Were the Lunar Rovers faked?

[nomuse]

You do realize that horsepower and torque are not the same thing?  Gasoline engines run very poorly at high torque, low speeds.  Electric motors, practically the opposite.  Electric vehicles tend to have smaller horsepower, all else being equal, because starting power needs are not the same as maintaining power.

(I had a nice chat not all that long ago with a guy who works on the electrical systems of the local ferries.  They use diesels to generate power which is sent to electric motors to drive the props.  Why?  It makes sense when you think about the kind of conditions a ferry faces.)

[anywho]

You do realize that horsepower and torque are not the same thing?  Gasoline engines run very poorly at high torque, low speeds.  Electric motors, practically the opposite.  Electric vehicles tend to have smaller horsepower, all else being equal, because starting power needs are not the same as maintaining power.

I compared the rovers power to an electric mobility scooter (and a low powered one at that), not a gasoline vehicle, and not a horse like someone else did.

It is undeniable that 1hp to accelerate a vehicle with a 1500lb mass is ridiculously low even under perfect conditions like a flat, even, solid, surface with solid tyres. Yet on the moon where conditions are anything but perfect the rovers performed amazingly well.

Most people would think in terms of power to weight and consider the performance perfectly fitting, but when we correctly consider power to mass.... 1hp to accelerate 1500lbs... valid questions are raised.

Back later.

[Chew]

You do realize that horsepower and torque are not the same thing?  Gasoline engines run very poorly at high torque, low speeds.  Electric motors, practically the opposite.  Electric vehicles tend to have smaller horsepower, all else being equal, because starting power needs are not the same as maintaining power.

I compared the rovers power to an electric mobility scooter (and a low powered one at that), not a gasoline vehicle, and not a horse like someone else did.

It is undeniable that 1hp to accelerate a vehicle with a 1500lb mass is ridiculously low even under perfect conditions like a flat, even, solid, surface with solid tyres. Yet on the moon where conditions are anything but perfect the rovers performed amazingly well.

Most people would think in terms of power to weight and consider the performance perfectly fitting, but when we correctly consider power to mass.... 1hp to accelerate 1500lbs... valid questions are raised.

Like what? It's acceleration?

Why don't you tell us how fast it could accelerate?

[gillianren]

Do I need numbers to say . . . .

Yes.  You need numbers, because numbers are the language of science.  If you don't have the numbers, you cannot say that you are right.  You can only say that you believe you are right, and we have no reason to assume that you know what you're talking about.

[smartcooky]

I used to go rallying many years ago.  I have personal experience of two-wheel drive on loose surfaces.  We used to go well over six times faster than the rovers.

I used to rally a 1974 Ford Escort RS1600. On loose gravel, I would typically hit top speeds of around 130 km/h with average stage speeds of about 80 km/h. The Ford Escort was a rear-wheel drive, making a lot harder to handle than modern AWD rally cars.

One of my favourite tracks was the Ashley Forest Rally Sprint, a single stage sprint where a typical time was about 1:15 to 1:30.

Enjoy

Best ever winning time was about 56 seconds!!!!

Now who says you wouldn't want to be "going sideways on such an uneven surface".

Well, that is just "business as usual" for a rally driver

[ka9q]

It is undeniable that 1hp to accelerate a vehicle with a 1500lb mass is ridiculously low

Why?

The primary source of vehicle drag on earth, aerodynamic drag, is completely absent on the moon. Moreover, rolling resistance is proportional to vehicle weight so on the moon it is only 1/6 of what it would be on earth.

That leaves the kinetic energy requirement. 1 hp = 745.7 W. The kinetic energy of 1500 lbm (680 kg) moving at 10 km/hr (2.78 m/s) is 2626 J. It would take about 3.5 sec to accelerate to 10 km/hr using a 1 hp motor. What's so ridiculous about that?

[ka9q]

(I had a nice chat not all that long ago with a guy who works on the electrical systems of the local ferries.  They use diesels to generate power which is sent to electric motors to drive the props.

Not just ferries but nearly all modern cruise ships are also diesel-electric.

[onebigmonkey]

Do I really need numbers to say that if the astronauts, in jumping onto the rover, clear the rover by 6 inches on the moon then the forces on the rover will be the same as a fall onto the rover of 1inch here on earth?

Yes.

Do I need numbers to say that a fall from 1inch puts more stress on the frame than the static weight weight of an astronaut?

Yes.

It's basic physics and common sense (although, admittedly, for most people, myself included, it does take a bit of time to stop thinking of weight and instead think in terms of mass)

Unfortunately  it's the basic physics and common sense bit that is lacking here. You keep talking about the forces involved, and weight is a product of those forces.

Mass may be the same on Earth and Moon, but the forces a body is subjected to are different because gravity is different. Your confusion comes from interchanging mass and weight depending on the point you're trying to make, and getting it wrong.

[smartcooky]

Mass may be the same on Earth and Moon, but the forces a body is subjected to are different because gravity is different. Your confusion comes from interchanging mass and weight depending on the point you're trying to make, and getting it wrong.

anywho

IMO, onebigmonkey above has hit on the "failure of understanding" that is leading you to your false conclusions.

