Author Topic: Were the Lunar Rovers faked?  (Read 279681 times)

Offline Allan F

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Re: Were the Lunar Rovers faked?
« Reply #285 on: March 24, 2013, 12:59:38 PM »

Sorry. That just confuses me. I don't understand your statement that "the mass is much greater than the weight". Mass is measured in kg and weight in newtons; you can't compare them directly, although they are directly proportional. I'm also not sure what you mean about a bump 'transferring' momentum to the chassis (assuming that by "bump" you mean an actual physical feature of the surface), since a bump has no velocity and therefore no momentum.

But. Hmmm. A bump could and does change the velocity vector of some of the vehicle's linear momentum to angular momentum, with the bottom of the opposite wheel as the center of rotation.  I'll crunch some numbers on that and see where they lead.

Sorry if I was unclear. I tend to see the rover as stationary, and the surface moving beneath it. That way, the surface bump hitting the wheel will give the rover an upward push at that wheel. Then the opposite wheel is the center of rotation, and the CoG is lifted with 1/2 the speed and travel as the wheel hitting the bump. And we're just interested in the upward thrust at the moment.

Also, english isn't my first language. I might not express myself as clearly as I wish.
Well, it is like this: The truth doesn't need insults. Insults are the refuge of a darkened mind, a mind that refuses to open and see. Foul language can't outcompete knowledge. And knowledge is the result of education. Education is the result of the wish to know more, not less.

Offline Noldi400

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Re: Were the Lunar Rovers faked?
« Reply #286 on: March 24, 2013, 01:25:05 PM »

Sorry. That just confuses me. I don't understand your statement that "the mass is much greater than the weight". Mass is measured in kg and weight in newtons; you can't compare them directly, although they are directly proportional. I'm also not sure what you mean about a bump 'transferring' momentum to the chassis (assuming that by "bump" you mean an actual physical feature of the surface), since a bump has no velocity and therefore no momentum.

But. Hmmm. A bump could and does change the velocity vector of some of the vehicle's linear momentum to angular momentum, with the bottom of the opposite wheel as the center of rotation.  I'll crunch some numbers on that and see where they lead.

Sorry if I was unclear. I tend to see the rover as stationary, and the surface moving beneath it. That way, the surface bump hitting the wheel will give the rover an upward push at that wheel. Then the opposite wheel is the center of rotation, and the CoG is lifted with 1/2 the speed and travel as the wheel hitting the bump. And we're just interested in the upward thrust at the moment.

Also, english isn't my first language. I might not express myself as clearly as I wish.

That's more or less what I was thinking. I'm trying to figure out how you calculate the amount of "upward" movement for a given forward velocity and size of "bump".  Just to simplify, for an initial figure I'm ignoring the damping effect of the suspension.

Your english is excellent, but we may have to clarify terms occasionally. Oh, how did you like the seat belt design?
"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline Allan F

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Re: Were the Lunar Rovers faked?
« Reply #287 on: March 24, 2013, 01:33:58 PM »
The best designs are those, who do the job while adhering to the 'kiss'-principle. "Keep it simple, stupid!"

The momentum delivered, is of course dependent on the shape of the bump. Something like sin(a) x height x v^2 where a is the angle between flat ground and the peak of the bump, v is the velocity of the LRV. It's probably more complicated than that - this only works for simple shapes.
Well, it is like this: The truth doesn't need insults. Insults are the refuge of a darkened mind, a mind that refuses to open and see. Foul language can't outcompete knowledge. And knowledge is the result of education. Education is the result of the wish to know more, not less.

Offline Zakalwe

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Re: Were the Lunar Rovers faked?
« Reply #288 on: March 24, 2013, 02:29:33 PM »
This is one of the reasons I love hanging around engineers - the combination of complexity where required and simplicity where possible is positively elegant.

Engineering: The Art Of The Practical.

