The Air Force and the Ballistic Vehicle Build-Up
 Although the Army had shown great initiative in ballistic missile development, the Air Force became the dominant military service in long-range, ballistic missiles. The Air Force had the responsibility for developing the Atlas and Titan intercontinental ballistic missiles (ICBM), the Thor intermediate range missile, and later, the Minuteman, an all-solid-propellant missile.
The Atlas and Titan had a range of about 10 000 kilometers and a payload capability of 700 kilograms. The Atlas was powered by two 667-kilonewton (150 000 lb thrust) first-stage engines plus a 267-kilonewton (60 000 lb) sustainer engine. At launch, all three engines operated and at the end of first-stage operation, the two large engines were jettisoned leaving the sustainer engine to continue to operate during the second phase. Propellants for all three engines came from common tanks which constituted the bulk of the structure. These tanks were made of thin-gage stainless steel and depended upon internal pressure for structural stability. Since Atlas jettisoned only its first-stage engines, it was called a 1 1/2 stage vehicle. Titan I, on the other hand, was a  conventional two-stage vehicle which jettisoned both first-stage engines and associated tankage. Its tanks were of the more conventional design with internal ribs for structural stability. Titan I's engines were similar to those for Atlas, and both vehicles used a jet-grade fuel similar to kerosene, with liquid oxygen as oxidizer.*
The Atlas, developed by the Convair division of General Dynamics Corporation, is of special interest to our story.** As one of two contractors studying 8000 kilometer vehicles for the Air Force in 1947, Convair chose a ballistic missile over a winged, subsonic vehicle-a bold decision at the time. A key to long-range ballistic missiles was achieving very light structures and an imaginative Convair engineer, Karl J. Bossart proposed several bold innovations for light structures. By the end of 1948 and three test flights, Bossart was able to incorporate his innovations into the Atlas design. One was the use of integral, thin-wall, pressure-stabilized tanks previously mentioned. Although Oberth had proposed such balloon-like tanks in 1923 and both the Glenn L. Martin Company and North American Aviation had used the concept in satellite designs for the Navy (pp. 41, 44), such tanks had never been built and flown. Bossart had independently conceived the idea during design calculations when he found that the tank pressure needed for the inlets of the engine's pumps was greater than the internal pressure necessary for the tanks to remain stable under aerodynamic forces and vehicle loading. Bossart also dispensed with insulation for the liquid oxygen tank and used swiveling rocket nozzles to control the pitch, yaw, and roll of the vehicle during flight.7
Bossart's innovations and the initial Atlas project aroused little interest until the early 1950s when the Air Force swung away from air-breathing propulsion and winged missiles in favor of ballistic missiles. The break for Atlas came in 1954 when the Air Force Strategic Missiles Committee recommended that it be developed with some changes. The committee also recommended that a new management group be established to accelerate ballistic missile development. This resulted in the formation of the Ballistic Missile Division of the Air Research and Development Command under Brig. Gen. Bernard Schriever, and the ballistic missile program began to accelerate. In fiscal year 1953, funding was $3 million; in FY 1954, $14 million; in FY 1955, $161 million. In February 1955, another advisory committee recommended additional development of intermediate range ballistic missiles (IRBM) with a range of 2800 kilometers. By the summer of 1955, the Air Force had two ICBMs (Atlas and Titan) and one IRBM (Thor) under development. The Army won approval to develop the Jupiter IRBM.*** The Navy turned to solid propellants and the Polaris missile was initiated. The Air Force also became interested in solid-propellant missiles and in 1957 began development of the Minuteman. During this period, funding continued to climb: in FY 1956, $515 million; in FY 1957, $1.3 billion.8 Thus, by the time of Sputnik, six U.S. missiles were being developed with the highest national priority, and  all were larger and had greater payload capability than Vanguard. By 1958, development of liquid-prope llant missiles not only provided the basic technology applicable to future launch vehicles but also the vehicles themselves were to become the greater part of the first generation of launch vehicles.
A key technology responsible for achieving low structural weight of the Atlas missile was Bossart's thin-gage, pressure-stabilized tanks. This concept met with considerable skepticism during the development of the Atlas. Opponents pointed out that if pressurization should fail, the tanks-and the missile-would collapse of their own weight. An equal concern was how well the tanks could withstand high aerodynamic loads during the early part of a flight. Doubt was sufficiently widespread that Titan, the second ICBM, was built with tanks of conventional design. An unanticipated severe test of the pressure-stabilized tanks came with the first test flight of Atlas in 1957. Hot exhaust from the turbopump burned through control wiring and the vehicle began to tumble while still in the atmosphere, placing excessive loads on the tanks. They held, and anyone viewing the film of the flight could easily become a convert to Bossart's concept. In spite of this, however, some engineers remained unconvinced, and prominent among them were those in the von Braun team.**** This attitude was important to their later consideration of liquid hydrogen, as we will see.
During the build-up of missile capability in the 1950s, President Eisenhower and the Department of Defense kept booster programs closely related to surface-to-surface military requirements, much to the disappointment of space enthusiasts. A prevailing attitude was that spaceflight was not yet practical, and work to make it so was far too costly to be taken very seriously. To be sure, there was tolerance for research on high-energy propellants and other means for achieving high rocket velocities, but it was peripheral to the main task of developing long-range ballistic missiles. Up to the time of Sputnik, talk of spaceflight was very unpopular in the halls of government and proponents had to tread very lightly. "Space Cadets" were frowned upon and the use of the word "space" in a proposal in pre-Sputnik days invited budget cuts within the executive branch and in Congress.
** Consolidated Aircraft became Consolidated-Vultee (Convair) in 1943 and was absorded by General Dynamics in 1954. The division building rockets has been named Convair, Astronautics, and now Convair-Aerospace.
*** Jupiter, developed by the Chrysler Corp. for the Army, is not to be confused with Jupiter C developed in-house by ABMA.
**** Bossart and his
colleagues at General Dynamics staged a demonstration in an
attempt to show engineers from ABMA the toughness of the thin-wall
tanks. They pressurized a discarded Atlas tank and invited one of
the engineers to knock a hole in it with a sledge hammer. The blow
left the tank unharmed, but the fast rebounding hammer nearly
clobbered the wielder. In another instance, von Braun expressed
his attitude towards the tanks during a good-natured exchange on
using the Atlas for Project Mercury: "....John Glenn is going to
ride on that contraption? He should be getting a medal just for
setting on top of it before he takes off!" Interview with K. J.
Bossart, 27 Apr. 1974; group interview with Grant Hansen, K.E.
Newton, Deane Davis, Donald Heald, and Bossart, Convair Aerospace
Div., San Diego, 29 Apr. 1974.