Were the Lunar Rovers faked?

[smartcooky]

Does anyone here detect the distinctive odour of socks?

[anywho]

Basically, the position seems to be, as it so often is:

So I'm going to focus on this one small detail....

To you guys 1/6g is only a small detail that has to be overcome because you see, and believe, the rovers hooning around with no traction problems and not even looking like rolling is a possibility, so driving in 1/6 is all just fun with one of you even mentioning the "dukes of hazard" yeehaa.

In reality 1/6g equals 1/6 the traction, and that is a big problem, not a "small detail". In the link is a coefficient of traction table which lists Dirt (packed dry) .5 and Ice (free of snow) .07, so on the moon that .5 becomes approx .08 which is more comparable to ice than any other surface (and that is being generous because on the moon it is loose dirt).

http://www.saltflats.com/traction.html

So on the moon there should be all the traction difficulties of driving on ice...

...The surface is at times more like a mogul run than a road....

...On earth you would not want to end up sideways on such an uneven surface, on the moon it is many times easier to roll a vehicle...

..when one astronaut is on board approx 3/4 of the weight is on one side of the vehicle, so yes, it is a very unbalanced vehicle especially for the moon where, once again, it is many times easier to roll a vehicle than on earth.

Can we all agree on some points?

Traction on a loose surface on the moon will be similar to ice on earth

It is many times easier to roll a vehicle on the moon than the earth

There are no groomed roads on the moon and the driving surface was at times very uneven (might stop all the irrelevant anecdotes about driving, and going sideways, on dirt roads)

A balanced vehicle has, by definition, the weight relatively well balanced, ergo, a vehicle with 3/4 the weight on one side is unbalanced.

On the moon where it is many times easier to roll a vehicle having a balanced vehicle would be significantly more important than on earth.

[Allan F]

Basically, the position seems to be, as it so often is:

So I'm going to focus on this one small detail....

To you guys 1/6g is only a small detail that has to be overcome because you see, and believe, the rovers hooning around with no traction problems and not even looking like rolling is a possibility, so driving in 1/6 is all just fun with one of you even mentioning the "dukes of hazard" yeehaa.

In reality 1/6g equals 1/6 the traction, and that is a big problem, not a "small detail". In the link is a coefficient of traction table which lists Dirt (packed dry) .5 and Ice (free of snow) .07, so on the moon that .5 becomes approx .08 which is more comparable to ice than any other surface (and that is being generous because on the moon it is loose dirt).

http://www.saltflats.com/traction.html

So on the moon there should be all the traction difficulties of driving on ice...

...The surface is at times more like a mogul run than a road....

...On earth you would not want to end up sideways on such an uneven surface, on the moon it is many times easier to roll a vehicle...

..when one astronaut is on board approx 3/4 of the weight is on one side of the vehicle, so yes, it is a very unbalanced vehicle especially for the moon where, once again, it is many times easier to roll a vehicle than on earth.

Can we all agree on some points?

Traction on a loose surface on the moon will be similar to ice on earth

It is many times easier to roll a vehicle on the moon than the earth

There are no groomed roads on the moon and the driving surface was at times very uneven (might stop all the irrelevant anecdotes about driving, and going sideways, on dirt roads)

A balanced vehicle has, by definition, the weight relatively well balanced, ergo, a vehicle with 3/4 the weight on one side is unbalanced.

On the moon where it is many times easier to roll a vehicle having a balanced vehicle would be significantly more important than on earth.

What tires were used in that table? How do you calculate the balance? What is the CoG for the LRV? If I am to agree on anything, I'd like to see why. The LRV didn't exceed 18 km/h. What kind of g-loads did that inflict on the frame?

The CoG is very critical to your claim. If the Cog (loaded or unloaded) isn't higher above the ground than the distance between the tires, the vehicle will be quite stable.

Also, you're disregarding the fact, that the people who developed the LRV KNEW the kind of enviroment it was to be used in. Is it possible that they actually made some hardware designed specifically to deal with the dangers it would face on the moon?

[BazBear]

I'm pretty sure you can't just divide a given earth traction coefficient by 6 to get the a lunar traction coefficient...but there is one obvious big problem with the numbers you are using...

Coefficient of Traction for Rubber Tires on Various Surfaces
Source: Forestry Handbook by Karl F. Wenger (1984)

Concrete (dry)                                                   .70
Asphalt (dry)                                                     .50
Asphalt (wet)                                                     .45
Gravel (packed, oiled, dry)                                   .50
Gravel (packed, oiled, wet)                                   .45
Dirt (packed, dry)                                               .50
Mud                                                                  .15-.40   
Snow (dry, on loose gravel)                                 .25
Ice (free of snow)                                               .07

Does this look like a rubber tire to you?

[Allan F]

Googling around, I see that the LRV is quite stable. It can pitch up to 45 degrees in any direction, and still be able to drive on. It can traverse obstacles 30 cm high, climb and descend 25 degrees slopes.

Now, if the LRV was 182 cm wide (distance between the centers of the wheels), the CoG should be lower than 91 cm, even fully loaded. Draw a line from the bottom of the wheels 45 degrees up, and you'll find the CoG.

