that make up atoms.
Chemical Rockets: Chemical rockets are suitable for many purposes. Large solid-fueled and liquid-fueled chemical rockets act as launch vehicles or as missiles that are capable of traveling from continent to continent. People use smaller chemical rockets as sounding rockets, as missiles with shorter ranges, or as the upper stages of launch vehicles. Small liquid-fueled chemical rockets make good thrusters because the burning of their fuel can be stopped and restarted whenever the spacecraft needs a course correction. Solid-fueled rockets and liquid-fueled rockets that use fuel at ordinary temperatures are the best chemical rockets for missiles. Combustion, or burning, takes place inside a cup-shaped container called the combustion chamber at the rear of the rocket. The exhaust nozzle, which is engineered to provide the greatest thrust for the particular propellant used, leads from the combustion chamber to the bottom of the rocket. The narrow part of the nozzle, between the hemispherical combustion chamber and the nozzle itself, is called the throat. Nozzles are made with material that is resistant to heat, because they must be able to withstand very high temperatures.
Solid Fueled Rockets: Solid-fueled rockets are the most simple rockets. They have two main parts: the body, or case, where the propellant is stored, and the combustion chamber with its attached nozzle. The case holds the propellant and opens to the combustion chamber at one end. Most cases are cylindrical, but the cases of some rockets that are used to move objects through space are spherical. The solid mass of propellant is called the charge, or grain. Solid-fueled rockets often use electrically heated wires called igniters to heat the propellant to its ignition point (the temperature at which the propellant catches fire). Igniters are threaded through the nozzle to the bottom of the propellant or through a hole in the propellant farther up in the grain.
Solid rocket fuels of the past included gunpowder and mixtures containing nitroglycerin and nitrocellulose that were called double-base propellants. Current fuels are called composite fuels and are composed of synthetic rubbers or plastics with additives. These additives include binders that hold the fuel together, powdered metals that increase specific impulses, and chemicals that control the speed at which the propellant grain burns. Usually, the faster a rocket burns, the more thrust it produces. The rocket also uses up its fuel faster if the fuel burns faster. Engineers must take the burning rate into account when they design solid-fueled rockets, because stopping the propellant from burning once it has ignited is very difficult. Rockets such as booster rockets, which must produce large amounts of thrust in a short period of time, use chemicals to increase the burning rate. Other rockets that need to produce less thrust over a longer period of time use chemicals to decrease the burning rate. The longer-burning rockets are called sustainers. A few types of rockets have small tanks and pumps that can spray water or another extinguisher on the propellant to stop its burning.
Engineers can make composite fuels in several separate segments, then stack and join them together in the rocket case to produce extremely large, powerful, and long-duration motors. The huge solid rocket boosters of the space shuttle are put together in sections and are capable of about 13 million N (about 3 million lb) of thrust. The shuttle’s solid rocket boosters are presently the world’s largest solid-fueled rockets. Star-shaped cavities in the propellant blocks increase thrust by increasing the surface area of fuel available for burning. This increase in surface area allows the propellant to burn faster.
Engineers seek to make rockets as light as possible in order to maximize their efficiency. About 90 percent of the weight of a modern solid-fueled rocket is propellant, but decreasing the weight of the case still increases the rocket’s efficiency. Using heat-resistant fiberglass and heat-resistant plastic helps lighten the materials used in the case, and special techniques for building the cases help reduce the amount of material needed while maintaining the cases’ strength.
Liquid Fueled Rockets: Liquid-fueled rockets carry their own fuel and oxidizer in liquid form. The liquids are stored in tanks in the rocket case and are pumped into the combustion chamber as needed. Liquid fuels generally provide greater specific impulses than solid fuels, mainly because the liquid fuels are denser. Engineers can control combustion in liquid-fueled rockets by simply changing the rate at which the pumps move the liquid. Engineers can stop combustion by stopping the pumps completely. Stopping and restarting combustion can be very useful in space missions, because course corrections or steering may require only short bursts from the rockets.
Safety Hazards: Liquid-propellant systems are more complex to handle than solid-fueled systems. Liquid-fueled rockets require separate oxidizer and fuel tanks, and many systems need high speed, lightweight pumps and injectors to spray fuel into the combustion chamber. The simplest liquid-fueled rockets use a non-reactive pressurized gas, such as nitrogen gas, to force the propellants into the combustion chamber. The non-reactive gas is held under pressure in a tank above the fuel tanks. Valves between the tanks open when fuel is needed in the combustion chamber. The pressure of the gas entering the fuel tank forces the liquid propellant into the chamber. More complicated liquid-fueled rocket systems use pumps to move the fuel and oxidizer between their holding tanks and the combustion chamber.
Types of Fuels and Oxidizers: Liquid-fueled rockets use several types of fuels and oxidizers. Some rockets use familiar liquid fuels such as alcohols, gasoline, and kerosene. The oxidizer used with these fuels is most often liquid oxygen—oxygen gas that is cooled and compressed to a liquid form. Kerosene is the most popular fuel for modern rockets.
