I like the idea of multiple vehicles. They would make the entourage more adaptable to changing conditions. Specialized vehichles could scout ahead and take greater risk. Slower, safer science packages could follow where it is safe. All could serve as components for rescue. The entourage could accomplish more than a single vehicle and the group would be more adaptable. Sort of a "Wagon Train" to Mars. More "experienced" readers may recognize this reference from way back in the last millenium.

I like to think that my jokes fill a much-needed gap.

Ahem.

Indeed.
You know I was just joking in that post too.

As a gold rule, always travel with more than 3 vehicles when going in off road (Mars) so that the stuck or in trouble ones will be rescated by one of them. Unless, the vehiclue must be specially designateed to travel almost any sort of terrain such as the ones alike to Caterpillar which is very stable and very capable to climb (greater than 30 degrees) , get down (also higher than 30 degree with very little slipping ), and travel over any kind of sands . I think that the next rovers must not carry any wheels but only bands like ones of Caterpillar. This will avoid to send two rovers at the same time. On the other hand, it is better to send a mini MARS GPS which will help rovers to travel easier and faster on Martian land. This will help to free lots of memory and CPU power from the Rover for another purposes .

Rodolfo

Tracked vehicles also have drawbacks (which is the reason most military vehicles are still wheeled)

1. More expensive than wheeled vehicles

2. Tracks wear out quite quickly

3. Require stronger engines because of more friction than wheels

4. Clumsy to steer

5. Less redundancy. If a track fails you are stuck while a multi-wheel (6 or more) vehicle usually can move minus one wheel

tty

Tracked vehicles would also be problematic on much of the chaotic terrain we've seen on Mars. The multi-wheeled independant drive/suspension systems on MER and Pathfinder were developed as a response to the conditions witnessed at the Viking and Pathfinder sites, i.e. the need to egress to rock strewn regions. Tracks are fine for a sandy or fine textured region like Meridiani, but would create a problem with the handful of topography conditions we've observed thus far. Certainly the conditions at Gusev also come to mind.

And, let's face it, we have successfully landed probes at five locations on Mars, and four out of those five locations have very, very similar types of terrain -- rock-strewn with windblown dust/sand drifts building up in various places. Only Meridiani has shown a different type of terrain.

Of course, there are a lot of different terrain types on Mars. But I think a lot of the flatter plains units (the places we're most likely to try landing) are going to be rock-strewn. So the rocker-bogey wheel system is probably going to be the best approach for most future rovers.

-the other Doug

The replies were very interesting. I realice that the tracks has their advantages and disadvantages. However, I think the best lands for tracks are the polar, sandy lands and mountains (lots of climbing and descending) Martian lands.

About the following points:
1) Yes it more expensive but for the project, it is not a matter of the fact that since the project always must look for the best and convenient solution (cheaper solution would be more expensive). The difference is very small when the project is of order of millions versus thousands dollars.

2), I was affraid of this since I saw that the tracks requires more maintenance but the distances that the rovers have advanced is very small (total more than 11 Km!!! and the tracks would still be in good shape.

3), definitely tracks will require engine with more par (force Kg-M) and it is not well suited for solar engine powered but I think, maybe, it would be fine with RTG nuclear isotops.

4) I think it is not a problem. The tracks is also capable to turn - O.

5) I agree it that the multi-wheels has the advantage of redundancy but the tracks band well designated can withstand for many thousands kilometers on soft lands of sands and many hundreds kilometers on harsh land (rockier).

Tha last word is that the tracks are by far needs less help to be rescued for any land, safer to travel (less risk to project of several millions dollars), more capable to reach to any land.

Maybe, the alternative to track is to have a rover with wider wheels and semi-inflated tire or two more wheels if the rover is to ttravel sandy lands and not for polar lands...which would be very slippery. (hard ice).

What I doubt that the rubber tire will not withstand of reactive or corrosive Martian land.

Rodolfo

One other issue to bear in mind with treads - they need to be able to operate at extremely low temperatures. I'm not sure what they've normally made of.
Plus, there are lots of hinges between the individual segments of track - more places for sand to get into, and with no one around to clean it, that might cause problems. But I'm not sure about that; tanks seem fairly robust, though they're also powered by a very strong engine.

One other thing I though of too with treads - space issues. The rover's back 4 wheels were nestled under it during transit, and the front two were folded up at the front. Treads would likely need to be sent into space in their deployed state, which would greatly limit the size of the rover itself.

The another hint would be helpful for Opps to travel is when it is free again and be able to navigate through dunes of sand on the same direction as where the winds blows. That is the rover must travel over crest in perpendicular line since the start of crest is harder (where the wind blows first on the crest) and the other side of crest is softer (where the wind accumulate sand). Going on that way, Opps will climb easier than the other side of crest which is of downslide. That hint is good for Earth sands and I think it will be also good for Mars' sands.