Why rocket science isn’t exactly rocket science, and other astronautical adventures.
What did space exploration ever do for us? What’s the point of spending all that money (and it is a lot of money) lofting people and objects off the planet? Shouldn’t we be sorting out our problems here on Earth before we start looking beyond it? These questions are often, and rightly, raised whenever space is in the news. But those expensive rockets are not shot into the skies for the fun of it. Many launches carry payloads that directly enrich our lives.
My apartment overlooks a local park. I can’t see many stars in the night sky, thanks to the urban glow of London. What I can see, out there in the dark, is a constellation of faint lights moving across the grass. A group of teenagers is prowling through the park in search of the digital monsters of Pokémon Go! They stop. Lambent oblongs are raised. A battle is joined. It’s a scenario played out in parks and streets around the world, and it’s all possible because of GPS*, the Global Positioning Satellite service.
GPS relies on a constellation of at least 24 satellites, which together allow a user to find their position anywhere on Earth. When the system was built during the 1970s and 1980s, it was intended as a navigational tool, first for the military and then for civilians. It has succeeded beyond measure. Satellite navigation is well on the way to replacing the traditional map.
Uses for GPS now extend way beyond navigation. Since the development of smartphones and third-party apps, the technology has percolated into many aspects of life. I doubt whether those who developed GPS could possibly have conceived that it would, one day, be used to hunt imaginary monsters in a moonlit park.
If catching Pokémon isn’t your thing, then you might instead have used GPS to seek a partner. Shakespeare portrayed Romeo and Juliet as star-crossed lovers. These days, people are finding cross-matched lovers thanks to artificial stars. Dating apps provide a summary of potential sweethearts, whom you might have passed on the street, or sat next to on the train – all reliant on GPS data. Some find this creepy, but one senses it is the beginning of something much bigger.
That is just to dip our toes in the water. We can swim out a little deeper, thanks to GPS-tagged sharks. The OCEARCH project has tagged dozens of great whites in this way. The feedback not only forewarns lifeguards about an incoming shark, but also allows scientists to learn much more about the behaviour of these creatures. Other applications include ‘geocache’ treasure hunts, the tracking of stolen goods and even performance art.
GPS is just one example of how space technology affects, and arguably improves, our everyday lives. Satellite TV is another, and accurate weather forecasting a third. Our orbital henchdroids have myriad other uses, such as helping farmers plan their crop rotations, prospecting for minerals, monitoring environmental changes, discovering the ruins of ancient cities, and spying on the enemy.
If a solar storm suddenly fried all the satellites orbiting our planet, chaos would ensue. Civilization might even collapse. Think of all the cargo ships, delivery trucks, emergency services, pilots and Pokémon Go players who rely on GPS. Many banking and payment services run data through satellites. There would be riots if the satellite dishes of the world were no longer able to receive the latest episode of Game of Thrones, or the Superbowl final.
Our modern world just wouldn’t be possible without satellites. And satellites wouldn’t have been possible without the billions of dollars and rubles spent on developing space programmes.
Spending money on satellite development, launch and operation has clearly helped to make the modern world. But what about space exploration? Can the costs of launching exploratory probes or humans into space be justified? The case can be argued persuasively either way, but I’m firmly in the ‘Hell, yes’ camp. Here’s why.
The romance of it all: I really shouldn’t start with this one. It is irrational. It is frivolous. It is subjective. Far better to begin with economic arguments, or the threat from asteroids, or the benefits to medical research. Most articles do just that, then finish off with appeals to our sense of wonder and curiosity. But no. That doesn’t seem right. If we’re being honest with ourselves, most space advocates want to explore simply because it is exciting to do so. And what is wrong with that?
When Apollo 11 landed on the Moon, the astronauts’ experience was shared with an estimated 600 million people back on Earth watching on TV. For the first time in history, one-sixth of our species united to witness the same event. The audience would have been still higher had TV sets been as widespread as they are today. These people did not tune in because they were interested in the composition of lunar soil, or to scope out investment opportunities. They did so because space exploration is thrilling.
The sense of wonder extends to our robotic probes. When NASA’s Curiosity rover landed on Mars in 2012, a lot of people took notice; 3.2 million viewers watched the livestream over the Internet – a huge number in 2012, and a larger audience than most cable news channels. Over a thousand braved the rain in New York’s Times Square to witness the event on a giant screen. The pictures were hardly eye-catching: all they got was footage of an anxious control room, as no imagery from the probe was immediately available. And all this for the fourth US rover to land on Mars – not an unprecedented event – and yet we were gripped.
There is something deep in the human psyche that urges us to tinker, to ask questions and to explore. It is our sense of curiosity that led us to harness powers beyond our own muscles: first firewood and yoked animals; later the sunlight and the energy locked up in the atom. Now we create and explore computer-generated worlds to satisfy that itch. Pushing out into space is not a ‘nice to have’ or an ‘optional extra’. It is an adventure that will forever call. We are driven to do it. As long as the human brain is what it is, there will be many who dream of the stars, and some will eventually get there.
When people say ‘What’s the point of exploring space?’ they’re asking a superfluous question. We might as well ask ‘What’s the point of art?’ or ‘What’s the point of having a baby?’. These are all questions that you could attempt to justify with facts and figures, but the honest answer is more human: because we want to.
Survival: And so we come on to the more rational justifications for space exploration. The first is one of survival. Sooner or later, Earth is going to be troubled by something big, and planet-wide. That might be an environmental disaster, an asteroid impact or a nuclear war. The only way to guard against such an ‘eggs in one basket’ scenario is to establish a human presence in places other than the Earth. The future of our species may rely on stable colonies on the Moon, Mars or elsewhere.
