Guy Norris Mojave, Calif.

The Farnborough air show has seen plenty of “firsts” over the decades, but the appearance this year of the first passenger-carrying suborbital commercial spacecraft takes this prestigious event into new territory.

The show debut of Virgin Galactic's SpaceShipTwo (SS2), albeit in full-scale replica form, follows a tradition of inaugurals ranging from the 1949 display of the world's first jet airliner, the de Havilland Comet 1, to the initial international appearance of the largely composite-built Boeing 787 in 2010. Although the Farnborough show is not best known for its space-related coverage, the display of the SS2 mock-up follows the 2010 establishment of a special Space Zone exhibit which organizers say will be doubled in area this year.

Richard Branson's Virgin Group is no stranger to the event, either. In 2002, Virgin Atlantic and Airbus used Farnborough to showcase the formal delivery of the first A340-600. This time, Virgin Galactic says it is displaying SS2 at Farnborough to take advantage of the additional global focus on the U.K. now, as the country is hosting a series of events ranging from the Summer Olympics to the Diamond Jubilee celebrations of Queen Elizabeth II.

But while the SS2 replica hogs the PR limelight at the show, the hard development work continues across the Atlantic at sites in the Western U.S., where flight testing is expected to culminate at year-end with the long-anticipated first rocket-powered flight. Plans to begin powered atmospheric flight tests were boosted last month when the vehicle's developer, Scaled Composites, was granted an experimental launch permit by the FAA. “It was a big step, and there are a lot of big steps in this process,” says Virgin Galactic President and CEO George Whitesides.

The permit comes as the pace of flight tests picks up at Scaled Composites' facility in Mojave, Calif., following a hiatus for modification work on both the SS2 and the WhiteKnightTwo (WK2) carrier aircraft that is used to air-launch the spacecraft. “The vehicles are now flying again,” says Whitesides. With glide tests of SS2 having resumed June 26, he adds, “our hope is to have a high flight tempo over the next few months. The basic plan is to get through the majority of the unpowered flight envelope over the course of the summer, and we hope to be in a position at that point to integrate the remaining components of the rocket motor over the fall. We should then be in a position to conduct our first powered-flight by the end of the year.”

Throughout 2013, these flights will be progressively longer, with the aim of culminating with the first truly suborbital flights. Assuming testing goes as planned, and certification authorities sign off on the work, the first passenger-carrying flights could be taking place by the end of 2013, says Whitesides. Despite the slowdown in testing caused by the discovery of an unexpected tail stall during a flight last September, the resumption of flights is encouraging to the development team, he adds. “We're still reasonably happy with where we are on the schedule. We don't have an excess amount of margin, but that's OK. We are moving as fast as possible, and as fast as is safe,” Whitesides says.

Modifications to the SS2 include replacing a pair of smaller strakes on the inboard side of each vertical tail with a larger, one-piece, horizontal strake. These have been added “to provide more margin for tail stall at low angles of attack,” says Scaled President Doug Shane. The tail stall, which occurred almost immediately after release from the WK2 during a post-maintenance check flight, was overcome by the crew deploying the feathering mechanism. This is designed to increase drag during reentry from suborbit, but in this instance helped recover full control of the vehicle in the descent.