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Space & Defence Technology — UPSC Prelims Science & Environment previous year questions
20 free solved previous year questions on Space & Defence Technology, papers from 2003 to 2026, drawn from UPSC CSE Prelims, State PCS, covering statement-based, direct, match and assertion questions. Every answer key has been checked again against published sources and solved independently, and each explanation is written fresh.
Read all 20 questions with answers
- #1UPSC CSE 2026Which of the following statements with regard to stealth technology is/are correct ?1. Stealth objects have a very small radar cross-section and are coated with Radar Absorbing Material.2. Stealth objects can be detected using specific frequencies.3. Stealth objects are coated with metamaterials to increase the scattering of electromagnetic radiation.Select the answer using the code given below :
- A1 only
- B2 and 3 only
- C1 and 2 only
- D1, 2 and 3
Answer: (C) 1 and 2 onlyExplanation
Statement 1 is correct. Stealth objects have a very small radar cross-section, which is how large they look on radar. They are coated with radar-absorbing material to soak up radar energy.
Statement 2 is correct. Some radars can still detect stealth objects, for example low-frequency or special radars.
Statement 3 is wrong. Stealth coatings are used to cut or redirect scattering, not to increase it.
So 1 and 2 only.
Remember: stealth cuts detection chance; it does not make an object invisible.Source: DRDO and Ministry of Defence notes on stealth technology; standard radar physics
- #2UPSC CSE 2026Which of the following statements with regard to Black Boxes used in modern aircrafts is/are correct ?1. They carry a beacon emitting red light pulses to facilitate underwater detection.2. They record both the cockpit voice and flight data.3. Their memory units are made using either stainless steel or titanium.Select the answer using the code given below :
- A1 only
- B2 and 3 only
- C1 and 2 only
- D1, 2 and 3
Answer: (B) 2 and 3 onlyExplanation
Statement 1 is wrong. The beacon on a black box sends out ultrasonic sound pings under water, not red light pulses. It helps divers find the box.
Statement 2 is correct. The black box has two recorders. The Cockpit Voice Recorder records pilots' talk. The Flight Data Recorder records flight parameters.
Statement 3 is correct. The crash-proof memory unit is built in stainless steel or titanium.
So 2 and 3 only.
Remember: black boxes are actually painted bright orange so that they can be found.Source: DGCA and ICAO notes on flight recorders (Annex 6)
- #3UPSC CSE 2026Consider the following statements with regard to involvement of private entities in India’s space programme :1. The Indian National Space Promotion and Authorisation Centre (IN-SPACe) is an autonomous agency formed to facilitate participation of private entities.2. Agnikul Cosmos launched the world’s first flight using 3D-printed rocket engine.3. Skyroot Aerospace has developed liquid fuel for GSLV.Which of the statements given above is/are correct ?
- A1 only
- B2 and 3 only
- C1 and 2 only
- D1, 2 and 3
Answer: (C) 1 and 2 onlyExplanation
Statement 1 is correct. IN-SPACe is an autonomous body under the Department of Space. It authorises and promotes private firms in space activity.
Statement 2 is correct per the official key. Agnikul Cosmos flew a rocket using a single-piece 3D-printed engine, which was a world first.
Statement 3 is wrong. Skyroot Aerospace builds its own Vikram rockets. It did not develop liquid fuel for the GSLV, which is an ISRO vehicle.
So 1 and 2 only.
Remember: Skyroot's Vikram-S in 2022 was India's first private rocket launch.Source: Department of Space, IN-SPACe; ISRO and Agnikul press releases
- #4UPSC CSE 2026Which of the following statements with regard to drone swarms is/are correct ?1. They use Terahertz band of frequency to communicate with the command centre.2. Individual drones in the swarm can communicate with other drones in the swarm.3. GPS Spoofing is a commonly used technique to counter drone swarm attack.Select the answer using the code given below :
- A1 only
- B2 and 3 only
- C1 and 2 only
- D1, 2 and 3
Answer: (B) 2 and 3 onlyExplanation
Statement 1 is wrong. Drone swarms do not generally use the Terahertz band to talk to the command centre. They use ordinary radio links.
