EVOLUTION OF U.S. EXPENDABLE LAUNCH VEHICLES

Beginnings

Robert H. Goddard was a Professor of Physics at Clark University in Worcester, Massachusetts, a post he held for 26 years from 1919 until his death in 1945.
During these years, Goddard performed a classic series of experiments in which he, almost single-handedly, worked out the basic elements of liquid-fueled rocket technology. Goddard was interested in using rockets for space flight from the very beginning. He felt that for this purpose, liquid fuels, specifically, kerosene or gasoline and liquid oxygen would be best. This fuel would be more efficient, that is, it has a higher specific impulse, and it has the advantage that by closing and opening valves, the rocket engine could be stopped and restarted. This latter point was especially important because it gave liquid-fueled rockets a truly decisive advantage over those that operated with solid fuel. In solid-fueled rockets, once the motor is started, the rocket is committed, and the engine cannot be turned off.
In 1919, Goddard published a paper titled ”A Method for Reaching Extreme Altitudes” in the Journal of the Smithsonian Institution in which he outlined his plans (1). These came to fruition on 16 March 1926, when a liquid-fueled rocket built by Goddard performed the first successful liftoff and flight and reached an altitude of about 80 feet (Fig. 1). This experiment was carried out in an open field on a farm near Auburn, Massachusetts. Goddard realized that this was not the best place for these experiments. He took advantage of an offer from Daniel Guggenheim, the heir to a huge mining fortune and an enthusiastic supporter of American aviation, to support the continuation of his experiments and to set him up on a large ranch near Roswell, New Mexico. It was here that Goddard built and flew the first gyroscopically stabilized liquid-fueled rocket on 31 May 1935; it reached an altitude of more that 7000 feet.
Goddard’s remarkable success was unfortunately not pursued. Because of the depression, Guggenheim could no longer support Goddard’s work, and eventually, the work at the Roswell ranch was abandoned. The U.S. military showed no interest in Goddard’s work. When the Second World War started, the military did initiate a vigorous effort to develop solid-fueled rockets for use as airborne and ground-based weapons, in which Goddard participated. Goddard’s untimely death in 1945 precluded his participation in the rapid development of large liquid-fueled rockets in the United States following World War II.
While all of this was happening in the United States, a group of Germans was also interested in developing liquid-fueled rockets for the same reasons that motivated Goddard. The intellectual leader of this group was Professor Hermann Oberth, a Romanian-German, who wrote the first topic on planetary exploration that was published in 1923, ”Die Rakete zu den Planetenraumen” (2). He advocated using rocket propulsion. In this topic, he worked out the necessary mathematics to accomplish this objective and also elaborated on the infrastructure that would have to be built. (Both Goddard and Oberth were unaware of the work of Konstantin E. Tsiolkovski, a Russian mathematics professor who had worked out the rocket equation and had speculated on the use of rockets for space travel 20 years before Goddard and Oberth wrote about their work.) Oberth’s topic attracted the attention of a small group of German scientists and engineers who had a great interest in space travel and rockets. Along with Oberth, these included Rudolf Nebel, Klaus Riedel, Willy Ley, and Max Valier. On 5 July 1927, these people and a few others founded the “Verein fur Raumschiffarht,” the ”Society for Space Travel.” By 1929, the Society had almost 900 members, one was a 17-year-old high school senior named Wernher von Braun. Von Braun was a member of a prominent and affluent Prussian family. His father served as Minister of Agriculture and also as Minister of Education under the democratic German Weimar Republic.
Robert Goddard with the liquid-fueled rocket that first flew on March 16 1926.This figure is available in full color at http://www. mrw.interscience.wiley.com/esst.
Figure 1. Robert Goddard with the liquid-fueled rocket that first flew on March 16 1926.
The Society acquired a small tract of land a few miles north of Berlin that was a German army ammunition storage depot and could be used for rocket flight experiments. The area was named the ”Rocket Flight Area” (Raketenflugplatz, in German), and the Society began to conduct flight experiments. The technical leaders of the Society were convinced—as was Goddard—that only liquid-fueled rockets were practical for space travel. They knew about Goddard’s work, and they began to build and test liquid-fueled rockets. The first test models were called ”Mirak” which stood for the German ”Minimum Rakete.” They were small test rockets designed only for static tests. They also built flight models called ”Repulsors” which looked very much like Goddard’s first rocket. One of these flew for the first time on 10 May 1931 and reached an altitude of 18 meters. The rockets following this event were somewhat more sophisticated, but none reached the technical complexity of Goddard’s gyrostabilized rocket.
Both Oberth and Nebel had talked and written about military applications of rockets. There was interest in rockets in Germany because the Versailles Treaty that ended Word War I contained provisions that seriously limited German artillery development. In 1929, the Army Ordnance Department established a small group to study the possible military applications of rockets. A year later, a young German artillery captain, Walter Dornberger, was named to head this group. Dornberger was aware of the experiments conducted by Oberth, Nebel, and the others at the Raketenflugplatz. He decided to help the group by providing modest financial support. He also quickly came to the conclusion that the Raketenflugplatz site was not adequate, and he offered the facilities of the German artillery range at Kummersdorf for the rocket experiments. These moves accelerated technical progress, but they also weakened the Society because several of the people who worked on the Society’s rockets joined Dornberger’s group. Wernher von Braun, one of them, started to work at Kummersdorf on 1 October, 1932.
When Adolf Hitler and the Nazi party came to power in January 1933, things changed drastically. The civilian organizations interested in rocketry disappeared, and the work on military rockets was substantially accelerated. During the mid-1930s, the Germans developed a well-organized, systematic research program on liquid-fueled rockets. The first of these rockets, called the A-2, was successfully launched in December 1934 and reached an altitude of 2000 meters, about 6000 feet. It was not as sophisticated as Goddard’s gyrostabilized rocket that was launched a few months later, but the A-2 did work. Wernher von Braun had acquired a Ph.D. and was the technical director of the Kummersdorf enterprise reporting directly to Dornberger. In any event, the Germans had now roughly caught up to where Goddard was when he was forced to quit.
By the mid-1930s, the Germans had made enough progress that they decided to develop a test site which would make it possible for them to test large rocket vehicles. They chose an isolated region on the north German Baltic coast where the River Peene reached the sea. The place was called Peenemunde and by 1939, test operations were started there. The A-2 was followed by the A-3 and the A-4, the latter was successfully flown on 3 October, 1942, almost a decade to the day that von Braun joined Dornberger’s unit. The A-4 was the prototype of the V-2, the first long-range weapon based on rocket technology (Fig. 2). It could throw a payload of 1 metric ton about 250 miles. The rocket engine of the A-4 developed a thrust of 60,000 pounds. The rocket burned ethanol as a fuel and used liquid oxygen as an oxidizer. Due to the success of the A-4 launch and the loss of the Battle of Britain in 1941, Hitler decided, on 7 July 1943, to put the development and production of the V-2 missiles at the highest level of priority.
