Scaled Composites Completes Development For SpaceShipOne Rocket
Propulsion System
Four years ago, Scaled
conducted a study of rocket engine technologies that were
appropriate for its future manned sub-orbital spaceship design. The
results of this study were that a hybrid configuration using
nitrous oxide (liquid N2O) and HTPB (rubber) propellants would
likely provide the safest solution with operating characteristics
that would complement the intended mission.
In Jan 2000, Scaled defined a new integrated concept for the
hybrid motor that allowed the entire propulsion system to be
mounted to the spaceship by simple skirt flanges on the oxidizer
tank. This concept, which cantilevers the case and nozzle directly
to the tank, required an advanced all-composite design
approach.
By early 2001, Scaled had committed to developing the two main
motor composite components in-house: The first is the nitrous oxide
tank, a composite liner laid up onto titanium flanges, with a
graphite over-wrap provided by Thiokol. The second is a unitized
fuel case/nozzle component fabricated using a high-temperature
composite insulator with a graphite/epoxy structure laid up onto an
ablative nozzle supplied by AAE Aerospace.
In mid 2001, Scaled awarded contracts to two competing small
businesses for the "rocket science". Each company was independently
responsible for the development of the motor's ignition system,
main control valve, injector, tank bulkheads, electronic controls,
fill/dump/vent systems and fuel casting. The vendors, Environmental
Aeroscience Corporation (eAc) of Miami and SpaceDev (SD) of San
Diego, were also tasked with conducting the ground firing tests of
their motor systems in Scaled's test facility during the
development phase.
In June 2002, Scaled selected eAc to supply the components at
the tanks' front end: the nitrous fill, vent and dump system
components and associated plumbing. Both vendors continued the
development of all the other propulsion components.
The ground firing development program started in November 2002
with a 15 second run by the SpaceDev team and ended early this
month with a 90-second run by eAc. Both vendors demonstrated full
design-duration firings during the nine-month development phase.
All tests have exclusively used 100% flight hardware, with no
boilerplate components and both vendors' motor systems met the
contracted performance. The tests validated the inherent safety of
hybrid type motors, with no instances of structural failure,
hot-gas breach, explosion or other anomaly that would have put
SpaceShipOne in jeopardy.
Because both teams were
so closely matched, and since both have developed satisfactory
motors the process to select one of these vendors to enter the
motor qualification and flight test phase was difficult. However,
Thursday (9/18), Scaled announced that it has awarded the contract
for propulsion support for the SpaceShipOne flight test phase to
SpaceDev, of San Diego.
Scaled now looks forward to entering into the historic phase of
private manned space flight.
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