4 ms·

Mars doesn't have a thick enough atmosphere for lift, you can fly a copter, but it needs a lot of power to do so and it needs to be light enough to do so. On t

Mars doesn't have a thick enough atmosphere for lift, you can fly a copter, but it needs a lot of power to do so and it needs to be light enough to do so. On the otherhand you probably could get away with a space elevator on Mars where you couldn't on Earth.

Fred34 3y ago
I wonder what's the math on trying to use a huge rail gun on Mars to shoot things into orbit. I know that people have talked about using rail guns on the moon to shoot and other materials ore back to earth (or even to mars) -- but the moon has less of an atmosphere and less of a gravitational pull than mars.
- zizee 3y ago
  This says it's possible: https://space.stackexchange.com/questions/8016/is-a-railgun-up-olympus-mons-possible https://space.stackexchange.com/questions/8016/is-a-railgun-... Note: I cannot vouch for its correctness.
  - Fred34 3y ago
    I'll add that stack-exchange page to my bookmarks thanks.
- colechristensen 3y ago
  The escape velocity for Earth is 11 km/s. The escape velocity for mars is 5 km/s. The situation for a ground launched projectile is of course worse because of air resistance losses. It's still really difficult to accelerate something to 5 km/s. (It's 2.5 km/s on the moon)
  - rtpg 3y ago
    Wikipedia says there are prototype railguns that can shoot at 3km/s now (wording: "can regulary exceed 3km/s")... are we at a point now where I could put a rail gun and a bunch of solar panels and batteries on the moon and just shoot (tiny) stuff into orbit? Not like the rocks on the moon are that useful for anything, but....
    - Fred34 3y ago
      Apparently there is helium-3 on the moon which could be used as a fusion reactor fuel. https://en.m.wikipedia.org/wiki/Helium-3 https://en.m.wikipedia.org/wiki/Helium-3
nickff 3y ago
Honest question here; why would you need more power to fly a helicopter on Mars than on Earth? You’d likely need proportionally larger blades, but less power, as the power goes into providing thrust, which is used to counter gravity (that is lower on Mars). Likewise, conventional aircraft would require longer wingspans, as they’d be flying in lower density air, but they’d also be lighter (less weight). In case it’s not obvious, I suspect that larger wings are required because of the lower density of Mars’ atmosphere, which would increase the stall speed relative to Mach number of any given aircraft.
- samplatt 3y ago
  You're not countering gravity, you're countering the mass of the helicopter vs. the mass of the air moved. Thus, since the air is thinner: to push larger blades going at the same speed, OR the same sized blades going at a faster speed, you'd need more power.
  - nickff 3y ago
    I don’t think you can spin the blades much faster, as Earth-bound helicopters already have issues with blade tip speeds approaching the speed of sound. Short blades are less efficient anyway, and I’m not sure why pushing larger blades will require more power; that would have to do with the balance between density of atmosphere and its viscosity.
    - consp 3y ago
      As a bonus the speed of sound on mars is usually quite a bit lower than on earth, since it's usually colder. Or you'd have to wait for warmer weather at the right spot at the right time.
- colechristensen 3y ago
  Aerodynamic forces are proportional to density. Mars' surface gravity is 1/3 that of Earth's. Mars' surface air density is 1/60 that of earths. So to use lifting surfaces on Mars to fly, the situation is 20x harder. It's roughly equivalent to flying at 40,000 ft on Earth with an electric helicopter. The world record for highest helicopter ever flown is 42,500 ft on Earth. Flying on Mars is like flying more or less at the service ceiling of all but the most specialized aircraft can on Earth, and most of those are air breathing engines. The structural weight required to make equivalent lift to weight ratios (L/W) is very much harder and the lower gravity doesn't make up for most of the difficulty.

Fred34 3y ago

I wonder what's the math on trying to use a huge rail gun on Mars to shoot things into orbit. I know that people have talked about using rail guns on the moon to shoot and other materials ore back to earth (or even to mars) -- but the moon has less of an atmosphere and less of a gravitational pull than mars.

zizee 3y ago
This says it's possible: https://space.stackexchange.com/questions/8016/is-a-railgun-up-olympus-mons-possible https://space.stackexchange.com/questions/8016/is-a-railgun-... Note: I cannot vouch for its correctness.
- Fred34 3y ago
  I'll add that stack-exchange page to my bookmarks thanks.
colechristensen 3y ago
The escape velocity for Earth is 11 km/s. The escape velocity for mars is 5 km/s. The situation for a ground launched projectile is of course worse because of air resistance losses. It's still really difficult to accelerate something to 5 km/s. (It's 2.5 km/s on the moon)
- rtpg 3y ago
  Wikipedia says there are prototype railguns that can shoot at 3km/s now (wording: "can regulary exceed 3km/s")... are we at a point now where I could put a rail gun and a bunch of solar panels and batteries on the moon and just shoot (tiny) stuff into orbit? Not like the rocks on the moon are that useful for anything, but....
  - Fred34 3y ago
    Apparently there is helium-3 on the moon which could be used as a fusion reactor fuel. https://en.m.wikipedia.org/wiki/Helium-3 https://en.m.wikipedia.org/wiki/Helium-3

nickff 3y ago

Honest question here; why would you need more power to fly a helicopter on Mars than on Earth? You’d likely need proportionally larger blades, but less power, as the power goes into providing thrust, which is used to counter gravity (that is lower on Mars). Likewise, conventional aircraft would require longer wingspans, as they’d be flying in lower density air, but they’d also be lighter (less weight). In case it’s not obvious, I suspect that larger wings are required because of the lower density of Mars’ atmosphere, which would increase the stall speed relative to Mach number of any given aircraft.

samplatt 3y ago
You're not countering gravity, you're countering the mass of the helicopter vs. the mass of the air moved. Thus, since the air is thinner: to push larger blades going at the same speed, OR the same sized blades going at a faster speed, you'd need more power.
- nickff 3y ago
  I don’t think you can spin the blades much faster, as Earth-bound helicopters already have issues with blade tip speeds approaching the speed of sound. Short blades are less efficient anyway, and I’m not sure why pushing larger blades will require more power; that would have to do with the balance between density of atmosphere and its viscosity.
  - consp 3y ago
    As a bonus the speed of sound on mars is usually quite a bit lower than on earth, since it's usually colder. Or you'd have to wait for warmer weather at the right spot at the right time.
colechristensen 3y ago
Aerodynamic forces are proportional to density. Mars' surface gravity is 1/3 that of Earth's. Mars' surface air density is 1/60 that of earths. So to use lifting surfaces on Mars to fly, the situation is 20x harder. It's roughly equivalent to flying at 40,000 ft on Earth with an electric helicopter. The world record for highest helicopter ever flown is 42,500 ft on Earth. Flying on Mars is like flying more or less at the service ceiling of all but the most specialized aircraft can on Earth, and most of those are air breathing engines. The structural weight required to make equivalent lift to weight ratios (L/W) is very much harder and the lower gravity doesn't make up for most of the difficulty.