Let’s be honest, though. These will not come anytime soon. The most balmy, idyllic location on Mars is still far less hospitable than the wastes of Antarctica or the middle of the Sahara Desert. The first humans on the Red Planet will find a harsh realm with no oxygen and little atmospheric pressure. With no vegetation or liquid water, the scenery will soon become tedious and dispiriting. Establishing a successful colony may require us to alter the environment of Mars to suit human needs better (terraforming), or alter ourselves to suit the environment better (genetic engineering), or both. It may take many decades or centuries before an off-Earth colony is entirely self-sufficient, but we have to start somewhere. As space pioneer Elon Musk once described Mars, ‘It’s a fixer-upper of a planet, but we could make it work.’
In the shorter term, learning to live and work in space is crucial if we are to have any protection from major, extinction-event asteroid impacts. The dinosaurs lost out there and the same fate could easily befall us. A colossal strike may yet be millions of years in the future, or it might come in the next few decades. We just don’t know.
In the extreme long term, the Earth will be swallowed by the Sun. One day, our star will begin a new phase in which it swells to many times its current size. Our planet will grow steadily warmer, then bake to a crisp. Earth will then be swallowed entirely. We’re talking five billion years in the future, which I appreciate is quite a relaxed deadline, but it will happen. Our species – or whatever we’ve evolved into – will have to be more than competent with interstellar travel by this point, or face extinction. It pays to get your homework done early.
Science and innovation: By building craft that can leave the confines of Earth, and by learning to live in a weightless environment, humans have solved all kinds of problems we wouldn’t ever have encountered had we stayed on terra firma. A heap of new challenges has led to a tidy pile of inventions originally developed for astronauts and space probes that have since found purpose closer to home. NASA even has its own Technology Transfer Program, to help spin out its best research and development into the wider world. Space spin-offs include the foil blankets given to marathon runners, numerous types of health monitor, advances in robotics and miniaturized computing, improved artificial limbs and much more besides. NASA alone claims to have developed around 2,000 products from its research programmes. Contrary to popular belief, these do not include Teflon and Velcro, which were invented by others.
Meanwhile, the weightless environment is also useful for scientific and medical study. Much of this research looks ahead, to prepare the way for long-duration space missions to Mars or beyond. Some addresses more Earthly needs. Osteoporosis is one example. This common condition, most prevalent in elderly women, weakens bones and leads to fractures. As it happens, bone loss is also one of the side effects of life in microgravity. An astronaut on a long-duration mission will lose 1–2 per cent of their bone mass per month. The crew of the International Space Station (ISS) is therefore well placed to investigate early signs of bone loss, and ways to prevent it. About half the pressurized space on the ISS is given over to scientific research, in areas as diverse as crystal growth, muscle atrophy and the detection of antimatter.
Inspiration: No photographs can compare in importance with the images of Earth taken by the Apollo astronauts. They mark a fundamental stage in our development as a species. Trillions of creatures have lived their lives on the Earth; until the middle of the 20th century, not one had seen its home from the outside. Those shots of the delicate blue marble, hanging in the boundless black of space, still captivate after decades of familiarity. We went to the Moon, but we discovered the Earth.
Space exploration makes us think. What a precious, lonely rock we inhabit. Why is it here? Why are we here? How can we keep it safe? The Apollo images influenced poets, musicians and philosophers. Space exploration is a muse like no other. It drives creativity – from Avatar to Ziggy Stardust. How many scientific careers were launched alongside Apollo 11?
Profit: One of the main objections to space exploration is the amount of public money pumped into the cause. Yet study after study has shown that spending on space is a tremendous boost for the economy. For every dollar the US government gives to NASA, the treasury gets back something like $10 in new revenue and from licensing spin-off products. It pays for itself and then some. What’s more, spending on NASA represents only about 0.5 per cent of the federal budget (1 per cent if military space spending is included). It’s barely visible on the pie charts. China, the country with the next largest spend, only invests 0.36 per cent of its national budget in space.
The private sector, too, can make a tidy buck from space, and not just by fulfilling government contracts. Many satellites are launched privately, with little or no burden on taxpayers. Several companies are now focused on sending humans into space – a role traditionally played by the state. After all, the adrenaline rush of launch, the weightless conditions in orbit, the chance to see the curve of the Earth and the bragging rights of saying you’re an astronaut, are all very appealing. There is a strong demand, which could translate into profits for any company who can sort out the ‘supply’ side of the equation.
There are already precedents. Seven paying astronauts have travelled to the ISS aboard Russian Soyuz rockets, beginning with Dennis Tito in 2001. These out-of-this-world holiday packages were arranged by Space Adventures, a private company. Ticket prices were undisclosed, though a figure of $20 million has been reported.
A second wave of private space travel is now opening up its throttles. Companies such as SpaceX, Virgin Galactic and Blue Origin are developing their own craft that will take paying customers beyond the atmosphere. All hope to make money out of these endeavours, partly for profit’s sake and partly to help fund even more ambitious adventures to the Moon and beyond. At the time of writing, none has yet fielded a crewed vehicle, nor registered a comfortable profit. Nevertheless, momentum is building. This paragraph is likely to fall out of date quicker than any other section of the book.
Prospecting: Another opportunity for the private sector is space mining. Our celestial neighbours contain plenty of raw materials that are not readily available on Earth. Helium-3, for example, is present in far higher concentration on the Moon than on the Earth. This non-radioactive isotope could be used in fusion reactions to provide safer nuclear energy. Mining and transporting the element would not be a trivial task – technologically or economically – but the rewards make it an attractive target for space companies. Such efforts could be done robotically, but some kind of human presence would help with logistics. Similarly, rare elements used in the electronics industry may one day be mined on the Moon or asteroids when Earth’s diminishing bounty is exhausted.
