UPSC Prelims 2025 Q42: Science & Technology – Defence Technology
- (a) Only one
- (b) Only two
- (c) All the three
- (d) None
Answer: (d) None
Explanation
Statement-by-Statement Breakdown:
| Statement | Claim | Verdict | Why |
|---|---|---|---|
| Statement I | All UAVs can do vertical landing | FALSE | Only VTOL (Vertical Take-Off and Landing) UAVs - like multirotor drones and helicopter-type UAVs - can land vertically. Fixed-wing UAVs require a runway, catapult, or belly landing - they CANNOT land vertically. |
| Statement II | All UAVs can do automated hovering | FALSE | Hovering requires zero forward speed with active thrust underneath - only multirotors and VTOL UAVs can hover. Fixed-wing UAVs need continuous forward airspeed to generate lift - they CANNOT hover. |
| Statement III | All UAVs use battery only as power source | FALSE | UAVs use many power sources: gasoline/petrol engines (long-range UAVs), jet fuel (military drones like MQ-9 Reaper), hydrogen fuel cells (high-endurance), solar (HALE drones). Battery-only limits range and payload severely. |
All three statements are FALSE → Answer: None
UAV Types and Capabilities:
| Type | Vertical Landing | Hovering | Typical Power |
|---|---|---|---|
| Multirotor (DJI, quadcopter) | YES | YES | Battery |
| Fixed-wing (Global Hawk, Predator) | NO | NO | Gasoline/Jet fuel |
| VTOL fixed-wing (hybrid) | YES | Limited | Battery + motor |
| Helicopter UAV | YES | YES | Gasoline/Battery |
| Solar HALE (Zephyr) | Requires runway | NO | Solar |
India's UAV programme: Tapas (DRDO — medium-altitude long-endurance), Rustom series, Archer-NG.
MQ-9B SkyGuardian — India signed deal for 31 armed drones (US lease-purchase 2024).
Answer: (d) None.
Why each option is right or wrong
- (a) Incorrect. 'Only one' would mean exactly one statement is correct. All three statements are false — no statement is correct.
- (b) Incorrect. 'Only two' would require two statements to be true. Statement I fails (fixed-wing can't VTOL), Statement II fails (fixed-wing can't hover), Statement III fails (many UAVs use non-battery power).
- (c) Incorrect. 'All three' would require vertical landing, hovering, and battery-only to apply to ALL UAV types. Fixed-wing UAVs alone disprove both I and II, and large military UAVs disprove III.
- (d) CORRECT. All three statements incorrectly generalise capabilities that only apply to specific UAV subtypes (multirotors/VTOL). Fixed-wing UAVs cannot do VTOL or hover, and battery-only power is just one of several UAV propulsion options.
Key point
Fixed-wing UAVs CANNOT hover or land vertically. UAV power = gasoline, jet fuel, solar, hydrogen, or battery — NOT battery-only.
Remember
Fixed-wing UAVs CANNOT hover or land vertically. Battery-only is false — military UAVs run on gasoline and jet fuel. All 3 statements = FALSE.
Common mistakes
- Assuming all modern drones are multirotor-type — military UAVs like Global Hawk and Predator are fixed-wing.
- Thinking hovering is universal — it requires active downward thrust, impossible in fixed-wing designs.
- Assuming battery = universal UAV power — long-range surveillance UAVs (HALE) use petrol or jet fuel for 24h+ endurance.
Exam tip
Fixed-wing UAV = NO hover, NO vertical landing. Always think of the Predator or Global Hawk — plane-shaped drones that need runways. Only multirotors (like DJI-type drones) can hover and VTOL. Power diversity — battery, petrol, solar, hydrogen all exist in different UAV classes.
Sources
- DRDO Annual Report — UAV Development Programme (Tapas, Rustom)
- Ministry of Defence — Unmanned Systems Policy 2021
- NCERT Class XII — Physics (Principles of Flight — optional extension)