|Image credit: NASA/North American Rockwell/General Dynamics|
The Booster's rocket motors would ignite on the launch pad, drawing liquid hydrogen/liquid oxygen propellants from integral internal tanks. At the edge of space, its propellants depleted, the Booster would release the Orbiter. It would then turn around, reenter the dense part of Earth's atmosphere, deploy air-breathing engines, and fly under power to a runway at its launch site. Because it would return to its launch site, NASA dubbed it the "Flyback" Booster. It would then taxi or be towed to a hangar for minimal refurbishment and preparation for its next launch.
The Space Shuttle Orbiter, meanwhile, would arc up and away from the Booster. After achieving a safe separation distance, it would ignite its rocket motors to place itself and an internally carried cargo into Earth orbit. Like the Booster, it would draw liquid hydrogen/liquid oxygen propellants from internal tanks.
After accomplishing its mission, it would fire its motors to slow down and reenter Earth's atmosphere, where it would deploy jet engines and fly under power to a runway landing. As with the Booster, the Orbiter would need minimal refurbishment before it flew again.
|The Space Shuttle Orbiter (upper left) climbs toward low-Earth orbit as the fully reusable Booster begins its turn to fly back to its launch site. Image credit: NASA North American Rockwell/General Dynamics|
NASA managers felt no need for a new launch and landing site; they already had two at their disposal. They planned to launch and land the Space Shuttle at Kennedy Space Center (KSC) on Florida's east coast and at Vandenberg Air Force Base (VAFB), California. Nevertheless, for a time in 1971-1972, a NASA board reviewed some 150 candidate Shuttle launch and landing sites in 40 of the 50 U.S. states. A few were NASA-selected candidates, but most were put forward by members of Congress, state and local politicians, and even private individuals.
The Space Shuttle Launch and Recovery Site Review Board, as it was known, was chaired by Floyd Thompson, a former director of NASA's Langley Research Center in Hampton, Virginia. The Board got its start on 26 April 1971, when Dale Myers, NASA Associate Administrator for Manned Space Flight, charged it with determining whether any of the candidate sites could host a single new Shuttle launch and landing site as versatile as KSC and VAFB were together. The consolidation scheme aimed to trim Shuttle Program cost by eliminating redundancy.
|Image credit: David S. F. Portree (base map by Daniel Dalet/d-maps.com)|
Texas had the most candidate sites (22) of any state, while Nebraska and Wyoming tied for second place with 12 sites each. Furthest north and east were Presque Isle Air Force Base, Dow Air Force Base, and Loring Air Force Base, all in Maine. Furthest south were sites around Brownsville, Texas. VAFB was the westernmost site considered.
|The reusable Booster lands on a runway less than an hour after launch from a nearby launch pad. Image credit: NASA/North America Rockwell/General Dynamics|
In its efforts to cull unsuitable sites, the Thompson Board focused most of its attention on the effects of sonic booms, the sudden waves of air pressure produced when an aircraft or spacecraft exceeds the speed of sound (that is, "breaks the sound barrier"). Sonic booms, which the Board wrote had "the startling audibility and dynamic characteristics of an explosion," were a bone of contention in the U.S. in the early 1970s; concern at the time over possible injury to people on the ground and damage to structures helped to kill U.S. plans to develop a supersonic passenger liner akin to the Anglo-French Concorde.
The Thompson Board determined that the Space Shuttle would generate its most powerful sonic boom during ascent, while the Booster and Orbiter formed what was in effect a single large vehicle. The Booster's rocket plume would, for purposes of calculating sonic boom effects, make the ascending, accelerating spacecraft stack seem even bigger. The Shuttle stack's flight path characteristics - for example, the pitch-over maneuver that it would perform as it steered toward orbit - would create a roughly 10-square-mile "focal zone" for sonic boom effects about 33 nautical miles downrange of the launch site. Winds could unpredictably shift the focal area by several miles.
"Overpressure" in the focal zone would almost certainly exceed six pounds per square foot and might reach 30 pounds per square foot, which would be powerful enough to damage structures. The Board noted that plaster and windows could suffer damage at an overpressure as low as three pounds per square foot . It urged that "the severe overpressures associated with the focal zone. . .be prevented from occurring in any inhabited areas."
|Image credit: NASA/North American Rockwell/General Dynamics|
As the Thompson Board continued its deliberations, the Space Shuttle design was undergoing rapid and profound changes. At its 22 June 1971 meeting, the Board discussed NASA Administrator James Fletcher's 16 June announcement that the space agency would spread out Shuttle costs by adopting "series development" of the Booster and Orbiter. The Orbiter would be developed first. Until the Booster could be developed, the Orbiter would be coupled with an "interim expendable booster" - possibly a modified Saturn V S-IC first stage - that would separate after depleting its propellants and fall back to Earth downrange of the launch site.
