Author Topic: Artificial Gravity - Why Weight?  (Read 24656 times)

Offline ndevereux

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Artificial Gravity - Why Weight?
« on: 04/30/2016 09:43 PM »
You may enjoy watching this short TEDx talk I gave on Feb 20th, 2016, about the importance of artificial gravity for manned missions to Mars, and beyond.


Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #1 on: 05/01/2016 03:43 AM »
I think artificial gravity is cool, but for Mars it might not be necessary.
You would not need artificial gravity if the flight to mars was short enough. I would rather spend the weight (and monetary) budget on more fuel or a better engine that shortens the trip time. For missions beyond mars or for orbital stations, it is a different matter, though. Also, if I may suggest, you could rotate the habitats at the end of the trusses by 90 degrees (using the truss as a rotation axis) and give the inhabitants and longer straight floor. Unless you just rotate the entire spacecraft, you might want to consider counter rotating something (more habitats?) in the other direction?
« Last Edit: 05/01/2016 03:51 AM by Elmar Moelzer »

Online Coastal Ron

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Re: Artificial Gravity - Why Weight?
« Reply #2 on: 05/01/2016 04:18 AM »
I think artificial gravity is cool, but for Mars it might not be necessary.
You would not need artificial gravity if the flight to mars was short enough. I would rather spend the weight (and monetary) budget on more fuel or a better engine that shortens the trip time.

The availability of fuel for refueling spaceships in space means that over time we can go faster and faster to our destinations, so while artificial gravity would be nice, passengers may be able to make a multi-month trip in 0G without too much physical degradation.  But we will need to ship enough people to Mars so that we can understand what the actual effects are.

Quote
For missions beyond mars or for orbital stations, it is a different matter, though. Also, if I may suggest, you could rotate the habitats at the end of the trusses by 90 degrees (using the truss as a rotation axis) and give the inhabitants and longer straight floor. Unless you just rotate the entire spacecraft, you might want to consider counter rotating something (more habitats?) in the other direction?

Artificial gravity through the use of rotating structures will require more much more mass than we'll be able to push between Mars and Earth in the early years.  That's because mass requires fuel, and fuel requires rockets from Earth (at least for the trip from Earth to Mars).  It's going to be a while until fuel is that cheap that we can build large spaceships with rotating gravity.

But when that time comes I have some ideas...   :D
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Ludus

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Re: Artificial Gravity - Why Weight?
« Reply #3 on: 05/01/2016 07:43 PM »
Zubrin's Mars Direct had this as an element even with a very minimalist approach. He just used a tether between the Hab and the spent upper stage.

I've always been puzzled why so little attention has been paid to this, despite the long history of the idea and the clear data about problems with long stays in microgravity.


Offline mvpel

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Re: Artificial Gravity - Why Weight?
« Reply #4 on: 05/01/2016 11:39 PM »
At a Mars Society convention I attended way back when at UC, there was a really cool presentation about fault-tolerant tether design too.
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline JamesH65

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Re: Artificial Gravity - Why Weight?
« Reply #5 on: 05/09/2016 11:46 AM »
I think artificial gravity is cool, but for Mars it might not be necessary.
You would not need artificial gravity if the flight to mars was short enough. I would rather spend the weight (and monetary) budget on more fuel or a better engine that shortens the trip time. For missions beyond mars or for orbital stations, it is a different matter, though. Also, if I may suggest, you could rotate the habitats at the end of the trusses by 90 degrees (using the truss as a rotation axis) and give the inhabitants and longer straight floor. Unless you just rotate the entire spacecraft, you might want to consider counter rotating something (more habitats?) in the other direction?

Might be worth reading Chris Hadfield's book, to get some idea of the problems he suffered after being in Zero G for his ISS commander mission. I was surprised how badly he was affected. Admittedly, 6 months, so slightly longer than the proposed Mars trips (100 days?), but still very relevant.

Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #6 on: 05/09/2016 09:57 PM »
I am of course talking about Mars missions with transit times much shorter than 100 days. There are several concepts, using advanced propulsion systems with trip times as short as 30 days.
 Once your trip times get significantly over 30 days, everything starts to get much more complicated and the lack of gravity is only one of those problems. This is why I am saying that it would be a good idea to further investigate those propulsion concepts and invest money and launch weight into those, rather than artificial gravity. This is just my personal opinion of course and I understand that some people might think differently.

Offline JamesH65

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Re: Artificial Gravity - Why Weight?
« Reply #7 on: 05/10/2016 06:15 AM »
I am of course talking about Mars missions with transit times much shorter than 100 days. There are several concepts, using advanced propulsion systems with trip times as short as 30 days.
 Once your trip times get significantly over 30 days, everything starts to get much more complicated and the lack of gravity is only one of those problems. This is why I am saying that it would be a good idea to further investigate those propulsion concepts and invest money and launch weight into those, rather than artificial gravity. This is just my personal opinion of course and I understand that some people might think differently.

Whilst those propulsion systems may be some years/decades away, artificial gravity would still be required for longer trips to the outer planets. So both will be needed I suspect.