Because of good air reconnaissance and brilliant photo interpretation, the British were aware that new and dangerous weapons were being developed and tested at Peenemunde. They mounted a massive air raid on the test site, which was partially successful. The Germans realized that they would have to disperse their test and production facilities because more allied air raids attacking the Peenemunde complex were inevitable. The Germans built a massive underground facility in central Germany called the “Mittlewerk” for producing V-2 missiles. They also built a test site in Poland which was out of range of long range bombers based in England. A little more than 6,250 V-2s were produced. About 3700 were fired at targets in Great Britain and on the continent, of which about 700 failed! About 2000 were in storage at the end of the war, 300 were expended in tests, and 250 were taken to the United States at the end of the war. Although the outcome of the war was not influenced by the use of large numbers of V-2 rockets, the creation of the V-2 missile and its successful operation was still a technical achievement of the first rank. It has been said that if the Manhattan Project to produce nuclear weapons was the technical ”tour de force” of the United States during World War II, then the development of the V-2 played the same role in Germany.
A V-2 missile taking off from the launch pad. This figure is available in full color at http://www.mrw.interscience. wiley.com/esst.
Figure 2. A V-2 missile taking off from the launch pad.


The End of World War II

The V-2 rocket team that Wernher von Braun organized at Peenemunde was dispersed at the end of World War II. Wernher von Braun and most of the 100 or so senior technical people were housed in the small mountain village of Oberjoch on the Austrian-German border. They wanted to surrender to the U.S. Army, which had some units in the neighborhood, but they did not know how to make contact. At the same time, in 1945, the U.S. Army realized that it would be important to capture the Germans who had the knowledge to develop and build long-range missiles. An operation dubbed ”Paperclip” was initiated to locate and detain the people who had this expertise. It was headed by U.S. Army Colonel Holger N. Toftoy. Eventually, the von Braun group surrendered to a U.S. Army unit and was taken into custody. Other veterans of the V-2 program wound up as prisoners of the Soviets. There were a few who actually volunteered to go to work for the Soviets.
Wernher von Braun, Walter Dornberger, and other leaders of the V-2 program arrived at Newcastle Air Base in Wilmington, Delaware on 19 September 1945. They were now under contract to the U.S. Army and were going to work on missile development. They were taken to Fort Bliss near El Paso, Texas, the U.S. Army’s Center for Anti Aircraft Artillery. Fort Bliss is located at the southern end of the White Sands Missile Test Range in New Mexico. It would be the job of von Braun and his colleagues to launch some of the V-2s brought over from Germany, to perform research, and to train Americans in the art and science of rocketry. In doing so, a large number of V-2 rockets was used; some were modified to measure the upper atmosphere and to photograph Earth, the Sun, and other astronomical objects. All of these activities were very important to the future of U.S. ballistic missile and space flight programs (3).
At the same time that the Germans were working for the U.S. Army, a group at Douglas Aircraft Company in Santa Monica, California, published a far-reaching document in 1946. The group was led by some outstanding scientists and engineers including Francis Clauser, David Griggs, and Louis Ridenour among others; they later left Douglas to form the RAND Corporation. The title of their work was ”Preliminary Design of an Earth-Orbiting Spaceship” (4). The group anticipated that large rockets, based on extensions of the V-2 designs, would be developed both by the United States and the Soviet Union to carry nuclear weapons at ranges from 8,000 to 10,000 miles. Such rockets could be modified to place significant payloads into Earth orbit and to other places in the solar system. Thus, the means to realize the early ideas of Tsiolkovski, God-dard, and Oberth would soon be available, and therefore, it was time to make some detailed calculations about spaceflight. The remarkable thing about
”Preliminary Design of an Earth-Orbiting Spaceship” is that it was a serious engineering study—about 250 pages long—that predicted nearly all of what has happened in spaceflight since 1946. Weather observations, intelligence gathering, communications, and other things now being done by Earth orbiting vehicles were treated. In addition, there were estimates of what it would take to put people in space. Thus, the stage was set for humanity’s first steps into space.

The Development of U.S. Space Launch Vehicles

As the authors of the 1946 report anticipated, the United States embarked on a vigorous program to develop and then build large liquid-fueled rockets for military reasons. Two military services, the U.S. Army and the U.S. Air Force, were charged with the responsibility for creating the missiles that would carry nuclear weapons. In 1950, the Army reached the decision that the Germans had finished their work at White Sands and that they would be moved to the Redstone Arsenal near Huntsville, Alabama, to initiate the development of new ballistic missiles.
The U.S. Army Rocket Development Program. Wernher von Braun, the leader of the German rocket engineers, arrived in Huntsville on 15 April 1950. It is safe to say that the town has not been the same since. The Army’s attitude toward long-range rockets was that they were an extension of artillery. Thus, in the beginning, the objective was to develop a second-generation V-2 missile. The military requirements, written in early 1951, called for a rocket that had a range of about 200 miles but had a substantially increased payload capability to carry the nuclear weapons then being developed. The rocket was named the Redstone and there were some important differences between the Redstone and the V-2. One was that the payload was designed to separate from the rocket, so that the entire vehicle would not have to reenter the atmosphere. This made it possible to build the rocket from aluminum rather than steel, as was the case for the V-2. The Redstone’s engine had a thrust of 80,000 lb, rather than the 60,000 lb of the V-2. The first Redstone was launched on 20 August 1953, from the new launch site on the east coast of central Florida at Cape Canaveral. The flight was a failure, but subsequent flights proved that the Redstone design was sound. The Chrysler Corporation was given the contract to produce the Redstone in quantity.
Wernher von Braun and his German colleagues never lost their interest in spaceflight. In 1952, von Braun, along with Fred Whipple, the Harvard astronomer, and Joseph Kaplan, a distinguished atmospheric scientist at UCLA, were the leading authors of a series of articles published between 1952 and 1954 in Collier’s magazine entitled ”Man Will Conquer Space Soon”(5). There were articles about what became the space shuttle, space stations, and journeys to the Moon and the planets. The articles attracted considerable attention and encouraged von Braun and his colleagues to press for an upgrade of the Redstone so that a man-made satellite could be put into Earth orbit. On 15 September 1954, von Braun submitted a proposal to Colonel Toftoy—who by now was chief of the rocket branch at the Redstone Arsenal—to upgrade a Redstone rocket with suitable upper stages so that a small satellite could be put into Earth orbit. This was technically feasible, but the proposal was rejected for political reasons.
The Eisenhower Administration was anxious to keep the effort to create an Earth orbiting satellite as a civilian project. The scientific community had designated 1957 as the first ”International Geophysical Year,” and orbiting a satellite would be part of the program of research. The satellite would be launched by a Vanguard rocket that would be developed by the Martin Company for this purpose. Even though people from the U.S. Naval Research Laboratory were involved in developing the Vanguard, the program would be managed by a civilian organization.
