We’re a sucker for anything that puts us in the cockpit of an exciting flight, and Virgin Galactic has kindly obliged. A day after the successful second test flight of SpaceShipTwo, the company out to define commercial space travel released a video combining a camera view out the tail showing the rocket motor plume, with audio from the test pilots during the 20-second powered flight.
The video starts while SpaceShipTwo is still attached to its mother ship, WhiteKnightTwo. Moments later it’s released, and a few seconds after that — with the nitrous-oxide flowing — the rubber-fueled rocket motor is ignited.
Scaled Composites test pilots Mark Stucky and Clint Nichols get an immediate kick into the back of their seats as the spacecraft accelerates through the sound barrier. The effect of the high g-forces can be heard in their strained voices and breathing.
The first thing we hear after ignition is the call “trimming.” The former Marine Corps and NASA test pilot Mark Stucky is adjusting the trim setting on SpaceShipTwo. This change is a small, incremental adjustment in the horizontal tail surface that removes some of the control forces needed to pull back on the stick — which on SpaceShipTwo is a stick with two vertical handles to further help with the forces. This allows the pilots to begin the pitch up and climb. Like most modern aircraft, to trim the airplane the pilot moves a switch on the control stick. For comparison, an airline pilot would also adjust the trim on an airplane to remove the force needed during the climb.
Moments before the 20-second rocket burn is completed, and in a stressed voice during the peak g-forces of the climb, Stucky mentions “lost…the…INS or something.” The INS is the inertial navigation system that provides a source of SpaceShipTwo’s location, independent of GPS or radio-based navigation instruments. It’s possible that during the high g-force loading there was some sort of electrical or other instrumentation problem that caused the outage.
A problem with the cockpit display happened during a SpaceShipOne test flight when a bad connection caused the entire instrument panel to go blank on test pilot Mike Melvill. During that flight, the information on the glass panel display returned as soon as the engine cut out and the g-forces were reduced. Of course, these kinds of issues are exactly why flight testing is performed with test pilots and engineers who can run the vehicles through just about every possible kind of scenario to find issues.
The peak speed reached during the flight was Mach 1.43 and an altitude of 69,000 feet. But that altitude isn’t reached until SpaceShipTwo “glides” upward for more than 30 seconds. During that unpowered portion of the climb there are some roll oscillations that can be seen in the video and immediately mentioned on the radio. Roll instability during the second SpaceShipOne X-Prize flight led to a series of rolls during the climb into space, so it’s something the Scaled Composites team is keenly aware of.
As SpaceShipTwo continues to climb, they pass through 65,000, then 66,000 feet, on their way to 69,000 feet. Next, the feather system is engaged which allows the twin tail booms to fold upward. This will be used during the re-entry process for the sub-orbital space flights and allows the spacecraft to reenter the atmosphere in a relatively simple and at a slow speed, keeping the process as easy as possible for the pilots.
As SpaceShipTwo descends in the feather mode, there is some oscillation until the tail returns to its normal position and the glide phase back to the airport begins.
Just before the end of the video, Stucky again trims the controls for the glide and hands over the controls to Clint Nichols who gets to log some valuable training time during the return to Mojave. Mission accomplished.