# Rocket Propulsion Questions and Answers – Multiple Rocket Propulsion Systems Performance

This set of Rocket Propulsion Multiple Choice Questions & Answers (MCQs) focuses on “Multiple Rocket Propulsion Systems Performance”.

1. For a rocket with an initial mass of 15,000 kg and carrying a payload of 1000 kg, determine the velocity change if it was ground launched and has an equivalent exhaust velocity of 3000 m/s. Assume the structural mass coefficient to be 0.24.
a) 3533 m/s
b) 3967 m/s
c) 3706 m/s
d) 4295 m/s

Explanation: Payload ratio λ = 1000/(15000 – 1000) = 0.0714.
∆V = Ueqln((1+λ)/(ε+λ))
= 3000 x ln(1.0714/0.3114)
= 3706 m/s.

2. If δ denotes inert mass fraction and λ denotes the payload fraction, what is the formula for parametric mass ratio (r)?
a) r = δ/λ
b) r = λ/δ
c) r = λ – δ
d) r = λ + δ

Explanation: Inert mass fraction is given by the formula δ = min/mo, where min denotes inert mass and mo denotes initial mass of the rocket. Payload mass fraction is λ = mpl/mo, where mpl is the payload mass. Parametric mass ratio is the sum of both the above ratios.

3. Overall engine specific impulse is influenced by ____________
a) nozzle area ratio and chamber pressure
b) nozzle area ratio only
c) chamber pressure only
d) neither nozzle area ratio nor chamber pressure

Explanation: In addition to the influence of nozzle area ratio and chamber pressure, the overall engine specific impulse also depends on the engine cycle and mixture ratio on a lesser extent.

4. Which of the following ranges describes the typical value of mixture ratio in the engines: SSME, RS-68, LE-5A and Vulcan?
a) 4-7
b) 12-15
c) 1-4
d) 15-20

Explanation: All of the engines use LOX and LH propellants. Mixture ratio for SSME, RS-68, LE-5A and Vulcan are 6, 6, 5, 6 and 5.35 respectively.

5. Which of the following engines were used in Ariane 5 vehicle?
a) RS-68
b) Vulcain
c) HM7(A)
d) RL 10-B2

Explanation: Ariane 5 uses Vulcain engine. The engine makes use of a gas generator cycle. RS-68 (Rocket System 68) was used in the first stage of the Delta IV rocket. HM7 was used as an upper stage engine in Ariane 1. RL 10-B2 was used in Delta 3 and Delta IV launch vehicles.
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6. YF 73 engine was used by which of these vehicles?
a) Space Shuttle
b) HII
c) Long March
d) Ariane 2

Explanation: YF 73 was used by the Long March vehicle. LE-5A and LE-7 were used in HII and SSME was used for Space Shuttle.

7. Which of the following describes the typical range of specific impulse in vacuum produced by the major LOX and LH propellant driven engines?
a) 400-500 s
b) 300-400 s
c) 150-300 s
d) 0-150 s

Explanation: Major LOX and LH propellant engines like SSME, RS68 and LE-5A produce specific impulses of 452.5s, 415s and 452s respectively. All of such engines are capable of producing specific impulse values above 400s.

8. LE-5A rocket engine and its derivatives were designed by ____________
a) France
b) India
c) China
d) Japan

Explanation: LE-5A and its derivatives were designed by Japan. It was designed to meet the upper stage requirements of H-I and H-II series of launch vehicles.

9. The kind of ignition system that allows multiple restarts for an engine is ____________
a) pyrotechnic igniter
b) spark igniter
c) hypergolic igniter
d) pyrotechnic initiator

Explanation: Pyrotechnic igniter and pyrotechnic initiator are same. Spark igniter is capable of multiple restarts while the other two – hypergolic and pyrotechnic igniters are single use ignition systems.

10. Which of the following has metal oxide pyrotechnic composition?
a) ZPP
b) Ni-Al laminate
c) ZHPP
d) HMTD

Explanation: ZPP is Zirconium Potassium Perchlorate. It is one of the most common initiators and called NASA Standard Initiator. ZHPP is a metal hydride-oxidizer, HMTD is a highly explosive organic compound and Nickel-aluminum laminates are used in electrically initiated pyrotechnic igniters.

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