Were the Lunar Rovers faked?

[Jason Thompson]

No, the are just an attempt to divert away from the subject matter, which is an army test which shows the rover cannot get enough traction to operate in 1/6g.

Wrong. When other examples that DO NOT support your conclusions are given they are issues YOU have to deal with. You don't get to dismiss them as diversions. Physics is universal. If it doesn't work on one thing it won't work on another.

So we have the rover wheel that is tested in a simulated lunar soil and it can only muster enough traction to drive up a 20 degree slope before traction becomes too problematic.

Yes, because at this point it has to effectively cancel out the rearward acceleration of its own weight due to the slope before it can move forward at all: something that it does NOT have to do on the flat. Which bit of that is not clear?

To accelerate the rover has to find enough traction to sustain a pull of 5 times its own weight, and that is undeniable.

No, it does not. It has to provide enough force to move itself, starting from a speed of zero and slowly building up the speed. It can do this with ANY force. F = ma.

The test shows a 50% drawbar pull coefficient is possible with the available traction, basic physics say a 500% coefficient is needed for acceleration.

No, your total lack of understanding of basic physics makes you assert that repeatedly without any actual basis in reality.

BTW, the silence is deafening wrt anyone claiming the army test proves the rover could operate on the moon, it seems like the best tactic is to shift the discussion away from the test to tug boats lol.

It is not our burden of proof. It is yours. and so far all you have done is failed to meet it.

[onebigmonkey]

So we have the rover wheel that is tested in a simulated lunar soil and it can only muster enough traction to drive up a 20 degree slope before traction becomes too problematic. That means traction is at its designated limit when the wheel has to sustain a pull of a little more than 1/3 of its own weight, there is a safety margin in that figure so lets round it up to a 27 degree slope where it has to pull 50% more than its own weight.

You might want to look at how they derived that lunar simulant there.

Please can you also give us your sources of information as to the nature of the slopes on which the LRV would be driving, and which slopes it actually did drive on that were greater than the stated capabilities of it, and also your sources showing that the surface material would be incapable of providing traction.

I did ask this before, but the silence was deafening.

[JayUtah]

No, the are just an attempt to divert away from the subject matter, which is an army test which shows the rover cannot get enough traction to operate in 1/6g.

No, they are an attempt to show you how you are misinterpreting the test.  Since you have utterly failed to interpret practically anything correctly in this discussion, kindly stop for a moment and consider that we're trying to get you to realize something that everyone else in the engineering world sees already.  Your knee-jerk reaction is simply to dismiss the counterexamples on a pretext.

BTW, the silence is deafening wrt anyone claiming the army test proves the rover could operate on the moon...

Fishing for straw men is not an argument, nor is shifting the burden of proof.

...it seems like the best tactic is to shift the discussion away from the test to tug boats lol.

Oh, please.  You've been trying to argue by irrelevant analogy for weeks.  It's a poor time now to start trying to tar others with a similar brush.

Your understanding of the physics principles is wrong.  Hence the model of vehicle dynamics you're using to "prove" the LRV is impractical, is commensurately wrong.  Your wrong-headed model would nevertheless apply to other vehicles.  Hence if it were true and probative for the LRV, it would have to be equally true and probative for other tractive vehicles.  It is provably not, therefore your homegrown yardstick is discarded.

You evidently realize this, which is why you're desperately trying to trump up reasons why we shouldn't attempt to validate your model.

[Tedward]

No, the are just an attempt to divert away from the subject matter, which is an army test which shows the rover cannot get enough traction to operate in 1/6g.

OK, page one, post one, by you. You want to get back on topic then Your claim the motors are not capable, please show your workings out, I don't know but I reckon I could follow your examples if you paste them in here. Going to dodge this again after so many pages?

[Jason Thompson]

Anywho, perhaps you'd go through some 'basic physics' with us, to show where we're going wrong, according to you?

1: Do you agree that F = ma?

2: Do you agree that it follows from that that a = F/m, and that therefore if I have a mass of, say 100 kg, I can accelerate it with any force at all, and all that will change is the rate of acceleration? So if I apply a force of 1 N it will accelerate at 1/100 ms^-2, a force of 10 N will accelerate it at 1/10 ms^-2, a force of 100 N at 1 ms^-2, and so on?

Let's start there.

[anywho]

To accelerate the rover has to find enough traction to sustain a pull of 5 times its own weight, and that is undeniable.

So when my car is on black ice, where the friction coefficient is around 0.01, it cannot move? My car weight 1700 kilos, and according to you, it has to be able exert a pulling force of 6.5 tonnes? Is that right?

On the moon f your car weighs 1700kgs then it has a mass of 10,200 kgs, so it has to find enough traction to pull 8,500kgs on top of the weght (this is not a force of 8500kgs, it is just an additional mass it has to tow)

On the moon your car would weigh only 283kgs but would still have to get enough traction to pull the 1700kgs along the black ice.

