by Douglas Messier
Parabolic Arc Managing Editor
XCOR’s advanced rocket engines will allow for daily flights into suborbital and then orbital space during this decade, investor Lee Valentine said on Saturday.
Valentine gave a fascinating talk during the Mojave Air and Space Port’s monthly Plane Crazy Saturday open house in which he laid out in detail how the company plans to make human access to space routine, cheap and safe.
“XCOR has got an engine, the prototype for the Lynx engine, that has got more than 550 flight equivalents on it,” Valentine said. “We have not identified any wear mechanism, and the senior engineering team thinks that that engine is going to be good for many thousands of flights. Indeed, with all of the engines that XCOR has ever built, we have never worn one out or identified the wear mechanism.”
What that gives XCOR is the ability to fly the suborbital Lynx space plane with airline-type operations, Valentine added. In the same way that Southwest can fly the same 737 from one place to another with quick turnarounds, XCOR will be able to fly the Lynx into space, turn it around in 35 minutes, and fly it back.
With a single ground crew and pilot, Lynx will be able to fly four times per day. If you add a second pilot and another ground crew, eight flights are possible.
Valentine said that XCOR’s engines are more reusable than the space shuttle’s main engines, which had to be rebuilt after two flights, and propulsion systems developed by other companies.
“Until this century and until XCOR engines there were no engines that were suitable [for frequent, affordable reuse],” Valentine. “So the best engines were maybe 100 flights. SpaceX is rumored on their Merlin 1-D to get more than 100 flights per engine. With the original Merlins they were hoping to get 25 flights. That’s not good enough.”
SpaceX does not have the ability at present to reuse Merlin engines from its Falcon 9 rocket. The company is working on a project called Grasshopper aimed at allowing it to recover Falcon 9’s first and second stages intact.
Engines make up 20 to 30 percent of the cost of a rocket. If you can recover them and re-fly them on a daily basis, then the cost of spaceflight will drop dramatically. This is exactly what XCOR plans to do with Lynx, which will take off and land on a conventional runway.
Valentine said that the Lynx has the second highest specific impulse kerosene-liquid oxygen (LOX) engine in the world after SpaceX’s new Merlin-D engine. The engine’s performance, however, is secondary to engine safety and longevity.
The LOX tank on the production Lynx vehicle will be made out of a composite material called Nonburnite that will be 30 lighter than the conventional tank that it will replace, Valentine said. It will be the first reusable composite fuel tank ever built, he added.
Lynx’s engines use piston pumps instead of turbo-pumps used in most rockets. Piston pumps are a lot cheaper to develop and build, and they are safer than turbo-pumps, Valentine said. They also allow the pilot to start up the engine almost instantaneously and the test them before taking off. Turbo-pumps need to be spun up first before they reach full power.
The Lynx propulsion system is designed to avoid hard starts. XCOR has never had a hard start in any of its flights or engine tests, Valentine said. There is also a containment system to prevent engine problems from destroying the vehicle.
All the fuels used by the Lynx, including those in the reaction control system (RCS) thrusters, are non-toxic. This means the vehicle is safer and easier to turn around. It used to take technicians six days to fully safe the space shuttle after each flight before any other work could be done on the vehicle.
”We could not make money with the Lynx vehicle if it took us two weeks or even two days to safe the propellant system,” Valentine said.
Non-toxic fuels are also safer to use because toxic hypergolic fuels are corrosive and have a nasty tendency to explode.
“No one has every demonstrated safety adequate for us to use hypergolic propellents on a vehicle like this,” Valentine said. “The number of accidents involving hypergolics in routine operations over the years is so great that we could not get insurance if we had hypergolics on the vehicle.”
He said work on the Lynx vehicle is coming along well. The fuselage was delivered last month and other flight hardware is on the shop floor at XCOR’s hangar in Mojave. The company has a week or two of wind tunnel tests ahead of it to fully refine the ship’s design. Test flights are set to begin at the end of the year.
Valentine said XCOR has plans for a fully reusable, two-stage-to-orbit vehicle that would be based on Lynx technology. The first stage would take off from a conventional runway with the orbital vehicle on top. The orbiter would fire its own engines once the combination reached the proper altitude.
The goal is to operate the orbiter on the same principles as the suborbital Lynx. It would be cheap to operate and could be quickly turned around for another flight.Utilizing first-orbit rendezvous, the vehicle could fly once per day from Mojave and multiple times per day from any of several equatorial launch sites that XCOR is considering, Valentine said.
Cheap and frequent access to suborbital and orbital space would open up an entire range of applications that are now cost prohibitive, including environmental missions, solar power satellites, orbital fuel depots and much more. A Lynx equipped with a powerful camera, for example, would be able to return data on farming conditions over a broad area even cheaper than a satellite.
Part of the engine development work for the orbital system is being funded through a joint project with United Launch Alliance (ULA), Valentine said. XCOR and ULA are working together to develop a new, less expensive LOX-liquid hydrogen engine to replace the RL-10 motor on the Centaur upper stage. The new engine will be used on ULA’s Delta IV and Atlas V rockets as well as XCOR’s orbital vehicle.
Although the piston pumps used in the new ULA engine will be heavier than turbine pumps, they are cheaper to build and operate, Valentine said. The pumps also allow for lighter nozzles, making the overall weight of the engine roughly the same. The Centaur stage will also use Nonburnite tanks.
Not only will the improved Centaur upper stage make it cheaper for ULA to get payloads off of Earth, the stage could be restarted and reused in space thousands of times, Valentine said. Refuel the Centaur stage at an orbiting depot, and ULA can use it as a space tug to haul cargo in Earth orbit or send it to the moon or other destinations.
XCOR’s technologies can be used to construct the orbiting fuel depots, which is a key priority for NASA, Valentine added. They also can be used for commercial manned spacecraft, nanosat launches, reusable vehicles for landing on the moon and Mars, and terrestrial fuel tankers.