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By 1991, the Soviet Union and itseconomy had collapsed, taking with themthe will to continue to invest large sums inspace achievements. In a few years, Buran Figure 2–7. The former Soviet Union’s unmanned shuttle,became an exhibit in a Moscow park, and Buran, stood ready on the launch pad with the Energiyathe Energiya launcher was never used again launcher in late 1988. It would make only one flight.to lift payloads into orbit.83.

“Soviet Union Developing Range of Manned, Unmanned Launchers,” Aviation Week & SpaceTechnology, March 28, 1988, pp. 52, 53, 58.84. Craig Covault, “Soviet Shuttle Launched on Energia Booster,” Aviation Week & Space Technology,November 21, 1988, pp. 18–21.****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 189EXPLORING THE UNKNOWN189Variations on the Shuttle ThemeBeginning well before the Space Shuttle actually flew, engineers considered a widevariety of technical options for improving or extending the Shuttle’s basic capabilities.These included adding to its lift capacity, carrying civilian passengers, and extending thestay time on orbit.

The impetus for such studies derived from the firm belief among someobservers that once the Shuttle became operational, the demand for launch serviceswould grow quickly, making it attractive to add significantly to overall launch capacity.Among the ideas driving such thinking was the photovoltaic solar power satellite, which ifbuilt would have required lofting millions of kilograms of materials into geosynchronousorbit and space workers into LEO.85 Concepts developed during the mid-1970s rangedfrom simply adding additional smaller solid rockets to the SRBs, to substituting large liquid rocket boosters for the SRBs, to building a fly-back booster.86 Concepts also includedideas as diverse as a passenger-carrying orbiter capable of taking several tens of passengersto and from orbit and a strictly-cargo vehicle based on using the SRBs, the external tank,the SSMEs, and a cargo canister to substitute for the orbiter.In general, these ideas never got beyond the concept stage.

Yet, by the late 1980s, asspace station planners struggled with the realities of lofting a station into orbit and resupplying it, some experts began to revive such concepts. Among other options, they considered building a heavy-lift launch vehicle that would be capable of launching large stationpayloads to orbit. The specter of losing an orbiter in the course of station construction,and the large number of Shuttle flights (more than twenty) required for the station thenunder consideration, led to studies of an alternative, larger cargo vehicle to reduce thenumber of orbiter flights. The Advanced Launch System (ALS) then under consideration(see Chapter 4) might have served such a purpose, but some NASA engineers argued fora cargo vehicle based on the Space Shuttle.Initially, this was called the Shuttle-Derived Vehicle; later, the concept became known asthe Shuttle-C, for cargo.87 [II-46] Because the design of the Shuttle puts the SSMEs necessaryfor part of the propulsion on the orbiter itself, the Shuttle-C cargo carrier would also need tocarry liquid engines to reach orbit.

NASA considered the option of using the reusable SSMEsin a boat-tail configuration and dropping them off to be recovered in the ocean, but theagency found recovery and refurbishment too costly.88 NASA engineers decided instead toemploy SSMEs that had flown enough times that they were no longer sufficiently reliable forhuman flight, then letting them burn up in the atmosphere after use. As the concept wasdeveloped, the Shuttle-C would have been capable of lofting about178,000 pounds to orbit from Kennedy Space Center.

Ultimately, after nearly four years ofstudy, NASA dropped its Shuttle-C efforts, in large part because OMB deemed the vehicle toocostly. Furthermore, the move away from using the Shuttle launch for science payloads thatcould fly on ELVs removed most of the non–space station launch pressure on the Shuttle.85.

Peter E. Glaser, “Power from the Sun: Its Future,” Science 162 (November 22, 1968): 857–86. For adescription and assessment of solar power satellite concepts of the late 1970s, see U.S. Congress, Office ofTechnology Assessment, Solar Power Satellites, OTA-E-144 (Washington, DC: U.S. Government Printing Office,August 1981).86. M.W. Jack Bell, “Space Shuttle Vehicle Growth Options,” paper presented at the American Institute ofAeronautics Conference on Large Space Platforms: Future Needs and Capabilities, Los Angeles, CA, September27–29, 1978.87.