In spite of this edict, the Redstone was upgraded. The first of these modifications was called the Jupiter A, which was used as a rocket test vehicle. The second, Jupiter C, which had three solid-fueled upper stages, was used in developing heat-resistant materials for ballistic reentry vehicles that would carry nuclear warheads. The first Jupiter C was launched on 20 September 1956 carrying a one-third scale warhead. It reached an altitude of 682 miles and flew a distance of 3,335 miles, a record that stood until the first intercontinental missiles were tested. It was only a short step from the Jupiter C to a rocket that could orbit a satellite. Von Braun secured permission to continue studies to achieve this objective in spite of the fact that his Army superiors were under strict orders not to develop orbital vehicles. Finally, an extended version of the Redstone was used to develop the Jupiter MRBM (medium range ballistic missile) that had a total takeoff thrust of 150,000 lbs.
The Soviets were not bound by the rules imposed on the U.S. Army’s group at Huntsville. On 4 October 1957, using a military rocket, the Soviets placed the first man-made object, Sputnik I, into an orbit around Earth. (How this was done is described in an article elsewhere in this topic.) The Soviet spacecraft created a sensation and caused great consternation in the United States. To add insult to injury, the Soviets launched a much larger satellite, Sputnik II that carried a dog named ”Laika” and weighed 1100 lbs, a month later on 3 November. The final embarrassment came on 6 December 1957 when the first Vanguard was launched and then fell back to Earth two seconds later. At this point, the decision was finally made to ask von Braun’s group to use the Jupiter C to orbit an American satellite. The Huntsville group recruited William Pickering, the Director of the Jet Propulsion Laboratory at the California Institute of Technology, then funded by the Army, to build a fourth stage for the Jupiter C. Professor James A. Van Allen was recruited to build a payload for Pickering’s fourth stage so that if it went into Earth orbit, some scientific results would be obtained. Von Braun’s team estimated that they could put a satellite into Earth orbit within sixty days.
The modified Jupiter C, now called the Juno I, blasted off from Cape Canaveral on 31 January 1958 and put Explorer I, the first American satellite into Earth orbit. It was launched 56 days after the Huntsville group was given the job to go ahead. Professor Van Allen’s scientific payload was the first to measure the radiation fields above the Earth’s atmosphere. This led to the discovery of permanent ”belts” of radiation surrounding the Earth, now called the ”Van Allen Belts.” Juno I was used to launch two more satellites, Explorers 3 and 4, and was then replaced by further upgrades of the Redstone, Juno II, and the Mercury Redstone. Juno II, was used to launch a series of ”Pioneer” satellites that explored the newly discovered radiation belts. Finally, the Mercury-Redstone was
used to launch Alan Shepard on a suborbital flight on 5 May 1961 followed by an identical flight by Gus Grissom on 21 July. Both of these flights were carried out after Yuri Gagarin achieved the first orbital flight by a human being on 12 April 1961. (See the article First Flight of Man in Space by Klimuk and Vorobyev on Gagarin’s flight elsewhere in this topic.) Thus, the United States was still substantially behind the Soviet Union in spaceflight technology.
The flights of Shepard and Grissom were the last to use the Redstone as the core of the launch vehicle. Thus, the period of playing catchup with the Soviet Union would not be over until launch vehicles more powerful than the Redstone were available.
The U.S. Air Force Rocket Development Program. The U.S. Air Force, unlike the Army, was given a broader mission in rocket development. In addition to short- and intermediate-range missiles, the Air Force would also develop rockets with intercontinental ranges. Another difference between the Army and the Air Force rocket programs was that the leaders ofthe Air Force program were Americans rather than people from Germany who had been captured at the end of the Second World War. Although a number of members of the German rocket team went to work for contractors who built the rockets, none of them went to work in the Air Force management organization, the Western Development Division in Los Angeles. Walter Dornberger, who had risen to the rank of Major General in the German Army before the end of World War II, went to work at Bell Aircraft, and he was soon joined by Krafft Ehricke. Ehricke later joined Convair to work on the Air Force Atlas rocket development. Dr.  Friedrich also joined Convair to work on the Atlas. Dr. Adolf K. Thiel joined Ramo/Woolridge, later TRW, and Dr. Martin Schilling became a vice president of Raytheon Corporation.
Wernher von Braun and the rocket team that remained with him in Huntsville eventually were transferred to NASA when part of the Redstone Arsenal was turned over to the new civilian space agency in 1960. The new organization was called the George C. Marshall Space Flight Center. There they developed the Saturn V launch vehicle that eventually put humans on the Moon in 1969. (See the article on U.S. Manned Spaceflight: Mercury to the Shuttle elsewhere in this topic.)
The rocket development program that the Air Force eventually adopted grew out of a careful study conducted by the Air Force Strategic Missiles Evaluation Committee. This group was headed by Professor John von Neumann of Princeton University who played a major role in the development of nuclear weapons during World War II. Von Neumann first broached the idea of putting nuclear warheads on top of large rockets, which he called ”intercontinental artillery.” In 1954, the Missile Evaluation Committee urged the development of relatively small intercontinental ballistic missiles (ICBMs) that were able to carry the advanced ”second-generation” nuclear and thermonuclear weapons then being developed. Von Neumann’s detailed familiarity with nuclear weapons development influenced the Evaluation Committee to make this judgment. He knew that nuclear explosives much smaller and more efficient than those used at Hiroshima and Nagasaki were being developed, and the rockets, therefore, would be tailored to carry the new weapons. Ironically, this was the reason, among others, that the Soviets gained a significant advantage over the United States during the first years of orbital space operations. Their nuclear weapon technology was well behind that of the U.S. Accordingly, they had to develop larger and more powerful rockets to carry their heavier nuclear weapons.
To develop the new ICBMs, the Air Force established the Western Development Division at Los Angeles. This move was in accord with the recommendation of the von Neumann Committee to create an organization that would have full authority and responsibility for ICBM development. The Western Development Division would have the technical support of a new organization, the Aerospace Corporation, which was a nonprofit organization created by the transfer to the Air Force of the Space Technology Laboratory of the Ramo-Woolridge Corporation. The first commander of the Western Development Division was a brilliant young Air Force Brigadier General, Bernard A. Schriever. He later achieved four-star rank as the leader of the U.S. Air Force Systems Command. The basic organization described here is still in existence, although the Western Development Division has undergone periodic name changes. Today, it is the Air Force Space and Missiles Division. This organization still receives technical support from the Aerospace Corporation just as it did half a century ago.
The Western Development Division was given the job of developing three missile systems, two ICBMs, the Atlas and the Titan, and one intermediate range ballistic missile (IRBM), the Thor.
