[X] My Assistant

[Guest_BruceMoomaw_*]

What about fluorine?

Not much better, and much harder to store. Unfortunately, it appears that we have to stick with RTGs and Pu-238, much though I would prefer not to.

[EccentricAnomaly]

I don't see anything you get out of this that you couldn't get much better from a balloon -- even a nonpowered one.

No balloon has ever been successfully deployed on another planet. The inflation and the proper envelope material sound like a very complicated problem to solve... and therefore expensive. A slow lander could use a design very similar to Huygens, and it would be much cheaper as a result... and I think the science would be comparable to a balloon.

A balloon would cover a small area in more detail, but a slow lander or glider could cover almost the entire surface. I think it would be possible to design something that could take days or weeks to descend with altitudes of 500 km or so above the surface for most of the time, and maybe a day below 500 km on final descent.

Also a balloon would require better model of the low altitude winds then I think Cassini or Huygens will provide. I think it would be really hard to design such a system without accepting a risk level comparable to Beagle 2.

[The Messenger]

I vote for a very large parachute, with lots of scheduled drift time - who cares where - we don't know enough about the surface to know what is important and what is not. And we better be able to analyse the surface for something other than water and hydrocarbons. This substance 'not found on any other surface in the solar system' has to have a name.

[Gsnorgathon]

No balloon has ever been successfully deployed on another planet.
...

...Except for the two Vega balloons deployed on Venus in 1985 by the Soviet Union.

[edstrick]

The Vega mission balloons were 100% successful. They had a mission goal (I'd have to check to be sure) of 1 days and lasted some 2 days till batteries depleted. Science capability was somewhat rudimentary because of the small payload, power available and direct-to-earth transmission, but it was a considerable technical and scientific success. And the small payload was well thought out and designed.

[Bob Shaw]

I vote for a very large parachute, with lots of scheduled drift time - who cares where - we don't know enough about the surface to know what is important and what is not. And we better be able to analyse the surface for something other than water and hydrocarbons. This substance 'not found on any other surface in the solar system' has to have a name.

Er... ...Titanium? It's like Unobtanium. Oh, damn, someone's used that one. What about natiTium?

Bob Shaw

[ljk4-1]

I don't see anything you get out of this that you couldn't get much better from a balloon -- even a nonpowered one.

How about a rover that uses legs instead of wheels, like the Dante robots?

[Guest_BruceMoomaw_*]

Well, first, the balloon has already been test-inflated repeatedly in Titan-temperature air -- including the cigar-shaped blimp. That's no problem, especially given the fact that Titan's low gravity means that the craft is falling quite slowly while it releases and inflates the balloon. (The large electric motors they'd need for a blimp have also been tested at Titanian temperatures.)

Second, a glider can only land once -- whereas the desired goal for a Titan Organics Explorer is to make landings at several different places (around five). The big problem with a nonpowered ballloon is that, of course, you only have very rough control over where you land -- but to a great extent that's also true with a glider. The Titan Organics Explorer appraisal group carefully considered the possibilities of a Titan airplane as well as blimps and balloons, and ended up saying firmly that the airplane was seriously inferior.

[Guest_BruceMoomaw_*]

As for a rover with legs instead of wheels: first, they're complex and haven't really been proven yet in a real-world environment (consider how short a time it took for the "Dante" legged rover to foul up). Second, Titan's surface is so nasty -- riddled with very steep slopes and likely quagmires -- that a legged rover probably would find it as hard to get around on the surface as a rover with big inflatable tires, and maybe more so.

Finally, any short-range rover of any type has a scientific problem mentioned by the Organics Explorer appraisal group: the impression we're starting to get of Titan from Cassini is that long-distance compositional differences are much more important than short-distance ones.

[lyford]

This sounds like a job for Tumbleweed Rover!!!!!

Strong winds should allow it to travel all over, but calling back home seems to be a bit of a puzzler.

[Bob Shaw]

This sounds like a job for Tumbleweed Rover!!!!!

Strong winds should allow it to travel all over, but calling back home seems to be a bit of a puzzler.

Why did you resign?

Bob Shaw

[EccentricAnomaly]

I just realized the problem with a slow parachute... a parachute kills all velocity vertical _and_ horizontal. A balloon would be much better because it would have longer to drift on the wind.

Now, I'm leaning towards a plane powered by an RTG heat engine. The airspeed on Titan would be very slow, and the wings would be very small. An airplane would be almost as good as a helicopter or blimp, but much simpler to build. And there is less of a need to predict the atmosphere.

[The Messenger]

I just realized the problem with a slow parachute...  a parachute kills all velocity vertical _and_ horizontal.  A balloon would be much better because it would have longer to drift on the wind. 

I like the tumbleweed approach, but there do not appear to be strong winds. How about an airbag balloon with spider accessories? Not a blimp, but a collection of hydrogen filled airbag-like cushons configured in a spherical shape with the landing probe in the middle, and an array of instruments dangling from tethers that analyses and broadcasts. When the probe is ready to land, the instrument clusters are reeled back in. Once on the ground, the probe can inertially drive the balloon coccoon across a verity of terrains, navigating with radar that can see through the bag fabric. Surface analysis is accomplished with drop down analytical tools.

[ljk4-1]

How about a robot probe that moves along the ground like a snake or catepillar?

Why reinvent the wheel that Nature has already developed for the last few million years?

I would call it The Undulator - though they call it Hydra:

http://europa.eu.int/comm/research/headlin...5_12_26_en.html

http://www.robots.org/images/2001_Robot_Ga...e%20planets.htm

http://www.space.com/businesstechnology/te...s_010911-1.html

http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=367

Paper - Biomimicry as Applied to Space Robotics:

http://cswww.essex.ac.uk/technical-reports...cott_Ellery.pdf

[tty]

I just realized the problem with a slow parachute...  a parachute kills all velocity vertical _and_ horizontal.  A balloon would be much better because it would have longer to drift on the wind.

Now, I'm leaning towards a plane powered by an RTG heat engine. The airspeed on Titan would be very slow, and the wings would be very small. An airplane would be almost as good as a helicopter or blimp, but much simpler to build. And there is less of a need to predict the atmosphere.

Nix - a parachute will, after a short while, drift with the wind just like a balloon. If You could invent a parachute that doesn't You would rich, since landing with a parachute in a high wind is difficult and can be dangerous.

Also I can't understand where you got the idea that an airplane has less need to predict the atmosphere than a blimp - if anything it is the other way around. Also an aircraft has the same problem as a helicopter - it can never be realistically test flown on Earth.

In my opinion the only realistic first-generation air vehicle for Titan is a free balloon or possibly a blimp. A blimp can always revert to a free-flying mode if there are control problems or the computer has to safe itself. At such times a crude altitude hold function could be maintained by a simple pressure sensor directly linked to the RTG heater. Try that with an aircraft!

Incidentally a spherical balloon while the optimal form for a free-floater is not good if you want to moor it when "landing" it since a moored spherical balloon is violently unstable. In such situations a "kite baloon" that works as a weather foil is preferable.


tty