Igloo Engineering

My alter-ego is a geophysicist because, somewhere along the line, I decided I didn’t want to be sitting at a desk all day.  I was under the impression that because geologists are outside all day, geophysicists must be, too.  There is some truth to that argument, but it turns out to not be applicable to the types of geophysics in which I am interested.

However, being a geophysicist has given me plenty of opportunity to hang out with geologists, and sometimes they have strange ideas.  On the other hand, it was actually another engineer with an interest in geology that gave me the strangest idea of all.  In fact, he offered me a beer if I could follow through on his idea.  (This is standard fare among geology folk, but I opted for a handmade milkshake from the local hole-in-the-wall burger joint near campus.)

This particular friend, along with several mutual friends, decided to spend a weekend camping…only they wanted to do it in an igloo.  They had an Icebox igloo maker.  (No, I’m not getting kickbacks from the company.)  My friends did a practice run in a park one weekend.  Then they attempted construction of the full igloo with the intention of camping in it.  Sadly, they were unable to finish it, leaving them to snow camp in an incomplete shelter.

A big part of the problem with building igloos is that, unless you happen to have a boatload of fairly dense snow in the immediate area, you have to increase the area from which you’re gathering snow.  As you do this, it increases the amount of time to set each individual block.  You also have to take into account fatigue.  Building igloos is fairly difficult work.

After this experience, the friend wanted me to write a program to see if I could calculate how long it would take to build a complete igloo.

(Photo by Nicholas Seaton.)

The igloo maker is basically a box on a stick.  One end of the stick is tacked to the ground.  There is an articulating joint so that you can move the stick in essentially any direction.  The box is filled with snow, to make a block, and then shifted to the next position.  This is repeated over and over.  At the beginning, you’re also supposed to build a ramp, so the bottom edge flows continuously from one row to the next.  In essence, you’re making a helix that’s tapering.  The actual shape is a catenary.

While I started out with idea of recreating this shape, I realized I was only getting one milkshake out of the deal, so I quickly opted to make some simplifying assumptions.  Rather than using a helix-type parameterization, I opted to model five rows of simple blocks.  I calculated the number of blocks for each row.  Then I assumed a starting quantity for how long it would take to make a block, and increased the amount of time for each subsequent block by a fixed amount.  I could alter both of these values to get a better estimate.

I wrote the program this way and came up with some pretty plots.  However, I realized I had very little validation of the algorithm.  Yes, I knew approximately how long it took, in total, to build the first five rows.  However, I would prefer some more specific data.  My plan is therefore to join another trip as an observer and take careful records to determine how long it really does take to make each block.  And, as an observer, I can’t participate myself in building the igloo because that, of course, will alter the results.