Mid-air retrieval is a technique used in atmospheric reentry

Atmospheric reentry

Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...

 when the reentering vehicle is incapable of a satisfactory unassisted landing. The vehicle is slowed by means of parachute

Parachute

A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...

s, and then a specially-equipped aircraft

Aircraft

An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 matches the vehicle's trajectory and catches it in mid-air.

This is a risky technique, and so is only used when other forms of landing are infeasible. Successful mid-air retrieval requires correct operation of the retrieving aircraft, favourable atmospheric conditions, and successful execution of a tricky manoeuvre, in addition to correct operation of the vehicle itself. Complicating matters, helicopter

Helicopter

A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

s, which are the optimal aircraft for these operations due to their maneuverability, are particularly prone to mechanical breakdown. These risks can be mitigated somewhat: for example, multiple recovery aircraft can be used. The need for human

Human

Humans are the only living species in the Homo genus...

 aviator

Aviator

An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...

s to perform a manoeuvre which would normally be classed as a stunt

Stunt

A stunt is an unusual and difficult physical feat, or any act requiring a special skill, performed for artistic purposes in TV, theatre, or cinema...

 may in the future be avoided by advances in unmanned aerial vehicle

Unmanned aerial vehicle

An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...

s.

Uses

The first successful mission use of mid-air recovery was on 1960-08-19 when a C-119 recovered film from the Corona mission code-named Discoverer 14

Discoverer 14

Discoverer 14 was a spy satellite used in the Corona program managed by DARPA and the United States Air Force. On 19 August 1960, usable photographic film images taken by the satellite were recovered by a C-119 recovery aircraft...

. This was the first successful recovery of film from an orbiting satellite and the first aerial recovery of an object returning from Earth orbit.

Notable uses of the technique:

• The early-1960s era Corona
  Corona (satellite)
  The Corona program was a series of American strategic reconnaissance satellites produced and operated by the Central Intelligence Agency Directorate of Science & Technology with substantial assistance from the U.S. Air Force...
  
   reconnaissance satellite returned delicate film
  Photographic film
  Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
  
   capsules to Earth
  Earth
  Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
  
   that required mid-air retrieval by a JC-130 Hercules & HC-130 airlift
  Airlift
  Airlift is the act of transporting people or cargo from point to point using aircraft.Airlift may also refer to:*Airlift , a suction device for moving sand and silt underwater-See also:...
  
  er. These aircraft were manned by a crew of 10 personnel. The crew consisted of two pilots, one flight engineer, two telemetry operators, one winch operator, and four riggers. The telemetry operators would acquire the location of the satellite and relay the info to the pilots. Once visually acquired the pilots would head on course to the satellite descending towards the Pacific Ocean. One could visually acquire the satellite and its parachute at an altitude of approximately 50,000 ft. The winch operator and the riggers would deploy the retrieving apparatus called the "Loop", which consisted of high quality nylon rope with a series of brass hooks spliced into the apparatus. The whole snatching operation by the pilots was done visually. The winch operator and the four riggers would deploy the loop. Once contact was made between the parachute and the loop the winch line would pay out and stop. The winch then was put into gear and the retrieval process commenced. Once on board, the aircraft flew back to Hickam Air Force Base, where they were stationed and offload the satellite or the canister onto a truck and then loaded immediately onto a running C-141 airlifter and then transported to a location, in Maryland, for analysis. The crews acquired these skills by practicing almost daily on practice missions, carried out with other aircraft dropping dummy bombs with chutes attached. The weights were 200 lb. in the early 70s and later to the conical parachute system which weighed in at 1,100 lb.
• The Genesis
  Genesis (spacecraft)
  The Genesis spacecraft was a NASA sample return probe which collected a sample of solar wind and returned it to Earth for analysis. It was the first NASA sample return mission to return material since the Apollo Program, and the first to return material from beyond the orbit of the Moon...
  
   mission returned a sample of solar wind
  Solar wind
  The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
  
   that was so delicate that it would have been damaged by a parachute landing, so a mid-air retrieval using helicopters flown by Hollywood stunt pilots contracted by NASA was planned. Its parachutes failed to deploy, leading to a disastrous high speed impact with the desert floor which shattered the sample wafers holding the solar wind samples.
• An early design for SpaceShipOne called for a shuttlecock
  Shuttlecock
  A shuttlecock, sometimes called a bird or birdie, is a high-drag projectile used in the sport of badminton. It has an open conical shape: the cone is formed from sixteen or so overlapping feathers, usually goose or duck and from the left wing only, embedded into a rounded cork base...
  
  -like shape that would have made it incapable of landing independently, necessitating mid-air retrieval. This was deemed too risky, and the final design made the spacecraft capable of independent horizontal landing while cleverly retaining the desired aerodynamic qualities for the early part of reentry.

Image gallery

File:CORONA_reentry_parameters.PNG|CORONA re-entry parameters
File:corona recovery sequence.PNG|CORONA recovery sequence