Grasshopper, a testbed for reusable technologies, is expected to make a first flight before the end of 2012.

"I believe we'll have some flight tests before the end of the year," says Gwynne Shotwell, president of SpaceX. "[It's] very typical of the way we always do business: we follow the same step-by-step approach to development. My guess is we'll do some hops that are pretty short, learn what we need to learn and increase altitude."

The vertical take-off, vertical landing (VTVL) rocket, a modified Falcon 9 first stage, will fly from SpaceX's engine test facility in MacGregor, Texas. Eventually, the company plans to rely on fully reusable rockets, as opposed to the expendable rockets currently employed. A reusable rocket, while more limited in payload to orbit due to extra weight, shows potential to reduce launch costs dramatically.

"As a matter of fact, if you look at our Vandenberg launch site, it's actually called the 'Vandenberg launch and landing site'," says Shotwell. "But we've got a way to go with that, obviously. You need to understand the full characterisation of the stage coming in, how you burn [and] the aerodynamics associated with burning as you're re-entering.

"I have no question about the fact that we'll solve this problem," she adds. "[However,] I wouldn't put a date on it."

SpaceX is gearing up for the 30 April launch of the Falcon 9 and Dragon capsule. Upon successful launch, Dragon is scheduled to become the first commercial spacecraft to dock with the International Space Station. The launch, which has been delayed significantly since its inception, is scheduled for 7 May.

SpaceX is also contracted to modify the basic Falcon design into an air-launched vehicle for Stratolaunch, which is planning to build the largest aircraft in history to accommodate it. The rocket, once dropped from the carrier aircraft, must make a challenging aerodynamic turn to the vertical.

"There are definitely challenges associated with getting that rocket to be captive carried under a giant aircraft," says Shotwell. "That's probably one of the key areas that we're looking at right now: the aerodynamics associated with getting dropped and lighting. Because we won't be vertical, we have to do a pretty heavy manoeuvre to get headed in the right direction."

Shotwell expects to finish a preliminary design review for the Stratolaunch rocket in late 2012, with a critical design review in 2013.

"We're just getting through our system design phase," Shotwell says. "We should have a PDR late this year; CDR sometime in 2013 is the baseline plan. But there's a lot of knobs to turn in terms of max payload to orbit, how many engines you have on the back end, max gimbal angle and so on.

"We've got a number of cases to close," he adds. "We're just trying to optimize right now."

Source: Flight International