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[II-5]20 Proponents admitted that such vehicleswere much more demanding technically and also required greater development risk andcosts, but they felt that if the technical issues could be overcome, such vehicles would provide the basis for an increased overall investment in space.

North American Rockwell (later,Rockwell International), for example, proposed a series of Class III designs that used alarge booster and orbital vehicle to carry the necessary volume of liquid oxygen/liquidhydrogen fuel. NASA’s “chief designer,” Maxime Faget at the Manned Spacecraft Center,advocated a two-stage concept that mounted a relatively small orbiter atop a much largerrecoverable booster.

[II-6] Both vehicles were powered, and both had straight wings.Faget’s orbiter would carry only a small payload and had only small cross-range capability.21Although by January 1971 many at NASA had begun to view a partially reusable designemploying an external propellant tank and a delta-wing orbiter as probably the best overall choice when weighing development costs and technical risks, NASA engineers nevertheless continued to consider the Faget concept until almost the end of 1971.22The Air Force, which was also involved at senior levels in the work of the STG, washighly critical of the Faget design, arguing that reentry would put extremely high thermaland aerodynamic loads on the orbiter’s straight wings. The Air Force Flight DynamicsLaboratory argued forcefully that a delta-wing design would provide a safer orbiter withmuch greater cross range.23 Ultimately, the Air Force’s wish for high cross range and largepayload capacity, as well as reduced expectations for NASA’s future budget, forced NASAto give up on the Faget concept and begin serious work on the partially reusable conceptthat became the final Space Shuttle design.

By the time NASA had reached this decision,many other Shuttle concepts had been explored, were found wanting, and had fadedfrom the scene. NASA awarded Phase B design study contracts for the Shuttle toMcDonnell Douglas and North American Rockwell in June 1970; these studies used theFaget two-stage fully reusable concept as their baseline. NASA also awarded Lockheed anda Grumman/Boeing team additional contracts to conduct Phase A studies for systemsusing some expendable components, should the two-stage concepts examined in thePhase B studies prove too expensive or technically demanding. In the meantime, NASApursued its own internal studies, in part, to improve the competence of its engineers andto give them better insight into the contractors’ work.24As noted earlier, logistics support for the space station was cited as one of the principal justifications for the Shuttle.

However, by its September 1970 budget submission to the19. Slightly paraphrased from ibid., 1: 534.20. As in the other chapters in this volume of Exploring the Unknown, the documents that follow this essayare not necessarily in chronological order, but rather follow in numerical sequence with the context of the essay.21. An orbiter with high cross range is capable of altering its orbital plane significantly. The Air Forcetended to favor high cross-range capability on the assumption that it might wish to fly only a single orbit andreturn to Earth at the same location from which it had been launched. However, during that one orbit, Earthwill have rotated sufficiently to require the Shuttle to change latitude to reach the launch site, thus requiring theorbiter to have sufficient cross range.

NASA had minimal need for high cross-range capability.22. Hallion and Young, “Space Shuttle: Fulfillment of a Dream,” p. 1031.23. Eugene S. Love, “Advanced Technology and the Space Shuttle,” 10th von Kármán lecture, 9th annualmeeting, American Institute of Aeronautics and Astronautics, Washington, DC, January 1973 (AIAA Paper 73-31).24. Interview of Milton Silveira by Joseph Guilmartin and John Mauer, November 14, 1984, p. 6, transcriptin NASA Historical Reference Collection.****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 167EXPLORING THE UNKNOWN167White House, NASA officials realized that the Nixon administration and Congress wereunwilling to support simultaneous development of both a space station and a Space Shuttle.A complete restructuring of NASA’s expectations was in order.

Between September 1970and May 1971, the focus of NASA’s attention was gaining White House approval for developing a two-stage fully reusable Shuttle. By May 1971, the expectations for NASA’s futurebudget were reduced sufficiently that having the resources needed to develop such a twostage, fully reusable design was out of the question. NASA estimated it would need at least$10–12 billion to build a two-stage Shuttle, but with a fiscal year 1971 budget of only $3.2 billion and little hope of future funding increases, the agency was forced to examine conceptswith several expendable components as a means of lowering development costs. [II-7]An important technical issue also led to the abandonment of the fly-back reusablebooster.

