What it felt like to be floating in a tin can

It is 40 years since Skylab was launched, bruised and broken, into orbit. True grit ensured it succeeded in paving the way to colonising space, writes Dan Clery.

Image of the Skylab space station taken by the first Skylab crew before departing for Earth on June 22, 1973

As they peered at their destination through the tiny window of the Apollo command module, NASA astronauts Charles Conrad, Paul Weitz and Joseph Kerwin came to the same conclusion. The brand new Skylab, NASA’s first ever space station, looked less like a high-tech high-altitude home of the future, and more like a battered, floating tin can. It looked, to be blunt, like a very bad place to die.

The space station had been built on Earth and hoisted into orbit in May 1973, strapped to the back of an unmanned Saturn V rocket. Within a minute of take-off, its meteoroid shield had ripped loose, destroying one of its two main solar arrays, and pinning the other to the wall. A secondary array deployed successfully and the astronauts could see it, looking like the sails of a windmill, but to all intents and purposes the $2.2 billion Next Step in America’s conquest of space hung high above the world, crippled, powerless and useless.

A heavy responsibility weighed on the men. It wasn’t just the huge cost and embarrassment of a failed space mission: their actions would determine the future of space travel.

Despite the success of the Apollo moon missions, no NASA astronaut had ever spent longer than two weeks in orbit. The agency needed to know whether this was possible and, if so, what sort of jobs they could do. Skylab was to be the trailblazer.

But perhaps it was not beyond repair. Despite the loss of its main arrays, the undamaged solar set provided just enough power to keep essential systems running. To complete their planned four-week mission, the astronauts would need to free the main array, but that was not their only problem: Skylab was turning into an oven.

The metal shield ripped off at launch had not just provided protection from a meteorite strike; it also sheltered the thin metal surface of the station from the Sun. Without it, inside temperatures could reach 77°C. To make it habitable, the crew would have to deploy a sun shield.

And, to add an extra frisson to an already challenging situation, there were the Russians to consider. This was the Seventies, the Cold War was at its height, and space was one of its main battlegrounds.

The US may have won the race to the moon but the Soviet Union beat it by two years in the race to produce the first orbiting space station.

The USSR’s Salyut-1 launched on April 19, 1971. However, it seemed jinxed from the start. The first crew failed to board because of a fault in the docking mechanism. The second got aboard and spent 23 productive days in orbit. Tragedy struck on the return journey, when a faulty valve resulted in all three cosmonauts suffocating.

They heard a stream of expletives. Using a three-metre hooked pole,
Weitz had tried to dislodge a strip of metal debris.

Salyut-1 was aborted after just 175 days in space, and crashed into the Pacific. A follow-up mission in July 1972 never reached orbit because the rocket failed at launch. And a month before Skylab’s launch, a third station made it into space but systems failed before a crew got there.

NASA was determined not to let Skylab suffer a similar fate. The astronauts had been forewarned and forearmed. After the station’s disastrous ascent, engineers worked non-stop to design tools that could be wielded by spacewalking astronauts to clear the shield debris. They also had to design a deployable sunshield. This was high-tech engineering without a safety net – and with nothing remotely like the computing power available today. The engineers modelled their sunshield on one of the oldest machines in history – the parasol.

Paul Weitz, Charles Conrad and Joseph Kerwin, left to right, at the Kennedy Space Center, Florida, as they prepare for the first manned missing to Skylab. – DVIDS/NASA

Arriving just 11 days after Skylab’s launch, Conrad, Weitz and Kerwin immediately got down to business. The first task was to free the trapped solar array, and get the station on to something approaching full power.

They donned spacesuits, and prepared for the spacewalk that was necessary if they were to repair the craft.

Conrad piloted the spacecraft close to the damaged array. Weitz opened the hatch and leant out. Kerwin crouched behind him and held on to his legs. Back on Earth, the ground controllers heard the radio go silent as Skylab passed out of range of a tracking station. When it burst into life they heard a stream of expletives. Using a three-metre hooked pole, Weitz had tried to dislodge a strip of metal debris.

