Why goto the Moon, and Not Mars??

Originally posted by Murcielago

Originally posted by Ess Why Kay

wrong, wrong, and wrong.
We can get to Mars in 7 months, the longest a single person has being in space in over 1 year and 2 months...nearly twice as long as the Mars trip would take.

Yes, but we'd need to come back to Earth, making it 14 months.

So? Would the people come back weaker then when they left earth...Yes, would they die from it...No. and after there trip they will gradually regain much of what they lost if they work out.

However if we go to Mars, i'm sure we will have a part of the craft be artificial gravity, done by centrifugal force.

But as for "far-out" thinking concepts...my fav is the MagBeam, which could get a crew to Mars in just 45 days! so a trip there and back is a mere 3 months.

Centrifugal force on a mission to Mars. This is going to be hard to control. I would imagine that you would need some sort of stabalizing effect, such as another mechanical device offsetting the larger centrifugal force so the spacecraft does not fly chaotically offcourse.

Originally posted by Murcielago

Frosty
EDIT: How long will the total voyage be for the astronauts, and does anyone know what the longest time spent in space is?

I answered both of those questions allready...good to see you read everyones posts.

I am talking about a round trip voyage including time spent on Martian surface, not just the one way ticket to the planet. Do you or does anyone else happen to know what this would be?

Originally posted by Frosty
Centrifugal force on a mission to Mars. This is going to be hard to control. I would imagine that you would need some sort of stabalizing effect, such as another mechanical device offsetting the larger centrifugal force so the spacecraft does not fly chaotically offcourse.

How would it affect the ship and cause it to go offcourse? I'm not saying you're wrong. I wasn't aware that it would affect the whole ship, if part of it was rotating.

It is going to be extremely cold on Mars and their will be no oxygen to breathe.

There is actually diatomic oxygen in the atmosphere found by the Viking missions at .13% concentration. It is low concentration, but it is there and all you would need is to concentrate it 100 fold.

It isn't actually that cold on Mars. The mean temperature is -81° F, with the max ever observed at 68° F and minimum ever observed at -220° F. To compare Earth has been down to -128 degrees, which is lower than the mean temperature on Mars. The mean winter temperatures at the South Pole for a winter on Earth can range from -40 F to -94 F. Temperature wise, surviving on Mars would be like surviving at the South Pole in a somewhat bad winter. There is permanent research stations in Antarctica. It would be even easier if you land at places/times with higher than mean temperatures like summer time and when the orbit (pretty elliptical for a planet) is closest to the sun.

Compared to the Moon, Mars is very hospitable. In the long term, it might be easier to live on Mars than on the Moon.

Centrifugal force on a mission to Mars. This is going to be hard to control. I would imagine that you would need some sort of stabalizing effect, such as another mechanical device offsetting the larger centrifugal force so the spacecraft does not fly chaotically offcourse.

Space-craft without humans can be spin stabilized anyway. The rotational momentum actually helps to resist small forces in space that might throw it off over time. This is like a football, and like a football, you want a good spin on the ball so it resist forces that would offset its nice smooth aerodynamic direction.

Centrifugal artificial gravity is actually really easy to control and really easy to do. To resist drag between the spinning and non-spinning parts, you can either have the whole spacecraft spin (which has been done for half a century), or have one habitation section spin with a either direct contact between the parts (hopefully with minimal friction) or perhaps have it guided by electromagnetic forces and no contact. The electromagnetic force would not have to be very big to correct the relative alignment of the two parts without contact.

Originally posted by jra

Originally posted by Frosty
Centrifugal force on a mission to Mars. This is going to be hard to control. I would imagine that you would need some sort of stabalizing effect, such as another mechanical device offsetting the larger centrifugal force so the spacecraft does not fly chaotically offcourse.

How would it affect the ship and cause it to go offcourse? I'm not saying you're wrong. I wasn't aware that it would affect the whole ship, if part of it was rotating.

Well, even if the whole vessel is rotating, wouldn't a slight enequality in the distribution of weight cause the craft to alter its trajectory? I would think so. Say for instance that the south end of the wheel is heavier than the east end, this could cause a distubance in it intentional path.

Would the astronauts even feel the affects of this centrifugal force? Might they be traveling relative to the ship already and never experience the artificial gravity?

Originally posted by kilendrial

Centrifugal artificial gravity is actually really easy to control and really easy to do. To resist drag between the spinning and non-spinning parts, you can either have the whole spacecraft spin (which has been done for half a century), or have one habitation section spin with a either direct contact between the parts (hopefully with minimal friction) or perhaps have it guided by electromagnetic forces and no contact. The electromagnetic force would not have to be very big to correct the relative alignment of the two parts without contact.

What research has been conducted to suggest this?

Originally posted by Frosty
Well, even if the whole vessel is rotating, wouldn't a slight enequality in the distribution of weight cause the craft to alter its trajectory? I would think so. Say for instance that the south end of the wheel is heavier than the east end, this could cause a distubance in it intentional path.

Would the astronauts even feel the affects of this centrifugal force? Might they be traveling relative to the ship already and never experience the artificial gravity?