Peace: The final and least-remembered mission of the Apollo era took place in July 1975, three years after the last Moon landing. In terms of technological leaps, it was trivial. Two spacecraft rendezvoused in low Earth orbit*. Politically, it was a monumental mission. The US Apollo capsule docked with a Soyuz spacecraft from the Soviet Union. After two decades of fierce rivalry, the Americans and Soviets were finally collaborating in orbit. It was the beginning of the end of the Space Race.
Space exploration, it hardly needs saying, is expensive. It makes lots of sense to team up, to pool resources. The Apollo–Soyuz test project was followed, albeit 20 years later, by a series of US space-shuttle dockings at the Russian Mir space station. This paved the way for the biggest feat of cosmic cooperation yet: the aforementioned International Space Station. The ISS brings together not only the old Space Race foes, but also 11 members of the European Space Agency, Canada and Japan. Russian cosmonauts and American astronauts still work up there together, despite a renewal of tensions between their two countries back on Earth. Indeed, since the retirement of the space shuttle in 2011, all US astronauts have relied on Russian rockets** to launch into space. International cooperation in orbit is unlikely to bring about world peace, but it does provide a model for us to look up to, in more ways than one.
To finish with an apposite quote from Apollo 14 astronaut Edgar Mitchell, ‘From out there on the Moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that, you son of a *!#!."’
* FOOTNOTE The Global Positioning System is the best known of several competing satellite clusters. GPS is owned by the US Government and operated by the United States Air Force and can be selectively turned off at their whim. It’s a little bit scary that so many people worldwide rely upon its information. Alternatives include the Russian GLONASS (Global Navigation Satellite System) and Europe’s Galileo satellites.
* FOOTNOTE This did, in fact, require some clever engineering. A special docking module, costing $100 million, was needed to allow the otherwise incompatible Apollo and Soyuz spacecraft to join together. One design requirement was that neither party should be seen to be the receptive partner in this mating – which just shows how touchy, some would say childish, Cold War diplomacy could be.
** In a curious quirk, the Russians don’t launch their crewed missions from Russia. The famous Baikonur Cosmodrome – which waved off Yuri Gagarin and all cosmonauts since – is actually in Kazakhstan, formerly part of the Soviet Union but now an independent country. At the time of writing, and for the best part of a decade, China is the only nation capable of putting humans into space from its own territory.
‘How do rockets operate in space?’ My father is fond of asking this. ‘I mean, there’s nothing for the flames to push off.’
I think he imagines that rockets fly by pushing down on the air, like a swimmer kicking off the wall of the pool, hence his bafflement over how a rocket can keep going even when there’s nothing to push off from.
It’s an easy and common mistake to make. Very few of us encounter rocket engines in everyday life. We can be forgiven for misunderstanding how they work. ‘It’s not rocket science,’ we say, when faced with a task that is straightforward compared to the daunting prospect of understanding how a rocket works.
But really, rockets aren’t all that complicated. The technology goes back as far as the 13th century, when the Chinese developed gunpowder rockets. The physics underlying a rocket’s flight path have been well understood since Isaac Newton laid down the laws of motion in 1686. Children learn these rules at school, and some even remember them.
Here, in simple terms, is how a rocket works. There are different types, but we’ll focus on a typical liquid-propellent rocket like the Saturn V or Falcon 9. Most of the rocket’s length and weight is taken up with fuel and oxidizer. The Saturn V’s first stage, for example, contained a mighty tank to hold its kerosene fuel, plus another tank for the liquid oxygen needed to burn that fuel. Beneath lies the rocket engine, which comes in two sections: a combustion chamber and an exhaust nozzle.
To start the engine, fuel and oxidizer are pumped into the combustion chamber. On ignition, an explosive ball of energy pushes outward in all directions, but can only escape downwards, through the exhaust nozzle. Now, remember Newton’s Third Law, which famously says that every action has an equal and opposite reaction. In this case, the action is blasting hot gas out of the nozzle. The reaction is a force upon the rocket the pushes in the opposite direction (i.e. up into the sky at the start of a launch). You can get a more intuitive feel for this by blowing up a balloon. When you release it from your hand, the balloon will whizz along for precisely the same reason. The gas goes one way, the balloon goes the other – equal and opposite reactions.
Notice how neither the ground nor the air are mentioned in these explanations. A rocket does not need these to operate. It does not push against anything. The rocket moves because it’s venting a high-pressure jet of gas, which is paired with a counterforce in the opposite direction. The principle works just as well in the vacuum of space as it does in the atmosphere – in fact, it works better in space because the rocket does not experience the drag of the atmosphere.
To reach a stable orbit, a rocket must burn enough fuel to achieve the colossal speed of around 28,000km/h (17,500mph). That’s roughly 8km (5 miles) every second! On the way, rockets typically shed their lower sections (called stages), or side boosters as fuel is spent. This reduces the mass of the rocket, helping it climb to orbit. Again, the principles were worked out long ago, by Russian theoretician Konstantin Tsiolkovsky in 1903.
That, if you’ll allow a pun, is the main thrust of rocket science. There is, of course, more to it. To launch a rocket into orbit, we’d need to work through the right angles and speeds, factor in air resistance, wind directions and fuel rate. But again, much of this relies on simple calculations. Bringing it all together is still a challenge, but it’s mostly one of engineering. The science behind the rocket’s propulsion is relatively straightforward.
Did you know that the first human artefact in space was a manhole cover? So says a wonderful and persistent urban myth. The metal plate in question was a 1-ton cap, placed above a nuclear test chamber in Nevada. Upon the bomb’s detonation, the cap was propelled over the hills and far away. Very far away. No one knows quite how fast it was travelling, but one technician guessed at six times Earth’s escape velocity. The nimble manhole cover must have entered space. All this happened in August 1957 – a few months before the launch of Sputnik 1 by the Soviet Union. The Americans had beaten the Russians into space after all, albeit with a glorified piece of street furniture.
