Virgin Galactic VSS Unity passes feather test
After successfully completing three glide-and-land tests at Mojave Air and Spaceport, Virgin Galactic conducted its first test of the “feather” mechanism on its second SpaceShipTwo (SS2) suborbital tourism spacecraft. This was the first successful test of SS2’s feathering system since a premature deployment of the system on the first vehicle caused it to break up in flight, killing one pilot and seriously injuring a second on Oct. 31, 2014.
Watch the birdie
After being released from the WhiteKnightTwo (WK2) carrier aircraft, VSS Unity folded its two tails upward to orient the spacecraft for the descent. In an operational flight from a suborbital altitude of 62 miles (100 kilometers), this configuration would increase Unity’s drag and aerodynamic stability without increasing heat loads tremendously. The effect allows SS2 to descend like a badminton birdie, with gravity guiding its center of mass downward.
Once the air is thick enough and heat loads have decreased, the twin tails drop to horizontal, and SS2 glides its way on regular aerodynamic control surfaces toward its runway.
Gabe Williams, the SS2 project engineer for the second vehicle, describes the process in Virgin Galactic’s online video: “Once we get to a slow enough speed, we’ll unlock the feather, and then when we’ve gotten to a high enough then the copilot will pull the feather handle. At that point, the feather will start to raise, but, in reality, the feather stays in the same position, and the cabin comes up, and then slowly the ship will pitch over. So if you’re watching [a] video of the cockpit during that time, you actually see the horizon change position as the feather comes up.”
For the May 1 test, with pilots Mike Stucky and Mike Masucci at the controls, SS2 Unity performed as expected, scissoring upward for several seconds before the feather dropped back into its regular position. Unity’s nose then drooped, and the spacecraft, now in aircraft mode, made a regular gliding descent and landing at Mojave. The aircraft has two rear landing gear and a skid up front, so it is towed to the hangar after landing.
What lies ahead
Unity still has more testing ahead before it makes its much-anticipated commercial debut. This was its fourth glide test, eighth flight overall. Virgin Galactic’s statement on the test stated: “Once data reviews are complete, we will move forward with our testing program—pressing onward with additional glide flights designed to expand our envelope of flight weights and centers of gravity.”
As to when commercial operations will start, that is still up in the air, so to speak. Virgin Galactic founder Richard Branson has made announcements concerning the first commercial flight in the past, most recently expecting one this year. According to Space News, he is now refraining from making any definitive announcements regarding SS2’s schedule. As noted in the Space News story, “I’ve made the mistake of giving dates before and being wrong.”
Virgin Galactic’s Chief Executive of Virgin Ventures (which includes Virgin Galactic) said at a February conference: “We have started the glide flight program, and we will continue that for the next few months, and then we’ll get into powered flight over the course of the year […]. We aspire to push far into the test flight program during the course of 2017.”
Video courtesy of Virgin Galactic
Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.