Thunderbolt / Pegasus II - Eagles Launch System

In 2015, Stratolaunch ceased working with Orbital on the three-stage Thunderbolt launch vehicle which aimed to put 13,500 lb. into a 220 naut. mile orbit. The Thunderbolt was designed to use ATK-provided solid rocket motors for the first and second stages, while the third was due to be powered by two liquid-fueled Aerojet Rocketdyne RL10C engines.

The Stratolaunch Eagles program was a Paul Allen project designed to address the space industry’s need for a responsive and flexible space launch system capable of increased flight rates for intermediateclass payloads. Eagles would employ the world’s largest aircraft developed by Scaled Composites, builder of the White Knight aircraft, as an air breathing reusable first stage to launch larger classes of payloads than any similar platform.

To help make the Stratolaunch vision a reality, Orbital ATK was leveraging its vast launch vehicle and launch operations expertise to develop the Air Launch Vehicle. Orbital ATK was applying technology from its patented Pegasus® air-launch system and the Defense Advanced Research Projects Agency (DARPA)-sponsored Taurus® program that was designed for easy transportability and rapid launch, to reduce cost and provide unparalleled flexibility to operate from virtually anywhere on Earth with minimal ground support.

The Air Launch Vehicle was a multistage rocket that combines demonstrated rocket technologies and a proven winged configuration on a large scale. The Eagles system was designed to be EELV compliant, capable of launching payloads in the 10,000 pound class [ten times the Pegasus payload] to low-Earth orbit (LEO), and smaller payloads to geostationary transfer orbit (GTO). The Air Launch Vehicle design utilizes Orbital ATK’s proven Modular Avionics Control Hardware (MACH), engineering standards and common vehicle and payload integration processes utilized in the Pegasus, Taurus, Minotaur and Antares™ launch vehicle families.

On 19 May 2014 Aerojet Rocketdyne, a GenCorp company, received a contract from Stratolaunch Systems Corporation(SSC) to provide six RL10C-1 production engines, with an option to provide an additional six RL10C-1 production engines at a later date, for the third stage of a revolutionary commercial air-launch system. The inaugural launch of Thunderbolt, the air-launch vehicle designed and developed for SSC, ess scheduled for 2018.

"Aerojet Rocketdyne was pleased to provide RL10C-1 production engines for the Stratolaunch air-launch vehicle," said Steve Bouley, vice president of Space Launch Systems at Aerojet Rocketdyne. "The RL10 family of engines has a long history of reliability and dependability. This contract expands our reach into commercial ventures and builds greater volume, providing more affordable propulsion to all of our customers."

The design concept for the Eagles Launch System involved the launch of an unmanned rocket dubbed Thunderbolt, carrying a commercial or government payload from beneath the fuselage of a giant carrier aircraft. According to the concept, the carrier aircraft would be powered by six Boeing 747 class jet engines and have a wingspan greater than the length of a football field. Upon reaching a prescribed altitude, the rocket would be dropped from the aircraft, at which point two stages of solid rocket boosters would fire and propel the rocket skyward. Once the solid rocket boosters are expended, two Aerojet Rocketdyne RL10C-1 engines would ignite to ultimately place the satellite into proper orbit. The RL10C-1 was a liquid-fuel cryogenic rocket engine designed and developed from the RL10 family of upper-stage engines, which have accumulated one of the most impressive lists of accomplishments in the history of space propulsion.

When announced in 2014, it was stated that flight testing would begin in 2016.

Air Launch Vehicle	Pegasus-XL	"Thunderbolt"
Manufacturer	Orbital ATK	Orbital ATK
Length	55.4 ft	131 ft
Wingspan	22 ft	40 ft
Weight	51,000 lbs	500,000 lbs
Stage 1 and 2	ATK Solid Rocket Motors	ATK Solid Rocket Motors
Stage 3	ATK Solid Rocket Motor	Liquid hydrogen/oxygen with two RL10C engines
Payload Accommodations	..	1,000 lb to LEO 10,000 lb to LEO EELV compatible fairing envelope Temperature and humidity controlled