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Old 10-20-10, 04:21 PM   #1
Steely Dan
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"Moon"tain biking and other 2 wheeled cosmic adventures

because i'm a cyclist with a cosmically oriented mind, i dream. i dream of cycling across the surface of the moon and other solar system bodies.

how would it work to bike on the moon? what kind of bicycle would one need? would the physics of cycling work in 1/6 gravity? what about bulky spacesuits, could they be built with the necessary flexibility? maybe mars would be easier because there's at least an atmosphere there, albeit a highly toxic one (to us anyway). imagine an epic climb to the top of olympus mons? or hugging the rim of valles marineris? what about aqua cycling across a methane sea on titan? ice cycling on europa anyone? what interplanetary destination would you most like to explore with your favorite pony?

i've always felt that bicycles completely rule the universe, and with luck, someday they literally will. oh how i would love to live long enough to witness the noblest invention conquer new worlds, but at least i can dream.

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Old 10-20-10, 06:36 PM   #2
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Old 10-20-10, 06:59 PM   #3
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The moon's surface is basically covered in dust. You'd want really fat tires. With no atmosphere, your tires would be inflated to the same (over)pressure as they would be here, but you'd have to use an air source of some sort -- your pump wouldn't work (unless you did it in the airlock or spacecraft.)

As for the physics of 1/6th gravity, I imagine you'd be fine. Hills wouldn't be a problem, at least up until the point where you don't have enough traction in the dust to keep going up. If somebody were to build a road up there, you could go *very* fast with no air resistance and a high gear ratio. If you did crash, going so fast with no air to stop you and only 1/6th gravity, you'd skid and bounce around and such for a very long time!

Any dust you kicked up would not float around -- with no atmosphere, it would fall like a rock.

Mars has 1/3rd Earth gravity. The atmosphere is 1% as thick as ours, so you'd still need a space suit. It's mostly carbon dioxide -- not so much toxic as just not having oxygen and even if it did it's far too thin to support your life.
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Old 10-21-10, 07:22 AM   #4
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Lunar bicycling is something I have thought about as well.

I suspect that given the possible consequences of a crash, that a trike or a quad like a Rhodes car might be the wisest way to go. And you would need carrying capacity to lug around the oxygen if you are planning on going any distance. I guess that food, water and waste would have to be in the suit with you unless you were pedaling some kind of sealed velocar.

As a thought experiment I even pondered whether escape velocity was attainable by bike. With no wind resistance and light gravity it seems as though if you had the gears and the time you could work up quite a speed. Lunar escape velocity is about 5,140 mph. So I'm not sure that a bicycle could reach that speed, though I see no reason you couldn't achieve several hundred miles per hour on a paved road.
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Old 10-21-10, 09:18 AM   #5
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With no atmosphere to push back on the outside of the tires, the tubes would pop. You'd need to run solid tires. Or some kind of non-solid tire that doesn't rely on air pressure....
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Old 10-21-10, 09:53 AM   #6
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With no atmosphere to push back on the outside of the tires, the tubes would pop. You'd need to run solid tires. Or some kind of non-solid tire that doesn't rely on air pressure....
If the bead of the tire is strong enough, it would be no problem. And if a regular tire can hold 100 lbs of pressure, it should be no problem if you don't have the 15 lbs of counter-pressure provided by the atmosphere. Given the moon's gravity, 85 lbs of pressure could work fine.
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Old 10-21-10, 10:25 AM   #7
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If the bead of the tire is strong enough, it would be no problem. And if a regular tire can hold 100 lbs of pressure, it should be no problem if you don't have the 15 lbs of counter-pressure provided by the atmosphere. Given the moon's gravity, 85 lbs of pressure could work fine.
Actually, if your tire takes 100 lbs of pressure, that means it takes 100 lbs of overpressure -- so the real pressure inside is 115 lbs.

If you pumped it up inside your spaceship with one ATM of pressure to 100 psi, and took it outside, the pressure would then be 115 PSI -- so you'd probably want to pump it up to 85 psi inside then take it out, where they'd be at 100 psi.

