eAc is part of the SpaceShipOne team on the Tier 1 private manned space program for Scaled Composites. Scaled began designing concepts for sub-orbital manned spacecraft in 1996. In April 2001 an extensive development program began. Since that time eAc has designed and tested a new nitrous/HTPB hybrid propulsion system specifically for SpaceShipOne. Its unique cantilevered design simplifies mounting and reduces leak paths. The composite nitrous tank and case/throat/nozzle components were developed at Scaled, with Thiokol providing the tank's filament wound over-wrap, and AAE Aerospace supplying the ablative nozzle. eAc is competing with another vendor in the development of the propulsion system including fuel, bulkhead, controller, valve, injector, igniter and a ground test program. eAc's desiong for the fill and vent bulkhead for the nitrous tank has already been selected and will be used for all ground testing and flights.

SpaceShipOne is a three-place, high-altitude research rocket, designed for sub-orbital flights to 100 km altitude. The unique configuration allows aircraft-like qualities for boost, glide, and landing. The ship converts (via pneumatic-actuated 'feather') to a stable, high-drag shape for atmospheric entry. This configuration allows a hands-off reentry and greatly reduces aero/thermal loads. Designed for a 'shirt-sleeve' environment, the 60" diameter cabin has a space qualified ECS and dual-pane windows.

Propulsion Testing

Full scale ground testing has been conducted at the Scaled facility in Mojave, CA. An ongoing series of ground tests will be used to validate the motor system before it's use in flight testing. A mobile ground station is used to monitor all ground rocket motor tests and will serve as the base station for all flight tests. Flight test engineers receive real-time telemetered data for abort criteria monitoring & recording of performance parameters. A mobile tanker is used for servicing liquid nitrous oxide to the spaceship and to the Test Stand Trailer (TST) that is used for instrumented, ground-based hot fire testing of the rocket motor. All development firings use actual spaceship flight components including the nitrous tank and adjacent fuselage structure.

The motor is controlled by the eAc Flight Motor Controller (FMC), a compact 16-bit microprocessor housed in a custom milled enclosure with integral vibration isolation and relays. The controller is designed to intelligently monitor and respond to a number of system parameters indicative of potential hazards. A recorded status bit allows for post fire analysis of system conditions in the event of an automatic shutdown.

Extensive in house testing of sub-scale hardware for this project delivered smooth and consistent thrust levels over 10,000 lb and allowed for refinement of the system. The experiences of the south Florida testing allowed eAc to bring to Scaled a functional and proven system resulting in the efficient execution of the first successful static test for the Scaled project. The project is the culmination of all the resources and expertise eAc has acquired. The design represents the state of the art in nitrous oxide hybrid propulsion.

SpaceShipOne firing, iso view.mpg
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SpaceShipOne firing, main view.mpg
SpaceShipOne firing, 45 second.mpg
SpaceShipOne firing, full duration.mpg

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