Ken,
I genuinely believe that LOX is the preferable oxidizer of choice for
*liquids*. Even maybe smaller ones. I just don’t believe that’s the case for
hybrids. Maybe with today’s additive technology my understandings might be
dated – regarding larger ones.
I bow to your experience with liquids.
Cheers,
TP
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of roxanna Mason
Sent: Monday, 15 March 2021 10:29 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Hybrid High Powered Rocket
It's what you're used to, how you were taught and who did the teaching. I was
blessed to have met and worked with Bob Truax for 35 years, couldn't have had a
better teacher/mentor.
He helped me learn how to handle and design LOx systems. All I want to do now,
now that I'm retired is to pass on what he taught me and so be it..
I'm currently in the finishing phases of designing a flight LOx/Kerosene rocket
for a small group of high school students in Texas. They learn fast, 35 years
of knowledge assemulated in under 6 months, impressive. They'll be future
engineers.for SpaceX and who knows what other companies to be.
Bless their little souls,
Ken
On Sun, Mar 14, 2021 at 4:10 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx
<mailto:troy@xxxxxxxxxxxxxxxxxxxxx> > wrote:
Yes okay, they can be self-pressurized but at modest pressures (200-300
psi(ish) without significant drops over the depletion but then you have to also
allow for pressure drops over the injectors and again, we are talking hybrids
here not bi-props or liquids where the O:F ratio will vary with grain
regression. LOX hybrids sound easy in theory.
Troy
From: arocket-bounce@xxxxxxxxxxxxx <mailto:arocket-bounce@xxxxxxxxxxxxx>
[mailto:arocket-bounce@xxxxxxxxxxxxx ;<mailto:arocket-bounce@xxxxxxxxxxxxx> ] On
Behalf Of roxanna Mason
Sent: Monday, 15 March 2021 9:47 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Hybrid High Powered Rocket
Troy, have you designed built and hot tested LOx systems yourself?
Just curious because all the minor negatives are easily dealt with. BTW, LOx
can be self pressurizing,
The first liquid rocket flight by Goddard in 1926 was done this way, he used it
to pressurize the fuel tank as well.
I wouldn't recommend it but it worked.
Being an engineer I don't believe in fixing something that works and if someone
is already using Nitrous safely then great. But if a newcomer to liquid rockets
asks what oxidizer to try out, I'd recommend LOx. It will help him/her in
their future career in aerospace more than nitrous experience too.
Ken
On Sun, Mar 14, 2021 at 3:12 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx
<mailto:troy@xxxxxxxxxxxxxxxxxxxxx> > wrote:
How to make hard-line clerics look like consummate pragmatists…
Now there’s a Best Seller just waiting for pen to paper…
Ken,
There’s a reason (no, multiple reasons) why N2O has been the only liquid
oxidizer approved for use with Tripoli and that’s not through the
hand-waving-chest-beating-table-thumping preaching of biased dogma. It’s by
pure *practicalities* and even the extra fuss needed for N2O proved over time
to rendered them unpopular against the vastly more practical solids.
HPR hybrid flyers could go out and fly their birds without the need for a
dewar or the need to have it filled just prior to the launch or to deal with
cryo sealing or potential embrittlement of a neighbouring parts or needing a
separate pressurant and accompanying plumbing with that or the requirement for
more specialised injectors. The hardware was cheap and simple. The assembly
could be fairly simple.
Again, it’s horses for courses. Yes, beyond a certain size system, LOX
becomes more practical, but the intended audience was quite clearly spelled out
as HPR.
Troy
From: arocket-bounce@xxxxxxxxxxxxx <mailto:arocket-bounce@xxxxxxxxxxxxx>
[mailto:arocket-bounce@xxxxxxxxxxxxx ;<mailto:arocket-bounce@xxxxxxxxxxxxx> ] On
Behalf Of roxanna Mason
Sent: Monday, 15 March 2021 8:06 AM
To: arocket@xxxxxxxxxxxxx <mailto:arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: Hybrid High Powered Rocket
I wish certain folks would lose their cryo phobia, LOx is such a superior
oxidizer and the self pressurizing 'advantage' of nitrous is all but lost with
the very few cons.
If you have a misfire in a LOx system just let it evaporate away. Of course all
pressurized systems will have relief valves or burst discs or both, which is my
favorite passive doubly redundant design philosophy. A 40-50 gallon dewar of
LOx can run anywhere between $75 and $300 depending on many factors.
A well maintained dewar will have only 1-2% loss per day so if you have a week
or two delay no problem.
My mom used to take me down to the welding supply store when I was in my single
digits age and get a liter of LOx or LN2 to 'play' with, price was always $2.
Get used to its properties and work your way up to closed systems. When I was
about 15 I asked an Aerojet engineer that was visiting our group, "what is LOx
like?" He said to me: "It's like water" He meant a Newtonian fluid, the cold
is largely inconsequential once understood. Some seals/o-rings need changing
and all non ferrous metals are com[patabler with LOx. Insulation is usually non
necessary with test stand components only extended storage is insulation
necessary nother like LH2 which requires insulation under all circumstances.
My friend Glenn May died in a nitrous explosion along with two of his
co-workers. I guess you could argue I have nitrous phobia, maybe so but it's
based on fact not a misperceived fear of an industrial gas that is produced,
transported.and used by the thousands of tons per day world wide w/o mishap.
Read and learn as much as it takes to understand the nature of any beast.
LOx Rocks,
Ken
On Sun, Mar 14, 2021 at 12:39 PM Henry Spencer <hspencer@xxxxxxxxxxxxx
<mailto:hspencer@xxxxxxxxxxxxx> > wrote:
On Sun, 14 Mar 2021, Troy Prideaux wrote:
The one glaring point to laser focus on with a Chill-and-Fill hybrid
is to ensure your tank is *rated* to hold the required pressure. If
you’re making it yourself, allow at least a x3 safety factor with a
pressure relief device.