Offline Jcc

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Re: Artificial Gravity - Why Weight?
« Reply #8 on: 05/15/2016 03:02 AM »
I think NASA should build a rodent habitat with some male and female mice for the ISS that rotates and can simulate Mars gravity. Maybe put it inside the BEAM if they are short on space. That would be to verify that mammals can reproduce successfully in Mars gravity. They may start with lower animals such as insects or worms first.

Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #9 on: 05/15/2016 03:12 AM »
Whilst those propulsion systems may be some years/decades away, artificial gravity would still be required for longer trips to the outer planets. So both will be needed I suspect.
The video is about a trip to Mars. I think for that particular application, trips can be shortened enough to remove the need for artificial gravity. Now for longer trips, this is a different matter all together.

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #10 on: 05/15/2016 05:08 AM »
I think NASA should build a rodent habitat with some male and female mice for the ISS that rotates and can simulate Mars gravity. Maybe put it inside the BEAM if they are short on space. That would be to verify that mammals can reproduce successfully in Mars gravity. They may start with lower animals such as insects or worms first.

I think NASA does not want that as it might interfere with microgravity experiments. They would have to shift the entire focus of what is done on the ISS.

I have been thinking for a while they may do that on MCT. I imagine they will want to verify the ECLSS of MCT with a crew in orbit for at least 6-8 months. Time enough to do such an experiment. If they are generous they may do the experiment with moon gravity in parallel, the same centrifuge but nearer to the center. The experiment could run long enough that space born mice can reproduce.

Offline Jcc

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Re: Artificial Gravity - Why Weight?
« Reply #11 on: 05/15/2016 12:54 PM »
I think NASA should build a rodent habitat with some male and female mice for the ISS that rotates and can simulate Mars gravity. Maybe put it inside the BEAM if they are short on space. That would be to verify that mammals can reproduce successfully in Mars gravity. They may start with lower animals such as insects or worms first.

I think NASA does not want that as it might interfere with microgravity experiments. They would have to shift the entire focus of what is done on the ISS.

I have been thinking for a while they may do that on MCT. I imagine they will want to verify the ECLSS of MCT with a crew in orbit for at least 6-8 months. Time enough to do such an experiment. If they are generous they may do the experiment with moon gravity in parallel, the same centrifuge but nearer to the center. The experiment could run long enough that space born mice can reproduce.

SpaceX could do it on an automated DragonLab if NASA or other ISS partners are not interested. NASA does want to go to Mars, so it is relevant, and it could be very interesting basic science. They can call it SpaceSex, that should grab people's attention.
« Last Edit: 05/15/2016 01:28 PM by Jcc »

Offline muomega0

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Re: Artificial Gravity - Why Weight?
« Reply #12 on: 05/15/2016 01:24 PM »
I think artificial gravity is cool, but for Mars it might not be necessary.
You would not need artificial gravity if the flight to mars was short enough. I would rather spend the weight (and monetary) budget on more fuel or a better engine that shortens the trip time.

The availability of fuel for refueling spaceships in space means that over time we can go faster and faster to our destinations, so while artificial gravity would be nice, passengers may be able to make a multi-month trip in 0G without too much physical degradation.  But we will need to ship enough people to Mars so that we can understand what the actual effects are.

Quote
For missions beyond mars or for orbital stations, it is a different matter, though. Also, if I may suggest, you could rotate the habitats at the end of the trusses by 90 degrees (using the truss as a rotation axis) and give the inhabitants and longer straight floor. Unless you just rotate the entire spacecraft, you might want to consider counter rotating something (more habitats?) in the other direction?

Artificial gravity through the use of rotating structures will require more much more mass than we'll be able to push between Mars and Earth in the early years.  That's because mass requires fuel, and fuel requires rockets from Earth (at least for the trip from Earth to Mars).  It's going to be a while until fuel is that cheap that we can build large spaceships with rotating gravity.

But when that time comes I have some ideas...   :D
While Economic Access to Space is one grand challenge, another is Space Health and Medicine--"Eliminate or mitigate the negative effects of the space environments on human physical and behavioral health"

Studying the solutions in space, say at L2 or LEO, will be way cheaper than sending crew to Mars or the moon and provides parametric data as well.  Avoiding gravity wells saves tremendous cost and asteroid destinations have very low gravity.  Slower trip times result in a substantially cheaper architecture.

Of course, if all of NASA's budget is simply meant to spent on propulsion and capsules, and ignoring the Grand Challenges of the past decades, then by all means continue to spend the next decade spending all the cash on multiple engine, capsule, and LV development efforts.

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Re: Artificial Gravity - Why Weight?
« Reply #13 on: 05/15/2016 01:29 PM »
Whilst those propulsion systems may be some years/decades away, artificial gravity would still be required for longer trips to the outer planets. So both will be needed I suspect.
The video is about a trip to Mars. I think for that particular application, trips can be shortened enough to remove the need for artificial gravity. Now for longer trips, this is a different matter all together.

Alternatively, an Earth-Mars cycler with artificial gravity.
Dragons (Orion, Starliners, BFS etc) function as taxi and lifeboats.

