UPSC CSE Prelims
Defence Technology Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Defence Technology
Topic Breakdown: Scroll →
Consider the following statements about Mission Sudarshan Chakra of India:
- It aims to enhance India's air defence, ballistic missile defence and aerial offensive capabilities.
- This Mission is being designed to enhance rapid, precise, and powerful defence responses, reinforcing India's strategic autonomy.
- 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?
Detailed Explanation:
All three statements are correct. Mission Sudarshan Chakra is a proposed integrated security initiative aimed at strengthening India's air defence, ballistic missile defence, and offensive capabilities.
It incorporates advanced technologies to enable rapid and precise responses while promoting strategic autonomy. The mission also envisions extending a nationwide security shield to public places across India by 2035.
Therefore, Option A (1, 2 and 3) is correct.
Mission Sudarshan Chakra is a long-term defence modernization initiative focused on creating a layered security architecture using indigenous technologies. It integrates air defence systems, missile defence, AI-enabled surveillance, space-based monitoring, and advanced weapons to enhance national security.
Which of the following items of defence hardware is/are manufactured in India ?
- Su-30 MKI Fighter Jets
- T-90 MK-III Tanks
- Akula Class Submarine
Select the answer using the code given below :
Detailed Explanation:
Statements 1 and 2 are correct. Su-30 MKI fighter jets are manufactured in India by HAL under a technology-transfer agreement, while T-90 Mk-III (Bhishma) tanks are produced in India at the Heavy Vehicles Factory, Avadi.
Statement 3 is incorrect because Akula-class submarines are designed and built in Russia. India has only leased these submarines and does not manufacture them.
Therefore, Option A (1 and 2) is correct.
India follows a policy of defence indigenisation, promoting domestic production of military equipment through technology transfer, licensed manufacturing, and indigenous development. This supports self-reliance under the Atmanirbhar Bharat initiative in the defence sector.
Which of the following statements with regard to drone swarms is/are correct ?
- They use Terahertz band of frequency to communicate with the command centre.
- Individual drones in the swarm can communicate with other drones in the swarm.
- GPS Spoofing is a commonly used technique to counter drone swarm attack.
Select the answer using the code given below :
Detailed Explanation:
Statement 1 is incorrect because drone swarms generally use conventional radio frequency (RF) bands for communication with command centres, not the Terahertz (THz) band.
Statements 2 and 3 are correct. Drones within a swarm communicate with each other to coordinate actions, and GPS spoofing is a widely used countermeasure to mislead and disrupt drone swarm navigation.
Therefore, Option B (2 and 3 only) is correct.
A drone swarm is a group of drones that work together using autonomous coordination and inter-drone communication. Swarm technology is used in surveillance, military operations, disaster management, and mapping. Countermeasures include jamming, GPS spoofing, and directed-energy systems.
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Which of the following statements with regard to stealth technology is/are correct ?
- Stealth objects have a very small radar cross-section and are coated with Radar Absorbing Material.
- Stealth objects can be detected using specific frequencies.
- Stealth objects are coated with metamaterials to increase the scattering of electromagnetic radiation.
Select the answer using the code given below :
Detailed Explanation:
Statement 1 — Correct. The primary goal of stealth technology is to minimize an object's Radar Cross-Section (RCS). This is achieved through:
- Geometric shaping — to deflect radar waves away from the source
- Radar Absorbing Materials (RAM) — which absorb electromagnetic radar energy and dissipate it as heat
Statement 2 — Correct. Stealth objects are not completely invisible. RAM coatings are optimized to defeat high-frequency radars (X-band). However, low-frequency radars (VHF/UHF bands) can detect stealth objects as their longer wavelengths resonate with the aircraft's physical dimensions — though they lack resolution required for a missile lock.
Statement 3 — Incorrect. Metamaterials in stealth applications are used to decrease/eliminate radar scattering — NOT increase it. They work by:
- Perfectly absorbing electromagnetic radiation, OR
- Bending and redirecting waves around the object (electromagnetic cloaking)
Increasing scattering would make the object more visible — defeating the very purpose of stealth.
Key Trick: Statement 3 reverses the function of metamaterials — a classic UPSC trap of replacing a correct word with its opposite.
The 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 ?
- The new standard is known as IS 19445 : 2025.
- It will improve interoperability of equipment across agencies.
- It was developed by TBRL, DRDO in collaboration with the 30th Central Scientific Research Institute, Russia.
