Very nice, and ty 4 looking out 4 the self impressed individuals (me)
I'll put on the other side of the camper I'm scrapping (lol) actually, I'm
well experienced in concrete and I'll build appropriate bunkers. Oh, I have
tons of 5\4" rough cut hardwoods ??? Snaps decking screws regularly.
The dwv is only being used as something to tighten my u bolts against, and
was thinking of filling the void with, 2 part foam, or... More solid and
I'll lose the function of the test... My kevlar wrap psi capabilities,
which I figure safely arrived to 30,000psi, going by this...
Kevlar 20 times stronger than aluminum at same specs (4,500psi+ @ 3" o.d. x
.25" walls) yields 90,000psi
Anyways, I know I applied to much epoxy to fabric ratio, so I'll half that
90,000psi to 45,000psi, and further because I prefer to start low and build
up until failure.
🧐 🤔 Anyone here know modulus by heart ? I'll pay good money 4 accurate
psi rating of 3" o.d. x .25" (specs attached) and I calculate maybe,
additionally, 17.5% too much epoxy. I made a tray to hold the well mixed
epoxy, all of it needed to complete the project, and a hanging roller,
slightly behind and above, with resistance... 2 much resistance ! So much
so, that I could barely continue turning it. The ends were most difficult
and even more epoxy than the main, maybe 25% percent extra, but, nearly 1"
thick in total
On Tue, Apr 18, 2023, 7:24 PM Steve Traugott <stevegt@xxxxxxx> wrote:
Okay, I'll say it. Kevin, others may chime in here, but for a motor that
size, I'm pretty sure you'd want an earth berm or solid concrete barrier
between you and the test stand. Distance alone isn't going to do it -- not
at 50 or 100 feet. Lexan is okay for protecting against little snafus but
in the event of a casing burst it may in fact add to the high-velocity
spiky chunks. That perforated DWV in the photo also won't act as
containment and will add its own spiky chunks if that's there during
firing.
Don't skimp on this -- successful engine R&D involves over 50% of your
time spent on test stands and other ground infrastructure and data
collection software work, and successful teams will blow up 90% of what
they build in some pretty spectacular ways. It all works best when you
have the ability to do that repeatedly, learning more from each iteration
without needing medical or legal assistance after a test.
On Tue, Apr 18, 2023 at 11:40 AM kevin ward <kevinward46@xxxxxxxxx> wrote:
Ty
Video recording of scales...
Lots of lexan...
50 to 100 feet away...
While burning on scales, pumping (1,000psi ???) Through 1 injector.
On Tue, Apr 18, 2023, 10:10 AM Ed Kelleher <Pres@xxxxxxxxxxxxx> wrote:
Hello Kevin,
Nice to see you building something. It's an important step, after
studying and thinking some, to verify your design.
A first approximation of thrust is Pc * At (chamber pressure * throat
area) - increase PC or At and thrust increases.
Later refined by Cf (Thrust coefficient which accounts for most of the
fiddly bits).
Best book would be Rocket Propulsion Elements by Sutton, 3rd edition or
higher, often available on eBay.
When testing, please treat your thrust chamber as a grenade. That is,
don't put anything near it that you don't want punctured by flying metal
For example, don't stand there trying to read the scales while it's
thrusting. :-)
Good luck!
Ed Kelleher
At 05:51 PM 4/17/2023, kevin ward wrote:
Can anyone help with this equation...
More psi in combustion chamber, no matter what, results in more thrust ?
BurnSim says so...
But dad insists NASA knows best and may 1 at the throat is penultimate.
Cutting issues with "supersonic velocities, at the throat, cause problems"
he pointed out a nozzle that had Mach 1 as Max propellant mass flowing, for
longer burn time... Vs less mass at higher velocities for less burn time.
Analogy: water hose at full open creates a little thrust, put a nozzle
on it and hold on... As in a fireman's hose or a high pressure washer.
You're only going to get thrust if you tighten up the throat.
I could see a different analogy that proves me wrong as in with a boat
and it's propeller. There is a point before velocity increases, that if you
apply too much torque, you're going to cavitate. Does that apply in rockets
?
I insist that NASA is limited in acceleration due to what they're
sending up; people, equipment, O-rings that go bang, etc. And the whole
point is to "attain escape velocity as quickly as possible". Another NASA
quote "controlled explosion".
Furthermore, throats and nozzle ends are maximized per the individual
rocket.Â
I figure they could go for, instead of steel motor casings, maybe kevlar
wrapped at 15 times psi, yielding a bunch more thrust, if they only sent a
rocket, with no purpose, other than trying 2 attain fastest object ever,
other than light.
I realize the rocket will burn up due to friction, unless properly
insulated, which isn't difficult.
If I just want to send a probe, to the kuiper belt, and wave an aerogel
disc, return and splash into the ocean.... I'll b limited by difficulty in
not destroying the aerogel, but, not NASA's fastest ever rocket, being
considered best velocity.
If you don't know, please instruct me where 2 go... B nice
Lol
Ty 4 your assistance.
P.s. Looking for team members\collaborators
Oh, pic of of M-2270. A little extra kiln coat on exterior to measure
variable temps. Inside casing is generous slathering of kiln coat (100HT).
Double choked nozzle will be additionally .25" kevlar adhered. (Playing
safe at 30,000psi, but figure capable of 50,00psi considering my imperfect
epoxy to kevlar fabric ratio.
Using air intake Jets to create gas wedge to alter vector. Passively. No
gyros or otherwise.
Additionally playing with extra metals in the propellant, i.e. rich
fuel\oxidizer mix. some of my fuel won't b onboard, rather scooped up as
accelerating, yielding less propellant mass required.
On Mon, Apr 17, 2023, 2:29 PM Henry Spencer <hspencer@xxxxxxxxxxxxx >
wrote:
On Mon, 17 Apr 2023, Uwe Klein wrote:
ratherA corollary:Â if you think of the first vehicle as a pathfinder
than as the main operational moneymaker, it should be sized for easy
manufacturing and operation,
You learn about the target environment.
But scaling effects may turn design decisions upside down.
Yes, you don't necessarily get the main operational moneymaker by just
running the pathfinder's plans through the Enlarge setting on the
photocopier. However, the real plans will also differ significantly
from
what you'd have drawn before building and operating the pathfinder.Â
The
purpose of the pathfinder is not to flight-test the technical design of
the operational vehicle, in miniature; it's to give you a better idea of
what that design should look like.
And the technical design of the vehicle is not the only issue.Â
Building a
team that can do a good job on the operational vehicle is part of it
too.
So is acquiring credibility as a launch supplier, and figuring out how
to
navigate the regulatory process. (Falcon 1 was financially a complete
flop for SpaceX, but it opened doors that were crucial to Falcon 9's
success.)Â Thinking of success in the launch business as purely a
technical problem is a dangerous delusion.
Henry
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