SpaceShipOne makes history — barely
by Jeff Foust
|The contrail went straight up, bisecting the Sun, forcing the crowd to squint and awkwardly block the Sun to see the contrail.|
For the next hour the anticipation grew as White Knight and SpaceShipOne, monitored by several chase planes, flew into position. The crowd scanned the skies, trying to track the progress of the vehicles, while listening to reports broadcast on loudspeakers. (In many locations, though, including portions of the media area, the loudspeakers were inaudible.) KLOA, a local radio station providing live coverage of the flight, broke away several times for commercials, news, and country music, much to the aggravation of those listening for information about the flight.
Then the moment finally came. For those out of earshot of the loudspeakers, the first indication that SpaceShipOne has separated and fired its engine was the appearance of a contrail in the eastern sky, just below the Sun. The contrail went straight up, bisecting the Sun, forcing the crowd to squint and awkwardly block the Sun to see the contrail. The contrail streaked up for over a minute, giving the crowd every indication of a successful flight. Within a few minutes, the contrail had dispersed, leaving no evidence that a flight into space had taken place.
For about the next half hour, the crowd again scanned the skies, looking for SpaceShipOne and its chase planes. At the same time news and rumors spread about the flight: yes, it had reached space, barely, but there had been some unspecified “anomalies”. The problems didn’t seem serious at first, and SpaceShipOne glided to an uneventful landing at the airport, to the cheers of the crowd. A short time later SpaceShipOne was towed to a position directly in front of the media and VIP viewing areas; Melvill then exited the vehicle, thrusting his arms skyward, and was embraced by Rutan. In brief comments to the assembled media, Melvill noted that it had not been a trouble-free flight, but it was successful nonetheless. Only later, after Melvill climbed atop SpaceShipOne for another victory salute and a trip down to the public viewing area, did it become clear how close to failure the flight had been.
At a press conference about two hours after landing, Rutan and Melvill provided reporters with details about the flight and what went wrong. The first problem took place as soon as the engine was lit: SpaceShipOne rolled 90 degrees to the left. Melvill then “stomped” on the rudder pedals, and the vehicle then rolled 90 degrees to the right. “It’s never ever done that before,” he said. “At that point, I was kind of reaching for the switch to shut it down, because I was going to lose control.” However, he was able to right the vehicle and bring the nose up to the proper level of climb.
This “roll off” had been seen before to a much lesser degree on previous flights—Melvill said that he had about a 30-degree roll to the left on the previous flight last month—but the cause is uncertain. “I don’t think it was my inputs that caused that problem, but it is possible,” he said. “I might have stepped on the rudder pedal or caused a mistake that caused it to roll.” He did note that when the engine fired up he felt an acceleration of 3g “eyeballs in” and 4g “eyeballs down”, a combination that he described as “very, very disorienting.”
|The “roll trim” problem appears to have been caused by the failure of an actuator that moves the stabilizers, according to Rutan.|
After that glitch, though, the powered flight went according to plan up until near the end. At that point, Melvill said, “I tried to trim the nose up a bit more to just get a little more height, and that’s when I had the anomaly with the trim system.” That problem caused the vehicle to roll, sending it over 30 kilometers off course in just five seconds. The problem also kept the vehicle from reaching its planned peak altitude of nearly 110 kilometers. Melvill said that he switched to an unspecified backup system and was able to restore control of the vehicle.
The “roll trim” problem appears to have been caused by the failure of an actuator that moves the stabilizers, according to Rutan. In supersonic flight, moving the elevons alone doesn’t provide enough control; in those conditions, Melvill said, “you can no longer move the stick, it’s like it’s welded to the airplane.” In that environment, the entire stabilizer is trimmed using actuators. If the two stabilizers get out of sync, Rutan said, “you’re out of control in roll.” That suggests to Rutan that one of the actuators failed during the flight. “We believe we lost one of those trim actuators, like it became inoperative, which means that when we tried to trim and pitch, we got a lot of roll going.”
Then there is the issue of the mysterious bang. During his brief comments shortly after landing Melvill reported hearing an odd, disconcerting bang during the flight, but was uncertain as to its nature. At the same time a large dent—perhaps 30 centimeters across—was visible on the underside of the fuselage, near the rocket nozzle in the rear of the vehicle. The buckling of that piece of the fuselage appears to be the source of the noise heard by Melvill.
Rutan explained that the piece that failed is a fairing that covers the underside of the motor. “This fairing had never flown before,” he said, because this was the first flight of a larger nozzle designed for operation at higher altitudes. He emphasized that the piece was not critical to the flight. “It wouldn’t put the ship in jeopardy if the whole thing fell off,” he said. “It’s there to give us a little less drag, and the ship looks a lot nicer, too, with that fairing on.” What caused the fairing to buckle remains unclear, but Rutan said it had nothing to do with the other problems experienced during the flight.