UPSC Prelims 2022 Q34: Science & Technology – Defence Technology
Which one of the following statements best reflects the idea behind the 'Fractional Orbital
Bombardment System' often talked about in media?
- (a) A hypersonic missile is launched into space to counter the asteroid approaching the Earth and explode it in space.
- (b) A spacecraft lands on another planet after making several orbital motions.
- (c) A missile is put into a stable orbit around the Earth and deorbits over a target on the Earth.
- (d) A spacecraft moves along a comet with the same speed and places a probe on its surface.
Answer: (c) A missile is put into a stable orbit around the Earth and deorbits over a target on the Earth.
Explanation
Fractional Orbital Bombardment System (FOBS)
| Feature | Detail |
|---|---|
| Idea | A warhead is put into low Earth orbit, then de-orbited over its target before completing a full orbit — hence "fractional" |
| Origin | Soviet Union, 1960s |
| Advantage | Can approach from any direction (even over the South Pole), dodging early-warning radars that face north |
| Recent news | Reports in 2021 that China tested a hypersonic glide vehicle launched on a FOBS-like path |
| Law | The Outer Space Treaty (1967) bans weapons of mass destruction in orbit; FOBS exploits the 'fractional' gap |
Other options compared:
| Option | What it describes |
|---|---|
| (a) | Planetary defence, like NASA's DART mission |
| (b) | Orbital insertion before a landing |
| (d) | Comet rendezvous, like Rosetta and Philae |
Answer: (c) A missile is put into a stable orbit around the Earth and deorbits over a target on the Earth.
Why each option is right or wrong
- (a) Incorrect. Destroying an asteroid in space is planetary defence, not FOBS.
- (b) Incorrect. Orbiting a planet before landing is a normal space-probe manoeuvre.
- (c) CORRECT. FOBS puts a warhead into orbit and de-orbits it onto a target on Earth.
- (d) Incorrect. Matching a comet's speed and landing a probe describes Rosetta.
Key point
FOBS = warhead placed in low orbit, de-orbited onto a target before one full orbit; Soviet 1960s idea; China test reported 2021.
Remember
FOBS puts a missile into orbit and drops it on a target on Earth.
Common mistakes
- Confusing FOBS with asteroid defence because both involve missiles in space.
- Thinking FOBS completes many orbits; it de-orbits before completing one.
- Not knowing why FOBS worries planners — it avoids north-facing radar warning.
Exam tip
'Fractional orbit' = less than one full orbit. The weapon goes up, partly around, then down on the target.
Sources
- Outer Space Treaty, 1967 — Article IV
- Center for Strategic and International Studies — Missile Threat: Fractional Orbital Bombardment System (FOBS)