SpaceShipTwo ascends to the edge of space during its latest test flight December 13. (credit: MarsScientific.com and Trumbull Studios)
by Jeff Foust
It was cold last Thursday morning in the Mojave Desert, but clear and calm: perfect weather for a spaceplane to fly to the edge of space at last.
By the time the sun peeked above the horizon at the Mojave Air and Space Port, final preparations for what Virgin Galactic hoped to be an historic flight were underway. VSS Unity, the second SpaceShipTwo, was attached to its WhiteKnightTwo carrier aircraft at the far end of the airport’s longest runway, with ground crews making one last set of checks. Further up the flight line, hundreds of people, mostly company employees and family members, gathered for the event, sipping coffee and watching a video screen.
At about 7:10 am Pacific time, the flight got underway. WhiteKnightTwo fired up its four jet engines and sped down the runway, leaving the ground by the time it passed by the crowd. With the aircraft ascending away from the airport, it would be 45 minutes to an hour until it was in position to release SpaceShipTwo on this latest test flight.
This flight would be the fourth powered flight for VSS Unity, and the eighth powered flight overall for the SpaceShipTwo program: the first vehicle, VSS Enterprise, was lost on its fourth powered test flight more than four years ago, claiming the life of co-pilot Michael Alsbury. The reason the company invited people to this flight was because, after years of development, and years of delays, this was the flight where they believed SpaceShipTwo would reach space—or at least one definition of it.
“I think you’re in for an amazing day tomorrow,” George Whitesides, CEO of Virgin Galactic, told a small group of reporters a day before the flight. Meeting at the company’s Final Assembly Integration Test Hangar, or FAITH, in Mojave, he and other company officials offered a preview of what they expected to unfold the next day. “It’s a day that we’ve been waiting for for a long time.”
The flight was an envelope expansion flight: burn the hybrid rocket motor a little longer, allowing SpaceShipTwo to fly a little faster and a little higher than before. On its previous test flight, in July, SpaceShipTwo burned the motor for 42 seconds, reaching a top speed of Mach 2.47 and an apogee of 52 kilometers.
“At a top level,” Whitesides said, “we’re going to be burning the motor a little longer than we have before. That should generate an apogee that is higher than we’ve had before.” How much higher? If the motor burned “into the 50 seconds” range, he said, the vehicle would be “approaching Mach 3—maybe a little under, possibly slightly over—and an apogees that could potentially be over 50 miles.”
That altitude, approximately 80 kilometers, is the one used by US government agencies—the Air Force, NASA, and even the FAA—for awarding astronaut wings, and it’s the one the company has used as the boundary of space, even though it’s below the Karman Line of 100 kilometers. “Under a nominal flight and a successful flight tomorrow, we could see the vehicle going over 50 miles,” he said.
But Whitesides emphasized this was a test flight, and there was no guarantee the flight would be nominal. “This is a test flight,” Whitesides said, “with all of the novelty and excitement and risk that goes along with a real test flight.”
He suggested the company was confident that the flight would be successful, given all the preparations it was making to invite people to witness yet. Yet, “the risk of a not-good day is still possible,” he said. Those “not-good” possibilities ranged from simply having to shut down the motor early, flying not as high as planned, to “other scenarios.” He didn’t elaborate about what those “other scenarios” were, but given that everyone was aware of what happened a little more than four years ago, he didn’t need to.
One difference about this flight is that the pilots of SpaceShipTwo would have some flexibility about how long to burn the motor. Earlier flights, Whitesides said, had a timer that burned the engine for a specific duration. “For this flight, we have given some amount of discretion to the pilot to see how long the rocket motor will be firing,” he said. But, he added, “we’re not going to get past the higher 50s” in terms of burn duration, in seconds, he said.
