- Parabolic Arc
- March 24, 2023
The Adventures of SpaceShipTwo: Inverted Flight, Wonky Gyros & an Impatient Billionaire
Nicholas Schmidle has an interesting profile of Virgin Galactic test pilot Mark Stucky in the New Yorker that sheds some light on what’s been going on at Richard Branson’s space company. I’ve excerpted some interesting passages below.
If you’ve been watching the videos of SpaceShipTwo VSS Unity‘s first three powered flights and thinking to yourself, Gee, it looks like that thing really wants to roll…well, you’d be right. Here’s an account of the first flight on April 5.
Stucky suddenly felt the wings tipping, as if the spaceship were about to roll upside down. “A little rolly there,” he said. He was straining to keep the wings level. He knew that he should abort—manually shut down the rocket motor—before he lost control of the spaceship. Entering a spin, or a tumble, at supersonic speeds would be hard to recover from. But, electrified by the ascent and believing that he could hold the spaceship steady, he let the motor burn.
A moment later, he felt the vehicle rolling even harder. “Ahhh! ” he groaned. The spaceship was slipping beyond his control. He commanded [David] Mackay to push the button that would instantly cut off the motor.
Mackay was leaning forward to do so when the rocket’s onboard timer hit thirty seconds; the motor automatically shut down.
Stucky got the craft under control and looked out his window. The Earth’s bright-blue surface filled his porthole. It was a stupendous sight: the outer edge of the atmosphere was dancing with wispy tendrils. The spaceship was now at eighty-four thousand feet—higher than he’d ever been. He could now testify to the awesome power of the “overview effect.” And yet, he suddenly realized, he wasn’t supposed to be looking down at Earth. This was the plan for tourist flights, but for this test the craft was meant to stay upright, allowing him to see only the blackness of space. SpaceShipTwo had somehow rolled over without his noticing.
“Oh, shit,” Stucky said. “The gyros are messed up.” For unknown reasons, they indicated that the spaceship was right side up.
“Totally,” Mackay confirmed.
Hurriedly, Stucky attempted to right the ship by blasting thrusters of high-pressure air, which was stored in the wings and was used to orient the vehicle in low-gravity environments. Then he instructed Mackay to unlock and raise the feather. As it went up, the spaceship righted itself, just as it had on Stucky’s harrowing glide flight seven years earlier. The same innovation that had contributed to the 2014 crash was, when properly deployed, a godsend.
The harrowing glide flight mentioned above occurred on Sept. 29, 2011, aboard the first SpaceShipTwo, VSS Enterprise. Stucky commanded the test with pilot Clint Nichols and flight test engineer Wesley Persall aboard. (At the time, all three of them were working for Scaled Composites, which built Enterprise.)
The goal was to test the vehicle’s tendency toward oscillations across the wing and the tail known as flutter. The vehicle entered a steep dive after separating from the WhiteKnightTwo mother ship when all hell broke loose.
But the engineers hadn’t fully accounted for such a steep angle of attack, and the tail lost lift; the spaceship suddenly flipped upside down and began spinning to the left.
Stucky counted each rotation as the plunging craft spun past the sun: One, two…
Stucky knew that he had to move quickly to slow the spin. He was falling five hundred feet a second. He deployed the speed brakes and stepped on the opposite rudder pedal, but the spaceship continued to tumble: Three, four…
He was out of ideas, preparing to open the hatch and parachute out, when something occurred to him. A decade earlier, when Rutan was designing SpaceShipOne, he’d been deeply concerned about the vehicle reëntering the Earth’s atmosphere askew and breaking apart. In 1967, a friend of his named Mike Adams had been flying the X-15 at Mach 5 when he lost control, and reëntered the atmosphere spinning sideways. This chaotic descent generated fifteen g’s, or fifteen times the force of gravity, and the plane was pulverized in midair. As a fix, [designer Burt] Rutan made his spaceship’s tail booms—flat panels that normally are parallel with the base of the fuselage—movable. When they were raised perpendicular to the fuselage, the craft slowed down and started descending like a shuttlecock. Rutan called his innovation the “feather.” In the documentary “Black Sky,” Brian Binnie, a former Scaled Composites test pilot, calls the feather “the angel’s wings on this vehicle.”
Stucky slid the feather handle to the “unlock” position, and raised the feather. The vehicle immediately stopped tumbling forward. Stucky regained control and glided to Earth. The angel’s wings had saved him, his co-pilot, and a flight-test engineer sitting in the back from almost certain death.
The full story of just how close the flight came to crashing was widely known in Mojave, but it didn’t make out into the press at the time. Those at the spaceport who witnessed this near disaster were bound by so-called Mojave Code — what happens on the flight line stays on the flight line.
The code allowed Scaled Composites and Virgin Galactic to downplay incident for the press. According to a Space.com story:
“Upon release, the spaceship experienced a downward pitch rate that caused a stall of the tails. The crew followed procedure, selecting the feather mode to revert to a benign condition. The crew then de-feathered and had a nominal return to base,” according to an updated flight log posted by Scaled Composites, builder of the WhiteKnightTwo /SpaceShipTwo launch system.
“Great flying by the team and good demo of feather system,” Scaled officials wrote in the flight log.
George Whitesides, Virgin Galactic’s chief executive officer and president, said the glide flight included a third seat flight test engineer onboard SpaceShipTwo for the first time. “A good capability for us to have for this phase of test,” he told SPACE.com. “Yes, apparently the tails exhibited stall characteristics in the test — which was a steep nose down maneuver.”
“Scaled is looking at the data now, but doesn’t anticipate any major issues,” Whitesides said. “This is why we flight test, to fully explore the aerodynamic flight envelope.”
No major issues or not, SpaceShipTwo didn’t make another glide flight until June 26, 2012 — nine months after the near crash.
Branson has struck a public attitude of nonchalance about whether Virgin Galactic or Jeff Bezos’ Blue Origin flies people to space first.
Branson said he expected that the companies would both “have a person in space roundabout the same time.” But he said they “are not in a race to get to space. … All that matters in the end is that everybody is safe and well.”
However, the New Yorker piece indicates the billionaire and company officials are concerned about possibly losing the commercial space race.
In April, 2015, after Blue Origin completed a successful test of New Shepard, its space-tourism rocket, [Virgin Galactic President Mike] Moses said to me, “I see that and go, ‘Crap!’ Because I look at their timeline and see that they have a good shot at beating us.”
By 2017, Unity was undergoing a series of glide flights in the lower atmosphere while Blue Origin was flying New Shepard to space.
The pilots began packing up, and Stucky read aloud a breaking-news item on his phone: Jeff Bezos had appeared at the Satellite 2017 conference, in Washington, D.C., to promote Blue Origin’s latest rockets. “I just keep waiting for them to announce that they flew humans to space,” [pilot C.J.] Sturckow said….
The company was pleased by its comeback, but Branson—who kept reading about rivals leaping ahead—was as restless as ever. In December, Blue Origin launched its New Shepard rocket-and-capsule configuration into space with a mannequin on board.
Around this time, Virgin Galactic weathered another series of setbacks. A technician accidentally damaged the bonding on SpaceShipTwo’s body with a blast of compressed air that he’d applied to remove drill shavings; repairs took weeks. Then the engineers discovered a problem with the horizontal stabilizers, or h-stabs, which are attached to the tail booms and control pitch and roll at supersonic speeds. One day, during ground tests, the h-stabs suddenly stopped working. It took months to solve the problem. In late December, Moses wrote a memo to employees: “We will not push blindly towards dates on a calendar. But I think you all can feel it, like I do, that the thing we all came here for—flying people to space from Spaceport America—is within reach.”