The powerful Centaur upper stage allowed for heavier deep space probes, and for them to reach Jupiter sooner, prolonging the operational life of the spacecraft.

Support for the project came from the United States Air Force (USAF) and the National Reconnaissance Office, which asserted that its classified satellites required the power of Centaur.

[5] These challenges dogged the development of Centaur with technical difficulties, such as fuel leaking through the welds, and the shrinking of the metal bulkhead when coming into sudden contact with the cryogenic temperatures of liquid hydrogen.

[12] 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.

[23] 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.

[26] To enhance reliability and reduce costs, the Galileo project's engineers decided to switch from a pressurized atmospheric entry probe to a vented one.

[28] By late 1979, delays in the Space Shuttle program pushed the launch date for Galileo back to 1984, when the planets would no longer be aligned so that a Mars slingshot would be sufficient to reach Jupiter.

Reagan was persuaded to revise his policy to permit a mixed fleet of ELVs and Space Shuttles,[37][38] and the USAF ordered ten Titan IV rockets in 1984.

[31] NASA historian T. A. Heppenheimer noted that in retrospect, "it was a mistake not to go with the Titan IIIE-Centaur",[39] given the delays and higher costs ultimately involved in using the Shuttle, but this was not apparent in 1984.

The Ulysses probe had the same initial destination as Galileo, as it would first have to travel out to Jupiter and then use a slingshot maneuver to leave the ecliptic plane and enter a solar polar orbit.

One such change was to allow the Milstar to have a direct connection with Centaur that would be separated using explosive bolts, which required further testing to ascertain the effect of the resulting shock.

[46] At a press conference on 15 January 1981, Frosch announced that NASA was withdrawing support for the three-stage IUS and going with Centaur because "no other alternative upper stage is available on a reasonable schedule or with comparable costs.

[20] The decision to go with Centaur pleased planetary scientists and was welcomed by the communications industry, because it meant that larger satellites could be placed into geostationary orbits, whereas the Shuttle and IUS were limited to 3,000-kilogram (6,600 lb) payloads.

[36] On 30 August 1982, a meeting of representatives of the NASA centers and Centaur contractors was held at General Dynamics in San Diego to discuss the requirements of the project.

The engines were capable of multiple restarts after long periods of coasting in space and had a hydraulic gimbal actuation system powered by the turbopump.

The Centaur upper stage would then coast at a speed of 0.30 meters per second (1 ft/s) for 45 minutes before starting its main burn a safe distance from the Space Shuttle.

The committee enlisted Ohio Senator John Glenn and representatives Mary Rose Oakar, Howard Metzenbaum, Donald J. Pease, and Louis Stokes in their efforts to persuade Congress to keep the center open.

Frank Spurlock managed trajectory mission design, and Joe Nieberding took charge of the Shuttle-Centaur group within the Space Transportation Engineering Division.

[73] Larry Ross, the Director of Space Flight Systems at the Lewis Research Center,[75] had the logo emblazoned on project stationery and memorabilia like drink coasters and campaign buttons.

[80] The four-person crews would be the smallest since STS-6 in April 1983, and they would fly into a low 170-kilometer (110 mi) orbit, which was the highest that the Space Shuttle could achieve with a fully fueled Centaur on board.

The theme music from Star Wars was played, a crowd of 300, mostly General Dynamics employees, was in attendance, as were astronauts Fabian, Walker and Hauck, and speeches were given by dignitaries.

The USAF made its Shuttle Payload Integration Facility at the Cape Canaveral Air Force Station available in November and December so SC-1 and SC-2 could be processed at the same time.

Concerned that this was too few, Nieberding gave a presentation to key management officials in which he made the case to Moore for the Space Shuttle engines to be run at 109 percent.

[86] The main safety issue that concerned them involved what would happen in the case of an aborted mission, a failure of the Space Shuttle systems to put them into orbit.

[87] In such an emergency, all the propellant could be drained through valves on both sides of the Space Shuttle's fuselage in 250 seconds, but their proximity to the main engines and the Orbital Maneuvering System was a concern for the astronauts, who feared fuel leaks and explosions.

[80][81] Hauck and John Young, the astronaut who was chief of the Shuttle office, took their concerns to the Johnson Space Center Configuration Control Board, which ruled the risk acceptable.

Engineers continued to perform tests and the Galileo probe was moved to the Vertical Processing Facility at the Kennedy Space Center, where it was mated with Centaur.

[90] In May a series of meetings were held with NASA and aerospace industry engineers at the Lewis Research Center in which the safety issues around Centaur were discussed.

NASA management also considered the money and manpower required to get the Space Shuttle flying again and concluded that there were insufficient resources to resolve lingering problems with Shuttle-Centaur as well.

[94] Termination letters went out to the NASA centers and to the major contractors, including General Dynamics, Honeywell, Teledyne, and Pratt & Whitney, and over 200 stop-work orders were issued.