But ultimately your tires would not care about the lack of atmosphere -- they'd just contain a bit less air to make the overpressure match what they're rated at. Given the moon's gravity, you could probably pump this tire to 1/6th the normal amount -- a mere 16 PSI overpressure -- and have the same amount of deformation, but you'd probably want to go higher than that just to reduce your rolling resistance since that's going to be what slows you down here, where it's air resistance that does it on the Earth. Also, since your speed could be so much higher, and yet your inertia the same -- any bumps you hit you'd hit would be as bad as they are here, or much worse due to a higher speed, so you'd want a high pressure to avoid pinch flats.

As for your bike, being in a space suit you'd want it to be as upright as possible, and with no atmosphere there's no advantage to being scrunched over anyways. Big ape-hanger bars would make sense!

If somebody paved a long road and your bike was geared appropriately and your suit didn't make it too hard to move, even a non athlete could probably hit 100 mph easily. Braking would be difficult, as you'd only have one sixth the stopping power -- so at that speed, it might take a very long time to stop, for example it would take over sixty times as long to stop as it would to stop from 30 mph down here. ("Over" because even air resistance isn't slowing you down like it does on the Earth.)

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Old 10-21-10, 10:37 AM   #8
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For the bike to work in vacuum on the moon, it's going to require special lubricants for the drivetrain... I remember reading that moving parts for robotic instruments and astronaut power tools require specially-formulated lubes that do not evaporate away in vacuum.

The lunar regolith might present a bit of challenge too. From what I hear that dust is extremely abrasive. Probably gotta inspect the drivetrain components (chainrings, derailleurs, cassette and chain) every few days.

As far as tires go, maybe special metal-mesh sprung tires like what they put on the Moon Buggy? Those seem to give pretty good traction and suspension on the Apollo missions. No need to pump air.

We all seen the footage of one of the Apollo astronauts losing his footing and bouncing around when he fell. I guess the upside of riding a bike on the moon is no road rash if you crash! (assuming your space suit remains intact!)

Just my musings after coming back from the Apollo Lunar Module exhibit at the Cradle of Aviation Museum here on Long Island (where Grumman built the LEM!)
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Old 10-21-10, 11:29 AM   #9
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The atmosphere is 1% as thick as ours, so you'd still need a space suit.
yeah, i know you'd need a space suit of some sort on mars, but i was watching some cable TV show about living on mars and the program made the claim that because mars has an atmosphere, albeit a very thin one, that the space suits needed to explore mars would not need to be nearly as bulky and cumbersome as those designed for the total vacuum on the surface of the moon. i'm certainly no expert in these matters so i have no idea if that's true or not.
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Old 10-22-10, 12:30 PM   #10
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As for your bike, being in a space suit you'd want it to be as upright as possible, and with no atmosphere there's no advantage to being scrunched over anyways. Big ape-hanger bars would make sense!
Or a recumbent.
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Old 10-22-10, 10:40 PM   #11
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This looks moon-ready (almost). The lube problem is an issue- this might be a good application of a belt drive.

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Old 10-23-10, 03:13 AM   #12
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A lunar bike would be fairly similar to a bike suitable for riding along a beach: Very fat tyres, carbon drive, teflon-impegnated plastic bearing surfaces rather than metal balls in grease. Lunar travellers are probably better off with pogo sticks but Martians could make much better use of bikes.
Given the cost of hauling weight into orbit and the tight weight budgets, the bikes would have to be weight-weenie light. I would imagine a 1990s style carbon monocoque frame with massive bottom bracket shell, integrated seatpost and saddle, stem/bar unit to reduce the number of bolts.
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Old 11-27-10, 03:48 PM   #13
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I think I may have found the grand-daddy of all lunar bicycle references, from Robert Heinlein of course.

...all the prospectors took bicycles along as a matter of course, just as they carried climbing ropes and spare oxygen...
The solitary prospector, deprived of his traditional burro, found the bicycle an acceptable and reliable, if somewhat less congenial, substitute. A miner's bike would have looked odd in the streets of Stockholm; over-sized wheels, doughnut sand tires, towing yoke and trailer, battery trickle charger, two-way radio, saddle bags and Geiger-counter mount made it not the vehicle for a spin in the park - but on Mars or on the Moon it fitted its purpose the way a canoe fits a Canadian stream.


From The Rolling Stones, by Robert Heinlein.
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