 Balloons
have long been utilized as a low-cost way to observe the cosmos
and are routinely employed in observations of the Earth’s
atmosphere. According to a recent review by a NASA scientist,
the future of planetary exploration could lie in balloons that
contain innovative steering devices and robot probes.
Dr. Alexey Pankine, a fellow at the NASA Institute for Advanced
Concepts (NIAC), presented an analysis of balloon applications
for planetary science at the World Space Congress in Houston,
Texas last month. His study, Directed Aerial Robot Explorers
or DARE, is funded by NIAC.
At the heart of the study are balloons that can float in
planetary atmospheres for many days. While balloons have been
frequently used in planetary exploration, their wider use
has been restrained by the inability to control their paths
in strong atmospheric winds. It is not possible to simply
attach an engine, as this would convert the balloon into an
aircraft, which would make it too heavy, too power dependent
and too expensive to send to another planet or high up into
the atmosphere.
As a possible solution, Global Aerospace Corporation has
proposed the use of an innovative device called the StratoSail®
that allows the user to control the path of a planetary balloon.
The device is essentially a wing that hangs on a long tether
several kilometres below the balloon. Strong winds and denser
atmosphere at the wing altitude create a sideways lifting
force that pulls the entire system. 
The DARE report analysed the use of the StratoSail® device
on several planets, including Venus, Mars, Jupiter and Titan
(a satellite of Saturn). Dr. Pankine found that a small, light
wing was able to pull the balloon with a velocity of about
1 m/s across the winds on those planets. This may not seem
like very much, but applied constantly for the duration of
a long mission, it would allow for pole-to-pole exploration
of the atmospheres of Venus and Titan, as well as targeted
observations of Mars and the vast Great Red Spot of Jupiter.
The DARE platforms would carry high-resolution cameras and
other instruments to study surfaces and atmospheres of the
planets. Dr. Pankine envisions small probes being deployed
over a small site of interest. Such robot probes could analyse
atmosphere during their descent on Venus or Jupiter and then
crawl around the soft landing on the surfaces of Mars and
Titan.
"The ability to alter the flight path in the atmosphere
and to deploy the probes would vastly expand the capabilities
of planetary balloons and make possible breakthrough observations
that are not feasible with any other platform," says
Dr. Pankine.
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