Statement 2 is correct. Each drone in a swarm talks to the others. This lets the swarm act together.
Statement 3 is correct. GPS spoofing sends fake satellite signals. It can mislead the drones' navigation, so it is used to counter a swarm.
So 2 and 3 only.
Remember: GPS jamming blocks the signal; GPS spoofing gives a false one.Source: Ministry of Defence and DRDO notes on UAS and counter-drone systems
- #5UPSC CSE 2026Consider the following statements about Mission Sudarshan Chakra of India :1. It aims to enhance India’s air defence, ballistic missile defence and aerial offensive capabilities.2. This Mission is being designed to enhance rapid, precise, and powerful defence responses, reinforcing India’s strategic autonomy.3. One of the aims of this Mission is to cover all public places of India by an expanded nationwide security shield by 2035.Which of the statements given above is/are correct ?
- A1, 2 and 3
- B1 and 2 only
- C2 and 3 only
- D1 only
Answer: (A) 1, 2 and 3Explanation
Mission Sudarshan Chakra was announced by the Prime Minister on 15 August 2025. It is a national mission to shield India from aerial and missile threats.
Statement 1 is correct. It aims to strengthen air defence, ballistic missile defence and aerial offensive capability.
Statement 2 is correct. The Mission is designed for fast, precise and strong defence responses and supports strategic autonomy.
Statement 3 is correct. One aim is to cover all public places with a wider security shield by 2035.
So 1, 2 and 3.
Remember: the Mission is a home-grown effort in the Atmanirbhar Bharat push.Source: Press Information Bureau, Prime Minister's Independence Day address 2025
- #6UPSC CSE 2026Which of the following items of defence hardware is/are manufactured in India ?1. Su-30 MKI Fighter Jets2. T-90 MK-III Tanks3. Akula Class SubmarineSelect the answer using the code given below :
- A1 and 2
- B1 and 3
- C1 only
- D2 only
Answer: (A) 1 and 2Explanation
Item 1 is correct. Hindustan Aeronautics Limited builds the Su-30 MKI in India under licence.
Item 2 is correct. The T-90 tank is made in India at the Heavy Vehicles Factory in Avadi.
Item 3 is wrong. The Akula class submarine is of Russian origin. India has operated one on lease, and it is not made in India.
So 1 and 2 only.
Remember: India's own nuclear submarines are built under the Advanced Technology Vessel (ATV) programme.Source: Ministry of Defence, annual reports (HAL, Heavy Vehicles Factory)
- #7UPSC CSE 2026Which one of the following pairs is not correctly matched ?(Indian Army Corps) : (Headquarters)
- A3 Corps : Dimapur
- B4 Corps : Tezpur
- C14 Corps : Leh
- D33 Corps : Srinagar
Answer: (D) 33 Corps : SrinagarExplanation
3 Corps has its headquarters at Rangapahar near Dimapur, Nagaland. This pair is correct.
4 Corps has its headquarters at Tezpur, Assam. This pair is correct.
14 Corps has its headquarters at Leh, Ladakh. This pair is correct.
33 Corps has its headquarters at Sukna near Siliguri in West Bengal, not at Srinagar. So this pair is not correctly matched.
The Srinagar corps is 15 Corps (Chinar Corps).
