Read the following statements marked as Assertion (A) and Reason (R). Choose the correct option. Assertion (A): The development of Spark Torch Igniters is essential for the feasibility of fully reusable rocket booster stages and spacecraft requiring multiple engine firings in orbit. Reason (R): Spark Torch Igniters provide highly reliable and repeatable ignition capability in vacuum conditions, a critical requirement for successive engine restarts during complex mission profiles.

Correct — A. The key reads both statements as true and R as the reason for A.

R: a spark torch igniter uses an electric spark to light a small torch flame, which then lights the engine. It can do this again and again, in vacuum, which is what successive restarts demand.

R explains A: a reusable booster must relight its engines to fly back and land, and a spacecraft must relight for each burn in orbit. Repeatable ignition serves both → option (a).

Why the others are wrong

• (b)
  Both A and R are true, but R is not the correct explanation of A — Treats R as a separate truth, but R names the capability A rests on — repeatable ignition for multiple restarts — so the key counts R as A's explanation.
• (c)
  A is true, but R is false — R is not false. Torch igniters relight from a spark, and Raptor uses them in its preburners while needing none of Merlin's consumable igniter fluid.
• (d)
  A is false, but R is true — The key holds A true: stages that fly back to land and spacecraft that fire repeatedly in orbit both need reliable restarts, the need A ties to torch igniters.

An engine that fires more than once needs a way to relight, and designs differ. Merlin, the engine of the reusable Falcon 9 booster, uses a dedicated, consumable igniter fluid. Raptor uses torch igniters and needs none.

Hypergolic propellants need no igniter at all: they ignite on contact, so an engine can fire any number of times until the propellant runs out. The Space Shuttle's orbital manoeuvring engines and Dragon's Draco thrusters use them.

Key facts

• A torch igniter uses an electric spark to light a small flame that ignites the engine, and it can be fired repeatedly.
• Falcon 9's booster is recovered for reuse by landing vertically on one of its nine Merlin engines.
• Raptor uses torch igniters in its preburners and needs none of Merlin's consumable igniter fluid.
• Hypergolic propellants ignite on contact, so engines that burn them need no ignition system.

Common traps

• Accepting a sweeping word like essential without testing it — check absolute words in A before judging the link.
• Marking R as unrelated because both statements sound technical — ask whether R names the capability A depends on.

No directly related past PYQ was found.