Offline The Amazing Catstronaut

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Re: Artificial Gravity - Why Weight?
« Reply #14 on: 05/15/2016 01:31 PM »

Of course, if all of NASA's budget is simply meant to spent on propulsion and capsules, and ignoring the Grand Challenges of the past decades, then by all means continue to spend the next decade spending all the cash on multiple engine, capsule, and LV development efforts.

Better to have the means to get there and current gen life support, than no means to get there and a significantly better life support.

We have the resources to keep people alive on mars now. The focus (and it's a vital one) is mitigating health risks and making everything cheaper, more sustainable and easier to expand using primarily martian resources - but one fiscal challenge at a time. You don't start fireproofing a building if the basic structure is impossible.

Probably more important than artificial gravity on mars is getting general healthcare fixed. How do I grow basic tissues on a martian environment? If someone gets cancer can we treat that without having to send them back to Earth? Somebody has inhaled martian dust? How do we look after their lungs?
« Last Edit: 05/15/2016 01:34 PM by The Amazing Catstronaut »
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Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #15 on: 05/15/2016 01:33 PM »
SpaceX could do it on an automated DragonLab if NASA or other ISS partners are not interested. NASA does want to go to Mars, so it is relevant, and it could be very interesting basic science. They can call it SpaceSex, that should grab people's attention.

Probably they could. However it is not that easy to maintain a habitat for mice over many months, keep it clean and feed them without humans. It is also extra expense and funds are limited. Doing it on a MCT test flight brings almost no extra cost assuming they see the need to do a long test flight.

Offline muomega0

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Re: Artificial Gravity - Why Weight?
« Reply #16 on: 05/15/2016 02:03 PM »

Of course, if all of NASA's budget is simply meant to spent on propulsion and capsules, and ignoring the Grand Challenges of the past decades, then by all means continue to spend the next decade spending all the cash on multiple engine, capsule, and LV development efforts.

Better to have the means to get there and current gen life support, than no means to get there and a significantly better life support.

We have the resources to keep people alive on mars now. The focus (and it's a vital one) is mitigating health risks and making everything cheaper, more sustainable and easier to expand using primarily martian resources - but one fiscal challenge at a time. You don't start fireproofing a building if the basic structure is impossible.

Probably more important than artificial gravity on mars is getting general healthcare fixed. How do I grow basic tissues on a martian environment? If someone gets cancer can we treat that without having to send them back to Earth? Somebody has inhaled martian dust? How do we look after their lungs?
Gas stations in space with prepositioned supplies and propellant are the fastest way to send crew to Mars, but it appears to be limited to about 3 months one way with existing technology.  EP tugs combined with chemical tugs cycling from near Mars to L2, and likely multiple tugs to reduce LOM/LOC.  A hybrid EP/chemical crew transfer needs more work.   Its N months travel, M months in 1/3rd g, and N back, where M costs a significant amount of dV and IMLEO.

Contrast that cost with a couple of launches of VG hardware and repeated trips to L2--much more data to actually address the challenge, rather than to side step the issue.   Even on a fly by mission to Mars, the crew to pause and 'go out for a spin' so to speak--long term, efficient gathering of data.  They could also spin at 1/3g in preparations for the Mars trip.   The crew would service satellites and gas station at L2 , or perhaps space junk sweepers in preparations for ISRU near zero g sources.  Think multiple purpose missions and 'flight rate'.

Offline Lee Jay

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Re: Artificial Gravity - Why Weight?
« Reply #17 on: 05/15/2016 02:10 PM »
I agree with the OP.

I think sending humans to Mars is a very, very dangerous thing to do.  Having astronauts die on such a mission would result in substantial pain, expense and delay as has been shown in the past.  With a growing culture of risk aversion, it would likely be worse now.

Ways to buy down risk are:

- Artificial gravity
- Radiation shielding
- Larger vehicle
- More people going for more capabilities and more redundancy

I'd like to see an artificial gravity station launched for research.  This could be a simple hab with weight attached by a tether to see what radii and what rotation rates give acceptable and unacceptable human results.  The idea would be to change the tether length and keep gravity the same for Earth, Mars and Moon gravity and see who gets sick and who stays well for each combination.  In this way we could better understand what it would take to build a Mars transport that has the necessary proportions to keep everyone well on a long-duration trip to Mars.

When people say things like, "we can get their really fast", I like to point out that a third of the people who went to the moon on moon landing missions stayed in orbit.  The same makes sense for a Mars mission and those people would potentially be subject to two and a half years in microgravity even with a really fast transport system.  I don't believe this is acceptable.  I also think it would be a lot better if people had time on a mission to the surface of Mars to adapt to Mars gravity on the way.  One could imagine leaving Earth at Earth gravity and transitioning to Mars gravity as the vehicle approached Mars.

Offline Toast

Re: Artificial Gravity - Why Weight?
« Reply #18 on: 05/15/2016 03:32 PM »
I like to point out that a third of the people who went to the moon on moon landing missions stayed in orbit.  The same makes sense for a Mars mission

With modern automated docking maneuvers, is it really necessary to keep somebody on orbit?  I was under the impression that NASA had been planning on this when they were considering new manned lunar missions as part of Constellation before it was cancelled. If separate command and decent modules are used, why not have the orbiting command module run by computer?

