Two years ago Mike Bangham, owner of Bangham Engineering of Huntsville, Alabama, visited Dugway Proving Ground in the remote Utah desert. He sought a remote area for a new type of rocket fuel, made of liquid natural gas and liquid oxygen that reportedly cost one tenth of other liquid rocket fuels.
The test, begun two years ago and expected to go into 2022, is called COMET, for Cryogenic Oxygen-Methane Explosion Test. Subcontracted to the U.S. Air Force and commercial United Launch Alliance (ULA), Bangham Engineering is learning the explosive properties of the new LNG/LOX propellant.
“We are creating explosions generated by LNG/LOX to establish TNT equivalency,” Bangham said. “We’re trying to get data on the explosive properties, to understand the risk to facility personnel on the ground and what could happen to the astronauts on board.”
The explosive properties of traditional liquid rocket fuels have been known for years, but the new LNG/LOX fuel is an enigma.
“We’re trying to get as close as we can to understanding the physics of what happens when LNG/LOX explodes,” Bangham said. “It’s not like your typical weapon. There is actually more energy stored in these chemicals than the equivalent in TNT, but it doesn’t release energy as quickly.”
In COMET tests, a rocket body is replicated from stainless steel and placed upright to duplicate a launch. Within the rocket body are two large chambers, each containing liquid oxygen and liquid natural gas. They are kept from mixing by a thick pane of glass. Upon “launch” the glass is remotely shattered and the volatile liquids mix. The explosion can be immediate when autoignition occurs. If autoignition does not occur, a secondary ignitor starts the explosion after a programmed delay .
Instrumentation near the rocket body records the pressures and heat generated by the blast in high speed, along with high speed video. Dugway provides meteorological conditions (wind, humidity, dew point and temperature) and the time of ignition.
The last COMET test, with large amounts of LNG/LOX, produced an especially strong blast, creating a large crater and damaging critical test equipment. The curved lid of the tank shot up like a flying saucer, and landed 800 feet away. Though other test facilities in California and Nevada were considered for COMET, Dugway was selected two years ago partly for its size and remoteness: 1,248 square miles without encroachment, and abuts the Air Force’s Utah Test and Training Range of 2,675 square miles.
“Dugway has a combination of people that can support the test, and enough area that we didn’t have to share the space with others,” Bangham said.