The Thor Missile and the Delta Space Launcher. The Thor first stage is a missile that has roughly the same performance characteristics as the Army’s Redstone missile. The decision to go ahead with the Thor was controversial because of the apparent duplication of effort. Eventually, the Joint Chiefs of Staff approved the proposal to go ahead with both missiles. In December 1955, the Douglas Aircraft Company was given the contract to develop the missile. The first successful flight of the Thor was carried out on 20 September 1957, and the first operational missiles carrying warheads were deployed in the United Kingdom in 1958, 3 years after the contract was given to Douglas. This remarkably rapid development cycle was due to General Schriever’s push for ”concurrency.” This means essentially that calculated risks are taken in the development process to speed the schedule and, in this case, the adoption of ”concurrency” succeeded.
Both the Thor and the Jupiter MRBM had pressurized, regeneratively cooled rocket motors that developed thrusts of about 150,000 lb. Unlike the Redstone, which burned ethanol and liquid oxygen, the Thor burned a kerosene liquid oxygen mixture. It was also designed to be very rugged, and this is the feature that has led to the large number of versions of the Thor, so that it has been called, justifiably, the workhorse of space launchers. It is truly remarkable that space launch vehicles based on the Thor started in the late 1950s with the capability of placing a few hundred pounds in near Earth orbit and now can place a payload of more than 8000 lb. into a geostationary transfer orbit.
The Thor has carried a number of upper stage vehicles. One is the Agena, built originally by the Bell Aerospace Company and later by the Lockheed Corporation. It will be described later. The most important booster stage was the ”Delta” solid-fueled rocket built by Aerojet General Corporation that had a thrust level of 8,000 to 10,000,lb depending on the version used. The Delta stage was used so frequently with the Thor that the combination is now called the ”Delta.”
The second important thrust augmentation for the Thor is the Castor rocket built by Thiokol Corporation. These are powerful solid-fueled rockets that are strapped to the bottom skirt of the Thor rocket. Each unit has a thrust level of 50,000 lbs, and they can be strapped on in numbers between three and nine. The Castor rocket capability adds both power and flexibility to the Delta space launch vehicle system. More than 200 successful Delta rocket launches have been conducted since the first Thor was launched in 1957.
The Delta launch family originated in 1959 when the NASA Goddard Space Flight Center awarded a contract to Douglas Aircraft Company to produce and integrate 12 launch vehicles. Using components from the U.S. Air Force Thor intermediate range ballistic missile (IRBM) program and the U.S. Navy Vanguard launch program, the Delta rocket was available 18 months after the award. On 13 May 1960, the first Delta was launched from Cape Canaveral Air Force Station, Florida, carrying a 178-pound Echo I passive communication satellite. Although the first flight was a failure, the ensuing series of successful launches established Delta as one of the most reliable of all U.S. boosters.
The Delta II Space Launcher. For more than 40 years, the Delta system has consistently demonstrated its robust design, launch flexibility, and value to launch service customers. A second generation, the Delta II launch system, was developed to include multiple configurations to suit the needs of the U.S. Air Force, the National Aeronautics and Space Administration (NASA), and to accommodate the emerging commercial satellite market.
From 1985 through 1987, the space industry was impacted by an unprecedented string of failures of various launch systems, which seriously impeded U.S. space launch capability. In one ofseveral steps to revitalize assured access to space, the U.S. Air Force held a competition for a medium launch vehicle that primarily would launch Global Positioning Satellites (GPS). The contract was awarded to McDonnell Douglas (now Boeing) for its Delta II series vehicles. With a 98.1% mission success rate since its inception in 1989 the Delta II has become the industry workhorse for deploying remote sensing satellites for U.S. government and commercial applications, GPS, commercial satellite systems/constellations, and numerous planetary missions for NASA.
In addition to the demonstrated reliability of the Delta II launch system, Delta vehicles provide incremental performance capability with three, four or nine Castor solid rocket motor (SRM) configurations. These configurations provide a broad range of performance, from 2000 to 4000 pounds to geosynchronous transfer orbit (GTO), using the highly reliable Rocketdyne RS-27A main engine, and two- and three-stage configurations. The latest version, which is designated Delta II Heavy, integrates the solid rocket motors (SRMs) used on Delta III with the Delta II standard upper stage, resulting in approximately a 12% increase in payload lift performance from the standard nine SRM configuration to more than 4700 pounds to GTO (Fig. 3) (6).
The Delta II launch system payload accommodations provide various mechanical interfaces, separation systems, and deployment systems that are designed for compatibility with launch industry standard interfaces. Payload accommodations enable deploying single, dual, or multiple satellites in a single Delta II launch. The multiple manifest, spacecraft dispensers have successfully deployed 55 Iridium spacecraft, five per launch on eleven launches, and 24 Glo-balstar spacecraft, four per launch on six launches.
Delta II and III space launch vehicles. This figure is available in full color at http://www.mrw.interscience.wiley.com/esst.
Figure 3. Delta II and III space launch vehicles.
The Delta II is launched in the United States from three launch pads, two on the East Coast at Cape Canaveral Air Force Station that has a capacity of 12 launches and one on the West Coast at Vandenberg Air Force Base, California, that has a potential of nine launches per year. Launch sites on both coasts enable the Delta II launch system to launch to virtually any orbit and provides customers with launch schedule assurance.
The demand for Delta II launches increased significantly in the mid- and late 1990s and has continued to maintain a steady backlog of government and commercial customers. In addition to continuing GPS deployment missions, Delta II has been selected for numerous NASA payloads because of NASA’s focus on smaller, less expensive spacecraft and its demand for proven reliable launch systems. NASA remains a critical customer for Delta launches, Delta II has assigned and planned missions through 2009.
Building on the success of the Delta II launch system, McDonell-Douglas developed the two-stage Delta III in the mid- to late 1990s to address the trend toward increasing mass of commercial satellites. The Delta III nearly doubled the payload lift capability of the Delta II launch system by deploying an 8400-pound payload to GTO. Delta III evolved from the highly reliable Delta II by maximizing the use of common components and infrastructure. Both launch systems use the same Rocketdyne RS-27 main engine, first stage LO2 tank, flight avionics, and launch operations infrastructure. Most notable of Delta III’s evolved features are a 13-foot diameter cryogenic second stage, 13-foot diameter composite biconic payload fairing and nine, larger, more powerful SRMs (46-inch dia.). The second stage uses a single RL10B-2 engine fueled by LH2 and LO2 that incorporates an extendable nozzle.
The Delta III established itself as an operational launch system in August 2000 by launching a 9460-pound demonstration payload to a planned subsyn-chronous GTO. The mission was successful; all of the systems and subsystems performed as planned. Intended to be a transition vehicle to the Delta IV, the Delta III has enabled demonstration and flight qualification of several critical components that would be used on the Delta IV.
