Shuttle-Centaur

Shuttle-Centaur was a proposed Space Shuttle upper stage using the Centaur upper stage rocket. Two variants were produced: Centaur G-Prime, which was planned to launch the Galileo and Ulysses robotic probes to Jupiter, and Centaur G, a shortened version planned for use with United States Department of Defense Milstar satellites and the Magellan Venus probe. The use of the powerful Centaur upper stage allowed for heavier deep space probes, and for them to reach Jupiter sooner, thus saving on battery life and wear and tear to the spacecraft. Support for the project came from the United States Air Force (USAF) and the National Reconnaissance Office (NRO), which asserted that its classified satellites required the power of Centaur. The USAF agreed to pay half the cost of Centaur G.

Main article: Centaur (rocket stage)

Centaur G and G-Prime
Illustration of Shuttle-Centaur G-Prime with Ulysses
ManufacturerGeneral Dynamics
Country of originUnited States
Centaur G-Prime
Length9.3 m (31 ft)
Diameter4.6 m (15 ft)
Empty mass2,761 kg (6,088 lb)
Gross mass22,800 kg (50,270 lb)
Engines2 x RL10-3-3A
Thrust73.40 kN (16,500 lbf) (per engine)
Specific impulse446.4 s
FuelLiquid hydrogen / LOX
Centaur G
Length6.1 m (20 ft)
Diameter4.6 m (15 ft)
Empty mass3,060 kg (6,750 lb)
Gross mass16,928 kg (37,319 lb)
Engines2 x RL10-3-3B
Thrust66.80 kN (15,020 lbf) (per engine)
Specific impulse440.4 s
FuelLiquid hydrogen / LOX

Both versions were cradled in the reusable Centaur integrated support system (CISS), an aluminum structure that handled communications between the Space Shuttle and the Centaur. The Space Shuttle Challenger and Space Shuttle Atlantis were modified to carry the CISS. The Centaur periodically vented hydrogen, which needs to be stored below −253 °C (−423 °F) to keep it from evaporating or boiling. Modifications were made to the Centaur and the Space Shuttle to permit venting and to allow the fuel to be dumped in the event of an emergency.

After the Space Shuttle Challenger accident, and just months before the Shuttle-Centaur had been scheduled to fly, NASA concluded that it was far too risky to fly the Centaur on the Shuttle. The Galileo and Ulysess probes were ultimately launched using the much less powerful solid-fueled Inertial Upper Stage (IUS), with Galileo needing multiple gravitational assists from Venus and Earth to reach Jupiter. The USAF mated a variant of the Centaur G Prime upper stage with the Titan rocket to produce the Titan IV, which made its first flight in 1994. Over the next 18 years, Titan IV and Centaur G Prime placed eighteen military satellites in orbit.

Background

Centaur

Centaur was developed in the late 1950s and early 1960s as an upper stage rocket using liquid hydrogen as a fuel and liquid oxygen as an oxidiser.[1] A rocket utilizing liquid hydrogen as a rocket fuel can theoretically lift 40 percent more payload per kilogram of liftoff weight than one with a conventional rocket fuel like kerosene. This was an attractive prospect in the early days of the Space Race, but to use liquid hydrogen, rocket engineers had to first overcome enormous technological challenges. Liquid hydrogen is a cryogenic fuel, meaning that it assumes liquid form only at extremely low temperatures and therefore must be stored below −253 °C (−423 °F) to keep it from evaporating or boiling. It must therefore be carefully insulated from all sources of heat, particularly the rocket exhaust, atmospheric friction during flight through the atmosphere at high speeds and the radiant heat of the Sun.[2] The tiny molecules of hydrogen can leak through microscopic holes.[3]

A Titan IIIE-Centaur rocket launches Voyager 2

Designed and built by General Dynamics, Centaur was powered by twin Pratt & Whitney RL10 engines.[4] It adopted the weight-saving features pioneered by the Atlas rocket family: a monocoque steel shell that held its shape only when pressurized, with the hydrogen and oxygen tanks separated by a common bulkhead; there was no internal bracing and no insulation surrounding the propellants.[5] The development of Centaur was dogged by technical difficulties: liquid hydrogen leaked through the welds, the metal bulkhead wrinkled under the shock of coming into sudden contact with something as cold as liquid hydrogen, and thew of the RL-10 engine exploded on the test stand.[6] In October 1962 NASA Headquarters transferred management of the project from NASA's Marshall Space Flight Center to its Lewis Research Center in Ohio. The technical problems were overcome. The development of technology for handling liquid hydrogen in Centaur paved the way for its use in the upper stages of the Saturn V Moon rocket and later by the Space Shuttle.[7]

Centaur upper stages were used in Atlas-Centaur rockets by the Surveyor program in the 1960s, which sent robotic spacecraft to the Moon,[1] and in the late 1960s and 1970s by the Mariner missions to Mercury, Venus and Mars; the Pioneer 10 and Pioneer 11 probes to Jupiter and Saturn; and the Pioneer Venus project.[8] In the 1970s, Centaur was placed atop the United States Air Force (USAF) Titan III booster to create the Titan III-Centaur launch vehicle system that was used for seven missions in the 1970s, including the Viking missions to Mars, Helios probes to the Sun, and the Voyager probes to Jupiter and the outer planets.[9] By 1980, Centaur had recorded 53 successful missions against two failures.[10]