Anywho, perhaps you'd go through some 'basic physics' with us, to show where we're going wrong, according to you?

1: Do you agree that F = ma?

2: Do you agree that it follows from that that a = F/m, and that therefore if I have a mass of, say 100 kg, I can accelerate it with any force at all, and all that will change is the rate of acceleration?

1. Yes

2. No, not when a vehicle is on a loose surface, you have to get enough traction to overcome the rolling resistance and that can not only be significant but can also be very complicated to work out due to issues like the wheel sinking into the surface (both before and in addition to any wheel spinnage).

It can sometimes be impossible to apply the force needed to accelerate the vehicle, or do you believe it is impossible to get stuck on a loose surface as long as you just go slow enough? even towing multiple trailers with your 4x4 on a loose surface?

To overcome the complexities inherent n a loose surface you could do some very complicated modelling, or you could conduct some tests. If those tests show you can only accelerate at x rate pulling a maximum of 50% before slippage is too problematic, then it's a no-brainer that you will get bogged f you try to pull 500%.

[JayUtah]

2. No, not when...

Do not complicate the basic physics.  Get the basic physics right first, then add the real-world complicating factors. This is where you habitually go wrong.  You try to fumble your way through secondary factors as a substitute for understanding the basics qualitatively.

[VQ]

No, the are just an attempt to divert away from the subject matter, which is an army test which shows the rover cannot get enough traction to operate in 1/6g.

Perhaps this should have been addressed more unambiguously earlier then - the report does not say that.

[ka9q]

On the moon f your car weighs 1700kgs then it has a mass of 10,200 kgs, so it has to find enough traction to pull 8,500kgs on top of the weght (this is not a force of 8500kgs, it is just an additional mass it has to tow)

Do you understand rolling resistance? I just explained it here a few days ago. This is the force needed to keep a wheeled vehicle going at a constant speed on a level surface. It is independent of speed but varies linearly with weight, so if the vehicle is transported to the moon and operated on a comparable surface the rolling resistance is only 1/6 of that on earth. That means only 1/6 as much motor power is needed to keep the vehicle moving at a constant speed.

The only force that doesn't vary with gravity is that needed to accelerate the vehicle, because inertial acceleration is the one place where mass really matters. Here you are limited by the fact that the static friction of the wheels, i.e., the maximum torque they can take without slipping, is also reduced to 1/6 of its earth value. So you simply can't accelerate or brake as rapidly on the moon as you can on earth, at least if you don't want the tires to slip. But kinetic friction, while often lower than static friction, isn't always so, and if you don't care if the wheels slip a little and/or if the coefficient of kinetic friction is close to that of static friction, this isn't a serious problem.

Besides, drivers usually spend far more time cruising than accelerating. Since the LRV's top speed on the moon for a given motor power is at least 6x that on the earth, it simply means the astronauts couldn't do much drag racing on the moon. It hardly means they couldn't drive around prospecting.

You complained that 1 hp was "obviously" insufficient for the LRV. But the LRV operated in a vacuum where aerodynamic drag is totally absent, in a 1/6 g gravity field where rolling resistance is only 1/6 of its earth value, and is limited in peak acceleration because of the decrease in maximum allowable traction force, at least if you care about wheel slippage. In other words, the LRV didn't need a bigger motor, and it probably couldn't have used one anyway.

[Jason Thompson]

2. No, not when a vehicle is on a loose surface,

I didn't ask about the surface. We'll deal with the details later. Answer the question. Do you agree that acceleration is proportional to force?

[nomuse]

No, the are just an attempt to divert away from the subject matter, which is an army test which shows the rover cannot get enough traction to operate in 1/6g.

Explain why the Army (or the report), did not reach the same conclusion. 

[Echnaton]

No, the are just an attempt to divert away from the subject matter, which is an army test which shows the rover cannot get enough traction to operate in 1/6g.

That is your interpretation of the test.  The test report itself does not say that.  So we are left with the possibility that your interpretation is wrong and are asking you to examine that possibility, which you have steadfastly refused to do.   

If the rover could not operate on the moon, how is it that we have video of a vehicle that is indistinguishable from the lunar rover operating in an environment that is indistinguishable from the lunar surface?

[twik]

If the Army tests really proved that the traction was insufficient, why didn't they just redesign the wheels with, say, spikes?

[raven]

If the Army tests really proved that the traction was insufficient, why didn't they just redesign the wheels with, say, spikes?

Or snow chains!

[Noldi400]

If the Army tests really proved that the traction was insufficient, why didn't they just redesign the wheels with, say, spikes?

Well, that's pretty much the bottom line, isn't it? If the test had determined that the tire/weight/motor combination was not able to meet the desired parameters, they would have gone back to the drawing board and made changes until they had a combination that worked.