I'm not an engineer, but the way that I've always looked at it is that any eejit can design something to be overly complicated. It takes a skill to xome up with the simplest, most elegant solution possible.
"The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.' " - Isaac Asimov

Offline nomuse

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Re: Were the Lunar Rovers faked?
« Reply #289 on: March 24, 2013, 03:15:27 PM »
Simple is hard.  That's the fun part.

The story I tell sometimes is my own mangled version of "Basho and the Merchant."

A well-to-do merchant asks a well-known sumi-e artist to paint him a fish, which he will then frame in his shop in a prominent place.  The artist agrees.  Six months pass, and the painting hasn't been delivered.  The merchant drops by again, "How's my fish coming along?"

"In a little," says the artist.

Ten months, same thing.  The merchant is getting a little sharp at this point.  Twelve months, a full year after placing the order, the merchant stalks into Basho's little place.  "Paint my fish or return my money!"

Basho says nothing.  He quietly puts out a fresh piece of paper, wets a brush.  Swish, swoop, pop!  Twenty seconds, and there is this absolutely gorgeous fish painted in fresh black ink.  The merchant is instantly mollified.  "This is," he says, "This is wonderful!  But...it only took you twenty seconds to paint.  Why did I have to wait a year to get it done?"

Basho says quietly, "It took me a year to learn how to paint it in twenty seconds."

Offline Tedward

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Re: Were the Lunar Rovers faked?
« Reply #290 on: March 25, 2013, 04:28:18 AM »
I have learned much again. I did not think about this. But looking back through the excellent replies and information I cannot help but think that the only option for Anywho is to build a simple replica weighted accordingly to test it. Would this work? Then burn it when it does not go his/her way.

Offline ka9q

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Re: Were the Lunar Rovers faked?
« Reply #291 on: March 25, 2013, 04:53:44 AM »
It takes a skill to xome up with the simplest, most elegant solution possible.
One of my favorite engineering sayings (I wish I could take credit for it, but I can't) is that the job isn't done when there's nothing left to add, but when there's nothing left to take out.

Offline onebigmonkey

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Re: Were the Lunar Rovers faked?
« Reply #292 on: March 25, 2013, 08:36:56 AM »
It takes a skill to xome up with the simplest, most elegant solution possible.
One of my favorite engineering sayings (I wish I could take credit for it, but I can't) is that the job isn't done when there's nothing left to add, but when there's nothing left to take out.

I have a variation on this from the many times I have dismantled laptops and re-assembled them:

If there are screws left over, you didn't need them.

Offline Captain Swoop

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Re: Were the Lunar Rovers faked?
« Reply #293 on: March 25, 2013, 12:23:09 PM »
I have a variation on this from the many times I have dismantled laptops and re-assembled them:

If there are screws left over, you didn't need them.

Not always true. The importance of those screws might not show until (for example) the one left holding the screen hinge breaks or the one missing from the board by the USB sockets lets the board flex just enough to break their fixing.

By the time something like a Laptop reaches the shops any screws or other parts that aren't needed have been pared away to save cost.

Offline cjameshuff

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Re: Were the Lunar Rovers faked?
« Reply #294 on: March 25, 2013, 12:33:58 PM »
Not always true. The importance of those screws might not show until (for example) the one left holding the screen hinge breaks or the one missing from the board by the USB sockets lets the board flex just enough to break their fixing.

Or the board now has freedom to flex enough to short out against something, frying potentially thousands of dollars of hardware and destroying who knows what data.

Cutting screws not only saves cost in the BOM and in assembly, it saves room, a scarce commodity in laptops. If they used an unusually large number of screws for something, it was probably to fix a possibly non-obvious problem.

Offline geo7863

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Re: Were the Lunar Rovers faked?
« Reply #295 on: March 26, 2013, 08:07:01 AM »

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).




Yes those supports are needed under the frame because it is such a delicate little flower that it can't even "hold their weight", yet on the moon those same masses can literally jump onto the rovers and then slam them into bumps all they want without any concerns.