When the Titan III-Centaur was rolled out for the first time in 1973, it was viewed as the last of the expendable launch vehicles. John Noble Wilford from The New York Times wrote that it was "expected to be the last new launching vehicle to be developed by the National Aeronautics and Space Administration until the advent of the reusable Space Shuttle which should be ready in 1978."[11] When the USAF questioned NASA's determination that all US space launches, civil and military, should use the Space Shuttle, NASA Administrator James M. Beggs insisted that expendable launch vehicles were obsolete, and that any money spent on them would only undermine the Space Shuttle's cost-effectiveness. Nonetheless, the USAF ordered ten Titan IV rockets in 1984.[12]

Space Shuttle upper stages

The decision to use the Space Shuttle for all launches augured badly for the projects to explore the Solar System with unmanned probes, which were coming under intense scrutiny by an increasingly cost-conscious United States Congress.[13] The Space Shuttle was never intended to operate beyond low Earth orbit, but many satellites needed to be in higher orbits, 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 in the early 1970s led to the termination of Saturn V production 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.[14]

With funding tight, NASA sought to offload Space Shuttle-related projects onto other organisations. NASA Deputy Administrator George Low met with Malcolm R. Currie, the Director of Defense Research and Engineering, in September 1973, and raised the prospect of the USAF developing an interim upper stage (IUS) for the Space Shuttle, to be used pending the development of the Space Tug. They reached an informal agreement, which was endorsed by the Secretary of the Air Force, John L. McLucas, but opposed by Leonard Sullivan, the Assistant Secretary of Defense for Program Analysis and Evaluation, who contended that the Space Shuttle had no economic or other benefit to the United States Department of Defense (DoD). After some debate, the 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.[14] The Marshall Space Flight Center was designated the lead center for managing IUS work.[15]

In April 1978, the quote for the development of the IUS was $263 million (equivalent to $825 million in 2019), but by December 1979 it was renegotiated for $430 million (equivalent to $1246 million in 2019).[16] The main drawback of the IUS was that it was not powerful enough to launch a payload to Jupiter without resorting to using a series of gravitational slingshot maneuvers around planets to garner additional 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.[17][18] However, 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.[14] A configuration with three stages, two large and one small, would be enough for a planetary mission, so NASA contracted for the development of a three-stage IUS.[18]

Deep space probes

Congress approved funding for the Jupiter Orbiter Probe on 12 July 1977.[19] 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.[20] What saved Galileo from cancellation was the intervention of the USAF, which was interested in the development of autonomous spacecraft that could take evasive action in the face of anti-satellite weapons, and the manner in which the JPL was designing Galileo to withstand the intense radiation of the magnetosphere of Jupiter, which had had application in surviving nearby nuclear detonations.[21] 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.[22] It was hoped that the Galileo spacecraft would be able to make a flyby of asteroid 29 Amphitrite while en route. 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.[23]

Artist's impression of the Galileo spacecraft in orbit around Jupiter

To enhance reliability and reduce costs, the Galileo project's engineers decided to switch from a pressurized atmospheric entry probe to a vented one. This added 100 kilograms (220 lb) to its weight, and another 165 kilograms (364 lb) was added in structural changes to improve reliability, all of which would require additional fuel in the IUS.[24] But the three-stage IUS was itself overweight, by about 3,200 kilograms (7,000 lb) against its design specifications.[22] Lifting Galileo and the IUS would require the use of the special lightweight version of the Space Shuttle external tank, the Space Shuttle orbiter stripped of all non-essential equipment, and the Space Shuttle main engines (SSME) running at full power—109 percent of their rated power level.[18] Running at this power level necessitated the development of a more elaborate engine cooling system.[25] By late 1979, delays in the Space Shuttle program pushed the launch date for Galileo back to 1984, when a Mars slingshot would no longer be sufficient to reach Jupiter.[26]

An alternative to the IUS was to use Centaur as an upper stage with the Space Shuttle. Shuttle-Centaur would require neither 109 percent power from the SSME, nor a slingshot maneuver to send the 2,000 kilograms (4,500 lb) to Jupiter.[22] In 1979, NASA's Associate Administrator for Space Transportation Systems, John Yardley, directed the Lewis Research Center to determine the feasibility of integrating Centaur with the Space Shuttle. The engineers at Lewis concluded that it was both feasible and safe.[27] A source inside NASA told The Washington Post journalist Thomas O'Toole that while it would cost money to modify Centaur so it could be carried on the Space Shuttle, it would be worth it, as the performance benefit of Centaur would mean that Galileo was no longer tied to a 1982 launch window.[22]

A third possibility considered was to launch Galileo using a Centaur upper stage atop a Titan IIIE, but this would have added at least $125 million (equivalent to $362 million in 2019) to the price of the $285 million (equivalent to $826 million in 2019) Galileo project because it would have required rebuilding the launch complex at Cape Canaveral.[22] In retrospect, this would have been the best way forward, but this was not apparent in 1979,[18] when there was a conviction at NASA that expendable launch vehicles were obsolete, and a national policy was in place that all launches should use the Space Shuttle. Moreover, Titan had been developed by, and was owned and controlled by, the USAF, and its use would mean that NASA would have to work closely with the USAF, something that NASA management hoped to minimise.[28] While NASA and the USAF collaborated and depended on each other to some extent, they were also rivals, and NASA resisted attempts by DoD to manage the space program.[29]