Select the answer using the code given below :
Detailed Explanation:
Statement 1 — Correct. In December 2025, BIS notified India's first dedicated national standard for bomb disposal systems, officially designated as IS 19445:2025.
Statement 2 — Correct. The standard establishes comprehensive guidelines for evaluating bomb disposal equipment — including bomb blankets, baskets, and inhibitors — against blast loads and splinter effects. A key objective is to bring uniformity in testing and procurement, thereby improving safety, reliability, and interoperability across agencies such as Armed Forces, CAPFs, NSG, and State Police.
Statement 3 — Incorrect. The standard was developed indigenously by BIS at the request of the Ministry of Home Affairs (MHA) and DRDO's Terminal Ballistic Research Laboratory (TBRL). There is no collaboration with any Russian entity. In fact, the standard was specifically created to reduce reliance on foreign norms, as existing international standards were either restricted in access or misaligned with Indian operational realities.
Key Point: IS 19445:2025 is a landmark step in indigenisation of defence standards — developed entirely within India by BIS + DRDO/TBRL, not in collaboration with any foreign agency.
With reference to India's defence, consider the following pairs:
Aircraft type – Description
I. Dornier-228 : Maritime patrol aircraft
II. IL-76 : Supersonic combat aircraft
III. C-17 Globemaster III: Military transport aircraft
How many of the pairs given above are correctly matched?
Detailed Explanation:
Among the three pairs, Dornier-228 and C-17 Globemaster III are correctly matched with their roles, while IL-76 is incorrectly described.
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Pair I is Correct: Dornier-228 is used for maritime patrol, surveillance, and reconnaissance missions.
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Pair II is Incorrect: IL-76 is a heavy military transport aircraft, not a supersonic combat aircraft.
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Pair III is Correct: C-17 Globemaster III is a strategic military transport aircraft used for troop and cargo movement.
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Therefore, only two pairs are correctly matched, making Option B the correct answer.
Pair-wise Analysis
| Pair | Status | Explanation |
|---|---|---|
| I. Dornier-228 : Maritime patrol aircraft | ✅ Correct | Operated by the Indian Navy and Coast Guard for maritime surveillance and patrol. |
| II. IL-76 : Supersonic combat aircraft | ❌ Incorrect | IL-76 is a heavy-lift transport aircraft, not a combat aircraft. |
| III. C-17 Globemaster III : Military transport aircraft | ✅ Correct | Used by the Indian Air Force for strategic airlift operations. |
Important Transport Aircraft of India
Dornier-228
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Twin-engine utility aircraft.
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Used for maritime patrol, surveillance, search and rescue.
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Operated by the Indian Navy and Coast Guard.
IL-76
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Heavy strategic transport aircraft of Russian origin.
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Used for troop transport, cargo movement, and humanitarian missions.
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Also serves as a platform for AWACS variants.
C-17 Globemaster III
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Strategic military transport aircraft manufactured by Boeing.
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Can carry troops, tanks, helicopters, and heavy equipment.
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Backbone of India's long-range airlift capability.
With 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?
Detailed Explanation:
The capabilities of Unmanned Aerial Vehicles (UAVs) depend on their design (fixed-wing, multirotor, hybrid, etc.). Therefore, the word "All" makes all three statements incorrect.
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Statement I is Incorrect: Not all UAVs can perform vertical landing. Fixed-wing UAVs require a runway or launcher/recovery system.
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Statement II is Incorrect: Not all UAVs can hover. Fixed-wing UAVs must keep moving forward to stay airborne.
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Statement III is Incorrect: Not all UAVs use battery power only. Many UAVs use fuel engines, hybrid systems, or even solar power.
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Therefore, none of the statements are correct, making Option D the correct answer.
Statement-wise Analysis
| Statement | Status | Explanation |
|---|---|---|
| I. All UAVs can do vertical landing | ❌ Incorrect | Only VTOL and multirotor UAVs can land vertically. |
| II. All UAVs can do automated hovering | ❌ Incorrect | Fixed-wing UAVs cannot hover. |
| III. All UAVs use battery only | ❌ Incorrect | UAVs may use fuel, hybrid, solar, or battery power. |
Types of UAVs
| Type | Hovering | Vertical Take-off/Landing | Power Source |
|---|---|---|---|
| Fixed-Wing | ❌ No | ❌ No | Fuel, Battery, Hybrid |
| Multirotor | ✅ Yes | ✅ Yes | Mostly Battery |
| VTOL Hybrid | ✅ Yes | ✅ Yes | Battery, Fuel, Hybrid |
Important Facts
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Fixed-wing UAVs are preferred for long-range surveillance and mapping.