Other compressed and cooled gases, such as hydrogen, perform as fuels in some liquid-fueled rockets. When a substance stays in liquid form even though its temperature is colder than its freezing point, or the point at which it should become a solid, the substance is called super cooled. Super cooled gases used as liquid fuels are called cryogenic (from the Greek word cryo for “cold”) fuels (see Cryogenics).
Hyperbolic Propellants: Some liquid-fueled rockets use oxidizers and fuels that begin burning as soon as they come in contact with each other. Such propellants are called hypergolic, and they greatly simplify a rocket’s ignition system. Some cryogenic fuel-oxidizer combinations are also hypergolic. Monopropellant rockets mix and store the fuel and oxidizer together.
Igniters: Other types of igniters include small explosive powder charges and pieces of metal that heat up when an electric current flows through them until they ignite the propellant. Some rockets that do not use hypergolic propellants as their main source of power may use small amounts of hypergolic propellants to ignite their main propellant. The combustion of the hypergolic propellant often takes place in a small chamber that opens into the main combustion chamber. Another method of igniting propellants is to use catalysts (chemicals that encourage certain chemical reactions to occur) to start a reaction that produces enough heat to ignite the propellant.
Burning Propellant Temperature: Liquid propellants burn in rocket engines at an average temperature of about 3,000° C (about 5,400° F). By comparison, the melting point of steel is about 1,370° C (about 2,500° F). Engineers must provide a way to cool the combustion chamber in order to keep the rocket engines from melting if the rocket will burn for more than a few seconds.
Regenerative Cooling: A cooling technique called regenerative cooling involves circulating the fuel around the outside of the rocket engine before burning the fuel. The heat of the combustion in the engine transfers to the circulating fuel, cooling the engine surfaces and warming the fuel. Many fuels burn more efficiently if they are heated before burning. In a process called film–cooling, special fuel injectors spray the fuel and oxidizers on the interior walls of the combustion chamber. The heat of the walls causes the liquid to evaporate, cooling the walls in the same way as sweat cools a human body. The propellant vapor then burns in the center of the combustion chamber.
Spaghetti Design: Most modern large liquid-fueled engines, such as the Space Shuttle’s Main Engine (SSME), use a design of combustion chamber called the spaghetti design. These chambers are called spaghetti chambers because hollow cooling tubes resembling strips of pasta form the walls of the combustion chambers. These chambers are well cooled and much lighter, yet stronger than previous chambers.
Cryogenics Propellant: Cryogenic propellants pose many of the same challenges to engineers that storable propellants do. The combustion temperatures of cryogenic propellants are generally higher than those of storable propellants, so the techniques for cooling the rocket engines need to be even more efficient. In addition, rockets that use cryogenic propellants must have ways of keeping the fuel cold enough to keep it from evaporating. Liquid hydrogen and other liquefied gases are usually made by compressing the gases under extreme pressure and at low temperatures. The gases are cooled in steps using special equipment. Liquefied gases must also be stored monopropellant and transported in leak-free insulating containers to maintain their cryogenic temperature and prevent the liquid from evaporating, or turning back into gas and escaping into the atmosphere.
Hypergolic and liquid-fueled rockets have only slight differences from the other types of liquid-fueled rockets. Systems in which an inert gas presses the fuel into the combustion chamber (pressure-fed systems) often use hypergolic propellants. Hypergolic propellants burn at about the same temperature as storable propellants, so rockets that use hypergolic propellants still need to provide a way to keep the rocket engines cool.
Monopropellant rockets generate much lower thrusts than those generated by all types of bipropellant rockets, or rockets that use a separate fuel and oxidizer. Monopropellant rockets are very useful, however, because they are simple, lightweight, and have only one propellant tank. Monopropellants burn at significantly lower temperatures (well beneath the melting point of steel) than other propellants, so cooling structures are not as important. Small monopropellant rockets serve as course-adjustment or attitude control systems for spacecraft. Most monopropellant rockets used for these applications can be stopped and restarted, and have variable levels of thrust.
Hybrid Chemical Rockets: Hybrid rocket engines use both liquid and solid fuels. Usually, the liquid oxidizer is injected onto the solid synthetic rubber fuel and ignited in the combustion chamber. Hybrid systems combine advantages of both solid- and liquid-fueled systems. Hybrid propellants are inexpensive, and their burn rate can be controlled by regulating the oxidizer flow. Hybrid rockets are still experimental and have not been widely used, but several rocket manufactures are testing hybrid systems. Hybrid propellants have specific impulses of around 2,900 N/kg/s (300 lb/lb/s), which is comparable to that of cryogenic liquid propellants.
Nuclear Rockets: Nuclear rockets are very powerful rockets that are theoretically capable of acting as launch vehicles and long-distance space travel systems. No nuclear rocket has yet made it into space, but experimental rockets have undergone tests on Earth. The complexities of building safe nuclear rockets and worries about using rockets that are carrying radioactive materials have limited the practical use of nuclear rockets.
