Quiz!

[Inanimate Carbon Rod]

Gene Kranz chose one of Apollo 17's wake-up calls. What song was it?

The Carpenters, We've Only Just Begun.

[Inanimate Carbon Rod]

The LRV was powered by four small electric motors in each wheel. The motors each produced how many HP?

[Zakalwe]

The LRV was powered by four small electric motors in each wheel. The motors each produced how many HP?

0.1

[Echnaton]

From The Apollo Lunar Roving Vehicle

Each wheel had its own electric drive, a DC series wound 0.25 hp motor capable of 10,000 rpm, attached to the wheel via an 80:1 harmonic drive, and a mechanical brake unit.

[Echnaton]

What special items were taken aboard Apollo 14 because of CMP Roosa's pre Air Force employment. 

[Laurel]

What special items were taken aboard Apollo 14 because of CMP Roosa's pre Air Force employment. 

A variety of tree seeds (to be planted later and grow into "Moon Trees"). Roosa was a smoke jumper for the Forest Service.

[Glom]

Is this the tree in question?

[Echnaton]

Corrected link

The Apollo Lunar Roving Vehicle

Is this the tree in question?

Don't know for sure about that tree, but here is the NASA page.  It has the known locations of the trees.

The Moon Trees

[ka9q]

Each wheel had its own electric drive, a DC series wound 0.25 hp motor

That may not sound like much, but most of the power required to keep a car going at freeway speed on the earth is in overcoming aerodynamic drag -- of which there is none on the moon. Most of the rest goes to rolling resistance, which with everything else constant, increases linearly with the weight of the vehicle -- which is of course only 1/6 what it would be on the earth.

On the other hand, the lunar surface isn't exactly a high performance roadway.

So, I wonder -- assume we did have paved roads on the moon. How much power would it take to drive a typical earth automobile at typical freeway speeds on level lunar ground?

[Zakalwe]

How many $ per pound of weight saved did NASA pay Grumman in order to reduce the mass of the LM? And what were the weight loss programs called?

[ka9q]

I just worked out my own answer for the mileage of an electric car on the moon.

I drive a Nissan Leaf. Using a spreadsheet I just wrote, and plugging in the best numbers I could find for the Leaf's usable battery capacity, drag, efficiency and overhead power, it gives me an estimated range-per-charge at 65 mph of 77 miles. The actual figure varies due to many factors, but this is pretty close.

Simply setting air density to 0 and the gravity to 1.622 m/s² increases the range per charge at 65 mph to 888 miles. Not bad at all...

On earth, in air, range drops substantially at higher speed because aerodynamic drag force increases with the square of the velocity. Rolling resistance is constant with velocity, but varies directly with vehicle weight. So on the moon, aerodynamic drag goes away and rolling resistance drops to 1/6 of its earth value. Range actually increases with speed because the car's own overhead consumes more energy when the car is driven for a longer time.

This does assume paved roads...

[Glom]

I just worked out my own answer for the mileage of an electric car on the moon.

I drive a Nissan Leaf. Using a spreadsheet I just wrote, and plugging in the best numbers I could find for the Leaf's usable battery capacity, drag, efficiency and overhead power, it gives me an estimated range-per-charge at 65 mph of 77 miles. The actual figure varies due to many factors, but this is pretty close.

Simply setting air density to 0 and the gravity to 1.622 m/s² increases the range per charge at 65 mph to 888 miles. Not bad at all...

On earth, in air, range drops substantially at higher speed because aerodynamic drag force increases with the square of the velocity. Rolling resistance is constant with velocity, but varies directly with vehicle weight. So on the moon, aerodynamic drag goes away and rolling resistance drops to 1/6 of its earth value. Range actually increases with speed because the car's own overhead consumes more energy when the car is driven for a longer time.

This does assume paved roads...

What about modifications to allow your car to operate in a vacuum? How are you going to cool it?

[Echnaton]

You mean a Leaf isn't cool enough, just on its own?

[ka9q]

Like most modern electric cars, the Leaf uses liquid cooling for the motor and electronics, dumping heat into a radiator with a fan. So yeah, it would require modification to work in a vacuum. The radiator designed to dump heat into the air would have to be replaced with a radiator designed to work by pure radiation, and it might have to operate at a higher temperature to be of a practical size. In extreme cases it might have to use a sublimator, but that would be highly undesirable because of its water consumption.

Of course, the fact that power consumption is so low because of the lack of atmospheric drag and the greatly reduced rolling resistance means less waste heat to get rid of in the first place. At 65 mph the rolling resistance that remains is 935 W, which is dissipated in the tires. I don't know if they would need active cooling, but the motor (90% efficiency) would lose only 104W and the electronics about 160W. I should probably take out the HVAC since the passengers will probably carry their own.

[ka9q]

With the electronics overhead reduced to 160W (apparently more accurate than 250W) and the HVAC load reduced to 0 W, the Leaf's range on the moon increases to 1,138 miles. Not bad...