GRUMMAN & BOEING “H33” [PHASE B SHUTTLE] [1971]
Notes:
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Boeing / Grumman “H33” shuttle lfitoff. In December 1970 the contractors received approval from NASA's Manned Spacecraft Center to conduct studies of mostly reusable two-stage shuttles employing externally mounted expendable fuel tanks on the orbiter. The final results were presented in July 1971, but it evident after only a few months that the drop-tank orbiter represented a real breakthrough. Moving the orbiter's bulky hydrogen fuel to a pair of expendable drop tanks greatly reduced the size and weight of both vehicles while reducing the total development cost by at least $1 billion.
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“H-33” booster/orbiter separation. The huge wing tanks (which carried 54,011kg of LH2) had the effect of increasing the orbiter's “propellant fraction”, I..e. the shuttle's empty weight would be less despite carrying more propellant at liftoff. Not only did this produce a smaller and less expensive orbiter, it also enabled Boeing to simplify the booster as well. The system would now stage at a lower velocity (2123 meters/sec.) than the fully reusable Phase-B design's 3000m/s. As a result, the booster would have to carry less rocket propellant for ascent and less jet fuel for its flight back to the launch site. The lower staging velocity also meant the booster's thermal protection system could be simplified and Boeing settled for a simple “heat sink” design much like the old X-15's. The total gross liftoff weight was reduced by 590t compared with the Phase-B baseline shuttle, and it was expected that the margina cost per flight would stay the same since the additional cost of the fuel tanks would be offset by the reduction in complexity & size (e.g. fewer engines to refurbish between flights). Note that the Grumman orbiter has three 1,845.75-kilonewton thrust engines rather than two 2.45KN-thrust motors like the fully reusable Phase-B orbiter. Grumman had to install a third engine as a safeguard against engine failure. The Phase-B design had no such problems since it would stage at a higher velocity and still could make it to orbit despite the failure of a single engine.
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Payload capability (without landing jets): 29,484kg into a 185km 28.5 deg. Orbit; 18,144kg into a 185km 90 deg. polar orbit; 11,340kg into a 500km 55 deg. orbit with landing jets installed on orbiter.
Development cost in FY'71 [1999 $s]: $2,674.3 million [=$11B] for orbiter, $32.6 million [=$134.1M] for drop tanks, $2180.6M [=$9B] for booster, $1,0165 million [$4.181B] for main engines plus $892.9 million [=$3.673B] for flight tests == $6.8 billion in total, or $28 billion at FY 1999 rates. Each booster would have cost $273.6 million and the orbiter would have cost $615 million per copy.
Cost per mission: $4.3 million including $0.74M for the drop tanks and $0.54M for manpower. [1971 rates] or $586/kg in 1999. 75 missions/year max with routine 2-week turnaround between flights. Space station rescue mission capability within 48 hours of emergency call.
Liftoff Thrust: 2,258,500 kgf. Total Mass: 1,963,916 kg. Core Diameter: 10.0 m. Total Length: 90.0 m.
Stage Number: 1. 1 x Shuttle H33-1 Gross Mass: 1,489,717 kg. Empty Mass: 224,431 kg. Thrust (vac): 2,546,578 kgf. Isp: 442 sec. Burn time: 216 sec. Isp(sl): 392 sec. Diameter: 10.0 m. Span: 54.1 m. Length: 74.7 m. Propellants: Lox/LH2 No Engines: 12. SSME Study
Stage Number: 2. 1 x Shuttle H33-2 Gross Mass: 474,199 kg. Empty Mass: 100,153 kg (incl. 2 * 4,694kg drop tanks) . Thrust (vac): 1846.75KN. Isp: 459 sec. Burn time: 234 sec. Isp(sl): 359 sec. Diameter: 8.1 m. Span: 29.6 m. Length: 47.9 m. Propellants: Lox/LH2 No Engines: 3. SSME Study
”Space Shuttle” -- Dennis R. Jenkins, 1981, ISBN: 0963397451
"Spaceflight and Rocketry -- a Chronology”, David Baker:, Facts on File Inc, 1996, ISBN 0-8160-1853-7