Remember: 14 Corps is called the Fire and Fury Corps.Source: Indian Army official website, formations
- #8UPSC CSE 2026The Bureau of Indian Standard (BIS) recently introduced a national standard to test and assess bomb disposal system. Which of the following statements with regard to this system is/are correct ?1. The new standard is known as IS 19445 : 2025.2. It will improve interoperability of equipment across agencies.3. It was developed by TBRL, DRDO in collaboration with the 30th Central Scientific Research Institute, Russia.Select the answer using the code given below :
- A1, 2 and 3
- B2 and 3 only
- C1 and 2 only
- D1 only
Answer: (C) 1 and 2 onlyExplanation
Statement 1 is correct. The Bureau of Indian Standards issued IS 19445:2025 for the performance and requirements of bomb disposal systems.
Statement 2 is correct. A common standard helps equipment of different agencies work together. This is called interoperability.
Statement 3 is wrong. The standard was not made with a Russian institute. It was developed through the BIS process, led by TBRL of DRDO.
So 1 and 2 only.
Remember: TBRL is the Terminal Ballistics Research Laboratory, in Chandigarh.Source: Bureau of Indian Standards, IS 19445:2025; PIB release
- #9UPSC CSE 2025With reference to Unmanned Aerial Vehicles (UAVs), consider the following statements:I. All types of UAVs can do vertical landing.II. All types of UAVs can do automated hovering.III. All types of UAVs can use battery only as a source of power supply.How many of the statements given above are correct?
- AOnly one
- BOnly two
- CAll the three
- DNone
Answer: (D) NoneExplanation
None of the statements is correct.
Statement I is incorrect. Fixed-wing UAVs need a runway, a net or a parachute to land. Only rotary-wing and some hybrid types land vertically.
Statement II is incorrect. Hovering needs rotors or a similar design. Fixed-wing UAVs must keep moving forward.
Statement III is incorrect. UAVs also use fuel engines, hybrid systems and solar power.
So the answer is none.
Remember: Quadcopters can hover. Fixed-wing drones cannot.Source: Ministry of Civil Aviation, Drone Rules 2021; DRDO and ISRO material on UAV types
- #10UPSC CSE 2025What is the common characteristic of the chemical substances generally known as CL-20, HMX and LLM-105, which are sometimes talked about in media?
- AThese are alternatives to hydro-fluorocarbon refrigerants
- BThese are explosives in military weapons
- CThese are high-energy fuels for cruise missiles
- DThese are fuels for rocket propulsion
Answer: (B) These are explosives in military weaponsExplanation
CL-20, HMX and LLM-105 are high-energy explosives used in military weapons.
HMX is a well-known military explosive. CL-20 is more powerful still. LLM-105 is valued because it is less sensitive to shock.
Option (a) is wrong. Refrigerant substitutes are chemicals such as hydrofluoroolefins, not explosives.
Options (c) and (d) are wrong. Fuels burn steadily, while these compounds detonate.
So option (b) is right.Source: DRDO and Ministry of Defence press releases on energetic materials
- #11UPSC CSE 2025Consider the following space missions:I. Axiom-4II. SpaDeXIII. GaganyaanHow many of the space missions given above encourage and support micro-gravity research?
- AOnly one
- BOnly two
- CAll the three
- DNone
Answer: (B) Only twoExplanation
Only two of the three missions support microgravity research.
Axiom-4 carried Indian experiments, including microgravity studies, to the International Space Station.
Gaganyaan will take Indian astronauts to low Earth orbit. It gives India a microgravity platform for research.
SpaDeX was mainly a demonstration of docking two small satellites in space. Microgravity research was not its purpose.
So the answer is only two.
Remember: SpaDeX made India the fourth country to demonstrate space docking.Source: ISRO press releases on Axiom-4, SpaDeX and Gaganyaan
- #12UPSC CSE 2025With reference to India's defence, consider the following pairs:Aircraft type – DescriptionI. Dornier-228 : Maritime patrol aircraftII. IL-76 : Supersonic combat aircraftIII. C-17 Globemaster III : Military transport aircraftHow many of the pairs given above are correctly matched?
- AOnly one
- BOnly two
- CAll the three
- DNone
Answer: (B) Only twoExplanation
Pairs I and III are correctly matched.
