FAQ: SpaceShipOne & White Knight
Q: How long had Burt been working on all this?
A: The concept dates back to April 1996. Design work and some limited testing started in 2000. The full development program began in May of 2001.
Q: What’s going to be next in Burt’s bag of tricks?
A: Scaled has completed 34 manned research aircraft. None were announced until they were ready to fly.
Q: When did the first X PRIZE flight take place?
A: The first flight was scheduled for September 29, 2004.
Q: How much will it cost to get a ride into space?
A: Rides are not offered in SpaceShipOne. The price of a ride takes into consideration the cost of certification and establishing an airliner-like operation. One goal of this research program was to see how low the cost might be without the burden of regulatory costs.
For more information on rides into space, please visit www.virgingalactic.com.
Q: Was it physically stressful?
A: It is on the order of some modern theme park rides. The highest forces occur during re-entry, but build up gradually and peak above 5 G’s for less than 10 seconds. With the pilot and passengers reclined, these forces are quite tolerable for anyone in reasonable health.
Q: Why did the 1st flight last only 2 minutes?
A: The airplane had outboard spoilers on the wings to help improve roll control in the event of gusty crosswind landings. They were pneumatically actuated (using the same tanks, valves and fittings as the RCS system on SpaceShipOne) and returned to recesses in the wings by springs. On the first flight, the low air pressure at rotation was sufficient to “suck” the spoilers out which killed the lift and caused the return springs to slam them closed. Four of these surfaces chattering out on the wingtips during the climb out produced significant airframe vibrations and the pilot elected to turn downwind and land immediately rather than aggravate the condition any longer than necessary. The spoiler system has since been disabled, since the ailerons provide adequate control.
Q: How can you see where you’re going?
A: The visibility is actually much better than you might imagine. By moving your head slightly you can piece together an acceptable picture of the outside world and maintain adequate “situational awareness.” What is more difficult is spotting other airborne traffic. However, between radar advisories from ground controllers and an onboard traffic alert system, this limitation is minimized.
Q: Isn’t it hard to land with all those wheels?
A: No. The pilot doesn’t notice that he has two nose wheels up front and with excellent elevator control he can hold them off until about 45 knots during the landing roll.
Q: Why is the cockpit called a “pressure vessel”?
A: The cockpit is airtight and the air is not freely exchanged with the outside air. So, like a submarine, the structure must be able to withstand large forces due to the pressure differential. In the case of this vehicle, there is high pressure air inside compared to the near vacuum outside.
Q: How do you keep the air breathable?
A: There are three components to keeping the cockpit environment suitable for flight. One, oxygen needs to be added at a small rate for that used by breathing. This is done with a small bottle carried in the cabin. Two, the carbon dioxide from the exhaled air needs to be removed and this is done by using an absorber system. Finally, the humidity is controlled by passing the air through another absorber material that removes water vapor, keeping the cabin cool and dry.
Q: Have there been any surprises during flight test?
A: Right from the start the White Knight has been one of Scaled’s best handling aircraft. It has good control harmony and is surprisingly responsive for a large airplane. Despite its high wing, the airplane’s dihedral effect (being able to pick up a wing with rudder only control) was too low and, therefore, angled winglets have been added.
Q: What’s with all those funny windows?
A: The windows must be small to keep the weight of the vehicle down and they must be round to minimize the structural loads. This configuration is also the least expensive to manufacture. Each portal consists of two windows to provide redundancy for the integrity of the pressure vessel should one window crack or fail. The number and location of the windows were selected to provide the pilot a view of the horizon throughout SpaceShipOne’s mission profile.
Q: How high did you go?
A: The goal was to get to 100 kilometers or about 62 miles up. This altitude was established by the X PRIZE foundation as a target to stimulate commercial interest in the technology to achieve it. Both Mike Melville’s and Brian Binnie’s flights surpassed this goal in 2004, winning the $10M Ansari X PRIZE.
Q: Why do you “fold” the wings to come back down?
A: In space, the wings are folded up to provide a shuttle-cock or “feather” effect to give the ship extremely high drag for re-entry. This allows the re-entry deceleration to occur at a higher altitude and greatly reduces the forces and heating on the structure. Also, the ship in the feathered configuration will align itself automatically such that the pilot has a less-critical flight control task. We refer to this as “care-free re-entry.” The atmosphere orients the vehicle to a belly-first attitude without pilot input. Another benefit is that since the altitude is higher, the pilot can glide further after the entry deceleration. A SpaceShipOne pilot can glide more than 60 miles after he converts back to the non-feathered glider shape.
Q: Why isn’t the pilot in a space suit?
