Friday, February 13, 2009

Should an Astronaut Keep a Pistol for Propulsion

I was trying to find some group matrix ranking and estimation stuff I found one time in graduate school. I remember working on this project that led to the discovery. It was sort of a group assignment and I had done similar things 4 or 5 times throughout my education. So, I started searching for the documentation and ran across several examples.

The one I did in graduate school was something about some NASA astronauts were stranded on the moon and they had 25 things. We were to individually rank the items and then rank them as a group so that we could see whether our individual rankings or our group rankings were more similar to the expert rankings. The experts, of course, were NASA astronauts.

Today, I found another example about surviving in the Canadian wilderness. In this case, the expert was a US Army Survival School instructor.

In both cases, there is "a loaded .45 caliber handgun."

Now, here's my beef (there must be a beef . . . otherwise, what would I be blogging about?). I don't believe that the people who identified the "gold standard" rankings were actually experts. I think they're somewhat clever, but not NASA astronauts and not US Army survival instructors. In fairness, I don't believe that the official versions of these tasks make the claim that there were ever any experts involved, but most versions offer some fictitious evaluator to give clout to the "correct" answers.

So, here's why I doubt the expert claims. I don't believe that a US Army survival instructor would list a pistol as the 9th out of 12 items in terms of importance and certainly not because "although a pistol could be used in hunting, it would take an expert marksman to kill an animal with it. Then the animal would have to be transported to the crash site, which could prove difficult to impossible depending on its size."

Let's keep in mind that an army survival instructor has probably gone through at least the S part of S.E.R.E. During this training, they learn to kill animals with sticks and rocks. To be sure, if you can club a critter with a stick, you can shoot the little guy and eat him there or at camp.

Second, I doubt the army instructor would agree that "the pistol also has some serious disadvantages. Anger, frustration, impatience, irritability, and lapses of rationality may increase as the group awaits rescue. The availability of a lethal weapon is a danger to the group under these conditions."

I mean, here's a guy who has probably spent a fair amount of time in really crappy situations with a bunch of people who had a bunch of guns. If someone is going to flip his lid and start killin' folks, he's not really going to need the pistol to do so. Just bring it.

Of course, I disagree with a lot of the valuation assessments on most of the items, but I'm harping on the pistol thing for a good reason. Not because I like guns and not because I'm a proud gun toting American, but because I was really irritated when I ranked a pistol among the least important things in space but my group chastised me when they ranked it in the top 5!

Now, first of all, I realize that a gun can be fired in space, but I also realize that there's a low probability of having a target at which to fire the gun. The reason my group (and NASA . . . purportedly) wanted to keep the gun around was as a means of propulsion. After finding this again today, I've done a little math. I'll admit that my physics is a little rusty these days, I'm pretty sure that the numbers are pretty close.

So, pretty much the biggest bullet I could find for a .45 was 230 grain. It'll leave a Glock at 880 ft/s. 1 grain = 1/7000 lbs. Momentum = mass * velocity. Thus, the momentum of the bullet leaving the gun shot by a guy standing on the moon would be 28.9 pound foot per second. If a guy my size (180 lbs) was in a space suit (180 lbs according to NASA . . . no, really) that was designed for walking on the moon (the floating in space suit is much heavier), said guy would weigh 260 lbs carrying 2 lbs worth of gun for a total of 262 lbs.

According to Newton's third law of motion, the gun firing the bullet must exert equal force against the shooter (id est, 28.9 lb ft/s). If we divide that by the weight of the shooter and his junk, we get about .11 ft/s or 6.62 feet per minute or .0752 miles per hour. Any way you look at it, it'll take a long time to get around the moon with a handgun.

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