“The real limitation we’re shooting for is altitude,” said Mike Moses, president of Virgin Galactic. “The time it takes to get to that altitude is variable based on the trajectory that the pilot flies.” For this flight Virgin Galactic was trying a release at a slightly lower altitude—about 13,100 meters, more than 1,000 meters lower than previous tests—to see if the slight denser atmosphere would offer what Whitesides called “a little bit more bite” for SpaceShipTwo’s control surfaces as it made its sharp turn to the vertical several seconds after motor ignition.
So, as WhiteKnightTwo reached the release point for the flight, everyone was wondering how long the engine would burn: the longer the burn, the more likely it would exceed that 50-mile threshold. The crowd turned to the northern skies, spotting WhiteKnight Two’s contrail against the cloudless blue sky. “Thirty seconds,” called out Enrico Palmero, president of The Spaceship Company, the Virgin-owned company that built VSS Unity, who was providing commentary for the audience as they kept an eye on the sky as well as the video screen.
“Ten… five… three, two, one, release,” Palermo said. “Clear release.” The crowd cheered. “Motor firing.” The bright plume of SpaceShipTwo’s rocket motor was clearly visible from the ground, as well as its contrail as it zoomed away from WhiteKnightTwo and then turned to the vertical.
The crowd cheered with each announcement by Palermo of burn time and speed. “Mach 2, 40 seconds,” he called out to another round of cheers. “Mach 2.5, 50 seconds.”
The engine should now be about to shut down. “Fifty-five seconds,” he said. “Fifty-eight seconds. Motor shutdown.” The motor burned to the long end of expectations—a full 60 seconds, it later turned out. Would that be enough?
Now Palermo was giving altitude readings as VSS Unity, which flew to Mach 2.9, traded away that speed for altitude. There was more of a hush of anticipation over the crowd as he read out altitudes in increments of 10,000 feet and reported that the vehicle’s feathering system, needed for a safe reentry, had deployed as planned. “Two hundred and fifty thousand feet,” he said. “Two hundred sixty.”
The cheers were louder now. “Two hundred and six—” he said, halting in mid-sentence, to laughter. “Two hundred and sixty-four thousand feet,” he finally said: 50 miles. “Welcome to space, Unity.”
SpaceShipTwo ultimately reached an apogee of 82.7 kilometers. Then it started its descent, its feathering system keeping the vehicle stable through reentry. The rest of the flight went smoothly: the feather retracted, turning SpaceShipTwo into a glider that made a smooth descent back to the Mojave Air and Space Port. It landed a little more than an hour after takeoff, rolling to a stop near where the crowd was assembled on the flight.
The vehicle’s two pilots, Mark “Forger” Stucky and CJ Sturckow, emerged to a hero’s welcome from the crowd and company officials, including founder Richard Branson. “Today, for the first time in history, a crewed spaceship built to carry private passengers reached space,” Branson said. “This is a momentous day.”
“It was really amazing,” Stucky said on stage. “To actually get out there and have the motor shut down and go, ‘Huh, we’re going to space’ and see the dark sky was great. Everything just worked great.”
“It was a great flight,” he added after describing all the milestones they achieved. “We would have been happy a third of that.”
For Stucky, this was his first suborbital spaceflight. Sturckow, though, already had his astronaut wings from his career at NASA, where he flew four shuttle missions. What did he think of the flight? “It was a great flight, and I can’t wait to do it again,” he said.
SpaceShipTwo speeds away from WhiteKnightTwo seconds after being released from the airplane, as seen from the ground at Mojave Air and Space Port. (credit: J. Foust)
Sturckow and the other members of Virgin Galactic’s test pilot corps will get their chance to do it again in the coming months. Last week’s flight, while a milestone for SpaceShipTwo and Virgin Galactic, is not the last test flight.
The first order of business will be to analyze the data from this flight. Whitesides said in a post-flight interview that this process will take several weeks, into January. “Then we’ll fit that into prep for the next flight,” he said. “This was a huge step forward, and once we look at the data we’ll see what that pathway is.”
Whitesides, like other company executives in the past, avoided giving specifics on a number of test flights or schedule before beginning commercial operations. Branson, as usual, was not so reticent. “If nothing shows up that needs to be changed, then the next test flight could be quite soon,” he said, perhaps in a month or so.