Pair I is correct. The Dornier-228 is a light aircraft. The Indian Navy and Coast Guard use it for maritime patrol.
Pair II is incorrect. The IL-76 is a heavy transport aircraft, not a supersonic combat aircraft.
Pair III is correct. The C-17 Globemaster III is a strategic military transport aircraft.
So only two pairs are correct.
Remember: Supersonic combat aircraft in India include the Rafale, Su-30MKI and Tejas.Source: Ministry of Defence and Indian Air Force fact files on aircraft
- #13UPSC CSE 2024With reference to radioisotope thermoelectric generators (RTGs), consider the following statements:1. RTGs are miniature fission reactors.2. RTGs are used for powering the onboard systems of spacecrafts.3. RTGs can use Plutonium-238, which is a by-product of weapons development.Which of the statements given above are correct?
- A1 and 2 only
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Answer: (B) 2 and 3 onlyExplanation
Statement 1 is incorrect. An RTG has no chain reaction. It turns the heat from natural radioactive decay into electricity using thermocouples.
Statement 2 is correct. RTGs power deep-space probes where sunlight is weak, for example Voyager and Cassini.
Statement 3 is correct. Plutonium-238 is the usual fuel. It was first made as a by-product of the nuclear weapons programme.
Remember: fission splits atoms; RTGs use decay, which is a different process.Source: NASA RTG fact sheets; US Department of Energy on Plutonium-238
- #14UPSC CSE 2024Consider the following activities:1. Identification of narcotics on passengers at airports or in aircraft2. Monitoring of precipitation3. Tracking the migration of animalsIn how many of the above activities can the radars be used?
- AOnly one
- BOnly two
- CAll three
- DNone
Answer: (B) Only twoExplanation
Radar sends radio waves and studies the echo.
Monitoring of precipitation is correct. Weather radar detects rain and snow.
Tracking animal migration is correct. Radar can follow flocks of birds, bats and insects.
Identifying narcotics on passengers is incorrect. Narcotics are found with trace detectors, sniffer dogs and scanners, not by ordinary radar.
So radar is used in only two of the activities.
Remember: radar stands for Radio Detection and Ranging.Source: Standard physics and meteorology references on radar applications (IMD Doppler weather radar)
- #15UPSC CSE 2024Consider the following aircraft:1. Rafael2. MiG-293. Tejas MK-1How many of the above are considered fifth generation fighter aircraft?
- AOnly one
- BOnly two
- CAll three
- DNone
Answer: (D) NoneExplanation
Fifth generation fighters have stealth shaping, supercruise and advanced sensor fusion. Examples are the American F-22 and F-35.
The Rafale is a 4.5 generation aircraft. The MiG-29 is a fourth generation fighter. The Tejas Mk-1 is also fourth generation, a light fighter.
So none of the three is fifth generation.
Remember: India's own fifth-generation project is the Advanced Medium Combat Aircraft (AMCA).Source: Ministry of Defence / DRDO and ADA material on Tejas and AMCA; standard defence references
- #16UPSC CSE 2023Consider the following pairs:Objects in space - Description1. Cepheids - Giant clouds of dust and gas in space2. Nebulae - Stars which brighten and dim periodically3. Pulsars - Neutron stars that are formed when massive stars run out of fuel and collapseHow many of the above pairs are correctly matched?
- AOnly one
- BOnly two
- CAll three
- DNone
Answer: (A) Only oneExplanation
Pair 1 is incorrect. Cepheids are stars whose brightness varies in a regular cycle.
Pair 2 is incorrect. Nebulae are giant clouds of dust and gas.
Pair 3 is correct. Pulsars are rotating neutron stars left after massive stars collapse.
So only one pair is correct.
