Virgin Orbit's modified Boeing 747-400 carrier aircraft, Cosmic Girl, is being readied for a series of ground and flight tests in the build-up towards captive carry evaluations of the company’s LauncherOne small satellite launch vehicle.
The initial ground test phase will begin in early August and follows delivery of the former Virgin Atlantic Airways 747 to the company's Long Beach, California headquarters on July 31. The aircraft arrived after completing final checks for its FAA experimental aircraft certification in nearby Mojave where the bulk of flight testing will be based. Conversion to its carrier role was completed during an extensive 16-month modification program at L-3 Platform Integration in Waco, Texas, from where an initial check-out flight was conducted on July 13.
"Now we will get into flight test and will start delivering rockets," says Virgin Orbit CEO Dan Hart who adds the arrival of the carrier aircraft represents a significant milestone for the company’s plan to deliver satellites to space with a target price of below $10 million per flight. The LauncherOne is designed to carry 440 lbs. into standard sun-synchronous orbits, or more than 880 lbs. into to low Earth orbit.
Stripped while in Texas of more than 65,000 lb. of cabin interiors and other fittings, the principle modification work focused on beefing-up the inboard port wing, skin, spars and ribs to handle loads of up to 85,000 lb. The initial load, including a specially designed pylon now in final assembly at Long Beach, will be 65,000 lb., of which around 55,000 lb. will be made up by the launch vehicle. The pylon will attach to the lower inboard wing between the fuselage and No.2 engine at a location originally designed by Boeing for the external ferrying of spare engines.
To take the weight of the rocket and pylon the wing has been locally strengthened with multiple doublers supporting attachments at the fore and aft main wing spars, plus an external longeron attached to a supporting wing rib. The pylon will attach to three main fittings mounted to the front spar and a fourth aft fitting beneath the rear spar. Modifications also include the addition of tubes and wire harnesses inside the leading edge which will connect the pylon and rocket with electric and pneumatic systems, as well as with tanks inside the fuselage containing gaseous nitrogen and helium.
Although ground vibration tests of the baseline modified 747 have been conducted to check for aeroelastic stability as well as for detecting potential structural issues, a second series of vibration tests will shortly begin in Long Beach to check for aeroelastic response with a mass representing LauncherOne. “We will get a basic understanding of the interaction between the airframe and the rocket, and that will be a big part of understanding the flight characteristics,” says LauncherOne chief engineer Kevin Sagis.
Flight testing will be divided into four main stages with the initial phase focused on baseline performance of the ‘clean’ aircraft without the pylon or launch vehicle. Phase two will test performance with the pylon attached. Phase three will be divided into two with the initial work testing the pylon with an empty rocket, and a second period of tests with the rocket ‘wet’ and loaded with water. The fourth phase will be a complete dress rehearsal with the rocket prior to the first release and firing flight test. Virgin appears confident the bulk of the work will be completed over the next four months, though no specific target date for the first launch is yet being disclosed. “We are taking a methodical approach to the flight test and will expand the flight envelope in a thoughtful fashion. It is a crawl, walk, run,” says Sagis.