Nuclear rockets generate thrust by using nuclear reactions to heat liquid hydrogen to a superheated gas, or a gas heated well beyond its boiling point, that shoots out of the rocket nozzle. In the nuclear reactions that occur, called fission reactions, heavy atoms such as uranium and plutonium split apart to produce lighter elements and energy. Nuclear rockets could produce much higher specific impulses than chemical systems, because nuclear rockets heat propellants to higher temperatures. Specific impulses of nuclear rockets are 7,800 N/kg/second (800 lb/lb/second) or more. In one form of nuclear rocket engine, a small nuclear reactor (similar to one used to produce electricity on the ground) superheats liquid hydrogen circulated through the reactor. Another type of nuclear rocket, called a gaseous fission nuclear rocket, offers specific impulses of 14,000 N/kg/second (1,400 lb/lb/second) or more. Gaseous fission rockets create an intensely hot fireball by splitting atoms of uranium-233 gas or a similar fuel. As before, liquid hydrogen is pumped in and converted into a superheated gas that exits the nozzle.
Safety Hazards of Nuclear Fission: A fission reaction releases most of its energy in the form of heat, which helps power the rocket. Fission reactions also release other types of radiation in the form of gamma rays and fast-moving neutrons. Both gamma rays and these fast neutrons can be harmful to the rocket body and to any living things nearby. The intense heat of both kinds of reactors can also be quite destructive to the rocket’s structure. Engineers of nuclear rockets surround the reactor with heavy metals, such as lead, in order to contain radiation. Engineers also design extensive cooling systems—usually with circulated water or cold liquid hydrogen—to control the heat. The National Aeronautics and Space Administration (NASA) in the United States is investigating nuclear propulsion. This extremely powerful source of propulsion energy holds much promise for both piloted and unpiloted space exploration within and beyond the solar system.
Electric Rockets: Electric rocket engines use batteries, solar power, or some other energy source to accelerate and expel charged particles. These rocket engines have extremely high specific impulses, so they are very efficient, but they produce low thrusts. The thrusts that they produce are sufficient only to accelerate small objects, changing the object’s speed by a small amount in the vacuum of space. However, given enough time, these low thrusts can gradually accelerate objects to high speeds. This makes electric propulsion suitable only for travel in space. Because electric rockets are so efficient and produce small thrusts, however, they use very little fuel. Some electric rockets can provide thrust for years, making them ideal for deep-space missions. Satellites or other spacecraft that use electric rockets for propulsion must be first boosted into space by more powerful chemical rockets or launched from a spacecraft.
Plasma Engines: Plasma engines, another type of electric rocket engines, use a strong electric current to turn a normal gas into a plasma. Plasma is a state of matter in which many atoms have been ionized, or stripped of at least one of their electrons. This conversion turns the gas into a sea of ions, free electrons, and neutral atoms, with fairly equal numbers of positively charged ions and negatively charged electrons. The most common type of plasma rocket engines uses a cathode, or a positive electric terminal, that extends into a cylindrical chamber. One edge of the chamber is an anode, or negative electrical terminal. Injectors feed a neutral gas into the chamber. A strong electric current is put on the cathode. The current ionizes some of the gas (turning it into plasma) and uses the traveling ions to carry electricity between the cathode and the anode. This ionization sets up an electric field between the cathode and the anode, and a magnetic field around the cathode. These fields act to accelerate the charged particles out of the rocket nozzle. Collisions between the charged and neutral particles make the particles move faster and give the rocket even more thrust.
Russian-American Stationary Plasma Thrusters: In 1992 Russian and American aerospace engineers began developing electric rockets called Hall thrusters, or Stationary Plasma Thrusters (SPTs). Hall thrusters act much like the plasma thrusters described above, except Hall thrusters have an external magnetic field. The chamber of a Hall thruster is surrounded by a magnet. A cathode extends into the chamber, and an anode forms the outer edge of the chamber. A neutral gas is fed through the back of the chamber. The electric field created by the cathode and the anode turns the gas into plasma, and the electric and magnetic fields accelerate the plasma out of the rocket. Hall rockets are especially useful for keeping satellites in the correct orbit, or station keeping. The electricity for most Hall thrusters comes from solar cells. Such rockets last for years and are much lighter and less expensive than chemical thrusters. E electric rockets work well for station keeping, but the amount of thrust they produce must be greatly increased if these rockets are to be used for primary propulsion systems or for long distance voyages.
Photon Rocket: The photon rocket is another potential means of rocket propulsion. Theoretically, photon rockets move by emitting a beam of light with an exhaust velocity of the speed of light. Photons (packets of light) have no mass, but their speed is so great that they could theoretically produce a tiny amount of thrust. The thrust of a photon rocket would be so small that such rockets would be of use only outside of the gravitational influence of the solar system.
