Pegasus celebrates quarter of a century milestone

In an era of new launch system development, Orbital ATK’s Pegasus has shown her staying power, passing the milestone of 25 years of operation. The air-launch system will continue to provide a unique role until at least 2017 and her heritage may also live on as part of the Stratolaunch system that is currently under development.


Pegasus’ milestone comes just months since Orbital and ATK officially merged into one single company. However, the two organizations had already worked together in the past – not least with the Pegasus system.

Pegasus and derivatives have accounted for over 150 vehicle sales worth more than $4 billion during the last quarter of a century, according to Orbital ATK.

Pegasus made her maiden flight on 5 April 1990, carrying the Pegsat and SECS satellites for NASA and the US Navy respectively.

Following the rocket’s first flight, the Pegasus development team received the National Medal of Technology from President George H. W. Bush and the Air and Space Museum Trophy from the Smithsonian Institution, among other honors and awards.

2015-04-06-135715Early launches were made using NASA’s NB-52B, nicknamed Balls 8, mostly flying from Edwards Air Force Base.

Six launches were made using the original Pegasus, two of which used Hydrazine Auxiliary Propulsion System (HAPS) fourth stages to refine the payload’s orbit.

Both of the HAPS launches were partial failures; one due to the first stage being late separating from the rocket, and the other due to the HAPS stage underperforming.

The original Pegasus and Pegasus-H were three-stage all-solid rockets, with an Orion-50S first stage fitted with wings and fins, an Orion-50 second stage, and an Orion-38 third stage.

PegasusCam, via L2The sixth Pegasus launch was the first flight of the XL configuration, with extended first and second stages.

The Pegasus-XL uses an Orion-50SXL, an Orion-50XL and an Orion-38.

(L2 Link to full onboard cam video of a Pegasus launch)

The rocket’s tail was also redesigned, allowing it to be launched by Orbital Sciences’ Lockheed L1011 TriStar aircraft rather than NASA’s B-52.

Originally delivered to Air Canada in March 1974 as C-FTNJ, the aircraft was used for passenger flights until it was bought by Orbital in May 1992. The aircraft carries the registration number N140SC.

Pegsus' Stargazer AircraftThe aircraft is named Stargazer after the USS Stargazer from Star Trek, a ship formerly commanded by Captain Picard.

This was an inside joke, as the ship his first officer had previously served on was named Pegasus. In addition to being used for Pegasus launches, Stargazer is used for high-altitude research flights.

Most Pegasus launches are conducted with Stargazer flying from Vandenberg Air Force Base; however, several other sites, including some outside the United States, have been used. Stargazer is one of only 11 TriStars still flying.

In addition to Edwards and Vandenberg, Pegasus launches have been made from the Kennedy Space Center, the Cape Canaveral Air Force Station, NASA’s Wallops Flight Facility, Bucholz Army Airfield at Kwajalein Atoll in the Marshall Islands and Gran Canaria Airport in the Canary Islands.

Pegasus XLThe maiden flight of the Pegasus-XL carried the STEP-1 for the US Space Test Program. The rocket failed to achieve orbit after its wing suffered a structural failure.

The flight following this failure was the final launch of the original Pegasus, and the next mission after that was the debut of the Pegasus-H, which featured the tail modifications of the Pegasus-XL, but without the stretched stages. Four Pegasus-H rockets were launched.

Following the first Pegasus-H launch, the Pegasus-XL made its second launch. Like its first, this failed to achieve orbit, this time because of a problem with the second stage.

That launch would have deployed the STEP-3 satellite – the third STP satellite to be involved in a Pegasus launch failure as STEP-2 was payload for the second of the partially unsuccessful Pegasus/HAPS launches.

PegasusThe third Pegasus-XL launch, in March 1996, successfully deployed the STP’s REX-2 satellite. Another failure occurred a few flights later, when in November 1996 the sixth Pegasus-XL launched from Wallops Island with NASA’s HETE gamma-ray astronomy satellite and Argentina’s SAC-B.

Despite reaching the planned orbit, both payloads failed to separate from the rocket, running out of power a few days after launch as they were unable to orient their solar panels towards the sun.

Since that failure, Pegasus has made 28 consecutive successful launches, with the latest coming in 2013 via the deployment of NASA’s Interface Region Imaging Spectrograph (IRIS) satellite.

In total, Pegasus has placed over 80 satellites into orbit, launching from six different launch sites worldwide.

Pegasus has also formed the basis for several other rockets. The Taurus rocket, which has made nine launches with three failures, consists of a wingless Pegasus or Pegasus-XL boosted by a Castor 120 solid rocket motor or the first stage of a retired Peacekeeper missile.

The Orbital Boost Vehicle, developed for the US military’s Ground Based Interceptor program, uses the upper stages of the Taurus, making it essentially a silo-launched Pegasus with no wings.

Also, the HXLV was an air-launched rocket, using the first stage of the Pegasus dropped from the NB-52, to boost a hypersonic flight experiment as part of NASA’s Hyper-X program – showing a deep heritage in technology development across the industry.

2015-04-06-140942“Pegasus combined major technological advances in propulsion systems, composite structures, digital avionics and aerodynamic design with a new business model involving commercial development and operation of space launch vehicles,” noted Dr. Antonio Elias, Orbital ATK’s Chief Technical Officer and Pegasus’ inventor.

*Click here to read an extensive Q&A with Dr. Elias*

“The spirit of innovation that Pegasus reflects is alive and well at Orbital ATK today, with several exciting new projects now underway.

“These include novel space systems, advanced precision weapons and, yes, new launch vehicles made possible by the combined capabilities of ATK and Orbital.”

Pegasus II via L2One such project is “Pegasus II” – as nicknamed – which is being designed for use with the Stratolaunch system.

However, changes to that program may result in numerous changes to the rocket the giant airplane is set to carry.

Following the successful launch of IRIS, Pegasus is looking forward to at least two more launches.

The Pegasus air-launch system remains the only NASA Category 3 certified small launch vehicle today, a distinction reserved by the space agency for its highest value payloads.

(Images: via L2, Orbital ATK and NASA.)

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