Kathy and I are to make
a hot air balloon but it can’t be powered by a
heater / burner - it has to be solar heated!
Apparently there are astronomers / physicists that
are planning to send payloads to Mars and to get these
machines to travel around the surface of the planet
using a similar hot air balloon. It works like this:
If the equipment lands at night, the air is cold. A
dark coloured balloon will be made to inflate from the
equipment using compressed gas. The whole thing waits
till sunrise. As the Sun rises the gas in the balloon
will heat up faster than the air around it. This will
make it expand and so will become relatively less dense.
This will make it rise.
Ideally this works best in the Polar Regions where
there is the greatest difference in temperatures possible.
We are to make a similar device. The production team
have given us a wireless camera to put on the balloon
as a payload.
Kathy and I talk about the science of this and then
start to make up a couple of prototypes. We intend to
use bin liner bags to make the balloon from. The first
was a geodesic design – a spherical (12 pentagons
called a dodecahedron) structure while a second quite
different design was a sausage shape. As we have no
previous experience we need to try out two very different
designs. Both the balloons looked great and easily filled
up with air by wafting using a board. The sausage was
about five metres long while the round balloon was about
two metres in diameter.
However apart from the beginning of the day there is
always a breeze at the mine and our balloon bellowed
and wriggled about far too much. Even when the breeze
did die down and we could make sure the balloons were
in the Sun nothing happened!
Finally we found out that the bags we had been using
were too thick and too heavy. The production team got
us some lighter bags and we started again.