Offline Lee Jay

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Re: Artificial Gravity - Why Weight?
« Reply #19 on: 05/15/2016 05:04 PM »
I like to point out that a third of the people who went to the moon on moon landing missions stayed in orbit.  The same makes sense for a Mars mission

With modern automated docking maneuvers, is it really necessary to keep somebody on orbit?  I was under the impression that NASA had been planning on this when they were considering new manned lunar missions as part of Constellation before it was cancelled. If separate command and decent modules are used, why not have the orbiting command module run by computer?

For extra safety, you'd like to have a person or persons on board who could fix things or manually operate things that get persnickety, such as is done during visiting vehicle dockings on ISS.

Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #20 on: 05/15/2016 07:34 PM »
Gas stations in space with prepositioned supplies and propellant are the fastest way to send crew to Mars, but it appears to be limited to about 3 months one way with existing technology.
I think there was a concept for a VASIMIR based mission with a slightly over 30 day trip time. MSNW is also working on a new fusion drive that could result in 30 day trip times with a space craft that fits into a single BFR launch (with payload to spare) or a single SLS launch (with no margin).

Online launchwatcher

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Re: Artificial Gravity - Why Weight?
« Reply #21 on: 05/15/2016 10:47 PM »
Gas stations in space with prepositioned supplies and propellant are the fastest way to send crew to Mars, but it appears to be limited to about 3 months one way with existing technology.
I think there was a concept for a VASIMIR based mission with a slightly over 30 day trip time. MSNW is also working on a new fusion drive that could result in 30 day trip times with a space craft that fits into a single BFR launch (with payload to spare) or a single SLS launch (with no margin).
There's a 39-day VASIMR mission described here:

http://www.adastrarocket.com/Andrew-SPESIF-2011.pdf

If I'm reading the paper correctly, the 39 day mission requires a 200MW nuclear reactor with power density of around 0.8kg/kW.   It mentions in passing that 4kg/kW is the best that's currently achievable.


Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #22 on: 05/15/2016 10:59 PM »
There's a 39-day VASIMR mission described here:

http://www.adastrarocket.com/Andrew-SPESIF-2011.pdf

If I'm reading the paper correctly, the 39 day mission requires a 200MW nuclear reactor with power density of around 0.8kg/kW.   It mentions in passing that 4kg/kW is the best that's currently achievable.
Not "achievable", but that has been designed and built. Mind you that most current reactors are quite small and the power increases volumetrically. There are also concepts for solar power that could reach as little as 1kg/kWh. And then there is still MSNWs fusion drive (which is arguably a bit further out).
Anyway, my point was that there are conceivable ways to get to such short trip times if the funding and will is there. So you can spend the money on artificial gravity or on faster trip times. I feel like faster trips gain us more for Mars.
« Last Edit: 05/15/2016 11:02 PM by Elmar Moelzer »

Offline philw1776

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Re: Artificial Gravity - Why Weight?
« Reply #23 on: 05/16/2016 06:08 PM »
Artificial gravity has a high probability of actually working and is a low capital investment R&D.  VASIMR with its way beyond state of the art power requirements costs $$$ to develop and has a good chance of under or not performing.  More so for the fusion approach.  Solar can get you a few megawatts but not nearly enough even with HUGE arrays.

Those believing that the also as yet non-existent BFR will happen have an easier "fast" 100-120 day transit solution.  Load 'er up with an extra couple hundred tons of propellant, a few more tanker launches to LEO refueling, and fire away with a couple extra Km/sec.  Brute force but large scale works for you here.  Don't add complexity of additional vehicles and waste propellant entering Mars orbit but EDL directly to the landing, as is planned for Red Dragon.

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Offline JasonAW3

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Re: Artificial Gravity - Why Weight?
« Reply #24 on: 05/16/2016 07:12 PM »
Interesting thought here;

     If using the Tether With Spent Stage Counter-Mass technique, one could, in theory, DRASTICALLY reduce the velocity of the approaching craft by simply cutting away the counter mass when it is approaching the direction of flight, assuming the rotation is parallel to the direction that the craft is traveling.

     Of course one would have to kill the tumble that would result from cutting loose the mass, but this shouldn't be too great of an issue.   
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Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #25 on: 05/16/2016 10:33 PM »
On the subject of artificial gravity for long duration space flight, NASA researchers Dr. Michael Schmidth and Dr. Thomas Goodwin, in an hour and a half interview for The Space Show, presented a history of artificial gravity research and summarized their own work on OMICS analysis pertaining to the human factors of exposure to microgravity and how artificial gravity might mitigate its effects on human physiology. They also outlined parameters for possible missions to Mars (or other transorbital deep space flights) involving artificial gravity, including SpaceX's MCT plans. It's worth a listen. Go to http://www.thespaceshow.com/show/01-mar-2016/broadcast-2657-dr.-michael-schmidth-dr.-thomas-goodwin. One interesting speculation they mentioned, based on animal studies, is that Mars' 0.38G gravity field might not be strong enough to prevent harm to human health over long stays on the planet.
« Last Edit: 05/16/2016 10:36 PM by WindyCity »

Offline Aussie_Space_Nut

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Re: Artificial Gravity - Why Weight?
« Reply #26 on: 05/17/2016 06:21 AM »
(snip) One interesting speculation they mentioned, based on animal studies, is that Mars' 0.38G gravity field might not be strong enough to prevent harm to human health over long stays on the planet.