Although Galileo was the only American planetary mission scheduled, there was another mission on the cards: the International Solar Polar Mission, which was renamed Ulysses in 1984.[30] It was originally conceived in 1977 as a two-spacecraft mission, with NASA and the European Space Agency (ESA) each providing one spacecraft, but the American one was canceled in 1981, and NASA's contribution was limited to the power supply, launch vehicle, and tracking via the NASA Deep Space Network.[31] The object of the mission was to gain an enhanced knowledge of the heliosphere by putting a satellite into a polar orbit around the Sun. Because Earth's orbit is inclined only 7.25 degrees to the Sun's equator, the solar poles cannot be observed from Earth.[31] Scientists hoped to gain a greater understanding of the solar wind, the interplanetary magnetic field, cosmic rays and cosmic dust. It was never intended to make a close approach to the Sun. 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.[32]

Another mission for Shuttle-Centaur subsequently appeared in the form of the Venus Radar Mapper, later renamed Magellan. The first mission integration panel meeting for this probe was held at the Lewis Research Center on 8 November 1983. Various Space Shuttle upper stages were considered, including the Orbital Sciences Corporation Transfer Orbit Stage (TOS), the Astrotech Corporation Delta Transfer Stage, and the Boeing IUS, but Centaur was chosen as the best option. Magellan was tentatively scheduled for launch in April 1988.[33] The USAF adopted Shuttle-Centaur in 1984 for the launch of its Milstar satellites. These military communications satellites were hardened against interception, jamming and nuclear attack. Telephone conversations with General Dynamics regarding the project had to be conducted over secure phone lines. Having the USAF on board had saved the project from cancellation, but the USAF asked for design changes and performance enhancements. One such change was to allow the Milstar to have a direct connection with Centaur that would be separated using explosive bolts. This required additional testing to determine what the effects of this would be.[33]

Decision to use Shuttle-Centaur

NASA Administrator Robert A. Frosch stated in November 1979 that he was not in favor of using Centaur, but Centaur found a champion in Congressman Edward P. Boland, who considered the IUS too underpowered for deep space missions, although he did not oppose its development for other purposes. He was impressed by Centaur's ability to put Galileo in Jupiter orbit with just two years' flight and saw potential military applications for it as well. He chaired the House Intelligence Committee and the House Independent Agencies Appropriations Subcommittee of the House Appropriations Committee, and he got the Appropriations Committee to instruct NASA to use Centaur if weight problems with Galileo prompted a further postponement. Orders from a Congressional committee had no legal standing, so NASA was free to disregard it. Appearing before the Senate a few days later, Frosch was non-committal, saying only that NASA had the matter under consideration.[34]

Galileo spacecraft at the Kennedy Space Center's (KSC's) Spacecraft Assembly and Encapsulation Facility 2 in 1989

Instead, NASA decided to split Galileo into two separate spacecraft, an atmospheric probe and a Jupiter orbiter, with the orbiter launched in February 1984 and the probe following a month later. The orbiter would be in orbit around Jupiter when the probe arrived, allowing it to perform its role as a relay. Separating the two spacecraft was estimated to cost an additional $50 million (equivalent to $145 million in 2019),[35] but NASA hoped to be able to recoup some of this through separate competitive bidding on the two. The problem was that while the atmospheric probe was light enough to launch with the two-stage IUS, the Jupiter orbiter was too heavy to do so, even with a gravity assist from Mars, so the three-stage IUS was still required.[26]

By late 1980, the estimated cost of the development of the two-stage IUS had risen to $506 million (equivalent to $1345 million in 2019).[14] The USAF could absorb this cost overrun (and indeed had anticipated that it might cost far more), but NASA was faced with a quote of $179 million (equivalent to $435 million in 2019) for the development of the three-stage version,[18] which was $100 million (equivalent to $243 million in 2019) more than it had budgeted for.[36] 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."[37]

The Lewis Research Center pointed out that Centaur provided four advantages over the IUS. The main one was that it was far more powerful. The Galileo probe and orbiter could be recombined and the probe could be delivered directly to Jupiter in two years' flight time.[18][17] Longer travel times meant that components would age and the onboard power supply and propellant would be depleted.[38] The radioisotope thermoelectric generators (RTGs) on Ulysses and Galileo produced about 570 watts at launch, which decreased at the rate of 0.6 watts per month.[39] Some of the gravity assist options also involved flying closer to the Sun, which would induce thermal stresses.[38]

The second was that while it was more powerful, Centaur generated its thrust more slowly, thereby minimizing jerk and the chance of damage to the payload. Thirdly, unlike solid-fuel rockets, which burned to completion once ignited, Centaur could be switched off and on again. This gave it flexibility in the form of mid-course corrections and multi-burn flight profiles, which increased the chances of a successful mission. Finally, Centaur was proven and reliable. The only concern was about safety; solid-fuel rockets were considered far safer than liquid-fuel ones, especially ones containing liquid hydrogen.[18][17] NASA engineers estimated that additional safety features might take up to five years to develop and cost up to $100 million (equivalent to $243 million in 2019).[36][35]

The IUS made its first flight atop a Titan 34D in October 1982, when it placed two military satellites in geosynchronous orbit.[16] It was then used on a Space Shuttle mission, STS-6 in April 1983, to deploy the first Tracking and Data Relay Satellite (TDRS-1),[40] but the IUS's nozzle changed its position by one degree, resulting in the satellite being placed in the wrong orbit. It took two years to determine what had gone wrong and how to prevent it happening again.[41]

Congressional approval

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. NASA Headquarters liked Shuttle-Centaur as an answer to the ESA's Ariane rocket family; by 1986, new versions of the Ariane under development were expected to be able to lift payloads heavier than 3,000 kilograms (6,600 lb) into geostationary orbits, thereby cutting NASA out of a lucrative segment of the satellite launch business. And the USAF, while disappointed with NASA's decision to drop the three-stage IUS, foresaw a need for USAF satellites to carry more propellant than hitherto in order to engage in avoidance maneuvers against anti-satellite weapons.[42]