Hi All, my first topical post... Anywho you appear to be talking with total emotional conviction and no subject knowledge whatsoever!

WHO exactly said that the Lunar Rover would have collapsed under 1G? You see it's really no good saying 'oh someone (with obvious and total authority) has said that xxx occurred"... you really do have to say who that 'Someone' is, otherwise you could be quoting your sister's 5 year old son and expect us to go 'oooh!....ahh! an enlightened one!" ( I am of course hypothesising that you do indeed have a sister with a 5 year old son for illustrative purposes only....if not please do not take it to mean that I am saying with any great authority that you do have a sister with a 5 year old son....just as we will not take it to mean that because you THINK someone said the Lunar Rover would collapse under 1G that that is indeed true!)

The second quote here makes me believe that you appear to think that the LR would suddenly collapse with bits bouncing everywhere to the loud sound of 'BOING!!!!' just like in a Wily Coyote cartoon! Please peruse the attached photograph. Its a NASA photograph of Two Astronauts (Cernan and Schmitt) fully suited and booted and ready to rock and roll, and sat on a Lunar Rover...here on earth under 1 G...please note that there are not bits flying off everywhere, and had this been filmed I very much doubt if the sound 'BOING' would have been heard!

we can see that this is in a NASA clean environment, the Lunar Rover has its Kapton coating and all the bits and bobs it needs on the moons surface, so this is pretty much obviously not a 'test hack' used to hoon around here on earth during training. The chassis of the Lunar Rover itself is certainly strong enough to support weight here on Earth, but it is on stands, so the limiting factor is obviously in the suspension/wheels. Even then had it not been on stands I doubt very much whether it would have collapsed like a delicate little flower!

One of my hobby's is building motorbikes (don't do design just throw off the shelf bits together!) now in my riding kit I weigh over 100Kg (sorry don't do pre-decimalisation) if I were to fit a shock absorber on my bike that had a rating of 50Kg and I suddenly sat on my bike would it collapse like a delicate flower?...no of course it wouldn't.... I may however damage components and I certainly wouldn't be able to ride the bike let alone ride it safely!

So come on Anywho leave the emotion at the doorstep and look at the hard evidence!

(edited: because of spelling and leaving words out..doh! I really should proof read before pressing the 'post' button)
« Last Edit: March 26, 2013, 08:38:59 AM by geo7863 »

Offline Allan F

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Re: Were the Lunar Rovers faked?
« Reply #296 on: March 26, 2013, 08:31:48 AM »
Nice picture - you can almost see the supports under the frame (which were there), keeping it from deforming and damaging the wheels.
Well, it is like this: The truth doesn't need insults. Insults are the refuge of a darkened mind, a mind that refuses to open and see. Foul language can't outcompete knowledge. And knowledge is the result of education. Education is the result of the wish to know more, not less.

Offline geo7863

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Re: Were the Lunar Rovers faked?
« Reply #297 on: March 26, 2013, 08:43:47 AM »
Nice picture - you can almost see the supports under the frame (which were there), keeping it from deforming and damaging the wheels.

I just pulled the pic off Google, the original is 3.56 MB so the detail is really quite good, there is also a Black and White photo taken at the same time(ish) as this one which I think is even better!

Offline Zakalwe

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Re: Were the Lunar Rovers faked?
« Reply #298 on: March 26, 2013, 09:03:28 AM »
Here's a picture of the Apollo 15 crew sitting in the Rover with no supports. Shock, horror, there's even a third crew-member leaning on it. Now, by the standard of evidence the anywho uses, this must prove that the LRV wasn't a fake and it was OK in 1G



Care to comment, anywho?
"The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.' " - Isaac Asimov

Offline Trebor

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Re: Were the Lunar Rovers faked?
« Reply #299 on: March 26, 2013, 09:03:40 AM »
Here is a short clip showing the rover being tested in earth gravity...

www.youtube.com/watch?v=vzfWuMFrJuU