Rolling towards history
by Jeff Foust
|“I never felt uncomfortable,” Melvill said of the roll. “I thought it was kinda cool.”|
To pilot Mike Melvill, though, the roll was not a cause for concern. After the flight Melvill described how he calmly used SpaceShipOne’s flight controls and, later, its reaction control thrusters, to bring the roll to a stop. On several occasions he even called it as a “victory roll”, a description that initially confused some journalists, who thought it might have been an intentional maneuver.
Burt Rutan later noted that the roll rates during this time reached as high as 180 degrees a second, or a full revolution every two seconds. While that seems high, it’s less than many aerobatic aircraft routinely do. “I never felt uncomfortable,” Melvill said. “I thought it was kinda cool.” He even kept the engine going long enough to ensure SpaceShipOne made it beyond the 100-kilometer milestone, reaching a peak altitude of nearly 103 kilometers.
The initial analysis of flight data offered no clues why the vehicle started to roll at that point in the flight. Rutan, though, said that the role did not pose a safety hazard. “The airplane, when it was rolling, was going absolutely straight on,” he said. “We have an extremely robust system.”
While the cause the roll remains uncertain, both Melvill and Rutan took some of the responsibility for the event. Melvill suggested that he might have inadvertently stepped on a rudder pedal, triggering the roll. “I don’t think I made a mistake,” he said, but later conceded that “it was probably something I did.”
Rutan, meanwhile, noted that there is a “known deficiency on its flying qualities” in SpaceShipOne. The vehicle, he explained, is subject to what’s known in aerospace engineering as the “dihedral effect”: winds coming in to the side of the vehicle can create a roll. This effect had been seen in past flights, most notably the June 21 suborbital flight, when the vehicle pitched strongly from side to side as it encountered wind shear shortly after ignition. Rutan said that there was significant wind shear this time at around 60 kilometers altitude, but not strong enough to cause a roll itself.
|“The airplane, when it was rolling, was going absolutely straight on,” Rutan said. “We have an extremely robust system.”|
Both Rutan and Scaled’s pilots are familiar with vehicle’s tendency to roll, and have seen it during simulator runs. “We have never run though a full burn and flown up out of the atmosphere without rolling the airplane,” Rutan said. Melvill and the other pilots have, therefore, done extra training in other aircraft to practice dealing with rolls, as well as build up tolerance to the g-forces encountered during the flight.
Other than the roll, the flight was apparently trouble-free: Melvill called it “near perfect” just after landing. Rutan said there was nothing to fix on the vehicle: even the motor was in “beautiful shape” because it burned for less than the planned duration. The fairing on the underside of the vehicle by the rocket nozzle, which buckled on the June 21st flight, made it through Wednesday’s flight undamaged. The roll problem “will not affect the second attempt at all,” Melvill predicted.
His prediction appears to have come true. At the press conference Rutan said no decision had been made about when to fly “X2”, the second X Prize qualification flight. A tentative date of October 4 had been distributed by X Prize officials in the days leading up to the flight, but Rutan said they would make a decision by the end of the day Thursday about when the flight would take place, after a safety review of the X1 flight, Sure enough, late Thursday they announced the X2 flight would take place on the morning of October 4.
One major question is who will fly SpaceShipOne on X2. Unlike the June flight, when the pilot announcement was made at a press conference the afternoon before, there was no announcement made for the X1 flight until about two hours before takeoff. The selection of Mike Melvill was also something of a surprise: after the June flight, he had made it clear he was not interested in flying the vehicle again, preferring to let another Scaled test pilot—Brian Binnie or Peter Siebold—fly the X Prize flights, unless he was specifically asked to fly again.
When asked at the post-flight press conference about the pilot, Rutan quietly conferred with Doug Shane, Scaled’s flight operations director, for nearly half a minute before responding. “We got a big surprise about two weeks ago,” Rutan finally said, when one of the pilots fell ill and had to be hospitalized. While the unidentified ailment was less serious than originally thought, Rutan said the pilot told him that he was under enough stress from the illness to be less than 100% able to fly. Rutan did not identify who the pilot was, although he later said that Binnie was at the controls of the White Knight aircraft on Wednesday.
Just after landing, Melvill indicated that someone else would be the pilot for the X2 flight. “I don’t think I will fly the next flight,” he said during an impromptu press conference standing atop SpaceShipOne. Later, at the formal press conference, he hedged a bit. “I’d love to see someone else get a chance to fly it. They’re younger, with faster reflexes, and in many ways better than I am,” he said. “But, if no one else wants to fly, I’d be happy to do it.”
While Melvill has the most experience of Scaled’s pilots in powered test flights, project officials don’t see a disadvantage of switching to someone else for X2. “It’s always great to get the perspective of others,” said Shane. “There’s equal arguments to bringing the strength of all three guys into the program.”
|“If no one else wants to fly, I’d be happy to do it,” Melvill said when asked about flying SpaceShipOne again.|
Rutan also denied speculation that he himself would fly on X2 as a passenger. X Prize rules require vehicles to be capable of carrying three passengers, but ballast can be used to simulate the weight of two passengers. For the X1 flight much of the ballast came in the form of personal mementos provided by Scaled employees, ranging from tools to photos. (Rutan said before the flight that employees were required to sign an agreement to prevent them from turning around and trying to sell the items after the flight.) Something similar will be used for ballast for the second flight; Rutan said he would wait until the inaugural flight of the new Virgin Galactic service.
While Rutan will not fly on SpaceShipOne on Monday, a Rutan did fly on the vehicle Wednesday. At the press conference he revealed that the night before the flight he rounded up the ashes of his mother, who passed away during the development of SpaceShipOne, and included them on the vehicle for the flight. Clearly showing the emotion of the moment, he quietly said, “She flew today.”