5 ms·

I'm no expert at all, but three things come to mind: - Mars has a (thin) atmosphere, mostly made up of CO2 -> good for plant growth. The Moon has none. - Mars

by jrv 10y ago

I'm no expert at all, but three things come to mind: - Mars has a (thin) atmosphere, mostly made up of CO2 -> good for plant growth. The Moon has none. - Mars has gravity closer to Earth than the Moon. - Mars has lots of water, while the moon has possibly just a little? EDIT: found http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not-another-planet http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not..., which cites similar and more reasons (although Mars One seems to be pretty much a scam).

bergie 10y ago
The Martian atmosphere also makes aerobraking possible, meaning spacecraft arriving there need less delta-V. A Dragon2 can land in Mars, but not on the Moon because of this.
- exDM69 10y ago
  Aerobraking is a benefit but is the Dragon really unable to land on the moon? The moon has less gravity (about half) and the velocity difference should be much smaller for a lunar intercept than a Mars intercept. Has anyone got numbers for this?
  - lmm 10y ago
    Dragon doesn't have enough delta-V to land on the moon. The plan for a Mars landing is to use it as a lifting body to keep it above the ground for long enough to shed most of its velocity.
    - exDM69 10y ago
      Yes, GP said that already but I'm after the numbers here. How much delta-v the Dragon has? And what are the approximate requirements for Moon vs. Mars landing?
      - Symmetry 10y ago
        The Dragon 2 has about 1.6 km/s. Apollo had 2.47 km/s to land and 2.22 km/s to take off. Oh, and it would take on the order of 4.5 km/s to take off from Mars and maybe a few hundred to land.
        exDM69 10y ago
        Thanks! These numbers look reasonable to me. Can you provide a link to source (s)? I'd like to read some more...
    - dalke 10y ago
      I've read various statements which say that Dragon can land on the Moon, such as http://www.nbcnews.com/science/space/mars-ahead-spacex-unveils-dragon-v2-capsule-astronaut-trips-n118116 http://www.nbcnews.com/science/space/mars-ahead-spacex-unvei... : > Musk has said a fully loaded Dragon could even be sent to make a touchdown on the moon or Mars or https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dragon-2018-mars-mission/ https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dra... : > “With Dragon launched on a Falcon Heavy, it can go pretty much anywhere in the solar system, because that’s a heck of a big rocket,” he continued. > “Dragon, with the heat shield, parachutes and propulsive landing capability, is able to land on a planet that has higher entry heating, like Mars. It can also land on the Moon, or potentially conduct a Europa mission.” How does that fit with the statement "Dragon doesn't have enough delta-V to land on the moon"?
robbiep 10y ago
'- Mars has gravity closer to the earth than the moon' Depends on what you mean by close. 0.38 is closer to 16.7 than 1, but any improvement on that is important
- Manabu-eo 10y ago
  If you are talking about human health, it might be that any gravity bellow 0.8g is almost as bad for human health as microgravity. It could be that any gravity above 0.1g is as good as 1g for human health. We simply don't know the format of that curve. We have no data on it even on rodents (the ISS module for that was scrapped). We only know that 1g is good and microgravity is bad. And that very high g is bad too.

by jrv 10y ago

bergie 10y ago

The Martian atmosphere also makes aerobraking possible, meaning spacecraft arriving there need less delta-V. A Dragon2 can land in Mars, but not on the Moon because of this.

exDM69 10y ago
Aerobraking is a benefit but is the Dragon really unable to land on the moon? The moon has less gravity (about half) and the velocity difference should be much smaller for a lunar intercept than a Mars intercept. Has anyone got numbers for this?
- lmm 10y ago
  Dragon doesn't have enough delta-V to land on the moon. The plan for a Mars landing is to use it as a lifting body to keep it above the ground for long enough to shed most of its velocity.
  - exDM69 10y ago
    Yes, GP said that already but I'm after the numbers here. How much delta-v the Dragon has? And what are the approximate requirements for Moon vs. Mars landing?
    - Symmetry 10y ago
      The Dragon 2 has about 1.6 km/s. Apollo had 2.47 km/s to land and 2.22 km/s to take off. Oh, and it would take on the order of 4.5 km/s to take off from Mars and maybe a few hundred to land.
      - exDM69 10y ago
        Thanks! These numbers look reasonable to me. Can you provide a link to source (s)? I'd like to read some more...
  - dalke 10y ago
    I've read various statements which say that Dragon can land on the Moon, such as http://www.nbcnews.com/science/space/mars-ahead-spacex-unveils-dragon-v2-capsule-astronaut-trips-n118116 http://www.nbcnews.com/science/space/mars-ahead-spacex-unvei... : > Musk has said a fully loaded Dragon could even be sent to make a touchdown on the moon or Mars or https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dragon-2018-mars-mission/ https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dra... : > “With Dragon launched on a Falcon Heavy, it can go pretty much anywhere in the solar system, because that’s a heck of a big rocket,” he continued. > “Dragon, with the heat shield, parachutes and propulsive landing capability, is able to land on a planet that has higher entry heating, like Mars. It can also land on the Moon, or potentially conduct a Europa mission.” How does that fit with the statement "Dragon doesn't have enough delta-V to land on the moon"?

robbiep 10y ago

'- Mars has gravity closer to the earth than the moon' Depends on what you mean by close. 0.38 is closer to 16.7 than 1, but any improvement on that is important

Manabu-eo 10y ago
If you are talking about human health, it might be that any gravity bellow 0.8g is almost as bad for human health as microgravity. It could be that any gravity above 0.1g is as good as 1g for human health. We simply don't know the format of that curve. We have no data on it even on rodents (the ISS module for that was scrapped). We only know that 1g is good and microgravity is bad. And that very high g is bad too.