There are several problems with this story. While it seems to be true that the metal cap was launched in this way, it is unlikely to have made it into space. Any object travelling at such enormous speeds is going to generate a lot of heat as it pushes the air out of the way. It’s like a spacecraft re-entry in reverse, but with the thicker, lower layers of atmosphere to negotiate. The cap probably disintegrated. Even if it did make it, the plucky lid would not have been the first object to have reached space. That distinction belongs to the V-2 rockets launched by the Nazis in the 1940s.
The V-2 was the world’s first effective ballistic missile. Thousands were fired on London, Antwerp and other targets during the closing years of the Second World War. Each rocket would climb high above the Earth before slamming down onto a city below. Whole blocks could be destroyed with one weapon. Thousands of civilians were killed. Even more lost their lives in the labour camps used to produce these weapons.
Many of the V-2 launches reached the internationally agreed boundary of space (100km/just over 62 miles). The first to do so was probably launch MW 18014, which took off from the Baltic port of Peenemünde in north-east Germany on 20 June 1944. This rocket achieved a height of 176km (109 miles) before crashing back to Earth. In other words, the first human object in space was launched from German soil 13 years before the Sputnik mission. It didn’t go into orbit, and was laden with a payload of evil, so it tends to be forgotten in more heroic narratives of space exploration. But the unsavoury fact remains that the Nazis were the first to touch outer space.
Want to see a photo of the Earth from space that pre-dates Sputnik? Several are available online. After the war, the USA and Soviet Union built on the captured V-2 technology to kickstart their own space programs. One US launch on 24 October 1946 included a camera. The grainy black-and-white images were snapped at 105km (65¼miles) above the planet’s surface. The rocket then fell back to Earth. It was smashed to pieces, but the film survived in its steel casing. According to an eyewitness, ‘When they first projected [the photos] onto the screen, the scientists just went nuts.’
Despite this colourful history, you’ll still find it written that Sputnik was the first man-made object in space. I’ve even seen it in museums dedicated to spaceflight. To put it clearly once more, Sputnik was not the first human artefact in space, but it was the first to orbit the planet. The two achievements are very different, as we explore in a later section. Yes, it’s nitpicking to correct such language, and Sputnik was by any measure a milestone of human technology. The full story, though, is rich and interesting in its own right.
You have to feel for Laika. Hers is a classic rags-to-riches-to-flaming-ball-of-plasma tale from the dawn of the space age. The young dog was blasted into orbit to worldwide acclaim, but on a mission she would not, and could not survive.
This was a time when almost nothing was known about space travel. The launch of Sputnik 1 in October 1957 had shown that machinery could function in space, but could humans? The acceleration at take-off, the weightless conditions of orbit and the fiery descent back to Earth were all untested. Both the US and Soviet space programs recruited animals for experiments, of whom Laika would become the most famous.
The feisty mongrel had already shown a good deal of pluck, surviving as a stray on the harsh, cold streets of Moscow. She had all the right stuff for the emerging Soviet space program and was selected to ride the Sputnik 2 mission into orbit. Her training was pitiless. Laika was strapped into centrifuges, exposed to loud noises and fed on a diet of gel. When not enduring these trials, she was kept in a tiny cage to prepare her for the confined space capsule.
Laika launched on 3 November 1957. The Sputnik 2 craft settled into orbit and she became the first animal to circle the Earth. This was a major step towards putting a human into space and the flight caused a sensation. Laika became the most famous dog on the planet (or otherwise). Coming just a month after the unoccupied Sputnik 1, her mission was dubbed ‘Muttnik’ by the American press.
It was always going to be a one-way ticket. The Soviets had not yet developed heat-shield technology and there was no way to return Laika to Earth. She died of overheating just hours after entering space. Laika was the first animal to enter orbit, and the first there to perish. Her remains re-entered five months later, cremated in the atmosphere.
Although Laika was the first animal to circle the Earth, others had already dipped their paws and proboscises into space. We’re talking here, once again, about the significant distinction between briefly entering space, and achieving orbit. The first can be done on relatively basic rockets, while orbital flights need much more power. They must gain enough speed to avoid falling straight back to Earth. It’s the difference between paddling on a beach at Dover and swimming the English Channel.
The earliest recorded spacefarers, then, were not humans, or dogs, or any other creature lovable enough to bear a pet name. The first multicellular organism to leave the Earth was a fruit fly. A batch of the insects launched from the USA on 20 February 1947 – a decade before Laika. Their V-2 rocket climbed to 109km (67¾ miles), a little over the international boundary of space. Unlike Laika, the flies survived their epic adventure. Because sub-orbital flights do not achieve enough speed to require meaty heat shields, the capsule simply parachuted back to the ground with its buzzing cargo intact.
The first large animal in space followed a couple of years later. The pioneer here was a rhesus monkey known as Albert II (Albert I died of asphyxiation on an earlier, shorter flight). Albert II achieved a height of 134km (83¼ miles), again on a US-launched V-2 rocket. Sadly, the pioneering primate died on impact after a parachute failure.
Other monkeys, mice and insects soared into space in the late 1940s and early 1950s. The first dogs to gain their space wings were called Tsygan and Dezik. They launched from the Soviet Union on 22 July 1951. Again, this was only a short, sub-orbital flight and needed no serious heat shield. The dogs were recovered alive after parachuting back to Earth – the first large animals to make it home safely. At least a dozen canines would go on to experience space travel before Laika. She was the first to reach orbit, but not the first in space. Humans did not make it until Yuri Gagarin’s flight of 1961, by which time around ten other species, including frogs and rats, had beaten us to it.
