GM-1
Encyclopedia
GM-1 colloquially known as Haha-Gerät (Ha-Ha Device) was a system for injecting nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

 (laughing gas) into aircraft engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...

s that was used by the Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....

in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. This increased the amount of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 in the fuel mixture, and thereby improve high-altitude performance. GM-1 was used on a number of modifications of existing fighter designs in order to counter the increasing performance of Allied fighters at higher altitudes.

A different system for low-altitude boost known as MW 50
MW 50
MW 50 was a 50-50 mixture of methanol and water that was often sprayed into the supercharger of World War II aircraft engines primarily for its anti-detonant effect, allowing the use of increased boost pressures.Secondary effects were cooling of the engine and charge cooling...

 was also used, although GM-1 and MW 50 were rarely used on the same engine. However, MW-50 was not a nitrous-oxide system, but a Methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

-water
Water injection (engines)
In internal combustion engines, water injection, also known as anti-detonant injection, is spraying water into the cylinder or incoming fuel-air mixture to cool the combustion chambers of the engine, allowing for greater compression ratios and largely eliminating the problem of engine knocking...

injection system, which injected a mixture of methanol and water into the cylinders to cool the mix. Cooling causes the air to become denser, therefore allowing more into each cylinder for a given volume. This is the same principle that intercoolers work on.

GM-1 was developed in 1940 by Otto Lutz in order to improve high-altitude performance. It could be used by fighters, destroyers, bombers and reconnaissance aircraft, though its first use was in the Bf 109E/Z fighter. Originally, it was liquified under high pressure and stored in several high-pressure vessels until it was found that low-temperature liquefied nitrous oxide gave better performance due to improved charge cooling. It could also be stored and handled more conveniently and was less vulnerable to enemy fire.

GM-1 was typically sprayed in liquid form directly into the supercharger intake from two jets of different bore while at the same time, the fuel flow was increased to take advantage of the additional oxygen from the nitrous oxide. The jets could be operated individually or in combination, yielding three steps of power increase, for example 120/240/360 HP at different GM-1 flow rates (60, 100 and 150 grams/sec). The development of a continuously variable injection system was considered, but apparently it never saw operational use.

Initially intended as standard equipment for the Luftwaffe, in operational service it was found that GM-1 had some drawbacks. The additional weight of the equipment reduced performance on all missions, while the system was only used in the cases where the aircraft went to very high altitudes. GM-1 also became less attractive than originally imagined when in 1943, the previous trend towards ever increasing combat altitudes ended.

While GM-1 saw little use in the second half of the war, the Focke-Wulf Ta 152H
Focke-Wulf Ta 152
The Focke-Wulf Ta 152 was a World War II German high-altitude fighter-interceptor designed by Kurt Tank and produced by Focke-Wulf. The Ta 152 was a development of the Focke-Wulf Fw 190 aircraft...

, which had been developed as a dedicated high-altitude interceptor, also received a GM-1 system to provide it with superior performance at high altitude. The Ta 152H was one of the few designs to support both GM-1 and MW 50.

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