[Anywho (OP)]

There are so any problems associated with the Lunar Rover that it would seem almost farcical to believe they could possibly be real.

The construction:

It is often said that if astronauts could not even sit on a Lunar Rover here on Earth because the Rovers were built of such lightweight construction that they "would have collapsed in 1 g if the crew sat on it." (1), and that the " The vehicle could support its own weight on earth, but no more" (2).

It would seem to defy basic physics to build a weak design because the astronauts on the moon are not just gently putting their weight onto the vehicles, they are also imparting their considerable momentum onto the vehicles and that momentum will be the same on earth as it is on the moon, the mass of the astronauts and their suits do not change. If we take as an example the method the astronauts supposedly used for getting onto the Rovers we can see that they jump up and onto the vehicles:

Getting to sit on the Rover seat in a stiff pressure suit from the lurain was not so easy. The astronauts found they had to stand facing forward, then with an upward and sideways kick, jump up with their legs and arms stretched out ahead to hopefully land in the middle of their seat.

http://www.honeysucklecreek.net/msfn_missions/Apollo_15_mission/hl_Apollo15.html [nofollow]

p=mv tells us that the momentum that the astronauts have, and therefore the forces they will impart, are the same on the Earth as they are on the Moon as long as they are traveling at the same speed. This means that if the astronauts, in the final stage of jumping onto the rover, fall from a height of 6 inches on the moon then the forces they impart onto the rover will be the same as if they fell from a height of 1 inch here on earth.

Once we understand that the forces of momentum are independent of weight then it is nonsensical to suggest you cannot even sit on a rover on earth, but you can jump on one on the moon. The astronauts and their suits have the same mass on earth as they do on the moon and it is very hard to imagine that jumping onto the rovers on the moon they would have less velocity than sitting on them here on earth.

Similarly, driving the rovers on an uneven terrain where the chassis is often forced to change directions vertically, the forces will be very similar, if not the same as here on Earth. Hitting a mound at 10kph will impart the same forces on the vehicle as hitting a mound at 10kph here on earth, the mass and velocity are the same. If you can't hoon around a crater filled terrain here on earth with the vehicles then you can't do it on the moon. If you can't sit on a rover on earth then you can't jump onto one on the moon.

Traction:

To take a 4WD onto a loose ungroomed surface here on Earth would not be counter-intuitive to most people, however, most people would balk at the idea of taking a 2wd vehicle onto a loose ungroomed terrain here on earth because, quite sensibly, it is unlikely a 2wd, with half the traction of a 4WD, would have enough traction. Well, on the Moon a 4WD does not have anywhere near half the traction of a 4WD on earth, it has only a piddly 1/6 the traction and that is true for steering, braking, and accelerating.

Fully loaded the rovers on the moon have a mass of approx 1,500lbs, yet they only have approx 250lbs of weight on the ground to try and accelerate, steer, and brake the 1500lb mass, and they are on a loose surface. The suggestion anyone can go 4WD driving on a loose surface in 1/6g is ludicrous.

I know defenders of the apollo missions will say that the lunar dust binds together so it is not loose, and will quote astronauts as saying they had big trouble controlling the rovers. The problem with both these excuses is that it is not what we see in the video and photographic footage, instead we see a surface that is very loose with dust being disturbed very easy by the astronauts moving around in it, and we see no control problems with the rovers either in driving or the photos of the tracks. It would appear as though they are merely paying homage to the physics while, at the same time, not bothering to fake any traction difficulties for TV.

Power:

The rovers would appear to be massively underpowered, they have 4 x 1/4hp motors giving a grand total of 1hp to drive a 1,500lb vehicle. One horsepower is low powered even for a mobility scooter, imagine putting seven big blokes on a low powered mobility scooter and seeing what performance you get out of it, yet on the moon they hooned around no problems at all.

Uphill there would be some benefits from being on the moon but driving on a flat surface on the moon you would get the same performance as on earth, simply because it is the same mass that has to be accelerated.

Balance:

The rovers are horribly unbalance vehicles, they weigh approximately 460lbs and the astronauts weigh approx 400lbs each fully suited (3), this means when one astronaut is driving there is approximately 3/4 of the weight on one side of the vehicle:



I doubt many of us would want to drive such an unbalanced vehicle over an uneven terrain here on earth, but on the moon where 1/6 g means it is much more likely to roll the suggestion becomes untenable. If the driver were to hit a rise on the unweighted side of the vehicle then the rover will rise 2, 3, or 4 times higher than it will hitting the same bump on earth (depending on the degree of the slope).

