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There's something I always asked myself about Mars expedition: well I kind of believe that it's possible to put somebody down on Mars within the next few decade

There's something I always asked myself about Mars expedition: well I kind of believe that it's possible to put somebody down on Mars within the next few decades. But... what about coming back to earth? Escape velocity is about > 5 km/s. Wouldn't you need to build a launch site having at least half of the power of our launch sites down here on Earth? How are they going to do that anytime near in the future? So is it going to be a on-way trip? And if so, are they going to maintain a supply chain from Earth to Mars for the whole of the life time of those explorers? Water, air, food...

mmanfrin 12y ago
I imagine water can be got from Mars (as there is Ice on Mars), and from that plants can grow, which will produce both air and food.
- crpatino 12y ago
  That would be a bummer for those personally involved wouldn't it? From astronaut to subsistence farmer. At least somebody would make lots of money from the reality TV show that ensued.
  - lucaspiller 12y ago
    There's not much you can spend it on there. I'm guessing Amazon shipping fees would be pretty high too.
- Amezarak 12y ago
  > I imagine water can be got from Mars (as there is Ice on Mars), and from that plants can grow, which will produce both air and food. I am doubtful there is enough air on Mars to sustain any Earth vegetation. The mean surface pressure on Mars is 0.6% that of Earth. Mars has virtually no atmosphere.
MattHeard 12y ago
Has there been any research into remotely building launch sites?
pmontra 12y ago
Most of the mass (fuel) will be waiting in orbit. They need to bring down to the surface only the fuel to get back to orbit so they won't need half of a Saturn V. They still need to launch a lot of fuel from Earth.
- toomuchtodo 12y ago
  Easier to manufacture the fuel on Mars. It only has 40% of Earth's gravity, so easier to lift to waiting orbital fuel depot.
- ifdefdebug 12y ago
  I wasn't thinking about the whole journey back home, just the first part of it which looks damn hard to me: how do you get a space craft away from Mars? You need to reach escape velocity, and that's 5 km/s (> 11000 mph). You'll have to build a complete launch site for that.
  - sfeng 12y ago
    If you have fuel in orbit you just have to reach it, you don't have to get to escape velocity.
    - ifdefdebug 12y ago
      OK, got that. Did some further reading (again) on the topic and it's still about 4 km/s to reach the orbit. People are working on it, but for what I read it looks hard to overcome for 2030...
    - rspeer 12y ago
      You still have to match velocity with the fuel. Crashing into your fueling station at 10000 km/h doesn't help anything.
      - LyndsySimon 12y ago
        Actually... it completely solves the problem of the return trip.
facepalm 12y ago
Well as you could see in the movie "Interstellar", once you have left the earth you can just zip around everywhere with your little space dinghy :-)
- sytelus 12y ago
  I don't know if lot of people realize this but you don't "leave" Earth just in low orbit or even significantly higher up. In fact the actual gravitational force at the level of ISS is almost same as on surface. The reason you "feel" zero gravity is not because you are so far from Earth but because you have acquired so much velocity that you fall with same acceleration as other falling objects. This is equivalence principal that creates feeling of weightlessness. But objects at that height otherwise feel pretty much same pull of gravity as us on surface.
Galaxeblaffer 12y ago
On the bright side, you only have to send the people and not all the gear, so much less weight to accelerate. I couldn't find something to indicate how much less fuel you would need to send only a few people with an earth reentry capsule. you would of course need air and supplies for 200-300 days hmm.. I guess it will be somewhat a problem anyways..
sytelus 12y ago
This is why sending humans to Mars is stupid - at least in our current resource and energy constrained world. Humans requires suits, food, air, water, health support, housing, massive infrastructure to return back and so on. On the other hand, they don't contribute much more in terms of sensors or agility. I know most of you are now super uncomfortable reading this and you want to be poetic and tell me all about spirit of adventure and what not. But get this: We need to make best out of our resources and technologies. We can have self driving cars and robots working in warehouses and delivering pizza. Why do we really need humans on Mars? I'm all of sending humans to Mars once we have found almost unlimited resorvoir of enery and world GDP has increased to point where we don't know what to do with all the excess. But until then let's send 100s of robots to mars, let's survey as much land there as possible, may be establish robot colony there, send robots with more and better sensors. May be robots can even build there biosphere first over years to prepare arrivals of humans. That would be much better use of our limited resources.

