Monomethylhydrazine
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Posts posted by Monomethylhydrazine
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I have been working on a rocket engine and I have cad models and everything and I am getting ready to build it. Then, I was running over the numbers one more time and I realized that the thrust I was getting was completely different from what I should have been getting.
The big problem is the nasa equations. It uses the variables Ttotal and Ptotal. NASA states, "pt is the total pressure in the combustion chamber, Tt is the total temperature in the combustion chamber." However, when I plug in 300 psi and 5742 degrees fahrenheit and the exhaust values for each variable as given by NASA's isentropic equations, I get a thrust of 735 pounds, whereas the first time I ran the numbers I got 32 pounds of thrust.
Here is my data, most of it was from a formula. The top ten rows are all givens. I got that information from https://risacher.org/rocket/eqns.html as I am building a gasoline-GOX engine.
What it is Value Unit Combustion pressure (Pc) 300 PSI Mixture Ratio 2.5 n/a Flame Temp 5742 Fahrenheit ISP 261 Seconds GOX Density 0.083 lb/ft^3 Gas Density 44.5 lb/ft^3 Nozzle Throat Cross Sectional Area 0.00173611 ft^2 Gas constant (R) 65 ftlb/lb Gamma (heat ratio) 1.2 gc (gravitation) 32 ft/second/second Tt (temperature of gasses at nozzle throat) 5637.618 Fahrenheit Tc (temperature of cumbustion flame) 6202 Rankine Pt (gas pressure at nozzle throat) 169.2 PSI Me (mach number of gasses at exit) 2.55 Area Exhaust/Area throat 3.65 Temperature Exhuast/Temperature combustion 0.606 Thrust 31.84104294 Pounds Mass flow rate 0.0009229501076 pounds per second Exhaust velocity 1380.669321 ft/second Temperature Exhuast 3479.652 Fahrenheit Exhaust pressure 24.4297 psi As you might imagine, I would really appreciate someone going over and double checking my numbers. Thank you so much!
0
Large Hybrid Model Rocket
in Engineering
Posted
http://www.ukrocketman.com/rocketry/hybridscience.shtml
I know I am a little late to the party, but check this website out. I am a liquid bi propellant rocket guy so I am by no means someone who knows hybrid rocketry. But I skimmed this and it looks good. I think it could really help you.
http://www.arocketry.net/solid.html
That website could help you with the safety part. Rocketry is dangerous and I do not want you to hurt yourself. Or anyone for that matter. I am putting this out there, I am not liable for anyone getting hurt using the information I provide.
I wish you good luck and be safe!