I am not advising the USC folks that they should try to achieve low
performance. I am advising them to focus on safety first, operability
second, and performance third.
If they pay attention only to safety and operability in steps one and two,
they will avoid the trap of premature optimization. Optimization is part
of step three.
When they start step three, they may well find that that their Isp is
already over 100 seconds. That's nice. They may find it already at 165
seconds. That's nice. Right out of the gate, performance Does Not Matter.
The horse has to learn to walk first.
-R
On Monday, September 12, 2016, Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Well, to a point. Like everything in life, you need a balance. Any
performance outcome that’ll be under your propellant combination’s c* or
c*/g (in Isp terms - ~165sec for this combination say) must have sub
optimal mixing unless you have a gaping hole in your chamber. Nobody should
expect to hit optimal mixing in the early days of development, but … dunno…
if the mixing is too far out of whack, does that not potentially expose the
chamber to potential damage or hard moments?
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx
<javascript:_e(%7B%7D,'cvml','arocket-bounce@xxxxxxxxxxxxx');> [mailto:
arocket-bounce@xxxxxxxxxxxxx
<javascript:_e(%7B%7D,'cvml','arocket-bounce@xxxxxxxxxxxxx');>] *On
Behalf Of *Randall Clague
*Sent:* Tuesday, 13 September 2016 12:37 PM
*To:* arocket@xxxxxxxxxxxxx
<javascript:_e(%7B%7D,'cvml','arocket@xxxxxxxxxxxxx');>
*Subject:* [AR] Re: LOX / IPA P&ID
If it works at all, it probably delivers 100 seconds or more. Fine. My
point is, forget about that. One step at a time. Premature optimization is
the bloodsworn enemy of success. Step two is Make It Work, success
is defined as supersonic flow. THEN, and only then, focus on the numbers.
-R
On Monday, September 12, 2016, Jonathan Goff <jongoff@xxxxxxxxx
<javascript:_e(%7B%7D,'cvml','jongoff@xxxxxxxxx');>> wrote:
Randall,
While I agree with the general sentiment that getting something that fires
reliably and safely comes first, I think you'd have to try hard to get
LOX/IPA rocket that only delivered 100s Isp, even on a first try.
Jon
On Sep 12, 2016 4:28 PM, "Randall Clague" <rclague@xxxxxxxxx> wrote:
242 seconds is ambitious for a first effort.
First make it safe. Forget about Isp, your goal is making fire without
making shrapnel.
Then make it work. Forget about Isp, your goal is making supersonic flow
without making shrapnel.
Then make it work better. You probably hit 100 seconds in step two. Try to
hit 200 seconds, but remember, Reliability Is More Important Than
Performance.
-R
On Monday, September 12, 2016, Dillon Wessing <dillonwessing@xxxxxxxxx>
wrote:
Hi all. I am the lead of the USC Liquid Propulsion Lab. We’re developing a
LOX / IPA engine and wanted some input/advice on our ground testing P&ID.
Just some general specs for the engine. 10 kN of thrust. Total mass flow
4.2 kg/s (fuel: 1.91 kg/s, ox: 2.29 kg/s). Chamber pressure 350 psi.
Pressure going into the injector 437. 5 psi.
We are having channels milled into our combustion chamber for regen
cooling with the IPA and will have a separate reg for the ox since the IPA
will have higher pressure drops. Please comment on the validity of this
design and any concerns that we should keep in mind.
Best,
Dillon Wessing
