Orbital’s Air Launched Rocket Gets Another Boost with Successful ST5 Spacecraft Launch

Pegasus launches from the L-1011. (NASA photo)

DULLES, VA, March 24, 2006/Satnews Daily/ — Orbital Sciences Corporation’s (NYSE: ORB) Pegasus space vehicle got another boost on Wednesday when it successfully “air launched” three small scientific spacecraft for the National Aeronautics and Space Administration's (NASA's) Space Technology 5 program (ST5).

The three 55-pound ST5 spacecraft were accurately delivered into their targeted elliptical orbits approximately 300 by 4,570 kilometers above the Earth 10 minutes after the Pegasus rocket was released from its L-1011 carrier aircraft at 9:04 a.m. (EST) to the time that the first of the three satellites were deployed into orbit. The remaining two ST5 satellites were then deployed at three-minute intervals.

Orbital’s patented air-launch system, in which the rocket is launched from beneath the company’s Stargazer L-1011 carrier aircraft over the ocean, is getting a lot of attention nowadays because of its reduced cost and its ability to provide customers with unparalleled flexibility to operate from virtually anywhere on Earth with minimal ground support requirements.

The technology will be 16 years in April this year. It was first unveiled on April 5, 1990 when a Pegasus rocket was launched for the first time from beneath a NASA B-52 carrier aircraft in a mission that originated from Dryden Flight Research Center in California.

In the decade since its maiden flight, Orbital claims Pegasus has become the world's standard for affordable and reliable small launch vehicles. The launch last Wednesday was its 37th mission, launching more than 78 satellites so far. It is also the 23rd consecutive successful mission according to Orbital.

Today, the three-stage Pegasus is being used by commercial, government and international customers to deploy small satellites weighing up to 1,000 pounds into low-Earth orbit. Pegasus is carried aloft by our Stargazer L-1011 aircraft to approximately 40,000 feet over open ocean, where it is released and then free-falls in a horizontal position for five seconds before igniting its first stage rocket motor. With the aerodynamic lift generated by its unique delta-shaped wing, Pegasus typically delivers satellites into orbit in a little over 10 minutes.

Pegasus prides itself as the world's first privately developed space launch vehicle. Its maiden flight in 1990 marked the first all-new, unmanned space launch vehicle developed in the U.S. in more than 20 years. It is also the first winged vehicle to accelerate to eight times the speed of sound and the first air-launched rocket to place satellites into orbit, using its carrier aircraft as an "air breathing reusable first stage."

There are numerous advantages for “air launch,” according to SpaceTethers.com. The first concerns air resistance, which is much more of a problem for a small ground launched rocket than a large one. The total energy of the rocket is determined by the amount of fuel, which goes up with the volume of the rocket, or the cube of the dimensions. This makes air launch much cheaper.

Launching at 40,000 feet is also much closer to a vacuum than sea-level, so the rocket is more efficient. In addition, a rocket taking off from a launch pad will probably fall back and explode if the engines fail during lift off. An air launched liquid fueled rocket should be able to dump fuel and land if the engines fail.

Another big advantage is by starting out high, the rocket can aim more horizontally. Since orbit depends mostly on horizontal velocity, air launch is efficient. Also, starting from higher up gives the potential energy of the height before the rocket is even started.

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