THEY call it the most powerful rocket ever built. NASA’s Space Launch System (SLS) is designed to carry astronauts on deep space missions, and is about to undergo its final ground test at a facility belonging to the rocket’s manufacturer, Orbital ATK.
I’m at the private viewing area, dotted with trailers, giant white tents, and an enormous video screen. The obligatory countdown clock stands on a nearby hill, red numbers glowing in the low morning light.
A single rocket booster is just 2 kilometres away – as close as we can safely get. The booster is tied down on its side, nozzle pointed into a human-cut ravine that will contain its flames. When the SLS launches for its first test flight in 2018, two of these will provide 75 per cent of its lifting power.
It’s 8.05 am on 28 June, the scheduled time for the test, but the booster is silent. The countdown clock is frozen because of a delay caused by a glitch in the booster’s monitoring system. As we wait for a simple parts swap, the tents fill with visiting dignitaries sheltering from the blazing sun.
The test is a straightforward one: does the booster fire for 2 minutes and 6 seconds, then stop? If so it will pass, and everything else is just details. But those details are important. More than 530 sensors will help the post-test analysis team pick apart every aspect of its behaviour. One team is even devoted to the world’s worst jigsaw puzzle: reassembling a styrofoam plug, currently jammed into the exhaust nozzle. Designed to control pressure for the first few seconds, the plug will mostly disintegrate as soon as the booster ignites.
Although the SLS will be the largest rocket the world has ever known, it will be some time before it claims that crown. The rocket I’m about to see go off is more powerful than the space shuttle booster it’s based on, but its first test flight with an empty Orion crew capsule in 2018 will have only half the lifting power of the retired Saturn V rockets that sent astronauts to the moon.
To get more thrust, NASA plans first to upgrade the SLS’s upper stage rocket for a second test flight in 2023, when Orion will carry a crew. After that, the booster itself will need an upgrade to be able to propel explorers into deep space.
That’s the plan – the elephant in the room is whether the project will keep getting the funding and policy support it needs. What’s more, the technology to keep humans alive in the harsh radiation of deep space doesn’t even exist yet. NASA’s previous deep space project, Constellation, died a quiet death the last time the US administration changed. With election season looming, will the SLS survive the whims of a new president?
No one is really worrying about that right now. At 9.05 am, the last few seconds count down on the clock, and the rocket flames into life right on cue. Cheers erupt as the flame extends, the booster quickly and visibly reaching full ignition. At first, it’s unnervingly silent, a physics lesson brought to life that light is faster than sound. A beat later, the shock wave literally hits us, accompanied by a roar that just doesn’t end.
This isn’t like a launch, in which the blast fades as the rocket tears away into the sky. The booster is locked into its ravine backstopped by solid rock. Inside its engine, gases heat to over 3000 °C, enough to boil steel. The noise continues, unleashing a tower of smoke as my heart thumps in counter-rhythm to a bass line I could never hope to match.
“It’s unnervingly silent at first – light is faster than sound. Then the shock wave literally hits us“
And then it’s over, flame sputtering out as a cooling arm swings into the nozzle, silence returning as the staggeringly tall smoke clouds start to feather in the gentle breeze. Later, when I can get up close to the booster, I learn that spent propellant reeks of burning tyres, offset by the scents of sun-warmed dirt and bruised sagebrush.
I can spot wild grins on the face of every Orbital employee and every NASA visitor. The SLS’s boosters have passed the test and are ready for launch. Everything from here on in is just details.
This article appeared in print under the headline “Close encounters of the rocket kind”