The Atlas Intercontinental Ballistic Missile (ICBM) and Space Launcher. Concurrently with the development of the Thor, the U.S. Air Force also undertook to develop the first large truly intercontinental missile—the Atlas. This missile included a number of innovative design features. The first and most important of these was that the body of the rocket vehicle was also the wall of the pressurized fuel and oxidizer tanks, and unlike the Thor and Redstone, both of which had conventional braced aluminum air frames, the Atlas skin was manufactured from a thin sheet of stainless steel. The Atlas could only stand on a launch pad if the tanks were pressurized; if they were not, the vehicle would collapse. The pressurized steel tank thus assumes some of the structural burden. This design saves enough weight, so that the Atlas dry weight fraction was the smallest of any large rocket yet built.
The propulsion system of the Atlas was also unique. It consisted of three engines, one mounted on the centerline of the vehicle and the other two fitted on a skirt and placed on either side of the center engine. At launch, all three Rock-etdyne MA5 engines would be running, generating a total thrust of 370,000 lb. The skirt, called the ”booster section,” could be jettisoned at an appropriate time, and the center engine, called the ”sustainer,” would continue to run, generating 60,000 pounds of thrust until the propellant is consumed. This concept is called ”stage and a half” because no fuel is carried in the booster section, so that no fuel tank is dropped. The engines burned RP-1 (kerosene) using liquid oxygen as the oxidizer. The engines were gimballed for thrust vector control, as was the Vanguard rocket mentioned earlier.
The Atlas program was initiated in 1951, and the contract to develop the rocket was given to Convair/General Dynamics Corp. The first successful flight of an Atlas ICBM occurred in December 1957, and the first employment as a space vehicle launcher occurred in December 1958 when it was used to put an active communications satellite that weighed about 200 pounds into Earth orbit.
Since these first flights, the Atlas, in combination with a number of different upper stages, has been a very successful space launch vehicle. Perhaps the most important launch of an Atlas booster was John Glenn’s first flight in the Mercury program. The Mercury spacecraft, ”Freedom Seven,” was placed into Earth orbit by a modified Atlas D ICBM on 20 February 1962 (Fig. 4). The Atlas has also been used very effectively with Agena, Centaur, Delta, and Burner upper stages. (The technical details of these upper stages will be discussed more thoroughly later.) The Atlas/Agena combination was used for some of the first Mariner Missions (Mariner 4) that returned the first pictures from a Mars flyby in July 1965. The Atlas/Agena was also used to send a Ranger spacecraft to the Moon for a hard landing, and it placed the Lunar Orbiter around the Moon as well. The latter spacecraft was particularly important because the high resolution pictures it obtained were used to select the landing sites for the Apollo landings. The Atlas/Centaur combination is a more capable launch vehicle that was used to put
Launch of John Glenn's Mercury ''Freedom Seven'' spacecraft by an Atlas space launch vehicle. This figure is available in full color at http:// www.mrw.interscience.wiley.com/esst.
Figure 4. Launch of John Glenn’s Mercury ”Freedom Seven” spacecraft by an Atlas space launch vehicle.
The most interesting application of the Atlas/Centaur was launching the Pioneer 10 spacecraft on 3 March 1972, as well as its sister ship, Pioneer 11, 13 months later. Pioneer 10 was the first spacecraft to pass beyond the orbit of Mars, to fly through the asteroid belt, to fly past Jupiter, and finally, it became the first human artifact to leave the solar system. Pioneer 11 repeated this performance a year later, and, in addition, it became the first spacecraft to fly by Saturn.
The Atlas II family was developed in the mid-1980s to address the growing demand for large commercial geosynchronous satellites. The Atlas II family has a 100% success rate and 56 consecutive launches, a reliability record unmatched in the industry. During the past decade, the Atlas II vehicle has been continually stretched and upgraded to improve payload performance. The Atlas IIAS is the most powerful and has the highest lift capability of the Atlas II family. Other configurations include the Atlas IIA and the Atlas II, which was retired in March 1998. Currently, Atlas II vehicles are being flown from both U.S. ranges.
Four solid fuel rockets are used to augment payload performance of the Atlas IIAS. All three MA-5 engines are ignited prior to liftoff. Approximately 180 seconds into first-stage ascent, the two larger MA-5 booster engines are shut down and jettisoned, reducing weight and improving payload performance. The center MA-5 sustainer engine burns for an additional 100 seconds up to main engine cutoff and staging. The Centaur second stage uses two RL-10A-4 engines to place up to 6700 lb (Atlas IIA) and 7950 lbs (Atlas IIAS) into a GTO orbit.
In the early 1990s, General Dynamics (now a part of Lockheed Martin) decided to upgrade the Atlas first-stage propulsion system. The prime modification was replacing the two MA-5 first-stage and single MA-5 sustainer engines with a single Russian NPO Energomash RD-180. Furthermore, Lockheed Martin simplified vehicle construction by drastically reducing the total part count. The reengined vehicle, known as the Atlas IIAR, has since been renamed the Atlas III. The maiden flight of the Atlas III launch vehicle, the replacement for the Atlas II, occurred on 24 May 2000.
Two versions of the Atlas III are currently available. The Atlas IIIA has a single RL-10A-4-2 engine powering the Centaur upper stage, whereas the Atlas IIIB has two RL-10A-4-2 engines and a stretched Centaur upper stage to increase GTO performance to just under 10,000 lb (Fig. 5) (7).
The Titan ICBM and Space Launch Vehicle. One of the limitations of the Redstone, the Thor, and the Atlas as military missiles was that they could not be kept on ”instant alert.”. This meant that they could not be launched on very short notice because the liquid oxidizer (liquid oxygen) is a liquid only at 210°C below room temperature so that it cannot be stored on the missile itself. Special cryogenic storage facilities had to be build at each of the military launch sites, and upon the order to launch the missile, the liquid oxygen had to be transferred from the storage tank to the missile. Such operations take, at best, something of the order of half an hour, which means that an instant ”launch on alert” is not possible.
The Titan missile actually started as a replacement for the Atlas because the fragility of the Atlas was deemed undesirable for deployed military rockets. The Titan was thus designed using the more rugged monocoque technique in which an appropriately braced aluminum ”fuselage” took the stresses of the launch. Originally, the first version of this missile, the Titan I, was designed for conventional fuels and would be placed in hardened underground shelters. A successful test was conducted in February 1959, and the Titan I system became operational in 1962. In spite of this, the system was awkward to operate, and the Air Force decided to convert the Titan I to a missile that could use storable fuels so that it could be maintained on instant alert. The implementation of this idea led to the Titan II ICBM.
The Atlas space launch vehicle family. This figure is available in full color at http://www.mrw.interscience.wiley.com/esst.
Figure 5. The Atlas space launch vehicle family.
