It's exactly what everyone's looking for: an engine that works on cheaper, less toxic, more readily available fuels.
This engine just happens to be for a rocket.
Engineers at NASA's Johnson Space Center and White Sands Test Facility teamed up with Dallas-based Armadillo Aerospace through an Innovative Partnership Program agreement to design and test a rocket engine that runs on liquid oxygen and liquid methane, for use on the moon or other extraterrestrial surfaces. Armadillo developed the engine, JSC designed and fabricated the nozzle and provided oversight on the project, and White Sands contributed the testing facilities. The project was jointly funded through the NASA Innovative Partnership Program office, the Propulsion and Cryogenic Advanced Development project, and Armadillo Aerospace.
The result was an engine that runs reliably on propellants that are not only cheaper and safer here on Earth, but could also be potentially manufactured on the moon or even Mars.
For decades – since the Apollo program – NASA has been using hypergolic propellants. They're nice because all you have to do to make them ignite is mix them together – once they come into contact with each other, you can depend on them to perform as planned.
But you pay a price for that dependability, literally and figuratively. They're expensive, they're heavy and they're toxic. So, since the late 1990s NASA has been looking into other options. One of those options is a combination of liquid methane and liquid oxygen.
Cryogenic liquid methane and liquid oxygen are 10 to 20 times less expensive than hypergol propellants. They weigh less, which is important because every pound of weight carried into space requires 15 pounds of fuel to send it there. And they're nontoxic, so if, for instance, they're used by a lunar lander, astronauts performing moonwalks won't have to worry about traces of it hanging around on the lunar surface and contaminating their spacesuits.
And as an added bonus, a team at NASA is already working on reactors that can convert moon dust into oxygen or create methane from the Martian atmosphere. Called in-situ resource utilization, methods such as these have the potential to further reduce the amount of propellants carried into space.
So, with all those advantages, the next logical progression is to prove the feasibility of the technology in a simulated space environment. That's where Armadillo Aerospace and the Innovative Partnership came in. NASA's Innovative Partnership Program is designed to allow NASA to share limited resources with outside partners who can help develop technologies that are important to NASA's missions. Armadillo is a private company that aims to eventually build a spacecraft that could be used for space tourism. Because of that, it shares NASA's interest in engines that run on low-cost, readily available, safe fuels.
Through the partnership, NASA was able to offer Armadillo expert advice and infrastructure for designing and testing a Vertical Takeoff / Landing vehicle. For its part, Armadillo was able to experiment with the engine design in order to develop the engine while making quick-turnaround changes as needed.
"They are a rapid turnaround facility," said Jacob Collins, an aerospace engineer at Johnson who worked with Armadillo on the project, "while we are a detailed engineering design team. Armadillo often does not have drawings for their designs. But they are able to design, fabricate, and test faster than drawings can be completed and approved. This partnership offers the best of both worlds: rapid prototyping and testing guided by engineers experienced with cryogenics."
That proved a winning combination. The engine and nozzle assembly was tested inside the vacuum chamber at the White Sands Test Facility. More recently, an un-tethered flight test was successfully completed - as shown in this video - reaching a height of 180 feet. The altitude isn't the important part, though. Federal Aviation Administration regulations controlled the altitude, but the flight experience gained – including all phases of the check-out, ground loading, flight, and recovery operations – is identical regardless of altitude.
The flight testing and the White Sands vacuum testing have enabled the team to achieve many technological firsts. For instance, they achieved the first liquid oxygen/liquid methane hot-fire test of a dual-bell nozzle while simulating a descent in altitude; the first pyrotechnic ignition at altitude using this combination of propellants; and the first self-pressurized throttling liquid oxygen/liquid methane lander.
Those tests wrap up the first phase of the partnership between NASA and Armadillo, and both sides of the equation continue to reap the benefits as they move into a second phase. In the meantime, the achievements so far represent good progress.
"We went through the tests and generated test data where none existed," Collins said. "Just mentioning a liquid oxygen / liquid methane hot-fire is foreign to a lot of people. The data collected on this project is a huge leap forward toward demonstrating the feasibility and many advantages of this technology."