“We ain’t going to do it with the tools we got,” Conrad reported to Houston. (That was the gist of it, anyway.)

The crew abandoned the attempt and set about their next task: docking the command module to the station. It took 10 nail-biting attempts. By this stage the trio had been working for 22 hours without a break. They opted to remain in the command module to sleep.

When they entered the station the next day, the temperature was above 50°C and the atmosphere dry as the desert. The astronauts could work inside for just tens of minutes at a time, before retreating to the relative cool of the airlock. The first job was to deploy the parasol. Piece by piece, they pushed its central pole through a 20-centimetre airlock. Once it was fully extended, they pulled on a cord and the arms unfolded, producing what looked like a huge golden beach umbrella. The parasol did the job. Over the next three days the temperature in the station dropped, levelling out at 26°C – hotter than they would have liked, but habitable.

The crew moved in and began working: carrying out medical experiments on themselves, taking images of the Sun, and training a variety of sensors on Earth. The small solar array barely sufficed. They constantly risked running out of power. It was clear that another attempt to free the damaged main solar panels had to be made.

On the 12th day, Conrad and Kerwin donned their suits once more. They managed to attach an eight-metre-long pole to the array’s winglike structure, where it functioned as a handrail. Grasping it, they floated out, hooked a rope on to help haul it open, and then cut away the restraining debris.

The pair pulled on the rope. At first nothing happened as a damper controlling the wing’s movement had frozen solid. Then, suddenly, the ice cracked and the structure whipped outwards, catapulting Conrad and Kerwin into space. Only their safety tethers saved them. But the mission had been accomplished. By the next day the wing had fully deployed and the station was awash with power.

At last, the crew could settle into their new home and get on with the serious business of science.

Skylab was cobbled together with parts left over from the Apollo program. Essentially it was two tin cans stuck together. The larger one, a “workshop” made from a Saturn rocket booster, was 14.6 metres long and 6.6 metres in diameter. The narrower one contained the airlock for spacewalks, and the docking station for the command module. Skylab paired with the module was as roomy as a three-bedroom house, but as tall as a 12-story building.

Owen Gariott asleep in the crew quarters on the second Skylab mission. – DVIDS/NASA

Despite its jerry-rigged beginnings, Skylab had a serious scientific goal. How long could astronauts live and work effectively in space? NASA’s previous missions, although brief, had revealed that significant changes took place in an astronaut’s physiology. Muscle tissue was lost and calcium leached from bones. Cardiovascular systems slowed because they did not have to work as hard. The volume of body fluids decreased and thus carried fewer red blood cells, electrolytes and hormones. Would this deterioration continue during longer spaceflights until it endangered health, or would it level out? Could physical exercise slow the decline?

The second manned mission's commander, Alan Bean, at work in the forward dome area of the workshop.

The Skylab astronauts were reluctant guinea pigs. The crew, struggling to get the damaged station working, failed to complete 30 minutes of daily exercise on a stationary bicycle, because they found it difficult to use in zero gravity. They abandoned the routine after a few days. By the second week the Earth-bound instructors agreed to let the crew decide when and how much they exercised. The astronauts eventually worked out a way to use the cycling machine, holding themselves in the seat by putting their hands on the ceiling.

For the second crew, which left Earth on July 28, 1973, health was a bigger concern. An hour after launch, pilot Jack Lousma felt nauseous. By evening all three crewmembers had fallen victim to “space motion sickness”. The medical team had little understanding of the condition or how to treat it. The symptoms resolved themselves by the third day.

The second team, like the first, spent most of their time making scientific observations – observing themselves, observing the Earth and observing the Sun. NASA wanted to know if it was worth the huge expense and danger of sending astronauts into space just to have a human operator carry out experiments that could be done remotely. Space agencies were already launching robotic satellites. Would their increasing sophistication make humans in space obsolete? The Skylab astronauts and ground staff were determined to show that not to be the case.

