In 2005, a new trajectory

Trajectory

A trajectory is the path that a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass...

 that an air-launched rocket

Rocket

A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

 could take to put satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s into orbit

Orbit

In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

 was tested. Until this time, launch vehicle

Launch vehicle

In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure....

s such as the Pegasus rocket

Pegasus rocket

The Pegasus rocket is a winged space launch vehicle capable of carrying small, unmanned payloads into low Earth orbit. It is air-launched, as part of an expendable launch system developed by Orbital Sciences Corporation . Three main stages burning solid propellant provide the thrust...

, or rocket planes such as the X-1

Bell X-1

The Bell X-1, originally designated XS-1, was a joint NACA-U.S. Army/US Air Force supersonic research project built by Bell Aircraft. Conceived in 1944 and designed and built over 1945, it eventually reached nearly 1,000 mph in 1948...

, X-15, or SpaceShipOne, which were carried under an aircraft pointing in the same direction as the fuselage

Fuselage

The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...

, would have their engines ignited either just before being air-dropped or a few seconds afterward. They would then be expected to accelerate and climb in front of the carrier aircraft, crossing its flight path. This was considered dangerous due to the potential for a crashes between the rocket and the launch vehicle.

The aft-crossing trajectory is an alternate flight path for a rocket. The rocket's rotation (induced by the deployment from the aircraft) is slowed by a small 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...

attached to its tail, then ignited once the carrier aircraft has passed it. It is ignited before it is pointing fully vertically, however it will turn to do so, and accelerates to pass behind the carrier aircraft.

The principal advantage of this method is its safety for the crew of the carrier aircraft.