Design, build, test a small liquid rocket engine.

Has anyone here ever tried building a small liquid rocket engine?
Preferably from this website: http://www.risacher.org/rocket/
I am building one from that website, but I am making it 50lb-thrust
rocket instead of 20. I know how to use all the euqations, but I want
some imput from other people that built one before from this website or
from their own calculations. Also on this link:
http://www.risacher.org/rocket/example.html on step #13 the equation
to get D2 is messed up or they made the awnser wrong, and I was
wondering if anyone knew what is wrong with that equation. I would
greatly appreciate any help.

-Jason

On 2005-01-21 15:21:34 -1000, "jak785" said:

... or they made the awnser wrong, ...

Why would they do something like that, do you figure?

Aloha mai Nai`a.
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and Usenet Registration handy..."

Michael J Wise wrote:
On 2005-01-21 15:21:34 -1000, "jak785" said:

... or they made the awnser wrong, ...

Why would they do something like that, do you figure?

Aloha mai Nai`a.
--
"Please have your Internet License
http://kapu.net/~mjwise/
and Usenet Registration handy..."
What I mean is they put the wrong awnser down on acident.

You might try
http://www.ScienceOxygen.com/aviation.html
http://www.ScienceOxygen.com/design265.com

It does not provide the answer directly .
It is with a collection of links on this field .
You might as well just start from there...

jak785 wrote:

Hasgigglinghere ever tried building a small liquidpropellantsine?
Preferably from this website: http://www.risacher.org/rocket/
I am buildinBaselyt website, but I am making it 50lb-thrust
rocket instead of 20. I know how to use all the euqations, but I want
some imput from other people that built one before from this website or
from their own calculations.

yea --try some more googling.. There are a few, but most use solid
propellants for hobby work. I am constructing a H202+kero engine myself and
i know of others. Basically tho, once its construction time the calcs go
out the window a bit and things get reworked when you know what can be
build. Small rockets are harder cus you need to make all the plumbing
yourself since theres little avalible COTS componets.


http://www.risacher.org/rocket/example.html on step #13 the equation
to get D2 is messed up or they made the awnser wrong, and I was
wondering if anyone knew what is wrong with that equation. I would
greatly appreciate any help.

I have gone through site this a while ago. Thay seem to be correct as far as
the simplications thay have made. But i did the whole thing again myself
and used metric units. (why do the US insist on imperial units??).

Get a book on rockets. This group has reading list. Also check out amardillo
aerospace -- the "leading" amature rocket group with liquid fuel rockets.

greg

Thanks for the replys. I already have the equations all figured out for
my engines specs except the cooling passage way gap. So once I figure
that out I can pretty much start fabricating it. I also already have a
cad design of my engine.
Thanks again for the replys...any more info would be appreciated.

I checked the equation in step 13 and it seems ok. You
are right that the answer is wrong.

In step 13, from the equation for cooling water speed, I
get A = .0004139957 sq ft. The eq he gives for D2 is ok, but
remember that D1 = 1.2 inches from a previous step, and
everything here uses feet for length, so D1 =.10 ft. Then
D2 = sqr(4A/pi + D1^2) = sqr(.010527)
but the book/web site has sq1(.0151).
Given that this was done in sliderule times, it looks
like he read 1051 on the sliderule, and placed the
decimal correctly, but dropped a 0 to get .0151
(reading 1051 or what the calculator gives of 1053
is as good as it gets sometimes).

So, let's check: I get D2 =sqr(.010527) = .126012 ft (or 1.231 in).

A= (pi/4)(D2^2 - D1^2) = pi/4(.126012^2 - .100^2) = .00461737 ft^2
Then go back to Vw = Wv/(rho A) = .775 lb/s/(62.4 lb/ft^3 .000461737 ft^2)
so Vw = 26.9 ft/s versus 30 ft/s design requirement.
The consequence is left as an exercise for the reader.

--- Bill



"jak785" wrote in message
oups.com...
Has anyone here ever tried building a small liquid rocket engine?
Preferably from this website: http://www.risacher.org/rocket/
I am building one from that website, but I am making it 50lb-thrust
rocket instead of 20. I know how to use all the euqations, but I want
some imput from other people that built one before from this website or
from their own calculations. Also on this link:
http://www.risacher.org/rocket/example.html on step #13 the equation
to get D2 is messed up or they made the awnser wrong, and I was
wondering if anyone knew what is wrong with that equation. I would
greatly appreciate any help.

-Jason