Private Researcher Aims for the Stars: The Russian Soyuz Launch vehicle could lift off with a tourist named Gregory Olsen on board this October. The U.S. millionaire has booked a holiday with the Russian space agency that should put him in space in October. But businessman, scientist and adventurer Gregory Olsen won't just be taking in the view; he says he plans to perform some experiments during his stay on the International Space Station (ISS).
Olsen had originally planned to take his trip of a lifetime in April, but Russian officials postponed it last summer after an undisclosed health problem was discovered. Olsen, who is about 60 years old, resumed training at Russia's Gagarin Cosmonaut Training Centre outside Moscow in May and has now signed a contract with the Russian agency.
The space traveler could join a Soyuz craft that is taking supplies to the ISS as early as October and would return after eight days in a different craft. Sources put the price of the trip, arranged through the specialist travel agent Space Adventures, based in Arlington, Virginia, at $20 million US dollars.
If successful, Olsen will become the world's third space tourist after fellow American Dennis Tito and South African Mark Shuttleworth. But Olsen prefers another description for himself: At a press conference last year he said he would rather be called a "private researcher," in recognition of the fact that he is "going to do a lot of science up there."
Olsen has a doctorate in materials science and started his career as a research scientist before founding two successful companies making electronic imaging equipment: EPITAXX and Sensors Unlimited, both based in Princeton. One of his experiments will be to grow semi-conducting crystals of the type used in his company's infrared imaging products, which include cameras used for night-vision equipment. Although Olsen was unavailable to comment in more detail on the nature of his experiments, experts speculate one may have something to do with semiconductors made of unusual materials.
Olsen's Experiment: The most commonly used semiconductor, found in computer chips, is silicon. But not all semiconductors are as easy to work with as silicon, notes Martin Liess of scientific instruments firm Perkin Elmer in Weisbaden, Germany. "Some other semiconductors are not so easy to grow into crystals and the effect of gravity can be limiting. It could be that Olsen has a semiconductor with certain advantages that is very sensitive to the effects of gravity," he says. Growing crystals of such semiconductors in space could be useful.
Olsen will also take one of his company's miniaturized infrared cameras aboard. He will use it for near-infrared astronomy, and to observe crops and the effects of pollution in the atmosphere from above. Olsen said: "l will spend my orbital time doing science".
Advertisement: David Alexander of Cambridge University's Institute of Astronomy explains that infrared astronomy is difficult from the Earth: "You don't get a perfect view of the sky because the atmosphere also emits infrared." But he expresses reservations about the true value of Olsen's contribution, pointing out that there are already at least two satellites with dedicated equipment to make infrared observations.
It remains unclear what Olsen's experiments will contribute to the world of scientific knowledge, but his mission should certainly add to the burgeoning industry of space tourism. In addition to orbital trips, Space Adventures says it is developing a program to take passengers on sub orbital flights starting in 2007.
Space New Discovery: A newly discovered giant planet has three suns wheeling overhead. The Jupiter sized world is 149 light years (about 879 trillion miles, just next door for astronomers) away from earthen a triple star system in the Northern constellation Cygnus, or the Swan.
Maciej Konacki, a planetary scientist at the California Institute of Technology in Pasadena, reported the sighting in this week's edition of the British Scientific Journal, Nature: "With three suns, the sky-view must be out of this world, literally, and figuratively."
About 150 extra solar planets have been discovered in the past ten years. About two hundred of them were found in binary star systems, consisting of two suns, but this is the first time a planet has been found in a luster of three. The masin star of the trio, named HD 1887533, is slightly larger than our sun. But it would look enormous to an observer on the planet, which whirls around its host, starts every 3-1/2 days at a distance of only 4 million miles. Our sun is 93 million miles from the Earth.
Konacki said: "Unlike Tatooine, life would be impossible on a new planet, since its temperature is estimated to be a scorching 1340 degrees Fahrenheit." The other two starts, each somewhat smaller than our sun, spin around each other at a distance of about 850 million miles, the distance from the sun to Saturn in our solar system.
A 32-foot wide Kech One telescope on the Mama Kea volcano in Hawaii makes the observation leading to a discovery. He detected Dr. Konacki’s tiny wobbles in the motion of HD 188753 as the gravity of its companions.
The opinion of most astronomers is that such planets form in huge disks of gas and dust around young stars. But at the gang of three stars would destroy most of the disk before the planet could form.
HD 188753 is a "conundrum" for theorists. Two German astronomers, Artie Hatzes and Gunther Wuchterl, wrote in a commentary piece in the Nature publication: "This planet should not exist," but it does.
Hubble, Edwin Powell
Hubble, Edwin Powell (1889–1953), was an American astronomer who made important contributions to the study of galaxies, the expansion of the universe, and the size of the universe. Hubble was the first to discover that fuzzy patches of light in the sky called spiral nebula were actually galaxies like Earth’s galaxy, the Milky Way. Hubble also found the first evidence for the expansion of the universe, and his work led to a much better understanding of the universe’s size.
