"under expanded."
Correction, over expanded, I get thermodynamic dyslexia
Ken.
On Tue, Apr 18, 2023 at 3:29 PM kevin ward <kevinward46@xxxxxxxxx> wrote:
At nozzle, under-expanded ? Sure to rich fuel mixture ?
With collection of air, balancing the proper fuel\air mixture.... ?
C* ?
Not a rocket scientist, yet.
My father's now handling maxing the motor, I'm testing the previously
constructed one, B4 even figuring most of this out.
Nozzle is fixed, but double choked, and stuff will vary as acceleration,
velocity increases.
Dad suggests that air cannot be injected at choked chamber due 2 high psi
internally.
Bigger air scoops, into smaller lines into smaller injectors, I think,
reduced, but yes...
Is come chamber still combusting fuel of oxidizer added there ?
Considering scrapping rich fuel mixture, and just going with the best
solid fuel, under 5,000° f, and 50,000psi, to add much as 100,000psi, yet
retaining air scoops 4 passive stabilization, only.
Do y'all c possibility of enough improvement picking up oxidizer ? I could
add in main combustion, but then have to overcome that internal pressure...
Don't c overcoming 50 to 100 thousand PSI easily
On Tue, Apr 18, 2023, 2:31 PM roxanna Mason <rocketmaster.ken@xxxxxxxxx>
wrote:
More psi in combustion chamber, no matter what, results in more thrust ?
A little late but my 2 cents. Assuming fixed nozzle geometry, more
pressure in the chamber(Pc) happens when M-dot increases,
when M-dot increases then Thrust (F) increases in a near linear fashion.
c* may shift a little up or down but for conversation sakes, that's how it
works.
Thrust coefficient (Cf) will increase a little if the nozzle is
initially under expanded.
Suttons book is best and so is the soft cover book from China Lake, How
To Design, Build and Test Small Liquid Fuel Rocket Engines. It's currently
on ebay.
Ken
On Tue, Apr 18, 2023 at 7:10 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
Content-Type: image/jpeg; name="IMG_2023-04-15-11-17-45-545.jpg"
Content-Disposition: attachment;
filename="IMG_2023-04-15-11-17-45-545.jpg"
Content-ID: <18791286ff2c6c62a691>
X-Attachment-Id: 18791286ff2c6c62a691