He also expected that, if all went well, the company would need to fly only a few more test flights. At that point, operations would shift from Mojave to Spaceport America in New Mexico, where the company will operate SpaceShipTwo commercially. “Ideally, we want to do three more flights before we go to New Mexico,” he said.
He confirmed that he still planned to fly on that first commercial flight. “Sometime next year, once the testing is finished, then I’ll do my flight,” he said.
Those initial commercial flights will be flown by VSS Unity, but two more SpaceShipTwo vehicles are under construction. The first of those two, Palermo said in a tour of FAITH the day before the test, should be completed in about a year, with the second to follow three to six months later.
The new vehicles incorporate improvements in manufacturing over Unity. “We have a lot of lessons learned. Unity was the first thing The Spaceship Company built, and as a result of that we could really optimize how we build the next two spaceships,” he said, changes that include reducing manufacturing costs and well as the weight of the vehicles. “There is mass savings, and that’s mostly come about from refining the design to be more manufacturable.”
Branson said after the flight that the company would soon start work on two more SpaceShipTwo vehicles, as well as a second WhiteKnightTwo aircraft, which he said will be needed to start commercial operations.
Virgin Galactic current has about 700 customers who have purchased or made deposits on tickets. “We stopped for the last four years taking new people,” he said, a hiatus that dates back to the fatal SpaceShipTwo accident. Branson said that the company will soon start selling tickets again, although at perhaps a higher price.
“The price will go up in the short term,” he said, although he didn’t disclose by how much. “Then it will level and it will start to go down.” That decline would come some time in the next three years, he said, but again he declined to go into specifics.
The revenue from ticket sales will be welcome for Virgin Galactic. Branson estimated that Virgin had spent $1.3 to 1.5 billion on its space efforts to date, including $1 billion of Virgin’s own funding. (That figure, Whitesides said later, included smallsat launch company Virgin Orbit and The Spaceship Company, not just Virgin Galactic.)
Branson hinted he was looking for additional investors, particularly after the company cancelled a year-old deal in October with the Public Investment Fund of Saudi Arabia to invest $1 billion in Virgin’s space projects in the wake of the murder of journalist Jamal Khashoggi. “By being successful today, I suspect we’ll bring in other investors to help us take it on to the next stage,” he said.
Richard Branson speaks after the flight on stage with (from left) George Whitesides, Mark Stucky, and CJ Sturckow. (credit: J. Foust)
One area of controversy about the flight, at least among some observers, was about its claim to reach space. At an altitude of 82.7 kilometers, SpaceShipTwo fell short of the Karman Line, the altitude of 100 kilometers commonly used as a boundary of space. That boundary gained fame two decades ago in the Ansari X Prize competition, as vehicles competing for that $10 million prize had to reach that altitude to qualify for the prize. SpaceShipOne flew past the Karman Line on three flights in 2004, including the two needed to claim the prize.
More recently, the other commercial suborbital crewed vehicle under development, Blue Origin’s New Shepard, has regularly cleared the Karman Line, although so far without people on board. That included a flight in July that reached an altitude of nearly 120 kilometers, thanks to an additional boost to the crew capsule provided by its abort motor. (As this article was being prepared for publication, Blue Origin announced plans for its next New Shepard flight as soon as Tuesday, which would again aim to fly to an altitude of at least 100 kilometers.)
However, the SpaceShipTwo flight cleared the boundary of 50 miles, or about 80.5 kilometers, used by US government agencies to award astronaut wings. That includes the FAA, who, in 2004, awarded commercial astronaut wings to Mike Melvill and Brian Binnie for their SpaceShipOne flights that exceeded 50 miles—all of which also exceeded 100 kilometers.
After last week’s flight, the FAA announced that Stucky and Sturckow would also receive FAA wings. Bailey Edwards, FAA associate administrator for policy, international affairs and environment, said after the flight that the two would receive those wings at an event in Washington “in the new year.”
