“Definitely want to be clear between nucleate boiling (common in regen) film
boiling (normally the end of a regen rocket) and the sort of bulk vaporization
that some people are talking about here for which I'd be surprised if it had
been used in a production rocket.”
- Good point. With peroxide, I am talking about nucleate boiling for the most
part. Film boiling does occur when you are getting close to the limit. It goes
boom long before bulk boiling occurs.
So to answer henrys question: it is absolutely necessary to avoid bulk boiling
of peroxide in your regen. Nucleate boiling will occur. If film boiling is
occuring, you had better increase your regen flow velocity.
Stefan Powell
Co-Founder, CTO
+64 (0)275273528
www.dawnaerospace.com<http://www.dawnaerospace.com>
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From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On Behalf Of
Ben Brockert
Sent: Wednesday, 21 October 2020 10:10 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Hypothetical Lox cooling
Definitely want to be clear between nucleate boiling (common in regen) film
boiling (normally the end of a regen rocket) and the sort of bulk vaporization
that some people are talking about here for which I'd be surprised if it had
been used in a production rocket. You certainly could make an engine with
geometry such that the propellant was liquid and then became gas at a specific
place (with an orifice and then larger channel to keep the velocity down) but
I'm not sure why.
Depending on the propellant you could have an expander engine where it goes
from liquid to supercritical in the jacket and then supercritical to gas in the
turbine, but once you're in pump fed land I'd be surprised if it didn't
optimize to supercritical all the way to the chamber. You practically can't
make a useful hydrogen engine that isn't supercritical. Oxygen, methane, and
propane are all under 1000 psi. Ammonia at 1640 psi? I can't think of many
useful propellants you'd want to vaporize.
In peroxide there's so much cooling capacity that you'd have to have a very
strange setup to have enough heat on hand to vaporize it all, assuming that you
can do that without it doing something energetic. There's probably some half
secret experimental Soviet cycle where you can get it to thermally decompose
predictably and then have oxygen and steam to run the turbine.
On Wed, Oct 21, 2020 at 11:49 AM Stefan Powell
<stefan@xxxxxxxxxxxxxxxxx<mailto:stefan@xxxxxxxxxxxxxxxxx>> wrote:
There is proper data from this black arrow/Gamma days. Local boiling can happen
on the micro scale in the regen boundary layer at temperatures >>150 degC. It’s
actually unavoidable in high heat flux engines where the hotside wall temp gets
to >400C. As long as the heatflux/velocity ratio of the coolant is high enough,
the boiling (decomposing, exothermic!) liquid/vapour mix in the boundary layer
mixes in with the rest of the coolant flow, recondensing and cooling and RUDs
are avoided. We found out the hard way a few times.
Stefan
From: arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>
<arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>> On Behalf
Of Henry Vanderbilt
Sent: Wednesday, 21 October 2020 12:52 PM
To: arocket@xxxxxxxxxxxxx<mailto:arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: Hypothetical Lox cooling
I was already assuming Black Arrow avoided peroxide boiling in the cooling
passages. Sorry my question wasn't clear enough: Does anyone have any informed
comment on how absolutely necessary, or otherwise, that might be in using h2o2
as a coolant? As I said, my limited info on the lower stability of peroxide as
vapor is anecdotal.
Hmm. Per Wiki, "The boiling point of H2O2 has been extrapolated as being 150.2
°C (302.4 °F), approximately 50 °C (90 °F) higher than water. In practice,
hydrogen peroxide will undergo potentially explosive thermal decomposition if
heated to this temperature. It may be safely distilled at lower temperatures
under reduced pressure.[7]"
So, possibly there's a practical upper temperature limit even if you do
pressurize it to raise the boiling point.
Does anyone know? Thanks in advance...
Henry
On 10/20/2020 12:05 PM, roxanna Mason wrote:
Maybe boiling, at the feed pressure, was avoided. Possible.
K
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On Tue, Oct 20, 2020 at 11:32 AM Henry Vanderbilt
<hvanderbilt@xxxxxxxxxxxxxx<mailto:hvanderbilt@xxxxxxxxxxxxxx>> wrote:
Speaking of possibly exciting hobbies, what happens if you boil peroxide in
cooling passages? Is that another one of those things one should avoid?
I gather peroxide cooling worked in Black Arrow, but I have the impression from
various distillation tales of woe that peroxide vapor is much less stable than
the liquid. I might guess both that preheating the peroxide could help with
catalyzing or directly combusting it, and also that making sure it stays liquid
till then is indicated, but those are just guesses.
Henry
On 10/20/2020 11:09 AM, Doug Jones wrote:
A supercritical positive-heat-of-formation oxidizer with oily contaminants
leached from every step of the distribution chain. What could possibly go wrong?
On Tue, Oct 20, 2020 at 11:04 AM Bruno Berger
<bruno.berger@xxxxxx<mailto:bruno.berger@xxxxxx>> wrote:
Am 20.10.2020 um 19:53 schrieb roxanna Mason:
Is your fuel even less satisfactory?Yep, we discussed that at ARIS for cooling the nozzle with N2O for their
Perhaps it's a LOx/solid fuel hybrid and you want to cool your nozzle.