Virgin Galactic expects to begin testing a second SpaceShipTwo this year to replace the suborbital rocketplane lost in last year’s fatal test flight crash.

The company confirmed remarks attributed to chief executive George Whitesides at last week’s Space Symposium conference in Colorado, but stressed that testing includes work on the ground and “ultimately flight tests will be dictated by safety and readiness rather than deadlines”. The operation remains grounded while the US NTSB continues its investigation into the 31 October incident at Mojave, which killed Michael Alsbury and left the other test pilot, Peter Siebold, seriously injured.

In that crash, the rocketplane broke up soon after starting its rocket motor and going supersonic following its air-launch at about 50,000ft. The immediate cause of the crash appears to have been the unlocking of a feathering mechanism, meant to swing SpaceShipTwo’s tailplanes into a vertical position to slow it down – like a badminton shuttle – as it re-enters the atmosphere.

NTSB investigators have available a vast amount of data from the heavily instrumented craft, and has said it will be considering a broad range of factors, including the safety cultures at Virgin Galactic and Scaled Composites, builder of SpaceShipTwo and its dedicated carrier aircraft, the twin-fuselaged WhiteKnightTwo. Initial inspection of the wreckage determined that neither rocket motor nor fuel tank explosions had caused the accident, though one aim of that particular flight was to test a new solid rocket fuel.

About a week after the crash, Whitesides wrote in an open letter that the second SpaceShipTwo was “already two-thirds complete”, adding: “Our team are pouring themselves into that project with heightened resolve. Our will is indefatigable, and our team is determined.”

However, Virgin Galactic and Scaled Composites may have since modified the design. Whitesides told the Financial Times last week that the operation will probably end up with a “better spaceship” for the tragedy of October 2014.

At the time of the crash, Virgin Group boss Richard Branson was talking about a test flight into space during calendar year 2014, with the first passenger-carrying flight from Galactic’s operating base at Spaceport America New Mexico during February or March 2015 – with him and his family on board, a plan he has been touting during several years of delays to the programme.

However, before the crash powered flights of SpaceShipTwo had gone no higher than about 70,000ft – far short of the 300,000ft-plus that will eventually be needed to carry six paying passengers on a short suborbital flight above the internationally recognised 100km altitude boundary of space.

Clearly much depends on the outcome of the NTSB investigation and its recommendations. Some commentators have speculated that Branson may be forced to find a face-saving way to end the passenger programme, given the financial calamity that would presumably come of killing any of the nearly 700 people who have already booked flights. At about $250,000 for a six-minute experience of microgravity and stunning view of Earth, many of these “astronauts” are, of course, billionaires and wealthy celebrities.

However, Virgin Galactic is outwardly retaining its bullish enthusiasm. After the crash, the company’s elaborate website was replaced by a dour holding page, but it has been relaunched in glorious colour under the strapline “Spaceline for Earth” – with prominence given to a vision for a future driven by space travel.

In any case, the company is pressing ahead with plans, launched at the 2012 Farnborough air show, to use WhiteKnightTwo to air-launch small satellites – a potentially lucrative business. In February this year, Virgin Galactic leased facilities in Long Beach, California to design and build LauncherOne, a liquid-fuel two-stage rocket intended to orbit government or private satellites of up to 225kg – quickly, and at a cost of less than $10 million.

When he announced that project, Branson indicated that test flights could come in 2015 and commercial services in 2016.

Virgin Galactic crash

Mojave crash site, October 2014