In addition, Fletcher had told reporters that Shuttle contractors would abandon work on the Orbiter's reusable internal liquid propellant tanks in favor of expendable external tanks. The expendable tanks would be less technologically challenging than their reusable internal counterparts and thus would have a lower development cost. The tanks would break up high in the atmosphere after separating from the Orbiter.
|Semi-reusable Space Shuttle with reusable Orbiter, twin reusable Boosters, and expendable External Tank. This is the design the Nixon White House favored by late 1971. Image credit: NASA/McDonnell Douglas/TRW|
During the press conference, Fletcher displayed a model of the Shuttle configuration the Nixon White House favored. It included a reusable delta-winged Orbiter with twin unmanned reusable booster rockets and a large expendable external tank for Orbiter ascent propellants. Though this put the semi-reusable design in the spotlight, NASA remained hopeful that the reusable manned Booster would eventually become part of the Shuttle system.
On 15 March 1972, as NASA and Nixon's Office of Management and Budget jousted over the Shuttle's development cost, Fletcher announced that the reusable Booster would be abandoned entirely in favor of the White House design. A pair of reusable Solid Rocket Boosters (SRBs) would separate from the Orbiter/External Tank (ET) combination after expending their propellants and descend on parachutes for recovery. NASA's Office of Manned Space Flight subsequently determined that the SRBs could not touch down in "a controlled manner" on land; they would instead need to splash down and be recovered at sea.
The Board members assumed that NASA would build five reusable Orbiters, begin Space Shuttle flights in FY 1978, and ramp up to 60 Shuttle flights per year beginning in FY 1985. To launch that many missions from Matagorda Island, the Shuttle fleet would need one Orbiter Thermal Protection System (TPS) maintenance and checkout bay, three vehicle assembly highbays for mating Orbiters with their ET/twin SRB stacks, three Mobile Launcher Platforms for transporting Shuttle Orbiter/ET/twin SRB stacks to their launch pads, three launch pads, three firing rooms, and one Orbiter landing strip.
If NASA opted for the two-site approach, three Orbiters based at KSC would conduct 40 missions per year using one Orbiter TPS bay, two vehicle assembly highbays, two Mobile Launcher Platforms, two pads, two firing rooms, and one landing strip. The two Orbiters based at VAFB would conduct 20 missions per year using one Orbiter TPS bay, one vehicle assembly highbay, two Mobile Launcher Platforms, one pad, one firing room, and one landing strip. The KSC/VAFB plan would thus need one more TPS bay, Mobile Launcher, and landing strip than the Matagorda Island plan.
The single-site plan would, however, incur greater construction costs than the dual-site plan, for the simple reason that Matagorda Island had no spaceflight infrastructure already in place. The Board estimated that Matagorda Island construction and operations would cost $5.365 billion through FY 1990, while KSC/VAFB would together cost $5.137 billion.
The single-site plan would, as had been predicted, lead to reduced Shuttle operations costs, but these savings would amount to only $87.6 million. Constructing the Matagorda Island site would, on the other hand, cost $315 million more than would modifying KSC and VAFB to support Shuttle launches. This meant that the single-site option would cost $228 million more than the two-site option.
In addition to the greater monetary cost, the single-site option would introduce substantial programmatic risk and societal costs. The Texas coastal site was partly privately owned, so construction could not begin there until NASA had negotiated purchase of the private land. Infrastructure such as roads, railways, a harbor, an airport, waste treatment plants, and a potable water system would need to be built new or expanded.
Thousands of workers would need to relocate to the Matagorda Island area over a period of less than five years, placing enormous strain on local housing, schools, and what few amenities existed in the immediate area. At the same time, established communities around KSC, already under pressure as the Apollo Program drew to an end, would suffer economically catastrophic job losses.
The Thompson Board briefed James Fletcher on its results on 10 April 1972. Four days later, Fletcher announced at a press conference at NASA Headquarters that Space Shuttles would launch from KSC beginning in 1978 and that launches from VAFB would be phased in early in the 1980s.
Space Shuttle Launch and Recovery Site Review Board, NASA, 10 April 1972
Astronautics and Aeronautics 1971, NASA SP-4016, 1972, p. 281
Astronautics and Aeronautics 1972, NASA SP-4017, 1974, pp. 139-140
Space Shuttle: The History of the National Space Transportation System, The First 100 Missions, Dennis Jenkins, Third Edition, 2008, p. 155