Well I guess it depends on how they design the ship, but I'd image it would be balanced on all sides. I don't think a slight inequality would affect it either.

I don't know if I completely understand what you mean in your second paragraph. You think that with the ship traveling in one direction while spinning. The astronauts wouldn't feel the centrifugal force? Why wouldn't they?

Well, even if the whole vessel is rotating, wouldn't a slight enequality in the distribution of weight cause the craft to alter its trajectory? I would think so. Say for instance that the south end of the wheel is heavier than the east end, this could cause a distubance in it intentional path.

Conservation of momentum forbids any direct alteration of trajectory because of internal movement of an object. Unless you are shooting something (particles from a rocket) permanently out somewhere else, internal workings will have an equal and opposite reaction to any action. It can alter the orientation of the aircraft which with thrust can alter the course of the spacecraft. 3-axis stabilization uses fly-wheels in the space-craft and stores whatever rotational momentum desirable in those taking it away from the spacecraft. If you have a rotating torus-shaped area for artificial gravity, and one side has more weight, you will get a pull to the heavier side because all the mass is continually “trying” to fly away, but is restrained. Stopping the parts from leaving creates a pull on the space craft. This would create a wobble in the spacecraft if the weight distribution was uneven but the rotation of the force vector will be equally in all directions over time, if uneven in a certain moment. You can compensate a few different ways. Put the rotating object at the center of mass of the over-all spacecraft so the force to a side doesn’t change the angle that the spacecraft is pointing at. You can also use pumps to control weight distribution in the space-craft and use laser telemetry to figure out in what area the weight is skewed. You can not care for the orientation of the space-craft until you apply thrust and then you just have to use thrusters to get into the right orientation. If your space-craft is big enough, it can absorb the momentum of people moving themselves and equipment around in the artificial gravity section without much change.

Would the astronauts even feel the affects of this centrifugal force? Might they be traveling relative to the ship already and never experience the artificial gravity?

Ok, you have a rocket that shoots you into space. You are traveling as fast as the ship. The ship isn’t pushing against you and you aren’t pushing against when the craft isn’t thrusting so no force is felt. You also have a rotating disk that you are not in contact with and so you don’t inherit its momentum. Your momentum doesn’t change, and you aren’t being pushed against anything, so you don’t feel “gravity”. When you come in contact with the disk, and you hold on (which can be done in space), you start moving in a circle with the disk. To move in the circle, you have to change direction, and to change direction, you need a force put on you towards the center of the circle continually. That force can be thought as “artificial gravity”. So, you can feel the centripetal force from the spinning section if you are in contact with it. Otherwise, you won’t.

What research has been conducted to suggest this?

The mag-rail was developed. That lifts a train of dozens of tons off of the ground without friction. Also, there is space-craft that is designed or being designed that is meant to stay at the same distance from each other.

If you have two unconnected parts of a space-craft with the same direction and velocity already, you don’t need much force to keep it that way. There is some difference in momentum, but that is small, so you don’t need much to compensate. There is solar wind, and interstellar medium drag, and that might effects parts of the ship more than others, so you have to compensate a little for that. But you only need a little bit of compensation.

Lets say you have a 150 pound person in a spinning section that simulates earth gravity, and he moves around. All the other parts of the spinning section are distributed symmetrically in weight so that the center of gravity is in line with the overall larger ship. The man moves around and you get a net 150 pounds of force in the direction that guy is on the ship (ship pushes against man at 150 pounds so that man pushes against the ship at the same amount). This might be a lot for electromagnetic forces (at power levels available in space if nuclear isn't used) to deal with in space, but it could deal with the other forces mentioned quite easily. A counterwieight of 150 pounds of water pumped around the ship into preset containers could take care of the mans weight. Also, if you have enough room between the two sections(rotating, main craft), the force of 150 pounds might not move the much larger disk/torus enough to impact the ship by the time that 150 pounds of force is applied in the opposite direction.

Originally posted by kilendrial
Conservation of momentum forbids any direct alteration of trajectory because of internal movement of an object. Unless you are shooting something (particles from a rocket) permanently out somewhere else, internal workings will have an equal and opposite reaction to any action. It can alter the orientation of the aircraft which with thrust can alter the course of the spacecraft. 3-axis stabilization uses fly-wheels in the space-craft and stores whatever rotational momentum desirable in those taking it away from the spacecraft. If you have a rotating torus-shaped area for artificial gravity, and one side has more weight, you will get a pull to the heavier side because all the mass is continually “trying” to fly away, but is restrained. Stopping the parts from leaving creates a pull on the space craft. This would create a wobble in the spacecraft if the weight distribution was uneven but the rotation of the force vector will be equally in all directions over time, if uneven in a certain moment. You can compensate a few different ways. Put the rotating object at the center of mass of the over-all spacecraft so the force to a side doesn’t change the angle that the spacecraft is pointing at. You can also use pumps to control weight distribution in the space-craft and use laser telemetry to figure out in what area the weight is skewed. You can not care for the orientation of the space-craft until you apply thrust and then you just have to use thrusters to get into the right orientation. If your space-craft is big enough, it can absorb the momentum of people moving themselves and equipment around in the artificial gravity section without much change.