Weight only equals mass in a 1G environment. When you take the environment away, mass and weight are no longer equal.

In Zero G, an object with a mass of 1kg has a weight of 0kg
On the moon an object with a mass of 1kg has a weight of approx 167g because its a 0.167 G environment
On Mars an object with a mass of 1kg has a weight of approx 380g because its a 0.38G environment

So, your 1500kg LRV, while it only weighs 250kg on the moon, its mass remains 1500kg. However, that isn't the kicker. The power required to move it horizontally is unaffected by its weight; it affected only by its mass.

Here's a primer for you
http://www.school-for-champions.com/science/gravity_horizontal_motion.htm

If all other aspects are equal (air resistance, friction) it takes the same amount of force to move a vehicle with a mass of 1500kg horizontally on the surface of the moon as it does on the surface of the earth, and moving 1500kg horizontally on the Earth can easily be done with a very small motor. Its more a matter if gearing than it is of power. I've seen a homebuild two seater golf cart (all up weight with two males and two sets of golf clubs, 500kg) powered by a 24v 1/2HP motor.

Of course, you could always go the way of most other HB's who come to this site; deny the science because you don't / can't / won't understand it.

[Tedward]

Often wonder what I produce on my bicycle. I have gears to make life easy and those spindly spoke look like they will snap if I bend them the wrong way. Indeed, I know well that they do.

Anywho. Tell me about the motors. I like learning and when a subject like this comes up I get a lot of information that I did not know yesterday.

So. We have a motor. What type and benefits is it to this, I have seen the manual but my motoring (electric) days with regard benefits of DC series wound vs other never appeared on my training as an apprentice. Then there is the harmonic drive. Sounds like something from Star Trek to me, why was this not fit for purpose. End result here is if you can show the drive train is up to the job or not. Not a comparison you have used, the kit used when it went there.

Your proposal sends you down a path that will be fraught with engineering that I suspect could not be done....



Edit. My spokes would bend I think I meant to say. Though I have snapped a few by poor adjustment, the ping is a dead give away and not wanted on voyage when you are head down on a good hill.

Edit 2. It has been a long time since I dealt with levers and forces and momentum and all that, might kick the old grey cells back into life.

[Jason Thompson]

This is actually the best defense against the argument that the rovers could not be so weak that they could not be sat on here on earth, yet could be jumped onto on the moon, namely that all the talk about the astronauts not being able to sit on them here on earth is something of an urban myth.

Perhaps we can find common ground by all agreeing that if the rovers cannot withstand the static weight of the astronauts here on earth, then they cannot be jumped onto on the moon.

It is extremely difficult to find common ground when you are approaching this from a totally different direction from the rest of us. Faced with the aparently contradictory information your entire argument is based on, there are three possible conclusions:

1: The statement is not actually true but is a bit of hyperbole to illustrate the differences in performance requirements between a rover on Earth and on the Moon.

2: The statement is actually true, though counter-intuitive, because the physics involved is a little bit specialised and not readily understood without some degree of effort.

3: The statement is true and proof that the hours of footage of a rover on the moon, and everything else related to them, was actually faked.

Conclusion 1 is the simplest. Conclusion 2 can either be accepted as the case by realising that your own knowledge of physics is not as extensive as that of the engineers who designed and built the thing. Conclusion 3 requires the dismissal of vast piles of material evidence of the rover doing exactly what it was said to have done.

[nomuse]

Quick bit of engineering here...the spokes on a bicycle wheel are under tension.  The hub does not "press" on the lower spokes, it "hangs" from the upper ones.  That tries to pull in/bend the rim, but since the rim is a circle, any attempt to flatten it merely increases the tension tangential to the load.  Gets a little more interesting under dynamic loads, and a little sheer comes into play, but at no point are the spokes under useful compressive load.  They aren't shaped for it.

Back in the day, we used to knock on them lightly with a metal tool to listen for the right tone.  Any dull ones weren't tensioned right. 

[Jason Thompson]

It is undeniable that 1hp to accelerate a vehicle with a 1500lb mass is ridiculously low even under perfect conditions like a flat, even, solid, surface with solid tyres.

If it is undeniable, provide the numbers to prove it.

[Jason Thompson]

If you find anything in your book about how they tested for 1/6g I will be interested if you want to post it.

Not my burden of proof. You are the one making the claim that the rovers were unable to perform as advertised. It is therefore your burden to explain all the evidence that says they actually did just that. That includes showing the calculations that led you to the conclusions you are presenting here, and showing the depth of research you have undertaken.

[smartcooky]

Of course, what everyone is missing here is the blindingly obvious; that the whole thing is a "self defeating proposition". 

If the lunar rover footage was faked along with the whole Apollo programme, why would NASA need to lie about the size and power of the LRV motors. They could just have used four 1 HP (instead of four ¼ HP) motors, and not made any claims that they were the smaller motors