Spacewalking is the most complex and challenging thing an astronaut can do in space. It’s the holy grail of entire careers, to be working outside the International Space Station and floating above the Earth. Hervé Stevenin is head of Extravehicular Activity (EVA) training – spacewalking to you and me – at the European Astronaut Centre of the European Space Agency (ESA). He trains his astronauts at the Neutral Buoyancy Facility, a giant, octagonal pool 10m deep, and at the NASA undersea habitat off the coast of Florida. He reveals why it takes 150 hours of training, and how disaster can strike in the vacuum of space…
RISING Why do you dunk your astronauts underwater to train them for spacewalking?
HÉRVE STEVENIN ‘We can balance the weight of the astronaut and the EVA equipment so that they neither rise or sink in the pool – the sensation for the astronaut is as close to weightlessness as we can get here on the surface of the planet. An astronaut assigned to an EVA will spend around 150 hours training underwater before the spacewalk, and only the best in EVA training will ever be considered for a spacewalk.’
RISING When the astronauts are in the pool what do they wear to prepare them for their EVA?
HS ‘At ESA, we don’t have our own spacesuit but in our Neutral Buoyancy Facility, our astronauts will experience everything bar the awkwardness of moving inside a spacesuit. Our trainees wear a bulky wetsuit and full face mask, which gives a similar sensation of limited perception to a spacesuit and enables voice communications. They use the real EVA gloves with a stiff under layer to simulate the rigidity due to pressurisation in space – getting used to the lack of sensitivity in handling things is important. Their boots have the same soles as spacesuit boots and they learn to lock their boots into a restraint platform, so they can work hands-free.’
RISING What kind of things do they get up to?
HS ‘They wear a mini workstation – a kind of T bar worn on the torso as the attachment point of all the tethers and tools on the astronaut. The instructor simulates the ground station or ISS [International Space Station] control communications. There is also a full size mockup of the Columbus part of the ISS so we are able to run them through simulations of entry and exit of airlocks, safe navigation around the structure, and common repairs and jobs for an EVA.’
‘There is a sunset, followed by a sunrise 45 minutes later, so half of their EVA is in darkness’
RISING So, what are the differences between underwater training and a real spacewalk?
HS ‘The key difference is the influence of the water. In the pool it’s difficult to initiate a movement because of the resistance of the water, and it’s easy to stop it. You just let go, and the friction of the water will stop the tool or body movement. In space it’s the opposite – you can start a movement with a finger push, but to stop is more difficult, you have to slow yourself down. Because we cannot simulate that here on Earth, the first time an astronaut goes into space, he or she is given a 10 minute adaptation period to get used to this, practising moving, and understanding the difference from the underwater environment.’
RISING The last time we went swimming there was a bottom to the pool, but that doesn’t apply to space?
HS ‘Yes, another difference is that when you are in the pool, up and down is clear and can never be mistaken. You can never confuse your orientation. In space you can become disorientated, there’s no reference point. Not even the Earth’s position is consistent with your mental image of up and down; and day and night conditions change every 45 minutes. There is a sunset, followed by a sunrise 45 minutes later. The astronaut has to work for half of their EVA in darkness using the light from their helmet torch. They don’t experience this in training but do get used to it very quickly.’
RISING How long can you last on a spacewalk?
HS ‘A spacewalk is limited by the life support system of the suit, so about six hours.’
RISING It’s a risky business – what emergencies do you train for?
HS ‘The worst is the incapacitated crew situation. If an astronaut in EVA is unable to move back to the airlock because they are unconscious after a malfunction in the life support system of the suit, or being still conscious but unable to move, the astronaut buddy must rescue them in less than 20 minutes. The victim is secured to the rescuer with a tether and pulled or pushed along the station structure back to the airlock. It’s a very challenging task, which is trained underwater, including at the ESA-NBF in Cologne. These emergencies have never happened so far on a spacewalk.’
‘Who could have imagined that an astronaut could almost drown in space?’
RISING What has been the most dangerous spacewalk ever?
HS ‘I was in the control room at the European Astronaut Centre when it happened. Luca Parmitano had a leak in his suit cooling system and water started to accumulate at the back of his head. In weightlessness water adheres to surfaces by capillarity, so his head got covered with a thin layer of water, which slowly moved to his ears and eyes. The EVA was terminated by Mission Control but it even got worse for Luca when the sun set and his helmet torch light was reflected by the water, blurring his vision in the darkness. He was unable to see and unable to hear. With water reaching the suit microphone, no-one could hear him. Water was even about to cover his nose and mouth. He stayed very calm and rescued himself, returning by feel along his safety tether to the airlock. We came close to a space tragedy – who could have imagined that an astronaut could almost drown in space? Attending this in real time, I felt like being in the Twilight Zone, watching anxiously as my friend Luca came close to drowning in his own spacesuit.’
RISING What is the future for spacewalks? Could humans ever be replaced by robots?
HS ‘There will always be a place for humans. The environment is so complex, and relatively unpredictable. Humans bring their ability to adapt and be flexible in a changing situation. Robots are good for predictable or repetitive tasks, or where more than human strength is needed. A good example was the relocation of the Columbus module from the shuttle and docking it with the ISS, only the large robotic arm could do that, and it was operated by an astronaut inside the ISS. But for difficult external tasks, installation or relocation of equipment, power and fluid cables routing and plugging, maintenance and repair tasks, astronauts in EVA are definitely required. It’s not a competition between robots and humans, it is all about cooperation, with robots supporting humans.’
‘Weightlessness is freedom – you don’t realise that gravity is a permanent constraint for us’
RISING You are a veteran of more than 1,000 of the ‘vomit comet’ flights that simulate a few seconds of weightlessness inside a plummeting plane. Do you remember your first time?
HS ‘I will never forget my first time weightless, the first five seconds of free floating in the plane I had the feeling that “oh my god I am falling”, the instinct is to grab hold of something to feel more secure. Seconds later you realise how easy and wonderful it is to be floating in weightlessness. I love to go back to do it. You don’t realise that gravity is a permanent constraint for us, until you are freed from it for the first time. It’s so comfortable and efficient to move around when you are floating. Weightlessness is freedom. It’s hard for our astronauts to come back to the influence of gravity, especially during the four Gs of the reentry. The contrast is so strong with months of being in weightlessness, that it’s like trying to move your arm with 20kg attached to it.’
RISING What do movies like Gravity and The Martian get hopelessly wrong when they depict spacewalks?
HS ‘What is fully unrealistic is the high speed that the actors move around in spacewalk without even being attached to anything. They’d fly off immediately into space on a real life EVA. But I guess if they moved at a realistic slow speed the movie action could become boring! In the final scene [spoiler alert] of the rescue of Matt Damon in The Martian, one astronaut in a jetpack was trying to reach him in a critical situation, she was attached to the structure with a tether preventing her to move close enough to save her colleague. The purpose of a jetpack is to let the astronaut move freely, untethered. So here again the movie got it wrong just to increase the drama of the situation.’
RISING So is it all nonsense, or do the movies get some of it right?
HS ‘What these two movies do very well is to share the feeling that you get inside a spacesuit. The feeling of isolation, of confinement, of loneliness, hearing your own breath inside the helmet, looking at your hands and tools through the visor. There are some very realistic shots where you do get the exact view that you would have from inside a spacesuit. It’s very similar to EVA suit training and for those who have had the chance to spacewalk, it brings them back to space.’
WHAT NEXT? Watch Hervé and his astronauts on a simulated mission to a moon of Mars in an ESA video at Aquarius – a subsea habitat on the ocean floor off Florida.