|Posted on Nov 24, 2009 08:44:29 AM | Wayne Hale | 5 Comments ||
The shuttle is in flight once again this Thanksgiving Day, not the first time a holiday has come during a shuttle flight. My station friends remind me that they fly 24/7/365 and Christmas is really just GMT day 359. But when the shuttle is flying during Thanksgiving, I am always reminded of one significant day:
STS-33 was one of those classified DoD shuttle flights we can’t really talk about. But I don’t think I’ll be in any trouble with security over this mostly true story. I was the Orbit 1 team Flight Director and the shift schedule called for my team to be on console about noon. We had a big family Thanksgiving meal early that year (a real challenge for my wife). Satiated with turkey, all the trimmings, and pie, I arrived at the MCC to start handover from the planning team lead by Rob Kelso. We were expecting a really quiet shift.
Falcon Flight gave me the big news before I even plugged my headset into the console: “Potty is broken!” Sigh. Flight Directors spent hundreds of hours studying the various systems: engines, fuel cells, navigation. Everybody’s least favorite system was not working. “If we don’t get it fixed, the crew will have to break out the Apollo bags” Rob continued. If you don’t know what an Apollo bag is, well . . . let’s just say that you really didn’t really want to know. It’s a big plastic bag with sticky substance on the lip which you apply to your . . . anatomy . . . to take care of your . . . business. Not glamorous.
Fixing the potty is not exactly the kind of problem you want to work on following a big meal.
So MC finished team handover, got a few sketchy details from the crew, and set to work to see how the “Waste Management Collection System” could be fixed.
It wasn’t until the post flight debriefings that we heard what really transpired onboard. Story Musgrave, raconteur extraordinaire, was an eyewitness. It seems that the victim of the WCS failure was the commander, Fred Gregory.
First, you must have a primer on how to go to the bathroom in space (every schoolboy’s favorite subject). The lack of gravity means that everyday earth based technology does not work. Early efforts were primitive (reference the discussion of the Apollo bags above). #1 might be easily taken care of, but #2 is a much bigger problem (Pardon me here, my vocabulary is influenced by the recent effort to get my grandchildren potty trained here on earth). Without gravity the . . . waste material . . . tends not be removed from the body. The shuttle potty deals with this mainly by airflow. A very small opening in the toilet (much smaller than earth based toilets) allows just the critical part of . . . your anatomy . . . to fit precisely over the hole. There is a famously closed circuit TV in the WCS trainer at JSC’s building 5 to help astronauts learn how to correctly position themselves. Flight Directors did not have to go through this little indignity during our training. In early WCS designs, there was a complicated mechanism down that hole called the “slinger/shredder” which was pretty descriptive of its intent. The astronaut office objected to having a high RPM mechanical device so close to . . . . their person . . . and tests showed that the “slinger/shredder” probably wouldn’t work well, so the design got changed early in the shuttle. Now the toilet just uses airflow to do what gravity does here on earth. One sits in the WCS compartment with your feet in stirrups and a lap belt to hold you down. Once correctly positioned, the victim uses a handle much like an automobile gear shift lever to start the mechanism. First pull on the lever closes the vacuum valve – all the odors in the quiescent potty are sucked out through the orbiter’s overboard vent system. Second pull on the lever opens the “slider valve” just under the seat and that means the toilet is open for . . . business. Next pull starts a small fan which circulates air to help with . . . removal. When you are done, reversing the gear shift lever first turns off the fan, then closes the slider valve, and finally opens the vacuum vent. In that order.
Some quirk of sadistic spacecraft design required that all the air coming into the space shuttle crew compartment comes in through the “roof” of the WCS compartment. Normally there is very little makeup air required, but when the pressure falls slightly due to the natural leakage of the crew compartment, makeup air flows in through automatic valve outlets. A sophisticated system automatically keeps track of whether the makeup gas should be oxygen or nitrogen, the desire being to maintain a sea level atmosphere composition and pressure. Since the crew breaths in oxygen (and the exhaled carbon dioxide is removed elsewhere), the makeup gas is usually oxygen. The cryogenic oxygen tanks in the payload bay feed both the fuel cells and breathing air. The liquid oxygen from the tanks must be warmed to become a gas, but it still comes out very cold in the WCS compartment.
So during crew sleep early Thanksgiving morning, Fred Gregory had to do what comes naturally. All was well until (as) he moved the gear shifter to close up the WCS. Story related what happened next with great relish. Unfortunately, somewhere in the mechanism, the slider valve failed to close - but the vacuum vent was opened up! Depressurization! You can imagine what it would be like to be strapped down, have the suction of pure space applied to . . . . your person . . . , have a rush of cold oxygen burst in over your head, and the depress Klaxon alarm going off simultaneously.
Story opened the WCS door and together they got the mechanism to close the slider valve, and then got Fred off the seat.
Of course the whole crew was awakened by this commotion and John Blaha, the pilot, was starting to work the emergency procedure for cabin leak.
The immediate danger passed, but Mission Control was now on the radio and wanted to know what happened. A much abbreviated narrative was received. Needless to say, not much sleep was had for the remainder of the crew sleep period. And the bathroom was definitely closed for maintenance.
On the ground, MCC called in the engineering team that designed and tested the WCS (remember, it’s a holiday and most folks were just then sitting down to the Big Meal!) We got a crew of techs to open up one of the WCS units on the ground. Meanwhile, the flight controllers studied systems schematics and flight rules. We all pondered how to make the thing work. The IFM (in-flight-maintenance) guys came to our rescue. By removing the cover from the front of the device and applying vise grip pliers to an appropriate lever, the potty could be used without depressurizing the cabin again.
Whew. Problem solved. That’s what MCC is there for.
Every Thanksgiving now, sometime after the pie and before the football game/nap, I chuckle as I remember that episode. And give thanks for 1 G and three toilets in my house.
A few days later, Fred Gregory tried to land the shuttle like he did the T-38 . . . but that is another story for another day . . . .
Tags : Thanksgiving, challenges, life support, waste management