Hubble was born in Marshfield, Missouri. He attended high school in Chicago, Illinois, and received his bachelor’s degree in mathematics and astronomy in 1910. He was awarded a Rhodes Scholarship to study at the University of Oxford in England, where he earned a law degree in 1912. He returned to the United States in 1913 and settled in Kentucky where his family had moved. From 1913 to 1914 Hubble practiced law and taught high school in Kentucky and Indiana. In 1914 he moved to Wisconsin to take a research post at the University of Chicago’s Yerkes Observatory.
In 1917 Hubble earned his Ph.D. degree in astronomy from the University of Chicago and received an invitation from American astronomer George Hale to work at Mount Wilson Observatory in California. Around the same time that Hubble received the invitation, the United States declared war on Germany, marking the beginning of official U.S. military involvement in World War I (1914-1918). Hubble volunteered to serve in the U.S. Army, rushing to finish his dissertation and reporting for duty just three days after passing his oral Ph.D. exam. He was sent to France at first and remained on active duty in Germany until 1919. He left the Army with the rank of major.
In 1919 Hubble finally accepted the offer from Mount Wilson Observatory, where the 100-in (2.5-m) Hooker telescope was located. The Hooker telescope was the largest telescope in the world until 1948. Hubble worked at Mount Wilson for the rest of his career, and it was there that he carried out his most important work. His research was interrupted by the outbreak of World War II (1939-1945); during the war he served as a ballistics expert for the U.S. Department of War.
While Hubble was working at the Yerkes Observatory, he made a careful study of cloudy patches in the sky called nebulas. Now, astronomers apply the term nebula to clouds of dust and gas within galaxies. At the time that Hubble began studying nebulas, astronomers had not been able to differentiate between nebulas and distant galaxies, which also appear as cloudy patches in the sky.
Hubble was especially interested in two nebulas called the Large Magellanic Cloud and the Small Magellanic Cloud (see Magellanic Clouds). In 1912 American astronomer Henrietta Leavitt had used the brightness of a certain type of star in the Magellanic Clouds to measure their distance from Earth. She used Cepheid stars, yellow stars that vary regularly in brightness. The longer the time a Cepheid star takes to go through a complete cycle, the higher its average brightness, or average absolute magnitude. By comparing the brightness of the star as seen from Earth with the star’s actual brightness (estimated from the length of the star’s cycle), Leavitt could determine the distance from Earth to the nebula. She and other scientists showed that the Magellanic Clouds were beyond the boundaries of the Milky Way Galaxy.
After World War I, with the Hooker telescope at his disposal, Hubble was able to make significant advances in his studies of nebulas. He focused on nebulas thought to be outside of the Milky Way, searching for Cepheid stars within them. In 1923 he discovered a Cepheid star in the Andromeda nebula, now known as the Great Andromeda Spiral Galaxy. Within a year he had detected 12 Cepheid stars within the Andromeda Galaxy. Using these variable stars, he determined that the Andromeda nebula was about 900,000 light-years away from Earth. (A light-year is the distance light can travel in one year, a measurement equal to 9.46 trillion km or 5.88 trillion mi). The diameter of the Milky Way is about 100,000 light-years, so Hubble’s measurements showed that the Andromeda nebula was far outside the boundaries of Earth’s galaxy.
Hubble discovered many other nebulas that contained stars and were located outside of the Milky Way. He found that they contained objects similar to those within the Milky Way Galaxy. These objects included round, compact groups of stars called globular clusters and stars called novas that flare suddenly in brightness. In 1924 he finally proposed that these nebulas were in fact other galaxies like our own, a theory that became known as the island universe. From 1925 he studied the structures of these external galaxies and classified them according to their shape and composition into regular and irregular forms. The regular galaxies, 97 percent of the total, had elliptical or spiral shapes. Hubble further divided the spiral galaxies into normal spiral galaxies and barred spiral galaxies.
Normal spiral galaxies have arms that come out from a central, circular core and spiral around the core and each other. The arms of barred spiral galaxies come out from an elongated, bar-shaped nucleus. There are no distinct boundaries between the types of galaxies—some galaxies have the characteristics of both spiral and elliptical galaxies, and some spiral galaxies could be classified as either normal or barred. Irregular galaxies—galaxies that seem to have no regular shape or internal structure—made up only 3 percent of the galaxies that Hubble found.
Hubble began to measure the distance from Earth to the galaxies that he classified. He used information provided by Cepheid stars within the galaxies to measure their distance from Earth. He compared these distance measurements to measurements of the galaxies’ movement with respect to Earth. Several astronomers, in particular American astronomer Vesto Slipher, studied the speed of the galaxies in the 1910s and 1920s, before Hubble classified them as galaxies. The astronomers measured the galaxies’ speed by measuring the redshift of the galaxy. Redshift results from the radiation that an object emits. This radiation will appear to shift in wavelength if the object is moving with respect to the observer. If the object is moving away from the observer, each wave will leave from slightly farther away than the wave before it did, increasing the distance between the waves. The wavelength of an object’s radiation will seem shorter if the object is moving toward the observer. This is called the Doppler effect. When the radiation emitted by the object is visible light, a lengthening in wavelength corresponds to a reddening of light. Therefore, the light of astronomical objects moving away from the observer is said to be red-shifted. Slipher and the other astronomers found that all of the galaxies were moving away from Earth. Hubble also did his own redshift measurements.