Remember: Cepheids are used to measure distances to galaxies.Source: NASA and ISRO astronomy resources; NCERT Class XI Physics
- #17UPSC CSE 2014Which of the following is/are correctly matched?Spacecraft : Purpose1. Cassini-Huygens : Orbiting the Venus and transmitting data to the earth2. Messenger : Mapping and investigating the Mercury3. Voyager 1 and 2 : Exploring the outer solar systemSelect the correct answer using the codes given below.
- A1 only
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Answer: (B) 2 and 3 onlyExplanation
Pair 1 is incorrectly matched. Cassini-Huygens was launched in 1997 to study Saturn and its moons. Huygens landed on Titan.
Pair 2 is correctly matched. NASA's Messenger orbited Mercury from 2011 to 2015 and mapped it.
Pair 3 is correctly matched. Voyager 1 and 2 explored the outer planets and now travel in interstellar space.
Remember: Venus was studied by Magellan and Venus Express.Source: NASA mission pages for Cassini-Huygens, Messenger and Voyager
- #18UPSC CSE 2007Which one of the following pairs is not correctly matched?
- ACosmic Background Explorer (COBE): Satellite programme
- BFalcon: Under-sea cable system
- CDiscovery: Space shuttle
- DAtlantis: Space station
Answer: (D) Atlantis: Space stationExplanation
Atlantis was a Space Shuttle orbiter of NASA, not a space station. So this pair is wrong.
COBE was a NASA satellite that studied cosmic background radiation. Falcon was an undersea cable system. Discovery was a Space Shuttle orbiter.
Remember: Shuttle orbiters were Columbia, Challenger, Discovery, Atlantis and Endeavour.Source: NASA Space Shuttle programme records
- #19RAS/RTS 2016Match List-I with List-II and select the correct answer using the codes given below the lists:List-I (Launch Vehicle)1. Satellite Launch Vehicle-3 (SLV-3)2. Augmented Satellite Launch Vehicle (ASLV)3. Polar Satellite Launch Vehicle (PSLV)4. Geosynchronous Satellite Launch Vehicle (GSLV)List-II (Satellite)A. Chandrayaan-IB. RohiniC. SROSS-CD. EDUSATCode:1 2 3 4
- AA B C D
- BB C D A
- CB C A D
- DC A B D
Answer: (C) B C A DExplanation
SLV-3 launched the Rohini satellite in 1980.
ASLV launched the SROSS series of satellites, including SROSS-C.
PSLV launched Chandrayaan-1 in 2008.
GSLV launched EDUSAT, the education satellite, in 2004.
So the correct matching is 1-B, 2-C, 3-A, 4-D.
Remember: PSLV is the launcher of Chandrayaan-1 and the Mars Orbiter Mission.Source: ISRO, launch vehicle and mission records
- #20UPPCS 2003Consider the following statements:Assertion (A): A space shuttle loses radio contact with ground station for a while during landing on the earth.Reason (R): As a space shuttle enters earth's atmosphere, the shuttle's surface temperature increases which ionize the surrounding air.In the context of the above statements, which of the following is correct?
- ABoth (A) and (R) are true, and (R) is the correct explanation of (A).
- BBoth (A) and (R) are true, but (R) is not the correct explanation of (A).
- C(A) is true, but (R) is false.
- D(A) is false, but (R) is true.
Answer: (A) Both (A) and (R) are true, and (R) is the correct explanation of (A).Explanation
Assertion (A) is true. A shuttle loses radio contact for a few minutes during re-entry. This is called the communication blackout.
Reason (R) is true. The shuttle hits the atmosphere at very high speed. Air in front of it is compressed and heated strongly.
The hot air ionises, that is, its atoms split into ions and free electrons. This layer of ionised gas is called plasma.
Plasma absorbs and reflects radio waves. So signals cannot pass between the shuttle and the ground station.
Hence R explains A.
Remember: Re-entry blackout is caused by a plasma sheath around the vehicle.Source: NCERT Class XI Physics (ionisation); NASA material on re-entry communication blackout
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