Orbitec, which also produces environmental-control and life-support systems, fire-suppression equipment and kits that will enable astronauts on the International Space Station to start to grow fresh food next year, has been working on vortex combustion since 1998, according to propulsion director Marty Chiaverini.
“We had been conducting research on swirl-injected hybrid rockets for improving fuel-burning behavior and discovered that under the right conditions vortex flow could be used to prevent flame spreading along solid fuel surfaces, rather than enhancing it,” Chiaverini says. “We modified some existing hardware and ran some proof-of-concept experiments on the vortex-cooled liquid rocket combustion chamber concept during the summer of 1998.”
Since then the company has tested its patented concept using a number of different liquid and gaseous propellants. The flexibility, which requires tweaking the propellant flow in the chamber to accommodate the varied propellant properties, “makes the system very attractive for most applications that are called out currently, as it does not discriminate,” says Chiaverini.
Potential applications range across the spectrum of thrust levels. The approach could also include rocket-based combined-cycle engines that start off using atmospheric oxygen before shifting to liquid oxygen at high altitude, according to a joint NASA/U.S. Army Missile Command study conducted in 2000 with Orbitec input.
“So far, we have successfully scaled the vortex chambers from 10 [lb. thrust] to 7,500 [lb. thrust],” he says. “We do not see any fundamental barriers to additional scale-up. The main issue we need to deal with [regarding] scale-up is injector design and optimization.”
The 30,000-lb.-thrust VR-3A engine under development for the Ausep competition will use liquid hydrogen fuel, Zamprelli says. The Air Force is looking for “cost-effective, technically mature alternatives to the Evolved Expendable Launch Vehicle upper stage,” according to NASA, which is collaborating on the effort.
“NASA is interested in the study as the [advanced upper stage engine] could be a candidate to power the [heavy-lift Space Launch System] cryogenic propulsion stage for in-space applications to enable exploration to multiple destinations beyond low Earth orbit,” according to the civilian space agency's Marshall Space Flight Center.
During the past 15 years, Orbitec has upgraded its test facilities to accommodate more powerful vortex engine ground-testing, working with both the Air Force and NASA on advancing the technology.
The flight test was preceded by a Sept. 20 ground test with a 3,000-lb.-thrust setup that demonstrated the chamber-wall vortex cooling, acoustic igniter and the ATK lightweight nozzle extension, which uses that company's technology to join hot carbon-carbon components to an actively cooled metal housing (AW&ST Oct. 1, p. 15.