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Multirotor drones are ideal for photography, monitoring, and inspection.
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Hybrid UAVs combine the advantages of fixed-wing and multirotor systems.
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Modern UAVs can be powered by batteries, internal combustion engines, hydrogen fuel cells, or solar energy.
What is the common characteristic of the chemical substances generally known as CL-20, HMX and LLM-105, which are sometimes talked about in media?
Detailed Explanation:
CL-20, HMX, and LLM-105 are advanced high-energy explosive compounds used in military applications.
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CL-20 is one of the most powerful non-nuclear explosives developed.
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HMX is widely used in missiles, warheads, and other military munitions.
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LLM-105 is a modern explosive known for its high performance and improved thermal stability.
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Therefore, all three are explosives used in military weapons, making Option B the correct answer.
Why Other Options Are Wrong
| Option | Why Incorrect? |
|---|---|
| Alternatives to hydro-fluorocarbon refrigerants | These chemicals are not refrigerants. |
| Explosives in military weapons | Correct. ✅ |
| High-energy fuels for cruise missiles | They are explosives, not fuels. |
| Fuels for rocket propulsion | Rocket fuels and explosives are different categories of energetic materials. |
Consider the following activities:
- Identification of narcotics on passengers at airports or in aircraft
- Monitoring of precipitation
- Tracking the migration of animals
In how many of the above activities can the radars be used?
Detailed Explanation:
Correct Answer: ✅ Only Two (Option B)
Radar works by transmitting radio waves and detecting their reflected signals from objects. It is widely used in weather monitoring and wildlife tracking, but not for identifying narcotics on passengers.
❌ Statement I is Incorrect: Narcotics detection at airports is generally done using X-ray scanners, trace detectors, sniffer dogs, and chemical analysis, not radar.
✅ Statement II is Correct: Weather radars are extensively used to monitor precipitation such as rain, snow, and storms.
✅ Statement III is Correct: Radar technology is used to track the migration of birds, bats, and other animals for ecological studies.
Short Notes: Radar Applications
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RADAR stands for Radio Detection And Ranging.
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It uses radio waves to detect the location, speed, and direction of objects.
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Weather radars monitor rainfall, thunderstorms, and cyclones.
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Doppler Radar can measure the velocity of moving objects.
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Radar is widely used in aviation, defense, navigation, and meteorology.
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It helps track bird and animal migration over long distances.
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Radar works effectively in darkness, fog, and cloudy conditions.
Consider the following aircraft:
- Rafale
- MiG-29
- Tejas MK-1
How many of the above are considered fifth generation fighter aircraft?
Detailed Explanation:
Correct Answer: ✅ Option 4 (None)
Fifth-generation fighter aircraft are characterized by stealth technology, sensor fusion, supercruise capability, advanced avionics, and network-centric warfare systems. None of the aircraft listed belong to the fifth-generation category.
❌ Rafale – Incorrect: The Dassault Rafale is a 4.5-generation multirole fighter aircraft developed by France.
❌ MiG-29 – Incorrect: The Mikoyan MiG-29 is a fourth-generation fighter aircraft.
❌ Tejas MK-1 – Incorrect: The HAL Tejas Mk1 is generally classified as a fourth-generation light combat aircraft with some modern upgrades.
Therefore, none of the above are fifth-generation fighter aircraft.
Short Notes: Fighter Aircraft Generations
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4th Generation: High maneuverability, fly-by-wire systems, pulse-Doppler radar (e.g., MiG-29).
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4.5 Generation: Advanced avionics, AESA radar, limited stealth features (e.g., Rafale).
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5th Generation: Full stealth, sensor fusion, supercruise, network-centric warfare.
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Examples of 5th-generation fighters: F-22 Raptor, F-35 Lightning II, Sukhoi Su-57.
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India currently operates Rafale, Su-30MKI, MiG-29, and Tejas, but none are fifth-generation fighters.
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India is developing the Advanced Medium Combat Aircraft (AMCA).
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Stealth technology reduces radar detection.
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Sensor fusion combines data from multiple sensors into a single operational picture.
Consider the following statements:
- Ballistic missiles are jet-propelled at subsonic speeds throughout their flights, while cruise missiles are rocket-powered only in the initial phase of flight.
