Since balloons have proven very useful for scientific research on Earth there are
those who believe they are potentially very useful for exploring other planets as
well. Robot “rovers” have been sent to the Moon and Mars since the 1960’s but
such machines tend to be expensive and have limited range and, due to the long
communications time lag across interplanetary distances, they have to be smart
enough to navigate without running into obstacles or toppling off cliffs. But if a
planet has an atmosphere, a balloon would have many advantages over a rover.
A robot balloon, or “aerobot”, would be much cheaper and lighter than a rover,
with the savings in mass reducing the cost of launch. An aerobot could cover a great
deal of ground, and its view from a height would give them the ability to examine
wide swathes of terrain in far more detail than by using instruments in orbit. For
exploratory missions the aerobot’s relative lack of directional control would not be a
big concern, since there would generally no need to direct it to a specific location.
Balloon designs for possible planetary missions have been unconventional. An
“infrared” Montgolfiere is an attractive configuration because it can be easier to
deploy than a light gas balloon; it does not necessarily require a tank of light gas
for inflation, instead being filled with warmed-up atmospheric gases for lift; and it
is relatively forgiving of small leaks. It will tend to fall to the ground when the Sun
goes down but, as explained below, this can be advantageous.
A more unusual possibility is the “reversible fluid” balloon, which consists of
an envelope connected to a reservoir containing a fluid that is easily vaporized.
The balloon can be made to rise by vaporizing the fluid into gas, and can be made
to sink by condensing the gas back into fluid. There are a number of different ways
of implementing this scheme, but basic principles are the same for all of them.
Fig. A.5.3 Planetary “aerobot” concept. Artistic rendering by Fourth Millennium
320 Appendix 5: Planetary Balloons
those who believe they are potentially very useful for exploring other planets as
well. Robot “rovers” have been sent to the Moon and Mars since the 1960’s but
such machines tend to be expensive and have limited range and, due to the long
communications time lag across interplanetary distances, they have to be smart
enough to navigate without running into obstacles or toppling off cliffs. But if a
planet has an atmosphere, a balloon would have many advantages over a rover.
A robot balloon, or “aerobot”, would be much cheaper and lighter than a rover,
with the savings in mass reducing the cost of launch. An aerobot could cover a great
deal of ground, and its view from a height would give them the ability to examine
wide swathes of terrain in far more detail than by using instruments in orbit. For
exploratory missions the aerobot’s relative lack of directional control would not be a
big concern, since there would generally no need to direct it to a specific location.
Balloon designs for possible planetary missions have been unconventional. An
“infrared” Montgolfiere is an attractive configuration because it can be easier to
deploy than a light gas balloon; it does not necessarily require a tank of light gas
for inflation, instead being filled with warmed-up atmospheric gases for lift; and it
is relatively forgiving of small leaks. It will tend to fall to the ground when the Sun
goes down but, as explained below, this can be advantageous.
A more unusual possibility is the “reversible fluid” balloon, which consists of
an envelope connected to a reservoir containing a fluid that is easily vaporized.
The balloon can be made to rise by vaporizing the fluid into gas, and can be made
to sink by condensing the gas back into fluid. There are a number of different ways
of implementing this scheme, but basic principles are the same for all of them.
Fig. A.5.3 Planetary “aerobot” concept. Artistic rendering by Fourth Millennium
320 Appendix 5: Planetary Balloons