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?

(a) These are alternatives to hydrofluorocarbon refrigerants
(b) These are explosives in military weapons ✓ UPSC's answer
(c) These are high-energy fuels for cruise missiles
(d) These are fuels for rocket propulsion

Why the answer is (b)

• CL-20 (hexanitrohexaazaisowurtzitane), HMX (octogen) and LLM-105 are nitramine and nitro-heterocyclic compounds classed as high-energy explosives.

• They are used as the main charge or booster in military munitions — warheads, shaped charges and shells — because they release more energy and detonate faster than TDX-era explosives like TNT.

• CL-20 is among the most powerful non-nuclear explosives known; LLM-105 is valued as an insensitive explosive that resists accidental detonation.

• They are not refrigerants, and although some are also used in solid propellants, their defining characteristic and the reason they appear in the news is as explosives — option (b).

• India's DRDO and Premier Explosives have reported work on CL-20-based formulations.

Why the other options are wrong

(a) These are alternatives to hydrofluorocarbon refrigerants: These compounds are energetic materials, not refrigerants.
(c) These are high-energy fuels for cruise missiles: They are explosives, not fuels; cruise missiles use jet fuel.
(d) These are fuels for rocket propulsion: Rocket fuels are propellants such as ammonium perchlorate composites; these are explosives.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2025, held on 25 May 2025. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.