This year the Royal Institution’s Christmas Lectures look at the challenge of human space flight and what it takes to hurl humans into the final frontier on voyages of exploration.
As a doctor I spent more than a decade travelling back and forth between the UK and Nasa’s Johnson Space Center in Houston, working as a visiting researcher on projects ranging from studying the effects of the space environment on ageing physiology to artificial gravity systems. At the same time I was completing my junior medical training in anaesthesia and intensive care. It was odd trying to splice those two lives together. Working on an intensive care unit overnight, heading to the airport at the end of the shift, grabbing some sleep on the plane, and then arriving the next day in a meeting room in Houston, where people were sitting around talking about how to send people safely to Mars.
But the thing that linked the two was the challenge of life at the extremes. In the hospital I was looking at the extremes of life when challenged by disease and injury. At Nasa I was looking at the threat posed to human physiology by the extremes of the physical world and universe.
When we talk about extreme environments we can get a rough idea of their austerity by judging how long they will support human life unprotected and unsupported. By that measure space is the ultimate extreme: uniquely hostile to human physiology, it provides no support for human life whatsoever. The unprotected space traveller would survive in that environment merely for a few seconds.
You might imagine that there would be plenty for a doctor to do – that when it comes to human space exploration, people who understand and can manipulate human physiology would be at the forefront of that effort. But medical doctors play a poor second fiddle to what is overwhelmingly a culture of engineering – and with good reason.
Space flight is in physical principle disarmingly simple. So simple in fact that Newton had begun to understand the dynamics that underpin it nearly 400 years ago. To leave the Earth and enter an orbit around it, you first need to throw an object across the globe so hard that its trajectory extends beyond the Earth’s horizons – so hard that it can be made to fall in such a way that it never again finds the ground.
And so to put an object into orbit around the Earth you have to provide it with an enormous amount of energy. In broad terms the faster you go the wider the radius of the orbit you achieve; to get a vehicle to achieve an orbit wide enough to get it to miss both the Earth and the upper layers of the atmosphere, to place you at the same altitude as the International Space Station some 250 miles above us, you need to travel at around 17,500mph.
That requires a vehicle propelled by engines and fuel tanks with the explosive capacity of a small nuclear weapon. This journey, from the surface of the Earth into low Earth orbit – aboard the Soyuz spacecraft – takes a little over eight minutes. And so the reason that the culture at Nasa, and space agencies across the world, is so firmly rooted in the demands of engineering rather than those of human biology is because in that brief but violent period there is almost nothing modern medicine can offer in the way of protection. During launch, either the engineering works and everyone lives, or it doesn’t and everyone perishes.
The preservation of human life throughout launch depends not upon medical procedures but on concentric layers of artificial protection that engineers design and build and swaddle the astronaut crews in.
The rocket engines must fire perfectly, delivering just the right thrust at just the right time, directed in precisely the right way. The tremendous force of that propulsion mustn’t be allowed to shake the vehicle, its systems or its fragile cargo of passengers apart. It is the job of engineering teams to make sure that the launcher and the vehicle are designed to perform in the face of forces that are trying to destroy them.
And perched atop that tower of kerosene and oxygen is a tiny capsule, with the volume of a handful of telephone boxes, and a couple of tonnes of supplies and three passengers crammed in among them. That capsule is a tiny bubble of life support, pinched off from the Earth and maintained artificially. Inside, still more machines provide a breathable atmosphere with enough pressure and warmth to support life in the void of space. If you survive the launch, your problems are really only just beginning.
International Space Station
It’s tempting to think of the International Space Station as a hi‑tech Big Brother house, floating high above the Earth. In some senses that is true: living conditions are harsh by any normal standard. There are few creature comforts and precious little privacy. It is a living arrangement bristling with the potential for huge social conflict. But remarkably that is largely avoided and in 15 years of operation there have been no evictions.
But the ISS is much more than an accommodation block. When crews go to live there they are taking up residence inside a machine upon which their lives depend every second of the day. They electrolyse water to produce oxygen, employ molecular sieves to scrub waste gases out of the air that they breathe, run heating systems from vast solar arrays that can pump out 80kW of power. That solar energy also drives four huge gyroscopes, which steady and steer the station, preventing it from tumbling out of control.
The International Space Station is far from tranquil: it hums and whines perpetually; fans are running all the time. Without gravity hot air doesn’t rise and cold air doesn’t sink. There is, as a consequence, no convection and without that it’s hard to get air to move or mix. That in turn causes problems, leaving astronauts prone to headaches in poorly ventilated areas, where exhaled carbon dioxide can build up. Hence the constant drum of motors churning air. The draughts on the ISS, like almost everything else that the crews depend upon for healthy living, are artificial. All of this effort just to maintain that bubble of life support in an outpost just 250 miles above our heads. The challenges involved are legion and we haven’t even started to talk about leaving low Earth orbit yet.
