Posted on 09/12/2003 4:52:25 PM PDT by Brett66
| Hybrid Rocket Motor for X Prize Entry SpaceShipOne Tested By Leonard David Senior Space Writer posted: 11:20 am ET 12 September 2003 |
A private space program has roared forward to another milestone.
At a Mojave, California test site, a hybrid rocket motor design that could boost Scaled Composites' SpaceShipOne to the edge of space was given a full-duration shakeout on September 4.
The propulsion unit was built by the Florida-based Environmental Aeroscience Corporation (eAc), one of two companies vying to be the engine of choice for SpaceShipOne. Competitor, SpaceDev of Poway, California, has also had its hybrid motor design undergo a full-duration run.
Reportedly, a Scaled Composites decision on which company's motor will power SpaceShipOne is near at hand. Performance data regarding the two different rocket designs is being closely guarded.
Suborbital flight plan
Aerospace maverick and head of Scaled Composites, Burt Rutan, has sketched out SpaceShipOne's flight plan. A suborbital hop of the craft has it first dropped by the White Knight (a turbojet launch aircraft) after the combined pair climbs for an hour to 50,000 feet. That places the two vehicles above 85 percent of the atmosphere.
SpaceShipOne is then released, dropping into glided flight. The vehicle's hybrid rocket motor fires, pushing the craft for more than a minute, reaching a speed of 2,500 miles per hour. The ship coasts up to 62 miles (100 kilometers) altitude, then reenters the atmosphere for a runway touchdown.
Goal of Rutan's private space program is to snag the $10 million X Prize, a worldwide competition that is spurring numbers of rocket teams to build suborbital, passenger-carrying space ships.
Hybrid motor details
SpaceShipOne's rocket motor is a hybrid, meaning it has characteristics that feature both solid and liquid rocket motors. The pilot uses simple controls to ignite the hybrid motor: two switches, one for "arming" the motor and a second to fire the engine. A dedicated propulsion display will show various critical motor parameters that can be monitored both by the pilot before launch and by a ground station during flight. The pilot has no ability to throttle the hybrid rocket motor.
Main components of the hybrid rocket motor -- the composite nitrous oxidizer tank and CTN (unitized motor case/throat/nozzle) have been in development at Scaled Composites since mid-2001. Those components passed their qualification tests by late 2002.
The other motor components (controller, valve, injector, aft bulkhead, head insulation, ignition system and fuel) are being developed and tested by the two competing subcontractors: eAc and SpaceDev.
According to Scaled Composites, due to the competitive nature of the rocket ground test program, details about engine performance is not being divulged. Once a vendor selection has been made, details about the rocket ground firings may be released.
Safe and simple
Hybrid motors are not new.
However, the configuration designed by Scaled Composites for SpaceShipOne is unique with its fuel case and nozzle cantilevered off the main oxidizer tank - forming part of the vehicle's aft fuselage. Rutan has applied for a patent given this new design. The hybrid motor's largest components, the oxidizer tank and fuel casing, have been fabricated by Rutan's company and made of composite structure.
The hybrid motor uses nitrous oxide (N2O or laughing gas) as an oxidizer and hydroxy-terminated polybutadiene (HTPB or rubber) as the fuel. Both of these can be safely stored without special precautions and will not react when put together.
Using nitrous oxide allows SpaceShipOne not to require complicated turbo pumps or plumbing to move the oxidizer into the combustion chamber.
To start a hybrid motor first requires introducing a significant source of heat into the fuel and then adding the oxidizer. A hybrid motor does not start by accident and, thus, it is a safe and simple alternative to its liquid and solid cousins.
The products of combustion are mostly benign (water vapor, carbon dioxide, hydrogen and nitrogen and some carbon monoxide) and are considered "more friendly" than any other class of rocket propulsion.
The rocket motor is partly re-usable. The oxidizer tank and the same fuel casing can support several short firings or one long one. The intent is to replace the fuel casing and nozzle between high altitude flights.
Shaded in mystery
In unveiling the private spaceship project on April 18, Rutan called the effort "the beginning of a renaissance for manned space flight."
"This might even be similar to that wonderful time period between 1908 and 1912 when the world went from a total of ten airplane pilots to hundreds of airplane types and thousands of pilots in 39 countries. We need affordable space travel to inspire our youth, to let them know that they can experience their dreams, can set significant goals and be in a position to lead all of us to future progress in exploration, discovery and fun," Rutan said.
Rutan remains guarded about the White Knight/SpaceShipOne flight test program.
The program appears to be marching along on a fast track at this point, including two glide flights of SpaceShipOne. Yet to be tested is an in-flight hybrid rocket motor firing. Rumors abound as to a target date for the first journey to the edge of space by SpaceShipOne. Insiders hint at a suborbital attempt that is timed with the 100th anniversary salute of the Wright Brothers flight this December.
Also shaded in mystery is the financial backer of the project. That person has yet to be identified, although one persistent name among several candidates is multi-billionaire, Paul Allen, a co-founder of Microsoft.
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