Animals continued to play an important role in space exploration well into the 1960s. If you thought that the Apollo astronauts were the first Earthlings to circle the Moon, then think again. They were preceded by a miniature Noah’s Arc of a space probe called Zond 5, which looped around the Moon in 1968, a few months before Apollo 8. This Soviet craft contained wine flies, mealworms and a pair of bemused tortoises on the first ever deep-space mission to carry living creatures. Their capsule was successfully recovered*. The parable of the hare and the tortoise had received the ultimate vindication.
* FOOTNOTE Given the longevity of tortoises, it’s quite possible that one or both of these reptiles is still alive. Someone, somewhere in Russia, may have a pet that beat Neil and Buzz to the Moon by almost a year.
The one thing everybody knows about space is that it’s very floaty. An astronaut can move around without the constraints of gravity. Floors, ceilings and walls are all interchangeable. You could curl heavy weights with your little finger, or drag a fellow astronaut about with your teeth, were you so inclined. It looks like a lot of fun up there. The late 21st century will surely see a blossoming of ‘zero gravity’ sports, stunts and sexual adventures. Yet the very phrase ‘zero gravity’ is a misnomer. No human will ever experience the true absence of gravity.
Although astronauts on the International Space Station appear to float freely about their modules, they are in fact plummeting. Fast. Their bodies, and the space station itself, still feel the inexorable tug of Earth’s gravity, and they fall towards the planet at great speed. Happily, they keep missing. The spacecraft and its occupants are also travelling sideways at many thousands of kilometres per hour. Effectively, the space station is falling around the curve of the planet. This controlled freefall gives the impression that gravity isn’t there. The astronauts are weightless and do not press against the floor, walls or ceiling. A ride in a falling elevator would offer a similar effect, though short-lived and terrifying. But gravity there is, and plenty of it. If gravity were suddenly switched off, the space station would hurtle away from the Earth like a child flung from a roundabout.
Two caveats. The first is that the men and women on the space station are not as attracted to the Earth as those of us with our feet on the ground. As Isaac Newton explained in 1687, the tug of gravity drops off the further we move from a massive object like a planet*. Those in low-Earth orbit are only about 400km (249 miles) above the surface – or more pertinently 400km further from the centre of mass of the Earth. At that distance, gravity is around 90 per cent of that which we feel on the surface. It’s reduced, but not absent.
The second caveat is a contradiction to everything I’ve just said. The above arguments are Newtonian. That is, they depend upon the laws of motion and gravitation as laid out by Newton. If we instead consider an orbiting spacecraft using Einstein’s theory of general relativity, then we can make a case for an absence of gravity. According to the ‘equivalence principle’, an astronaut orbiting the Earth has no way of perceiving or detecting her spacecraft’s freefall without checking against distant references outside the spaceship. She might just as readily be adrift, far from any star or centre of mass. It is valid, in this sense, to speak of zero gravity.
You can argue it both ways. What you can’t say is that outer space is free of gravity. Newton and Einstein would have different ways of describing it, but both would agree that a planet’s gravitational influence extends way beyond its surface. We can never truly escape that invisible lure. Even if you could travel away from Earth in the fastest spaceship for centuries, you would still have a gravitational attraction to the home planet – albeit a very, very weak attraction. By the same interplanetary token, you would also feel an attraction to Mercury, Jupiter, the Sun, Proxima Centauri, Halley’s Comet and anything else with mass in the galaxy (and beyond).
* FOOTNOTE More precisely any two objects feel a gravitational attraction that is inversely proportional to the square of the distance between their centres – the so-called inverse-square law. In simpler terms, if you double your distance from Earth (distance = x 2), the pull of gravity will be four times weaker (distance squared = 2 x 2 = 4). If you triple your distance, the attraction is nine times weaker. And so on. The inverse-square law is worth remembering as it applies not just to gravity, but also to the intensity of light (and other radiation) from a point source – a useful tip for photographers. Learn one simple equation and understand many things.
The date 12 April 1961 is one that will forever be remembered in the history of our species. Hundreds of years from now, when other momentous events of the 20th century slip into the footnotes, the day that humans first entered space will stand proud. It is the moment that life on Earth crossed a new threshold, like the first creatures to venture out of the oceans onto land. Even gods fade into obscurity with the passing of millennia. Surely, Yuri Gagarin will not.
The historic journey of Vostok 1 came just 58 years after the Wright brothers made the first powered flight near Kitty Hawk, North Carolina. The spacecraft lifted off from the Baikonur Cosmodrome in the Soviet Union. Yuri Gagarin journeyed 327km (203 miles) from the Earth, well beyond the boundary of space.
Gagarin became the first human to leave our planet’s atmosphere. But the debutant spaceman was almost robbed on a technicality. The Fédération Aéronautique Internationale (FAI), who oversaw and adjudicated flight records, had previously stipulated that a pilot must land with his spacecraft for the journey to count as a space flight. Gagarin did not land with his capsule. The Soviets had not yet developed a reliable landing system, and so the first cosmonaut was ejected from his returning vessel. Gagarin completed the final 7km (4⅓ miles) of his journey on a separate parachute to the Vostok capsule.
By any reasonable criteria, Gagarin had made it into space. To punish him for bailing out on the way down is like disqualifying a marathon runner for completing the last few metres barefoot. But rules are rules and the Soviets weren’t taking any chances. They withheld information about the landing to make it look like pilot and capsule had remained together. The omission was later admitted, by which time the FAI was happy to retrospectively change the rules. Gagarin was never going to lose his tag as the first human in space.