In conclusion:

We are supposed to believe they took a 4WD to the moon that was of such a lightweight design that they couldn't sit on it on earth, but they could jump on it on the moon?

They had no traction problems on a loose surface in 1/6g even though 1/6g equals a whooping 1/6th of the traction?

They had ample power driving a 1500lb mass with a 1hp vehicle?

They could hoon around with one astronaut on one side of the vehicle (approx 3/4 the weight on one side), on an uneven terrain hitting bumps in 1/6g, with no worries at all about rolling?

(1) http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/ApolloCat/Part1/LRV.htm [nofollow]

(2) http://www.hq.nasa.gov/office/pao/History/SP-4204/ch23-3.html [nofollow]

(3) http://www.hq.nasa.gov/alsj/a17/A17_LunarRover2.pdf [nofollow]

[CliffordK]

Ok,
Let's compare the specs of your typical lunar rover to my car.

1957 Fiat 500.
Curb Weight:  499 kg (1,100 lb).
HP: 13 (original 479cc, later upgraded to 499cc, and 17 HP).
Top speed of about 55 MPH.
Construction, Steel.

Lunar Rover
Curb Weight, 209 kilos, 462 lbs.
Loaded weight, max of about 1600 lbs.
Power, 1 HP.
Top speed of about 8.7 MPH, or 14 KPH.
Construction: aluminum alloy.

If you notice while driving, getting up to about 10 MPH doesn't take much power, and many vehicles can do it at idle.  In fact, it is hard to hold some vehicles down to 10 MPH.

And, with my Fiat, while it does seem a bit under powered on the Freeway, I've always thought it had excellent 0 to 10 MPH acceleration.

It may be that for a standard gasoline powered vehicle with transmission, the engine to wheel power conversion would be close to 50%, or less, giving the original Fiat 500 the equivalent of about 6 HP at the wheels.  Direct drive, 1/4 HP to each wheel may give a higher power ratio, perhaps even 100% to the wheels.

I have never felt particularly unbalanced in my Fiat 500, although I might consider a different design for a lighter car.  I have been thinking of a design for a multi-passenger pedal car, and have thought about a 3 person design with a single person in the middle position, 2 people at the sides, and 3 people across when at capacity.

The weakest point on the frame would be the vertical load.  Starting, stopping, and turning, it is likely much stronger.  It isn't flying over bumps very fast.

I've taken a 2wd drive vehicle in some pretty extraordinary places.  While there are a few surfaces that one looses traction, I don't worry too much about dry ground.  It is the wet mud (not on the moon) that is the biggest problem.  Some wheel weight, of course, is good for traction, but a lightweight vehicle would also be much easier to get moving.

I probably would have chosen wide paddle tires like a dunebuggy, or perhaps a more aggressive agriculture tread.  However, narrow tires can actually get good grip by concentrating the weight in a smaller area.

Anyway, I don't see why that vehicle couldn't be able to do a speedy 10 MPH on the moon.

[Don_1]

Not another conspiracy theory .......... please!

[Bored chemist]

LOL
"They had ample power driving a 1500lb mass with a 1hp vehicle?"
So, a bit like a horse then?

[CliffordK]

"They had ample power driving a 1500lb mass with a 1hp vehicle?"
So, a bit like a horse then?

It depends on if it was a Chinese Horse!!!!

Were the motors fan cooled or fin cooled?

[Anywho (OP)]

Ok,
Let's compare the specs of your typical lunar rover to my car.

1957 Fiat 500.
Curb Weight:  499 kg (1,100 lb).
HP: 13 (original 479cc, later upgraded to 499cc, and 17 HP).
Top speed of about 55 MPH.
Construction, Steel.

Lunar Rover
Curb Weight, 209 kilos, 462 lbs.
Loaded weight, max of about 1600 lbs.
Power, 1 HP.
Top speed of about 8.7 MPH, or 14 KPH.
Construction: aluminum alloy.

If you notice while driving, getting up to about 10 MPH doesn't take much power, and many vehicles can do it at idle.  In fact, it is hard to hold some vehicles down to 10 MPH.

And, with my Fiat, while it does seem a bit under powered on the Freeway, I've always thought it had excellent 0 to 10 MPH acceleration.

It may be that for a standard gasoline powered vehicle with transmission, the engine to wheel power conversion would be close to 50%, or less, giving the original Fiat 500 the equivalent of about 6 HP at the wheels.  Direct drive, 1/4 HP to each wheel may give a higher power ratio, perhaps even 100% to the wheels.

