A manned mission to Mars and its obstacles

[ladykrimson]

I know there are many obstacles in the way of sending a manned mission to Mars, as described by Chronos in the "High School Debate" thread. I have a few questions of my own about ideas that will help to overcome these obstacles.

1. The weightlessness is one of the big barriers. I have seen some suggestions to spin the ship on the way to Mars, in order to simulate gravity for the crew. It seems like a sound method to me and fairly easy to enact. What are the complications or problems for this method?

2. Necessary supplies will weigh the ship down, making it difficult to launch from Earth. It has been suggested to build a spacecraft in orbit and then send supplies up with other manned missions. When the spacecraft is built and supplied, the astronauts could then launch in a smaller craft and dock with the larger craft. Aside from the cost, what are complications or problems with this suggestion?

3. I have searched many places, but I can't find an answer to this. Have humans discovered a way to generate an electro-magnetic shield? If so, could this be applied to the ship with the manned mission to Mars? I realize that it wouldn't be as powerful as Earth's, but could it, at least, provide some protection?

4. Enough fuel to get to Mars and then return would weigh down the ship. Is it possible to fuel the ship in orbit with the necessary amount of fuel? Why don't we have some type of fueling station already in orbit? Wouldn't that be an economical investment if humans intend to explore space further or even sending out more probes?

5. Just like on the moon, why are we not sending some kind of probe in advance of the mission to collect some Martian samples and return them to Earth? That way, NASA could get an idea of what it takes to land a craft safely on Mars and launch from Mars safely.

 

[Nabeshin]

1. The weightlessness is one of the big barriers. I have seen some suggestions to spin the ship on the way to Mars, in order to simulate gravity for the crew. It seems like a sound method to me and fairly easy to enact. What are the complications or problems for this method?

The objection to this one is that in order to get an appreciable gravity, you need to either have a very large object or make it rotating very quickly. The problems with either of these are quite obvious, so it's actually not that easy to enact this one.

2. Necessary supplies will weigh the ship down, making it difficult to launch from Earth. It has been suggested to build a spacecraft in orbit and then send supplies up with other manned missions. When the spacecraft is built and supplied, the astronauts could then launch in a smaller craft and dock with the larger craft. Aside from the cost, what are complications or problems with this suggestion?

Nothing's wrong with it. A mission to Mars would take a long time, and likely require a spacecraft much larger than we've currently seen. It's therefore necessary that it be assembled in orbit, much in a similar way the ISS has been. It's much cheaper to do it in this piecewise fashion than to launch the whole thing in one go.

3. I have searched many places, but I can't find an answer to this. Have humans discovered a way to generate an electro-magnetic shield? If so, could this be applied to the ship with the manned mission to Mars? I realize that it wouldn't be as powerful as Earth's, but could it, at least, provide some protection?

Well, lead makes a pretty good EM shield. Or any metal, really. The issue is just one of weight and practicality. As far as trying to generate an E-M field like the Earth's, that's much more difficult. Likely, any device powerful enough to provide significant protection would also wreck serious havoc on the spacecraft itself!

4. Enough fuel to get to Mars and then return would weigh down the ship. Is it possible to fuel the ship in orbit with the necessary amount of fuel? Why don't we have some type of fueling station already in orbit? Wouldn't that be an economical investment if humans intend to explore space further or even sending out more probes?

Like I said in response to 2, you pretty much must construct the craft in orbit. At any rate, you still have to ship the fuel to LEO or some similar orbit, which is still a costly endeavor. So unless you could manufacture the fuel already in space (and I know of no practical way to do so), it's not that much better.

5. Just like on the moon, why are we not sending some kind of probe in advance of the mission to collect some Martian samples and return them to Earth? That way, NASA could get an idea of what it takes to land a craft safely on Mars and launch from Mars safely.

The moon is very very much closer than mars. Not only that, it's also much less massive. Not to imply that Mars is huge, but it takes significantly more thrust to lift off of Mars than it does to lift off of the moon. So to get back is a much bigger undertaking. It makes good sense to perhaps try to get a craft back from Mars from a learning perspective, but economically you probably more than double the cost of the mission. We already know how to land on mars, and we've taken off the moon, so I would think it's just a problem of scaling in taking off.