Jack Lousma, pilot of the second manned mission to Skylab, on a spackewalk on 6 August 1973. – DVIDS/NASA

Skylab’s biggest instrument was its solar telescope. The astronauts spent hours taking pictures of the Sun’s surface and atmosphere, at a variety of wavelengths. It’s easy to forget in this digital age that the telescope recorded images on old-fashioned 35mm film and the astronauts had to use it sparingly. When the film ran out, changing it entailed donning a spacesuit and heading outside.

It may have been a clunky operation but the imaging produced unique results. Space probes, free of Earth’s atmosphere, provided a wealth of new data on solar wind and the Sun’s magnetic field. But the sensors they could carry were very primitive. Charged Couple Devices, the highly sensitive photon detectors used today, were still in their infancy. Skylab’s instruments, on the other hand, could produce simultaneous images of the Sun’s surface and atmosphere at X-ray, ultraviolet and visible wavelengths because they had astronauts on hand to collect the films and bring them back to Earth.

Astronauts could direct the gaze of the telescope to catch fast-moving phenomena like solar flares as they happened. Astronomers wanted observations of a flare from its very beginning and to link it to events in the corona, the Sun’s outer atmosphere. Perhaps it would help explain the longstanding mystery of why the corona was so much hotter than the surface.

Ed Gibson, science-pilot of the third and final Skylab crew, which took off in November, 1973, became obsessed with catching a whole flare. On 20 January 1974, astronomers told him there were signs of a coming flare, but despite watching for most of that day and the next he got nothing. At 5pm he asked crew commander Jerry Carr for permission to continue observing for one more orbit, bribing him gently with some “butter cookies” when they got back home. (“Butter cookies”, it transpired, was the crew’s code for Scotch.) Gibson’s patience was rewarded when he caught a flare on the rise and recorded the whole 23-minute event.

Edward Gibson, science pilot for the third manned mission at the space station's telescope console. – DVIDS/NASA

Back home, analysis of the solar data identified entirely new phenomena, such as coronal mass ejections and coronal holes. At a conference in 1974 the results were declared the best that had ever been obtained. “Skylab has vindicated the use of man in space to perform scientific experimentation,” said Richard Tousey of the Naval Research Laboratory.

Skylab also had instruments to observe the Earth, but their advantage was not so clear-cut due to competition from NASA’s Landsat satellite, launched in 1972. Skylab had a wider variety of instruments, including microwave sensors, a multispectral scanner that covered 13 visible and infrared wavelengths, and a radar altimeter. But unlike the satellite, Skylab’s astronauts could only be intermittent observers, limiting the value of the data.

By the beginning of February 1974 the third and final Skylab crew were preparing to head home. The instructions for closing down the station spewed from the station teleprinter in a paper stream that measured 15 metres. It took days to gather together all the medical samples, experimental results and photographic films, and prepare the station for hibernation. It was likely to be a long sleep as NASA had no plans to return. Nevertheless, as the crew departed on 8 February they used the Apollo module’s thrusters to boost the station up to an orbit where it was hoped it would stay for up to eight years – just in case.

A solar flare captured by Skylab's telescope.

Did Skylab answer the questions it raised about astronauts’ health and the value of putting in people in space? Medical scientists studying the crews found that they recovered their pre-flight fitness a matter of weeks after returning to Earth. NASA concluded that spaceflights of at least nine months would be possible without any ill-effects.

As for spaceflights longer than that, the Soviet Union took the lead. Its teething problems laid the groundwork for a much-improved series of Salyut and Mir space stations, which quickly broke the endurance records set by the Skylab crews when, in 1987-88, Vladimir Titov and Musa Manarov spent a full year on Mir.

As for the value of sending people into space, the jury is still out. Despite astronomers’ enthusiasm for Skylab’s solar observations, the increasing sophistication of robotic satellites and electronic sensors soon made unmanned probes the obvious choice. A satellite never needs to sleep. True, it can’t do running repairs or make intelligent choices, but at a fraction of the cost, scientists are prepared to put up with such shortcomings.