But was he the first? Momentous events always generate conspiracy theories. Gagarin’s flight was no exception. Rumours circulated, almost immediately, that others had launched before him, only to burn up on re-entry or meet some other tragic fate. Those deaths, so it was said, had been hidden by the Soviets to save face. Test pilot Vladimir Ilyushin is sometimes named as one of these cover-up cosmonauts. He narrowly survived a car crash just days before Gagarin’s flight. Conspiracy theorists allege that his injuries were instead received on a botched spaceflight that left him in a PR-unfriendly coma. Two Italian brothers, Achille and Giovanni Judica-Cordiglia, even claimed to have recorded radio communications from secret, pre-Gagarin missions.
Such claims are unlikely. For starters, Yuri Gagarin’s flight was announced to the world while he was still in space. Any number of horrors might yet have awaited the cosmonaut. If previous flights had failed at this stage only to be hushed up, why wasn’t Gagarin’s mission kept secret until he’d landed safely? And if those secret missions had been detected by radio enthusiasts in Italy, how come NASA or some other American agency failed to listen in? A recording of a Soviet mishap would have been a coup to the Americans during the Space Race. If there were spacemen before Yuri Gagarin, we would have heard about them.
Here’s an experiment I’m sure you’ve tried. Launch yourself through the air into a swimming pool and land belly first. What happens? The smack of the water kicks up a splash and gives your stomach a painful slap. You moved from an area of low density to one of high density at speed. The sudden clash of matter causes something of a shock – it’s not an experiment most of us repeat too often.
A spaceship returning to Earth finds itself in an analogous situation. One minute it’s in the near-vacuum of space, then next it’s screeching into the upper regions of the atmosphere at astounding speed. Without some kind of protection, its hypersonic bellyflop would be disastrous. This is where heat shields come in.
It would be natural to think that the danger here is friction. After all, the spaceship is typically moving at 27,000–40,000km/h (17,000–25,000mph) when it hits the upper atmosphere. At speeds like this, even tenuous gas is dangerous. The heat of friction when billions of molecules collide with the incoming spacecraft is sufficient to melt steel. Hence the reason why capsules and shuttles need some kind of thermal reinforcement to protect them.
That’s not quite how it works, though. The heat is mostly caused by compression, not friction. A crewed spacecraft always re-enters with its widest part first. With Apollo or Soyuz capsules, for example, it is the broad side of a bell shape, while space shuttles descend belly-first rather than pointing nose-down. This is deliberate. The punch of the atmosphere slows down the craft from orbital velocities to something that can land on a runway or with parachutes. But it also kicks up heat.
As it hurtles through the atmosphere, the spacecraft’s flat side compresses the gases directly in front of it. The air is hit at such speed that it hasn’t time to move aside and instead piles up in front of the vehicle. Gases under compression heat up. Remember how your bike pump warms up if you put your thumb over the aperture and push in the handle? This bubble of superheated air does not directly touch the vehicle. A shockwave separates the two. The heat is instead transferred by radiation. Without the shield, this heat transfer would burn up the vehicle, but friction would play little part.
Incidentally, orbiting spacecraft don’t have to re-enter the atmosphere at hypersonic speeds. An orbiting vehicle could alternatively fire a braking rocket to slow itself right down, and then gently pass through the upper atmosphere without the need for a heat shield. To do this would require a swift and powerful deceleration, essentially performing the launch sequence in reverse. Such a manoeuvre would need tonnes of additional rocket fuel. It’s far more practical to use the atmosphere to slow down, rather than building a much bigger rocket to carry the deceleration fuel.
Not all objects returning from space need chunky heat shields. Ballistic missiles, for example, can climb well above the internationally agreed boundary of space at 100km (just over 62 miles) – see the earlier section on V-2 rockets. Unlike crewed spacecraft, there is no desire to slow the vehicle down (unless you’re on the receiving end). Missiles are therefore streamlined to pass through the upper atmosphere as elegantly as possible. In addition, missiles do not travel nearly so fast as an orbital vehicle. They still need thermal protection, but not to the same degree as a crewed capsule or space shuttle.
The final crewed mission to the Moon took place in December 1972. The Apollo programme had been cut short, due to waning interest and budget. The remaining Saturn rockets – the towering vehicles that had lofted these missions – were used to launch the first US space station (Skylab), and for an orbital hook-up with a Soviet Soyuz vehicle. That last flight took place in July 1975. It would be almost six years before another American would fly in space. NASA was taking a break from launching to build something special: the space shuttle.
One of the many eye-watering costs of spaceflight is the hardware itself. Each Saturn V rocket sucked around $110 million from the budget. Adjusted for inflation, this is something like $720 million in today’s money. No part of the Saturn V rocket or crew capsule was reused on future missions. With such profligacy, spaceflight could never be routine.
The space shuttle – Saturn’s successor as the American crewed launch system – was supposed to change all that. Much of the hardware was designed for reuse. The two booster rockets could be recovered and refurbished. These parachuted back to an ocean landing after detaching from the rest of the stack. The winged orbiter itself could glide back to Earth and, after a thorough check-out, head off to another launch. Only the orange external fuel tank* was sacrificed. This remained attached to the orbiter for much longer than the solid rocket boosters, and burnt up after re-entering the atmosphere at great speed.
The space shuttle flew 135 missions between 1981 and 2011, all launched from Kennedy Space Centre in Florida. It was a revolutionary system in many ways. This was the first (and so far only) vehicle to carry more than three astronauts. The shuttle regularly accommodated seven crew, and once carried eight. It was the first to strap the crewed component onto the side of the fuel tank, rather than above it. And it was the first orbital vehicle to use wings for a runway landing. The space shuttle was a remarkable innovation, but not quite the icon of reusability that had been intended.
