UPSC Prelims 2008 Q110: Science & Technology – Space Technology & Astronomy
Consider the following statements in respect of a jet engine and a rocket:
1. A jet engine uses the surrounding air for its oxygen supply and so is unsuitable for motion in
space.
2. A rocket carries its own supply of oxygen in the gas form, and fuel.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (c) Both 1 and 2
Explanation
Checking two claims about jet engines and rockets
These two propulsion systems differ fundamentally in how they obtain the oxygen needed for combustion.
| Statement | Verdict | Reason |
|---|---|---|
| 1. Jet engine uses surrounding air for oxygen, unsuitable for space | Correct | A jet engine draws in atmospheric air for combustion, making it unusable in the vacuum of space, where there's no air |
| 2. A rocket carries its own oxygen supply and fuel | Correct | A rocket carries its own oxidizer (supplying oxygen) along with fuel, allowing it to operate independent of the atmosphere, including in space |
Jet engine vs rocket:
| Point | Jet Engine | Rocket |
|---|---|---|
| Oxygen source | Surrounding atmospheric air | Onboard oxidizer |
| Works in space? | No | Yes |
Answer: (c) Both 1 and 2.
Why each option is right or wrong
- (a) Incorrect. Statement 2 (rocket's onboard oxygen/fuel supply) is also correct, so '1 only' is incomplete.
- (b) Incorrect. Statement 1 (jet engine's atmospheric dependency) is also correct, so '2 only' is incomplete.
- (c) CORRECT. Both the jet engine's atmospheric dependency and the rocket's self-contained oxidizer/fuel supply are accurate.
- (d) Incorrect. Since both statements are accurate, 'neither' is wrong.
Key point
A jet engine depends on atmospheric air for oxygen (making it unusable in space), while a rocket carries its own oxidizer and fuel, allowing it to operate independent of the atmosphere — both statements are accurate.
Remember
Jet engines rely on atmospheric air for oxygen (unsuitable for space); rockets carry their own oxygen supply and fuel, enabling space travel.
Common mistakes
- Confusing the jet engine's atmospheric dependency with the rocket's self-contained propulsion system.
- Not understanding why jet engines cannot function in the vacuum of space.
- Assuming only one of the two closely related propulsion-system facts can be true at once.
Exam tip
Jet engines need atmospheric air (fail in space). Rockets carry their own oxidizer + fuel (work in space). A fundamental propulsion-system distinction.
Sources
- NCERT Class XI Physics — Laws of Motion (rocket propulsion)
- Encyclopaedia Britannica — jet engine