Thanks to the seminal work of Howard and Hanks et al, the world is intimately familiar with the story behind perhaps the most epic hack of all time, the saving of the crippled Apollo 13 mission. But Apollo 13 is far from the only story of heroic space hacks. From the repairs to fix the blinded Hubble Space Telescope to the dodgy cooling system and other fixes on the International Space Station, both manned and unmanned spaceflight can be looked at as a series of hacks and repairs.
Long before the ISS, though, America’s first manned space station, Skylab, very nearly never came to fruition. Damaged during launch and crippled both electrically and thermally, the entire program was almost scrapped before the first crew ever arrived. This is the story of how Skylab came to be, how a team came together to fix a series of problems, and how Skylab went on to success despite having the deck stacked against her from the start.
Hacking a Space Station
When NASA was designing its manned space program in the 1960s, it knew it was going to need an encore should they succeed in meeting President Kennedy’s goal of landing a man on the moon by 1970. So even while Gemini and Apollo were still rehearsing the moves needed to get to the moon, the designs that would eventually fly to space as America’s first manned space station were being finalized.
Ideas for using the spent upper stages from launch vehicles as the basis of a space station dated back to at least the 1940s, when Wernher von Braun speculated about what would be needed to send a man to the moon during his Peenemunde days. Various iterations of the design floated about during the 60s, including a design which would have the entire living and working areas of the space station inside the active liquid hydrogen fuel tank of an upper stage rocket; after arrival in orbit, the excess hydrogen would be purged and the tank pressurized with an oxygen-nitrogen atmosphere.
The “wet workshop” design eventually lost out to the “dry workshop” idea, and fully fitted-out labs and habitats were built within an S-IVB stage, which normally served as the third stage of a full Saturn V stack. Christened Skylab, the space station provided laboratory and living space for three astronauts for missions of between one and three months. Equipped with a solar observatory and a docking adapter for the Apollo command-service module (CSM) on one end, Skylab’s missions were to study the Earth and the Sun, and to conduct space medicine and other microgravity experiments with the full laboratory inside.
A Mission in Trouble
On May 14, 1973, Skylab was launched as an unmanned mission. Mounted where the third stage of a Saturn V would normally go in the stack, and nestled in a payload shroud, Skylab was in trouble right from the start. Other than a lateral acceleration that was detected early on, Skylab’s 10 minute trip to orbit was uneventful. Once in orbit, the station began getting ready to accept its first crew, scheduled to lift off shortly after their home was aloft and operational. Skylab’s observatory and solar-panel windmill deployed correctly, but mission controllers soon began to see anomalies. Telemetry told them that the micrometeoroid shield hadn’t deployed, and that temperatures within the workshop were nearing dangerous levels. What’s more, Skylab’s power production was seriously below specifications.
As controllers pored through telemetry, a picture of what was going on 460 km overhead began to emerge. The lateral acceleration during launch was caused by a structural failure of the micrometeoroid shield, intended to protect the crew against penetration by space debris and to shade the workshop on the side that was always kept facing the sun. While it was tearing free, the shield ripped one of the two solar arrays mounted on the side of the workshop clean off, while simultaneously jamming the remaining array with debris that prevented it from deploying fully.
Skylab, intended to be a spectacular follow-up to the success of the Apollo program, was now in orbit but totally unusable.
The first step in saving Skylab was maneuvering the spacecraft to control the heat build up inside. Everything the first crew would need for a month in space – food, fuel, instruments, film – was slowly roasting at temperatures up to 77°C. Without a heat shield, the only option was to orient Skylab so that the smallest possible surface area was directly exposed to the sun. While that kept the temperatures reasonable, it burned precious attitude-control fuel, plus it kept the remaining solar arrays in the dark for much of the time, resulting in power problems. Still, the maneuvers successfully balanced power production and temperature control and bought enough time to start working the problem.
Eleven Days in May
It became clear that unless the first crew could rig a heat shield to replace the missing one, the entire $2.2 billion Skylab mission would end before it began. Secondary to that would be solving the problem of the partially deployed solar array, so that Skylab would have enough power to run all its scheduled scientific programs. Engineers and the flight crew, now on a launch delay and wearing surgical masks since they were still in quarantine, began working on both problems in parallel, in a marathon of brainstorming and design-build sessions that came to be known as “The Eleven Days in May.”
The heat shield problem seemed insurmountable without a spacewalk, but NASA was loathe to allow EVAs without proper ground rehearsal. Luckily, Skylab had been designed with a small airlock in the workshop to allow experiments in the vacuum of space. Luckier still, the airlock was located on the sunny side of the ship, and so was a natural port to exploit for a sun shade. Several design were batted about, but the winning design was basically a Mylar parasol with a collapsible shock-tube frame that would be deployed through the small airlock. The design was perfected with tests in the Skylab neutral buoyancy simulator and the final product shipped to the Cape for launch.
Solving the power problem would prove to be a little more on the hackish side. Telemetry indicated that the surviving array was jammed with debris, and a plan was hatched to conduct a “stand-up EVA” through the CSM hatch to clear the blockage. But tools would be needed, and nothing in NASA’s tool crib fit the bill. Looking for inspiration, engineers from Marshall Spaceflight Center raided a local hardware store and found a pole-mounted tree pruner. A flurry of calls to local manufacturers resulted in selecting a cable cutter and a prying tool from a company manufacturing tools for, ironically enough, the power industry. The tools were quickly modified, mounted to a collapsible 3 m pole, and shipped to the Cape.
A Bit of a Fixer-Upper
The crew of Skylab 2, Pete Conrad, Joseph Kerwin, and Paul Weitz, finally arrived at their home for the next month on May 25, 1973. They found the place pretty much as advertised, and after conducting a reconnaissance fly-around, they popped the hatch and got to work on the jammed array. Despite their efforts and the power amplifying effect of a steady stream of NSFW language over an open channel, the array remained stuck fast, so the crew gave up and docked with their new home.
The parasol was deployed through the airlock and the temperature quickly dropped. A later full EVA would get the stuck solar array deployed, and with this addition of 7 kW to the power budget paired with a now-reasonable temperature inside, Skylab was finally up and running.
Skylab eventually flew three crews of three men for a total of 171 mission days. Skylab 4, at 84 days in space, held the record for longest duration in space for years. While it was never intended to be a permanent station, the plan to have the new Space Shuttle visit the station and boost its orbit never came about, and after almost 35,000 orbits, Skylab finally returned to Earth over the Australian outback in July of 1979. It was a sad and ignoble end to a machine that had beaten the odds with the help of an umbrella and some hardware store items, and the dedication of a team that wouldn’t quit hacking until the problem was solved.
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[All images courtesy of NASA]