Inflatables

I was talking to a blimp guy the other day and he mentioned that the blimps they built use a special low-permeability skin, and I thought that's what we need in inner tubes for bicycle tires, especially for road bikes. I mean, how many times should you have to pump up a tire? You need to inflate car tires maybe once or twice a year, if that. High pressure (100 PSI) road bike tires have to be pumped up durn near every day, or at least once a week. So maybe this blimp material would be good for bicycle tires.

Probably not, blimps don't run high pressure, they have enormous volume relative to surface area, and the skin doesn't need to be flexible. Actually, the less flexible the better. Still, you would think someone would have come up with a better material for bicycle inner tubes. This is one of the big bug-a-boos of high technology. We can build carbon fiber frames that weigh next to nothing, but we cannot build an inner tube that will hold it's pressure. I put this in the same category as shoe laces: places where high technology has fallen on it's big fat face.

The blimp guy also mentioned that the military had been looking at using blimps for aerial reconnaissance. Wouldn't they be easy to shoot down? Well, yes, if you have a weapon that can reach them, like anti-aircraft missiles or fighter aircraft, but regular small arms are not much of a threat. You don't have to be too high up to be out of reach of even a high powered rifle. WWII Bofors 40 mm anti-aircraft gun was effective up to about a mile and a half of altitude. Using our old reliable physics formulas, a bullet fired with a muzzle velocity of 2500 FPS (feet per second), could theoretically reach an altitude of 18 miles , but that's without considering air resistance. And air resistance is crucial. A high velocity bullet traveling horizontally initially loses one FPS of velocity for each foot traveled . So being a mile high should put you out of the reach of small arms, and still put you close enough to the ground to be able to see what's going, especially with most any kind of optics.

Bullet holes by themselves are not a big problem. The holes they make are small, the volume of the blimp is so large, and the pressure so low, that a single bullet hole poses no real threat. The promotional blimps you see flying around sporting events seem to act as bullet magnets for any yahoos in the neighborhood, so the blimp people are very familiar bullet holes.

The big problem with blimps is not with flying them, but landing and launching. A steady breeze they can handle, but when it gets really windy, you also tend to get gusts and changes of wind direction, and those kind of things make a blimp's life miserable. So small unmanned aircraft seem to be the military's preferred method.