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Hallion and James O. Young, “Space Shuttle: Fulfillment of a Dream,” in Richard P. Hallion, ed., The Hypersonic Revolution: EightCase Studies in the History of Hypersonic Technology, Volume II (Dayton, Ohio: Wright-Patterson Air Force Base, Special Staff Office, AeronauticalSystems Division, 1987), pp. 1049–50.19019019015015011411411010583100—165185205195205040C-2040C-3040C-4040C-5040C-6041041A042A042B043044045046047048048A049LandingWeightVehicle (thousands)Table 2–1 continued****EU4 Chap 2 (161-192)Page 169EXPLORING THE UNKNOWN169****EU4 Chap 2 (161-192)1704/2/0112:45 PMPage 170DEVELOPING THE SPACE SHUTTLEredesign.

NASA favored an engine having higher specific impulse than either of these,which would require the use of only three, rather than four, engines in the orbiter. Theagency decided to build a completely new engine; in July 1971, it awarded the development contract to Rocketdyne for its staged combustion design, which became known asthe Space Shuttle Main Engine (SSME).28Although NASA continued to explore a wide variety of payload bay sizes and overallpayload capacity during its exploration of the optimum Shuttle design, throughout 1970and 1971, it favored a fifteen-foot by sixty-foot payload bay.

After the decision to defer anattempt to gain approval for developing a Saturn V–launched space station, among thereasons for favoring a payload bay of this size was that it was compatible with the growingdesire to use the Shuttle like a truck, routinely using it to place large payloads in orbit.The Air Force was also interested in the larger cargo bay for hauling some of its nationalsecurity payloads. In addition, the larger bay made balancing the orbiter for launch easier and therefore carried less flight risk than a shorter payload bay.

In the fall of 1971, theWhite House Office of Management and Budget (OMB) asked NASA to examine the benefits and drawbacks of a smaller Shuttle, having a shorter, narrower payload bay. NASAanalyses showed, however, that developing a smaller orbiter would have relatively smalleffect on the overall inert or gross launch weight of the Shuttle system, and thus its development costs.

[II-8] NASA engineers also pointed out that a larger payload bay made thehandling of multiple payloads more efficient.By late 1971, designers both within NASA and industry had begun to realize that themost cost-effective design for the Shuttle system was a vertically launched delta-wingedorbiter mounted to an external tank carrying liquid oxygen and liquid hydrogen, flankedby booster rockets. [II-9, II-10] Putting all of the launch fuel and oxidizer in an externaltank allowed designers to reduce the size of the orbiter.

It also made the design and construction of the propellant tanks simpler and therefore cheaper. The design allowed theShuttle to carry a greater payload as a fraction of total vehicle inert weight compared to atwo-stage, fully reusable Shuttle system.29Throughout the final months of 1971, OMB persisted in its pressure to lower Shuttledevelopment costs (see Document II-7). On December 29, 1971, NASA AdministratorJames C. Fletcher sent OMB Deputy Director Caspar W. Weinberger a letter summarizingthe results of NASA’s most recent analyses, which showed that a Shuttle with a fifteen-footby sixty-foot payload bay was still the “best buy.” However, yielding to OMB pressure, NASArecommended that President Nixon approve a design with a smaller bay.30 [II-11] Five dayslater, on January 3, 1972, much to NASA’s surprise, President Nixon authorized the spaceagency to proceed with developing a Space Shuttle with the larger payload bay.

Therewere many factors involved in the decision to authorize NASA to proceed with the Shuttleprogram it preferred.31 Among them was the desire on the part of Nixon and his politicaladvisors to initiate during the 1972 presidential election year a large aerospace programwith significant employment impacts in key electoral states. [II-12] Nixon met with28. Staged combustion involves partially burning the propellants before burning them completely in asecond phase of combustion. NASA chose this design from among three: an “Aerospike” or plug-nozzle designthat did away completely with the expansion bell and two expansion bell designs.

See J.P Loftus, S.M. Andrich,M.G. Goodhart, and R.C. Kennedy, “The Evolution of the Space Shuttle Design,” unpublished manuscript,Johnson Space Center, Houston, TX, 1986, pp. 15–24.29. See Document III-30 in Logsdon, gen. ed., Exploring the Unknown, 1: 549–55.30. For a fuller discussion of the process leading to Space Shuttle approval, see John M. Logsdon, “TheSpace Shuttle Program: A Policy Failure?,” Science, May 30, 1986, pp. 1099–1105; Thomas Heppenheimer, TheSpace Shuttle Decision: NASA’s Quest for a Reusable Space Vehicle (Washington, DC: NASA SP-4221, 1999).