For starters, each mission took a heavy toll on the orbiter’s thermal protection system. This was another revolutionary aspect of the shuttle. Rather than a traditional heat shield, each orbiter carried a mosaic of ceramic tiles. Many were damaged in flight, and needed replacement post-mission. Then there was the sheer complexity of the shuttle. To make it safe for humans, every aspect had to be checked and rechecked after each landing. Several months of maintenance were necessary to return the vehicle to flight readiness. It was reusable, but only with some considerable replacement of parts.
To throw some stats at this, the space shuttle programme required some 9,000 employees to make each vehicle safe for relaunch. That clearly does not come cheap. The price tag for each launch varied depending on the complexity of the mission, and what you include in the costs. Most estimates quote about $500 million. It’s cheaper than a Saturn V launch (adjusting for inflation), but not by all that much. Plus, the Saturn could lift about five times the tonnage of the space shuttle. Far from a cheap, reliable way to orbit, the space shuttle turned out to be an expensive, occasionally disastrous transportation system. It could accomplish remarkable feats, such as rescuing the Hubble Space Telescope and supporting construction of the International Space Station. But nobody in retrospect could call it economical.
To end on a technicality, the shuttle wasn’t even the first space vehicle to achieve a form of reusability. That honour belongs to the X-15 rocket-powered aircraft, an experimental plane developed by the US Air Force. Between 1959 and 1968, the X-15 made 199 flights. Thirteen of these reached sufficient altitude to earn astronaut wings for their pilots. The program made use of only three X-15s, two of which crossed the boundary of space on more than one occasion. They were reusable space vehicles, a generation before the shuttle. That said, they only briefly crossed the boundary of space, whereas the space shuttle could stay in orbit for extended periods.
* FOOTNOTE The first two shuttle missions, in April and November 1981, looked a bit different from all subsequent launches. For these test flights, the main fuel tank was painted white for UV protection. This was soon deemed unnecessary and all future tanks were left unpainted in the familiar rust-orange colour. This saved time, cost and about 272kg (600lb) in launch weight – the equivalent of four unclad astronauts.
And so to a rather morbid topic. Space, it hardly needs saying, is a hostile environment. There’s no air, obviously. Temperatures can swing from 260ºC (500ºF) in the sunshine to as low as -100ºC (-148ºF) in the shade. There’s always the risk of collision. At a typical orbital speed of 28,000km/h (17,500mph), even a speck of metal could do serious damage if it hit the wrong spot. Sudden depressurization or a fault with the oxygen supply add further risk. In the event of a fire, you can’t simply run outside or open a window. It must be hard to relax up there.
For all the dangers, very few people have died in space. Most accidents have occurred during launch or re-entry. The Challenger accident of 28 January 1986 is perhaps the most famous spaceflight tragedy. A leaky booster rocket ruptured the main fuel tank causing the orbiter to break up 73 seconds into the flight. The tragedy occurred at just 15km (9⅓ miles) – well within the atmosphere, not in space.
The accident report included some bleak findings. The crew compartment survived the initial break-up*. It was thrown clear of the fireball and continued on a ballistic trajectory to a height of 20km (almost 12½ miles) before tumbling into the ocean. Had the crew survived the blast, only to be killed on impact with the water? It seems so. The wreckage was too mangled to say for sure, but it is likely that some of the astronauts were conscious during the free fall. They were killed at sea level, not in space.
NASA suffered the loss of a second space shuttle on 1 February 2003, when Columbia broke up during re-entry. Again, the tragedy took place within the Earth’s atmosphere and not in space. The orbiter fragmented after hot gasses penetrated a hole in the wing’s leading edge. This time, the cabin quickly lost pressure, sparing the crew a prolonged death.
The two shuttle accidents remain the worst disasters to befall spacecraft. Each claimed seven lives. But there are other terrible incidents in the history of spaceflight. The earliest to kill astronauts was the Apollo 1 accident of 27 January 1967. Gus Grissom, Roger Chaffee and Ed White died when a fire ripped through their capsule during a launchpad rehearsal.
The first fatality in flight occurred just months later, on 24 April 1967. This was the first crewed mission of the Soyuz, the Soviet spacecraft that – though much modified – remains the workhorse of the Russian space program half a century later. This debut mission suffered a string of problems, and the craft was ordered back to Earth early. Sadly, a final malfunction occurred after re-entry when the main parachute failed to open properly. The sole cosmonaut aboard, Vladimir Komarov, died upon impact with the ground. In the third space tragedy of that year, American pilot Michael J. Adams lost his life when his X-15 rocket plane broke up at excessive speed. This happened well within the atmosphere, but the craft had dipped over the US Air Force’s definition of the space barrier (80km/50 miles) before the accident.
Only three humans have died while actually in space. The fatal flight was the Soyuz 11 mission of 1971. Georgi Dobrovolski, Viktor Patsayev and Vladislav Volkov asphyxiated when their capsule depressurized while undocking from the Salyut 1 space station (the world’s first). Their bodies were recovered after Soyuz 11 made an automatic re-entry and landing.
In total, 19 astronauts have lost their lives in flight, but only three of these were in space. Numerous other lives have been lost during training and preparation for spaceflight, as happened on Apollo 1. Others have died in training-jet crashes and accidents back at base. The most recent (at time of writing) is Mike Alsbury, a pilot of the ill-fated VSS Enterprise. This private, suborbital spaceship was undergoing powered test flight 16km (10 miles) above the Mojave Desert, south-western USA, when the craft disintegrated. Remarkably, his co-pilot Peter Siebold survived.
Space exploration is not just dangerous to astronauts. In fact, most of those killed by rocket accidents were never destined for space. Explosions on or near the launchpad have claimed the lives of hundreds of workers over the years. Incidents from the former Soviet Union and China are still somewhat shrouded in obscurity. Perhaps the most horrific accident in spaceflight history occurred in Xichang, China on 15 February 1996. An unmanned Long March 3B rocket veered off course immediately after launch and crashed into a nearby village. The official death toll was just six, but other accounts estimate as many as 500 people lost their lives. It is quite probably the worst disaster in spaceflight history, but few have ever heard about it.
