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#276 2021-04-06 17:19:34

SpaceNut
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Registered: 2004-07-22
Posts: 23,099

Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

Video showing rover wheels wearing out

https://youtu.be/OlZIIWeLgio

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#277 2021-04-07 12:24:54

GW Johnson
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

I think I have commented before about these wheels:  aluminum is the simply wrong material to use to drive over rocks.  I don't care what alloy or cold-work strength,  or heat treatment.  It is the wrong choice for long life.

A nuclear-powered rover has an inherently long service life,  with essentially unlimited power.  What is the point of sending one of these to Mars,  if its wheels wear out and immobilize it in a couple of years?  BTW,  the new Perseverance rover has pretty much the same wheel design as Curiosity.  I know they say it's improved,  but it's still aluminum wheels on sharp rocks.

Once again,  stupid is as stupid does.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#278 2021-04-07 12:38:04

tahanson43206
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

For GW Johnson re #277

I was intrigued by your observations in this post ... the article at the link below is unapologetic

Surely the mission managers must have considered carbon based materials for the wheel ground contact surfaces ... I wonder how the decision making process, surely involving very smart, highly educated persons, would have resulted in the decision to stay with aluminum.

https://mars.nasa.gov/mars2020/spacecraft/rover/wheels/

I doubt very much the famous/infamous "brother-in-law" effect was at work.

There is too much at stake for NASA leadership to allow that.

(th)

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#279 2021-04-07 20:13:37

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,576
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

Carbon composite would be even worse than aluminum.  The failure stresses are even lower,  and the elongation-to-failure very far lower.

Driving in the rocks with non-inflatable wheels requires high tensile strength and large elongation-to-failure.  Period.  End-of-issue.  You also need strength when soaked out to extreme cold. 

As I said,  there is no point sending a rover to Mars with a power system lifetime of multiple decades,  and wheels that are useless in a couple of years.  Yet NASA has now done this mistake twice.

The material of choice for this is a 300-series stainless steel.  There is no other choice available.  I would recommend 304L,  myself.  A real materials guy might have something even better,  but odds are,  it'll be a 300-series stainless. 

Stupid is,  as stupid does.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#280 2021-04-09 07:27:32

Quaoar
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

GW Johnson wrote:

Carbon composite would be even worse than aluminum.  The failure stresses are even lower,  and the elongation-to-failure very far lower.

Driving in the rocks with non-inflatable wheels requires high tensile strength and large elongation-to-failure.  Period.  End-of-issue.  You also need strength when soaked out to extreme cold. 

As I said,  there is no point sending a rover to Mars with a power system lifetime of multiple decades,  and wheels that are useless in a couple of years.  Yet NASA has now done this mistake twice.

The material of choice for this is a 300-series stainless steel.  There is no other choice available.  I would recommend 304L,  myself.  A real materials guy might have something even better,  but odds are,  it'll be a 300-series stainless. 

Stupid is,  as stupid does.

GW

Which is the weight difference between an aluminium wheel and a steel wheel of the same size?

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#281 2021-04-09 12:21:23

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,576
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

Quaoar:

For the same volume of parts,  the steel part is about 2.8 times heavier than the aluminum part. 

But,  what is the point of saving weight on the wheels,  if you cannot move the rover after about 2 years or so,  when it is nuclear-powered,  and would otherwise run around for decades?

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#282 2021-04-09 18:18:54

SpaceNut
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From: New Hampshire
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

An alloy with Titanium as well as other blends might be able to achive the goal of strong but light mass...

Then again there is the wire mesh lunar tire which might work but it needs to be tried and tested long before its sent....+


Sterling engine produces power from the RTG which has Plutonium...

Curiosity’s RTG was designed to supply about 125 watts continous….

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#283 2021-05-22 18:50:46

SpaceNut
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Re: Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT

60a8cb50e25d05001880cff1?width=1000&format=jpeg&auto=webp

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