Sent from my iPhone
On Aug 19, 2016, at 1:27 PM, Erin Schmidt <7deeptide@xxxxxxxxx> wrote:
@ Zachary
Addendum II: One final thought, cranking up TWR will give you passive
stability off of the launch rail, but will also tend to activate L/D
constraints. This means dynamics/controls problems may just be inherently
difficult to avoid in this design regime...
On Fri, Aug 19, 2016 at 11:22 AM Erin Schmidt <7deeptide@xxxxxxxxx> wrote:
@Ben
I think you raise a very good point. Our own experience was that it was very
difficult to get our heat transfer reqs. to converge without film cooling
for such a small engine.
Very much appreciate any information you can find regarding mass envelope
for small LV's. It's easy enough to find regression models for larger
engines; but this is the interesting space we're in...
@Zachary
Addendum: I notice that if I reduce the dry mass by too much (say by halving
the feed system mass to 10kg vs. 20kg) while maintaining the TWR >5, and
Max_accel<15g constraints, the total GLOW paradoxically increases
(significantly) vs. a rocket with a higher dry weight. This is definitely
due to aerodynamic drag. This is a funny sort of regime to identify (and one
of the huge advantages to experimenting with modeling/convex optimization in
the early design phase of such a rocket).
On Fri, Aug 19, 2016 at 11:09 AM Ben Brockert <wikkit@xxxxxxxxx> wrote:
On Fri, Aug 19, 2016 at 7:48 PM, Erin Schmidt <7deeptide@xxxxxxxxx> wrote:
The liquid engine PSAS is currently building is about 2kN for reference,
6kN
is getting pretty dang big for an amateur built regen bi-prop engine.
I'd argue that amateurs shouldn't start at anything smaller than 4500
N or so. It's still in a scale where tubing or billet is easily
available to make the engine, but large enough that cooling isn't as
difficult. The bigger an engine is the easier it is to cool, no matter
whether it's regen, film, or ablative.
It's also large enough that it's not trivially replaced by a COTS
solid. It gets flows into the range of "easy maintenance" ball valves
(i.e. bolted flange), which typically only go down to 1/2" pipe size.
And it's in the sweet spot for standard 0.8 Cv regulators.
To the original question, I wish I had a MEL of a liquid rocket or two
to share with you, but I don't. I'll see if it's something I can
scrape together in the future.
Ben
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Erin Schmidt
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Erin Schmidt
