Henschel Hs 117 'Schmetterling'

The Henschel Hs 117 'Schmetterling' (Butterfly) was a ground-to-air guided missile that almost entered service in the last days of the Third Reich.

Henschel first suggested building a ground-to-air missile in 1941, with the designation Hs 297. At first the RLM (German Air Ministry) wasn't interested in the design, but in 1943, after it became clear that the war was going against Germany, Henschel were ordered to produce the missile as a matter of urgency, with the new designation of Hs 117.

The Hs 117 was an odd looking piece of equipment. It had an asymmetrical nose, which had a pointed cone on the right and a propeller on the left, used to power a small generator. Two booster rockets were carried for take-off, mounted above and below the fuselage. A third rocket was built into the missile. The swept back wings were more conventional, and somewhat resemble those of more recent cruise missiles. The rocket was steered using solenoid-controlled Wagner bars on the trailing edge of the wings and the tail plane.

Launch power was provided by two Schmidding 109-553 solid fuel rockets, each of which provided 3,850lb of thrust for four seconds, bring the rocket up to 680mph. The internal rocket was normally a BMW 109-558, which used R-Stoff (which self ignited) as its main fuel and SV-Stoff to oxidize the R-Stoff. It was also possible to use the Walter 109-729 rocket, which used low-octane petrol (Br-Stoff), SV-Stoff and an alcohol igniter.

The missile was controlled using the Kehl/ Strassburg system, which had the code name 'Tarsival' and the designation FuG203/230. This used four radio frequencies, two for the vertical controls and two for the horizontal. The whole system was joystick controlled. A fifth frequency was used to detonate the warhead.

The Hs 117 was not a precision instrument. It was not expected to score direct hits on enemy aircraft, and instead relied on blast to damage or destroy its targets. It was launched from a modified anti-aircraft gun mount, which was aimed in the general direction of the target. Once the missile was in the air a flair (by day) or light (by night) would be ignited in the tail, to allow the controller to follow its path. The controller would use a normal optical telescope to follow the rocket, and use the joystick to bring it into the middle of a group of enemy aircraft, where it would be detonated. Some work was done on a radar based control system, which used two cathode ray tubes - one for the target and one for the missile. The controller used the joystick to keep the dots together.

The first test launch of the Hs 117 was made in May 1944, and by September twenty two launches had been made, including some with the Hs 117H (see below). The missile could reach 36,000ft, and had a range of up to ten miles. In December the Hs 117 was ordered into production, but the first deliveries were not expected until March 1945, and full production was not expected until November. It was hoped that the first operational unit would enter service in March, but the war ended before the Hs 117 began operations.

The Hs 117H was an air-to-air missile based on the standard Schmetterling. It didn't need the external booster rockets, and carried a larger 220lb warhead. The guidance system was the same as for the ground-launched version, although the controller would be in a nearby parent aircraft. The Hs 117H could be launched from a range of up to 6.2 miles, and could reach targets 16,500ft above the parent aircraft. Work on the Hs 117H continued into 1945, and the project was one of few to survive a savage cut in January 1945, but it was never used operationally.

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How to cite this article: Rickard, J (9 December 2009), Henschel Hs 117 'Schmetterling', http://www.historyofwar.org/articles/weapons_henschel_hs_117.html

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