The Second Version


A Blimp on the Radar

I am writing this piece offline while I wait for the installation of software on some computers to finish. Yes, IT jobs can be that exciting.

Some days ago my blog-friend Wellington asked me a question about blimps, and that made me think. Apparently there are blimp enthusiasts out there who think that those devices can have a much more widespread use than now.

Instead, I think not, because blimps suffer from a basic but serious physical limitation: air density.

In order to provide buoyancy, a blimp must be less dense than the surronding air. But air is already a low-density fluid, roughly only 1 kg/m3 near the sea level (by contrast, the density of water is 1000 times higher). Even if the blimp were "full" of vacuum, and the mass of the shell and other hardware were trascurable, the most lift that can be provided is of one kilogram per cubic meter displaced.

A blimp with any relevant payload must necessarily be huge, and consequentially cumbersome and slow and very susceptible to wind (because the force exerted by wind is a function of the cross-section of the body). Fixed and rotary-wing aircrafts satisfy the needs for speed, payload and manouvrability much better; their only disadvantage is higher fuel consumption.

However, one use where blimps can be the best choice is for semi-mobile (or semi-fixed) observation and surveillance posts. A crew of a few men – or better, automated sensors – does not require a big payload; the blimp can move around in appropriate patterns slow and steady using little fuel and with little noise. Something that airplanes and helicopters do not do as well.

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2 Commenti:

  • That is correct.

    A slightly better solution are "Hybrid" HTA/LTA vehicles. These are not-so-lighter-than-air vehicles that take up to half their lift from their aereodynamics and the rest from the lifting gas. Bu they are still at disadvantage compared to other flying vehicles.

    As for the surveillance role, projects are already underway.

    Di Anonymous Wellington, Alle 6/10/09 12:00  

  • Are there projects for surveillance blimps also out of the military field, such as in fire early warning role?

    Di Blogger Fabio, Alle 10/10/09 18:58  

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