- Agni-V is a medium-range supersonic cruise missile, while BrahMos is a solid-fuelled intercontinental ballistic missile.
Which of the statements given above is/are correct?
Detailed Explanation:
Answer: Option 4 — Neither 1 nor 2
Both statements incorrectly describe the fundamental characteristics of ballistic and cruise missiles, as well as the specific types of Agni-V and BrahMos missiles. Let us evaluate each statement:
❌ Statement 1 – Incorrect: The statement incorrectly swaps the propulsion characteristics. Ballistic missiles are rocket-powered and follow a high, arcing ballistic trajectory at supersonic or hypersonic speeds, while cruise missiles are jet-propelled, fly at lower altitudes using aerodynamic lift, and can be subsonic, supersonic, or hypersonic.
❌ Statement 2 – Incorrect: The statement incorrectly describes both missiles. Agni-V is a solid-fuelled Intercontinental Ballistic Missile (ICBM) with a range exceeding 5,000 km, capable of striking targets across continents. BrahMos is a supersonic cruise missile (not a ballistic missile) developed jointly by India and Russia, with a range of around 450-600 km.
📝 Short Notes: Ballistic vs Cruise Missiles
| Feature | Ballistic Missiles | Cruise Missiles |
|---|---|---|
| Propulsion | Rocket-powered (initial boost phase) | Jet-propelled (air-breathing engines) throughout flight |
| Trajectory | High, arcing ballistic path; exits and re-enters atmosphere | Low-altitude, follows terrain contours using aerodynamic lift |
| Speed | Supersonic to hypersonic | Subsonic, supersonic, or hypersonic |
| Guidance | Guided only during boost phase; free-fall descent | Continuously guided throughout flight |
| Range Categories | Short (< 1,000 km), Medium (1,000-3,000 km), Intermediate (3,000-5,500 km), Intercontinental (> 5,500 km) | Tactical (< 300 km), Medium (300-1,000 km), Long-range (> 1,000 km) |
| Indian Examples | Agni series (I, II, III, IV, V), Prithvi series | BrahMos, Nirbhay |
- Agni-V: India's longest-range ICBM with a strike range of over 5,000 km, three-stage solid-fuelled missile, capable of carrying nuclear warheads, enhances India's strategic deterrence.
- BrahMos: World's fastest supersonic cruise missile (Mach 2.8-3), joint venture between India (DRDO) and Russia (NPO Mashinostroyeniya), available in land, sea, air, and submarine-launched variants.
- Detection Difficulty: Cruise missiles fly low and are harder to detect by radar, while ballistic missiles have predictable trajectories once launched but are harder to intercept due to high speeds.
What is "Terminal High Altitude Area Defense (THAAD)", sometimes seen in the news?
Detailed Explanation:
The correct answer is An American anti-missile system (Option 3). THAAD (Terminal High Altitude Area Defense) is a missile defense system developed by the United States to intercept and destroy short, medium, and intermediate-range ballistic missiles during their final phase of flight.
THAAD is designed to intercept ballistic missiles both inside and outside the Earth's atmosphere. It is an important part of the U.S. missile defense network and has been deployed in countries such as South Korea and Saudi Arabia.
Which one of the following is the best description of ‘INS Astradharini’, that was in the news recently?
Detailed Explanation:
Answer: Option 3 — Torpedo launch and recovery vessel
INS Astradharini is India's first indigenously designed and built Torpedo Launch and Recovery Vessel (TLRV), commissioned in 2015 with 95% indigenous content.
It serves as a specialized platform for technical trials of underwater weapons like torpedoes and mines developed by NSTL, featuring a catamaran hull design for enhanced stability during weapon recovery operations.
With reference to Agni-IV Missile, which of the following statements is/are correct?
- It is a surface-to-surface missile.
- It is fuelled by liquid propellant only.
- It can deliver one-tonne nuclear warheads about 7500 km away.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Agni-IV is a surface-to-surface ballistic missile designed to be launched from mobile land-based platforms and strike ground targets.
❌ Statement 2 – Incorrect: Agni-IV uses two-stage solid-fuel propulsion, not liquid propellant. Solid propellants provide better storage stability and quick launch capability.
❌ Statement 3 – Incorrect: Agni-IV has a range of approximately 4,000 km, not 7,500 km. While it can carry a one-tonne payload, the 7,500 km range figure is incorrect.