mmanfrin 12y ago

I imagine water can be got from Mars (as there is Ice on Mars), and from that plants can grow, which will produce both air and food.

crpatino 12y ago
That would be a bummer for those personally involved wouldn't it? From astronaut to subsistence farmer. At least somebody would make lots of money from the reality TV show that ensued.
- lucaspiller 12y ago
  There's not much you can spend it on there. I'm guessing Amazon shipping fees would be pretty high too.
Amezarak 12y ago
> I imagine water can be got from Mars (as there is Ice on Mars), and from that plants can grow, which will produce both air and food. I am doubtful there is enough air on Mars to sustain any Earth vegetation. The mean surface pressure on Mars is 0.6% that of Earth. Mars has virtually no atmosphere.

MattHeard 12y ago

Has there been any research into remotely building launch sites?

pmontra 12y ago

Most of the mass (fuel) will be waiting in orbit. They need to bring down to the surface only the fuel to get back to orbit so they won't need half of a Saturn V. They still need to launch a lot of fuel from Earth.

toomuchtodo 12y ago
Easier to manufacture the fuel on Mars. It only has 40% of Earth's gravity, so easier to lift to waiting orbital fuel depot.
ifdefdebug 12y ago
I wasn't thinking about the whole journey back home, just the first part of it which looks damn hard to me: how do you get a space craft away from Mars? You need to reach escape velocity, and that's 5 km/s (> 11000 mph). You'll have to build a complete launch site for that.
- sfeng 12y ago
  If you have fuel in orbit you just have to reach it, you don't have to get to escape velocity.
  - ifdefdebug 12y ago
    OK, got that. Did some further reading (again) on the topic and it's still about 4 km/s to reach the orbit. People are working on it, but for what I read it looks hard to overcome for 2030...
  - rspeer 12y ago
    You still have to match velocity with the fuel. Crashing into your fueling station at 10000 km/h doesn't help anything.
    - LyndsySimon 12y ago
      Actually... it completely solves the problem of the return trip.

facepalm 12y ago

Well as you could see in the movie "Interstellar", once you have left the earth you can just zip around everywhere with your little space dinghy :-)

sytelus 12y ago
I don't know if lot of people realize this but you don't "leave" Earth just in low orbit or even significantly higher up. In fact the actual gravitational force at the level of ISS is almost same as on surface. The reason you "feel" zero gravity is not because you are so far from Earth but because you have acquired so much velocity that you fall with same acceleration as other falling objects. This is equivalence principal that creates feeling of weightlessness. But objects at that height otherwise feel pretty much same pull of gravity as us on surface.

Galaxeblaffer 12y ago

On the bright side, you only have to send the people and not all the gear, so much less weight to accelerate. I couldn't find something to indicate how much less fuel you would need to send only a few people with an earth reentry capsule. you would of course need air and supplies for 200-300 days hmm.. I guess it will be somewhat a problem anyways..

sytelus 12y ago

This is why sending humans to Mars is stupid - at least in our current resource and energy constrained world. Humans requires suits, food, air, water, health support, housing, massive infrastructure to return back and so on. On the other hand, they don't contribute much more in terms of sensors or agility. I know most of you are now super uncomfortable reading this and you want to be poetic and tell me all about spirit of adventure and what not. But get this: We need to make best out of our resources and technologies. We can have self driving cars and robots working in warehouses and delivering pizza. Why do we really need humans on Mars? I'm all of sending humans to Mars once we have found almost unlimited resorvoir of enery and world GDP has increased to point where we don't know what to do with all the excess. But until then let's send 100s of robots to mars, let's survey as much land there as possible, may be establish robot colony there, send robots with more and better sensors. May be robots can even build there biosphere first over years to prepare arrivals of humans. That would be much better use of our limited resources.