Water is critical to the existence of human life. Why do you think we spend so much time looking for it on other planets?
It is, however, less than desirable on a racetrack. Water gets between the tires and the track, which decreases friction. Decreased friction means lower speeds and higher probability of crashing.
Before you read any more, head over and read why it takes so long to dry racetracks.
OK. Welcome back.
The traditional way of removing water from a race track was to evaporate it using jet engines. Evaporation is the process of turning a liquid into a vapor. In the case of the jet dryer, this is done by heating the water until it evaporates. The exhaust from a jet engine is somewhere in the 1000 F -1300 F temperature range.
The problem is that evaporation is a slow procedure, even when abetted by jet engine temperatures. Only the molecules on the surface of the water can evaporate, so you have to evaporate the water layer by layer. This is why it takes a couple of hours to dry an intermediate-size track.
The new system (Air Titan) relies on a little different approach. The majority of the water will be blown off the track, leaving a thin residual layer that can then be evaporated by the jet dryers.
The leading edge of the system is a series of pickup trucks towing trailers and attached to another vehicle by giant hoses. The trailers contain the equipment that pushes the water off the track. There’s a really great picture of the water sheeting off in the New York Times article.
This is trickier to design than it sounds. Air has to be compressed to very high pressure, then blown onto the track in a controlled way. If you just blow air on the track, the water will spatter in every direction and the net drying effect will be negligible. If you have jets of air that focus on discrete spots, the water in the area you miss is going to spread out and re-wet the track. You have to have a continuous sheet of air, angled to push water exactly where you want it to go. The compressors are huge – as you can see from the diagram above. Three compressors are being towed on a semi truck on the apron, as the center of gravity of the semi is too high for it to be on the banking.
A series of pickup trucks will circle the track in a synchronized way: the truck closest to the outside wall will blow the water there down to the next groove. A pickup following behind in the that groove will push it down further and so on. (One might imagine a blower powerful enough to blow air down the track from the outside groove to the apron. But I bet you’d have a really hard time finding someone to volunteer to be the driver of the truck on the apron.) There’s a nice animation of the process on YouTube.
Blowing the water off the track is only the first part of the process. A vacuum truck on the apron will suck up the water pushed down by the air jets. The process finishes off with the traditional jet dryers – which now only have to evaporate the very thin layer of water that remains on the surface.
The system isn’t Juan Pablo-proof, but because of the hoses and the water sheeting down the track, racecars won’t be allowed on the track while the dryers are out there. Reports are that it’s costing NASCAR mid-to-upper six figures to develop the system — which is probably a small price compared to losing valuable airtime or being shunted to a less-widely distributed cable station due to delays.
The idea is to be able to dry a big track like Talladega in less than an hour, but even Air Titan doesn’t solve all the problems. The rain has to stop before the drying system can be used, so rain delays may be minimized… but they won’t be a thing of the past.
Not until NASCAR figures out how to control the weather.