The Titan I ICBM was somewhat more capable in range and payload than the Atlas. The Titan II had to be substantially more capable. The storable fuel chosen for the Titan II was a mixture of nitrous oxide (N2O4) and “Aerozine,” a hydrazine-based fuel. These two substances are liquids at room temperature, and they ignite when they come into contact, that is, they are hypergolic. Thus, with appropriate care, they can be stored on the missile itself. However, the hypergolic fuel mixture does not have the same high specific impulse of the liquid oxygen/hydrocarbon fuels, so that the rocket is not as effective as a launch vehicle. Thus, the Titan II ICBM was designed from the very beginning as a two-stage system, which gave it substantially better performance than the Atlas. The Titan II second-stage motor was also fueled by a hypergolic mixture, so that the entire vehicle could be stored at room temperature
The first successful test of the Titan II was carried out on 16 March 1962, and the first operational missile was installed in its hardened underground bunker in December 1962. Ultimately, 51 Titan II missiles were deployed at three sites near Wichita, Kansas; Tucson, Arizona; and Little Rock, Arkansas. The Titan II was a formidable part of the U.S. nuclear deterrent force; it carried a multimegaton warhead that could reach targets 8000 to 10,000 miles away. In September 1980, a technician at one of the Titan II missile sites in Arkansas dropped a wrench down the silo and it punctured the fuel and oxidizer tanks as it fell. Eventually, the two liquids mixed, ignited, and the resulting conflagration destroyed the missile and silo. Fortunately, the nuclear warhead, which had a hardened design, survived the accident unharmed. Partly as a result, all of the deployed Titan II ICBMs were decommissioned by 1987.
Like the Thor and the Atlas, the Titan II ICBM was also converted into a very flexible and capable space launch system. The first of these, fielded in 1964, was called the Titan IIIA; it consisted of the Titan II two-stage ICBM plus a third stage called “Transtage” that could put payloads of more than 3000 pounds into low Earth orbit. This was followed quickly by the Titan IIIB/Agena in 1966 that could put 8500-pound payloads into near Earth orbit. This was accomplished by increasing the thrust of the first stage from 430,000 to 463,000 pounds and using the somewhat more capable Agena rather than the Transtage. All of these modifications were carried out by the Martin Company.
The Titan II space launch vehicle is a two-stage liquid-fueled booster designed to provide small-to-medium weight class capability. It can lift approximately 4200 pounds into a polar, low Earth circular orbit. Titan IIs were also flown in NASA’s Gemini manned space program in the mid-1960s. Deactivated Titan II missiles are in storage at Davis-Monthan Air Force Base in Tucson, Arizona. Lockheed Martin was awarded a contract in January 1986 to refurbish, integrate, and launch 14 Titan II ICBMs for government space launch requirements.
Tasks involved in converting the Titan II ICBMs into space launch vehicles included modifying the forward structure of the second stage to accommodate a payload; manufacturing a new 10-ft diameter payload fairing with variable lengths plus payload adapters; refurbishing the Titan’s liquid rocket engines; upgrading the inertial guidance system; developing command, destruct, and telemetry systems; modifying Vandenberg Air Force Base Space Launch Complex 4 West to conduct the launches; and performing payload integration. Six Titan II Space Launch Vehicles have been launched from Vandenberg Air Force Base, California, since 5 September 1988.
The major modification of the Titan III could be made because of the sturdy monocoque construction of the original Titan II missile. This was the addition of two very large solid-fueled strap-on rockets on opposite sides of the Titan II core vehicle. These rockets have a thrust of just over 1,000,000 pounds each, which raises the takeoff thrust of the entire vehicle in the launch configuration to about 3,000,000 pounds. This configuration of the launch vehicle is called Titan IIIC, and with a Transtage, it can place about 30,000 pounds in low Earth orbit. It can place a payload of about 3600 pounds in a geosynchronous orbit by using the appropriate upper stages. Another important variation is the Titan IIID, which has no upper stages but can put a 13,000-pound payload into near Earth polar orbits. This is the launch vehicle that, when launched from the West Coast at Vandenberg Air Force Base, puts most of the U.S. highly capable reconnaissance satellites in orbit. The Titan IIID was declared operational in 1971.
In 1977, the Titan IIIE/Centaur was fielded. This is the most capable expendable space launch vehicle in the current American inventory. The addition of the Centaur upper stage makes the difference (Note: The upper stage will be described in more detail later.) The Titan IIIE/Centaur has launched a whole galaxy of spacecraft to explore everything from the outer planets using exquisitely designed cameras to putting very sophisticated payloads into the atmosphere of Jupiter. This would include Helios, Galileo Jupiter with the probe, the two Voyagers, the two Vikings, and a substantial number of others. A related version of the Titan IIIE is the Titan 34D which, instead of carrying the Centaur, carries a solid-fueled upper stage called the ”inertial upper stage” or IUS. This stage was developed by the Air Force to put large military and intelligence gathering satellites into polar orbits.
Titan IV consists of two solid-propellant, stage-zero motors, a liquid propellant two-stage core and a 16.7-ft diameter payload fairing. Upgraded three-segment solid rocket motors increase the vehicle’s payload capability by approximately 25% (Fig. 6) (7). In 1985, the U.S. Air Force selected the Martin Marietta Astronautics division (now Lockheed Martin) in Denver to build and launch 10 Titan IVs. In 1986, the contract was increased to 23 vehicles, and, in November 1989, the contract was extended to 41. Titan IV has been used exclusively to launch U.S. government satellite missions. It provides primary access to space for critical national security and civil payloads.
The operating success rate of Titan launch systems is better than 95%. It can place 47,800 lb into low Earth orbit or more than 12,700 lb into geosynchronous orbit.
Titan IV is launched from Launch Complex 40 at Cape Canaveral Air Force Station, Florida, and from Space Launch Complex 4E at Vandenberg Air Force Base, California. The first Titan IV B was successfully flown from Cape Canaveral Air Force Station on 23 February 1997. This configuration improves reliability and operability and increases lift capability by 25%. Advancements also include improved electronics and guidance. The Titan IV B has standardized vehicle interfaces that increase the efficiency of vehicle processing. Additionally, the more efficient programmable aerospace ground equipment is used to monitor and control vehicle countdown and launch.
Upper Stages. In describing the evolution of military missiles to become space launchers, we mentioned a number of upper stages used in combination with the military rockets to place spacecraft into Earth orbit and beyond. In this section, we will provide brief descriptions of the most important.
The Titan IV space launcher. This figure is available in full color at http:// www. mrw. interscience.wiley. com/esst.
Figure 6. The Titan IV space launcher.
The Centaur, developed and built by Convair/General Dynamics, is the most capable of these vehicles. The Centaur uses liquid oxygen to burn hydrogen fuel. This mixture is the most potent of all chemical rocket fuel combinations because it provides the highest specific impulse to the rocket. Thus, rockets using this combination have the highest propulsive efficiency. The Centaur can be shut down and restarted in space, which is most important because it permits executing complex space maneuvers. However, because the fuels are cryogenic, these maneuvers have to be carried out shortly after launch, so that the fuel and oxidizer are not lost by evaporation. The Centaur has two Pratt and Whitney RL-10 engines that develop a total thrust of 30,000 pounds. The first Centaur was flown in 1962, and since then, Centaur upper stages have been used on top of Atlas and Titan boosters.
