ka0use

i was in a bike shop yesterday (salvagetti's, downtown denver) and they had a surly moonlander with really fat tires.

got me to wondering.

could one ride a bike on the moon's surface?

i have no idea what the bright side temp is.

is space absolute zero? if so, would you have to have all lubed parts degreased to prevent the lubes from freezing and preventing riding?

what about the air in the tires? would you have to use solid tires?

i suppose the space suits' bulkiness would be an issue. put on huge pedals, snort! and you'd use up air faster.

imagine the cost to have nasa run one up there as part of a mission. probably a one way trip.

ok, do-able, but not practical.

any rocket scientists out there to offer comment? of all the sci-fi authors who wrote juvenile stories, clarke, heinlein, asimov, anderson i think the only times a bike was mentioned was when the kid rode it on earth. transport elsewhere was powered.

Fargo Wolf

If they can drive a moon buggy whose tires are made out of piano wire, I see no reason why a bike can't be built to pedal on the moon. There would be no suspension, unless it is a coil spring. The tires, I've already mentioned, as air filled ones would explode. It would also have to be built with a space suit in mind too.

AndreyT

Yes, certainly. I'm not sure though what "The Rules" say about wearing a spacesuit while riding a bike.

No. Space is vacuum. Vacuum has no temperature. The idea about things exposed to space necessarily "freezing" is a silly urban legend. Vacuum is in fact a perfect insulator, i.e. it completely stops any direct heat transfer losses and any convective heat losses.

In such environment thermal radiation becomes the dominant heat transfer method, meaning that things heat up relatively quickly in direct sunlight and cool down relatively quickly in the shade.

It will freeze if you let it freeze (by allowing it to lose all its heat through radiation), but it is up to you. With the same degree of success you can let it overheat and burn up instead of freezing.

I'd say that when it comes to lubricants, the primary concern would be the pressure, not the temperature. In non-pressurised environment liquids boil and evaporate much faster, which is what will happen to "ordinary" lubricants.

No. You'll simply have to adjust the pressure to compensate for the lack of external atmospheric counter-pressure. Also, rubber tires have to be kept in certain range of operating temperatures. Outside of that range rubber will either crack or burn.

tsl

DX-MAN

I've often thought about that -- how cool would it be to race mountaincross on the moon? 200-ft jumps, COOL!

Mr. Jim

Here's a better bike option for the moon https://www.bbc.co.uk/newsround/16411939

Pete In Az

You would need fenders, or else, you would get Moon dust (dirt?) all over you and the bike.

JanMM

The big question really is what is the best chain lube for a moon bike? Also, what is the best way to clean the chain on a moon bike?

fishymamba

More importantly: Carbon, Titanium, Aluminum, or Steel?

MichaelW

Would a bicycle give you any advantage on the moon? You would need it folding to minimise storage and the weird shape is easiest to make using carbon fibre.
Mars is probably a more bike-friendly environment than the moon. The extra gravity will keep bike handling and traction in a more earth-like zone.
I imagine that the perfect Mars bike would be a bit similar to my theoretical beach/surf bike. Fat tyres, teflon bearings, singlespeed belt drive.

cyccommute 

Several problems: Space may be a vacuum but it isn't a perfect vacuum. There are still some molecules of gas running around in near earth orbit. The concentration gets less the further out you get but there are still some particles. Since those particles are moving around, they still have some 'temperature' according to the kinetic theory of gasses.

But the moon's surface certainly has a temperature because it's solid and it's exposed to solar radiation. There's no atmospheric insulation so the temperature can fluctuate between 134C (day time) and -153C (night) at the equator. Any object on the surface will experience that temperature fluctuation as well.

Also, because of the kinetic theory of gasses, a vacuum wouldn't necessarily be an insulator. If you have particles that can escape, they will take the heat with them. The reason that things 'freeze' when exposed to a vacuum is that some particles...usually water...outgas from the surface taking heat with them as they leave. That 'outgassing' is what we recognize as 'boiling' under normal conditions but it just happens at a lower temperature in a vacuum. As some of the water leaves as water vapor, it takes a lot of heat with it, 537 kcal/kg to be exact. That amount of heat loss will very quickly freeze water. I do freeze drying at work occasionally, and you can watch liquid water freeze extremely quickly when the vacuum is turned on. That usually occurs at around 100 torr, which is a relatively high vacuum pressure.