Nice explination. So now in order to compensate for this 'wobble', how much more energy is going to be needed. After what you said, I am predicting something twice the size of the ISS making it to Mars with centrifugal force. I would think nuclear propulsion or something other than the liquid fuel will be needed for any Mars mission.

Would the astronauts even feel the affects of this centrifugal force? Might they be traveling relative to the ship already and never experience the artificial gravity?

Ok, you have a rocket that shoots you into space. You are traveling as fast as the ship. The ship isn’t pushing against you and you aren’t pushing against when the craft isn’t thrusting so no force is felt. You also have a rotating disk that you are not in contact with and so you don’t inherit its momentum. Your momentum doesn’t change, and you aren’t being pushed against anything, so you don’t feel “gravity”. When you come in contact with the disk, and you hold on (which can be done in space), you start moving in a circle with the disk. To move in the circle, you have to change direction, and to change direction, you need a force put on you towards the center of the circle continually. That force can be thought as “artificial gravity”. So, you can feel the centripetal force from the spinning section if you are in contact with it. Otherwise, you won’t.

You are trying to say that you must enter into the rotating body to experience the effects or that the rotating body must be started after the astronaut is inside? To the first question: how would someone get into the wheel, with a space suit?

What research has been conducted to suggest this?

The mag-rail was developed. That lifts a train of dozens of tons off of the ground without friction. Also, there is space-craft that is designed or being designed that is meant to stay at the same distance from each other.


How is friction not occuring? This doesn't seem to hold up with me. Could you explain or post a link?

If you have two unconnected parts of a space-craft with the same direction and velocity already, you don’t need much force to keep it that way. There is some difference in momentum, but that is small, so you don’t need much to compensate. There is solar wind, and interstellar medium drag, and that might effects parts of the ship more than others, so you have to compensate a little for that. But you only need a little bit of compensation.

Lets say you have a 150 pound person in a spinning section that simulates earth gravity, and he moves around. All the other parts of the spinning section are distributed symmetrically in weight so that the center of gravity is in line with the overall larger ship. The man moves around and you get a net 150 pounds of force in the direction that guy is on the ship (ship pushes against man at 150 pounds so that man pushes against the ship at the same amount). This might be a lot for electromagnetic forces (at power levels available in space if nuclear isn't used) to deal with in space, but it could deal with the other forces mentioned quite easily. A counterwieight of 150 pounds of water pumped around the ship into preset containers could take care of the mans weight. Also, if you have enough room between the two sections(rotating, main craft), the force of 150 pounds might not move the much larger disk/torus enough to impact the ship by the time that 150 pounds of force is applied in the opposite direction.

The question I have, is how do you start this wheel without it kareeming off? I would imagine that thrust needs to be applied.

Wait, I still like my idea! In science class, we had a metal pole thingy, and you put a magnet that is round with a hole in the middle goes over it and you push it down, then let go and it shoots up off the pole. Now, magnify this a million times.

a 20mile pole with a device that you can attach a Shuttle to, this way you don't need as large of rockets, or as much fuel, and this way you can use a larger Shuttle that holds more food/water.

Or just make a rocket the size of Rhode Island and duct tape a chair to it. Either way you get into space.

Hmmm... I don't see why having something spinning for artificial gravity would matter. Why's that? They would stop the spin when they needed to do maneuvers! During the majority of the trip, the straight line from Earth to Mars, they could be under spin. Once they came to the point of maneuvers, it could be stopped and all could be done well.

Anyway, let's get this back on topic.

[edit on 10/24/2005 by cmdrkeenkid]

Back on topic, the reason to go to the moon first (or the ISS either for that matter) is to accumulate the resources needed for a round trip to Mars. We do not have, nor are we currently planning to build, a spacecraft capable of going directly to Mars from Earth that is capable of carrying a crew of humans. The total amount of resources required to support a single human being for an extended duration in space is horrendous. Further, if attempting to go directly from Earth, or from the ISS, all those resources have to be boosted up out of Earth's gravity well. Since no current, or planned, spacecraft can carry all the required resources in a single trip, several trips are needed. The larger the crew the greater the number of trips needed.

It doesn't take many trips up from Earth to add up to a sizeable, expensive effort. If, on the other hand, those resources were being boosted up from the Moon instead of Earth only 1/6 th. the energy is needed to get them to some assembly point. Assuming that the most expensive resources to get to the assembly point are going to be the spacecraft itself plus fuel and water, and further assuming that those resources (or at least a goodly percentage of them) are available on the Moon, it becomes more economical to acquire them there and send them to the assembly point than to try to boost them up from Earth. I haven't attempted a break-even analysis for the Moon -vs- Earth, but I'm sure NASA has and has concluded its cheaper to start from the Moon--if fuel & water are available on the Moon. If, in addition to fuel & water other needed resources can be had on the Moon the picture just keeps improving.

Now, factor in the need for more than one spacecraft & crew, or the desire to send spacecraft to locations other than Mars and it becomes obvious why the Moon is the correct place to start interplanetary journeys from.



[edit on 24-10-2005 by Astronomer68]