MSL Wheel Discussion, Moved from MSL at Glenelg thread Options

[Guest_fthurber_*]

ADMIN: A few OT posts moved from the MSL at Glenelg thread.

I don't know about the rest of you but this looks perilously close to the nasty stuff that trapped Spirit and almost trapped Oppie. Very very dangerous.

BTW I am a big fan of JPL but I am not so keen on the J-P-L Morse code in the wheels. These holes in the wheels might tend to dig into the soft stuff instead of floating on top...

Speaking of which... there appears to be a fundamental design flaw (or maybe just a tradeoff) in the wheel systems in MER and MSL. People who drive over soft sand (fishermen on beaches for instance) know that best way to avoid getting stuck is to have large and soft and smooth (so they do not dig in) tires. MSL/MER have just the opposite; small and hard and knobby wheels.

[Tom Tamlyn]

I don't know about the rest of you but this looks perilously close to the nasty stuff that trapped Spirit and almost trapped Oppie. Very very dangerous * * * there appears to be a fundamental design flaw (or maybe just a tradeoff) in the wheel systems in MER and MSL. * * * best way to avoid getting stuck is to have large and soft and smooth (so they do not dig in) tires. MSL/MER have just the opposite; small and hard and knobby wheels.

Golly gee ...

Your post seems perilously like the overture to a resumption of the "inflatable wheels/technology lock-in/reusability" theses that were pursued with such ... ah ... enthusiasm by some posters in the "MSL/Curiosity Landing Method" thread in another discussion forum, beginning at about reply #124. The lengthy advocacy of those theses had achieved a certain kind of perfection when the nsf moderators locked the thread.

Whether or not you were involved personally in that discussion, are you sure that it's appropriate to renew those issues here?

TTT (speaking for myself only)

Edit: fixed typo

This post has been edited by Tom Tamlyn: Oct 6 2012, 07:23 AM

[Guest_fthurber_*]

Golly gee ...

Your post seems perilously like the overture to a resumption of the "inflatable wheels/technology lock-in/reusability" theses that were pursued with such ... ah ... enthusiasm by some posters in the "MSL/Curiosity Landing Method" thread in another discussion forum, beginning at about reply #124. The lengthy advocacy of those theses had achieved a certain kind of perfection when the nsf moderators locked the thread.

Whether or not you were involved personally in that discussion, are you sure that it's appropriate to renew those issues here?

TTT (speaking for myself only)

Edit: fixed typo

Wow it is so easy to step on land mines on this site....

I had no idea that this idea had ever been discussed before! I only recently started reading Unmanned Spaceflight and have never read nasaspaceflight (until just now--thanks for the link). I thought I had been whistling in the wind; I imagined that I was the only one who was advocating large/soft/smooth wheels. Ha! Should have known. Anyway I will stand down on this; too much has been said already.

.

[Stu]

Large/soft/smooth/sexy wheels have been discussed/considered for Mars exploration since Yoda was a lad. They feature in scientific studies and science fiction novels alike. They're not a new idea, in any way. No doubt we'll see them on Mars one day, but that day is a long way off in the future. For now, the wheels we have, and use, are the best ones for the job, designed by people with brains the size of small planets and computers with processing power beyond our wildest dreams. I think we can be pretty sure that there's no design flaw.

And you can rest easy, confident that the rover drivers won't take any risks with Curiosity, or Opportunity, and will only put their well-designed wheels where they're safe to go. That's their job, and they're extremely good at it.

[Guest_Oersted_*]

Speaking of which... there appears to be a fundamental design flaw (or maybe just a tradeoff)

You said it! (My underlining/bolding)

[TheAnt]

You said it! (My underlining/bolding)

Not just a tradeoff or compromise.
It have taken me quite some time to realise what a good solution they provide for moving over unknown terrain.
And since these rovers move at a quite slow pace by any standards. They would be overtaken even by one robot lawnmower - which do move rather slow. They do not need anything else, if there ever will be a more fast moving rover - wheels like on the LRV or Lunokhod.

A tracked rover would have had one small advantage in a few situations, Purgatory might not have happened and being able to take a closer look at the lower part of the cliffs in Victoria crater. With a track you be at the mercy of any bearing at all times, if one seize up the rover is stuck.
Instead Spirit were able to continue, dragging one wheel behind.
Why do I talk about tracks? Well the rocker boggie arrangement is somewhat similar to what a tracked vehicle might have.
Now the rover only have a slight disadvantage of not having full tracks, but it can turn on a dime and move with quite less energy used.

[Phil Stooke]

Slightly different perspective - amateurs second-guessing the most brilliant engineers on the planet is never a good idea.

Phil

[RoverDriver]

I think we are suffering from the http://en.wikipedia.org/wiki/Eternal_september syndrome.

Regarding the ripple, we made sure that we had most of our wheels on solid ground before the scuff. If you noticed we drove near it, took extensive imaging, moved closer, took more imaging, then drove around it, more imaging down to grain size detail and finally used *one* wheel to very gently scuff the ripple.

The part you don't see is that we have done extensive testing on various soils with our engineering models, we have a large group of planetary geologists that assist us rover drivers in analyzing the terrain to determine the load bearing capacity and spot locations that potentially might pose a threat to the vehicle. The J-P-L holes are there to assist in measuring wheel sinkage which is directly related to wheel slip. You also don't see all the safety measures that each drive uses, each drive is carefully crafted to ensure everything that can be detected, is detected as early as possible. You would be amazed at the length of discussions that we have on details that most of the people wouldn't even notice.

I don't want to discourage you in making suggestions but also consider that maybe your idea/suggestion might have already come up, considered, maybe tested and even tried. We still have mortgages and bills to pay so we have a very immediate incentive to keep this vehicle alive and well.

Finally, if you are ever in the LA area drop me a line and I will personally give you a tour of our facility and will go into the fine details of what we do.

Paolo

[tedstryk]

I think we are suffering from the http://en.wikipedia.org/wiki/Eternal_september syndrome.

Bingo

[stevesliva]

It's more that people have to be reassured that the drivers at JPL aren't suffering from said syndrome-- that JPL's institutional memory is not lacking.

[nprev]

It's not. Let's please stay on topic now, eh?

[Astro0]

ADMIN NOTE:
This discussion had run its course and reminds us again of that unwritten rule on UMSF: "we don't know better than the experts".

While it's always interesting to speculate and discuss what's taking place, we shouldn't fall into the trap of trying to second guess the expertise and judgement of the team of engineers, scientists and drivers on this mission or any other. They have shown to us time and time again that they know what they're doing and allow us to enjoy the ride with them.

Topic closed.