In an odd bit of irony, the first technological method of human flight, the lighter-than-air vehicle, continues to haunt the imaginations of many futurists and technology forecasters. Images of mega-blimps hauling material goods have been staples of what the Future Will Hold for at least the last 30 years, and even today, inventors talk about turning airships into "gravity planes," or using them as "stratellites" to serve as city-wide WiFi hubs.
For me, the most plausible future use of lighter-than-air technology is also the most distant: as a means of extended study of other planets. On Earth, the airship proposals largely focus on tasks that can be accomplished by other means (even if less elegantly); on other planets, controlled-flight balloons are often the only way of achieving research goals. Balloons can get a much closer view of the world being studied than can satellites, can see much more of the planet than can ground rovers, and can stay aloft far longer than powered air vehicles. Two balloons have flown (relatively briefly) in the corrosive atmosphere of Venus, and many have pondered the possible use of balloons on Mars. Now the aerospace company Global Aerospace has come up with a design for exploring Mars by lighter-than-air vehicle that just might work.
Floating just several kilometers above the surface of Mars, the guided Mars balloons can observe rock formations, layerings in canyon walls and polar caps, and other features – at very high resolution using relatively small cameras. They can be directed to fly over specific targets identified from orbital images and to deliver small surface laboratories, that will analyze the site at the level of detail rovers would do. Instruments at the balloon's gondola can also measure traces of methane in the atmospheric and follow its increasing concentrations to the source on the ground. This way the search for existing or extinct life on Mars can be accelerated.
The main problem with using balloons is that they can be difficult to control. Powered airships such as blimps use powerful fans as propulsion, but the need to keep weight down -- Mars' atmosphere is barely 1-5% as thick as Earth's -- would reduce the amount of onboard power a Mars blimp could carry. Instead, Global Aerospace has come up with a novel solution: an outboard "wing," suspended at the end of a kilometer of cable.
Global Aerospace Corporation has designed an innovative device, called Balloon Guidance System (BGS) that enables steering a balloon through the atmosphere. The BGS is an aerodynamic surface – a wing – that hangs on a several kilometer-long tether below the balloon. The difference in winds at different altitudes create a relative wind at the altitude of the BGS wing, which in turn creates a lifting force. This lifting force is directed sideways and can be used to pull the balloon left or right relative to the prevailing winds.
Although the BGS wing is part of the Mars balloon proposal, Global Aerospace argues that it would be useful for long-duration high-altitude balloon research on Earth, too.
If the Mars balloon gets off the ground, it may be just the first in a series. Any planetary body with an atmosphere is fair game for the balloon treatment. Global Aerospace has a sprawling proposal (PDF) under NASA's Institute of Advanced Concepts process, encompassing balloon missions to Mars, Venus, Titan and even Jupiter. The most basic form of air travel may well end up a cornerstone of the exploration of our solar system.