# Exhaust Velocity Calculation

#### .:Endeavour:.

Please check my calculations for the exhaust velocity of a rocket that uses Nitrogen Tetroxide (N2H4) & Aerozine 50 as its propelants. This is the formula that I'm using to find out the exhaust velocity:

$V_e = \sqrt{{\frac{T*R}{M}}*{\frac{2*k}{k-1}}*[1-(P_e/P)^(^k^-^1^)^/^k] }$

Ve = Exhaust velocity at nozzle exit, m/s
T = absolute temperature of inlet gas, K
R = Universal gas law constant = 8314.5 J/(kmol·K)
M = the gas molecular mass, kg/kmol (also known as the molecular weight)
k = cp / cv = isentropic expansion factor
cp = specific heat of the gas at constant pressure
cv = specific heat of the gas at constant volume
Pe = absolute pressure of exhaust gas at nozzle exit, Pa
P = absolute pressure of inlet gas, Pa

T = 3110 Kelvin
R = 8314.5
M = 20.24
k = 1.2314
Pe = Pa = 1 atm
P = 25 atm

$$V_e = \sqrt{1,277,573.864 * 10.643 * 0.454}$$

$$V_e = \sqrt{6,173,137.26}$$

Ve = 2,484.5799 meters per second

Are this calculations correct or did I make a mistake? I got the equation and most of the data from these two sites: http://en.wikipedia.org/wiki/Rocket_engine_nozzles, http://www.braeunig.us/space/problem.htm#1.10, and http://www.braeunig.us/space/comb-NA.htm.

Last edited by a moderator:
Related General Engineering News on Phys.org

#### JBA

In spite of the obtuseness of the presented equation the equation is correct; but, I haven't verified the numerical result.

"Exhaust Velocity Calculation"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving