1.

You are considering using N ₂O ₄/N ₂H ₄ bipropellant engines in your design. One of the potential engine manufacturers claims that he has an engine which will produce 2224 N thrust and a specific impulse of 327 s in a vacuum. Noticing your skepticism, he provides you with the following test data from a near-vacuum firing of the engine: a) pressure in the test chamber during firing = 2.482 kPa, b) measured thrust = 2157 N, c) measured propellant flow rate = 0.7049 kg/s, d) measured chamber pressure = 1965 kPa, and e) measured gas total temperature = 3283 K. The engine has a throat area of 6.5374 sq cm and an area ratio of 65. From other sources you know that the exhaust gas produced by this propellant combination has a molecular weight of 18.9 and the ratio of specific heats of 1.26. Do you believe this engine will achieve the expectations of the manufacturer? To decide:

1. Calculate the theoretical vacuum specific impulse of this engine, using frozen equilibrium assumptions.

2. Adjust the test data, thrust, and specific impulse, to vacuum conditions.

3. Compare adjusted specific impulse from the test to theoretical values.

4. Compare the adjusted specific impulse and thrust to claimed values.

2.

If a propulsion system delivers a thrust of 4448 N with a propellant flow rate of 1.474 kg/s, what is the specific impulse?