Defence Technology: UPSC Previous Year Questions (Science and Technology)

Explanation

Statement 1 is incorrect: Only Vertical Takeoff and Landing (VTOL) UAVs, like multi-rotor drones (e.g., DJI Phantom, Skydio quadcopters/hexacopters, 2014) and certain hybrid tilt-rotor drones, can land vertically. Fixed-wing UAVs (e.g., NASA Global Hawk, MQ-1 Predator, Wing Loong, 1994) require runways, catapults, or recovery systems (e.g., net, parachute) and cannot land vertically. Hybrid UAVs vary by design. Fixed-wing UAVs excel in energy efficiency, endurance, and speed, ideal for surveillance and long-range missions, unlike multi-rotor drones suited for precision tasks.

Statement 2 is incorrect: Only rotary-wing and multi-rotor UAVs (e.g., DJI Phantom, Skydio, 2014) hover, using vertical thrust from propellers with GPS/stabilization systems can do automated hovering. Fixed-wing UAVs (e.g., MQ-9 Reaper, Global Hawk, 2001) require forward motion for lift and cannot hover. Some VTOL-capable fixed-wing UAVs (e.g., tilt-rotor) can hover, but not universally. Hovering suits aerial photography, surveillance, delivery, and rescue.

Statement 3 is incorrect: UAVs use diverse power sources: batteries (Lithium-ion/LiPo for small/medium multi-rotor drones, e.g., DJI Mavic Air, Skydio, 2018), gasoline (military drones like MQ-9 Reaper, DRDO Rustom, Nishant, 2008), hybrid systems, solar (HALE UAVs like AeroVironment’s, 2010), or hydrogen fuel cells. Power choice depends on mission, endurance, range, and payload. Hence, option (d) is correct.

Explanation

CL-20 (Chemical Formula C₆H₆N₁₂O₁₂), HMX (High Melting Explosive Chemical Formula C₄H₈N₈O₈), and LLM-105 (2,6-Diamino-3,5-dinitropyrazine-1-oxide) are High-Energy Materials (HEMs)--specifically military explosives used in warheads, missiles, artillery shells, and detonators. They are not refrigerants or fuels, but nitroamine (CL-20, HMX) or nitro-substituted (LLM-105) compounds with high detonation velocities, thermal stability, and armor-penetration capability. CL-20: Developed in 1987 by U.S. Naval Air Warfare Center, it has 20% more energy than HMX. Indian variant (ICL-20) is made by DRDO’s High Energy Materials Research Laboratory (HEMRL). Used in Switchblade drones, AGM-158C missiles, and Arjun MBT shaped charges. HMX: It is one of the Standard explosives used in Agni, Prithvi, and nuclear weapons. Used in Plastic Bonded Explosives (PBX), torpedoes, and detonators. LLM-105: Designed for Insensitive Munitions (IM), Ideal for naval/aircraft munitions, explored by HEMRL.

Explanation

Pair 1 is correctly matched: Dornier -228 is known for their versatility, they are equipped for a range of missions, including maritime patrol, surveillance, pollution control, search and rescue, and medical evacuation.

Pair 2 is not correctly matched: The Ilyushin Il-76 is a strategic/heavy military transport aircraft, not a supersonic combat aircraft. HAL Tejas, MiG-21, Sukhoi Su-30MKI and Dassault Rafale are examples of supersonic combat aircraft.

Pair 3 is correctly matched: The C-17 Globemaster III is a large military transport aircraft used for airlift and cargo missions. The Indian Air Force (IAF) has received its third Boeing C-17 Globemaster III, a large, versatile military transport aircraft capable of carrying heavy, oversize loads long distances and landing on rough and unprepared surfaces.