vehicular traction question

[Soybomb]

Okay I'm taking a stupid stupid technical writing class. One of my personal projects is to write up a detailed proposal about a mars rover. (Yeah this is college...hah) Anyway my instructor and I are having a disagreement Help me settle it, links are best if you have them

Okay I'm tooling around on the rocky terrain of mars in my mars rover. There is a large boulder in front of my tires that I might climb over. Will I need more traction or less traction that i would on earth to climb that obstacle? I think that I should need just as much traction as I would on earth if not more. In order for there to be traction you need friction. The two types coming into mind here are both divisions of kinetic friction, namely sliding friction and rolling friction. The coefficient of friction is higher for rolling friction is higher than sliding friction. An example is that your braking distance is increased by braking with the wheeling rolling compared to the longer distance you'd have if the wheels lock up. So I'm always going to have more traction if the wheels can keep grip and roll as opposed to slide.

Anyway back to that rock I'm trying to climb. Here on earth, the higher gravity gives the vehicle more weight on the rock allowing for more traction. An example here is that pickup trucks will load the rear down with snow or sandbags to increase the weight over the driven wheels, giving them better traction.

Now she thinks that since there is less gravity on mars the vehicle will be lighter and not have to struggle as much trying to go over the obstacle.

Who is right? Am I just being dumb? Would the mars rover need more, the same amount, or less traction than earth's off-road vehicles. If I'm right, whats an easy way to prove it to her?
Thanks all

 

[Nevo]

Okay, here's a college lesson you need to learn:

When you're having a disagreement with your professor, your professor is right.

The earlier you can learn this lesson, the easier your college career will be.

 

[Soybomb]

Actually she acknowledged that she may not be correct and that she wants to see proof either way

 

[JACKHAMMER]

Both of you are right (i think). When climbing a rock you wouldn't need as much friction because the downward force would be less. (you are climbing a vertical obstacle, so the less weight of the vehicle the less frcition needed to grip). For horizontal surfaces (like your sand bag example) the more weight the better.

 

[JACKHAMMER]

Stupid Double post.

 

[Soybomb]

Hmmm interesting. I would also see the increased traction a necessity in downhill descents. If you slide around too easily, you're going to roll.

 

[JACKHAMMER]

<< Hmmm interesting. I would also see the increased traction a necessity in downhill descents. If you slide around too easily, you're going to roll. >>



Exactly. It is all about how the vectors add up. (Remember frre body diagrams from your physics classes ? )

 

[brxndxn]

I really hate free body diagrams

 

[JohnnyKnoxville]

Is there an engineer in the house? I believe the important factors are the amount of contact area the tires actually have on the surface of the rock and the weight of the vehicle.I'm obviously no rocket scientist but if you did some calculating on the gravity forces and tire patch area,ah please don't make me think this late in the day,I'll get back to you.

 

[Soybomb]

*yawn* *Stretch* *bump*

 

[db]

I wish I had seen this thread 1 hour ago, since I was wishing a happy birthday to an actual rocket scientist, and would have asked him.
I am not qualified, but will guess anyway and say that it's no different in either place, since the gravity in each place not only affects the vehicle weight but also therefore the corresponding amount of friction from same vehicle.

Heh.