Engine...TDR and high-performance directed rocket motor
Warhead...nuclear warhead (variable yield)
The Avalanche is an active radar guided unconventional medium air to air missile (UMRAAM) developed by the UNETCO International Armaments Consortium. Like with the Stingray, the missile is assembled off-site before transport to a central facility where it is then inspected and mated to a nuclear warhead. Prior to its destruction during an alien raid, this was the Morlenbach facility in Germany. Since that event, inspections are now carried out in a secret facility in Western Europe (known among troops as the "Uranium Hotel"). The missiles then undergo another round of safety checks and inspections before being requisitioned to X-COM bases. Meticulous records are kept of every warhead entered into UNETCO service, what missiles they are mated to, where they are shipped, and where and when they are used.
Structurally, the Avalanche is similar to the Stingray. It uses a Throttleable Ducted Rocket (TDR) (a ramjet) with an integrated nozzleless booster to achieve a high speed on approach to the target. It is larger and far less maneuverable than the Stingray, however, doing damage to the target by virtue of the proximity triggered detonation of its nuclear warhead. It possesses a similar electronics package to the Stingray. One notable difference is that the Avalanche's warhead needs to be activated before it is mounted to a hard point, and then electronically unlocked before firing (after mounting). The levels of redundancy involved have ensured that, after many years using these weapons, there has never been an accident.
The warhead used is similar to the American W80. It is a small thermonuclear warhead (or hydrogen bomb) with a variable explosive yield between 5 and 150 kT TNT. The proximity fuse can also be adjusted to trigger detonation at different distances from the target. The Avalanche is capable of intercepting and damaging even the largest UFOs, however, because only a few of these missiles can be carried at a time (due to size), they may not be able to successfully down the more powerful alien craft: Terror Ships, Battleships, and occasionally Supply Ships can survive several salvos of these weapons. However, it is a powerful addition to the X-COM arsenal, and it was essential in the early years before the development of ship mounted plasma beams and fusion ball launchers. Most Avalanche missiles were retired in 2003.
When an Avalanche is launched, X-COM pilots use the brevity code "Genie" in radio communication, to announce the launch of a guided air-to-air nuclear missile.