I can feel the heat from the rocket engine through my jeans, as well as the vibration of the shock wave. The sound is like a punch; because I’m wearing protective headphones, I feel it more than hear it. It lasts all of half a second, but in that instant, the air seems to split open and release a primordial force. The flame shoots three feet through the air in the XCOR Aerospace rocket shop in Mojave, California—a long, orange-yellow tongue flicks from the burnished aluminum nozzle bolted to the test stand, and is gone.
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The pint-size engine, its nozzle just a hand’s length, kicks with the force of 40 pounds. The test stand is itself no larger than a tea cart. Mark Peck, the engineer who pressed the red button to fire the engine, sits beside it, only about a foot or two away. He dialed in the duration of the test on an old-fashioned rotary telephone dial that XCOR gadgeteers had rigged to the test stand.
Twelve of these engines, designated 3N22, will go on the spaceship that’s coming together elsewhere on the shop floor. Six of them will give the pilot pitch, yaw, and roll control at the apex of the ship’s suborbital flight, outside the atmosphere, where aerodynamic flight controls have no effect. Six more are backups, there in case something goes wrong with any of the first six.
XCOR’s spacecraft, the Lynx, is being built to carry a pilot and a single passenger on a trajectory similar to that of the bigger, eight-seat SpaceShipTwo, built by Scaled Composites for Virgin Galactic, just down the flightline from XCOR’s hangar at the Mojave Air & Space Port in California. Both companies aim to give space adventurers and researchers the experience of weightlessness in a black daytime sky with a view of the curving Earth below. But unlike SpaceShipTwo and its historic predecessor, SpaceShipOne—the first private manned vehicle to reach space—the Lynx will take off directly from a runway under its own rocket power, without the benefit of a carrier aircraft to take it to high altitude before launch.
The Lynx flight profile has never been done—not by others hoping to break into the space tourism business and not by the X-15, a rocketplane developed by the Air Force and NASA that flew to suborbital space in the 1950s and 1960s. The Lynx will follow a different path to space not because the XCOR engineers want to do something no one has done before but because they have a different goal from those of the makers of SpaceShipTwo and the X-15. XCOR’s goal is orbit, and the Lynx is just one step along the way.
“Part of our business strategy was to start with what we thought an orbital vehicle would look like, and we wanted the suborbital vehicle to path-find the suite of technologies that we knew we’d need for an orbital system,” says XCOR CEO Jeff Greason [pronounced GRAY-son]. The company’s founders studied the rocket performance that would be necessary to create a two-stage, orbital launch system. “That same level of performance gives you a suborbital-class vehicle that needs only one stage,” Greason says.
XCOR’s business goal is to reduce launch costs enough to win customers who want to put payloads into orbit. In this, the company is like the now-celebrated SpaceX, started by millionaire Elon Musk when his dreams of traveling to Mars were dashed by the high cost of getting to Earth orbit. XCOR is what a rocket company looks like when the founders don’t start out with $100 million from the sale of an Internet service.
Doug Jones, one of XCOR’s founders and the engineer in charge of the test, stands at a taller cart on the other side of the rocket. He takes off his earphones and scans the data that has appeared on the LCD before him. The engineers are trying to determine the minimum amount of helium needed to completely purge the nozzle of residual propellant between firings. They set up for another test.
Jones is one of four engineers who founded the company in 1999, veterans of a Mojave rocket startup, Rotary Rocket, that went bust. They had all worked in Rotary’s propulsion division. Since starting XCOR, they have fired 12 rocket engine designs a total of more than 4,000 times without a single, in the euphemism of the trade, hard start. In other words, they’ve never had an engine blow up.
After showing they could make engines, the XCOR team turned to fuel pumps. They were interested in piston pumps because, compared with the turbopumps that traditionally pressurize fuel and oxidizer for rocket engines, piston pumps are cheaper to design and build, and they last longer. The life of a turbopump is measured in minutes; a piston pump will work for hundreds of hours. The Defense Advanced Research Projects Agency was interested too, and funded some of XCOR’s piston pump research.
“Larger rocket engines are really only needed and used for high-thrust and long-duration maneuvers like launch,” says Preston Carter, the former DARPA program manager who funded XCOR’s piston pump development. For commercial suborbital tourism and eventually commercial launch systems, he says, XCOR’s small, higher-performance rocket engines and piston pumps will be in demand.
XCOR is the first to use piston pumps for space applications. For a small company trying to foster routine, airline-style operations for spaceships, they offer the key advantage of affordability, and because of how XCOR began, affordability is a major part of its business plan.