* FOOTNOTE Technically, the spacecraft was not destroyed by an explosion, as is often assumed. The ruptured tank caused the stack to break up under aerodynamic stress. It was wrenched apart. The flaming ball seen in the footage is the hydrogen fuel catching fire – effect, not cause of the break-up.
There’s a famous quip that goes like this.
During the 1960s, the Americans spent millions of dollars of taxpayer money designing a pen that could write in the weightlessness of space.
The Russians used pencils.
It has all the hallmarks of a good urban myth. It’s a plausible tale, with a good punchline, and it plays up to national stereotypes. The Americans strive for the best; weighted down by bureaucracy, they are oblivious to common sense. The Russians, meanwhile, are thrifty and resourceful. They get the job done with whatever works. The tale is indeed an urban myth, though one with some small basis in reality.
It’s true that normal ballpoint pens do not work well in space. They need gravity to function reliably. Try writing your next shopping list against a wall. The US space program did initially use pencils just like the Soviets, but spent more than would seem reasonable on mechanical versions. After an outcry at the cost, the agency sought alternatives. Businessman Paul C. Fischer had independently developed a ‘space pen’ that could write at any angle, with or without gravity, and even worked underwater. NASA commissioned a batch at $6 each, and began using them on Apollo missions from 1967. The Soviets were also impressed and ordered their own supplies. Neither agency spent a dollar or rouble of taxpayer money developing the technology.
In any case, pencils are a dangerous option in space. Nobody wants particles of graphite floating around a space capsule. Flakes and fine powder are a risk to health as well as electrical circuits. Pencil marks are also easily erased, and a poor substitute for pen ink in official documentation. The earliest space missions did use conventional pencils, but soon switched to the alternatives mentioned above, when the shortcomings became clear.
What would it feel like to float out of an airlock without a spacesuit? Would you explode? Would your eyes pop out? Would you die instantly? It’s a scenario often played out in science-fiction stories, to varying degrees of realism. The experience would be deeply traumatic certainly, but not immediately fatal.
Let’s imagine that, in the weightless equivalent of sleepwalking, you unlatch the airlock without putting on your spacesuit. The air rushes out, drawing you along. You wake to find yourself outside your spaceship in nothing more protective than your cotton pyjamas. How are you feeling?
Your body is facing several challenges all at the same time. The first is a lack of anything to breathe. There is oxygen in space, but you’ll be lucky to find one atom per cu. m (35⅓ cu. ft). Effectively, you’re in a vacuum, and your lungs are unable to take anything in. Temperature is also a problem. Space can be very, very cold in the shade; just a few degrees above absolute zero (-273ºC/-460ºF). Yet in a vacuum, there’s nothing for your body to transfer its heat to by convection or conduction. You will eventually freeze as your body heat escapes by radiation, but not instantaneously. Other problems, though probably less pressing to you at that moment, include strikes by micrometeorites and a high dose of radiation.
The biggest challenge of all is the lack of pressure. Normally, our bodies are in balance with the environment. In space, there is no pressure. It’s a vacuum. The outside of your body is at zero pressure while the inside is at its normal pressure (1 Atmosphere). The sudden differential takes your breath away – literally. The air rushes from your lungs faster than a sneeze. If you attempt to hold your breath, the air in your lungs will expand until the tissue ruptures. Don’t do it. Your bowel, too, makes its own rapid exhalation. Fortunately you can’t smell it.
The pressure drop has also affected the fluids of your body. Liquids boil more readily at low pressure. The fluids on or near the surface of your body are evaporating. Your saliva has vapourized and your eyes are drying out. Deeper fluids agitate less. Your blood will not boil. The circulatory system is robust and not directly exposed to the vacuum. It will maintain much of its pressure. As the other fluids of your body attempt to escape, though, your skin starts to balloon out. Again, this in itself shouldn’t be fatal. Your skin and connective tissue are strong enough to hold things together even here.
It’s all rather horrible, though you’ve been spared the worst of it by slipping into unconsciousness. The situation is recoverable so long as somebody retrieves you quickly. You might last for a minute out there without long-term problems, perhaps two. Did anybody notice you were sleepwalking …?
We do not know in detail how the body would withstand such an onslaught. No astronaut has worked up a sufficient spirit of derring-do to voluntarily float unprotected out of an airlock. That said, at least one man has been exposed to a near-vacuum and lived to tell the tale. Jim LeBlanc was a technician working on new spacesuit designs for NASA. In December 1966, he climbed into a vacuum chamber wearing a prototype moonsuit. Somehow, a pressurization hose pulled loose and the unfortunate test subject found himself bereft of atmosphere. He passed out within 15 seconds but was quickly rescued and suffered no long-term ill effects. His only adverse symptom was earache. The last thing he remembered was a fizzy sensation on his tongue. His spittle evaporated.
If we continue to explore space it is almost inevitable that, sooner or later, an astronaut will be exposed to the vacuum of space and will not be recovered*. What will happen to the body? The vacuum conditions would not only kill off the astronaut, but also any bacteria that might cause decomposition. The corpse would freeze but not rot. If the astronaut were lost in deep space, away from the gravity wells of planets and moons, he or she might float through the heavens for millennia, unravaged by the passage of time. It is the nearest we can get to immortality.
* FOOTNOTE Three cosmonauts aboard Soyuz 11 died in 1971 when their craft depressurized, but their bodies were returned to Earth on autopilot. See the section on space deaths for further discussion (see here).