In 1929 Hubble compared the distances of the galaxies to the speed at which they were moving away from Earth, and he found a direct and very consistent correlation: The farther a galaxy was from Earth, the faster it was receding. This relationship was so consistent throughout the 46 galaxies that Hubble initially studied, as well as in virtually all of the galaxies studied later by Hubble and other scientists, that it is known as Hubble’s Law. Hubble concluded that the relationship between velocity and distance must mean that the universe is expanding. In 1927 Belgian scientist Georges Lemaître had developed a model of the universe that incorporated the general theory of relativity of German American physicist Albert Einstein. Lemaître’s model showed an expanding universe, but Hubble’s measurements were the first real evidence of this expansion.
The relationship of the velocity of galaxies to their distance is called the Hubble constant. If astronomers knew the precise value of Hubble’s constant, they could determine both the age of the universe and the radius of the observable universe. Many teams of scientists have attempted to measure the value since Hubble proposed his theory. In 1999 a group of scientists measured Hubble’s constant to be 70 kilometers per second-megaparsec, with an uncertainty of 10 percent—the most precise measurement to date. This result means that a galaxy appears to be moving 260,000 km/h (160,000 mph) faster for every 3.3 million light-years that it is away from Earth. The universe is infinitely large, but if objects really do move faster as they move farther from the center of the universe, at some distance objects will be moving at the speed of light. That distance would be the limit to the observable universe, because light from an object moving at the speed of light could never reach Earth. The radius of the observable universe is called the Hubble radius.
During the 1930s, Hubble studied the distribution of galaxies. His results showed that galaxies should be scattered evenly across the sky. He explained that there seemed to be fewer galaxies in the area of the sky that corresponds to the plane of the Milky Way because large amounts of dust block light from external galaxies.
Hubble was an active researcher until his death. He was involved in building the 200-in (508-cm) Hale telescope at the Mount Palomar Observatory, also in southern California. The Hale telescope was the largest telescope in the world from when it went into operation in 1948 until the Keck telescope at the Mauna Kea Observatory in Hawaii was completed in 1990. The Hubble Space Telescope (HST), a powerful telescope launched in 1990 and carried aboard a satellite in orbit around Earth, was named after Hubble and has helped scientists make many important observations.
Edwin Powell Hubble
November 20, 1889
September 28, 1953
Place of Birth
Recognizing that galaxies other than our own exist, and finding evidence that the universe is expanding
1914-17 Worked as a researcher at the University of Chicago's Yerkes Observatory in Wisconsin
1919 Began work as an astronomer at the Mount Wilson Observatory in California, and retained the position for his entire career
1923 Discovered that the Andromeda nebula is a galaxy (now called the Great Andromeda Spiral Galaxy) containing stars of its own
1929 Provided evidence that the universe is expanding, by calculating that the farther a galaxy is from the earth, the faster it is receding
1948 Accepted a mostly honorary position as an astronomer at the Mount Palomar Observatory, which he helped found
Did You Know
Prior to Hubble's discovery, distant galaxies were thought to be gas nebulas within the Milky Way.
Hubble earned an advanced degree in law and worked as a lawyer before beginning a career in astronomy.
The Hubble Space Telescope is named in Edwin Hubble's honor.
Redshift/Hubble’s Law: Photo Researchers, Inc./Science Photo Library Redshifts of galaxies allow astronomers to measure the distance from Earth to the galaxies. Knowing the distances to galaxies gives astronomers an idea of the way the universe is expanding and provides clues to the origin, evolution, and future of the universe. The relationship between the redshift (and therefore velocity) and distance of a galaxy is called Hubble’s law.
Hubble’s Law/Measurement: The relationship of the velocity of galaxies to their distance is called the Hubble constant. If astronomers knew the precise value of Hubble’s constant, they could determine both the age of the universe and the radius of the observable universe. Many teams of scientists have attempted to measure the value since Hubble proposed his theory. In 1999 a group of scientists measured Hubble’s constant to be 70 kilometers per second-megaparsec, with an uncertainty of 10 percent—the most precise measurement to date. This result means that a galaxy appears to be moving 260,000 km/h (160,000 mph) faster for every 3.3 million light-years that it is away from Earth. The universe is infinitely large, but if objects really do move faster as they move farther from the center of the universe, at some distance objects will be moving at the speed of light. That distance would be the limited to the observable universe, because light from an object moving at the speed of light could never reach Earth. The radius of the observable universe is called the Hubble radius.
