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Preparing for Skylab: The separate 1972 experimental mission that never left the ground
Bags of splashy fun for astronauts in SMEAT's simulation
Feature Remember Skylab? How about SMEAT? Fifty years ago, a trio of US astronauts took part in 56-day simulation of a Skylab mission that would prove critical to the success of the US's first crewed space station.
SMEAT (Skylab Medical Experiment Altitude Test) took place a year after Apollo 15 launched to the Moon. It was originally planned to consist of a 28-day mission and then a 56-day mission within a partial mock-up of Skylab sealed in a hypobaric chamber at NASA's Manned Spaceflight Center in Houston.
The problem faced by NASA was that the Skylab mission was chock-full of unknowns, even when compared to the ongoing Apollo program. It had simply not tried such a long duration mission before; would the hardware work as expected? Would the crew remain healthy for such a long time in a closed system? And so on.
While many unknowns would remain until Skylab actually launched, a number of variables could be ruled out by simulating a mission on the ground, including performing experiments, evaluating procedures and, importantly, gathering baseline medical experiment data.
Skylab had two levels but only one was configured in the chamber for SMEAT; there was no need for inflight storage. Engineers otherwise strove to make things as close to the Skylab experience as was reasonably possible. The layout of the main chamber was pretty much identical, with partitioned waste management and wardrobe compartments, as on Skylab. There was simulated lighting and hardware to match Skylab's. Food was pretty much the same as what would be consumed on orbit and clothing was as close to flight standard as possible.
During the planning process, the 28-day mission was ditched. Astronauts Karol J "Bo" Bobko, Dr William E Thornton, and Robert L Crippen were selected (no backups were deemed necessary) and SMEAT got underway on July 26, 1972.
The crew had already trained within the chamber, although once sealed within noted that the 5-psi atmosphere of the simulation resulted in softer sound and slightly sore throats through having to shout to be heard. A simulated Skylab shower was available for use once a week and waste products collected via Skylab systems.
In his book Skylab: America's Space Station David J Shayler described the urine collection system: "Only one of the crew was required to use this system to evaluate it for flights, which was quite fortunate since it often broke down or leaked. This resulted in lost data and a rather messy clean-up period."
The other two crew members collected urine in covered cans, passed out through the transfer lock.
As well as checking out the habitability of what would become Skylab, the SMEAT crew were also to work on the medical experiments planned for the outpost and generate baseline data. By all accounts, these tests were a great success, both in highlighting what did and didn't work well and giving controllers a better idea of timelines. There were issues with fastenings and harnesses for some experiments, but all fed into redesigns for the orbital missions.
However, urine issues persisted. Shayler notes in his book that the four-pint (1.8 liter) collection bags were too small (one member of the crew exceeded six pints) and occasionally the bags tore, resulting in some unpleasant splashing onto the floor and the participating crew member. It's just as well they did: while nasty on the ground, a floating ball of urine would be far more hazardous on orbit.
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The problem was solved by eight-pint bags with either a centrifuge collection system or the Apollo-style roll-on cuff.
The crew's psychological state was also carefully monitored, and frustrations with "ground" personnel noted. A certain amount of horseplay occurred, and Shayler wrote of a practical joke planned (but not executed) by the crew involving the collection of lint to create what appeared to be hairballs and some smuggled chicken bones to convince test conductors that a cat was somehow onboard.
The joke never happened and, as it transpired, the crew worried that they would run out of time to meet all the test objectives. However, Shayler again: "The crew never felt despondent as they set out to do a good job for 56 days, and that is exactly what they did."
SMEAT was a critical and now mostly forgotten part of the Skylab mission. It proved the Skylab environment was habitable and was crucial in fixing both procedures and hardware before the orbital missions began. ®
It is easy to tumble into a SMEAT-shaped clickhole online, although we would strongly recommend both David J Shayler's Skylab: America's Space Station and Homesteading Space: The Skylab Story by David Hitt, Owen Garriott, and Joe Kerwin. ®