A: You can think of the design of the cockpit with its dual seals and window panes as essentially a space worthy cockpit surrounded by a second outer space worthy shell. This redundancy eliminates the need for a space suit and allows the crew to operate and test the vehicle in comfort knowing that any major single failure will not result in loss of cabin pressure.
Q: What pilot qualifications were required to fly it?
A: Scaled’s pilots come from a variety of backgrounds and experiences. It is the training provided by in-house assets and program-specific resources that provided confidence in our ability to fly the space ship. This training included glide approaches in our twin engine Duchess, acrobatic and unusual attitude training in an Extra 300, a sophisticated simulator with tailored flight displays for each distinct phase of flight and finally, the in-flight exposure to the same cockpit environment provided by the White Knight aircraft.
Q: How did the pilot control the rocket motor?
A: Rocket controls are very simple. Two switches: one to Arm it and a second to Fire it. The avionics suite had a dedicated propulsion display that showed various critical motor parameters that could be monitored both by the pilot before launch and by a ground station during flight.
Q: Could the pilot throttle the rocket?
A: No. There was no provision for the pilot to modulate the rocket thrust.
Q: Has any other vehicle gone supersonic with manual flight controls?
A: Yes. Chuck Yeager’s “Glamorous Glennis” or the Bell X-1 had manual flight controls. Like SpaceShipOne it also had electric trim for supersonic flight. SpaceShipOne may have been the first supersonic aircraft that was not developed by an Aerospace Prime.
Q: Did you do wind tunnel testing?
A: No. All design refinements and performance predictions have been derived from Computational Fluid Dynamic tools.
Q: Why is it called a hybrid motor?
A: It is called a “hybrid” because it has characteristics that utilize features from both solid and liquid rocket motors.
Q: Who designed the rocket motor?
A: While hybrid motors are not new, the configuration designed by Scaled for SpaceShipOne was unique with its fuel case and nozzle cantilevered off the main oxidizer tank, which in turn, formed part of the vehicle’s aft fuselage. Burt applied for a patent for the new configuration. Its largest components, the oxidizer tank and fuel casing, are Scaled-designed composite structure. The development and testing of the rocket hardware - injectors, valves, controls, ignition systems and fuel characteristics - was done by two competing, independent rocket companies, eAc and SpaceDev.
Q: What’s the deal with laughing gas and rubber?
A: All rocket motors have some form of “fuel” and an “oxidizer.” In solid rocket motors the oxidizer is embedded into the fuel (like an Estes rocket motor) and when lit will burn until depleted. In liquid rockets the oxidizer is usually liquid oxygen and the fuel another liquid like hydrogen or kerosene. In our hybrid motor we used 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. Finally, N2O has the nice quality of self-pressurizing when at room temperature so that the space ship didn’t need complicated turbo pumps or plumbing to move the oxidizer into the combustion chamber.
Q: How do you start it?
A: To start a hybrid motor first requires introducing a significant source of heat into the fuel and then introducing 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.
Q: Does it pollute the atmosphere?
A: The products of combustion are mostly benign (water vapor, carbon dioxide, hydrogen and nitrogen and some carbon monoxide) and certainly much more friendly than any other class of rocket propulsion.
Q: Is the rocket re-useable?
A: Partly. The oxidizer tank is reusable 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.
Q: How did you validate the simulator?
A: The simulator is based on CFD analysis and updated by flight test data. Since the space ship is first flown as a glider, it will provide the opportunity to iterate the subsonic aero characteristics before the powered supersonic flights.
Q: Does it simulate stick forces?
A: Not in real time. We are able to change the stick force gradients to simulate different flight regimes. Thus we can practice flying with a “heavy” stick for supersonic conditions and a lighter one for the glide landing return.
Q: Can you rehearse normal and emergency procedures?
A: Yes. The cockpit has most of the functionality of the actual vehicle. Emergencies and faults can be introduced by a console operator.
Q: Who developed the controls and displays?
A: All of the controls and displays were developed in-house and reflect many iterations and fit-ups in the simulator as well as in-flight assessments during White Knight flights.
Q: How do you simulate rocket accelerations and weightlessness?
A: We don’t attempt to do this in the ground based simulator, but we are able to expose the pilots to most of the expected flight envelope from flying the White Knight and the acrobatic Extra 300.
Q: How can I get more technical information?
A: The April 21, 2003 issue of Aviation Week & Space Technology magazine is an excellent source.
Q: How can I send fan mail and well wishes to the SpaceShipOne team?
A: Use our online contact form or use our mailing address:
Scaled Composites, LLC
1624 Flight Line
Mojave, CA 93501