See also thediscussion of the Shuttle decision in ibid., 1: 386–88, 549–59.31. See Document III-28 in ibid., 1: 546–47.****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 171EXPLORING THE UNKNOWN171Fletcher and NASA Deputy Administrator George M. Low on January 5, 1972; afterwards,the White House issued a statement announcing Nixon’s approval of the Space Shuttle.32The January 3 decision left open several issues, including whether the Shuttle’s strapon boosters would use solid or liquid fuel.

[II-13] In Shuttle system configuration 040C(see Table 2–1), the external tank was flanked by two large, “strap-on” solid rocket boosters (SRBs). This design ultimately became the foundation of the Space Shuttle’s configuration. Nevertheless, until March 1972, other possible designs were still on the table, andeach had their supporters. For example, in preparation for choosing the booster rockets,NASA studied three general types: large solid-fuel boosters; liquid, pressure-fed boosters;and liquid, pump-fed boosters. To reduce operations costs, NASA decided to make theboosters reusable. After separation from the Shuttle at about forty kilometers altitude,they would fall back to the ocean on large parachutes and be recovered from the sea soonafter launch (Figure 2–3).Technical discussions over the relative merits of these designs centered on which typeof booster was safest, most easily refurbished, and cheapest to develop and manufacture.Proponents of liquid motors pointed out that NASA and the Air Force had extensive experience with liquid motors and that they offered greater safety.

Liquid engines had the distinct advantage that if system malfunctions were detected in the startup prior to launch,they could be shut down immediately and the launch safely aborted. If an engine failedafter launch, it could be shut down and the launch aborted to an overseas airstrip afterFigure 2–3. This is the standard mission profile for the partially reusable Space Shuttle that actually emerged from the politicalapproval process.

(NASA photo)32. See Document III-32 in ibid., 1: 558–59.****EU4 Chap 2 (161-192)1724/2/0112:45 PMPage 172DEVELOPING THE SPACE SHUTTLEthe boosters and the external tank were dropped off. By contrast, once the SRBs wereignited, they could not be shut down (although it was possible to terminate their thrust byblowing off the top of the booster), and the abort potential was decreased. In addition,solid rocket motors of the size NASA was considering (156-inch diameter) had never beenused, although the Air Force had tested such large engines and felt they would be sufficiently reliable.

Advocates of the big dumb booster designs of the 1960s felt that the pressure-fed design offered greater overall simplicity, which would contribute both to lowercosts and to safety.33 Supporters of solid rocket motors cited the high reliability of solids,as well as their lighter weight and greater simplicity compared to liquid designs.34 Also,NASA had strong concerns about its ability to refurbish liquid rocket motors after theyhad been subjected to the corrosive action of an ocean bath. By March 1972, driven primarily by cost considerations, the pendulum of apparent advantages swung in favor oflarge solid rocket engines, and NASA officials decided to proceed with solid rocket motordevelopment, judging that such motors offered sufficient reliability and ease of handlingto be used for human spaceflight.35 [II-14] NASA announced its choice of solid boosterson March 15, 1972, as it defended the Shuttle program before Congress.

[II-15]The prime contractor for the Shuttle orbiter still had to be decided. Grumman,Lockheed, McDonnell Douglas, and North American Rockwell had all submitted competitive designs for a Shuttle based on the Marshall Space Flight Center 040C design. ANASA-Air Force Source Evaluation Board rated North American Rockwell the highest,based on an evaluation of contractor strengths in:•••••••Manufacturing, test, and flight-test supportSystem engineering and integrationSubsystem engineeringMaintainability and ground operationsKey personnel and organizational experienceManagement approaches and techniquesProcurement approaches and techniquesOn July 26, 1972, NASA Administrator James Fletcher met with Deputy AdministratorGeorge Low and Associate Administrator for Organization and Management Richard C.McCurdy to make the final Shuttle contractor decision.

This choice was essentiallybetween North American Rockwell and Grumman, the two companies that had receivedthe highest ratings from the Source Evaluation Board. After considerable discussion, thethree adopted the board’s recommendation. [II-16] In August 1972, North AmericanRockwell received the contract to design and develop the Shuttle orbiter. Later, MortonThiokol was selected to produce the SRBs.36 [II-17] NASA also selected Martin Marietta todevelop the external tank. The Manned Spacecraft Center assumed responsibility forsupervising overall orbiter development.

Marshall Space Flight Center was to supervisethe development and manufacturing of the SRB, the SSME, and the external tank, and33. Arthur Schnitt and F. Kniss, “Proposed Minimum Cost Space Launch Vehicle System,” Report no.TOR 0158(3415)-1, Aerospace Corporation, Los Angeles, CA, July 18, 1966. For a general discussion of the bigdumb booster concept, see U.S.