Frank Morring, Jr. Washington

An innovative combustion-chamber setup that was flight-tested last month could cut the cost of rocket engines by eliminating the need for regenerative cooling.

Orbital Technologies Corp. (Orbitec), a Madison, Wis.-based space-technology company, flight-tested a version of the 30,000-lb.-thrust liquid-propellant rocket engine it is developing for the U.S. Air Force's Advanced Upper Stage Engine Program (Ausep) and other in-space applications.

Results of the Oct. 20 sounding rocket test at Mojave, Calif., validated the company's “vortex” engine technology, which injects fuel and liquid oxygen so that the burning mixture does not touch the walls of the combustion chamber, allowing them to be thinner, lighter and lower cost, says Paul Zamprelli, business development director.

By carefully tweaking the propellant-injection parameters, the company hopes to eliminate the need for costly cooling tubes or channels that circulate unburned fuel through the combustion chamber walls to prevent them from overheating. The flight test also demonstrated Orbitec's acoustic igniter and a lightweight carbon-carbon nozzle extension developed for the flight by ATK.

“The next step is to demonstrate the performance at a larger scale and ensure that future launch vehicle requirements are captured in our design,” Zamprelli says. “Orbitec is ready and excited to compete for any future rocket engine and propulsion applications.”

In the vortex approach, oxidizer is injected into the combustion chamber at an angle that sets up a pair of coaxial vortices (see illustration). The swirling motion provides better mixing with the fuel, with combustion occurring in the innermost vortex. The outer vortex protects the chamber walls and other surfaces from the heat of the combustion.

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.