Quick Review: Mythbusters AT-ST Log Smash

So, did the Mythbusters get it right?

In broad strokes, yes.  As reader Vorus noted, my old 2002 page on the AT-ST log smash held up well compared to their scrutiny.

In short, they build a rig with telephone poles and hang logs beneath them, pulling them back and letting them smash a test vehicle and then a full-on (and nicely painted) armored truck of the sort you might expect to haul bank loot.

There were some great moments beyond the eminently television-friendly Kari's various attire, such as Grant Imahara describing "back of the envelope" calculations suggesting that the energy involved per log was going to be about a megajoule, followed by a quick flash of assorted scenes from the show of megajoule scale, like car crashes and so on.

The total for both logs of two megajoules falls in line nicely with the notations on my AT-ST log smash analysis page in which, as always, I heap the benefit of the doubt upon Star Wars and basically double the likely figures.   The Mythbusters team, unencumbered by claims of bias from a group of Star Wars fans bent on maximizing Star Wars technology at every turn, felt perfectly at liberty to simply follow the facts and not inflate the figures in favor of Star Wars.

But, there were also some oddities.

"Aren't you a little short for a chicken walker?" - The AT-ST height is given as 20 feet (a rather low figure given that the full-scale mock-up in the film was over 8 meters, or 26 feet), and for some reason they felt it necessary to then hang a Ford Econoline test vehicle at that height for smashification.   Not only was the altitude completely unnecessary, but it put undue stresses on their rig to move the logs about at that height.   Fortunately this was abandoned for final testing, otherwise they would've had to rebuild it. 

"Aren't you a little short for an Ewok log?" - Also, despite having a fake log of proper length to width ratio at the beginning of the episode, it is somehow decided that the logs in the film are about ten feet long and five feet wide, which makes them entirely too short.  In the scene below, for instance, the logs would not even extend all the way to the edge of the frame.

On my page I came out with 1.5 meters by nine meters, or about five feet in diameter and 30 feet long.  And, since their targets were quite a bit shorter than the AT-ST cab section, the five foot logs looked a bit monstrous.

"Aren't you a little short for a log nose?" - The logs themselves were unfinished, in the sense that they were straight or nearly-straight cuts and had no pointed/rounded tips.  In the first hit against the armored truck, this seemingly resulted in the left side (as viewed from the front) not actually penetrating the side of the vehicle since it hit the roofline broadside.

"Aren't you a little far back for a logsmash?" - The first strikes were against the flat sides of a van and then the flat side of an armored truck.   In the case of the truck the right side simply caved in, which makes sense given that there is likely very little actual vehicle structure back there.   The second hit, however, was aimed more forward, and literally tore the roof off of the vehicle and smashed the cabin.  There is likely a pillar just behind the driver's door, making that more of a fair test.   After all, armored trucks of that nature are mostly intended to be bulletproof rather than structurally strong.

Of course, comparing that to the actual AT-ST's structural failure is interesting, since the first hit, as noted, only poked a hole in the truck.  The general structure appeared to remain fairly intact.   Compare that to the logsmash itself, in which the AT-ST literally crumples.   I guess in an age of blasters, the notion of kinetic impact may seem altogether quite foreign.

"Aren't you a little hard for a log?   Wait, don't answer that."  - For some unexplained reason, eucalyptus logs were selected explicitly for their hardness.   Presumably this was intended to allow repeated strikes without fear of log failure . . . the rig, after all, would've been rather difficult to 'reload'.    Nevertheless, it seemed odd when watching initially.

This does bring me back to my page, however.   I did assorted calculation via forces and whatnot, but never really got into the actual pondering of hardness of the AT-ST hull.   Given the malleability against logs it would be nice to review that ancient page and see what I can come up with in that regard.   Presumably I dismissed it back then as relatively unimportant, given that I had already concluded that AT-STs were more or less bulletproof.

In any case, I'd say the Mythbusters team did a great and very entertaining job, and it was great fun to see things get smashed and have Grant Imahara generally confirm my old figures.

1 comment:

Vorus said...

My guess about the issue of using shorter logs was that shorter logs are easier to work with, and then they went with eucalyptus logs to make up for some of the missing mass.

I miss the older seasons when more time was spent on explaining the setup and rig, but oh well. It was still cool to see it recreated in real life, and I agree that they generally did a good job.

And it was great to see how well it lined up with your figures.