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“This will be a unique rocket,” says SLS systems engineer, Dawn Stanley. “It’s going to get us back to the Moon and beyond the Moon to asteroids and Mars, further than we’ve ever gone before.”
Stanley is based at Marshall Spaceflight Center in Huntsville, Alabama, behind the high security fences of the Redstone Arsenal – for more than 60 years the home of America’s missile and rocket programme. The 154 sq kilometre (60 sq mile) site is dotted with firing ranges, test stands and discarded space hardware.
Conscious of all this history around her, Stanley says the new spacecraft is designed to be more versatile than anything that has gone before.
“If they want us to go to an asteroid to do a retrieval mission, this rocket can get you there or if you want to go to Mars, this rocket can get there,” she says. “The SLS can meet those many missions that our government has.”
The first four SLS launchers will use spare engines left over from the Space Shuttle programme, the solid rocket boosters are longer versions of the ones used on Shuttle; and the upper stage engine is based on a 1960s Saturn 5 design. Stanley makes no apologies for this rocketry recycling.
“To get off the Earth, we still need a rocket so we’re using Shuttle technology and technology from Apollo but we’re also infusing new technology,” she says. “Our core stage is a new design and we’re using new manufacturing techniques to get an efficient and affordable rocket built.”
The SLS itself is taking shape some six hours drive south of Huntsville in Nasa’s vast Michoud assembly facility near New Orleans. Almost a kilometre long, this factory was used to build the Saturn V rocket and, until, recently the Shuttle’s external fuel tank.
Because of its size most of the workers get around the rocket factory on bicycles or, if they are really lucky, white Austin Powers-style electric buggies – complete with Nasa emblems on the side.
We drive past the first barrels, rings and domes of the new rocket, arranged across the factory floor like some sort of modernistic Stonehenge. Each one is made from sheets of aluminium, only a few millimetres thick in places but given structural integrity by an internal lattice of thicker metal. These gleaming structures will soon be welded together to form the central core of the rocket. This will be filled with fuel tanks, engines and control systems.
“Welding typically uses lots of heat, fire and smoke,” explains SLS engineer Brent Gaddes. “Friction stir welding is totally different because you never completely melt the metal – you actually stir it together. The metal never gets above the melting point.”
It’s a remarkable process to watch – two panels are clamped together and a computer-controlled rotating spindle moves along the join. It takes only a few minutes for even the longest welds, which are stronger and more reliable than anything produced using conventional welding techniques.