I have never felt particularly unbalanced in my Fiat 500, although I might consider a different design for a lighter car.  I have been thinking of a design for a multi-passenger pedal car, and have thought about a 3 person design with a single person in the middle position, 2 people at the sides, and 3 people across when at capacity.

The weakest point on the frame would be the vertical load.  Starting, stopping, and turning, it is likely much stronger.  It isn't flying over bumps very fast.

I've taken a 2wd drive vehicle in some pretty extraordinary places.  While there are a few surfaces that one looses traction, I don't worry too much about dry ground.  It is the wet mud (not on the moon) that is the biggest problem.  Some wheel weight, of course, is good for traction, but a lightweight vehicle would also be much easier to get moving.

I probably would have chosen wide paddle tires like a dunebuggy, or perhaps a more aggressive agriculture tread.  However, narrow tires can actually get good grip by concentrating the weight in a smaller area.

Anyway, I don't see why that vehicle couldn't be able to do a speedy 10 MPH on the moon.

I looked around and found a forum discussion where they say a 1hp buggy has 80% efficiency, that gives your fiat approximately 10 times the hp of the rovers (converting your current 17hp to 8.5 and the rovers to .8hp). If you put 2 people into the fiat it will near enough be equal in weight to the fully loaded rover, so you are more or less comparing the performance of two vehicles that have an order of magnitude difference in the power to weight ration.

You say you have never felt unbalanced in your fiat, well, to get a similar imbalance to the rovers with one astronaut on them you would have to put 5 men all on one side of the fiat (giving 3/4 the weight on one side). I would fancy you would not find this too appealing to drive even in a straight line, let alone over an uneven surface and cornering. Adding to the imbalance is the fact that it would be many times easier to roll a vehicle on the moon than on earth.

You say you have taken a 2wd off road many times and your only fear is wet mud, while if you live in a muddy area this may be largely true because dry mud can set like concrete, I live in a very sandy area and anyone with any brains knows the danger of taking a 2wd onto any sandy area that is not well grassed or at least deliberately compacted by machinery.

The point about the traction is that they didn't have anywhere near the earth equivalent of a 2wd up there, they had less than the equivalent of a 1 wheel drive for traction, it is simply true that 1/6g equals 1/6 the traction so I stand by the assertion that a 4WD is woefully inadequate for driving on a loose surface in 1/6g.

[Anywho (OP)]

LOL
"They had ample power driving a 1500lb mass with a 1hp vehicle?"
So, a bit like a horse then?

More accurately, a bit like a low powered one of these, only instead of one person it has to transport the equivalent of 6 large men:



Mobility scooters can come in up to 3hp, so 1hp is near the bottom end of power for one of these, if you were designing a vehicle to transport a massive* 1500lbs gross would you consider such a low power system to be adequate?

*Massive compared to what mobility scooters are designed for.

[RD]

You can see where one has been driving about and where it is parked ...
http://www.nasa.gov/mission_pages/LRO/news/apollo-sites.html
http://www.nasa.gov/images/content/584392main_M168000580LR_ap17_area.jpg

[CliffordK]

I believe that many dune buggies are two wheel drive.
Often based on VW Bug engines.
And, with the typical open differential, it is not uncommon for a 2 wheel drive to become a 1 wheel drive.

4 wheel electric motors would be an excellent type of traction differential.

I'm not sure you can completely ignore gravity.  On the moon, the rover would sink into the regolith 1/6 as much as on Earth.  The weight on the bearings is also 1/6 as much.  No wind resistance.  Going up hill, it is 1/6 as much weight to move. 

And, if one got stuck, it would be easy enough to get out and push. 

I have no doubt that the astronauts were instructed not to drive into a hole they couldn't get out of.

[Anywho (OP)]

You can see where one has been driving about and where it is parked ...
http://www.nasa.gov/mission_pages/LRO/news/apollo-sites.html [nofollow]
http://www.nasa.gov/images/content/584392main_M168000580LR_ap17_area.jpg [nofollow]

This thread is about the physics of taking a 1hp, massively unbalanced, 4wd to the moon and having no problems with traction, rolling, power etc. It also asks the question whether you can build a rover so weak that it cannot be sat on here on earth and then take it to the moon and jump onto it before hooning around on an uneven surface (both of with should be impossible if it is so fragile that it cannot be sat on here on earth).

