1
Results from Gaseous Methane/Oxygen Mixture Testing
Reema Reveles, Tyler Ross Lambert, Mike Bangham, James Allen, Jairus Schwartz, and
Brendan Mangan
Bangham Engineering Inc., Huntsville, AL, 35801, U.S.A
Liquefied natural gas (LNG) and liquid oxygen (LO
2
) propulsion for launch vehicles
is gaining significance in recent years. The safety standards are well-defined for
LH
2
/LO
2
and RP-1/LO
2
fuel-oxidizer mixtures. However similar standards are yet to
be established for LNG/LO
2
mixtures. The present test program is split into three
incremental blast test plans for experimental determination of the LNG/LO
2
explosive
behavior. The first test phase presented in this paper involves methane-oxygen gas
blast tests. Vinyl balloon of sizes 6-ft., 12-ft., 14.5-ft. and 16-ft. diameters respectively,
were inflated with the gas mixture and a combustion was triggered to simulate an
unconfined methane-oxygen explosion. A deflagration to detonation transition (DDT)
of the combustion zone was observed in most of the tests. The primary data that was
analyzed to develop empirical models were: (a)Overpressure, (b)Impulse, and
(c)Acoustic data. The recorded overpressure and impulse were compared to the TNT
based predictions. The initial results showed that the TNT-based overpressures over-
predict the near field data when compared to the experimental data. The empirical
model for impulse predicted a combined effect of a decay with scaled distance and an
increase with the fuel mass. The caveat to the gas experiment based conclusion is that
the test series does not exactly replicate credible accident scenarios for a vapor cloud
explosion from a cryogenic fuel/oxidizer failure. However, it is believed that the gas
explosions will envelope the overpressures from cryogenic propellant blasts. An
attempt to characterize the decay of overpressures in the acoustic regime is made since
the long-range acoustics from blast events have serious community noise and safety
implications. The follow-up test series with LNG/LO
2
mixtures will a more realistic
evaluation of the overpressures from a safety standpoint in the design of launch
systems.
I. Nomenclature
OP = Overpressure (psi)
= ambient pressure (14.7 psi)
= range from the center of blast (test data at 10, 20, 30 and 50 ft.)
= radius of the balloon (test data for 3, 6, 7.25 and 8 ft. radius balloons)
LNG = Liquefied Natural Gas
LO
2
= Liquid Oxygen
LH
2
= Liquid Hydrogen
COE = Center of Explosion
DoD = Department of Defense
RP = Rocket Propellent
