Virgin Galactic is preparing to fly the SpaceShipTwo rocket plane to the edge of space for the first time Thursday on a test flight that will mark a major advancement in the company’s long-sought ambition to begin regular commercial hops with space tourists.
The SpaceShipTwo vehicle, helmed by Virgin Galactic test pilots Mark “Forger” Stucky and Rick “C.J.” Sturckow, will take off from the Mojave Air and Space Port in California as soon as 10 a.m. EST (7 a.m. PST; 1500 GMT) Thursday under a specially-designed four-engine carrier jet.
The jet-powered mothership, named VMS Eve, will take nearly an hour to climb to an altitude of more than 40,000 feet (about 13,000 meters) over the Mojave Desert, where it will drop the SpaceShipTwo vehicle, christened VSS Unity. The rocket plane will free fall for a few seconds, then ignite its rear-mounted hybrid rocket motor to fire for up to 50 seconds, propelling Stucky and Sturckow to a target altitude of more than 50 miles (80 kilometers).
In a press release Tuesday, Virgin Galactic — founded by billionaire entrepreneur Richard Branson — said the company was entering a new phase of testing on SpaceShipTwo, an upsized commercial version of the SpaceShipOne rocket plane that won the Ansari X Prize in 2004, becoming the first privately-funded spacecraft to carry a human to space.
“During this phase of the flight program we will be expanding the envelope for altitude, air speed, loads, and thermal heating,” Virgin Galactic said in a statement. “We also plan to burn the rocket motor for durations which will see our pilots and spaceship reach a space altitude for the first time. Although this could happen as soon as the next flight, the nature of flight test means that it may take us a little longer to get to that milestone.”
The SpaceShipTwo pilots could command the craft’s rocket motor to shut down early in the event of a problem, cutting short Thursday’s test flight.
The rocket plane has a length of around 60 feet (18 meters), and a wingspan of 27 feet (8 meters). Once the rocket-powered portion of the flight is completed, VSS Unity will coast to its maximum altitude, then glide back to a runway landing at Mojave Air and Space Port.
VSS Unity is the second SpaceShipTwo vehicle to be built, following the loss of the VSS Enterprise rocket plane in a fatal crash in 2014 that killed Michael Alsbury, the craft’s co-pilot. Lead pilot Peter Siebold parachuted back to the ground after a harrowing fall from the stratosphere when VSS Enterprise lost control and broke apart moments after igniting its rocket motor on an atmospheric test flight.
Engineers blamed pilot error for the accident, which occurred after Alsbury prematurely unlocked SpaceShipTwo’s feathering system, twin tail booms that are used to re-orient the rocket plane and slow it down for descent back into the dense, lower layers of the atmosphere. While the pilots did not command the feathering system to engage, the air flow at the ship’s altitude forced the booms to rotate toward their re-entry positions, leading to the craft’s disintegration at an altitude of more than 50,000 feet.
The new SpaceShipTwo models, beginning with VSS Unity, have an added safety feature to prevent pilots from unlocking the tail fins too early.
Virgin Galactic, through it subsidiary The Spaceship Company, took over development and construction of subsequent SpaceShipTwo vehicles from Scaled Composites after the crash. VSS Unity made its first captive carry test flight underneath the VMS Eve mothership in 2016, followed by a series of unpowered glide flights and three rocket-powered tests beginning in April.
Once the test flight program is completed, Virgin Galactic plans to relocate operational SpaceShipTwo flights to Spaceport America facility in New Mexico. The SpaceShip company is building additional SpaceShipTwo vehicles to allow for a higher flight rate once commercial service begins.
Here is a list of the VSS Unity’s powered test flights to date:
- April 5: Apogee of 84,271 feet (25.7 kilometers); Top speed of Mach 1.87
- May 29: Apogee of 114,500 feet (34.3 kilometers); Top speed of Mach 1.9
- July 26: Apogee of 170,800 feet (52 kilometers); Top speed of Mach 2.47
SpaceShipTwo is designed to carry six passengers, along with two pilots, close to the boundary of space. Commercial flights of the vehicle are expected to fly to an altitude of at least 50 miles (80 kilometers). The U.S. Air Force and NASA awarded astronaut wings to pilots of the X-15 rocket plane who traveled to that altitude, but the Kármán line — the internationally-recognized boundary of space — lies at the 62-mile (100-kilometer) mark.
But there has been a recent push to redefine the boundary of space to the lower 80-kilometer mark, and the Fédération Aéronautique Internationale, the world air sports governing body, announced Nov. 30 that it will reconsider the location of the boundary, which is useful for keeping scorecards and determining who and what vehicles have flown in space.
“In the last few years there have been many scientific and technical discussions around this demarcation line for the ‘edge of space’ and variance around this as a boundary condition for recognition of ‘astronaut’ status,” the FAI said in a statement.
“Recently published analyses present a compelling scientific case for reduction in this altitude from 100 kilometers to 80 kilometers,” the statement continued. “These analyses combine data/modeling from a number of differing perspectives (latitudinal variations during solar cycles, theoretical lift coefficients for different size/configuration satellites ranging from cubesats to the International Space Station, perigee/apogee elliptical analysis of actual satellite orbital lifetimes, etc.) to a level that has never been done before in relation to this issue.”
The Kármán line is named for Theodore von Kármán, a pioneer in theoretical aerodynamics who co-founded the Jet Propulsion Laboratory.
The recent analyses of the boundary of space “also provide an accurate overview of some of the historical arguments and inadvertent misrepresentations of Kármán’s actual analyses and conclusions from over half a century ago,” the FAI statement continued.
The air sports governing body said it would organize a workshop with the International Astronautical Federation in 2019 to “fully explore this issue with input and participation from the astrodynamics and astronautical community.”
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1.