If there's a pad failure after ignition the mixing propellants will ignit
immediately as they mix real time so a premix then ignition is unlikely.
Perhaps having flares preburning like they do with the shuttle SSME is a
good idea.
Ken
On Mon, Jul 4, 2022 at 10:22 AM Doug Jones <rocketplumber@xxxxxxxxx> wrote:
The miscibility makes me think that placing LOX tanks under LNG may help
reduce the mixing due to density. LOX over LNG may be good for vehicle CG,
but scary for a fallback scenario.
The upper stage makes sure you have a Dagwood sandwich of mixing, though.
On Sat, Jul 2, 2022 at 12:52 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Fri, 1 Jul 2022, willsrw@xxxxxxxxx wrote:
I’m surprised the conversion is assumed to be one to one. A one to one
conversion (propellant to TNT equ) means 100% mixing to a perfect
mixture ratio throughout the entire volume of propellant.
No, not nearly -- methane's heat of combustion (complete combustion,
oxygen included in mass, but assuming water vapor produced remains vapor)
is 10.0 MJ/kg, while nominal TNT energy output is about 4.6 MJ/kg. Even
considering that a typical propellant mix doesn't contain enough oxygen
for complete combustion, LOX/CH4 is quite a bit more powerful than an
equivalent mass of TNT. Perfect mixing would yield close to 200%.
Difficult to do.
But much less difficult than for LOX/LH2 or LOX/kerosene, where the large
temperature difference gets in the way. That's why people are wary of
LOX/methane, in the absence of large-scale tests -- good mixing is much
more plausible when the two liquids are at about the same temperature and
are fully miscible.
Henry