And this is why we must have at least a system whereby we can simulate Mars gravity for extended stays. I mentioned this in the past but it is only reasonable to assume that if you sent people somewhere knowing it MAY BE HARMFUL then surely you open yourself up to legal claims. I can see the lawyers standing in the court rooms showing all the wonderful concept pictures of idyllic mars bases, of how the believers got the hopes up of the decieved thereby condemning them to a sorry end..........on mars! :-)

For the record I want to go to Mars but it just freaking does my head in why we will not simulate the Mars environment in a reasonably safe manner in Earth orbit, close enough for a quick trip home should any problems occur. I mean, you can make an argument for just about anything but surely what is reasonable should prevail.

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #27 on: 05/17/2016 09:10 AM »
For the record I want to go to Mars but it just freaking does my head in why we will not simulate the Mars environment in a reasonably safe manner in Earth orbit, close enough for a quick trip home should any problems occur. I mean, you can make an argument for just about anything but surely what is reasonable should prevail.

So for the record. Based on one speculation you want to stop going to Mars, the only place where you can fully "simulate" Mars conditions and spend billions (and how many years?) to simulate a less authentic environment for studies?

Offline JamesH65

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Re: Artificial Gravity - Why Weight?
« Reply #28 on: 05/17/2016 11:12 AM »
(snip) One interesting speculation they mentioned, based on animal studies, is that Mars' 0.38G gravity field might not be strong enough to prevent harm to human health over long stays on the planet.

And this is why we must have at least a system whereby we can simulate Mars gravity for extended stays. I mentioned this in the past but it is only reasonable to assume that if you sent people somewhere knowing it MAY BE HARMFUL then surely you open yourself up to legal claims. I can see the lawyers standing in the court rooms showing all the wonderful concept pictures of idyllic mars bases, of how the believers got the hopes up of the decieved thereby condemning them to a sorry end..........on mars! :-)

For the record I want to go to Mars but it just freaking does my head in why we will not simulate the Mars environment in a reasonably safe manner in Earth orbit, close enough for a quick trip home should any problems occur. I mean, you can make an argument for just about anything but surely what is reasonable should prevail.

Everyone going to Mars will know EXACTLY what they are letting themselves in for. The lawyers will have their signatures in blood confirming it. I'm not seeing any lawsuits in the near future.

Offline RonM

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Re: Artificial Gravity - Why Weight?
« Reply #29 on: 05/17/2016 03:31 PM »
(snip) One interesting speculation they mentioned, based on animal studies, is that Mars' 0.38G gravity field might not be strong enough to prevent harm to human health over long stays on the planet.

And this is why we must have at least a system whereby we can simulate Mars gravity for extended stays. I mentioned this in the past but it is only reasonable to assume that if you sent people somewhere knowing it MAY BE HARMFUL then surely you open yourself up to legal claims. I can see the lawyers standing in the court rooms showing all the wonderful concept pictures of idyllic mars bases, of how the believers got the hopes up of the decieved thereby condemning them to a sorry end..........on mars! :-)

For the record I want to go to Mars but it just freaking does my head in why we will not simulate the Mars environment in a reasonably safe manner in Earth orbit, close enough for a quick trip home should any problems occur. I mean, you can make an argument for just about anything but surely what is reasonable should prevail.

Everyone going to Mars will know EXACTLY what they are letting themselves in for. The lawyers will have their signatures in blood confirming it. I'm not seeing any lawsuits in the near future.

Exploration missions to Mars will be dangerous and everyone knows that. No lawsuits afterwards.

The big issue is whether or not it is possible to colonize Mars. We need to know if 0.38g is enough for long term health before we start building a colony. Artificial gravity studies will be important.

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #30 on: 05/17/2016 04:42 PM »
Exploration missions to Mars will be dangerous and everyone knows that. No lawsuits afterwards.

Yes.

The big issue is whether or not it is possible to colonize Mars. We need to know if 0.38g is enough for long term health before we start building a colony. Artificial gravity studies will be important.

I am of the firm opinion that artificial gravity on a large scale has no place in such a scenario. We can and should build a base on Mars regardless. That base is the place to find out about long term health, including reproduction. First with animals and then soon with humans.

Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #31 on: 05/17/2016 06:30 PM »
The big issue is whether or not it is possible to colonize Mars. We need to know if 0.38g is enough for long term health before we start building a colony. Artificial gravity studies will be important.

The same issue would affect permanent bases on the moon, but even more so. Schmidth and Goodwin also talked about surface-based centrifugal gravity simulators that people could spend time in to ward off the ill health effects of low gravity. That would add considerable complexity to living permanently on the surface of Mars (assuming that 0.38G is insufficient to prevent muscle and bone loss over time), but it could make it doable.

