SpaceShipOne: A progress report
by Jeff Foust
|“In any event, we have a lot of analyzing to do,” Shane said of the third glide test flight.|
Included in the presentation was video from the most recent SS1 glide flight, which took place just three days earlier. There had been some interest in the flight because of rumors of problems during the flight involving a stall and uncontrolled roll. Shane noted that SS1, with pilot Mike Melvill at the controls and several hundred kilograms of ballast in the aft portion of the vehicle, started to stall shortly after release from White Knight. “What happened next was very unexpected,” said Shane. Melvill struggled to pitch the nose down to get out of the stall, and in the process the vehicle started to roll, as the SS1 external camera video clearly showed (see photo). “His roll trim was way out of trim to the right,” said Shane. “As soon as he recentered the roll trim, the airplane recovered.”
As soon as SS1 returned to stable flight the remainder of the test flight was cancelled, although Shane said that Melvill was still interested in continuing the planned test flight. What caused the stall and roll remain unknown. “In any event, we have a lot of analyzing to do,” Shane said.
Shane also mentioned a number of minor issues dealing with SS1 and White Knight. So far there has been little consistency in runway landing locations for SS1: while the first glide test flight landed as planned, the second landed long on the runway, requiring “moderate” braking to come to a stop before the edge of the runway, and the most recent test nearly landed short of the runway. On White Knight engine stability at high altitudes and low Mach numbers has become an issue—“anyone who has flown a T-38 probably could have told us that,” Shane said—resulting in several cases of afterburner blowouts and full engine flameouts.
Rutan took time during his portion of the talk to discuss the evolution of SpaceShipOne. Back in 1995, when the Proteus aircraft, a predecessor to White Knight, was still in development, one of its design requirements was the ability to carry a manned suborbital spacecraft. “The idea then was for Proteus to do a zoom maneuver to assist the spacecraft’s initial trajectory,” Rutan said.
By 1998 the design of the spacecraft had progressed, featuring a parachute that would slow the vehicle for landing. This design also featured “high-drag feathers” to permit a steep reentry and slow the vehicle high in the atmosphere, as well as the “carefree” stable capsule configuration during reentry. In 1999 Rutan eliminated the parachutes in favor of winged or lifting body configurations that would permit a runway landing. Those configurations used large deflected elevons and an “enormous” speed brake to reduce speed during reentry. (see photo)
The problem with those designs was flight stability. “All these designs worked well in subscale model tests, but CFD [computational fluid dynamics] analysis found that when the CG [center of gravity] was far enough aft to attain the adequate angle of attack at supersonic reentry, they were unstable for subsonic flight,” Rutan said. Fly-by-wire control systems could have solved the problem, he said, but he rejected them because of their high cost and low reliability. After experimenting with some “bizarre” designs, three years ago he hit upon the solution used in SS1: an articulated tail section that rises to a 60-degree angle during reentry and then returns to its normal position for subsonic flight.
|Rutan continued his policy of not talking about future plans or schedules for SS1, other than to show a concept for a larger version of the SS1 that could be used for space tourism flights.|
While Rutan was quite happy to talk about past developments in the program, he continued his reticence to talk in detail about the future of the program, including any schedule for additional test flights or a date for the first suborbital spaceflight for SS1. “While we’ve been out in the open since April, we do have a policy of not talking about future schedules, or specific things we’re going to do in the future,” he said. “We do show what we have done, though, immediately on the web site.” (However, as of press time, nearly one week after the third glide test, Scaled Composites had published no information about that test on its site.)
This, though, has not stopped speculation about when Rutan might attempt the first non-governmental manned suborbital flight. There have been a number of rumors suggesting that Rutan may attempt to make that flight in December, on the 100th anniversary of the Wright Brothers’ first flight. Speaking earlier last week at the AIAA Space 2003 conference in Long Beach, California, Matthew Ganz, president and CEO of HRL Laboratories (the former Hughes Research Labs), also stated that he felt Rutan could attempt a flight in December. Ganz is in some position to know: until recently he served on the board of directors of Scaled Composites.
Rutan also provided no new details about the cost of the SpaceShipOne project or his source of funding, other than to say that he did not start the project until he had obtained all the money he needed to finish it. Microsoft cofounder Paul Allen has been the person most widely named in the rumor mill as the source of the funding. This week’s issue of Newsweek offers some additional circumstantial evidence: the film company shooting a documentary about the flight is Vulcan Productions, owned by Allen.
Rutan did drop a hint about what he was thinking about doing after SS1. The final slide of the presentation, put on the screen during a brief question-and-answer session, showed what appeared to be a scaled-up version of the SS1 (see photo). A cutaway showed the cabin, with one pilot and ten passengers (arranged in three rows of three people with the tenth person floating above them.) The illustration was simply captioned “A Future Space Tourism Ride?”