 

[ladykrimson]

The objection to this one is that in order to get an appreciable gravity, you need to either have a very large object or make it rotating very quickly. The problems with either of these are quite obvious, so it's actually not that easy to enact this one.

About how quickly would it have to rotate to produce appreciable gravity?

Nothing's wrong with it. A mission to Mars would take a long time, and likely require a spacecraft much larger than we've currently seen. It's therefore necessary that it be assembled in orbit, much in a similar way the ISS has been. It's much cheaper to do it in this piecewise fashion than to launch the whole thing in one go.

OK, that is good to know.

Well, lead makes a pretty good EM shield. Or any metal, really. The issue is just one of weight and practicality. As far as trying to generate an E-M field like the Earth's, that's much more difficult. Likely, any device powerful enough to provide significant protection would also wreck serious havoc on the spacecraft itself!

Wow, I never even thought of that aspect. An EM field would have repercussions on the computer equipment on the spacecraft . So the problem is to find a material that can protect from radiation but is not too heavy or not practical.

Like I said in response to 2, you pretty much must construct the craft in orbit. At any rate, you still have to ship the fuel to LEO or some similar orbit, which is still a costly endeavor. So unless you could manufacture the fuel already in space (and I know of no practical way to do so), it's not that much better.

Well, if the spacecraft is going to be built in space, that means that parts and equipment will need to be delivered several times. Why not start stocking up on fuel at the same time?

The moon is very very much closer than mars. Not only that, it's also much less massive. Not to imply that Mars is huge, but it takes significantly more thrust to lift off of Mars than it does to lift off of the moon. So to get back is a much bigger undertaking. It makes good sense to perhaps try to get a craft back from Mars from a learning perspective, but economically you probably more than double the cost of the mission. We already know how to land on mars, and we've taken off the moon, so I would think it's just a problem of scaling in taking off.

Economically, it would increase the cost, but things are not always what we expect when humanity leaps into these endeavors. Each time we have sent a craft to a different planet or moon, we discover something about the destination that is completely different than what we expected. What if there is some incalculable factor that prevents a craft from lifting off from Mars? Do we wait until humans are there to discover it?

 

[Nabeshin]

About how quickly would it have to rotate to produce appreciable gravity?

see: http://en.wikipedia.org/wiki/Artificial_gravity

Economically, it would increase the cost, but things are not always what we expect when humanity leaps into these endeavors. Each time we have sent a craft to a different planet or moon, we discover something about the destination that is completely different than what we expected. What if there is some incalculable factor that prevents a craft from lifting off from Mars? Do we wait until humans are there to discover it?

Of course, these are famous last words, but I don't think there's much unexpected in lifting off from mars. There are complications with the martian atmosphere and weather, perhaps, but I can't think or anything that would be terribly difficult. You might say, "well we don't know everything so there always could be something that would make it hard," and while true, at some point you have to assess your knowledge as sufficient and give it a go...

Really, these questions could be much better answered by lots of others here on the forums, I don't really deal with this planet stuff myself :)

 

[Chronos]

While I am still stuck on economics, we still need to learn a lot more about the practical side of planetary exploration before sending humans on a 2 year space mission. The death of the crew on a first mission to Mars would be a political nightmare. Probes must come first, IMO. We need to thoroughly explore every aspect and practicality of a Mars mission before rolling the dice on a manned mission.

 

[ladykrimson]

While I am still stuck on economics, we still need to learn a lot more about the practical side of planetary exploration before sending humans on a 2 year space mission. The death of the crew on a first mission to Mars would be a political nightmare. Probes must come first, IMO. We need to thoroughly explore every aspect and practicality of a Mars mission before rolling the dice on a manned mission.

I agree that probes should definitely come first; however, we can't hold off forever on a manned mission to Mars. Some of the techniques we learn for space travel are learned on the actual missions. If we look at the event with Alexei Leonov, that is how we learned that space suits needed to be pressurized due to the vacuum of space.