As well as keeping the exterior of the system cool, the vortex also works to burn the rocket fuel more efficiently by promoting more complete mixing of the fuel and air in a confined area. In addition, the longer path of the spinning vortices give the fuel more opportunity to burn, meaning the chamber height can be reduced, making for a significant weight savings – and therefore cost – savings.
Vortex rockets can also be considerably simpler and cheaper to build than conventional engines. And because vortex engines are less subject to severe heat and wear they last longer, which may make them suitable for reuse, cutting mission costs even further.
Such potential benefits explain why work on the unique power plants has been funded by the US Air Force Research Laboratory and other defence department agencies for more than a decade.
“It’s a nice, simple solution to the rocket chamber-cooling problem,” says Michael Micci, a rocket propulsion specialist and professor of aerospace engineering at Pennsylvania State University.
Orbitec’s research team now thinks that their rocket is ready for bigger and better things. Its October test in the Mojave used a version of a 13,600-kg-thrust (30,000-lb) liquid engine that it is developing for the US Air Force’s Advanced Upper Stage Engine Program, which aims to find a more capable and affordable upper-stage motor to sit atop the Atlas 5 and Delta 4 rockets it uses to launch most national security payloads.
The upper-stage of a rocket is the last to fire – and is usually the smallest segment of the vehicle. It operates at high altitudes once the lower stages have fallen away and pushes the payload into its final orbit. Current upper-stage technologies tend to account for a significant – and seemingly disproportionate – amount of the overall mission costs, according to the US space agency Nasa. Better-performing upper-stage engines would reduce costs because a given payload could be delivered using a smaller launch vehicle.
Nasa is particularly interested in the Orbitec’s vortex/cold-wall engine technology as a possible candidate to power the upper stage of its Space Launch System, the agency’s next-generation heavy-launch vehicle that will take the place of the space shuttle and may be used to kick-start manned missions deeper into the solar system.
The same technology could be used for manoeuvering spacecraft and propelling planetary probes. It could also help booster rockets get off the launch pad, paving the way for significantly safer, low-cost space access, Orbitec says.
Not bad for a firm that began in 1988 as a tiny university spinoff with “three engineers in a garage” in Madison, Wisconsin, says an admiring industry insider.