HAHO

High-altitude military parachuting (or military free fall (MFF)) is a method of delivering military personnel, military equipment, and other military supplies from a transport aircraft at a high altitude via free-fall parachute insertion. Two techniques are used: HALO (high altitude – low opening) and HAHO (high altitude – high opening).

In the HALO technique, the parachutist opens his parachute at a low altitude after free-falling for a period of time, while in the HAHO technique, the parachutist opens his parachute at a high altitude just a few seconds after jumping from the aircraft. Military HALO techniques date back to 1960, while in recent years, the HALO technique has been practiced by civilians as a form of skydiving.

In military operations, HALO is used for delivering equipment, supplies, or personnel, while HAHO is generally used only for personnel. In typical HALO/HAHO insertions the troops jump from altitudes between 15,000 feet (4,600 m) and 35,000 feet (11,000 m).

The origins of the HALO techniques date back to 1960 when the United States Air Force began conducting experiments that followed earlier work by Colonel John Stapp in the late 1940s through early 1950s on survivability for pilots ejecting at high altitude. Stapp, a research biophysicist and medical doctor, used himself in rocket sled tests to study the effects of very high g-forces. Stapp also solved many of the problems of high-altitude flight in his earliest work for the Air Force and subjected himself to exposure to altitudes of up to 45,000 feet (14,000 m). He later helped develop pressure suits and ejection seats, which have been used in jets ever since. As part of the experiments, on August 16, 1960, Colonel Joseph Kittinger performed the first high-altitude jump at 19.5 miles (31.4 km) above the Earth's surface. The first time the technique was used for combat was during the Vietnam War in Laos by members of MACV-SOG. SEAL Team Six of the United States Navy expanded the HALO technique to include delivery of boats and other large items.

...
Wikipedia