|Space Shuttle Mission-62: Discovery awaits the imminent arrival of its crew, August 1994. Image credit: NASA|
Carter's 1978 decision piqued the ire of spaceflight purists in a way that even the Sortie Lab decision of 1972 had not, for it turned the rationale for the Shuttle completely upside-down. The Shuttle had been conceived originally as crew rotation and resupply vehicle for a Saturn V-launched core Space Station. After President Richard Nixon refused to fund the core Station and scrapped the Saturn V, NASA studied a Shuttle-launched Station until it became clear that no Station would receive Nixon's blessing.
Deprived of its true purpose, the Shuttle Orbiter became a piloted spacecraft meant to replace all existing expendable space launch vehicles. It would, NASA promised, dramatically reduce the cost of spaceflight, ushering in a new age of space development. It would also reduce the cost of satellites by servicing them in orbit, serve as a short-term space laboratory by carrying in its Payload Bay a can-shaped Sortie Lab module, and make space readily accessible to non-astronauts.
The 1978 decision to turn the Shuttle into a robot spacecraft ceased to be controversial on the morning of 28 January 1986, when the Orbiter Challenger was destroyed a little more than a minute into Space Shuttle Mission (SSM) 25. Had astronauts been on board, they would have been unaware of the Solid Rocket Booster malfunction that was the root cause of Challenger's destruction. Had they somehow learned of the malfunction, they would have been unable to intervene and would have been trapped at least until the Shuttle stack's twin Solid Rocket Boosters had spent their propellant and detached. That would have been too long, for Challenger was destroyed as its Solid Rocket Boosters still burned.
As it was, Challenger's five-person crew for SSM-25 watched as the automated spacecraft they had been meant to board in orbit for a two-week stay was torn apart by aerodynamic forces and tumbled in fragments into the Atlantic. The Solid Rocket Boosters emerged still firing from the fireball created when the Shuttle's large, fragile External Tank broke up, spilling its liquid hydrogen and liquid oxygen propellants. The Solid Rocket Boosters each painted a twisting smoke-trail across the blue Florida sky until a Range Safety Officer sent the radio command that destroyed them.
As Challenger disintegrated, the Astronaut Transport Spacecraft (ATS) meant to launch the SSM-25 crew into orbit the following day stood atop a Saturn II expendable rocket on nearby Pad 39B. The ATS was an Apollo Command and Service Module spacecraft redesigned to carry five astronauts. The Saturn II rocket comprised the top two stages of the Saturn V - that is, the 33-foot-diameter S-II and 22-foot-diameter S-IVB. It included six uprated J-2 engines - five in its first stage and one in its second - and six small solid-rocket boosters evenly spaced around its base. Without an ATS on top, the Saturn II could launch a 20-ton payload.
After Challenger, some called for an end to unmanned Orbiter flights. They pointed out that the ATS/Saturn II combination included a sizable cargo volume in the tapered shroud that linked the base of the ATS with the top of the Saturn II S-IVB. They referred to early 1970s NASA and contractor studies that showed that increasing the number of solid-rocket boosters to 10 would permit the Saturn II to launch both the ATS and up to 20 tons of cargo .
President Carter, since his election in November 1984 the first President since Grover Cleveland to serve non-consecutive terms, surprised many by declaring his support for the Shuttle. This should perhaps not have come as a surprise, given that it had been Carter who made the 1978 decision to launch and land the Orbiter without a crew. The "come-back President" pointed to the Challenger accident as the vindication of his 1978 decision, and called for continued unmanned Orbiter flights on the grounds that upgrading the Saturn II would not replace all Shuttle capabilities. It is widely assumed that he also sought to continue the unmanned Orbiter flights to preserve the thousands of jobs the Shuttle Program had created.
In August 1986, Carter signed off on NASA's post-Challenger plan to redesign the SRBs and begin construction of two new Orbiters. This would increase the total number of Orbiters in the Shuttle fleet to four, enabling more downtime for inspections and upgrades between flights. To pay for the new Orbiters, Carter reduced the number of annual Orbiter flights to three from the six planned before Challenger was destroyed. As each new Orbiter came online, one additional flight per year would be added, so the four-orbiter fleet would eventually fly five missions per year.
