Defence Technology and Missiles

• Statement 1 is correct. Agni-IV is a surface-to-surface ballistic missile, launched from a road-mobile transporter erector launcher.
• Statement 2 is incorrect. Agni-IV is a two-stage missile using solid propellant in both stages. Only the earliest Indian systems used liquid propellant, the Prithvi series and the first stage of Agni-I in its original configuration, and the whole direction of the Agni programme has been towards all-solid motors precisely because solid propellant permits the missile to be stored fuelled, moved on a launcher and fired at short notice, whereas a liquid-fuelled missile must be fuelled before launch and is therefore vulnerable and slow to react.
• Statement 3 is incorrect. Agni-IV has a range of the order of three thousand five hundred to four thousand kilometres with a payload of about one tonne. A figure of seven thousand five hundred kilometres exceeds even Agni-V, which is in the five thousand kilometre class, and would place the missile in the full intercontinental category, which India had not demonstrated. The official answer is therefore (a).
• Statement 2 is the decisive one and settles the item on a single principle rather than on a recalled number: the strategic logic of a survivable land-based deterrent requires solid propellant, and a candidate who holds that principle rejects statement 2 without hesitation, which removes (b) and (d), and statement 1 is beyond argument, which removes nothing but confirms (a) once statement 3 is rejected on range.

INS Astradharini, commissioned in October 2015, is a torpedo launch and recovery vessel, indigenously designed and built to support the trials of underwater weapons and sonar systems developed by the Naval Science and Technological Laboratory at Visakhapatnam. She replaced the older Astravahini and is notable for a catamaran hull form that gives stability during launch and recovery operations. Hence (c).

• Option (a) is wrong: amphibious warfare ships of the Indian Navy are the landing platform dock and landing ship tank classes, of which INS Jalashwa is the best known.
• Option (b) is wrong: India's nuclear-powered submarines are the Arihant class and the leased Chakra, and a trials support vessel is not a submarine at all.
• Option (d) is wrong for a further reason worth stating plainly, that India has never operated a nuclear-powered aircraft carrier; Vikramaditya and the later Vikrant are conventionally powered. The name itself supplies a partial route, astra denoting a weapon and dharini a bearer or holder, which points to a weapon-carrying auxiliary rather than a combatant.

• Option (c) is correct. Terminal High Altitude Area Defense is an American ballistic missile defence system, developed by Lockheed Martin and operated by the United States Army, designed to intercept short, medium and intermediate range ballistic missiles in their terminal phase at high altitude. It uses a hit to kill kinetic interceptor with no explosive warhead, destroying the target by the energy of impact, and is cued by the AN slash TPY 2 X band radar. Its deployment in the Republic of Korea from 2017 provoked sustained Chinese objection, ostensibly to the reach of the radar rather than to the interceptor.
• Option (a) is wrong: Israel's systems are Iron Dome for rockets and short range projectiles, David's Sling for medium range, and Arrow for longer range ballistic threats, and the radar in the Israeli architecture is the Green Pine rather than anything called THAAD.
• Option (b) is wrong: India's indigenous effort is the Ballistic Missile Defence programme of the Defence Research and Development Organisation, with the Prithvi Air Defence and Prithvi Defence Vehicle for exo atmospheric and the Advanced Air Defence for endo atmospheric interception.
• Option (d) is wrong: Japan and the Republic of Korea have no such joint programme, and Japan's own layered defence rests on Aegis equipped destroyers with SM 3 interceptors and on land based Patriot PAC 3. Note that the name states the function, terminal phase, high altitude, area rather than point defence, which is enough to identify it as an interceptor system rather than a radar and to eliminate option (a).

Hence (c).

A fractional orbital bombardment system delivers a warhead by first placing it in a low orbit and then braking it out of that orbit over the target, instead of flying the high ballistic arc of a conventional intercontinental missile. The military attraction is that the trajectory is low and can approach from any direction, including over the South Pole, which defeats early warning radars oriented along expected ballistic corridors and compresses warning time.

• Option (c) captures this and is correct.
• Option (a) describes planetary defence against an asteroid, an entirely civilian application with no bombardment of a terrestrial target.
• Option (b) describes an orbiter and lander sequence of the kind used in interplanetary missions.
• Option (d) describes a comet rendezvous and lander, the profile flown by Rosetta and Philae.

Hence (c).

Both statements are reversed, which makes this a straightforward elimination once the basic distinction is held.

• Statement 1 is incorrect. A ballistic missile is rocket powered only during the boost phase and thereafter follows a free ballistic trajectory through mid course and re entry, reaching hypersonic speeds. A cruise missile is air breathing and jet propelled through most of its flight, sustaining powered aerodynamic flight at low altitude, and many are subsonic.
• Statement 2 is likewise reversed. Agni-V is a solid fuelled long range ballistic missile in the intercontinental class, while BrahMos is a supersonic cruise missile with a ramjet sustainer. Neither statement stands, giving (d).

