Slide 34 of 125
The “Single-stage Earth-orbital Reusable Vehicle” (SERV) was the most unusual of all space
shuttle concepts to emerge from the Phase A/B studies. It was refined by Chrysler
Corporation's Space Division under a $750,000 contract in June 1970-June 1971. NASA only
provided a handful of safety and operability-related requirements such as return to
preselected landing site minimum of once every 24 hours with 11,340kg payload, from a 55 degree
space station orbit. Like Phil Bono's earlier designs, SERV would have utilized an
“integral aerospike engine” (a small prototype was actually built). The engine was developed
by Rocketdyne and consisted of 12 modules throttable to 18-120% of the rated thrust. It was
regarded as highly risky since the vehicle gross weight was very sensitive to the engine
performance and structural weight. SERV used 28 vertical-lift landing jet engines to cancel
terminal velocity and to provide for hover time. Chrysler's trade studies indicated that
landing rocket engines would weigh less than jets only if SERV had to carry enough
propellant to overcome landing errors of less than 2,750 meters below 7.62km altitude. But
this appeared to be overly optimistic due to concept's the relatively limited crossrange
maneuvering capability, so the designers selected landing jet engines plus enough JP-4 fuel
to compensate for a descent positioning error of up to 7,250 meters.
NASA dictated that the first task of the SERV study be mainly devoted to researching past VTVL
SSTO studies to identify their best features. Chrysler's final concept was very similar to a
1970 VTVL SSTO design developed in-house at NASA's Office of Advanced Research & Technology
(OART) in 1970 by Edward Gomersall. The “OART-M.A.D.” single-stage-to-orbit RLV would have
utilized J-2S propulsion technology from the Saturn program. The concept at left was intended
as a replacement for the Saturn-IB rocket stage. Gomersall's fully reusable SSTO design would
have had a small 5-man winged spacecraft, submerged central cargo bay, integral aerospike
engine for ascent propulsion and ballistic reentry just like Chrystler's SERV (right). The
main difference was the external shape; Chrysler preferred an Apollo type design although
it would have resulted in increased ascent velocity losses due to air drag. But the maximum
deceleration during reentry would only have been 3 g's vs. more than 4 g's for the slender
OART-M.A.D. configuration. The crossrange capability would have been 130km vs. up to 2200km
for a nose-first reentry wingless conic or biconic shape. But Chrysler felt the base-first
reentry mode would be preferable since there would be plenty of room for the engines. An
Apollo-type ablative thermal protection system would have been used to reduce the development
risk although the designers believed an advanced reusable TPS would weigh less and reduce the
maintenance cost per flight.
Unlike the other shuttle concepts, SERV would have flown unmanned although it could be
outfitted with several different kinds of spacecraft mounted on the nose of the SSTO vehicle,
to provide for passenger flights. The payload vehicles would have separated from SERV in orbit
and contained their own docking and in-orbit propulsion systems since SERV was not designed
for docking with space stations. The primary manned payload was the “MURP” -- Manned Upper
Reusable Payload. This small 10-man spaceplane was originally developed by McDonnell-Douglas
during the early shuttle Phase-A study for use with expendable boosters. MURP would have
contained a launch abort system for the crew and also would have provided the sort of reentry
crossrange sought by the US Air Force. Other payloads such as large-diameter space station
modules or simple Apollo CM-derived ballistic crew capsules could also have been carried into
orbit by SERV.
Development Cost in FY 1971 dollars: $3,565 million [=$14,666M in 1999 $s] plus $350 million [=$1440M in FY 1999] for each production vehicle.
Payload capability: 11,340kg to 550km 55 deg. space station orbit and return. 52,816kg to 28.5 deg. 204km orbit plus return capability of 20,411kg. 19,493kg to 185km 90 deg. orbit. 18.3 * 7m diameter cargo bay.
Liftoff Thrust: 33,151KN. Total Mass: 2,721,554 kg. Core Diameter: 18.3 m. Total Length: 24.0 m.
Stage Number: 1. 1 x Shuttle SERV-1 Gross Mass: 2,721,554 kg. Empty Mass: 224,187 kg. Thrust (vac): 43,254KN. Isp: 469.5 sec. Burn time: 249 sec. Isp(sl): 346.7 sec. Diameter: 18.3 m. Span: 27.4 m. Length: 20.3 m. Propellants: Lox/LH2. No Engines: 1. Plug-Nozzle SERV
“SERV - A reusable single stage to orbit space shuttle concept” -- Tharratt, JBIS 1975, p. 3-25.