NASA Considers Blimp to Explore Distant Moon

Scientists at NASA's Jet Propulsion Laboratory in Southern California have been asked to design the ultimate all terrain vehicle, something that can operate billions of miles from Earth at temperatures of around 300 degrees below zero, and be able to fly like an aircraft, roll along the ground like an ATV, and cruise across an ocean like a boat.

So they borrowed from the past, and looked to the future, and came up with kind of a flying swamp buggy that dates back to the beginning of aeronautical engineering. It's a blimp.

Later this month, the wizards of Pasadena hope to begin testing a scaled down model of a blimp that could give us a close-up look at one of the most mystifying and intriguing objects in the solar system, Saturn's largest moon, Titan.

Titan is no small body. With a diameter of 3,200 miles, it's bigger than the planet Mercury. We don't know a whole lot about what it's really like, because it is enshrouded in a dense atmosphere that makes it almost impossible to see the surface. But what we've seen so far has left planetary scientists screaming for more.

Floating Over Gas Oceans

Images from the powerful Keck Telescope in Hawaii penetrated the atmosphere just enough to show dark and light areas on Titan's surface. There's a good chance the dark blotches are oceans of liquid hydrocarbons, most likely methane or ethane.

We'll get a better feel for the place in January of 2005, when the Hugens probe is released by the Cassini spacecraft and plunges into the atmosphere of Titan. Cassini, launched in 1997, is speeding toward Saturn and is expected to give us our best look yet at the ringed planet and its moons.

One person who will be watching that encounter with a great deal of interest is Jack Jones, a mechanical engineer in JPL's advanced projects group, who is leading the research effort to find out if a blimp would really work on Titan. The idea has some appeal, Jones says, because a blimp would be so versatile.

"The scientists want to explore the atmosphere, and both the solid surfaces and the liquid oceans. They want to land on both of them and explore," Jones says.

They will do that remotely, of course. There won't be anybody aboard this blimp. It would inflate just as it reaches Titan's atmosphere, and drift around the moon at about six miles altitude during its shake-down cruise. Scientists would use its cameras and instruments to identify areas they want to take a closer look at, and eventually the blimp would use electric-powered propellers to drive it down to the surface and guide it to the desired locations.

The harsh conditions at Titan could make it ideally suited for a blimp, Jones says.

Working at Minus 300

"It's very cold on Titan," he says, and that could work to the advantage of the blimp. A colder climate means a denser atmosphere, and since a blimp — which is actually just a powered balloon — has to displace atmosphere to remain aloft, it works more efficiently in a dense atmosphere.

But designing a blimp to work at 300 degrees below zero is no piece of cake. The tricky part is coming up with a material for the blimp's envelope that will be strong enough to take a hard knock if the blimp bumps into a rock on Titan's surface. Several types of plastics seem promising, according to tests at JPL, but the researchers are still trying to come up with a glue that will seal the pieces together, including the blimp's interior bladder, which will be filled with helium to give it the necessary lift.

"Glues don't work at that temperature," Jones says. Again, several products look interesting, but require further testing, Jones says.

The idea is to build a fairly compact blimp, say about 30 feet in length, that could serve as an instrument platform for everything from high altitude observations to close-up photographs. Once they get to Titan, Jones says, it should be pretty smooth sailing because the atmosphere has very little wind.

There's so little heat from the sun that there isn't a dynamic weather system like we have on Earth. Titan is so far from the sun that sunshine reaching its cloud-tops is about 100 times less than we receive here on Earth. And about 90 percent of that is absorbed by the upper atmosphere, so about a thousand times less sunlight actually reaches the surface of the moon.

That's unfortunate, in a way, because Titan's atmosphere is so rich in organic elements that it is ripe for life, just as the Earth was so long ago. What's really lacking is heat that most scientists believe is necessary for the spark of life.

Seeking Heat, Seeking Life?

So the blimp, if indeed this works out, will probably carry an infrared camera which could detect any heat on the surface of Titan. Many scientists think heat may indeed be generated by geophysical processes on the large moon.

"That would be tremendously interesting to scientists because you have all the ingredients for life there," Jones says. So if the infrared camera detects a hot spot, the blimp could zoom down for a closer look.

"By golly," Jones says, "we might stumble onto some life.

"That would be very exciting."

But of course, as he notes, the ultimate all terrain vehicle is still a long ways from reality. If the Cassini mission shows that it is possible for instruments to function in the dense atmosphere of Titan, then the Aerover Blimp, as JPL officials call it, might be just the ticket for a follow-up mission.

That could come within a decade.

And what an interesting footnote to aviation history that would be. The first human flight of any kind is generally credited to the Montgolfier brothers of France, who built a hot air balloon and flew for five miles over Paris in 1783. Maybe similar technology will allow us to explore a very forbidding world.

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.