|Centaur Rocket Systems (1968-1974)|
Atlas Centaur Launch
Centaur was a 15000-pound thrust second-stage rocket designed for the military in 1957 and 1958 by General Dynamics. It was the first major rocket to use the liquid hydrogen technology developed by Lewis in the 1950s. Centaur suffered numerous problems before being transferred to Lewis in 1962. Lewis was able to rectify those problems, and Centaur performed key missions for Apollo. A second generation of Centaur was developed in the mid-1960s and would go on to have a long career. B-1 and B-3 were used to study Centaur’s boost pumps and shroud jettison system, respectively.
Centaur Program Overview (1963) (PDF, 1.00MB)
The Centaur Program was originally managed by Werner von Braun at the Army Ballistic Missile Agency which would become the NASA Marshall Space Flight Center. There was internal debate regarding the selection of the upper-stage for the new Saturn booster. A 1959 committee led by Abe Silverstein reviewed the options and concluded that a stage using high-energy propellants such as liquid hydrogen was the only solution. Von Braun was skeptical but approved their decision. Marshall was preoccupied with the Saturn booster and wary of Centaur’s unconventional design. Von Braun recommended cancelling the program before a single flight. The loss of the first launch in May 1962 only deepened his doubts.
Following congressional hearings and internal NASA deliberations, the Centaur Program was transferred to Lewis in September 1962. Silverstein was now the NASA Lewis Research Center Director and would personally oversee the program. Numerous test facilities at Lewis’ main campus and Plum Brook were built or modified specifically for Centaur. The rocket was put through an intensive 2-year checkout.
The next Centaur launch in November 1963 was a success. By the seventh launch in April 1966, Centaur’s initial problems had been resolved. On May 30, 1966 Centaur successfully sent the first Surveyor spacecraft on its way to the Moon. Three days later it became the first spacecraft to soft land on the Moon. Although the Surveyor flights completed Centaur’s primary mission, their success led to the planning of further launch assignments and upgraded versions of the rocket. This required additional tests and studies during the late-1960s and early-1970s at Lewis’ main campus and Plum Brook Station. B-1 and B-3 were involved in two of these.
|Advanced Centaur Tests|
B-1 During Tests
In August 1967 Plum Brook technicians began readying the B-1 test stand for to test the Centaur that November. The tests would focus on tank outflow and tank pressurization to determine if the boost pumps could be removed from the system. The series, referred to as the Advanced Centaur tests, were aimed at testing the next generation Centaur, the Centaur D. The studies obtained data on the pressurization and outflow of propellants from a “battleship type” Centaur tank. After months of preparation, a series of outflow tests were run from March to June 1968. In the fall of 1968 the second phase of testing focused on tank pressurization and a redesign of the propellant tank duct. The final series of tests in early 1969 analyzed a flight-type liquid hydrogen pressurization panel. The panel was chilled to simulate test conditions for future tests in the soon-to-be-completed B-2 facility.
The Advanced Centaur tests led to a redesign of the tank insulation that eventually became the standard for the Centaur D, a launch vehicle that performed 65 successful missions between 1966 and 1989. The tests were also an important early step in the eventual elimination of the boost pumps from the Centaur feed system. Followup full-scale tests in the B-2 facility led to the eventual removal of the boost pumps from the design. This produced a less complicated system and significantly reduced the cost of a Centaur rocket.
|Shroud Jettison Tests|
CSS in B-3 Stand
In the late 1960s NASA engineers were planning the ambitious new Viking mission to send two rover vehicles to the surface of Mars. The $1 billion Viking Program was vital to NASA’s future. The Viking rover was the heaviest payload ever attempted in a launch and was over three times the weight of Atlas-Centaur’s previous heaviest payload. Consequently, NASA engineers sought a more powerful booster to mate the Centaur with the Titan III rocket. Concurrently, General Dynamics was in the process of introducing a new Centaur model for Titan—the D-1T. The biggest change for the D-1T was a completely new shroud designed by Lockheed, called the Centaur Standard Shroud (CSS).
The conical two-piece covering encapsulated the payload to protect it against adverse conditions and improve the aerodynamics as the launch vehicle passed through the atmosphere. Once at the edge of space, the shroud would be jettisoned. Even a minor error in the jettison system could result in a launch failure. Lockheed was looking to test the jettison system for its new CSS before the launch. The shroud, its insulation, the Centaur ground-hold purge system, and the hydrogen tank venting system would all be studied in B-3.
After more than two years of preparations, the tests were run between April and July 1973. Structural load tests determined the ultimate flight loads on two axes, established the Centaur load sharing, and combined spacecraft loads with the CSS. The next series was run at cryogenic temperatures. These included determining the level of propellant boiloff during launch holds, verifying the vent system capacity, and conducting unlatch tests to ensure separation, and determining separation loads, and clearances. The final series included jettison tests run both at sea level and simulated altitude. Follow-up proof tests were run in early 1974.
The CSS performed flawlessly during the August 20 and September 9, 1975 launches. Each spacecraft took over 300 days to reach Mars. The missions were huge successes. Viking 1 and 2 operated on the Martian surface until November 1982 and April 1980, respectively. With Surveyor and Viking, Centaur had helped launch the first vehicles to soft land on the Moon and Mars.
Shroud Passes Cryo Tests (1973) (PDF, 883KB)
CSS Cryogenic Unlatch Tests NASA TM X-71455 (PDF, 13.7MB)
Centaur Standard Shroud articles (1972) (PDF, 1.29MB)