Page 10 - Aerotech News and Review, April 7, 2017

White Knights and starry skies: Toward commercial space travel
by Peter W. Merlin
special to Aerotech News
Visitors to the recent Los Angeles County Air Show at Fox Field in Lancaster, Calif., were treat- ed to a presentation by two test pilots from Vir- gin Galactic, the privately-funded space company owned by Sir Richard Branson’s Virgin Group and Abu Dhabi’s Aabar Investments PJS.
The Mojave-based project is currently devel- oping a vehicle to take passengers to the edge of space on a ballistic rocket ride ending with a gentle glide to a runway landing.
The commercial space venture kicked off in
and a liquid oxidizer, and climb above the atmo- sphere. In 2004, Rutan’s team won the $10 million Ansari X-Prize after SS1 soared above 328,000 feet, the internationally recognized boundary be- tween Earth’s atmosphere and outer space.
Using lessons learned from SS1 test flights, Scaled Composites designed and built Space- ShipTwo (SS2) to carry two pilots and six pas- sengers on brief suborbital flights. A new, larger mothership called White Knight Two was built to carry SS2 to launch altitude and provide pres- surization, air conditioning, and electrical power to the spaceship until launch time, about an hour after takeoff.
thermal protection. To slow its descent, the crew activates a feathering system that bends the wings and tail booms up into a shuttlecock configura- tion. “SS2 is the first full-size aircraft to use the feathering system,” Mackay said. “It’s the first vehicle flown that can fold itself in half and then unfold to return to normal flight.”
At lower altitudes, the vehicle returns to normal configuration, pitches down into a steep dive, and maneuvers for a glide landing on a conventional runway. In keeping with the concept of a routine commercial operation, the cabin is a fully pres- surized “shirtsleeve” environment; neither pas- sengers nor crew require pressure suits at any point from takeoff to landing. Even during the experimental phase of the project, the crew wears only ordinary cloth flight suits. This, according to SS2 lead test pilot Mark “Forger” Stucky, is because the designers have supreme confidence in the vehicle’s structural integrity. “The airframe has been tested to well beyond the load limits we would expect to see during flight,” he said, “there is a great deal of structural redundancy.”
A former military and NASA research pilot, Stucky joined Scaled Composites in 2009 for the White Knight Two and SS2 development programs as an engineering test pilot, technical adviser and design engineer. He flew the majority of SS2’s envelope expansion flights including the first powered flight. He also served as project pilot and instructor during the transition and integration of White Knight Two from Scaled Composites to Virgin Galactic’s commercial operations team, and joined Virgin Galactic as a pilot in February 2015.
Initially, Scaled Composites had full respon- sibility for the flight-test program. The first SS2 vehicle, dubbed VSS Enterprise, was flown for the first time unpowered in October 2010 by test pilots Pete Siebold and Mike Alsbury. Over the next four years, the team performed more than 50 airborne tests including and 19 captive carry flights, 30 glide flights, and three rocket-powered flights. Mission goals were designed to test the vehicle and its systems incrementally through performance envelope expansion. Although ex- perimental in nature, VSS Enterprise was not considered a developmental prototype. “One of the interesting challenges,” Stucky noted, “was that we have are building a flight-test vehicle that
The twin-hulled White Knight Two mothership carries SpaceShipTwo to altitude for a glide test flight.
Photograph courtesy of Virgin Galactic
According to Virgin Galactic chief pilot David Mackay, the force of the rocket will subject passengers to approximately 3.5g — roughly equivalent to the acceleration of the most powerful drag-race car — for a full minute. “Launch is hori- zontal, but as soon as the motor begins providing thrust, we pull up into the vertical,” said Mackay. At engine shutdown, SS2 will be moving at more than three times the speed of sound and when the mo- tor shuts off, the
Photograph by Peter Merlin David Mackay is Virgin Galactic’s chief pilot.
is designed to go into operational service.”
The project received its most serious setback in October 2014 when VSS Enterprise, again piloted by Siebold and Alsbury, broke apart at an altitude of around 50,000 feet during the fourth powered flight. When the craft disintegrated, Siebold was thrown clear while still restrained in his seat. Despite being exposed to sudden decompres- sion, extreme g-forces, chilling temperatures and being battered by debris, he somehow released himself from his seat, and his parachute deployed automatically at around 20,000 feet. Alsbury per- ished and was found in the wreckage. The debris field stretched more than 30 miles from the city of Ridgecrest to the rural community of Cantil. A subsequent investigation revealed that the co-pilot had inadvertently unlocked the feathering mecha-
nism too soon.
Branson vowed to continue the project, with
improved safety measures, and responsibility for further testing was given to Virgin Galactic.
A second SS2 vehicle, VSS Unity, became the first such craft built entirely by The Space- ship Company, Virgin Galactic’s manufacturing arm. VSS Unity completed its first flight suc- cessful glide test in December 2016, and by early March 2017 four captive-carry and three glide tests had been completed. Stucky noted that the test team was building on the previous work to maximize the value of each test flight. “One of the most unusual things we’re doing this time around
See VIRGIN, Page 11
2001 when Scaled Composites of Mojave, Ca- lif., began development of the first privately developed manned space vehicle. Designed by Burt Rutan, SpaceShipOne (SS1) was a rocket- powered craft carried aloft beneath a mothership airplane called the White Knight.
Following release at an altitude of 47,000 feet, the SS1 pilot would ignite a hybrid rocket engine fueled by a combination of solid rubber propellant
spaceship’s occupants will experience weight- lessness.
At that point, Mackay said, the passengers will be able to unstrap and float about in zero grav- ity. To maximize the experience, the cabin was designed with a lot of windows that will provide spectacular views of the curvature of the Earth, the thin blue band of atmosphere, and the black- ness of space. Additionally, he said, “The seats will be fully reclined to maximize cabin volume and allow the passengers to do somersaults in
Photograph by Peter Merlin Mark “Forger” Stucky is the lead test pilot for SpaceShipTwo.
zero-g.”
When the spaceship
reaches its apogee, at about 328,000 feet, it will start to descend. Passengers will return to their seats, which will remain in the reclined position to absorb re- entry forces up to five times Earth’s gravity. At about 70,000 feet, the vehicle’s configuration changes in a unique way.
When it gets back down to 70,000 feet, the spaceship changes from the feather-shape it has adopted for the drop, back into a glider to make the landing. Unlike previous space vehicles that were made of metal alloys covered with special heat-shield- ing material, SS2 is built from carbon-fiber com- posites with virtually no
Photograph courtesy of Virgin Galactic The first SpaceShipTwo vehicle, VSS Enterprise, climbs during its second powered flight.
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