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MIT Rocketlab's How to Design Build and Operate Liquid Fueled Rocket Engines



 
 
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  #1  
Old October 30th 04, 10:07 AM
David Findlay
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Default MIT Rocketlab's How to Design Build and Operate Liquid Fueled Rocket Engines

Anyone here used the information from this book? I'm trying to do some
design based on it, although I've found in a couple of places the formula's
make great leaps with no explanation. The main one I'm having problems with
is Step 9.

start quote
The chamber length is found from Eq. (21)


Vc = (1.1) (Ac Lc)


However, we must first determine the chamber area or Ac. We do this by
assuming that the chamber diameter is five times the nozzle throat diameter
or Dc = 5Dt, therefore


Dc = 1.2 in. and Ac = 1.13 in2
Therefore,


Lc = Vc/(1.1)(1.13) = 2.67/1.245 = 2.15 in
end quote

Having a chamber volume of 2.67 in^3 and calculating the the chamber
diameter by Dc = 5Dt, the cross-sectional area of the chamber should be Ac
= 2 pi r = pi * Dc as far as I can tell. But they introduce a figure 1.13
in^2 for Ac, with no explanation. On the formula page they provide a
formula for Ac:

Ac = Dc^2 / 4

This produces a value of 0.35 in^2. Any ideas on what is going on here? What
is the correct value? I've been trying to follow their example so I can
build and validate a spreadsheet for such calculations, but I'm stuck here.
I've also been trying to convert the formulae to metric. Has anyone already
converted it?

Secondly, is there a better publication out there to superseed this book?
This book is aimed at static test articles, do other publications apply
more to flight articles? Lastly, how well will these values apply to an
aerospike type of engine, specifically an annular version? Would I be able
to use the same areas and volumes effectively? Thanks,

David

P.S. Sorry for the cross post, but being a historical book now I think it's
relavent to both.
  #2  
Old October 30th 04, 10:47 PM
Darren J Longhorn
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Default

On Sat, 30 Oct 2004 19:07:56 +1000, David Findlay
wrote:

Anyone here used the information from this book?


Try the arocket email list.

  #3  
Old October 30th 04, 10:54 PM
David Findlay
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Posts: n/a
Default

Anyone here used the information from this book?

Try the arocket email list.


Thanks, that's an awesome site. Thanks,

David
  #4  
Old November 1st 04, 05:19 PM
Ray Schmitt
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Posts: n/a
Default

The classic text on liquids is George Sutton's "Rocket Propulsion Elements".
Sutton spent years working at Rocketdyne. The book was written over 40 years
ago, has been continually revised, and now is in its 7th edition.

Also Huzel and Huang's "Modern Engineering for Design of Liquid-Propellant
Rocket Engines (Progress in Astronautics and Aeronautics, Vol 147)" is good.
It's more recent (1992). H & H usually fill in the gaps between equations.

Both are available at Amazon.com but are pricy. Any university science
library will have copies.

Later
Ray Schmitt


"David Findlay" wrote in message
...
Anyone here used the information from this book? I'm trying to do some
design based on it, although I've found in a couple of places the

formula's
make great leaps with no explanation. The main one I'm having problems

with
is Step 9.

start quote
The chamber length is found from Eq. (21)


Vc = (1.1) (Ac Lc)


However, we must first determine the chamber area or Ac. We do this by
assuming that the chamber diameter is five times the nozzle throat

diameter
or Dc = 5Dt, therefore


Dc = 1.2 in. and Ac = 1.13 in2
Therefore,


Lc = Vc/(1.1)(1.13) = 2.67/1.245 = 2.15 in
end quote

Having a chamber volume of 2.67 in^3 and calculating the the chamber
diameter by Dc = 5Dt, the cross-sectional area of the chamber should be Ac
= 2 pi r = pi * Dc as far as I can tell. But they introduce a figure 1.13
in^2 for Ac, with no explanation. On the formula page they provide a
formula for Ac:

Ac = Dc^2 / 4

This produces a value of 0.35 in^2. Any ideas on what is going on here?

What
is the correct value? I've been trying to follow their example so I can
build and validate a spreadsheet for such calculations, but I'm stuck

here.
I've also been trying to convert the formulae to metric. Has anyone

already
converted it?

Secondly, is there a better publication out there to superseed this book?
This book is aimed at static test articles, do other publications apply
more to flight articles? Lastly, how well will these values apply to an
aerospike type of engine, specifically an annular version? Would I be able
to use the same areas and volumes effectively? Thanks,

David

P.S. Sorry for the cross post, but being a historical book now I think

it's
relavent to both.



 




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