Two groups in particular were unhappy with the decision: Boeing and the Marshall Space Flight Center.[43] Other aerospace companies were disappointed that NASA had decided to adapt the existing Centaur upper stage rather than develop a new high energy upper stage (HEUS) or the orbital transfer vehicle (OTV), as the space tug was now called. The OMB was not opposed to Centaur on any technical grounds, but it was a discretionary expense and in the budget-cutting atmosphere of 1981, one that the OMB felt could be dropped for the fiscal year 1983 budget, which was submitted to Congress in February 1982. Gallileo was reconfigured for a 1985 launch using the two-stage IUS, which would take four years to get to Jupiter and reduce the number of moons visited by half when it got there.[44]

Senator Harrison Schmitt, the Chairman of the Senate Subcommittee on Science, Technology and Space,[42] and a former astronaut who had walked on the Moon on Apollo 17,[45] was opposed to the OMB decision, as were the House and Senate Appropriations Committees, but Congressman Ronnie G. Flippo, whose district in Alabama encompassed the Marshall Space Flight Center, was the Chairman of the House Subcommittee on Science, Technology and Space, and he supported the OMB decision. In July 1982, the proponents of Centaur added $140 million (equivalent to $320 million in 2019) to the Emergency Supplemental Appropriations Act, which was signed into law by President Ronald Reagan on 18 July 1982. In addition to the funding, it directed NASA and Boeing to cease work on the two stage IUS for Galileo.[42]

Flippo fought this decision. He argued that Centaur was too expensive, as it cost $140 million in the current year with the whole Shuttle-Centaur project estimated to cost around $634 million (equivalent to $1450 million in 2019); that it was of limited use, since it was only required for two deep space missions; and that it was a prime example of faulty procurement, because an important contract was being given to General Dynamics without any form of tender process. He enlisted the support of Congressman Don Fuqua, the Chairman of the House Committee on Science, Space and Technology. Centaur was defended by Congressman Bill Lowery, whose San Diego district included General Dynamics.[44]

On 15 September, Flippo moved an amendment to the 1983 NASA appropriations bill that would have forbidden further work on Centaur, but his position was undermined by Edward C. Aldridge Jr.,[46] the Under Secretary of the Air Force (and Director of the National Reconnaissance Office),[47] and NASA Administrator James M. Beggs, who contended that contamination observed during early Space Shuttle flights meant that more shielding would be required for classified Defense satellites, which would add more weight and therefore require the power of Centaur. Aldridge and Beggs announced that they would soon conclude an agreement for the joint development of Shuttle-Centaur. Flippo's amendment was defeated by a vote of 316 to 77, clearing the way for the Shuttle-Centaur project.[46]

Design
Shuttle-Centaur system

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. From this arose two new versions of Centaur: Centaur G and Centaur G Prime. The principal constraint was that they had to fit inside the Space Shuttle's 18-meter (60 ft) cargo bay. This restricted the width to 4.6 meters (15 ft). Centaur G was intended for USAF missions, specifically to place satellites into geostationary orbits, and the $269 million (equivalent to $615 million in 2019) to design and develop it were split 50–50 with the USAF. It was 6.1 meters (20 ft) long, allowing for large USAF payloads up to 12.2 meters (40 ft) long. Its dry weight was 3,060 kilograms (6,750 lb) and it weighed 16,928 kilograms (37,319 lb) fully loaded. Centaur G Prime was intended for deep space missions and was 9.0 meters (29.5 ft) long, allowing it to carry more propellant, but restricting the length of the payload to 9.3 meters (31 ft). The dry weight of the Centaur G Prime was 2,761 kilograms (6,088 lb), and it weighed 22,800 kilograms (50,270 lb) fully loaded.

The two versions were very similar, with 80 percent of their components being the same. The Centaur G Prime stage had two RL10-3-3A engines, each with 73,400 newtons (16,500 lbf) thrust, and a specific impulse of 446.4 seconds, with a 5:1 fuel ratio. The Centaur G stage had two RL10-3-3B engines, each with 66,700 newtons (15,000 lbf) thrust, and specific impulse of 440.4 seconds, with a 6:1 fuel ratio. 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.[48][49][50]

Centaur G and G Prime configurations

The Centaur G and G Prime avionics were the same as that of the standard Centaur and were still mounted in the forward equipment module. It used a 24-bit Teledyne Digital Computer Unit with 16 kilobytes of RAM to control guidance and navigation. It still used the same pressurized steel tank, but with some additional insulation including a two-layer foam blanket over the forward bulkhead and a three-layer radiation shield.[48] Other changes included new forward and aft adapters; a new propellant fill, drain and dump system; and an S band transmitter and RF system compatible with the tracking and data relay satellite system.[51] Considerable effort was put into making the Centaur safe, with redundant components to overcome malfunctions and a propellant draining, dumping and venting system so that the propellants could be dumped in case of emergency.[52]

Both versions were cradled in the Centaur integrated support system (CISS), a 4.6 meters (15 ft) aluminum structure that handled communications between the Space Shuttle and the Centaur upper stage. It helped keep the number of modifications to the Space Shuttle to a minimum. When the cargo doors opened, the CISS would pivot 45 degrees into a ready position to launch Centaur. After twenty minutes, the Centaur would be launched by a set of twelve coil springs with a 10-centimeter (4 in) stroke known as the Super*Zip separation ring. 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. For most missions, only a single burn was required. Once the burn was complete, the spacecraft would separate from the Centaur upper stage, which could still maneuver to avoid striking the spacecraft.[52][53]