As designs began to mature, it became clear that for this concept to be feasible,the orbiter staging velocity (that is, the velocity at which the booster would release theorbiter) had to be 12,000 to 14,000 feet per second. Achieving this velocity would requirean extremely large booster incorporating enormous fuel tanks. Upon returning throughthe atmosphere at these velocities, the booster would have to sustain extremely high heatloads. NASA engineers became increasingly uncomfortable about their ability to buildsuch a booster, given the technology then available and generally poor knowledge aboutatmospheric reentry of large structures.The ultimate design of the Shuttle orbiter and other system components dependedon decisions about five key orbiter characteristics:•••••Payload bay load capacity and sizeExtent of cross-range maneuverabilityPropulsion systemGlide or power-assisted landingPrimary structural material25The first two were of greatest concern to the Air Force.

Because NASA needed AirForce support in the White House and congressional debates over the Shuttle, in January1971, the space agency agreed to the following design criteria:•••Fifteen-foot by sixty-foot payload bayA total of 65,000 pounds of easterly payload lift capacity (40,000 pounds for polarorbits from Vandenberg Air Force Base)A cross range of 1,100 nautical miles26With these decisions made, NASA was then able to focus on what combination oforbiter design, propellant tank, and booster best fit the required characteristics.Throughout 1971, Manned Spacecraft Center and Marshall Space Flight Center designersanalyzed a remarkable twenty-nine different Shuttle designs, incorporating a wide varietyof orbiter capacity, hydrogen and oxygen fuel tank, and boosters (see Table 2–1).27While still evaluating two-stage Shuttle designs, NASA engineers had found that theexisting F-1 and J-2 engines, both of which were by then out of production, were inadequate to meet the safety and weight requirements of the Shuttle without significant25.

Scott Pace, “Engineering Design and Political Choice: The Space Shuttle, 1969–1972,” M.S. thesis,Massachusetts Institute of Technology, May 1982.26. For more details on the design criteria, see Document II-32 in Logsdon, gen. ed., Exploring theUnknown, 2: 369–77.27. None of these designs, however, were sized to carry 65,000 pounds to orbit (100-nautical-mile circularorbit), although several had a fifteen-foot by sixty-foot payload bay and could reach the 1,100-nautical-mile cross range.1308595——135125—12595128—10515313010095135135110110110114145145100115140140140190190St (AR7)St (AR7)St (AR5)45˚ LE SWDeltaDeltaSt (AR5)45˚ LE SWDeltaDeltaDeltaDeltaSt (AR5)St (AR5)DeltaDeltaDelta45˚ SW45˚ SWDeltaDeltaDeltaDeltaDeltaDeltaDelta30˚ SWDeltaDeltaDelta60˚ Delta50˚ DeltaWing1,2757857921,1202,1002,7001,0001,4142,5001,5002,3601,9008601,1102,6002,0001,5001,2001,7002,2002,2002,2002,5002,9002,9002,0001,2903,1003,1803,1802,9003,200WingArea (ft2)15 by 3015 by 4015 by 4015 by 4015 by 4015 by 6015 by 6015 by 6012 by 4012 by 4015 by 4012 by 4015 by 4015 by 6015 by 4012 by 4015 by 3012 by 4012 by 6015 by 4015 by 4015 by 4015 by 4015 by 6015 by 6015 by 4015 by 4015 by 6015 by 6015 by 6015 by 6015 by 60PayloadSize (ft)2020202020404040404040402040402020404020202020404020202525254040PayloadWeight(thousands)1,2721,0801,0641,0641,0641,3251,3151,3151,2001,1201,0801,0801,140—1,1401,2009601,4401,4401,1101,1801,1101,0601,4001,1401,0701,1101,3151,3151,3151,3151,315BodyLength(in.)Ext H2 , Int O2, 4 Eng.