All three are high explosives used in military munitions, giving (b). They belong to the class of nitrogen-rich energetic materials, and the family also includes the more familiar RDX and TNT. The distinctions among them concern the balance between energy release and stability: some members of the class are valued for high detonation performance, while others are developed as insensitive munitions, meaning they resist accidental initiation by shock, fire or fragment impact during storage and handling, which is a major safety consideration for naval and aircraft magazines.

• Option (a) is wrong because refrigerant replacements for hydrofluorocarbons are hydrofluoroolefins, ammonia, carbon dioxide and hydrocarbons, an entirely unrelated chemistry driven by the Kigali Amendment.
• Option (c) is wrong because cruise missile propulsion uses conventional liquid hydrocarbon fuel in a turbojet or turbofan, and these compounds would sit in the warhead rather than the fuel tank.
• Option (d) is wrong for a related reason: solid rocket propellants are formulated from an oxidiser such as ammonium perchlorate with a metallic fuel and a polymeric binder, and although some energetic materials appear as propellant additives, that is not the defining characteristic of this group.

• Statement 1 is correct and states the two pillars of the technology. Shaping deflects incident energy away from the transmitter so that little returns to the receiver, which reduces the radar cross section, and radar absorbing material converts a further part of the incident energy into heat within a lossy ferrite or carbon loaded coating.
• Statement 2 is correct and follows from the physics of the first. Shaping and absorbing coatings are optimised for the centimetric wavelengths of fire control radars, so when the wavelength becomes comparable to major structural features of the airframe, as with metre wave VHF and UHF radars, the scattering regime changes and returns rise sharply, which is why low frequency surveillance radars are the standard counter stealth measure.
• Statement 3 is incorrect and is the eliminator, since the objective is always to reduce the energy returned to the receiver, and a coating designed to increase scattering would defeat the entire purpose. Metamaterials are studied in this field precisely for the opposite reason, to guide waves around a body or absorb them over a wide band.

Hence 1 and 2 and (c) is correct, while (b) and (d) accept a statement whose verb points the wrong way.

The official key treats all three statements as correct, giving (a).

• Statement 1 is sound, since the mission as announced is an integrated shield combining air defence, ballistic missile defence and an offensive counter strike element rather than a purely defensive layer, which is what distinguishes it from an air defence programme alone.
• Statement 2 is sound and is essentially the stated rationale, that indigenous capability across detection, interception and response reduces dependence on external suppliers and therefore reinforces strategic autonomy.
• Statement 3 reflects the announced horizon of 2035 and the intention to extend protection beyond purely military assets to civilian and religious sites and centres of population. There is no option offering 1 and 2 while excluding 3 in a way that would be preferable, since (b) would require statement 3 to be false in substance and not merely loose in wording.

• Item 1 is correct, since the Su-30 MKI is built under licence by Hindustan Aeronautics Limited at Nashik from Russian design with progressively increasing indigenous content, and further batches have been ordered from the same line.
• Item 2 is correct, since the T-90 series is produced under licence at the Heavy Vehicles Factory at Avadi, and the T-90 Mk-III variant with an improved engine, thermal imaging and an automatic target tracker was sanctioned for manufacture there.
• Item 3 is incorrect and is the eliminator, since Akula class nuclear powered attack submarines are Russian built and have been operated by India only on lease, the INS Chakra arrangements being the examples, whereas India's own nuclear submarine construction is the indigenous Arihant class of ballistic missile submarines at Visakhapatnam. Hence 1 and 2 and (a) is correct. (b) admits the Akula, (c) drops the Avadi tank line, and (d) drops the Nashik aircraft line.

• Statements 1 and 2 are correct and statement 3 is the eliminator, so (c) is the answer.
• Statement 2 is the substantive point and can be reasoned rather than recalled, since the purpose of a national standard is precisely to fix common test methods and performance thresholds so that equipment bought by different agencies, the police, the paramilitary forces and the armed forces, meets a comparable specification and can be used and serviced across them.
• Statement 1 records the designation of that standard.
• Statement 3 fails on the attribution, since a national standard issued by the Bureau of Indian Standards is developed through its own sectional committees drawing on domestic technical expertise, in this case the Terminal Ballistics Research Laboratory of the Defence Research and Development Organisation at Chandigarh, and the addition of a named foreign research institute is the inserted error. A standard intended to secure indigenous procurement autonomy would not be co-developed with a foreign defence research body. (a) and (b) accept that attribution and (d) discards the interoperability rationale.