A while back we told you the story of the WWII submarine that was lost due to a malfunctioning toilet. It turns out that a similar incident threatened the space shuttle Discovery in 1989…
TOP SECRET
On November 22, 1989, the space shuttle Discovery blasted off from the launchpad at Kennedy Space Center in Florida for a five-day secret mission in Earth orbit.
It is believed to have deployed a spy satellite for the Department of Defense, but since the mission was (and still is) classified, only the United States government knows for sure.But some details of the mission have emerged, and they involve something a little more down-to-earth: the space shuttle’s toilet, or Waste Collection System (WCS), as it was more properly known. The $30 million device looked like an ordinary toilet, but because it was designed to operate in zero gravity, the experience of using it was quite different from using a toilet on Earth. The WCS toilet was equipped with a seat belt and stirrups that allowed shuttle astronauts to anchor themselves in place, so that they didn’t float away in the middle of doing their business. And instead of a flush handle, the toilet was operated with a lever similar to an automobile stick shift.
SHIFTY BEHAVIOR
- When astronauts needed to answer the call of nature, after first securing themselves to the toilet with the seat belt and stirrups, they shifted the toilet lever once, closing a valve on the outer hull called the overboard vent valve that was normally open to the vacuum of space.
- Once the valve was closed, a second shift of the lever opened an inner valve called the slider valve or toilet gate valve at the bottom of the toilet bowl. The toilet was now “open for business”; urine could be deposited into a funnel attached to a vacuum hose (male- and female-shaped funnels were available), and solid waste could be deposited into the toilet bowl.
- To help the solid waste get to the bottom of the bowl, a third shift of the toilet lever activated a fan that used airflow to blow the waste through the toilet gate valve into an interior holding compartment of the toilet.
- After the waste had floated into the inner compartment, shifting the toilet gear in the reverse direction turned off the fan.
- A second reverse shift closed the toilet gate valve, securing the solid waste in the toilet’s interior compartment.
- A final reverse shift opened the overboard vent valve, exposing the inner compartment and the solid waste therein to the vacuum of outer space. Doing so freeze-dried the waste, killing bacteria and helping control odors. The waste itself remained trapped inside the holding compartment, because ejecting into space would have turned it into a projectile hurtling through space at more than 17,000 miles per hour.
HAPPY THANKSGIVING
That was how the toilet was supposed to work, and that was how it usually did work. But that wasn’t how it worked early in the morning of November 23, 1989, Thanksgiving Day, when mission commander Frederick D. Gregory woke up early and had to go to the bathroom. Everything went well until he finished up and reverse-shifted to close the toilet gate valve. Gregory didn’t realize it, but the valve had failed to close. (He was still strapped to the toilet, and from that position he would have had trouble determining whether the valve was open or closed.)
When Gregory reverse-shifted again, the overboard vent valve opened. Now both the toilet gate valve and the overboard valve were open at the same time, exposing the interior of the space shuttle to the vacuum of outer space. That was a big problem: the air inside the shuttle cabin was now rushing down the toilet and out into space. If it were not stopped, the shuttle could depressurize completely, killing all of the astronauts on board.
POT LUCK
It didn’t take Gregory long to realize that something had gone terribly wrong. As if the air rushing between his legs and down the toilet were not enough of a clue, the sudden drop in air pressure triggered a shrieking alarm that woke up the rest of the crew—just the kind of thing you don’t want to happen when your pants are down and you are strapped to a space toilet in zero gravity.
The dropping air pressure also activated an automatic system that replaces escaping air by releasing oxygen and nitrogen from storage tanks in the shuttle’s payload bay. Because the payload bay itself is open to the vacuum of space, the tanks were very cold and the oxygen and nitrogen they contained was in liquid form. Before the contents of the tanks can enter the shuttle, it is heated to become a gas…but only just—the gas is still very cold. And if Fred Gregory needed reminding, he soon discovered that the oxygen and nitrogen are fed into the space shuttle’s interior through vents located directly above the toilet. So in addition to feeling the air roaring through his legs and hearing the alarm screaming in his ears, he was also deluged by very cold oxygen and nitrogen gas being dumped on his head.
TO THE RESCUE
Mission Specialist Story Musgrave was the first crew member on the scene; he floated over to Gregory and together they managed to wrestle the toilet gate valve closed, stopping the leak. Then…
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