Obviously, human studies in LEO are essential in order to move  in a rational manner toward long-duration deep space flight or surface colonization of the moon or Mars.
« Last Edit: 05/17/2016 06:34 PM by WindyCity »

Offline philw1776

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Re: Artificial Gravity - Why Weight?
« Reply #32 on: 05/17/2016 11:57 PM »
Why do we NEED to do artificial grav studies in LEO before Mars?
Where did we do zero grav studies before we sent people into LEO?
Send people on round trips and animals on longer trips to Mars. Disect them.  The animals, not the people.
If incurable side affects, then no Mars colony until medicine advances.
Else, continue.

Not against AG studies in LEO, just against that they are NEEDED before proceeding.
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Offline QuantumG

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Re: Artificial Gravity - Why Weight?
« Reply #33 on: 05/18/2016 12:07 AM »
One argument why you might want to know the reduced gravity effects of surface stays on Mars is to reduce the amount of reduce gravity mitigation assurance you need for a mission. If you conservatively assume that 0.38 gravity is no better than zero gravity for bone mass depletion, then you need to show that ~900 days in zero-g is survivable. Obviously, being able to show that Mars gravity is not as debilitating as zero-g will reduce the mitigation requirements. That said, a long duration mission to the lunar surface may be just as effective as an artificial gravity experiment, and more attractive to whoever is footing the bill.
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Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #34 on: 05/18/2016 11:33 PM »
Why do we NEED to do artificial grav studies in LEO before Mars?

NASA is cautious is my guess. (Isn't astronaut health and safety the agency's preeminent concern?) Schmidth and Goodwin would like to study how much (or how little) artificial gravity is needed to prevent ill health effects. They call that the "sweet spot". Such studies would compare incremental levels of artificial gravity to zero in on it. If 0.38G doesn't cause problems, that would be good to know for mission and vehicle design purposes. The slower the centrifuge turns, fewer vestibular problems arise from the Coriolis effect. The strength of a centrifugal force is determined by the length of the centrifuge arm and its speed.

These guys also would like to bring nuclear thermal propulsion on line to reduce transit time to Mars (or other deep space destinations). Wouldn't we all? And good luck with that.

I should also mention that they're not asserting that artificial gravity would have the same beneficial effects as a gravity field. Animal studies suggest that it would, but shy of actually conducting human studies on orbit, it's a question mark. Centrifuge studies on earth are inconclusive.
« Last Edit: 05/19/2016 05:44 PM by WindyCity »

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #35 on: 05/19/2016 12:27 AM »
Why do we NEED to do artificial grav studies in LEO before Mars?

NASA is cautious is my guess. (Isn't astronaut health and safety the agency's preeminent concern?)

That's why I am somewhat surprised that they plan orbital missions. They are not shorter than landing missions and they are continuous zero g. That does not sound like overly concerned to me. They must be very confident that that time is acceptable. Spending part of that time under martian gravity cannot be worse than microgravity the whole time.


Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #36 on: 05/19/2016 05:49 PM »
That's why I am somewhat surprised that they plan orbital missions.

No studies are planned as of now, I believe. The researchers spoke in favor only of conducting them. I do recommend listening to their Space Show interview. That would be better than my trying to relay what I recall from it. These fellows have detailed knowledge of the history of artificial gravity research, especially from the point of view of the physiological effects of weightlessness and artificial grav's ameliorative value.

As to your concern about why LEO studies would be preferable in their minds to studying low gravity's effects on the surface of Mars,  the reason might be that they wouldn't want to send people on a 2-yr plus mission without knowing in advance what the possible dangers of low-grav exposure are. If they could determine what the "sweet spot" is from studies in zero-G, that could save money in terms of mission design while preventing harm to the astronauts. That would seem to make sense to me.

I think that before planners talk seriously about what the challenges are in colonizing Mars they ought to have some idea of whether 0.38G is enough gravitational force to prevent harm to human health. If it's not enough to keep people healthy, then perhaps astronauts could spend a period of time each day in a surface centrifuge, in the manner of  a daily exercise regimen, to keep them healthy. Meanwhile, advances in medications or genetic modification could solve the problem in the future.
« Last Edit: 05/19/2016 06:03 PM by WindyCity »

Offline CuddlyRocket

Re: Artificial Gravity - Why Weight?
« Reply #37 on: 05/20/2016 01:33 AM »
These fellows have detailed knowledge of the history of artificial gravity research, especially from the point of view of the physiological effects of weightlessness and artificial grav's ameliorative value.

Be wary of experts promoting "further studies" in their field; it is in their interests after all!

Quote
I think that before planners talk seriously about what the challenges are in colonizing Mars they ought to have some idea of whether 0.38G is enough gravitational force to prevent harm to human health.

The best, possibly only, way of finding that out is to send people to Mars; especially if you're talking about really long-term exposure to 0.38g - we can hardly expect to keep people in orbital centrifuges for decades!

At least some of the first people on Mars will come back and can then be tested; with steadily increasing periods spent on the surface. And you can always send data, even samples, back to Earth. Once there's sufficient capacity on Mars they can do their own biomedical research.

Offline muomega0

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Re: Artificial Gravity - Why Weight?
« Reply #38 on: 05/20/2016 01:45 AM »
These fellows have detailed knowledge of the history of artificial gravity research, especially from the point of view of the physiological effects of weightlessness and artificial grav's ameliorative value.