Centaur G Prime in the CISS (right)

All electrical connections between the Orbiter and the Centaur were routed through the CISS. Electrical power for the Centaur was provided by a 150-ampere-hour (540,000 C) silver zinc battery. Power for the CISS was provided by two 375-ampere-hour (1,350,000 C) batteries. Since the CISS was also plugged into the Orbiter, this provided two-failure redundancy.[54] The Centaur G CISS weighed 2,947 kilograms (6,497 lb) and the Centaur G Prime CISS 2,961 kilograms (6,528 lb).[50] The CISS was fully reusable for ten flights and would be returned to Earth. The Space Shuttle Challenger and Space Shuttle Atlantis were modified to carry the CISS.[52][51]

By June 1981, the Lewis Research Center had awarded four contracts for Centaur G Prime worth a total of $7,483,000 (equivalent to $17.1 million in 2019): General Dynamics was to develop the Centaur rockets; Teledyne, the computer and multiplexers; Honeywell, the guidance and navigation systems; and Pratt & Whitney, the four RL10A-3-3A engines.[55]

Management

Christopher C. Kraft Jr., William R. Lucas, and Richard G. Smith, the directors of the Johnson Space Center, Marshall Space Flight Center and Kennedy Space Center respectively, did not like NASA Headquarters' decision to assign Shuttle-Centaur to the Lewis Research Center. In a January 1981 letter to Alan M. Lovelace, the acting Administrator of NASA, they argued that management of the Shuttle-Centaur project should instead be assigned to the Marshall Space Flight Center, which had some experience with cryogenic propellants and more experience with the Space Shuttle, which the three directors regarded as a complex system that only their centers understood.[56]

Engineers at the Lewis Research Center saw matters differently. The director of the Lewis Research Center, John F. McCarthy Jr., wrote to Lovelace in March, providing reasons why the Lewis Research Center was the best choice: it had led the project to evaluate the feasibility of mating the Space Shuttle with Centaur; its experience with Centaur was the greatest of all the NASA centers; it had managed the successful Titan-Centaur project; had experience with space probes with the Surveyor, Viking and Voyager projects; and it boasted a highly skilled workforce where the average engineer had thirteen years of experience. In May 1981, Lovelace informed Lucas of his decision to have the Lewis Research Center manage the project.[56] In November 1982, Andrew Stofan, the director of the Lewis Research Center, and Lew Allen, the director of the JPL, signed a Memorandum of Agreement on the Galileo project; JPL was responsible for the design and management of the mission, and the Lewis Research Center for integrating the Galileo spacecraft with the Centaur and the Space Shuttle.[57]

Shuttle-Centaur project logo.

The future of the Lewis Research Center was uncertain in the 1970s and early 1980s. The cancellation of the NERVA nuclear rocket engine had caused a round of layoffs in the 1970s, and many of the more experienced engineers had elected to retire.[58] Between 1971 and 1981, staff numbers fell from 4,200 to 2,690. In 1982, the staff became aware that the Reagan administration was considering closing the center, and they mounted a vigorous campaign to save it. The staff formed a committee to save the center, and began lobbying Congress. The committee enlisted Ohio Senator John Glenn and Congressmen Mary Rose Oakar, Howard Metzenbaum, Donald J. Pease, and Louis Stokes in their efforts to persuade Congress to keep the center open.[59]

McCarthy retired in July 1982, and Andrew Stofan became the director of the Lewis Research Center. He was an associate administrator at NASA Headquarters, whose involvement with Centaur dated back to 1962 and who had headed the Atlas-Centaur and Titan-Centaur Offices in the 1970s.[60][61] Under Stofan, the Lewis Research Center budget steadily increased, from $133 million (equivalent to $385 million in 2019) to $159 million (equivalent to $338 million in 2019) and $188 million (equivalent to $387 million in 2019) in 1985. This permitted an increase in staff for the first time in 20 years, with 190 new engineers hired in 1983.[55] In the process, the Lewis Research enter drifted away from fundamental research and became involved in the management of major projects like Shuttle-Centaur.[59]

William H. Robbins was appointed the head of the Shuttle-Center Project Office at the Lewis Research Center. Most of his experience was with NERVA, and this was his first experience with Centaur, but he was an experienced project manager. He handled the project's administration and financial arrangements.[62] Vernon Weyers was his deputy. USAF Major William Files also became a deputy project manager. He brought with him six USAF officers who assumed key roles in the Project Office.[63] Marty Winkler headed the Shuttle-Centaur program at General Dynamics.[64] Steven V. Szabo, who had worked on Centaur since 1963, was head of the Lewis Research Center's Space Transportation Engineering Division. He was responsible for the technical side of the activities related to the integration of the Space Shuttle and Centaur, which included the propulsion, pressurization, structural, electrical, guidance, control and telemetry systems. Within the Shuttle-Centaur Project Office, Edwin Muckley was in charge of the Mission Integration Office, which was responsible for the payloads. Frank Spurlock managed trajectory mission design, and Joe Nieberding took charge of the Shuttle-Centaur group within the Space Transportation Engineering Division. Spurlock and Nieberding hired many young engineers, giving the Shuttle-Centaur project a mixture of youth and experience.[62]