In the meantime, the Hubble Space Telescope reached orbit in May 1986 atop a Saturn II without an ATS. Repairing its flawed optics became a goal for one of the first post-Challenger Shuttle missions. A Saturn II/Centaur launched the third Radio Relay and Tracking Satellite to geostationary orbit in July 1986, enabling for the first time continuous contact between orbiting spacecraft and flight controllers and researchers on the ground.
A Department of Defense-sponsored ATS solo mission designated SSM-X5 launched in December 1986 with a three-person crew to test polar-orbiting missions. (SSM-X1 through X4 had been Orbiter and ATS test missions in the 1980-1981 period.) Shortly after its return to Earth, new NASA Administrator Sally Ride announced that the Defense Department had opted to forego future Orbiter/ATS flights in favor of ATS solo flights.
The Shuttle Orbiter Enterprise soared into space in September 1987 to start the SSM-26 "Return-To-Flight" mission. Its five-person crew arrived in the SSM-26 ATS two days later. The astronauts spent three weeks on board Enterprise.
Columbia reached orbit in November 1987 to begin SSM-27; after its crew docked their ATS and boarded, they piloted the Orbiter to a rendezvous with the Hubble Space Telescope. Through a series of ambitious spacewalks, the astronauts corrected its faulty optics. They returned to Earth after 10 days in orbit. Columbia landed two days later.
Enterprise reached orbit the next time in May 1988 for SSM-29, but returned to Earth early after the Saturn II rocket bearing the SSM-29 ATS malfunctioned shortly after clearing Pad 39A's lightning mast. The ATS's Launch Escape System activated and pulled its Command Module free of the disintegrating Saturn II rocket. The five astronauts on board were uninjured. They would reach Enterprise to carry out SSM-29R in May 1989. The ATS/Saturn II combination had a flight record going back to the first Apollo Saturn V flight in November 1967, so troubleshooting the J-2 engine malfunction that destroyed the SSM-29 Saturn II and returning the system to flight needed only a few months.
The new Shuttle Orbiter Discovery flew an uncrewed orbital test mission (SSM-X6) in December 1989. In October 1991, the new Orbiter Endurance performed a nearly identical test mission (SSM-X7).
Endurance was the first Orbiter upgraded to permit a 12-week orbital stay and docking with two ATSs at one time. It carried out its first long-duration mission (SSM-60) and received two ATSs between mid-April 1994 and mid-July 1994.
Shortly after Columbia's retirement to the National Air and Space Museum in mid-1995, the new long-duration Orbiter Adventure joined the fleet. It would be the last Orbiter constructed and the last retired; its final mission was SSM-90 in February 2003.
By then, the U.S.-Russian-Chinese-European-Japanese-Brazilian International Space Station had become operational, and NASA and Europe had begun flight tests of the jointly developed Hermes shuttle, which became operational in June 2009. NASA retired the ATS in July 2011, ending 43 years of Apollo and Apollo-derived spacecraft missions.
A note on the Presidents: In this alternate timeline Ronald Reagan defeats James Carter in November 1980, but falls to an assassin's bullet (as he very nearly did) in April 1981. His Vice President, George H. W. Bush, finishes Reagan's term, but Carter narrowly defeats him in November 1984 after Bush's Vice President, Alexander Haig, announces a third-party candidacy that draws votes away from the Republican incumbent. Carter declines the nomination in 1988, in part because of Constitutional questions, and Republican James Thompson of Illinois defeats Carter's Vice President, New Jersey Democrat Bill Bradley, to win the White House. Thompson's two terms (1989-1997) see the collapse of the Soviet Union and the start of the International Space Station.
The Unmanned Shuttle Decision: Prudence and the Presidency, John Logsdon, NASA, January 1999, pp. 36-49, 53, 111
SSM-25 Press Kit, NASA, December 1986
SSM-27 Press Kit, NASA, November 1987
Enterprise, Discovery, Endurance, Adventure: NASA's Orbiter Fleet, NASA Facts, December 1996
Chronology of Space Shuttle/Astronaut Transport Spacecraft Missions, 1980-2011, David S. F. Portree, NASA, 2012, pp. 20-22, 26-28, 33-34, 37-40, 45-55, 61-63, 88-91, A-13