Apollo 13

I was, as is my wont, listening tonight to The Mike Malloy Show (M-F, 9p Eastern, GMT -5: checkitout!) and Mike mentioned how this evening marked the anniversary of the Apollo 13 explosion.  He asked, "Do you remember where you were that night?  If you do, you're old, you really are, because it was 40 years ago tonight!"


Thanks for that, Mike.  I do remember being 14, so I do remember the flight of Apollo 13.

It's one of my favorite stories, actually. I read an amazing book about it a few years ago and the number and the sequence of the seemingly unimportant minor little things that had to go wrong in just the right way in order that the Apollo 13 Service Module (SM) that exploded in space did in fact explode in space were mind-boggling.

Heck, the oxygen tank itself that blew up (North American Rockwell; serial number 10024X-TA0008, as every schoolboy knows) was mind-boggling in its own right.  As it was designed to hold liquid oxygen and for oxygen to liquefy it has to be really, really cold, engineers had to build a tank that was amazingly--what's the word I'm looking for, oh yeah, thermal--and what they came up with was a tank into which one could place an ice cube, seal it up, and it would take 24 years for that ice cube to melt.  I had 2 questions upon hearing this.  First, how big an ice cube are we talking about, and second, how do you know this, actually, without putting an ice cube in the thing and then waiting for 24 years to check on it?  But that's what they said.

It all got me thinking so I Googled tonight and came across the Apollo 13 Incident Report.

The whole disaster was set into motion when it was decided to take an oxygen tank which was to have been used on Apollo 10 and put it into Apollo 13 which meant the tank had to be moved from the Apollo 10 SM to the Apollo 13 SM and to do that, the Apollo 10 SM had to be taken off the storage rack to which it was bolted.  This, the removing of the SM from a storage rack, was not considered to be a very big deal at all and would not have been a big deal had it not been for the fact that it was only when they raised it with a fork-lift that they discovered that only 3 of the 4 bolts securing the SM to its storage rack had been undone.

And you know how they found this out, don't you?

The forklift operator--probably the lowest-paid guy in the plant next to the guy in charge of loosening the bolts before the forklift guy showed up--got resistance when he tried to lift the SM and, like any man would, merely applied more power to the lift rather than stopping to find out what was causing the resistance in the first place which as it turned out was of course the bolt still being bolted into place.  Said bolt, of course, finally snapped thanks to the forklift operator straining harder and harder on the lift which caused the SM to slam back down into its storage rack.  It wasn't much of a fall--only a couple of inches--and the unit was immediately inspected and no damage was discovered.

Investigators would later determine that this minor mishap several years before the actual flight may have caused something called an internal fill line in the oxygen tank to come ajar.

This, in and of itself, was not nearly enough to cause the accident though.

As we got better and better at space travel, we got better and better at building spacecraft and it was decided to upgrade the tank so that in addition to running off the 28-volt power system aboard Apollo 13, it would also run on the 65-volt system in use at launch pad 31-B at the Kennedy Space Center.  Why run the damn thing off the spacecraft's batteries and run them down pre-launch when you can just plug 'em in, right?  Any engineer would say, "Well, duh," to that.

Well, duh.

From the Incident Report:


All components were upgraded to accept 65 volts except the heater thermostatic switches, which were overlooked. These switches were designed to open and turn off the heater when the tank temperature reached 80 degrees F. (Normal temperatures in the tank were -300 to -100 F.)


That last note is important.  We talked about liquid oxygen being really cold.  It was never expected that the interior of the tank holding it would get anywhere near 80 F when it's supposed to be at -300 F.  Well, here's what happened a couple of days before the flight:

During pre-flight testing, tank no. 2 showed anomalies and would not empty correctly, possibly due to the damaged fill line. (On the ground, the tanks were emptied by forcing oxygen gas into the tank and forcing the liquid oxygen out, in space there was no need to empty the tanks.) The heaters in the tanks were normally used for very short periods to heat the interior slightly, increasing the pressure to keep the oxygen flowing. It was decided to use the heater to "boil off" the excess oxygen, requiring 8 hours of 65 volt DC power. This probably damaged the thermostatically controlled switches on the heater, designed for only 28 volts. It is believed the switches welded shut, allowing the temperature within the tank to rise to over 1000 degrees F. The gauges measuring the temperature inside the tank were designed to measure only to 80 F, so the extreme heating was not noticed. (My emphasis.)  The high temperature emptied the tank, but also resulted in serious damage to the teflon insulation on the electrical wires to the power fans within the tank. 


Why is that important?  If you saw the movie "Apollo 13" the explosion occurred when astronaut Jack Swigert (Kevin Bacon's character) flipped a switch to do what was called a "cryo (short for cryogenic) stir."  Fans in the oxygen tank had to be activated from time to time in flight to stir the liquid oxygen so that it would remain a liquid and not turn into an unusable slush.  The electical lines to those fans were the lines which had lost their teflon coating, exposing bare metal to the oxygen, resulting in an explosion when electricity was introduced. See 'ya, SM.  See 'ya, all of our oxygen.  That's what Jim Lovell saw venting into space: his oxygen supply.

It's amazing they survived.

So, there you have it.  A two-inch drop, a component overlooked, and Tom Hanks gets to make a movie we all enjoyed.

But there is one thing I remember first-hand from April, 1970.  All of us, and I mean all of us were watching every minute all the time to see how it was going to turn out.  So how would you forget that?