The Agena is the second important liquid-fueled upper stage. The Agena also uses a hypergolic fuel/oxidizer mixture of (N2O4) and unsymmetrical dimethyl hydrazine (UDMH) to provide a thrust of about 15,000 pounds. The Agena also has shutdown and restart capability like the Centaur. The difference is that the fuel/oxidizer mixture can be stored at ambient temperature, so that the Agena vehicle can stay in orbit in a dormant condition much longer than the Centaur. The Agena has been used on Thor, Atlas, and Titan rockets and has proven to be the most ubiquitous of the high-performance liquid upper stage vehicles. The Agena was originally designed and built by the Bell Aerospace Company for the Atlas and was later taken over by the Lockheed Missiles and Space Company (now called Lockheed Martin Co.). It was flown for the first time in 1960 on an Atlas booster.
Solid-fueled rockets have been used extensively as upper stages for space launch vehicles ever since the first orbital flights. The Juno I launcher, which placed Explorer I in Earth orbit in January 1958, had three solid-fueled upper stages, including a small solid booster on the Explorer I satellite itself. Solid-fueled rockets have the advantage that they are safely storable and also extremely versatile. They have ranged from the small rockets already mentioned that might develop tens of pounds of thrust to the huge strap-on rockets of the Titan IIIC that develop thrust levels of more than a million pounds. The primary disadvantage of solid-fueled rocket boosters is that, except in certain cases, such as the two-grain systems used in antimissile applications, they cannot be turned off once they are lit. Another disadvantage is that failure of solid-fueled rocket is usually catastrophic—which was unfortunately graphically illustrated in 1986 by the failures of a solid rocket booster in January that caused the loss of “Challenger” and then again in April that caused the loss of a Titan 34D flight.
There are too many solid-fueled upper stages to list here. Probably the most important and capable solid-fueled upper stage is the inertial upper stage (IUS) that was built by the Air Force for use with the Space Shuttle and the Titan 34D system.

The Evolved Expendable Launch Vehicle Program (EELV)1

The EELV Concept. The Evolved Expendable Launch Vehicle program, born of studies conducted in the late 1980s and 1990s, represents a commitment to 1 Excerpts from input by James Simpson, The Boeing Company reducing significantly the cost of access to space. An industry/government partnership has developed two competing EELV systems to meet space transportation needs during the next 20 years (8).
Conceived as a ”system of systems” to improve operability and reduce recurring and infrastructural costs, EELV is using streamlined manufacturing and improved mission assurance processes. Its facilities and operations are designed to lower costs.
Requirements call for a 25-50% reduction in recurring operational cost compared to current systems and for improving system reliability and availability. The U.S. Air Force interest is that EELV will replace the Titan, Atlas, and Delta vehicles and their launch infrastructures supported by DOD. The program implements DOD acquisition excellence goals by streamlining the government’s role and replacing its oversight of contractors with less intrusive ”insight.” The objective is to enhance U.S. launch industry competitiveness in the international market by reducing costs across the entire system.
In October 1998, the government awarded $500 million contracts each to Boeing and Lockheed Martin. Development costs are shared between the contractors and the government, resulting in a national, dual-use launch service. The government program office has virtually unlimited access to all but some highly sensitive and proprietary cost and pricing data. The Air Force simultaneously awarded initial launch service contracts to both firms.
The strategy enabled two further benefits: competition and assured access to space. Having two competitors throughout the life cycle of the program is key to achieving price competitive procurement. Two providers using a standard payload interface maintain payload interchangeability between Delta IV and Atlas V and enhance assured access to space.
Each delivery order for a launch service has a standard 24-month period for performance. Individual launch service plans, however, are highly flexible and can be tailored to spacecraft customer needs.
EELV will support U.S. military intelligence, civil, and commercial mission requirements using contractor-provided commercial launch services. The two are the Boeing Delta IV and Lockheed Martin Atlas V, both designed to meet the full range of government launch requirements.
The EELV program has three key performance parameters: specific payload mass-to-orbit requirements; vehicle design reliability of 0.98 (threshold) at a 50% confidence level; and standardization, including standard payload interface for each class of vehicle and standard launch pads that can accommodate all configurations in an EELV family (9).
Delta IV. Delta IV was developed under a U.S. Air Force EELV contract. The Delta IV launch vehicle uses a new liquid oxygen/liquid hydrogen 16.7-foot diameter common booster core (CBC) powered by the new Boeing-Rocketdyne RS-68 main engine. This is the first large liquid-fueled engine to be developed in the United States since the SSME (Space Shuttle main engine). The RS-68 is a gas generator liquid oxygen/hydrogen booster engine. The bell-nozzle RS-68 develops 650,000 pounds of sea level thrust and uses a simple design approach that has drastically reduced the total part count compared to engines of equivalent size or performance. The vehicle’s cryogenic upper stage, which uses the Pratt & Whitney RL10B-2 engine, is substantially similar to that flown on the Delta III (6,9,10).
There are several variants of the Delta IV launch vehicle. The Delta IV-M (medium) is a single-core variant that combines the CBC with a version of the Delta III liquid oxygen/hydrogen second stage and a stretched 4-meter fairing that provides 9200 pounds to GTO. The Delta IV-M + variants augment the single core with two or four solid rocket strap-on Alliant Techsystems graphite epoxy motors (GEMs) and provide two variations of upper stages and payload accommodations, the 13-foot Delta III derivative and the 16.7-foot version that has greater fuel capacity and greater payload volume. The M + variants enable payload deployment of 14,700 pounds to GTO. The Delta IV vehicle family will have a GTO lift capability of up to 29,500 pounds and is available in three major variants. The largest variant, the Delta IV-Heavy, combines three CBCs with the 16.7-foot upper stage. The payload accommodations include either a 16.7-foot isogrid aluminum fairing based on the existing Titan IV or a newly developed composite fairing based on the Delta II and Delta III designs. The 13-foot fairing is the existing Delta III composite fairing lengthened by 3 ft (Fig. 7) (6).
Improvements include the new CBC, the newly developed and simplified main cryogenic engine, the focused factory facility, and simplified launch-processing operations.
Parts for the medium-plus and heavy CBCs are, respectively, 88% and 93% common relative to the medium CBC. All are manufactured using a common factory production list. CBC innovations include friction stir-welded tanks, spun-formed domes, and the use of composite structures. The RS-68 has reduced operating pressure, 80% lower part count, 95% less labor, uses cast versus welded parts, and has no special coatings. However, more than 85% of the upper stage part count is a Delta III heritage, and much of the avionics are from Delta II and III.