Shuttle-Centaur project organization

The Shuttle-Centaur Project had to be ready to launch in May 1986, which was just three years away. The cost of a delay was estimated at $50 million (equivalent to $101 million in 2019).[64] Failure to meet the deadline meant waiting another year until the planets were properly aligned again.[65] The project adopted a mission logo depicting a mythical centaur emerging from the Space Shuttle and firing an arrow at the stars.[64] Larry Ross, the Director of Space Flight Systems at the Lewis Research Center,[66] had the logo emblazoned on project stationery and memorabilia like drink coasters and campaign buttons. A special Shuttle-Centaur project calendar was produced, with 28 months on it, covering January 1984 to April 1986. The cover sported the logo, with the project motto, co-opted from the movie Rocky: "Go for it!"[64]

When it came to integrating Centaur with the Space Shuttle, there were two possible approaches: as an element or a payload. Elements were components of the Space Shuttle like the external tank and the solid rocket boosters; whereas a payload was something being carried into space like a satellite. The 1981 Memorandum of Agreement between the Johnson Space Center and the Lewis Research Center defined the Centaur as an element. At first, the engineers at the Lewis Research Center preferred to have it declared a payload, because time was short and this minimized the amount of interference in their work by the Johnson Space Center. Centaur was therefore declared to be a payload in 1983. Payload status was originally conceived as being for inert pieces of cargo. The Johnson Space Center added additional requirements for Centaur. Complying with the requirements of this status resulted in a series of safety waivers. Both centers wanted to make the Centaur as safe as possible, but differed over what trade offs were acceptable.[67]

Preparations
NASA Lewis Research Center director Andrew J. Stofan addresses the crowd at General Dynamics in San Diego at the rollout of SC-1.

Two Shuttle-Centaur missions were scheduled: STS-61-F for Ulysses in the Space Shuttle Challenger for 15 May 1986, and STS-61-G for Galileo in the Space Shuttle Atlantis for 20 May. Crews were assigned in May 1985: STS-61-F would be commanded by Frederick Hauck, with Roy D. Bridges Jr. as the pilot and mission specialists John M. Lounge and David C. Hilmers; STS-61-G would be commanded by David M. Walker, with Ronald J. Grabe as pilot and James Van Hoften and John M. Fabian, who was replaced by Norman Thagard in September, as mission specialists.[68][69][70] In addition to being the STS-61-F commander, Hauck was the Shuttle-Centaur project officer at the Astronaut Office. He and Walker attended key senior management project meetings, which was unusual for astronauts.[71]

The four-person crews would be the smallest since STS-6 in April 1983, and they would fly into a low 170 kilometers (110 mi) orbit, which was the highest that the Space Shuttle could achieve with a fully fueled Centaur on board. Payload deployments were not normally scheduled for the first day to allow for astronauts who came down with space adaptation syndrome. To avoid this, both crews were entirely composed of astronauts who had already flown in space at least once before so deployment could occur just seven hours after launch.[72]

The two launches would only have a one-hour launch window and there would be just six days between them. Because of this, two launch pads would be used: Launch Complex 39A for STS-61-G and Atlantis and Launch Complex 39B for STS-61-F and Challenger. The latter had only recently been refurbished to handle the Space Shuttle. The first Centaur G Prime, SC-1, was rolled out from the General Dynamics factory in Kearny Mesa, San Diego on 13 August 1985. 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.[73][72][74]

SC-1 was then flown to the Kennedy Space Center, where it was mated with CISS-1, which had arrived two months before. SC-2 and CISS-2 followed in November. 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. A problem was detected with the propellant level indicator in the oxygen tank in SC-1, which was promptly redesigned, fabricated, and installed. There was also a problem with the drain valves, which was found and corrected. Shuttle-Centaur was certified as flight ready by NASA Associate Administrator Jesse Moore.[74]

The main safety issue involved what would happen in the case of an aborted mission, a failure of the Space Shuttle systems to put them into orbit. In that case, they would have to dump the Centaur's propellant and land. This was an extremely dangerous maneuver under any circumstance, one that in fact would never occur in the life of the Space Shuttle program.[75] If the Space Shuttle orbiter had to return to Earth with Centaur still on board, its center of gravity would be further aft than on any previous mission. Centaur would periodically vent boiling hydrogen to maintain the proper internal pressure. In an emergency, all the propellant could be drained in 250 seconds through valves on both sides of the Space Shuttle's fuselage, but their proximity to the main engines and the Orbital Maneuvering System was a concern for the astronauts, who feared fuel leaks and explosions.[71][72] The astronauts considered the Shuttle-Centaur missions to be riskiest the Space Shuttle missions yet.[76]

Centaur G Prime arrives at the Shuttle Payload Integration Facility at the Kennedy Space Center

The Johnson Space Center committed to lifting 29,000 kilograms (65,000 lb) but the engineers at Lewis Research Center were aware that the Space Shuttle was unlikely to be able to lift that amount. To compensate, the Lewis Research Center reduced the amount of propellant in the Centaur. This limited the number of possible launch days to just six. Concerned that this was too few, Shuttle-Centaur group leader Joe Nieberding gave a presentation to key management officials in which he made the case for Moore the Space Shuttle engines to be run at 109 percent. Moore approved the request, over the objections of representatives of the Marshall Space Flight Center and Johnson Space Center who were present.[77]

The astronauts were concerned about this. Hauck and Young took their concerns to the Johnson Space Center Configuration Control Board, which ruled the risk acceptable.[78] Engineers at the Lewis Research Center, the JPL and General Dynamics dismissed the astronauts' concerns about liquid hydrogen, pointing out that the Space Shuttle was propelled by liquid hydrogen and at liftoff they had 25 times the Centaur's fuel in the Space Shuttle's external tank.[79]