Removing one astronaut, putting about 30 kg 46 cm (half of the half with of the LRV) offset from the centerline, would that make the LRV unbalanced? You'll be moving the CoG 30kg/50kg x 46/182 cm = 15 cm off the centerline. Is that unbalanced?

Edit: removing one astronaut would also LOWER the CoG, increasing the stability of the LRV.

[Allan F]

I'm pretty sure you can't just divide a given earth traction coefficient by 6 to get the a lunar traction coefficient...but there is one obvious big problem with the numbers you are using...

Coefficient of Traction for Rubber Tires on Various Surfaces
Source: Forestry Handbook by Karl F. Wenger (1984)

Concrete (dry)                                                   .70
Asphalt (dry)                                                     .50
Asphalt (wet)                                                     .45
Gravel (packed, oiled, dry)                                   .50
Gravel (packed, oiled, wet)                                   .45
Dirt (packed, dry)                                               .50
Mud                                                                  .15-.40   
Snow (dry, on loose gravel)                                 .25
Ice (free of snow)                                               .07

Does this look like a rubber tire to you?

Those numbers are very outdated. Modern tires have a friction coefficient up to .85 on dry asphalt. More if it's specialized racing tires.

[nomuse]

To you guys 1/6g is only a small detail that has to be overcome because you see, and believe, the rovers hooning around with no traction problems and not even looking like rolling is a possibility, so driving in 1/6 is all just fun with one of you even mentioning the "dukes of hazard" yeehaa.

In reality 1/6g equals 1/6 the traction, and that is a big problem, not a "small detail". In the link is a coefficient of traction table which lists Dirt (packed dry) .5 and Ice (free of snow) .07, so on the moon that .5 becomes approx .08 which is more comparable to ice than any other surface (and that is being generous because on the moon it is loose dirt).

http://www.saltflats.com/traction.html

Nonsense.  Who was it who said, "Simplify as much as possible, but no further?"

What is the friction co-efficient between a shovel and a scoop of dirt held in it?

Snow chains here on Earth are CHAINS.  They are steel, which is very hard and smooth, unlike the sticky rubber of a tire.  Yet, they work better.  Why?  Because they mechanically interact with the material.

You are attempting to describe the performance of the LRV as if it is simply a light-weight automobile, only in less gravity.  It is not.  It does not have pneumatic tires.  It has individual motors in each wheel.  There is no differential.  There are no treads, per se.  There are chevrons of metal attached to the mesh of the wheel. 

The only way to understand the performance of that vehicle under those conditions is by addressing the actual mechanism of that vehicle and how it interacts with those actual conditions.

So on the moon there should be all the traction difficulties of driving on ice...

...The surface is at times more like a mogul run than a road....

...On earth you would not want to end up sideways on such an uneven surface, on the moon it is many times easier to roll a vehicle...

..when one astronaut is on board approx 3/4 of the weight is on one side of the vehicle, so yes, it is a very unbalanced vehicle especially for the moon where, once again, it is many times easier to roll a vehicle than on earth.

Where is the astronaut in relation to the wheelbase?  It is the length of the lever that matters, not some arbitrary comparison with some other vehicle.  And, yes...both seats are WITHIN the wheelbase.

Can we all agree on some points?

Traction on a loose surface on the moon will be similar to ice on earth

It is many times easier to roll a vehicle on the moon than the earth

There are no groomed roads on the moon and the driving surface was at times very uneven (might stop all the irrelevant anecdotes about driving, and going sideways, on dirt roads)

A balanced vehicle has, by definition, the weight relatively well balanced, ergo, a vehicle with 3/4 the weight on one side is unbalanced.

On the moon where it is many times easier to roll a vehicle having a balanced vehicle would be significantly more important than on earth.

None of these strike me as particularly descriptive of the LRV.

[BazBear]

Those numbers are very outdated. Modern tires have a friction coefficient up to .85 on dry asphalt. More if it's specialized racing tires.

I suspected as much. I copied the full list from the link Anywho provided to point out that the list he's quoting was specifically for rubber tires.

[gillianren]

Nonsense.  Who was it who said, "Simplify as much as possible, but no further"?

According to my research, it was Einstein speaking a bit disparagingly of Occam's Razor, though I also believe that it's the best description I've ever heard.  (My research, I confess, was some time ago.  I have also corrected your punctuation.)  This is one of those situations where we are clearly trying to separate farther than possible.  And by "we," I mean "Anywho," who still hasn't answered my research question.

[Glom]

I don't get this assertion that the LRV is unstable. It looks stable to me. It is low and flat. I would have thought the risk of rolling over was very low.

Sounds like someone is twisting observations to fit desired conclusions.

[raven]

You know, even if the LRV got stuck somehow, as I believe happened on at least Apollo 15 once, you know what the astronauts could do?
They could get off their butts, perhaps unload experiments, go at each end, and simply move the darn thing.

[anywho]

I'm pretty sure you can't just divide a given earth traction coefficient by 6 to get the a lunar traction coefficient...but there is one obvious big problem with the numbers you are using...