I think your post is valid but I am hoping my reply does not lead to a distraction from the subject matter of the thread.

I think those photos from the LRO do absolutely nothing to prove the Apollo missions took place, they are of poor quality compared to what most people would have been hoping for, and they are easily faked.

There are also a few questions about their validity like why are the tracks so clear even very close to the landers, in other words, why didn't the exhaust from the ascent rocket engine taking off disturb the tracks surrounding the lander?

Another question is why are the tracks darker than the surrounding soil? It is known that the lunar soil is darker on the surface due to radiation darkening so any disturbed soil should have a considerably higher albedo than the surrounding soil.

Once again, I hope my reply does not distract from the questions about the rovers and lead to a discussion about the LRO photos.

[evan_au]

On the Earth, the rover has to support its own weight (and presumably gets a bit of structural support from the launch vehicle during the rigors of liftoff).

On the Moon, the rover only has to support 1/6 of its own weight, plus 1/6 the weight of its heavily-garbed passengers.
The momentum is the same at 10km/h on the Moon as at 10km/h on the Earth. However:

• The wheels don't have to hold up so much weight on the Moon, so you can make them very much "softer".
• Similarly, the chassis does not need to be so rigid - it can be much more flexible.
• They occasionally managed to get 1 or more wheels "airborne" (vacuum-borne?) at 10km/h horizontal speed, but because the Lunar gravity is so much lower, the vertical speed would be very much lower than 10km/h.
• Taken together, the change in momentum to stop a vertical impact is spread out over a much longer time on the Moon.
• So the forces on the vehicle would be much less than the impact of an airborne vehicle on Earth.
• And the forces on the vehicle would still be less than driving over the same terrain on Earth at 10km/h without getting airborne (because gravity is lower).

[Anywho (OP)]

On the Moon, the rover only has to support 1/6 of its own weight, plus 1/6 the weight of its heavily-garbed passengers.

That is only true if both are stationary, I have put a link up which shows that the astronauts supposedly had to jump up and onto the rovers, this means that even before being driven the rovers are coming under a lot more force than the static weight of the astronauts either on earth or the moon.

Once we know that the astronauts jump onto the rovers then weight can be ignored in estimating what forces the rovers will come under because it is a combination of mass and velocity that will determine the force, and is a noncontroversial fact that your mass is the same on earth as it is on the moon.

Unless we are to rewrite p=mv to p=wv, meaning weight times velocity instead of mass times velocity, then it is nonsensical to say you can't sit on a rover here on earth but you can jump onto one on the moon.

The wheels don't have to hold up so much weight on the Moon, so you can make them very much "softer".

I don't believe this to be true at all (nor the other comment about the chassis), the wheels and chassis have to be designed for the worst stresses the vehicle will come under, and on both the earth and the moon that will be all the bumps and dips the vehicle hits while being driven, not the static loading.

On both the earth and moon, as you acknowledge, the momentum will be the same at the same speed, therefore hitting bump and rises will put the same stresses on the frame and wheels in both cases, or at least very similar stresses.

Similar stresses means basically that if you can't drive it around hitting bumps at 10 or 15 kph here on earth, then you cant do it on the moon. Yet they tell us you can't even sit on the rovers here on earth but you can drive around hitting bumps on the moon.

[CliffordK]

Ok,
So, on the moon, you have a vehicle that can carry the momentum of a 1500 lb vehicle, at 10 mpg.
However, it has a vertical weight of only 250 lbs.

It would be easy enough to add springs and shocks designed to support a 250 lb vehicle, but with a wide dynamic range, so that they could absorb the impact of say a 1000 lb dynamic impact.  Likewise, your A-Arms and kingpin/spindle assembly would be designed to handle the 1500 lb dynamic load of say pushing into and over a rock.  Furthermore, if you wished to carry 500 lbs of moonrocks, you would load those over the axles, rather than in the middle of the chassis.  Each passenger would weigh only about 1/6 of 400 lbs, or about 67 lbs. 

I could imagine a structure that could absorb the vertical impact of say tossing a 67 lb  of grain on it, by using well designed springs, but would be unable to support 800 lbs of weight applied to the middle of the frame.

Assuming a left hand drive, you might instruct your drivers not to do hard right hand turns with a single driver, and no passengers.  It wouldn't take much to convince the astronauts that their lives depended on safe driving.  They might survive a roll-over, but damage to their spacesuits could be fatal.

