If gaseous H2 has absorbation bands in the IR, then tailoring the IR output of
the heaters so the gas heats--and the liquid does not--has the potential to
keep pressure up while minimizing boil off. The point here is that for a 2-4
minute burn one should design for a non-equilibrium state as between the gas
and the liquid; stratify the gas, not the liquid.
Borrowing from Tridyne designs, a platinum cat pack with a small H2 feed (for
the Lox side) will generate plenty of heat while staying below the combustible
range. It of course also generates small amounts of water that will freeze out
and float on the Lox surface, which may be a feature.
Bill
Sent from my Commodore 64.
-------- Original Message --------
Subject: [AR] Re: Hydrogen and oxygen used as pressurizing gasses
Local Time: December 11 2015 5:41 pm
UTC Time: December 12 2015 12:41 am
From: stevegt@xxxxxxx
To: arocket@xxxxxxxxxxxxx
I like the IR LED idea -- that could generate gas while keeping the electric
bits away from the wet bits.
Other possible heat sources: low-pressure starter motor, catalytic pack.
On Fri, Dec 11, 2015 at 4:02 PM, William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Brian:
As you may know, blowdown systems using self-pressurized Lox have been used by
amateurs for more than half a century (Jim Nudding of the PRS for hybrids, in
the 1950's, as an example). Environmental heat is sufficient if you size the
tank L/D correctly. The Lox will be warm and you will get lower density in
consequence.
Local heating to the surface can provide makeup pressure if you want constant
pressure through the burn.
Hydrogen is tougher using traditional assumptions but I would not do that: a
"cold" radiant heat source at the top of the tank (i.e., IR LED's) can provide
lots of gas while keeping the overall liquid cold; the obvious trick is in
keeping control of the system, for which modern control systems appear to be
more than sufficient: if a four rotor helicopter is stable enough to be sold as
a toy, keeping control of the local heating and pressurization of a cryogen
ought to be in family.
Simple systems tend to be lower cost and higher reliability....
Bill
On Fri, Dec 11, 2015 at 5:11 PM, Brian Feeney <alaiadesign@xxxxxxxxx> wrote:
Bill, what cycle are you suggesting to boil the liquids? Self pressurizing to
300 psi for LOX to O2 gas certainly works and has been demonstrated along with
methane. Self P for LH2 is I believe, under that pressure range. It was
mentioned to me years ago that LH2 may have some other difficulties in a self
pressurizing system given its extreme cryogen nature. Stratification? I don't
though have a good handle on it one way or the other.
Cheers
Brian Feeney
On 2015-12-11 4:55 PM, "William Claybaugh" <wclaybaugh2@xxxxxxxxx> wrote: