Were the Lunar Rovers faked?

[smartcooky]

Well, I'm waiting for poo!!

Sooner or later, the subject of poo is bound to come up.

1. How did astronauts do poos if they were a long distance away from the LM on an LRV jaunt when they were caught short?

2. Did the astronauts suffer from "sphincter impaction" from bouncing up and down on the LRV.?

3. If they did it in their suits, how would the dispose of it?

You know its only a matter of time before P1000 anywho starts asking about poo!

[raven]

It's actually somewhat interesting reading if you want to know.

[anywho]

Apples and oranges. Or, more appropriately, apples and grapes.

No, the LRV cannot support a total of 800 lbs [363 kg] of astronauts and equipment in Earth gravity.

Yes, it can easily support a 67 lb [30 kg] astronaut jumping onto the seat in lunar gravity. Driven with confidence, yes.  It did have a top speed of 20 kph, but according to the transcripts the more usual speed was 8 to 10 kph, not much faster than a brisk walk on Earth.  They weren't slamming the thing around like a Baja Buggy - they were well aware of the danger.

That 67lb astronaut jumping onto the seat in lunar gravity still has a 180kg (400lb) mass, and once something is moving it has momentum, and that momentum is determined by the mass and velocity, not weight.

It is a 180kg (400lb) mass free falling onto the seat (albeit slower than on earth) when the astronauts jump up and onto the rovers on the moon, not a 67lb weight.

Likewise, when they hit a bump that causes the chassis to change direction, it is the mass and velocity that will determine the forces on the vehicle, not the weight.

Perhaps the reason is that it's one of the top image results in Google for "lunar rover tracks", and the first that looks like a close-up.

Yep, my mistake.

I've computed the roll stability factors for the lunar rover

You have computed the "roll stability factors for the lunar rover" and yet you question the premise that it would be many times easier to roll on the moon?

Why do you ask for numbers when you have already done them, you should know that it either is or isn't "many times easier to roll on the moon".

By questioning the premise are you indirectly saying it isn't many times to roll a vehicle in 1/6g than it is on earth?

  I'm an engineer.   

You're an engineer who disputes the premise that the vehicles are unbalanced with 3/4 the weight on one side?

Why don't you ask a truck driver? They would roll their eyes at anyone who thinks you can have a weight similar to that of the vehicle itself, load it entirely on one side, and then call the vehicle balanced. Most would probably refuse to drive the vehicle until it was properly loaded no matter what any engineer says, and that is on earth.



 

[Echnaton]

Why don't you ask a truck driver? They would roll their eyes at anyone who thinks you can have a weight similar to that of the vehicle itself, load it entirely on one side, and then call the vehicle balanced. Most would probably refuse to drive the vehicle until it was properly loaded no matter what any engineer says, and that is on earth.

What in the name of your deity does a truck on earth have to do with the LRV on the moon?  Nothing as far as I can tell.  Can you provide some numbers with your analysis please? 

[DataCable]

That 67lb astronaut jumping onto the seat in lunar gravity still has a 180kg (400lb) mass, and once something is moving it has momentum, and that momentum is determined by the mass and velocity, not weight.

And what acceleration is causing that mass to move?  Hint: I've bolded the answer above.

It is a 180kg (400lb) mass free falling onto the seat (albeit slower than on earth)

Which, by definition, means less momentum.

Likewise, when they hit a bump that causes the chassis to change direction, it is the mass and velocity that will determine the forces on the vehicle, not the weight.

Which means the lower lunar gravity will not make the rover more prone to roll over.

Why do you ask for numbers when you have already done them, you should know that it either is or isn't "many times easier to roll on the moon".

I'll re-phrase your question and pose it back to you.  If you know that it is "many times easier to roll on the moon," does that mean you've done the necessary computations?

Why don't you ask a truck driver?

Are you a truck driver?  If not, have you actually asked any truck drivers, or are you just assuming what they'd say and/or roll their eyes at?

[Not Myself]

Why don't you ask a truck driver?

Are you a truck driver?

 

It's déjà vu, all over again!

[Tedward]

No info yet. Quelle surprise!

[Noldi400]

Apples and oranges. Or, more appropriately, apples and grapes.

No, the LRV cannot support a total of 800 lbs [363 kg] of astronauts and equipment in Earth gravity.

Yes, it can easily support a 67 lb [30 kg] astronaut jumping onto the seat in lunar gravity. Driven with confidence, yes.  It did have a top speed of 20 kph, but according to the transcripts the more usual speed was 8 to 10 kph, not much faster than a brisk walk on Earth.  They weren't slamming the thing around like a Baja Buggy - they were well aware of the danger.

That 67lb astronaut jumping onto the seat in lunar gravity still has a 180kg (400lb) mass, and once something is moving it has momentum, and that momentum is determined by the mass and velocity, not weight.

It is a 180kg (400lb) mass free falling onto the seat (albeit slower than on earth) when the astronauts jump up and onto the rovers on the moon, not a 67lb weight.

Likewise, when they hit a bump that causes the chassis to change direction, it is the mass and velocity that will determine the forces on the vehicle, not the weight.

Well, DataCable beat me to the response, so I'll not rehash what he said except to point out that the statements bolded in red are self-contradictory; you seem to be saying that "mass and velocity" are unrelated to "weight". 

Look at it this way: the effect of a local gravity field is measured in units of acceleration; i.e., in calculations, gravity can be treated as acceleration. So in considering only vertical movement:

Velocity is determined by acceleration x time;
Weight is determined by mass x acceleration;
Momentum is determined by mass x velocity.

All standard definitions, right out of the book. If we then substitute the definition of velocity for velocity in the momentum definition, we can say that:

Momentum is determined by mass x acceleration x time.

But look at this! The section in blue is the definition of weight! So, substituting again, we find that:

Momentum is determined by weight x time.

How about that? Momentum in a vertical motion caused by gravity - an astronaut jumping up and coming down on the rover seat - is directly proportional to weight.


[One of you actual engineers please check my work - if I made a mistake please point it out and I'll gladly retract it.]

[Jason Thompson]

That 67lb astronaut jumping onto the seat in lunar gravity still has a 180kg (400lb) mass, and once something is moving it has momentum, and that momentum is determined by the mass and velocity, not weight.

And you have already had it explained to you that the ability of a material or structure to withstand brief forces is different from its ability to withstand sustained force without deforming or failing. It is not remotely suspect to read that a vehicle could withstand the force of an astronaut jumping onto it but could not support the weight of a man for sustained periods in Earth's gravity.

You haven't deigned to supply us with the source of your initial comment about the rover's abilities, but in any case the comment says nothing about the rover failing immediately if it is sat on by an astronaut on Earth. That's your implication so you can spin a whole argument based on the unsupported notion that you can compare its ability to withstand the brief effects of a suited astronaut jumping into the seat on the Moon and its ability to support a suited astronaut for unspecified periods on Earth.

Likewise, when they hit a bump that causes the chassis to change direction, it is the mass and velocity that will determine the forces on the vehicle, not the weight.

And how have you accounted for how the structure of the vehicle absorbs that force? Hitting a bump will cause the wheel to deform, the suspension to respond and even the chassis to flex a little before it will cause the entire chassis to change direction. That's what those systems were for, after all. What force would be required to overcome all that designed-in flexibility and cause the entire vehicle chassis to shift direction?

You have computed the "roll stability factors for the lunar rover" and yet you question the premise that it would be many times easier to roll on the moon?

Why do you ask for numbers when you have already done them, you should know that it either is or isn't "many times easier to roll on the moon".

Let me tell you something about who you are talking to, anywho. I have been talking to Jay via forums like this for over ten years now. He has proven expertise, experience and credentials in the fields we are talking about here. If he tells me he has done the computations and disputes your assertions, I will accept his word because I know he can do those computations, and I know that if I ask him to he will, when he has the time, provide those computations and explanations to support his assertions. He has done so many times before. That is how you get your arguments taken seriously in discussions like this one.

You, on the other hand, despite repeated requests, have proved unwilling or unable to provide the numbers to back up your position. Jay does know the numbers. He is asking you for them not because he needs them himself but for the same reason we are: because you need to present them to prove to the people you are trying to persuade that you actually know the first thing about what you are arguing about.

By questioning the premise are you indirectly saying it isn't many times to roll a vehicle in 1/6g than it is on earth?

Show us the computations that show it is. So far your demonstrated knowledge of physics hasn't left the high school textbook level, and your application of it isn't even up to that standard. Unfortunately for your arguments, large portions of physics, when you get into detailed applications like the rolling of a vehicle in the lunar environment, go waaaaay beyond the level of physics understanding you have so far demonstrated. Prove us wrong and support your assertions with actual numbers and computations, and show they are appropriate. All you have so far is handwaving, appeals to intuitive reasoning (which often lets us down when we apply it because a lot of science and engineering is not intuitive: his is why we have specialists rather than just getting any old joe off the street to design our spacecraft), and invalid comparisons to other vehicles like mobility scooters.

I'm an engineer.   

You're an engineer who disputes the premise that the vehicles are unbalanced with 3/4 the weight on one side?