Full integration, assembly, and checkout testing take place before each vehicle leaves the factory. Delta IV’s horizontal booster processing flow and vehicle stage mating in the horizontal integration facility allow parallel integration, reduced hazardous lifting operations, and decreased pad time. Total vehicle time at the launch base is less than 1 month and only 8-11 days on the pad. Delta IV features launch sites on both the East Coast (Cape Canaveral Air Force Station, Florida) and West Coast (Vandenberg Air Force Base, California). Each pad can launch all configurations, and launch pads are virtually standard between the Cape Canaveral SLC-37 and Vandenberg SLC-6 launch sites.
Atlas V. The Atlas V vehicle family, developed under the U.S. Air Force EELV contract, builds on the improvements made for the Atlas III. The Atlas V family of vehicles incorporates a reinforced first-stage structure, as well as increased propellant load in the first stage, called the common core booster (CCB) powered by the Russian RD-180 engine. The RD-180 is produced by RD AM-ROSS, a joint venture between Pratt & Whitney and Russian’s NPO Energomash. The engine develops 860,000 pounds of thrust at sea level, uses liquid oxygen/RP-1 propel-lants, and is the only high-thrust, staged-combustion engine in production. It has been tested extensively and was flight proven on the first Atlas IIIA mission in May 2000 (Fig. 8) (7).
Evolved Delta. This figure is available in full color at http://www.mrw. interscience.wiley.com/esst.
Figure 7. Evolved Delta.
Lockheed Martin has proposed variants of the Atlas V that incorporate different arrangements of solid strap-on boosters to increase the payload performance of the single common core variant up to 18,000 lb to GTO. To differentiate the various Atlas V configurations, Lockheed Martin devised a secondary numbering system. The first number identifies the fairing diameter in meters (3,4, or 5-meter fairing). The second number identifies the number of solid strap-on boosters (0 through 5). The final number identifies the number of second stage RL-10 engines (either 1 or 2). As an example, an Atlas 5 532 has a 5-meter fairing, three solid strap-on boosters, and two second-stage RL-10 engines. A single engine RL-10 second stage is used for high altitude (MEO and GTO) missions, whereas the two-engine variant is used for LEO missions.
Atlas Vs several configurations have the flexibility to meet varied performance requirements for missions from LEO to GTO. Options include the addition of one to five Gencorp Aerojet strap-on solid rocket motors for intermediate lift capability or the use of three CCBs for heavy payloads. The Atlas 400 series has a 13-foot payload fairing and a single CCB; the 500 series has a composite 16.7-foot payload fairing, a single CCB, and up to five Aerojet solid rocket boosters; and the heavy launcher has three CCBs and a composite 18-foot payload fairing. All three series use a common Centaur upper stage with Pratt & Whitney RL10A-4-2 engines(s).
Evolved Atlas. This figure is available in full color at http://www.mrw. interscience.wiley.com/esst.
Figure 8. Evolved Atlas.
These modifications, combined with the stretched Atlas IIIB Centaur upper stage, allow the Atlas V to place more than 10,000 lb in a geosynchronous transfer orbit with the single CCB. The heaviest variant of the family currently planned for production will incorporate an arrangement of five solid strap-on boosters to increase the payload performance of the single common core variant up to 18,000 pounds to GTO. Lockheed Martin has designed a three common booster variant capable of placing more than 13,000 lb directly into a geostationary orbit that is currently not being marketed commercially (8,10).
Atlas V, which uses the same Centaur upper stage as the Atlas IIIB, can be configured with either one or two RL10A-4-2 engines. A hydrazine attitude control system provides precise in-orbit maneuvering. The 18-foot payload fairing is a new design derived from the Ariane V fairing manufactured by Contraves Space of Switzerland. It will be offered in two lengths, one optimized for communications satellites and the other for accommodating large-volume spacecraft missions. The 13-foot payload fairing is the same one used on Atlas II and III. Among Atlas V’s innovations is the RD-180 engine capability for continuous throttle between 47 and 100% of nominal thrust, which allows substantial control over launch vehicle and payload environments. Others include reduced manufacturing cycle time and simplified launch processing. Atlas V also includes the Air Force EELV standard payload interface that allows payload interchange-ability with Delta IV (8).
Atlas V incorporates efficient launch site processing, including use of an off-pad vertical integration facility (VIF) for the vehicle and parallel processing of the encapsulated payload in separate installations. Launch site processing has been reduced from 28-38 days for Atlas II to just 18-26 days. The encapsulated payload will be transported to the VIF and mated to the launch vehicle. After combined systems testing, the fully integrated Atlas V/encapsulated payload will be transported to the nearby ”clean launch pad.” All vehicle configurations use common processing procedures and can be launched from the same clean pad. On-pad time has been reduced to less than 1 day.
Current Status. The Lockheed Martin-built Atlas 5 401 (single CCB, no solids, and single engine Centaur) booster launched flawlessly on 21 August 2002 deploying the Hot Bird 6, a communications satellite for Eutelsat.
The 12.5-foot diameter rocket was the largest to launch from Cape Canaveral since the Saturn 5 sent Apollo astronauts to the Moon. This flight gives the Atlas family a string of 61 consecutive successful launches during 9 years using the Atlas II, Atlas III, and Atlas V vehicle configurations.
On 20 November 2002 the Delta IV-M + 4,2 carried the W5 communications satellite for Eutelsat to a precise geostationary transfer orbit.
The Department of Defense and related agencies (e.g., NASA), as well as the commercial sector, will be major customers for both vehicles. The Pentagon has scheduled 29 launches aboard the rockets to date.


Conclusions

It is truly remarkable that from Goddard’s first liquid-fueled rocket flight to the landing on the Moon was a mere 43 years—well within the lifetimes of many people living today. The spurs for this achievement were clearly the Second World War (1939-1945) and later, the Cold War (1948-1991). In both cases, the technology of rocket propulsion was considered critical by all concerned to prevailing in the conflicts. However, this is only half the story. The other half is that a group of unusually talented and motivated people from many nations contributed to the successes that we have described. The principal technical conclusion that can be drawn from what has been said here is that the technology of chemically fueled rockets is mature. For the past 40 plus years, since the development of the ICBMs in the early 1960s, no new propulsion technology has been developed and applied. What has happened is that the proliferation of liquid- and solid-fueled chemical rockets has made it possible to develop a very large number of launch vehicle combinations tailored to meet a great many different requirements for expendable space launchers. This, of course, is what is meant by the term ”evolution” in the title of this article. For the foreseeable future, this evolution will continue and will be made possible by advances in guidance and control systems, more accurate timing and navigation, and other auxiliary technologies. It is a tribute to the designers of the early ICBM rockets that their products are still in our front line expendable space launchers.
What of the future? We believe that there are now signs on the horizon that new technologies for space launch systems will be required. We are on the threshold of initiating human exploration of the solar system. The International Space Station will be the staging base for this new phase of space exploration. We believe that both electric propulsion systems and nuclear rockets will be assembled at the space station and will eventually take people and equipment on journeys around the solar system. Hopefully, the designers and builders of these new propulsion systems will display the same skill and virtuosity as the people who created the space launchers described in this article.

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