I just heard that the tires on the lunar rover were made from wire mesh because normal air filled tires would explode since there was no atmosphere. Why would having no atmosphere affect a sealed tire? Being a diver I know that air expands and tires that are filled at earths 1atm would explode, but if the tires were near empty when going into space, would they not expand to the ideal trie pressure etc?
In a vacuum, the smallest bit of air would inflate the tire quite a bit, AFAIK. Maybe enough to burst it. A non-inflated/solid tire would avoid this problem.
Unless I’m missing something, having tyres in a vacuum is the equivalent of putting an extra bar of pressure inside them, i.e. an extra 15 psi. I don’t think you would burst any conventional vehicle tyre by doing that.
Broadly speaking, the only thing that matters with regard to inflation of the tyres is the difference between internal and external pressure, so you could use pressurised tyres in a vacuum, you just need to put less air in them to inflate them.
In practical terms though, rubber tyres might just not work very well in the environment of the lunar surface; although there’s no actual ambient temperature, because there’s little or no atmosphere, it’s really hot in the sun and really cold in the shade, and for a thin sheet of rubber under pressure and constantly under stress of deformation from actual use, it might just be too much. solid rubber tyres might be able to handle this for the duration of the mission, but they’d be much heavier.
It wasn’t just a matter of an air-filled tire exploding.
Any pneumatic tire design would have been unnecisarily heavy. Given the low speed, low gravity, and limited endurance needed, a wiremesh tire provided the ideal strength to weight ratio.
Mangetout, it seems to me that you are totally correct…but the program i was watching clearly said that due to the atmosphere (or lack of), the tires would have exploded, and so they couldnt use air filled tires. thats what caught me off guard…
There might be a smidgen of fact in there though; on the launchpad, the vehicle was subject to atmospheric pressure; on the moon (and on the journey there), it was in near total vacuum, the transition from our atmosphere to space could have caused overinflation; this could be resolved in a couple of ways (each with their own individual disadvantages).
-Design the tyres to be able to withstand a wider range of inflation pressures (in which case they’d probably be heavier)
-Launch with the tyres completely uninflated and pump them up when you get there (but the inflation equipment is extra weight)
-Launch with the tyres underinflated by just the right amount to compensate for the change in ambient pressure (Inflation at any point during the mission is a potential point of failure)
All in all, the choice of mesh tyres was an inspired and elegant one; solving many problems all at the same time.
1.) My recollection was that the lunar vehicle tires were essentially spirals of metal, not “metal mesh”.
2.) I always felt that the reason they used metal “tires” was because they were operating in vacuum, in temperature extrenmes, and in unfiltered sublight (not atmosphere to block it), just filled with hard UV rays. All of thes things are hell on rubber or any synthetic polymer. I always assumed that the use of pure metal was to avoid the deterioration that would inevitably come to rubber/plastic is such a harsh environment.
there’s a fairly good photo here - it looks like they are constructed as a spiral lattice of springy strips covered by an outer mesh layer.
Another picture that clearly shows the mesh.
That doesn’t look clear at all, it looks tiny.
The google thumbnail does, but the page below it is this one, with quite a clear image.
On Apollo 14, the astronauts used the Mobile Equipment Transporter, an unpowered cart for carrying tools and samples and used as a mobile work surface. It used inflated rubber tires.
Photo Here:
It’s not hard to design an inflated rubber wheel that can hold up to lunar surface conditons. The lunar rover used open mesh wheels for weight reasons, not because they couldn’t make rubber wheels that would survive.
They look like rubber to me! 
But seriously, here’s another close-up of the rover tire (Apollo 17).
The answer, as some have already said, is to reduce weight and ensure reliability; AAA coverage doesn’t extend to Selene. For long term exposure to vacuum and unfiltered sunlight (as the Rover was designed to be left in place to be potentially used on later missions) there may have been some consideration to the embrittlement of elasomers, but there are glass fabrics, such as those used in pressure suits, that could have been used if a pressurized tire was desired.
Here is a simple graphic of the Rover that clearly indicates the wire-mesh wheels.
Stranger
Pffft! Could have at least sprung for the whitewalls.
“Everybody remember where we parked! Taurus-Littrow Green!”
Wire mesh tires don’t get flat.
Can YOU easily change a flat wearing a spacesuit?
IIRC, the reason they didn’t use rubber was not because of a danger of bursting, but because the volatile organic compounds that normally preserve the softness of rubber tend to “boil” away quickly in the near-vacuum of space, leaving a tire much more vulnerable to cracking and leaking.
Here’s a cite from NASA that appears to back me up:
Sort of like why you have to replace winter tires every 3 years whether they appear to be worn or not.
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- Also we note (mentioned in another thread) that the daytime/nighttime temperatures on the surface of the moon are +200C/-100C. A pretty broad temperature range for rubber. It might be possible to make some sort of “soft” material now, as I’ve seen little soft-silicone dishes that can be used to bake in–are labelled as safe up to 500F–but I dunno what they would do at -200F…
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- Also we note (mentioned in another thread) that the daytime/nighttime temperatures on the surface of the moon are +200C/-100C. A pretty broad temperature range for rubber. It might be possible to make some sort of “soft” material now, as I’ve seen little soft-silicone dishes that can be used to bake in–are labelled as safe up to 500F–but I dunno what they would do at -200F…
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Many TV and other documentaries use careful background research of the “making it up” type to provide explanations such as this. Or more likely, the “correct” answer was so obvious to the writer that he/she never bothered to actually check it out.