On 28 January 1986, Challenger lifted off on STS-51-L. A failure of the solid rocket booster 73 seconds into flight tore Challenger apart, resulting in the deaths of all seven crew members.[80] The Space Shuttle Challenger disaster was America's worst space disaster up to that time.[78]

Cancellation

On 20 February, Moore ordered the Galileo and Ulyssess missions postponed. Too many key personnel were involved in the analysis of the accident for the missions to proceed. It was not canceled, but the earliest the missions could be flown was in thirteen months. 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 the Centaur.[81][82]

Of the four safety reviews required of the Shuttle-Centaur missions, three had been completed, although some issues arising from the last two remained to be resolved. The final review was originally scheduled for late January. Some additional safety changes had been incorporated into the Centaur Gs being built for the USAF, but had not made it to SC-1 and SC-2 owing to the strict deadline. After the disaster, $75 million (equivalent to $217 million in 2019) was earmarked for Centaur safety enhancements.[65]

Although completely unrelated to the accident, Challenger had broken up immediately after throttling to 104 percent power. This contributed to the perception at the Johnson Space Center and Marshall Space Flight Centers that it was too risky to go to 109 percent. At the same time, the engineers at Lewis were aware that safety improvements to the Space Shuttle were likely and that this could only add more weight. Without 109 percent power, it seemed unlikely that the Shuttle could lift Centaur.[81]

In May a series of meetings was held with NASA and aerospace industry engineers at the Lewis Research Center in which the safety issues around Centaur were discussed. The meeting concluded that Centaur was reliable and safe. At one meeting at NASA Headquarters on 22 May, though, Hauck argued that Centaur posed an unacceptable degree of risk. A review by the House Appropriations Committee chaired by Boland recommended that Shuttle-Centaur be canceled. On 19 June NASA Administrator James C. Fletcher terminated the project.[82][83][84]

This was only partly due to the NASA management's increased aversion to risk in the wake of the Challenger disaster. 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.[85] Stop work orders went out to the contractors. Most work was completed by 30 September, with all work done by the end of the year. Allowing work to continue to completion preserved the investment in technology. The USAF purchased the flight hardware from NASA for use with Titan.[86] About $700 million (equivalent to $1413 million in 2019) had been spent on Shuttle-Centaur.[87]

Legacy
Dedication ceremony at NASA Glenn for the Centaur G Prime display. Director Janet Kavandi is in the front row, in the blue skirt.

Galileo was not launched until 17 October 1989, on STS-34 using the IUS.[88] It took six years to reach Jupiter instead of two, as it had to fly by Venus and Earth twice to garner enough speed to reach Jupiter.[89][90] When the JPL tried to use its high gain antenna, it was found to have been damaged, most likely from vibration and the loss of lubricant during overland transportation between the JPL and Kennedy Space Center three times or during the rough launch by the IUS. A prolonged period of time in the vacuum of space followed where bare metal touching could undergo cold welding.[91][92][93]

The Ulysses project scientists had to wait even longer; the Ulysses spacecraft was launched using the IUS and Payload Assist Module on STS-41 on 6 October 1990.[31] The USAF mated the Centaur G Prime upper stage with the Titan booster to produce Titan IV, which made its first flight in 1994.[94] Over the next 18 years, Titan IV with Centaur G Prime placed eighteen military satellites in orbit.[95] In 1997 NASA used it to launch the Cassini–Huygens probe to Saturn.[94]

A Centaur G Prime was on display at the U.S. Space & Rocket Center in Huntsville, Alabama, for many years. In 2016, the center decided to move it to make way for a redesigned outdoor display, and it was transferred to NASA's Glenn Research Center. It was officially placed on outdoor display on 6 May 2016 after a ceremony attended by forty retired NASA and contractor staff who had worked on the rocket thirty years before, and by officials including Glenn Director Janet Kavandi, former Glenn Director Lawrence J. Ross, and the USAF's former Titan IV mission manager, Colonel Elena Oberg.[95][96][97]