Theresa M. Foley, “NASA May Seek Proposals for Shuttle-Derived Booster,” Aviation Week & SpaceTechnology, June 29, 1987, pp. 24–25.88. Craig Covault, “Shuttle-C Unmanned Heavy Booster Could Simplify Space Station Launch,” AviationWeek & Space Technology, August 15, 1988, pp. 87–88.****EU4 Chap 2 (161-192)1904/2/0112:45 PMPage 190DEVELOPING THE SPACE SHUTTLEThe Advanced Solid Rocket MotorThe failure of the Space Shuttle’s solid rocket motor had repercussions for NASA’sShuttle program that extended far beyond the redesign of the motor. Proponents of bothliquid boosters (pump-fed and pressure-fed) and more advanced solid rocket designsargued within NASA and before Congress that a major overhaul was needed.

In additionto providing additional safety, the proposed designs would have improved the payloadcapacity of the Shuttle, which fell far short of the expected 65,000 pounds placed in thestandard twenty-eight-degree LEO 110 nautical miles above Earth’s surface. As a result ofweight growth during manufacture and early operations, the Shuttle was capable of carrying a maximum payload to this orbit of only 48,000 pounds. However, some payloads,particularly space station components, were expected to weigh more.During the period after the Shuttle returned to flight, NASA engineers explored twonew solid rocket designs—the Advanced Solid Rocket Motor (ASRM) and an improvedRedesigned Solid Rocket Motor (RSRM).

The ASRM was a totally new design that woulduse a new manufacturing process, allowing the entire motor to be poured at one time. Itwould therefore not have joints that might fail. Proponents argued that the ASRM wouldprovide greater safety than segmented boosters. After conducting detailed engineeringstudies of both liquid- and solid-fuel designs and comparing costs and safety, NASA decided in early 1989 to proceed with the ASRM on the basis that it would result in lower overall costs with comparable flight safety.89 In March 1989, NASA’s Aerospace Safety AdvisoryPanel noted that “on the basis of safety and reliability alone it is questionable whether theASRM would be superior to the RSRM . . .

until the ASRM has a similar background oftesting and flight experience.”90Yet, NASA’s own analysis disagreed with these findings, and in late April 1989, theagency awarded two contracts for the ASRM to a partnership formed between Aerojet andLockheed. One contract supported the design and development of the ASRM; the secondcontract was for the design, construction, and operation of an automated solid rocketmotor production facility.

NASA designated Yellow Creek, Mississippi, as its preferred government-owned/contractor-operated ASRM production site and the Stennis SpaceCenter in Mississippi as the motor test location. NASA estimated that ASRMs could beready for a first launch in 1994 or 1995. Agency officials also expected that the ASRM program would help promote a competitive solid rocket motor industry.91The ASRM was never built. After NASA built the plant in Yellow Creek, Mississippi, andbegan to outfit it, Congress began to have second thoughts about the increasing costs ofthe ASRM program.

In October 1993, Congress voted to shut down the ASRM program asa cost-saving move. NASA then decided to put greater emphasis on improving the RSRM.Space Shuttle in the 1990sOnce NASA was assured that the redesigned solid rocket motors worked safely, that theoperation of the SSME improved, and that other safety-related issues were addressed, thespace agency began to operate the Space Shuttle on a more regular basis, and launches hadfewer delays. In fact, by the late 1990s, NASA felt that it could hand over the day-to-day89. Proponents of solid rocket motors argued that such motors, if properly designed, are nearly as safe asliquid rocket motors that are by their very nature much more complicated and suffer from a greater number ofpossible failure modes.90.

Aerospace Safety Advisory Panel, Annual Report for 1988 (Washington, DC: NASA Headquarters, CodeQ-1, March 1989), p. 3.91. NASA, “Space Shuttle Advanced Solid Rocket Motor—Acquisition Plan,” March 31, 1988, p. 3, NASAHistorical Reference Collection.****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 191EXPLORING THE UNKNOWN191operations of the Shuttle to a private contractor, United Space Alliance. [II-47] Thereusability of the orbiter also made it possible for NASA to demonstrate the Shuttle’s ability to return payloads from orbit. For example, in 1990, STS-32 returned from the LongDuration Exposure Facility, which had been in orbit since 1984, when it was deployed bySTS 41-C. After the communications satellite Intelsat VI was placed in an unusable orbitby a Titan III rocket in March 1990, NASA astronauts aboard STS-49 in May 1992 capturedthe satellite and redeployed it after attaching a new perigee kick motor to place it in geosynchronous orbit.