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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Shuttle-Centaur | 2/9 | https://en.wikipedia.org/wiki/Shuttle-Centaur | reference | science, encyclopedia | 2026-05-05T13:20:55.194283+00:00 | kb-cron |
=== Space Shuttle upper stages === The 1972 decision to develop the Space Shuttle augured badly for the projects to explore the Solar System with robotic probes, which were coming under intense scrutiny by an increasingly cost-conscious Nixon administration and United States Congress. The Space Shuttle was never intended to operate beyond low Earth orbit, but many satellites needed to be higher, particularly communications satellites, for which geostationary orbits were preferred. The Space Shuttle concept originally called for a crewed space tug, which would be launched by a Saturn V. It would use a space station as a base and be serviced and refueled by the Space Shuttle. Budget cutbacks led to the decision to terminate Saturn V production in 1970 and the abandoning of plans to build a space station. The space tug became an upper stage, to be carried into space by the Space Shuttle. As a hedge against further cutbacks or technical difficulties, NASA also commissioned studies of reusable Agena and Centaur upper stages. With funding tight, NASA sought to offload Space Shuttle-related projects onto other organizations. NASA Deputy Administrator George Low met with Malcolm R. Currie, the Director of Defense Research and Engineering, in September 1973, and reached an informal agreement that the USAF would develop an interim upper stage (IUS) for the Space Shuttle, to be used for launching satellites in higher orbits pending the development of the space tug. After some debate, Pentagon officials agreed to commit to the IUS on 11 July 1974. The Secretary of Defense, James R. Schlesinger, confirmed the decision when he met with NASA Administrator James C. Fletcher and Low four days later. A series of study contracts were let, resulting in a decision that the IUS would be an expendable solid-fuel upper stage. A call for bids was then issued, and the competition was won by Boeing in August 1976. The IUS was renamed the Inertial Upper Stage in December 1977. The Marshall Space Flight Center was designated the lead center for managing IUS work. In April 1978, the quote for the development of the IUS was $263 million (equivalent to $990 million in 2024), but by December 1979 it was renegotiated for $430 million (equivalent to $1495 million in 2024). The main drawback of the IUS was that it was not powerful enough to launch a payload to Jupiter without resorting to gravitational slingshot maneuvers around other planets to garner more speed, something most engineers regarded as inelegant, and which planetary scientists at NASA's Jet Propulsion Laboratory (JPL) disliked because it meant that the mission would take months or years longer to reach Jupiter. The IUS was constructed in a modular fashion, with two stages: a large one with 9,700 kilograms (21,400 lb) of propellant and a smaller one with 2,700 kilograms (6,000 lb), which was sufficient for most satellites. It could also be configured with two large stages to launch multiple satellites. The USAF asked NASA to develop a configuration with three stages, two large and one small, that could be used for a planetary mission like Galileo. NASA contracted with Boeing for its development.
=== Deep space probes === Congress approved funding for the Jupiter Orbiter Probe on 12 July 1977. The following year the spacecraft was renamed Galileo after Galileo Galilei, the 17th-century astronomer who had discovered the largest four of Jupiter's moons, now known as the Galilean moons. During the early 1980s, Galileo struggled with both technical and funding difficulties, and the Office of Management and Budget (OMB) targeted NASA for budget cuts. The intervention of the USAF saved Galileo from cancellation. It was interested in the development of autonomous spacecraft like Galileo that could take evasive action in the face of anti-satellite weapons, and in the manner in which the JPL was designing Galileo to withstand the intense radiation of the magnetosphere of Jupiter, which had application in surviving nearby nuclear detonations. The Galileo project aimed for a launch window in January 1982 when the alignment of the planets would be favorable to using Mars for a slingshot maneuver to reach Jupiter. Galileo would be the fifth spacecraft to visit Jupiter, and the first to orbit it, while the probe it carried would be the first to enter its atmosphere. In December 1984, Galileo project manager John R. Casani proposed that Galileo make a flyby of asteroid 29 Amphitrite while en route. It would be the first time a US space mission visited an asteroid. NASA Administrator James M. Beggs endorsed the proposal as a secondary objective for Galileo.