Notes
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  2. Dawson 2002, p. 335.
  3. Dawson 2002, p. 346.
  4. Dawson 2002, pp. 340–342.
  5. Dawson 2002, p. 336.
  6. Dawson 2002, pp. 346–350.
  7. Dawson 2002, pp. 350–354.
  8. Dawson & Bowles 2004, pp. 116–123.
  9. Dawson & Bowles 2004, pp. 139–140.
  10. Meltzer 2007, p. 48.
  11. Wilford, John Noble (3 October 1973). "Test Rocket for Planetary Exploration Rolled Out". The New York Times. Retrieved 8 October 2020.
  12. Dawson & Bowles 2004, p. 232.
  13. Dawson & Bowles 2004, pp. 162–165.
  14. Heppenheimer 2002, pp. 330–335.
  15. Waldrop 1982, p. 1014.
  16. Heppenheimer 2002, p. 368.
  17. Bowles 2002, p. 420.
  18. Heppenheimer 2002, pp. 368–370.
  19. Meltzer 2007, pp. 35–36.
  20. Meltzer 2007, p. 38.
  21. Meltzer 2007, pp. 50–51.
  22. O'Toole, Thomas (11 August 1979). "More Hurdles Rise In Galileo Project To probe Jupiter". The Washington Post. Retrieved 11 October 2020.
  23. Dawson & Bowles 2004, pp. 190–191.
  24. Meltzer 2007, p. 41.
  25. Meltzer 2007, p. 42.
  26. Meltzer 2007, pp. 46–47.
  27. Dawson & Bowles 2004, p. 178.
  28. Dawson & Bowles 2004, pp. 193–194.
  29. Levine 1982, pp. 235–237.
  30. Bowles 2002, pp. 428–429.
  31. Wenzel et al. 1992, pp. 207–208.
  32. Dawson & Bowles 2004, pp. 191–192.
  33. Dawson & Bowles 2004, pp. 192–193.
  34. Meltzer 2007, pp. 45–46.
  35. O'Toole, Thomas (19 September 1979). "NASA Weighs Deferring 1982 Mission to Jupiter". The Washington Post. Retrieved 11 October 2020.
  36. Meltzer 2007, p. 43.
  37. Janson & Ritchie 1990, p. 250.
  38. Meltzer 2007, p. 82.
  39. Taylor, Cheung & Seo 2002, p. 86.
  40. "STS-6". NASA. Retrieved 11 October 2020.
  41. Dawson & Bowles 2004, p. 172.
  42. Waldrop 1982, p. 1013.
  43. Dawson & Bowles 2004, pp. 173–174.
  44. Waldrop 1982, pp. 1013–1014.
  45. "Biographical Data – Harrison Schmitt" (PDF). NASA. Retrieved 12 October 2020.
  46. Waldrop 1982a, p. 37.
  47. Field 2012, pp. 27–28.
  48. Dawson & Bowles 2004, pp. 184–185.
  49. Stofan 1984, p. 3.
  50. Kasper & Ring 1990, p. 5.
  51. Graham 2014, pp. 9–10.
  52. Dawson & Bowles 2004, pp. 185–186.
  53. Martin 1987, p. 331.
  54. Stofan 1984, p. 5.
  55. Dawson & Bowles 2004, pp. 180–181.
  56. Dawson & Bowles 2004, pp. 178–180.
  57. Dawson & Bowles 2004, p. 191.
  58. Dawson 1991, p. 201.
  59. Dawson 1991, pp. 212–213.
  60. Dawson & Bowles 2004, pp. 177–181.
  61. "Andrew J. Stofan". NASA. Retrieved 14 October 2020.
  62. Dawson & Bowles 2004, pp. 182–183.
  63. Dawson & Bowles 2004, p. 194.
  64. Dawson & Bowles 2004, pp. 195–196.
  65. Rogers 1986, pp. 176–177.
  66. Dawson & Bowles 2004, p. 179.
  67. Dawson & Bowles 2004, pp. 196–200.
  68. Hitt & Smith 2014, pp. 282–285.
  69. Nesbitt, Steve (31 May 1985). "NASA Names Flight Crews for Ulysses, Galileo Missions" (PDF) (Press release). NASA. 85-022. Retrieved 17 October 2020.
  70. Nesbitt, Steve (19 September 1985). "NASA Names Crews for Upcoming Space Flights" (PDF) (Press release). NASA. 85-035. Retrieved 17 October 2020.
  71. Dawson & Bowles 2004, pp. 203–204.
  72. Evans, Ben (7 May 2016). "Willing to Compromise: 30 Years Since the 'Death Star' Missions (Part 1)". AmericaSpace. Retrieved 18 October 2020.
  73. Norris, Michele L. (14 August 1985). "Centaur to Send Spacecraft to Jupiter, Sun : New Booster Rolled Out in San Diego". Los Angeles Times. Retrieved 18 October 2020.
  74. Dawson & Bowles 2004, pp. 204–206.
  75. "Aborts". NASA. Retrieved 18 October 2020.
  76. Hauck, Rick (20 November 2003). "Frederick H. Hauck Oral History Interview" (PDF) (Interview). NASA Johnson Space Center Oral History Project. NASA. Retrieved 6 January 2021.
  77. Dawson & Bowles 2004, p. 208.
  78. Dawson & Bowles 2004, pp. 206–207.
  79. Dawson & Bowles 2004, p. 197.
  80. Meltzer 2007, pp. 72–77.
  81. Dawson & Bowles 2004, pp. 207–208.
  82. Johnson 2018, pp. 140–142.
  83. Dawson & Bowles 2004, pp. 209–210.
  84. Fisher, James (20 June 1986). "NASA Bans Centaur from Shuttle". Orlando Sentinel. Retrieved 18 October 2020.
  85. Dawson & Bowles 2004, pp. 216–218.
  86. Dawson & Bowles 2004, p. 213–215.
  87. "NASA Drops Plans to Launch Rocket from the Shuttle". The New York Times. 20 June 1986. Retrieved 18 October 2020.
  88. Meltzer 2007, pp. 104–105.
  89. Meltzer 2007, pp. 82–84.
  90. Meltzer 2007, pp. 171–178.
  91. Meltzer 2007, pp. 182–183.
  92. Johnson 1994, pp. 372–377.
  93. Meltzer 2007, pp. 177-183.
  94. Dawson & Bowles 2004, p. 215.
  95. Cole, Michael (8 May 2020). "NASA Glenn dedicates display of historic Shuttle-Centaur booster". SpaceFlight Insider. Retrieved 7 October 2020.
  96. Rachul, Lori (3 May 2016). "NASA Glenn Dedicates Historic Centaur Rocket Display" (Press release). NASA. 16-012. Retrieved 20 October 2020.
  97. "Last existing Shuttle-Centaur rocket stage moving to Cleveland for display". collectSPACE. Retrieved 3 December 2020.

References
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