Artificial Gravity and Spacetravel

[Airbrush]

Anyone know if the first manned missions to Mars will have artificial gravity during the long voyage to and from Mars? It seems simple to have a spacecraft designed to rotate and create one g. At least while they are sleeping or their free time they can relax in a one g environment. Is that possible?

 

Anyone know if a centrifuge can be built on the surface of Mars or the Moon where the crew can sleep, or even recreate, in a one g environment?

[mathematic]

I presume a centrifuge could be built. The problem is practicality along with expense.

[Enthalpy]

A centrifuge would be big to achieve 1g with a reasonable angular speed. It has definite drawbacks, as every object and person would feel a strong Coriolis force during any move.

 

I wonder: for what benefit? Humans have already spent 2 years in true zero gravity, hence worse than on the Moon or Mars.

[J.C.MacSwell]

A centrifuge would be big to achieve 1g with a reasonable angular speed. It has definite drawbacks, as every object and person would feel a strong Coriolis force during any move.

 

I wonder: for what benefit? Humans have already spent 2 years in true zero gravity, hence worse than on the Moon or Mars.

How so? The longest continuous time in space is just over 14 months, and only one other time has someone gone more than a year.

 

https://en.wikipedia.org/wiki/List_of_spaceflight_records

[Airbrush]

In all the documentaries I've ever seen about a manned Mars mission, I missed any mention of having the spacecraft rotate creating 1 g. Are the first Mars astronauts just going to get used to zero g's on the trip there and back, and obviously only the small Martian gravity? Seems like over a 2-year mission, there would be significant bone weakening.

Over the long term they should be able to build a giant centrifuge under ground, probably inside a lava tube. It would resemble a giant merri-go-round in the park, but the floor would be angled inward to compensate for the rotation. Then maybe the combined g forces on people would be the Mars tiny gravity, plus the centrifugal force from rotation adding up to 1 g.

Could you please explain how a Coriolis force would be experienced inside the centrifuge?

 

 

 

 

[Janus]

In all the documentaries I've ever seen about a manned Mars mission, I missed any mention of having the spacecraft rotate creating 1 g. Are the first Mars astronauts just going to get used to zero g's on the trip there and back, and obviously only the small Martian gravity? Seems like over a 2-year mission, there would be significant bone weakening.

 

Over the long term they should be able to build a giant centrifuge under ground, probably inside a lava tube. It would resemble a giant merri-go-round in the park, but the floor would be angled inward to compensate for the rotation. Then maybe the combined g forces on people would be the Mars tiny gravity, plus the centrifugal force from rotation adding up to 1 g.

To generate an effective 1g force, the floor would have to be tilted at a angle of 67.8 degrees from the horizontal.(And since the floor is tilted, parts of it will be closer or further than others to the axis of rotation than others and experience less or more lateral g force. Thus, the total g-force will vary from edge to edge, and if you want the floor to remain "level" for the occupants at all points, the floor would have to "curve". By how much depends on how wide you want you floor to be compared to the radius of the centrifuge. )

And just how big do you mean by giant? What radius are we talking about? How wide of a floor? For example, if we give it a 100 m radius(outer edge) and a 10 m width, then the inner edge would feel 0.97g and to be "level" would be tilted at a bit under 67 degrees. A narrower floor would decrease the difference. The outer rim would be moving at 30.13 m/s and it would be rotating at 2.877 rpm

Could you please explain how a Coriolis force would be experienced inside the centrifuge?

The degree would depend on the size of the centrifuge. For example, let's say your spacecraft is 15m in diameter. If we assume a normal 1g weight for someone standing on the inner surface, then I estimate that going from a seated to standing position would result in a Coriolis effect equal to a sideways change in velocity of 1 1/4 mph.

Another interesting point is that, depending on your height, you would weigh roughly 6% more while sitting down than when standing up.(while sitting down your center of mass will be further from the axis of rotation, and where the g force will be stronger)

Edited August 23, 2016 by Janus

[J.C.MacSwell]

To generate an effective 1g force, the floor would have to be tilted at a angle of 67.8 degrees from the horizontal.(And since the floor is tilted, parts of it will be closer or further than others to the axis of rotation than others and experience less or more lateral g force. Thus, the total g-force will vary from edge to edge, and if you want the floor to remain "level" for the occupants at all points, the floor would have to "curve". By how much depends on how wide you want you floor to be compared to the radius of the centrifuge. )

And just how big do you mean by giant? What radius are we talking about? How wide of a floor? For example, if we give it a 100 m radius(outer edge) and a 10 m width, then the inner edge would feel 0.97g and to be "level" would be tilted at a bit under 67 degrees. A narrower floor would decrease the difference. The outer rim would be moving at 30.13 m/s and it would be rotating at 2.877 rpm

 

The degree would depend on the size of the centrifuge. For example, let's say your spacecraft is 15m in diameter. If we assume a normal 1g weight for someone standing on the inner surface, then I estimate that going from a seated to standing position would result in a Coriolis effect equal to a sideways change in velocity of 1 1/4 mph.

Another interesting point is that, depending on your height, you would weigh roughly 6% more while sitting down than when standing up.(while sitting down your center of mass will be further from the axis of rotation, and where the g force will be stronger)

So the new phrase for offering someone a seat would be "take a load on".

[michel123456]

They will send a robot anyway.

[Carrock]

One option which doesn't seem to have had much attention:

 

Split the the spacecraft into two masses: one for crew habitation and the other 'not wanted on voyage'.

