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. ✓ UPSC's answer
(d) A spacecraft moves along a comet with the same speed and places a probe on its surface.

Why the answer is (c)

• A Fractional Orbital Bombardment System (FOBS) places a nuclear warhead into a low Earth orbit and then, before completing a full orbit, fires a retro-rocket to deorbit it onto a target — option (c).

• Because it can approach from any direction (e.g. over the South Pole) and at low altitude, it evades early-warning radars designed for ballistic trajectories.

• The Soviet Union deployed a FOBS in the 1960s–80s; China's 2021 test of a hypersonic glide vehicle launched by a fractional orbital system revived the term in the media.

• The other options describe asteroid deflection, planetary landing and comet rendezvous (like Rosetta–Philae), none of which is FOBS.

• Hence option (c).

Why the other options are wrong

(a) A hypersonic missile is launched into space to counter the asteroid approaching the Earth…: Asteroid interception is planetary defence, not FOBS.
(b) A spacecraft lands on another planet after making several orbital motions.: Orbiting before landing on a planet is a spacecraft manoeuvre, not a weapon system.
(d) A spacecraft moves along a comet with the same speed and places a probe on its surface.: Matching a comet's speed to place a probe describes a mission like Rosetta, not FOBS.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2022, held on 5 June 2022. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.