Even before the flight, some were questioning the use of the Karman Line as an appropriate boundary of space. In a November 30 statement, the Fédération Aéronautique Internationale (FAI), the international organization that maintains aerospace records, announced it was formally reconsidering the use of 100 kilometers as the boundary of space.
“Recently published analyses present a compelling scientific case for reduction in this altitude from 100 km to 80 km,” the FAI said in its statement. “FAI has therefore been in contact with the International Astronautical Federation (IAF) to propose that an international workshop is held during 2019 to fully explore this issue with input and participation from the astrodynamics and astronautical community.”
The statement didn’t identify the specific “recently published analyses” that led to that reconsideration. One, though, is likely a paper published in the journal Acta Astronautica by Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. That paper used a combination of analyses of satellite orbits and atmospheric modeling to conclude that 80 kilometers “is a more suitable choice to use as the canonical lower ‘edge of space’ in circumstances where such a dividing line between atmosphere and space is desired.”
McDowell gave an overview of that paper December 5 at the Eilene M. Galloway Symposium on Critical Issues in Space Law in Washington. “There is a fairly well defined boundary of space, and it’s not 100 kilometers,” he said, summarizing the technical analysis in the paper.
There’s also a historical issue with the boundary, he said. “As far as I can tell, von Kármán never wrote this down at the time,” he said, referring to Theodore von Kármán, the aerospace engineer after whom the Karman Line is named. “This is what we call in mathematics a ‘folk theorem.’”
McDowell noted that a 1963 book on space law by Andrew Haley went into the topic in some detail, but he set the line at 84 kilometers rather than 100 kilometers. “The idea that the Karman Line is, by definition, 100 kilometers is actually a rather recent idea,” he said, referring to another recent paper on the topic by Thomas Gangale.
The Karman Line also, for now, doesn’t carry much legal weight: treaties and many national space laws have avoided using that boundary, or other altitudes, as official demarcations of space for legal purposes. That could change in the future, though, McDowell noted, given both the rise of suborbital spacecraft as well as long-range hypersonic vehicles that may travel at altitudes around the Karman Line.
Some members of the UN’s Committee on the Peaceful Uses of Outer Space (COPUOS) have raised questions about setting an altitude definition for space. “Some delegations expressed the view that the lack of a definition or delimitation of outer space created legal uncertainty at the both the national and international levels concerning the applicability of air law and space law,” said Chris Johnson of the Secure World Foundation at the symposium.
“I’m agnostic as to what the legal community should do,” McDowell said, “but I think it should be informed by what the physics says.”
In the near term, then, what matters may not be the opinions of lawyers and scientists but the court of public opinion: does going to “just” 80 kilometers count as reaching space, or do you need to go to at least 100 kilometers? Or, perhaps, is neither altitude sufficient, and people will only consider going into orbit a real spaceflight?
The real problem is trying to set a discrete boundary on a continuum. There’s no physical discontinuity when crossing an altitude of either 50 miles or 100 kilometers in the atmosphere. Is a flight to an altitude of 101 kilometers—one kilometer above the current Karman Line—that much different from one to 99 kilometers?
Certainly there will be differences between the experience of a SpaceShipTwo flight that goes to a little more than 80 kilometers and a New Shepard flight that goes to a little above 100 kilometers: the latter will offer a bit more time in microgravity and a bit broader view of the Earth. Whether those will be significant differences, in the eyes of customers, remain to be seen. Other differences between the vehicles—one a spaceplane that is released from an aircraft and later glides to a runway landing, the other a vehicle that takes off vertically and returns by parachute—might end up being bigger differentiators. (Both, at least initially, will offer similar views, since New Shepard’s launch site in West Texas is not that far from Spaceport America in New Mexico.)
Unless and until a legal definition is established, the boundary of space will remain a fuzzy thing. While armchair astronauts will continue to argue on social media about specific boundaries, the real decisions will be made by those who develop suborbital vehicles and those who choose to fly on them.