 

Attach the two with a cable long enough to make coriolis force etc not a problem and spin up for 1G in crew quarters.

 

This wouldn't be simple or cheap but it may be more cost effective than other options.

[Airbrush]

.....Split the the spacecraft into two masses: one for crew habitation and the other 'not wanted on voyage'.

 

Attach the two with a cable long enough to make coriolis force etc not a problem and spin up for 1G in crew quarter.....

 

Sounds like a great idea!

To generate an effective 1g force, the floor would have to be tilted at a angle of 67.8 degrees from the horizontal.(And since the floor is tilted, parts of it will be closer or further than others to the axis of rotation than others and experience less or more lateral g force. Thus, the total g-force will vary from edge to edge, and if you want the floor to remain "level" for the occupants at all points, the floor would have to "curve". By how much depends on how wide you want you floor to be compared to the radius of the centrifuge. )

And just how big do you mean by giant? What radius are we talking about? How wide of a floor? For example, if we give it a 100 m radius(outer edge) and a 10 m width, then the inner edge would feel 0.97g and to be "level" would be tilted at a bit under 67 degrees. A narrower floor would decrease the difference. The outer rim would be moving at 30.13 m/s and it would be rotating at 2.877 rpm

 

The degree would depend on the size of the centrifuge. For example, let's say your spacecraft is 15m in diameter. If we assume a normal 1g weight for someone standing on the inner surface, then I estimate that going from a seated to standing position would result in a Coriolis effect equal to a sideways change in velocity of 1 1/4 mph.

Another interesting point is that, depending on your height, you would weigh roughly 6% more while sitting down than when standing up.(while sitting down your center of mass will be further from the axis of rotation, and where the g force will be stronger)

 

We have 2 different problems, one is how to have one g on the trip to and from Mars, the other is a distant future plan for a large-enough centrifuge under the surface of Mars which is a much more complicated problem. It seems like Carrock's idea is a practical solution for the trip to and from Mars.

Edited August 24, 2016 by Airbrush

[Jonas Taelman]

Artificial gravity isn't that hard to achieve. The only thing necessary for this gravity is a round, cilinder-form shape of the spacecraft. The gravity can be made by spinning the spacecraft in a consistant speed in lenght around it's own axis. All inside loose objects will clamp to the inside wall due to the artificial atmosphere that is created inside the spacecraft for breathing and, well, living. The same thing happens when you spin a bucket of water at the same speed around. Momentum and Newton's 1st law makes sure that the water stays in the bucket.

 

The travelcourse, on the other hand, is a little bit more complicated. First this spaceship needs to create an orbit around the Earth before setting up course to Mars. For artificial gravity to be created we need quite a long ship. This is a complication since the longer or bigger the ship is the heavier it will be and the more fuel you will need. When we do make it to a full and succesfull orbit, chances are high that we don't have any fuel left. This, ofcourse, can be easely solved be sending more fuel op there (but is really expensive). If we do have the ability to refuel, we need to make a calculated burn to enlargen our orbit shape into a very long oval shape that intersects Mars' gravity field. This burn will use a lot of fuel. When we get in that gravity field we need te make another burn to get into orbit aroud Mars, again, this uses fuel. When in orbit we still need to make a soft, succesfull landing. By turning the spaceship retrograde (oppesite side of course direction), burning, make the orbit smaller and get closer to Mars until we enter the atmosphere. More fuel is used.

At a speed of about Mach 2 or Mach 3 even (1 mach = speed of sound = approx. 1320 km/h) we can't say we can make a soft landing. By again burning retrograde we slow down by a big amount and are able to land softly while using landingstruts and parachutes.

 

This journey would take about 10 - 15 years, billions of dollars, billions of gallons of fuel, and a lot of smart and patient people.

Edited September 3, 2016 by Jonas Taelman

[Airbrush]

So you think there will be no artificial gravity during the trips to and from Mars for the first manned mission?

[John Cuthber]

One option which doesn't seem to have had much attention:

 

Split the the spacecraft into two masses: one for crew habitation and the other 'not wanted on voyage'.

 

Attach the two with a cable long enough to make coriolis force etc not a problem and spin up for 1G in crew quarters.

 

This wouldn't be simple or cheap but it may be more cost effective than other options.

Actually, that is simple and cheap.

It's a very good idea. The only problem would be if the rope got hit by something and snapped, but space travel is always going to be horribly risky.

[Airbrush]

"Rope?" How about an excess number of extra strong cables for redundancy? Even if a micro-meteor takes out a cable, there are several more to take it's place.

Edited September 3, 2016 by Airbrush

[Jonas Taelman]

people forget that gravity is essential during trips at this extent. The journey from Earth to Mars for Curiosity took 6 years, and that's only for an unmanned ship. For a manned ship it would take much longer so let's say there's even a minimum of 6 years. To live without any gravity for six whole years will take it's toll on not only your health, but also your complete anatomy.

 

 

And about the Coriolis Force.

Why not make the scale bigger? Send it into orbit in parts. The bigger the scale the smaller the effects, no?

I also think in times of emergency that the Coriolis effect will be the least of our worries.

Edited September 3, 2016 by Jonas Taelman

[Airbrush]

The ideal Mars mission is supposed to take about 9 months to get there, then you need to stay on Mars for about 18 months, then the return trip would take another 9 months. That kind of mission will minimize travel time. So that means 18 months in zero gravity and 18 months in Mars gravity for those who on the surface, but zero g's for 36 months for those in orbit around Mars. That much zero g's should be very bad for people even if it's not 6 years.

Edited September 3, 2016 by Airbrush