Slide 33 of 125
The early Boeing/Grumman design shown here was a standard fully reusable two-stage concept;
Grumman initially conducted a limited 6-month effort on two Phase-B type fully reusable
designs. These concepts were used as a point of departure for later trade studies.
Boeing / Grumman “H33” shuttle liftoff. 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. Grumman also claimed their external-tank design would
offer greater flexibility, e.g. increasing tankage about 10% in volume combined with a 10 per cent
rocket engine thrust uprating would have accomodated a 13,600-kilogram increase in payload
“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 50% 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 aircraft-like “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
marginal 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. smaller engines to refurbish between
flights). The Grumman orbiter version depicted here has three small engines unlike the NAR &
McDAC Phase-B designs. Grumman decided that three 1,845.75-kilonewton thrust engines rather
than two 2.45KN-thrust motors would act 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.
Shuttle Phase-B options. Although Grumman & Boeing felt a parallel orbiter/booster
development program would be the most cost effective option, the contractors also proposed a
staggered schedule where the H-33 shuttle orbiter would be developed first. It would initially
be launched by an expendable S-IC rocket (configuration "4" above) derived from the Saturn V
moon rocket visible at far left. The fully reusable Boeing shuttle booster would later be introduced
(configuration "2" above). Note that the Grumman/Boeing H-33 shuttle is considerably smaller than
the North American Rockwell ("1") and McDonnell-Douglas ("3") fully reusable Phase-B shuttles.
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
”Program Changes Boost Grumman Shuttle” -- AW&ST, 1971/July 12/p.36
”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