High-altitude military parachuting

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, often called a HALO jump) and HAHO (high altitude – high opening). In the HALO technique, the parachutist opens the parachute at a low altitude after free-falling for a period of time, while in the HAHO technique, the parachutist opens the parachute at a high altitude just a few seconds after jumping from the aircraft. Although HALO techniques were first developed in the 1960s for military use, in recent years HALO parachute designs have been more widely used in non-military applications, including as a form of skydiving. In military operations, HALO is also used for delivering equipment, supplies, or personnel, while HAHO is generally used exclusively for personnel. In typical HALO/HAHO insertions the troops jump from altitudes between . Military parachutists will often reach a terminal velocity of , allowing for a jump time under two minutes. The origins of the HALO technique 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 U.S. Air Force and subjected himself to exposure to altitudes of up to . 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 above the Earth's surface. Kittinger's friend and United States Naval Parachute Test Jumper Joe Crotwell was also among the consultants and test jumpers of the original program.