A mechanical failure during the test launch of a biodiesel-powered rocket produced unexpected results, giving rocket engineers a deeper appreciation for the biofuel. According to Steve Harrington, chief executive officer of Carlsbad, Calif.-based aerospace engineering company Flometrics Inc., a stuck fuel valve on the rocket caused some biodiesel to flow into the liquid oxygen system and, upon ignition, a fire inside the liquid oxygen manifold caused the launch to fail on March 7 in the Mojave Desert in the southwestern U.S.
“We got a big puff of flame out of the nozzle, but no significant thrust,” Harrington said. “The rocket didn’t go anywhere.” But what happened next was a surprise. “We ran into a problem, but then we discovered this advantage of biodiesel that we hadn't expected. This type of failure often causes a serious fire when you use kerosene: you get a pool fire underneath the rocket and it just kind of barbeques the fins, and so on. But this time the fire was minimal. The biodiesel just went right out and the rocket did not even get scorched.”
According to NASA, the RP-1 kerosene-based rocket fuel that Flometrics used to power its RocketDyne LR-101 rocket engine has a minimum flash point of 82 degrees Fahrenheit (28 degrees Celsius). The National Biodiesel Board said the flash point of biodiesel can range from 200 to 300 degrees Fahrenheit (93 and 149 degrees Celsius). By comparison, the flash point of petroleum diesel is 140 degrees Fahrenheit (60 degrees Celsius), the NBB said.
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“The biodiesel showed a definite advantage compared to the standard fuel in that it wouldn't sustain itself in a pool fire,” Harrington said. “This may be a reason to use it for manned missions, to keep the chances of catastrophic fire lower.”
Harrington said the next attempt to launch the 20-foot tall, 150-pound rocket will be on March 21. “The people who run the launch facility are hosting a launch for the Boy Scouts that day,” he said, “and so it will be a heckuva show for the Boy Scouts.”
For more information, read “Flometrics to launch biodiesel-powered rocket.”