No, he is disputing that it is significantly unbalanced and that this makes it very easy to roll.

However, he definitely is an engineer. What are you?

Why don't you ask a truck driver? They would roll their eyes at anyone who thinks you can have a weight similar to that of the vehicle itself, load it entirely on one side, and then call the vehicle balanced. Most would probably refuse to drive the vehicle until it was properly loaded no matter what any engineer says, and that is on earth.

And when you can show that comparing a single-function lunar vehicle to a truck on Earth is in any way valid we'll start taking you seriously.

[Glom]

As I already explained, the velocity is affected because of the lower gravity. Therefore, the force on impact will be lower.

You can see this by thinking of the energy. When the astronaut drops onto the LRV, gravitational potential energy is converted to kinetic energy. Since the former is less, the latter must also be less.

[anywho]

And you have already had it explained to you that the ability of a material or structure to withstand brief forces is different from its ability to withstand sustained force without deforming or failing. It is not remotely suspect to read that a vehicle could withstand the force of an astronaut jumping onto it but could not support the weight of a man for sustained periods in Earth's gravity.

It would be highly unusual, as I said earlier, normally you might expect to be able to sit on something like a kids bike, and even ride it on a smooth surface, but possibly not be able to ride it over bumpy terrain without it breaking.

What makes this claim even more unusual is that, unlike the kids bike, the rovers are engineered to be driven over bumps, yet we are told they cant be sat on. It's a complete paradigm shift where something is engineered for dynamic loading but not able to be sat on.

Added to that is that the astronauts are allowed to drive over the speed limit so there is enough redundancy to hit those bumps even harder, yet not enough to be even sat on?

Let me tell you something about who you are talking to, anywho. I have been talking to Jay via forums like this for over ten years now. He has proven expertise, experience and credentials in the fields we are talking about here. If he tells me he has done the computations and disputes your assertions, I will accept his word because I know he can do those computations, and I know that if I ask him to he will, when he has the time, provide those computations and explanations to support his assertions.

Let me tell you something about him, he hasn't disputed one of my assertions so far. 

All he has done is ask for numbers in an attempt to infinitely complicate simple assertions, this is unfortunate because many here see his demands for numbers as disputing the assertion and perhaps leads people to think, incorrectly, that it is no easier to roll a vehicle on the moon than it is on earth.

As I already explained, the velocity is affected because of the lower gravity.

Yes, the velocity of falling from 6 inches onto the rovers will be slower on the moon than falling from 6 inches on earth, the velocity will be the equivalent to falling onto the rovers from 1 inch on earth.

[Chew]

All he has done is ask for numbers in an attempt to infinitely complicate simple assertions, this is unfortunate because many here see his demands for numbers as disputing the assertion

No, we all see it as asking you to prove your assertions with your calculations. Simple as that.

[Chew]

Why all this assuming the astronauts jumped into their seats anyway? They could barely move in their suits so how could they jump into their seats?

[Jason Thompson]

It would be highly unusual,

Prove it. Don't just waffle on meaninglessly, support your assertions with numbers and sound engineering principles.

Added to that is that the astronauts are allowed to drive over the speed limit so there is enough redundancy to hit those bumps even harder, yet not enough to be even sat on?

The rover was designed to tolerate things at its maximum speed. Not at a speed limit: at the maximum speed it was capable of achieving regardless of what the astronauts try and get out of it. And once again you completely ignore the difference between a fleeting impact and a sustained load.

Let me tell you something about him, he hasn't disputed one of my assertions so far. 

All he has done is ask for numbers in an attempt to infinitely complicate simple assertions,

No, he asks for numbers for the same reason we do: so you can demonstrate to us that you actually understand the engineering principles on which you are attempting to draw conclusions. Your assertions may be simple, but the engineering and the physics is not, no matter how much you assert that it is.

Engineering and science are done with numbers and computations. If you really had this argument so sewn up it was indisputable, you would be able to produce those computations and calculations and prove it beyond the point where engineers can argue with you over it. Your inability to do so speaks volumes, as does your assertion that Jay's request for numbers is just an attempt to obfuscate and confuse. Sorry, no. This is a science and engineering problem. No competent engineer would argue things the way you are.

leads people to think, incorrectly, that it is no easier to roll a vehicle on the moon than it is on earth.

Prove that it is incorrect. Don't just say it, prove it.

Yes, the velocity of falling from 6 inches onto the rovers will be slower on the moon than falling from 6 inches on earth, the velocity will be the equivalent to falling onto the rovers from 1 inch on earth.

And the effect of that is what? Numbers numbers numbers.

[DataCable]

...we are told they cant be sat on.

Please cite your source for this claim.