Orbiter, SRM BoosterExt H2 , Int O2, SRM BoosterExt H2 , Int O2, SRM BoosterExt H2 , Int O2Ext H2 , Int O2Ext H2 , Int O2, Reusable Booster(Stretched 022) Ext H2 , Int O2(Stretched 022A) Ext H2 , Int O2Ext H2 , Int O2, Reusable BoosterExt H2 , Int O2, Main Engine, OWB Tanks in rear, SRM Booster(Shortened 023) Ext H2 , Int O2, Reusable BoosterOWB Tanks Amidships, Ext Main Engine3 J-28 Engines3 J-28 Engines3 J-28 Engines, SRM Booster(Modified 026) SRM Booster(Shortened 025 & 028), SRM Booster(Modified 035)(Stretched 035)3 J28/SRM Booster3 J28/SRM Booster3 J28/SRM Booster3 J25/Pressure-Fed Booster3 Uprate J28/Recoverable Booster3 Super Uprate J25/(036) SRM Booster550K M1Pc/Solid Booster3 J28/Pressure-Fed Booster4 J28/Pressure-Fed Booster4 J25/Pressure-Fed Booster4 J28 Retractable/Pressure-Fed Booster3 MiPc, SRM Boosters3 MiPc, 150-ft2 Canard, Twin TailFeatures168020021122022A022B023024025026027028029030031032033034035035A036036A036B036C037037A038039040040A040B040C040C-1LandingWeightVehicle (thousands)Table 2–1.

Shuttle Configurations Evaluated by the Manned Spacecraft Center (1969–1971)****EU4 Chap 2 (161-192)4/2/0112:45 PMPage 168DEVELOPING THE SPACE SHUTTLE215.3—165175185185049A05005105205305435˚ Delta35˚ Delta2,2402,2402,12015 by 60 up15 by 60 up15 by 60 up—15 by 60 up15 by 6015 by 6015 by 6015 by 6015 by 6015 by 6015 by 6015 by 6015 by 6015 by 6010 by 3010 by 30—14 by 4515 by 6015 by 6015 by 6015 by 60PayloadSize (ft)25252525404040404040151525252725—25404040401,2501,2501,250—1,0501,3151,3151,3151,3151,3151,3151,3001,3651,2601,260770880——1,3151,3151,3151,315PayloadBodyWeightLength(thousands) (in.)3 Hi Pc Swing Engines, 149” SRM, 75’ Bay with OWB inrear, 180-ft2 Canard4 CC Swing Engines, 120” SRM, 75’ Bay, 190-ft2 Canard4 Hi Pc Swing Engines, 140” SRM, 75’ Bay, 190-ft2 Canard— —3 Hi Pc Swing Engines, 156” SRM, 180-ft2 Canard3 Hi Pc, 425 ft2 Wing Clove, Twin Tail, 178” SRM, 62” ASRM3 MiPc, 300-ft2 Wing Clove, Twin Tail, SRM Boosters3 MiPc3 MiPc3 MiPc, 100-ft2 Canard, Twin Tail3 MiPc, 150 ft2 Canard, Twin Tail3 J28/Pressure-Fed Booster3 J25/Pressure-Fed BoosterGlider, TIII L6 BoosterGlider, TIII L6 BoosterGlider, 2 MiPc oo Ext Tank, PF Booster2 MiPc, PF Booster—3 MiPc, Twin Tail, SRM Boosters2 MiPc, Twin Tail, SRM Boosters4 MiPc, 324-ft2 Wing Clove, Twin Tail, SRM Boosters4 400K, 308-ft2 Wing Clove, Twin Tail, SRM Boosters3 Hi Pc, 350 ft2 Wing Clove, Twin Tail, 156” SRM, 62” ASRMFeatures12:45 PM35˚ Delta35˚/–19˚ Delta 3,00050˚ Delta4,15060˚ Delta4,44050˚ Delta3,20055˚/–19˚ Delta 2,80030˚ SSW1,29030˚ SW1,290Delta2,50030˚ SW1,25530˚ SW90060˚ Delta2,000————49˚/–5˚ Delta3,45035˚/–19˚ Delta 3,24035˚/19˚ Delta3,08075˚/55˚1,150/DBL Delta3,42075˚/55˚1,250/DBL Delta3,600—35˚ Delta2,000WingWingArea (ft2)4/2/01Source: Richard P.