Designed by XCOR engineers and being built by AdamWorks, a composite-structures company in Centennial, Colorado, the cockpit is a pressurized, carbon fiber vessel that fits inside the Lynx’s outer hull. Curved but not perfectly round, it has large openings for windows so that pilot and passenger can see the view. “Somehow you have to gather up all the pressure loads and carry them around the large openings,” says Greason. “That means there’s a lot of composite reinforcement in the parts that you do not look through.”
Although the cockpit is still being fabricated, the Lynx’s 3,000-pound-thrust main engine, designated the 5K18, is complete. Four of them will rocket the Lynx into space. The 5K18 test stand has two of the company’s signature piston pumps installed. The fuel pump built for the X-Racer has operated at twice its design pressure just to feed one 5K18 engine at a time.
A more recent pump design is a bigger blue and silver pump for the cryogenic liquid oxygen oxidizer, fed by insulation-wrapped pipes. Designed for the 5K18, it can run at reduced speed to feed a single engine or faster for two. Recently the team has run both fuel and oxidizer pumps for the first time in single-engine runs, satisfying the self-imposed requirement for all-piston-pump propulsion.
Three-time space shuttle astronaut Rick Searfoss is XCOR’s test pilot. He flew both of the company’s previous rocket-powered airplanes, and he’ll shake down the Lynx as well, starting with taxi tests and proceeding to progressively higher flights.
The first Lynx out of the hangar doors, a prototype dubbed the Mark I, has a planned ceiling of 200,000 feet—128,000 feet shy of the 100-kilometer (62-mile) Kármán line, which is the accepted boundary of space. A lightweight carbon fiber oxidizer tank in place of the Mark I aluminum tank should make it possible for the first production vehicle, the Mark II, to reach 328,000 feet.
On each vehicle, the flight experience for a paying participant will be nearly the same. Searfoss and the customer, who will sit in the right seat, will wear pressure suits for protection in case the cockpit is compromised in flight. After getting clearance from the tower at Mojave, the spaceplane—30 feet from nose to tail and 24 feet from wingtip to wingtip, about the size of the Bell X-1 rocketplane that carried Chuck Yeager past the sound barrier—will rocket down the runway, blasting out four jets of flame.
“For the pilot, it’s going to be a high-workload activity,” says Searfoss, but not, he adds, much different from that required of fighter pilots. He says the acceleration will be comparable to that of a F/A‑18 or an F-16 in full afterburner. While those jets take a few seconds to run up to full thrust, with the spaceplane, “the full performance is there…within a fraction of a second,” says Searfoss.
The Lynx will go supersonic within a minute of takeoff, pointing nearly straight up and accelerating through 2.5 Gs. Through the wrap-around cockpit windows, the pilot and customer will see the blue sky fade to black. After Searfoss flips the switches to shut off the engines, the ship will coast to the apex of the flight in silence. For three or four minutes, he and the customer will feel weightless.
With nudges of the control stick triggering split-second kicks from the 3N22 engines, Searfoss will nose the vehicle over to get the best possible views of Earth: blue ocean, open desert, mountains and clouds, the thin blue line of the atmosphere against the starless black daytime sky. The Lynx will return to its home airport as a glider.
Like Virgin before it, XCOR is taking its time getting to that first powered flight. The hope is to get the Mark I off the ground by the end of this year.