This document summarizes the design of a 500N ethanol/lox rocket engine. It provides key parameters such as an O/F ratio of 3.2 and a chamber pressure of 290 psi. Flow rates include 0.06348 kg/s of fuel and 0.20313 kg/s of oxidizer. Based on these parameters and equations of rocket engine design, it calculates pressure and temperature values at different locations in the engine. It then determines the throat area of 0.2864 in^2 and exit area based on an expansion ratio of 3.8075997. Manufacturing constraints such as a 50mm inlet diameter and 30 inch chamber length are also specified. CFD analysis is recommended to finalize the design.

1. 500N Ethanol/Lox
engine
Design Study

2. Key constants
• Molecular weight of exhaust(𝜛 there are no other symbols
rip):28.1622
Gas constant:𝑅 =
1544
𝜛
ft/ °R
Gravity: 32.2 𝑓𝑡/𝑠2

3. Key Parameters
O/F= 3.2
Chamber pressure(Pc): 290.0755 PSI
Chamber Temperature: 2677K=4818°R

4. Flow rates
Propellant mass flow rate:
Fuel(ṁf):0.06348 kg/s
Oxidizer(ṁo): 0.20313kg/s
Exhaust mass flow rate(ṁe): 0.587kg/s

5. 𝑝𝑖𝑛𝑗 =
𝑃𝑐(1 + 𝛾(𝑀𝑖)2)
(1 +
𝛾 − 1
2
𝑀𝑖
2
)
𝛾
𝛾−1
Pressure @ injector(Pinj): 296.5663904 PSI
𝑝𝑖 =
𝑝𝑖𝑛𝑗
1 + 𝛾(𝑀𝑖)2
Pressure @inlet (Pi) : 283.452732 PSI

6. 𝑝𝑡 = 𝑝𝑐(
2
𝛾 + 1
)
𝛾
𝛾−1
Pressure at Throat: 166.22880028 PSI

7. Expansion Ratio(𝜀) selection

8. Expansion Ratio
Therefore, 𝜀=3.8075997
𝜀 =
𝐴𝑒
𝐴𝑡
=
2
𝛾 + 1
1
𝛾−1
(
𝑝𝑐
𝑝𝑒
)
1
𝛾
𝛾 + 1
𝛾 − 1
1 − (
𝑝𝑒
𝑝𝑐
)
𝛾−1
𝛾

9. Temperatures
𝑇𝑖𝑛𝑗 = 𝑇𝑐 = 2677k = 4818°R
𝑇𝑥 = 𝑇𝑐
𝑃𝑥
𝑃𝑐
𝛾−1
𝛾
Ti(inlet stagnation temp)=4802.95712380 °R
Tt(Throat stagnation temp)= 4468.144301°R
Te(exit stagnation temp)= 3217.25011°R

10. Specific Volume(essential for
Chamber Volume)
• 𝑉
𝑥 =
𝑅𝑇𝑥
144𝑃𝑥
• Throat=10.23385216 ft^3/lb
• Exit= 83.35024137 ft^3/lb
• Chamber= 6.185336216 ft^3/lb

11. Areas
• Gas flow rate=
144 𝑊𝑡𝑐 𝑉𝑥
𝑣𝑥
• 𝑊𝑡𝑐 = 0.587 lb/s
• At= 0.2864443282 in^2
• Ae= At* 𝜀

12. • Set Inlet diameter according to your
manufacturing limits.
50mm dia for my case!!
• L* is set a 30 inches for my application.
• 𝐿∗
=
𝑉𝑐
𝐴𝑡
, where Vc is volume of Chamber.

13. CFD!!!