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This is a static archive of the domnit.org blog,
which Lenny Domnitser wrote between 2006 and 2009.

Smash Lab, No

I caught an episode of Smash Lab, Discovery’s new science show, with 120% more violent titillation. I will now bitch about it.

The premise of the episode was to make soft aerated concrete highway medians. Aerated concrete is already used at the end of airport runways to stop overshooting planes. An Engineered Material Arresting System (EMAS) crumbles under the weight of a plane, which digs into the surface and stops. They wanted to use a similar material to prevent head-on-collisions and decrease impact. Sounds good.

They came up with 2 designs: to line a standard reinforced concrete barrier with aerated concrete, and to make an arrestor bed, a plane of aerated concrete similar to EMAS. Rather than discuss the merits of design, the 4 actors that conducted the experiments made a few handwavy, remarks along the lines of “we have to consider both mass and velocity; those together make kinetic energy”. It didn’t sound exactly scripted, more like they were given a list of facts to impart, like when sportscasters awkwardly read background info. It’s PowerPoint voice, rephrasing bullet points. The smashers split into teams of 2 based on superficial preferences and tried both designs. It’s not wrong to try it both ways, but there was no argument.

3 concrete densities were made, 15% air, 25% air, and 40% air. Team Barrier set up a standard highway barrier, lined it with equally thick walls of each concrete, and smashed a fresh taxi into each at the same speed and (unrealistic) angle. And that’s it. There was no control experiment. ROOAAAAR! USE FUCKING SCIENCE! The lighter concretes decreased the force of the impact, but only the heaviest kept the car from going over the barrier. The design was deemed a failure, without seeing what happens when a car hits a barrier without an aerated concrete wall.

Team Arrestor Bed only tested 1 concrete, which given that it’s a novel design, the other concretes were judged too hard or too brittle in the lab, and it’s obvious that a car won’t stop without an arrestor bed, is OK for an initial experiment. The 25%-air mama bear concrete was formed into a strip, with a small ramp leading up to it. The test failed, and it probably would have even if the ramp hadn’t caused the car to bounce in and out of the concrete.

I wasn’t too bothered by the lack of realism (most roads can’t fit arrestor beds, and those that can probably have ditches; and brittle concrete on a large road system is totally unmaintainable; compare to a sturdy, battle-scarred barrier), it was the lack of thought. Maybe I was expecting too much from a show called Smash Lab, but that “lab” part must be worth something. A proper arrestor bed is pretty complicated, but the only expert they had in was a stunt driver. I’d rather see 1 or 2 fewer crashes to make time for a quantitative test of compressive strength and a calculation of whether they could even possibly succeed.

If real science is too boring, just show me a montage of car crashes in front of Beethoven’s Ninth instead of this non-attempt at science.