Apparently they never ventured more than about 5 miles from the lunar module.  It would be a long bunny hop back to the module, but they were pretty much within walking distance to get back.

[Anywho (OP)]

I could imagine a structure that could absorb the vertical impact of say tossing a 67 lb  of grain on it, by using well designed springs, but would be unable to support 800 lbs of weight applied to the middle of the frame.

Assuming a left hand drive, you might instruct your drivers not to do hard right hand turns with a single driver, and no passengers.  It wouldn't take much to convince the astronauts that their lives depended on safe driving.  They might survive a roll-over, but damage to their spacesuits could be fatal.

When the astronauts jump onto the vehicles on the moon it is not the equivalent of throwing a 67lb bag of grain onto it, it is the equivalent of throwing a 400lb bag of whatever onto it. The difference between earth and the moon is not in the weight because the mass never changes and, unless stationary, it is the mass which is relevant, the only difference will be in the speed at which the astronauts freefall onto the rovers.

Like I said earlier, if they jump onto the rover here on earth and clear the vehicle by 1 inch, and they jump onto the vehicle on the moon and clear the vehicle by 6 inches then the forces on the vehicle will be exactly the same.

However, sitting is a very controlled and relatively gentle process as opposed to jumping, there can be little doubt that jumping onto the vehicle on the moon will put more stress on the frame than sitting on it here on earth.

As you correctly point out any accident is likely to result in suit failure, and therefore death, so there has to be ample redundancy in the structure of the rovers to handle any foreseeable event, yet we are told these rovers are so weak that they cannot even be sat upon on earth but they can be jumped onto on the moon and driven at 15kph over uneven surface with complete confidence?

WRT your next point, there is no evidence the astronauts took it easy when they were in the rovers alone, in fact all the evidence is to the contrary with the highest speeds and most radical driving being done when there was only one astronaut on board belying the fact that there is 3/4 the weight on one side of the vehicle, it is uneven terrain, and that it is significantly easier to roll a vehicle in 1/6g.

[CliffordK]

Ok,
So the astronaut on the moon will act both as a 67 lb weight, and a 400 lb mass.

Just sitting on the rover, the astronaut would exert a downward weight of 67 lbs. 
Going over a bump, however, the astronaut would provide the same resistance to change as a 400 lb mass.

That would play both ways.
When you go over a bump, it would take essentially the same amount of force to get a wheel airborne as on the Earth.  However, it will fall back down 6 times as fast on the Earth.

That may give one a strange sense of stability, that the rover would in fact exhibit similar resistance to flipping on the Earth and the moon., although it would be easier to maintain a wheelie on the moon as there would be less force bringing the airborne tire back down.  Some things might feel like they were happening in slow motion.

If I was designing the rover, I would build it with extremely weak springs.  This would mean that the effect of the majority of the bumps would be transferred to the suspension system, not to the frame and the passengers.

It is possible that the weakness of the frame was overstated, although the springs would likely bottom out if the rover was fully loaded on Earth.

Many of the moon/rover photos indicate that much of the driving was on relatively flat, but bumpy landscape.

Certainly nothing was as rugged as say the McKenzie Pass, in part because the regolith provides a generally sand-like surface.

[Anywho (OP)]

Ok,
So the astronaut on the moon will act both as a 67 lb weight, and a 400 lb mass.

Just sitting on the rover, the astronaut would exert a downward weight of 67 lbs. 
Going over a bump, however, the astronaut would provide the same resistance to change as a 400 lb mass.

That would play both ways.
When you go over a bump, it would take essentially the same amount of force to get a wheel airborne as on the Earth.  However, it will fall back down 6 times as fast on the Earth.

That may give one a strange sense of stability, that the rover would in fact exhibit similar resistance to flipping on the Earth and the moon., although it would be easier to maintain a wheelie on the moon as there would be less force bringing the airborne tire back down.  Some things might feel like they were happening in slow motion.

You will rise significantly higher after hitting a bump on the moon, it may be 3 or 4 times as high depending on the slope of the bump you hit. You will also have approx 6 times the hang time due the parabolic arc being both longer and higher, meaning that it is much easier to roll a vehicle on the moon than here on earth.

There is no easy solution regarding the suspension, if you make it stiff you put more stress on the frame but if you make it soft then you increase the chances of rolling.

I cannot see any advantage to driving a car in 1/6g, only disadvantages like traction loss and rolling being more of a problem etc. Yet with the rovers they supposedly took a vehicle all the way to the moon that would be too unbalanced to operate safely here on earth and therefore many times more dangerous on the moon...

