[AR] Re: Ignition Sequence for Main Valve Timing
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 2 Aug 2016 13:29:41 -0400 (EDT)
On Tue, 2 Aug 2016, David Masten wrote:
As others point out, depends on details. I've gone LOX first for two
reasons - LOX valve sluggishness and combustibility limits...
Another reason: unless you are purging the chamber with (say) GN2 at the
beginning of the sequence, conditions in the chamber invariably start out
oxidizer-rich because there's air in there! Starting with the oxidizer
postpones the transition to fuel-rich until you're in better control of
the situation.
Starting with a cryogen also helps establish control of chamber conditions
more quickly, because chilldown gas tends to sweep the chamber clear.
Physically linking the two propellant valves gives all the same benefit
if you are regenerative cooling with the fuel, and the LOX valve is
sufficiently close to the injector...
People have even done torch igniters that don't have separate valves, but
just have the plumbing arranged so the propellants reach the torch before
they reach the chamber. (Although that does remove one big advantage of
torch igniters: now you can't have an interlock that prevents the chamber
feeds from starting if the torch doesn't light or doesn't stay lit.)
Henry
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