Hubble’s Constant: Other astronomers used mainly ground-based telescopes to try to determine Hubble’s constant. The American astronomer Alan Sandage and the Swiss astronomer Gustav Tammann have used a variety of methods to come up with an expansion estimate of 55 km/sec/megaparsec (about 34 mi/sec/megaparsec). A megaparsec is 1 million parsecs, and a parsec is about 3.26 light years (a light year is the distance that light could travel in a year—9.5 × 1012 km, or 5.9 × 1012 mi). So far, the cosmologists using the Hubble Space Telescope have found a value of about 70 km/sec/megaparsec (44 mi/sec/megaparsec) for the expansion rate of the universe. These expansion rates correspond to a universe between 8 billion and 13 billion years old.
Equation of the Law: The universe’s density, expansion rate, and age are all related. The density of the universe determines how much the gravitational force will slow the expansion rate. The rate of expansion depends on the age and density of the universe. If cosmologists measure the rate of expansion by examining galactic redshifts and estimate the density of the universe, they can calculate an estimate of the universe’s age. Cosmologists calculate the expansion rate of the universe by finding the relationship between the distance of an object from Earth and the rate at which it is moving away from Earth. This relationship is represented by Hubble’s constant, H in the formula v = H × d, where v is velocity (or the speed of the object) and d is the distance between the object and Earth. If Hubble's constant is relatively large, the universe is expanding relatively rapidly. A universe that is rapidly expanding would be larger than a universe of the same age with a smaller value of Hubble's constant.
Expansion of the Universe: In the late 1920s American astronomer Edwin Hubble discovered that all but the nearest galaxies to us are receding, or moving away from us. Further, he found that the farther away from Earth a galaxy is, the faster it is receding. He made his discovery by taking spectra of galaxies and measuring the amount by which the wavelengths of spectral lines were shifted. He measured distance in a separate way, usually from studies of Cepheid variable stars. Hubble discovered that essentially all the spectra of all the galaxies were shifted toward the red, or had redshifts. The redshifts of galaxies increased with increasing distance from Earth. After Hubble’s work, other astronomers made the connection between redshift and velocity, showing that the farther a galaxy is from Earth, the faster it moves away from Earth. This idea is called Hubble’s law and is the basis for the belief that the universe is fairly uniformly expanding.
Other uniformly expanding three-dimensional objects, such as a rising cake with raisins in the batter, also demonstrate the consequence that the more distant objects (such as the other raisins with respect to any given raisin) appear to recede more rapidly than nearer ones. This consequence is the result of the increased amount of material expanding between these more distant objects. Hubble's law states that there is a straight-line, or linear, relationship between the speed at which an object is moving away from Earth and the distance between the object and Earth. The speed at which an object is moving away from Earth is called the object’s velocity of recession. Hubble’s law indicates that as velocity of recession increases, distance increases by the same proportion.
Using this law, astronomers can calculate the distance to the most distant galaxies, given only measurements of their velocities calculated by observing how much their light is shifted. Astronomers can accurately measure the redshifts of objects so distant that the distance between Earth and the objects cannot be measured by other means. The constant of proportionality that relates velocity to distance in Hubble's law is called Hubble's constant, or H. Hubble's law is often written v=Hd, or velocity equals Hubble's constant multiplied by distance. Thus determining Hubble's constant will give the speed of the universe's expansion. The inverse of Hubble’s constant, or 1/H, corrected for the effect of gravitation, theoretically provides the age of the universe. The value of Hubble’s constant probably falls between 55 and 75 kilometers per second per megaparsec. A megaparsec is one million parsecs and a parsec is 3.26 light-years.
Hubble Space Telescope: The Hubble Space Telescope studied Cepheid variables in distant galaxies to get an accurate measurement of the distance between the stars and Earth to refine the value of Hubble’s constant. The value they found is 72 km per second per megaparsec, with an uncertainty of only 10 percent. The actual age of the universe depends not only on Hubble's constant but also on how much the gravitational pull of the mass in the universe slows the universe’s expansion. Some data from studies that use the brightness of distant supernovas to assess distance even seem to indicate that the universe's expansion may be speeding up instead of slowing down. Astronomers were actively investigating these topics at the end of the 20th century.
Free of the distorting effects of the earth’s atmosphere, the Hubble Space Telescope has an unprecedented view of distant galaxies. Placed in orbit in 1990, scientists discovered soon after the telescope became operational that its 240-cm (94.5-in) primary mirror was flawed. However, a repair mission completed by space shuttle astronauts in December 1993 successfully installed corrective optics that compensated for the flawed mirror.
Einstein’s Biggest Blunder: When Einstein expanded his general relativity to include "cosmological considerations," Einstein found to his dismay that his system of equations did "not allow the hypothesis of a spatially closed-ness of the world.” How did Einstein cure this flaw? By something he had done very rarely: making an ad hoc addition, purely for convenience: "We can add, on the left side of the field equation a – for the time being – unknown universal constant, - ['lambda']." In fact, it seems that not much harm is done thereby. It does not change the covariance; it still corresponds with the observation of motions in the solar system ("as long as is small"), and so forth. Moreover, the proposed new universal constant also determines the average density of the universe with which it can remain in equilibrium, and provides the radius and volume of a presumed spherical universe. Altogether a beautiful, immutable universe – one an immutable God could be identified with.
