HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES
Risacher.org, 29 December 2011
http://www.risacher.org/rocket/
also
http://www.cientificosaficionados.com/libros/cohetes.pdf [PDF, 6.3M]
This excellent book, written by Leroy J. Krzycki in the 1960's provides a good theoretical and practical overview of developing your own liquid propellant rocket motors. Although dated, it provides timeless theoretical coverage in an understandable fashion. It covers all aspects from the motor to a suitable test system.
I will have to investigate this book after testing my second small liquid fueled rocket engine...hopefully it will work better than my first (pressure fed) lacquer fueled liquid engine.
ReplyDeleteHi i was reading the book my self and the problem for me is i dont know how to calculate the length of the combustion chamber if you have any suggestions
ReplyDeletethat would be great thanks
Alex,
ReplyDeleteThe length of a rocket chamber is usually designed in terms of what is known as L* (L Star). It is unique and specific for each propellant combination and motor design. It is actually a combination "rule of thumb" standing in place of the reactivity of the propellants, the velocity of propellants in the chamber, the quality of your injector and the size of your throat. Another way of looking at L* is to see it as the "dwell time" of the propellant in your chamber needed for adequate combustion.
If you look in the "DESIGN EQUATIONS" section of the book, in the "Combustion Chamber" section, they talk about L* (page 17 the version linked above).
If you look at this page:
http://www.braeunig.us/space/propuls.htm
you'll see a table with some suggested ranges.
In actuality, L* will need to be determined empirically, though the guidelines like the table above will help.
For a first-time approach, you might want to try something above 60 inches for a good starting point (but that's just a suggestion). If you've got a good injector with a fast reacting propellant, then you will be able to lower it, but a poorer injector might take a larger L*.
For more information, do a google search on the following search terms:
"l star" rocket engine
If you still need help, don't hesitate to ask more questions....
Cheers,
Ed L