Back to the moon
There is unfinished business on the moon. It is nearly half a century since the Apollo programme landed a dozen men on its surface. And while it represents a treasure trove of scientific discovery, nobody has been back since. Low Earth orbit is 250 miles away and can be reached in minutes. The moon is about 250,000 miles away, takes days to get to and, in addition to isolation and the added complexity of the rocket science required, leaves crews extremely vulnerable to radiation. On Earth we’re protected from some types of radiation by the thick blanket of atmosphere above, which absorbs gamma rays, x-rays and ultraviolet radiation that would otherwise be harmful. But there’s another layer of protection that also keeps us safe: Earth’s magnetic field.
The magnetosphere filters out a particularly harmful species of radiation, which comes in the form of charged, high-energy particles – atomic nuclei spat out as a by-product of thermonuclear reactions in stars including our own. This type of radiation is particularly harmful and, during solar flares, can increase in intensity by many thousands of times. Presently we have little in the way of effective protection from the radiation that comes with the worst solar flares.
Mars and beyond
In recent years the idea of putting human crews on the surface of something other than the moon or Mars has found its way into the strategy documents of the international space agencies. This mission is less science fiction than you might think. The European Space Agenecy’s Rosetta mission, which so spectacularly landed the Philae lander on the surface of a comet last year, showed us that we could find and intercept a tiny target hurtling through space hundreds of billions of miles away. This has given agencies confidence that their idea of landing a human crew on an asteroid might be realisable.
But for now it is Mars that lies at the edge of possibility, and surviving that journey presents a challenge on a different scale. With Mars, the problem is distance and time. To get to the red planet you have to traverse hundreds of millions of interplanetary miles; more than 1,000 times the distance Apollo crews travelled to the moon. With existing technology it would take between six and nine months to travel from Earth to Mars and the same again on the return leg.
That’s a lot of time spent without any gravitational load on your body. Weightlessness may look like fun, but like everything else, too much of it can be a bad thing. When physiologists first considered what effect the space environment might have on the human body, before anybody had even been into space, they correctly predicted that muscle and bone would waste. Those systems are sculpted by gravity and as anyone who has ever so much as looked at a gym knows, if you don’t use it you lose it. Because of this, crews aboard the International Space Station must subject themselves to a daily programme of resistive exercise to try and prevent some of that bone and muscle loss.
Weightlessness wreaks havoc with other systems. It upsets your senses of balance and co-ordination, making it more difficult for crew members to track moving targets, creating illusions of motion and, for the first few days of flight, generally making them feel pretty queasy. With the exception of the nausea, all of these problems tend to get worse the longer you spend weightless.
More recently, new – and potentially more worrying – problems have cropped up. For reasons that are not yet entirely clear the pressure in some astronauts’ brains appears to rise as a consequence of space flight, and this has been linked to alterations in their eyesight that sometimes persist for many years after their return to Earth. This phenomenon has only been noticed after long duration missions, which highlights the message: spending a lot of time in space isn’t great for your health.
But time also creates problems for life support systems. If you imagine the amount of food, water, oxygen and power a single person might consume in a mission set to last up to three years (if you include the surface stay), that demands quite a sizable larder. Now multiply that by a crew of four or six and it looks like you need an impossibly huge spacecraft just to keep you fed and watered.
And that does become impossible unless you are able to recycle and reuse everything you can. Already aboard the space station astronauts recycle most of their waste water, including their urine. They scrub carbon dioxide out of their exhaled air and rebreathe the remaining oxygen. You might be able to go further still, by growing crops hydroponically, as a source of food and a mechanism of removing carbon dioxide and renewing the oxygen supply. If you choose the right plants you might even recycle the nitrogen in human solid waste. Which of course is a scientific way of saying that maybe you could use your own poo to fertilise your life-supporting crops.
A system as sophisticated as that is extremely difficult to assemble, manage and maintain, and it’s likely to be a while before we see greenhouses flying through deep space. For now life support engineers will content themselves with finding ways to recycle more and more of the resources they can, and in so doing reducing the amount of payload that crews have to set aside for the things that keep them alive.
There is a simple lesson from all of this: space is hard. All frontier endeavours are. But there is plenty to celebrate here. Since the start of the 21st century there has been a permanent human presence in space. What started as a surrogate battlefield for nuclear war has become a multinational programme of science, exploration and collaboration. This is not the place to get into a discussion of why we should explore space at all. There are many benefits that derive from human space exploration but one is more important than all the rest. Human space exploration inspires children to study and pursue careers in science, technology and engineering. It does so by showing them that within the limits of human imagination anything might be possible. I know this because it inspired me and throughout the whole of my life has continued to hold my fascination.
It is an enormous honour to give the Royal Institution’s Christmas Lectures. And yes, the take-home message is that space is hard. But the real lesson for this year’s audience is that this has been my adventure and it can be yours too.
How to Survive in Space will be shown on BBC4 in three parts on 28, 29 and 30 December at 8pm. Find out more on the Royal Institution’s website and join the conversation on Twitter and Instagram by following @ri_science or searching for #xmaslectures
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