But in 1922, Alexander Friedmann showed that the equations of general relativity did allow expansion or contraction. And in 1929 Edwin Hubble found by astronomical observations the fact that the universe does expand. Thus Einstein – at least according to the physicist George Gamow – remarked that "inserting was the biggest blunder of my life." When the special relativity theory was created, it did not include the cosmological constant of the Universe expansion. Dr. Einstein acceded to Dr. Hubble observation results to exclude the cosmological constant back into the relativity theory to compensate for the expansion of the Universe. In fact, Dr. Einstein went to Dr. Hubble’s office and apologized for this blunder.
Summary: In the early 1800s, British inventor William Congreve noted reports of Indian rockets employed against British forces. Despite their stabilizing poles, Congreve rockets were often inaccurate. In the 1880s, Russian teacher Konstantin Tsiolkovsky theorized that rockets might be useful for space flight. In World War I, 1918 rockets were balloon weapons. After World War I (1914-1918), rockets were used only as signals and simple balloon weapons. After World War I, the Treaty of Versailles prohibited Germany from building and using heavy artillery.
In spite of the war time conditions, and many ups and downs, the work progressed rather satisfactorily, and at the end of World War II a new potent weapon had been developed, the ballistic missile known by its builders as the A. The German rocket troops were trained to erect 3 missiles at a time, and to fuel, align, and launch them in a matter of 2 hours. About 1000 of these missiles were fired at the cities of London and Norwich, while about 2000 more were fired at targets on the European continent. The British launched 3 V 2's from the Cuxhaven area. They used captured German soldiers who had served in missile firing units. In the 1920s and 1930s space flight and rocketry clubs sprang up in Europe (especially Germany) and the United States and undertook their own experiments.
In 1932 the German army hired Wernher von Braun, a bright young member of the VfR, for its own secret rocket program. United States troops bring material and personnel, including von Braun, back to the United States. About 500 specialists were brought here under "Operation Paperclip" for this purpose. The story of 118 of these rocket scientists after arrival in this country is recorded in history. A quote from Dr. Von Braun: " In this achievement will be discussed in the perspective of its far-reaching importance for the future of mankind.” Dr. Von Braun was assigned as the Director, Marshall Space Center and upon his death the Von Braun Civic Center was named after him to honor his accomplishments. In 2004, a Von Braun Complex was built at Redstone Arsenal to honor him on his birthday.
Hubble, Edwin Powell, was an American astronomer who made important contributions to the study of galaxies, the expansion of the universe, and the size of the universe. Hubble was the first to discover that fuzzy patches of light in the sky called spiral nebula were actually galaxies like Earth’s galaxy, the Milky Way. Hubble also found the first evidence for the expansion of the universe, and his work led to a much better understanding of the universe’s size.
The future of rocketry will now include President Bush’s vision for NASA’s space exploration, to re-visit the moon by humans and to go beyond the moon with a planned human landing on Mars.
The Speech that Started the Moon Race, Web Site: http://www.cs.umb.edu/jfklibrary/
The Genesis of the Saturn Program, Web Site:
The Goddard 1941 Rocket Concept, Web site: http://www.nasm.si.edu/
The Russian Lunar Concept, Web Site: http://www.astronautix.com/
Liberty Bell, Web Site: http://www.thespaceplace.com/history/mercury/mercury04.html
Summary: Soviet Claiming Lead In Science/New Announcements Noted on Ballistic Missile and Rocket for Research-Web Site: http://www.nytimes.com/partners/aol/special/sputnik/
Yuri Gagarin’s Trip Around the Earth, Web Site:http://www.nytimes.com/partners/aol/special/sputnik/
Arno Breker: His Art and Life, by B. John Zavrel
Collected Writings of Arno Breker, by Arno Breker
Living with the Himalayan Masters, by Swami Rama
Alexander the Great, by Robin Lane Fox
Primer for Those Who Would Govern, by Hermann Oberth
From Pemenenemunde to the Moon By Konrad K. Dannenberg
Space Explorations Contributed By: Frank H. Winter, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation
Von Braun, Wernher, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation
Notable Inventions and Discoveries, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation.
1957 Missies and Rockets Chronology, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation.
Goddard, Robert Hutchings, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation.
Simonite, Tom, 'Private Researcher' Aims for the Stars.
Space News Discovery, Huntsville Times, 14 July 2005.
Quick Facts of Edwin Powell Hubble, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.
Edwin Powell Hubble, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.
Hubble’s Constant, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.
Hubble space Telescope, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.
Einstein Relativity Theory, Microsoft ® Encarta ® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.