The downside of putting people in space was only exacerbated by the problems with NASA’s next big project, the Space Shuttle, which was meant to make the maintenance of space stations a routine matter. The shuttle, which debuted in 1981, turned out to be much more expensive and less reliable than expected. And after the loss of life in the Challenger and Columbia accidents, NASA became much more careful about what it was used for.

The shuttle did launch many probes to distant planets as well as valuable scientific satellites, and also recaptured and repaired a few, such as the Hubble space telescope. Sometimes the shuttle flew with a laboratory in its cargo bay so scientists could carry out experiments in zero gravity for a couple of weeks. Long-term experiments by humans, however, were off the menu.

It was not until 2000, some 26 years after the third crew left Skylab, that a real successor opened for business. In collaboration with the Russian, European, Japanese and Canadian space agencies, NASA was building the International Space Station – one of the most expensive objects ever made.

Skylab had one last brush with fame at the end of the decade,

when its orbit started to decay.

Expedition 1, launched by a Soyuz rocket in November that year, brought the first crew: Russians Yuri Gidzenko and Sergei Krikalev, and American Bill Shepherd.

Many of the experiments carried out on the ISS would have been familiar to Skylab astronauts – but there are differences. Astronaut health is still a central area of research, particularly combating the effects of weightlessness during a longer mission (to Mars, for instance). The instruments for observing the Earth and Sun have been replaced by new ones, such as the Alpha Magnetic Spectrometer for detecting dark matter. Researchers now take advantage of microgravity to study how plants and animals develop (smething long-term space dwellers will need to know), and to manufacture defect-free materials such as ZBLAN, a heavy metal glass.

NASA claims the science done on the ISS cannot be replicated elswhere. But the ISS has many detractors who argue that the station’s $150 billion price tag could have been more usefully spent on something else.

Skylab had one last brush with fame at the end of the decade, when its orbit started to decay. The space station lacked thrusters to control when and where it could be brought down to Earth. The craft had some large lumps of metal that could survive re-entry and hit the ground with a potentially lethal impact.

NASA hatched a plan to send one of the early shuttle missions to Skylab to fit a booster pack. But delays to the shuttle program and the dying space station’s rapidly deteriorating orbit made that impossible. All controllers could do was change Skylab’s orientation to alter drag, hoping this would enable them, during the last orbit, to aim it towards an ocean.

That orbit began on 11 July 1979. Skylab followed a path that took it across southern Canada, down the east coast of the US, and then across the Atlantic, past South Africa and towards Australia. NASA controllers set the station tumbling – a tactic, they believed, that would bring it down in a patch of ocean 1300 kilometres southeast of Cape Town. But Skylab didn’t play ball. Rather than break up quickly, radar images continued to show a single blip. This helped maintain its momentum; the 70 tonne station travelled much further than expected.

At around 1 pm Washington time, residents of Western Australia were treated to a glittering firework display as Skylab entered the atmosphere. Pieces were found around the town of Esperance, about 700 km southeast of Perth. Before the re-entry, The San Francisco Examiner had offered $10,000 for the first piece of debris delivered to its offices. On July 13, Stan Thornton, a 17-year-old beer truck driver from Esperance, claimed the prize. The Shire of Esperance fined NASA $400 for littering.

It was an undignified end for America’s first space station, and memories of the mission soon faded. Forty years on, we can see the legacy of Skylab – and that of the Russian missions – in the six astronauts living and working in the International Space Station. Now that people are seriously talking about sending astronauts to Mars, the experience gained there will become enormously important. Who knows if we would be even thinking of such a long and dangerous venture if back in 1973 Charles Conrad, Paul Weitz and Joseph Kerwin hadn’t decided to open the hatch and tackle the battered tin can?

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Daniel Clery is a news editor with Science magazine and the author of A Piece of the Sun: the Quest for Fusion Energy.
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