...too structurally weak to operate safely safely here on earth even though the stresses will be largely the same on the moon...

...of such low power that it would be insufficient on earth even though the mass that has to be accelerated is the same on earth as the moon...

....and has a drive system that is of a noted design for loose surfaces on earth (4wd), but makes no concessions for the fact that on the moon there will be only 1/6g and therefore 1/6 the traction.

And it all went swimmingly well with no problems at all???

[Anywho (OP)]

BTW, the Soviets supposedly sent an unmanned rover to the moon, I say "supposedly" because there is a possibility, on both sides, that there was as much BS and bluffing going on at the time of the space race as there was genuine advances.

Anyhow, real or not, the soviets at least made concessions to the low traction of 1/6g by giving their rover 8 wheel drive.



It is also worth noting that because the soviet rover was unmanned and was crawling around in a quasi static manner, it required much less traction than the relatively high performance apollo rovers.

[Anywho (OP)]

Ok,
So the astronaut on the moon will act both as a 67 lb weight, and a 400 lb mass.

Just sitting on the rover, the astronaut would exert a downward weight of 67 lbs. 
Going over a bump, however, the astronaut would provide the same resistance to change as a 400 lb mass.

That would play both ways.
When you go over a bump, it would take essentially the same amount of force to get a wheel airborne as on the Earth.  However, it will fall back down 6 times as fast on the Earth.

It will only fall back 6 times as fast if they both rise to the same height, but on the moon the rovers will, upon hitting a bump, rise many times higher so by the time it comes down the speed difference will be more likely around half as fast than 1/6th the speed.

So the way I see it is that driving around hitting bumps will put very similar stresses on the frames on the moon as on earth because the mass and velocity are the same, the chances of rolling will be far greater on the moon, but when the rover lands after hitting he bump then it will land lighter* on the moon than on earth.

* by "lighter" I mean slower and therefore with less stress on the frame, how much slower will depend on the angle of the rise.

[Anywho (OP)]

Someone on another forum posted footage of them testing the rovers for 1/6g, they had ropes suspending 5/6 of the weight.

This really highlights how farcical driving a 4wd on the moon is, the only test they show is one that is designed not to fail where they take a run up on a firm surface, then just go straight over a short test bed. Effectively this test nothing on the loose surface, not braking, not steering, not acceleration.

The test is, like the whole notion of 4WDriving on the moon, a farce (starts at 2.04, video is set to then)

https://www.youtube.com/watch?feature=player_detailpage&v=FVMfjPXwRO4#t=124s [nofollow]

Even with this mockery of a test you can see the back bobbling around, and that is at slow speeds and over a relatively smooth bed, this highlights how ridiculous the "Grand Prix" test runs were on the moon when they supposedly drove with full control at much higher speeds and over much bumpier terrain.

But the really funny thing about the tests in the video, the ones that were designed not to fail, is that they did fail. The third test shows a start of control loss even before they hit the test bed and they can't regain control instead slipping and sliding until they come to a stop while still on the test bed.

The tests really do highlight everything I have said about how farcical 4WDriving on the moon would be.

[Anywho (OP)]

For the lunar rovers, traction in 1/6g is a massive problem to overcome, the vehicles only have approx 250lbs weight on the ground an yet have to propel a 1500lb mass, and to make things more difficult it is a loose surface they have to do this on.

To do this they had a wire mesh wheel with chevrons covering about 50% of the contact surface area, the chevrons are both smooth and shallow, so the wheel does not have a deep thread. The chevrons directly cover 50% of the frictive surface and they also recess the remaining frictive surface.



These wheels were tested by the US army engineers for NASA and the results appear to show that the rovers could not possibly have operated on the moon.

http://www.hq.nasa.gov/alsj/PerfBoeingLRVWheelsRpt1.pdf [nofollow]

They simulated 57lbs of weight on the wheels, they have a pull coefficient of approx 0.5 to 0.6 before slip becomes so bad it will immobilise the vehicle (1), now I read that as meaning with 57lbs weight the wheel can pull 85lbs to 92lbs before slip is too problematic, yet each wheel has to pull 342lbs to move the rover on the moon.

Does the testing prove that the rovers could not get enough traction to work on the moon?

(1) fig. A12. graph entitled "comparisons of relations off pull coefficients to slip obtained by three different recording methods", it is the last graph, third page from the bottom.

Mod: I've merged this post with a previous, nearly identical topic chain.