I note that the first airship pictured at:

http://www.hobbyspace.com/AAdmin/arc...alAirship.html

it looks like a dark blue in the front part of the V and then silver
in the 2 back parts. On my shelf next to my desk I have one of
these toys that spins in sunlight. Probably most people are
familiar with it, there are 4 little plates that are black on
one side and white on the other that spin in a glass bulb with
a partial vacuum. So I wondered if this is related to the JP Aerospace
propulsion system. My toy moves away from the black side.
Basically molecules bounce away faster from the hotter black
side and so push on it more.

But this would push the airship backwards as it is colored now.
So this does not seem to be it, unless the builder got things
backwards.

Still, this force seems like it could be some fun for airships
at high altitudes. Imagine a single cylinder shaped airship
that is black in the back half and white in the front half,
with something inside separating the two halves.
Imagine that it is moving perpendicular to the sun and rolling
like a rotisserie to even out the heat. So the back half
that is black would be hotter and would have a net thrust.
Anyone know how to calculate this thrust?

-- Vince