From: Scaled Composites
Posted: Sunday, October 3, 2004
The complex reason on why the rolling departure occurred will be described in a report we will post at a later date. What I am intending to do here is merely address some of the incorrect rumors about the rolls that have been seen in various news stories and web discussion groups.
While the first roll occurred at a high true speed, about 2.7 Mach, the aerodynamic loads were quite low (120 KEAS) and were decreasing rapidly, so the ship never saw any significant structural stresses. The reason that there were so many rolls was because shortly after they started, Mike was approaching the extremities of the atmosphere. Nearly all of the 29 rolls that followed the initial departure were basically at near-zero-q, thus they were a continuous rolling motion without aerodynamic damping, rather than the airplane-like aerodynamic rolls seen by an aerobatic airplane. In other words, they were more like space flight than they were like airplane flight. Thus, Mike could not damp the motions with his aerodynamic flight controls.
Mike elected to wait until he feathered the boom-tail in space, before using the reaction control system thrusters (RCS) to damp the roll rate. When he finally started to damp the rates he did so successfully and promptly. The RCS damping, to a stable attitude without significant angular rates was complete well before the ship reached apogee (337,600 feet, or 103 Km). That gave mike time to relax, note his peak altitude, and then pick up a digital high-resolution camera and take some great photos out the windows. Those photos are now being considered for publication by a major magazine.
While we did not plan the rolls, we did get valuable engineering data on how well our RCS system works in space to damp high angular rates. We also got a further evaluation of our Care-free Reentry capability, under a challenging test condition. As seen on the videos of the flight, the ship righted itself quickly and accurately without pilot input as it fell straight into the atmosphere. No other winged, horizontal-landing spaceship (X-15, Buran, SpaceShuttle) has this capability.
Some publications have stated that Mike defied a request to shut down the motor and let it run a few more seconds in order to reach 100 Km altitude. This is not true. While a Mission Control aerodynamist did discuss a possible abort a few seconds earlier, Mike immediately shut down the motor on the first advisory call over the radio. Mike himself was monitoring the apogee predictor during the initial rolls and was in the process of going for the thrust termination switch as he heard the advisory call.
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