This idea came from a weapons anecdote and a tale of 3M's post-it notes. The weapons anecdote is that the AM39 Exocet missile tends to be more destructive when the warhead duds, than when it detonates, as a detonation would hurl any unconsumed fuel in the missile out of the stricken ship and nothing starts fires like burning rocket fuel. The post-it notes are made with a failed glue that never stuck very well, but doesn't stain and takes forever to dry (ones I have forgotten in old textbooks can be restuck after being on the same page for over ten years).
In 2960, Magna developed a new gelled fuel for long range missiles. Confident in the chemists' experimental results, and in a hurry to market it, the normal pilot plant stage was skipped. The first run was from a full scale industrial plant tailored for the new fuel. The first batch was a shocking failure. While the new fuel did burn well enough to fly straight, there was a stutter that would shake the missile enough to damage the fuse, and the fuel was too sensitive to heat, causing the engines to cook off before the warheads might, in an overheating mech. Desperate to salvage their investment, Magna used it to fuel practice rounds and marketed them towards vehicle units. Sales started at a respectable, if modest pace, but were hampered by the number of fires caused by unconsumed fuel sticking to the target and burning fiercely, so the LRM-p would have hardly made even a footnote in history, if not for a fortuitous accident.
In 3005 lance of raiding pirates had to gross misfortune to blunder across a lance of LRM carriers just as they were about to start a firing exercise. The lance of combat vehicles was hidden buy trees. The instructor, knowing the vehicles were loaded with practice rounds and that moving would draw attention (and destruction) told everybody to not move and do nothing. One cadet broke, stabbed the firing button, while screaming 'Fire!' into his comlink, so the other three vehicles opened fire. As the pirates were just abreast of the vehicles and just inside short range, the rockets still had most of their fuel. Being low maintenance mechs armed with large bore autocannon, the pirate mechs did not have the heat sinks to deal the liberal coating of burning rocket fuel. One pirate lost his head and charged the LRM carriers and knocked one out, but between the heat load of firing its weapons and another barrage of LRM-p's, one of its ammo bins cooked off. The other three made a break for it. Two pilots ejected rather than be cooked in their mechs and the third was fast enough, despite the heat loading to pull far enough away from the LRM carriers to escape the ravages of unburnt fuel.
After this incident, the gel fuelled LRM-p enjoyed strong enough sales to warrant more production runs.
The LRM-p round gets a +1 to hit mod for being unguided, but has no minimum range. At short range, each missile dumps 2 heat on the target, at medium range, each missile dumps a single point of heat, and at long range, the blue painted nosecone transfers some of its paint to the target, so that a hit can be confirmed (it is a practice round). They are no less dangerous to have in the bins than inferno rounds. An emergent property of the LRM-p is that, carrying its own oxydizer, it still works in a vacuum, or exotic atmosphere that would not suport a fire, just not at aerospace ranges.
