Rocketplane outfits Learjets for commercial spaceflight missions

 - October 16, 2006, 12:31 PM

In the race for space tourism dollars, Oklahoma-based Rocketplane is vying for a head start by refurbishing hardy Learjet 25 airframes as the platforms for suborbital reusable launch vehicles capable of carrying up to four people to altitudes of 330,000 feet.

“Learjets are generally certified to 51,000 feet, and the [atmospheric pressure] difference between 51,000 feet and the vacuum of space is about a tenth of an atmosphere,” Rocketplane vice president and program manager David Urie told AIN. “We’re going to burst one fuselage as part of the pressurization testing just to make sure.” [The Learjet 25 was originally certified to a maximum ceiling of 45,000 feet; some later models were cleared to 51,000 feet.–Ed.]

Founded in 2001, Rocketplane began operations in June last year after selling $13 million in transferable investment tax credits from the state of Oklahoma. Since then it has hired approximately 30 employees, the bulk of whom are engineers and tradesmen, spread across four locations in Oklahoma and Green Bay, Wis., and taken delivery of two Learjet fuselages.

The company is using the first, a repossessed Learjet 24 fuselage, as a ground-test article. It will convert the second airframe, a Learjet 25 fuselage, essentially the same as that of the 24 but slightly longer, into the first Rocketplane XP ship. All subsequent Rocketplane XP vehicles will be built from Learjet 25 airframes, although the company is also developing a completely new two-stage launch vehicle for satellite delivery and other space services.

Flying into Space

The Rocketplane XP concept involves stripping out the Learjet fuselage, installing new wings, replacing the original General Electric CJ610 turbojets with more efficient turbofans and installing an Orbital Technologies reusable rocket engine. The as yet unspecified air-breathing engines will take the Rocketplane XP to approximately 30,000 feet, where the liquid oxygen and kerosene-fueled rocket engine will ignite.

After an 80-second burn, the engine will shut off at an altitude of about 158,000 feet; the vehicle will continue to its 330,000- foot apogee before beginning its descent and gliding back to Earth.

“It’s a very simple wing as it doesn’t have a lot to do,” Urie said. “It essentially lifts the airplane off the runway, provides aerodynamic lift during climb, does a 3g pull-up to begin rocket ascent and provides the gliding surface on the way home. But it’s not as sophisticated as the wing of a business jet, which has to be efficient at cruise. We don’t have any cruise.”

Participants will experience three to four minutes of weightlessness during the half-hour flight, which will start and end at the former Clinton-Sherman AFB in Burns Flats, Okla. Now dubbed Spaceport Oklahoma, the former Air Force base maintains the third-longest runway in the U.S.

Currently headquartered at Will Rogers Airport in Oklahoma City, Rocketplane will soon move its main operations to Burns Flats to prepare for vehicle development and testing. According to Urie, the company has completed preliminary design review and is set to complete the critical design review in September. First flight of the prototype Rocketplane XP is set for October next year, with first space tourism revenue flights scheduled for early 2007.