Be wary of experts promoting "further studies" in their field; it is in their interests after all!
Corollary:  Be wary of experts promoting 'further studies' of decades old LVs and capsules, without developing any technology; it is in their interests after all!

Yet all this 'detailed' knowledge is now extended by the first U.S. data point of almost a year in space.  Why not get one or two data points at fractions of gravity to try and bound the problem?  Ahhh...must not be in the interests of propulsion and capsule operations.

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #39 on: 05/20/2016 06:04 AM »
Once there's sufficient capacity on Mars they can do their own biomedical research.

That would likely be from day one of the first landing. I do expect a permanent presence from that day on and individual people staying 2+ years.

That is if the first landing is done by SpaceX which I see likely.

Offline llanitedave

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Re: Artificial Gravity - Why Weight?
« Reply #40 on: 05/20/2016 03:07 PM »
Mice on the Moon.  Land a colony there for a few mouse generations, monitor them, and then bring them back for study.  Seems straightforward, and a lot faster and cheaper than a human mission to Mars.
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Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #41 on: 05/20/2016 04:12 PM »
Mice on the Moon.  Land a colony there for a few mouse generations, monitor them, and then bring them back for study.  Seems straightforward, and a lot faster and cheaper than a human mission to Mars.

On the moon you have the same problem as in orbit. Without humans tending the habitat it will be difficult to maintain it for such a long time.

Plus a habitat with artificial gravity for mice is not that hard, you don't need a large diameter. It would not even be too hard to have two levels with moon and Mars gravity.

Offline the_other_Doug

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Re: Artificial Gravity - Why Weight?
« Reply #42 on: 05/20/2016 05:51 PM »
Mice on the Moon.  Land a colony there for a few mouse generations, monitor them, and then bring them back for study.  Seems straightforward, and a lot faster and cheaper than a human mission to Mars.

On the moon you have the same problem as in orbit. Without humans tending the habitat it will be difficult to maintain it for such a long time.

Plus a habitat with artificial gravity for mice is not that hard, you don't need a large diameter. It would not even be too hard to have two levels with moon and Mars gravity.

Well, gee, if you need to send people to tend the thing, well, then, I guess you have to do so.

Since it's a dirty, rotten, thankless job (but somebody has to do it), I would volunteer to go and muck out the rodent stables every day.  I have to go to the Moon to do it?  I can make that sacrifice... :D
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Offline QuantumG

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Re: Artificial Gravity - Why Weight?
« Reply #43 on: 05/20/2016 11:04 PM »
You'll need to get those mice back too. Can't tell much from just remote observation.

It's kinda sad that sending mice to the surface of the Moon and returning them safely to Earth is beyond our capabilities.
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Offline llanitedave

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Re: Artificial Gravity - Why Weight?
« Reply #44 on: 05/21/2016 01:32 AM »
You'll need to get those mice back too. Can't tell much from just remote observation.

It's kinda sad that sending mice to the surface of the Moon and returning them safely to Earth is beyond our capabilities.


Well, I believe this nation should commit itself.
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Offline savuporo

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Re: Artificial Gravity - Why Weight?
« Reply #45 on: 05/21/2016 01:59 AM »
Mice on the Moon.  Land a colony there for a few mouse generations, monitor them, and then bring them back for study.  Seems straightforward, and a lot faster and cheaper than a human mission to Mars.

This would have been enough of a start, without going all the way to lunar surface

https://en.wikipedia.org/wiki/Mars_Gravity_Biosatellite
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Offline llanitedave

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Re: Artificial Gravity - Why Weight?
« Reply #46 on: 05/21/2016 03:35 PM »
Mice on the Moon.  Land a colony there for a few mouse generations, monitor them, and then bring them back for study.  Seems straightforward, and a lot faster and cheaper than a human mission to Mars.

On the moon you have the same problem as in orbit. Without humans tending the habitat it will be difficult to maintain it for such a long time.

Plus a habitat with artificial gravity for mice is not that hard, you don't need a large diameter. It would not even be too hard to have two levels with moon and Mars gravity.


Yeah, that's true.  It would be a good use for a free-flying satellite keeping formation with the ISS.
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Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #47 on: 05/21/2016 04:26 PM »
I am of the firm opinion that artificial gravity on a large scale has no place in such a scenario. We can and should build a base on Mars regardless. That base is the place to find out about long term health, including reproduction. First with animals and then soon with humans.

I understand your point of view, and certainly there would be no lack of volunteers to serve as guinea pigs on Mars. People are willing to accept high risks in order to get involved in a wide variety of activities. Given, however, that artificial gravity studies could be performed on orbit that would show the likely health effects of low-gravity exposure, and further would determine the "sweet spot," the minimal amount of gravity needed to prevent debilitating muscle and bone loss, I think that pursuing them would be prudent and ethical. Contrary to what has been said, according to Schmidth and Goodwin centrifugal studies on orbit would likely be revealing, if not one-hundred percent determinative, of the impact of low gravity on human health. In my opinion, therefore, it would be immoral to send people on a mission involving an unknown risk that could possibly have been lessened or eliminated before launch. The fact there are brave souls who would be willing to jump aboard willy-nilly is beside the point. All of us have a responsibility to protect human life when at all possible. Indeed, it might possibly set back human space flight if early Mars travelers suffered any serious ill consequences from exposure to low gravity. It simply seems to me wise and humane to do the studies first and find out what we can before sending people on a dangerous journey.

