250+ TOP MCQs on Liquid Propellants and Answers

Rocket Propulsion Multiple Choice Questions on “Liquid Propellants”.

1. What kind of propulsion is used for trajectory adjustments and attitude corrections?
a) Boosting propulsion
b) Auxiliary propulsion
c) Sustaining propulsion
d) Cryogenic propulsion
Answer: b
Clarification: Auxiliary propulsion helps in trajectory adjustments and attitude corrections. Boosting propulsion imparts a high velocity to the payload. Boosting and auxiliary propulsion are one way of classifying liquid rocket engines.

2. How are liquid rocket engines classified on the basis of their feed system?
a) Pressurized or turbopump
b) Restartable or single fired
c) Single flight or reusable
d) Boosting or auxiliary
Answer: a
Clarification: Feed system is used for the transfer of the liquid propellants from their storage tank to the thrust chamber of the rocket engine. They can be a gas-pressurized feed system or turbo pump feed system.

3. The thruster is also called as _____________
a) combustion chamber
b) thrust chamber
c) nozzle
d) injector
Answer: b
Clarification: Thruster is the same as the thrust chamber of a rocket engine. It is the combination of the injector, combustion chamber and the nozzle.

4. Which of the following ways of thrust chamber cooling may use niobium metal?
a) Film cooling
b) Cooling jacket
c) Radiation cooling
d) Ablative cooling
Answer: c
Clarification: Niobium is a special high temperature material that can radiate excess heat. So it is used as part of the radiation cooling of the thrust chamber.

5. At what temperature are the liquid oxygen and the liquid hydrogen kept in their storage tanks of the cryogenic rocket engine?
a) -253°C and -183°C
b) -183°C and -253°C
c) -253°C for both
d) -183°C for both
Answer: b
Clarification: Liquid oxygen is stored at -183°C and liquid hydrogen is stored at -253°C. Extensive care is taken to ensure that the vaporization losses are minimized for the cryogenic propellants.

6. Determine the mixture ratio if mass flow rate of the oxidizer is 3/4 times the total mass flow rate of the combustion products.
a) 2.5
b) 3
c) 2
d) 1
Answer: b
Clarification: Assuming the combustion gases are purely a result of the propellants and using mass conservation, mcomb = mo + mf.
mo = 3/4 mcomb
So, mf = 1/4 mcomb
Mixture ratio r = mo / mf = 3.

7. If the total propellant flow rate is 24 kg/s and the mixture ratio is 2.3, determine the mass flow rate of the oxidizer.
a) 19.67 kg/s
b) 15.33 kg/s
c) 12.94 kg/s
d) 16.73 kg/s
Answer: d
Clarification: mo = r m/(r+1)
= 2.3 x 24/(3.3) = 16.73 kg/s.

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