NASA got the sternest possible reminder of the hazards of spaceflight when an International Space Station resupply mission ended in spectacular failure on 28 October, just metres above the launch pad at Wallops Island, Virginia.
Seconds after lift-off, the Antares rocket – developed and operated by Orbital Sciences under the private sector partnership scheme NASA has relied on for cargo flights since it retired its Space Shuttle fleet in 2011 – exploded in a fireball, made all the more spectacular for being a night-time launch.
No-one was hurt on the ground, early indications pointed to the survival of at least some of the launch pad infrastructure and the six ISS crew currently in orbit are in no immediate danger of running short of provisions. However, at a press conference later in the evening, NASA’s associate administrator for human exploration and operations acknowledged Congressional critics of NASA’s private sector launch partnerships, which will see Boeing and SpaceX ferrying US astronauts to the ISS from 2017, a service currently bought from the Russians.
Noting that the rockets which will carry US astronauts will not use the Antares’s AJ-26 main engines, William Gerstenmaier on several occasions underscored that space launches are a “tough business”. As for upcoming human launches by private contractors, he says that he and NASA have been “pretty open with our Congressional friends in Washington, explaining how difficult our launch business is”.
And, he went on: “The important thing is we don’t overreact to this failure. That we really understand what occurred… and that we fix it, and fix it with some confidence.”
This failure, he says, was a “reminder of how difficult this business is, how careful we have to be. How the small things matter in this launch business”.
But Gerstenmaier, in a further remark clearly aimed at everyone associated with launches in NASA and its contractors, says: “Don’t get over-confident.”
Cargo flights, he says, are a learning opportunity “where we can afford to have some failures”.
Flight Orb-3 was the third ISS-bound mission for Antares and Orbital’s Cygnus spacecraft, following two successful flights earlier this year. The cause of failure is not yet known, but video of the accident shows the steady burn of the rocket’s main engine become a violent explosion at the base of the vehicle, which then drifted sideways slightly before falling tail-first back to the ground.
The Antares main engines are supplied to Orbital Sciences by Aerojet Rocketdyne, which acquired from Russia a number of Soviet-era NK-33s, originally designed in the 1960s for the Soviet Moon programme. Refurbished and “Americanised”, the engines are “extensively tested”, “tough” and “robust”, says Orbital executive vice-president Frank Culbertson. And, he adds, all engines are thoroughly tested before being fitted to Antares rockets, so there is as yet no cause to suspect a link between the latest failure and a testbed failure experience in May 2014 at NASA’s Stennis Space Center. The accident investigation, he says, is being led by Orbital Sciences with support from the US Federal Aviation Administration and NASA.
The ISS carries sufficient provisions to support its crew for four to six months, but it will be met by a 29 October Progress resupply flight from Baikonur in Kazakhstan, and on 9 December a SpaceX Falcon 9 flight is also being readied.
Some cargo planned to fly on the SpaceX flight may be swapped out for items lost in the Antares explosion, NASA says.
In addition to food, water, gasses and other consumables a number of scientific experiments were lost, but all of that hardware will eventually be replaced, says NASA’s ISS programme manager, Mike Suffredini. He adds that while the ISS crew were “disappointed” about the loss, they had plenty of scientific work to do in orbit even without the lost cargo.
The next crewed flight to the ISS is scheduled for 23 November from Baikonur – the sole route to the station since the Space Shuttle fleet’s final grounding. The crew will be Anton Shkaplerov (Russia), Terry Wirts (USA) and Samantha Cristoforetti (Italy).