Coefficient of Traction for Rubber Tires on Various Surfaces
Source: Forestry Handbook by Karl F. Wenger (1984)

Concrete (dry)                                                   .70
Asphalt (dry)                                                     .50
Asphalt (wet)                                                     .45
Gravel (packed, oiled, dry)                                   .50
Gravel (packed, oiled, wet)                                   .45
Dirt (packed, dry)                                               .50
Mud                                                                  .15-.40   
Snow (dry, on loose gravel)                                 .25
Ice (free of snow)                                               .07

Does this look like a rubber tire to you?

Those numbers are very outdated. Modern tires have a friction coefficient up to .85 on dry asphalt. More if it's specialized racing tires.

Who cares if they are outdated and technology has improved, it would have improved for ice as well so the comparison is still valid. Find another set of figures if you want, I have seen other tables in the past and the results are always very similar, those were just the easiest to find with a quick google.

Snow chains here on Earth are CHAINS.  They are steel, which is very hard and smooth, unlike the sticky rubber of a tire.  Yet, they work better.  Why?  Because they mechanically interact with the material.

Snow chains, which are often plastic today, work because they have low surface area and are designed to bite into the snow, they would have a fraction of the value on the moon because they rely on weight.

The chevrons look nothing like snow chains, they are flat and with a comparatively large surface area. I spent a fair bit of my youth at ski resorts and those chevrons would be useless in most slippery conditions.

The Soviets supposedly sent a rover to the moon and the tracks on their 8WD rovers are more like chains, the soviet rover was nowhere near as high performance as the apollo rovers were yet they seem to take low traction a lot more seriously.

[Jason Thompson]

To you guys 1/6g is only a small detail that has to be overcome because you see, and believe, the rovers hooning around with no traction problems and not even looking like rolling is a possibility, so driving in 1/6 is all just fun with one of you even mentioning the "dukes of hazard" yeehaa.

No, to us 1/6th G is a significant detail but not a major obstacle because we are qualified to judge it/ This board includes a whole raft of scientists and engineers. Moreover they have demonstrated their understanding of this subject here in this thread. And yet you insist we just believe it because we see it. What are your qualifications in any relevant field?

In the link is a coefficient of traction table

Which is irrelevant because it applies to rubber tyres. The rover did not use rubber tyres.

...On earth you would not want to end up sideways on such an uneven surface, on the moon it is many times easier to roll a vehicle...

A comparative statement that is meaningless unless you can show how easy it would be to roll the rover on Earth. It is low, flat and has no weight of bodywork.

Traction on a loose surface on the moon will be similar to ice on earth

No, because you have no characterised the lunar surface beyond 'loose dirt'. You have taken no account of the cohesive qualities of the regolith, nor of the type of wheel the rover used, which was flexible and a wire mesh, providing much more interaction with that dirt.

It is many times easier to roll a vehicle on the moon than the earth

So how easy is it to roll the rover on Earth? Your answer needs to take into account the rovers speed, low centre of gravity, and the capabilities of the suspension system to absorb the deflection of the vehicle caused by hitting an obstacle.
 

There are no groomed roads on the moon and the driving surface was at times very uneven (might stop all the irrelevant anecdotes about driving, and going sideways, on dirt roads)

So what?

A balanced vehicle has, by definition, the weight relatively well balanced, ergo, a vehicle with 3/4 the weight on one side is unbalanced.

But this is meaningless. The important question is not where its weight is but where that puts its centre of gravity. Show your calculations that indicate where the centre of mass is and what angle the rover would have to reach before it would tip.

On the moon where it is many times easier to roll a vehicle having a balanced vehicle would be significantly more important than on earth.

Agreed. now show us how easy it would be to roll the vehicle in either location.

[anywho]

I don't get this assertion that the LRV is unstable. It looks stable to me. It is low and flat. I would have thought the risk of rolling over was very low.

Sounds like someone is twisting observations to fit desired conclusions.

It looks stable for earth but you have to consider that it is many times easier to roll on the moon, and that the rovers are very lightweight with drivers that are very heavy (comparatively).

We are used to seeing vehicles that weigh a few thousand pound with drivers that weigh a few hundred so in that way these don't "look" too unstable.

But in this case the rovers weigh 460lbs and the astronauts weigh 400lbs, with one driver on that is 3/4 the weight off to one side, this is extraordinary, it would be the equivalent of having 10 blokes sitting on the one side of a normal earth vehicle, or 5 if you have a fiat bambina. Would that still look stable to you?

Adding to that very abnormal imbalance is the fact that the ground is very uneven, and as said earlier, it is many times easier to roll a vehicle on the moon. How many times easier it is to roll would depend on the degree of the slope hit but I would suggest 3or 4 times easier to roll would not be unreasonable.

If you ended up going sideways on the slippery and uneven surface I think it would be a straight 6 times easier to roll, or at least I can't see why it wouldn't be.

[Tedward]

No evidence yet then, just a point of view. So easy to copy and paste from your findings, why don't you?


Edit. I have just realised that range rovers are so dangerous, they cannot ever go off road, they will fall over for certain.