Lighter-Than-Air Objects (Blimp Sim)

Hey,

I was wondering if anyone has any tips on simulating a lighter than air blimp.
I am quite happy with working out/applying thrust from engines and air resistance, however I am unsure how to work out/simulate the floating, and the forces applied in the vertical direction by gravity and the payload. Currently having a look at using ODE(Java).

Any hints on topics/ideas to look into, or something more thorough would be great.

I haven’t tried this personally, but you could try adding force to each body that is opposite the gravitational force. If the opposing force is equal to the gravitational force, the bodies should be effectively weightless.

Create a “buoyancy” force, which is based on the geometry of your blimp. Basically it is equal to the mass of fluid displaced by your blimp mutliplied by gravity. This means you need to find out the mass of air per unit volume at any particular altitude that your blimp will fly in, and multiply this density by the volume of your blimp. This will give you the mass of air displaced by your blimp, multiply this by gravity and apply the resulting force upwards at the centre of gravity of your blimp.

For a description of buoyancy have a look at this:
http://scienceworld.wolfram.com/physics/BuoyancyForce.html