In 1997, Jeff Greason was an electrical engineer at microprocessor giant Intel in Oregon. A space enthusiast, he gave up his lucrative career for a startup with an uncertain future when he joined Rotary Rocket in Mojave as head of propulsion. Greason says that when Rotary shut down just two years later, a small group of engineers in the propulsion division came to their boss—him—and, in essence, asked him to keep the team together in a new venture. Aleta Jackson, Dan DeLong, Jones, and Greason (all still working together, 14 years later) decided that XCOR was a great name for a new rocket company; the “X” was inspired by the U.S. X-1 and X-15 programs.
The four started by working on small government contracts in propulsion. “Most of us didn’t get paid for a long time,” Greason says. In 2005, a NASA project for a methane-powered rocket engine gave XCOR a $3 million infusion. At about the same time, the Rocket Racing League hired the company to build a rocket-powered airplane called the X-Racer. United Launch Alliance tapped XCOR in 2009 to build and test a liquid hydrogen rocket that could serve as the upper stage of a satellite launcher. That work is ongoing. In 2008, the company began taking deposits on $95,000 Lynx flights to space. By 2012 a round of financing brought the company more than $5 million.
Greason says that XCOR has worked only on the technologies the company needs to develop for its primary business: creating launch vehicles. When those technologies can be used by a government or private customer, he adds, “we work with that organization to solve their problem, but we do it because it’s advancing the work on the tools we need to solve our problem. That’s the way we avoid becoming a we’ll-do-anything-for-a-contract sort of shop.”
Today, XCOR employs 50 engineers, machinists, and others to build and test rocket engines and develop the Lynx as a vehicle that can carry payloads as well as passengers. Sitting next to the pilot in the Lynx Mark II can be 265 pounds of anything that wants a ride to 328,000 feet—for an exposure to space and microgravity that is shorter than that available on most sounding rockets and, according to Greason, “orders of magnitude less in price.”
There’s a good reason that the Lynx flight profile has never been tried. Using an aircraft to get as high as possible before lighting its engines saves a rocketplane precious fuel and therefore weight. For SpaceShipTwo, the fuel savings translates into more payload—six paying participants plus two pilots, versus only one each for Lynx. For the X-15, the fuel savings translated into greater performance, allowing the craft to go hypersonic—past six times the speed of sound.
“The X-15 was designed for a different mission—speed—so it was optimized for that environment,” says Dennis R. Jenkins, coauthor of Hypersonic: The Story of the North American X-15. “Lynx is undoubtedly optimized for altitude.” Jenkins figures weight saved using modern materials and equipment—carbon fiber composites versus the X-15’s heavier nickel alloy, a several-ounce GPS receiver in place of a several-hundred-pound inertial guidance system, and so on—could help Lynx reach its target altitude without an air launch.
“There is no requirement for air launch to reach 100 kilometers altitude,” says Charles Miller, former senior advisor for commercial space at NASA and president of the NexGen Space consultancy. “Air launch has upsides as well as downsides. While there is a lot of engineering judgment, debate, and analysis about which path will ultimately be the best, nobody truly knows the answer.”
The method of launch is not the only significant difference between the two craft. SpaceShipTwo has a hybrid propulsion system, with a solid fuel core and rocket nozzle integrated into one single-use piece. Liquid nitrous oxide serves as the oxidizer, which the fuel needs to burn.
Virgin and Scaled have said that the hybrid fuel system makes their vehicles safer, since the solid fuel can’t light without the oxidizer. But it provides less thrust for its weight, contributing to the need for air launch. Between flights, the entire engine and solid fuel assembly have to be exchanged for another; by contrast, all the Lynx requires between flights is more fuel.
Jeff Foust is an analyst with aerospace consultancy Futron and a longtime observer of the suborbital spaceflight industry. “With SpaceShipTwo,” he says, “there’s probably enough touch labor involved with replacing that rocket motor core, putting a new solid fuel core in, and then of course refueling the liquid oxidizer tank that will not allow them to fly as rapidly as or as frequently [as] XCOR is able to do.” But he cautions that it is too early to predict which approach to suborbital flight will win. “Until they demonstrate their capabilities and the market reacts, we don’t really know which one is the right bet,” he says.
SpaceShipTwo achieved its first powered flight just a week after my visit to XCOR last April; the Lynx is months away from completion. For SpaceShipTwo, as in most spacecraft development programs, the pacing technology has been its propulsion system. But for the propulsion experts at XCOR, the engines aren’t a problem. One of the things holding up the Lynx is its cockpit.