The issue with greases, lubricants, tires, etc. in a vacuum is the outgassing. Because the pressures are so low, even materials that we don't normally think of as being volatile would evaporate. Keeping them trapped at the surfaces where they are needed for lubrication would be difficult and the heat of friction would further exacerbate the problem. I'm sure there are ways to do it but they aren't going to be trivial.

You are correct on the tire pressure. Atmospheric pressure is only 14.7 psi at sea level (12.0 psi up here). Going to a vacuum would only change the internal pressure by around 15 psi. If you were running the tires at the limit of their pressure, you'd have to decrease the pressure by that amount to maintain the same safety margin. Pressurizing the tires again might be problematic and the diffusion rate through the rubber of the tube would be very fast because of the pressure differential.

Monster Pete

I remember seeing something about the moon buggy, and that on one mission a fender fell off. The surplus map they used as a makeshift fender was visibly abraded by the dust. You'd certainly want something to keep it away.

ka0use

well, i got to thinking some more and, yes, it hurt. maybe useful in a really large pressure dome?
no suit, no dust, no tire pressure issues. would there be increased air use considering less effort to
ride? true, still have mass.

Tom Stormcrowe

fishymamba

Yes!

AlmostTrick

You really don't need anything that special for a moon bike. Here's mine...

Monster Pete

You'd need to be careful about keeping parts lubricated since most liquid lubricants will 'boil off' in space. Likewise, a lot of plastics will outgass in a vacuum, and metal parts in direct contact will cold weld together (due to really being in direct contact without a thin layer of air between them.) Pneumatic tyres aren't a problem in a vacuum, just reduce the absolute pressure by 1 bar. You'd probably want fat balloon tyres to aid traction on the lunar surface.

hueyhoolihan

i've thought about riding on the moon occasionally too, often when riding into a HEADWIND. which i don't think can occur there...maybe that's why i'm thinking about it. IDK.

i've often thought too that the decrease in gravity would make riding, and especially, hill climbing, much more pleasant. i could be wrong about that, but i'm pretty sure my new bike would weigh only 2.2 pounds and i would weigh only a little over 24 pounds. ya baby!

generally, i picture myself sans spacesuit, or any other type of space apparel. why encumber myself in my imagination? that's reality's job!

Artkansas 

I'm pretty sure we will see bicycles in space. I'm involved in an "Open Source" Mars group. One of the first conversations to happen there was about what would be required for a bicycle on Mars.

Artkansas 

You have to remember that when much of that was written we were in the golden age of petroleum. Exercise was only for professional athletes and weirdos.

For short distance travel, I suspect that the bicycle still has an important role to play. Yes, you will use more air, but balance that against everything needed to make a moon car, and you are still way ahead. I'm guessing that at first trikes will predominate until we decide that falling can be done safely. I'm guessing that proper maintenance will be highly valued.

silvercreek

I was in a Houston bike shop a few weeks ago and a customers small child knocked over a Surly Moonlander that knocked down about 5 other bikes.

Monster Pete

Another thing about designing for space is that you can get away with structures too flimsy to work on Earth. The ladder on the lunar module was one example- if you tried to use it on Earth it would collapse under your weight. Under 1/6 gravity on the moon you could ride a much more slender bike than you could get away with here.

XR2

Earth's moon does indeed have an atmosphere. Not much to speak of however it does exist.

Looigi

So...I wonder if space suits are available combo chamois/diapers. Seems once you use the diaper, it make for a kind of squishy chamois.

hueyhoolihan

i agree. most, if not all, of those fondly remembered writers are now dead. and i imagine their parents and surly their grandparents saw the internal combustion engine as regards transportation a great improvement.

and although i would like to think NASA would entertain the use of a bicycle as a means of travel on far off planets, i'm afraid that entities that have reached a critical size, and NASA easily qualifies in my mind, serve not their original purpose, but, ultimately, a purpose common to similar sized entities. and that is self-preservation. which in this case would be better served by a very expensive self-powered vehicle as opposed to a human powered bicycle.

i can't forget the heat they took over designing, what was it? a 600 dollar hammer? i could just image what kind of press they'd get after suggesting a bicycle that would no doubt justifiably cost over a million bucks i guess. maybe more. maybe a lot more.