Online scienceguy

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Re: Artificial Gravity - Why Weight?
« Reply #48 on: 05/21/2016 04:40 PM »
What about mice bred in a centrifuge on the ISS?
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Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #49 on: 05/21/2016 04:53 PM »
What about mice bred in a centrifuge on the ISS?

The objection read most often here is that running a centrifuge on the ISS will interfere with microgravity experiments/research.  I don't know if I buy that, but it is the objection mentioned most often.

Personally I am a proponent of developing an expandable station with a microgravity section and a spinning section, both with both pressurized and hard vacuum work areas. For a lot of reasons ISS is really not suitable to anything larger than something that might support experiments with small rodents in an AG situation.

But what I do see a need for is the build up of a database of medical information much like what was done with divers over 50 years or more to characterize how humans (animals first if desired) respond to different levels, and different time break downs at these levels, of acceleration.  There are tons of WAGs about how much gravity might mitigate health issues, somewhat less about what a sustainable regime of micro-gravity and acceleration exposure would be both in time mixes and levels for acceleration.  But the one thing is, is that we only have experience with 1 g and greater for any length of time, or microgravity in varying amounts of single exposures more than about 90 seconds before returning to a 1 g regime for a long period of time.  Experience with a daily cycle between microgravity and acceleration would be invaluable as well as experience with different acceleration levels.
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Re: Artificial Gravity - Why Weight?
« Reply #50 on: 05/21/2016 05:41 PM »
Will the Bigelow habitat they just installed be big enough to put a mouse centrifuge inside?
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Offline savuporo

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Re: Artificial Gravity - Why Weight?
« Reply #51 on: 05/22/2016 06:40 AM »
What about mice bred in a centrifuge on the ISS?

A free flying centrifuge like Mars Gravity Biosatellite was supposed to be would give much more flexibility. DLRs is going to be launching a very similarly purposed free-flying eu:CROPIS for partial-g plant growth studies soon.

No reason to try and cram it in ISS where it would be difficult to fit a centrifuge and it would likely conflict with micro-g research a lot. However, MGB project plans at some point talked about having a separate experiment in micro-g running in parallel - something that is being done on ISS as we speak.

If ISS were to have any sort of a robotic space tug ( like Jupiter ) then co-orbiting experiments that can be deployed and retrieved would make the most sense.
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Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #52 on: 05/22/2016 05:56 PM »
What about mice bred in a centrifuge on the ISS?

Are we mice or men? Animal studies can help point the way, but their usefulness goes only so far. I should think that human studies will be required to reach a deeper, more reliable understanding of the issue.

Offline The Amazing Catstronaut

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Re: Artificial Gravity - Why Weight?
« Reply #53 on: 05/22/2016 06:44 PM »

Are we mice or men? Animal studies can help point the way, but their usefulness goes only so far. I should think that human studies will be required to reach a deeper, more reliable understanding of the issue.

Pigs would be better, but yet again, pigs require roughly the same life support conditions as humans.
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Online Robotbeat

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Re: Artificial Gravity - Why Weight?
« Reply #54 on: 05/22/2016 07:03 PM »
What about mice bred in a centrifuge on the ISS?

Are we mice or men? Animal studies can help point the way, but their usefulness goes only so far. I should think that human studies will be required to reach a deeper, more reliable understanding of the issue.
Animal studies are huge. You can't (for several reasons) breed several sequential generations of humans in varying levels of gravity just to see what happens.

Let's do this experiment. And do it with a few different mammals, perhaps even chimps (carefully keeping their welfare in mind).
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Offline the_other_Doug

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Re: Artificial Gravity - Why Weight?
« Reply #55 on: 05/23/2016 12:42 AM »
You can't (for several reasons) breed several sequential generations of humans in varying levels of gravity just to see what happens.

Aw, why not?  I will gladly volunteer to spend the rest of my life on the Moon, with as many other volunteers as may arise, to help perform such studies.

Of course, I imagine they would want someone younger than 60 as their starting point... ah, well.  :D  :D  :D
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Online Robotbeat

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Re: Artificial Gravity - Why Weight?
« Reply #56 on: 05/23/2016 01:03 AM »
You can't (for several reasons) breed several sequential generations of humans in varying levels of gravity just to see what happens.

Aw, why not?  I will gladly volunteer to spend the rest of my life on the Moon, with as many other volunteers as may arise, to help perform such studies.

Of course, I imagine they would want someone younger than 60 as their starting point... ah, well.  :D  :D  :D
1) Cost
2) Unethical study, wouldn't be approved by usual scientific bodies
3) Would take like a century
4) The subjects may decide halfway through not to continue. May revolt. Etc.

These are significant complications. Might as well just solve them as well as you can with animal models and just go for it. After all, if the purpose of these experiments is to reduce risk and cost, the experiment would be just as risky and cost just as much as just trying the real thing and so would be pointless.
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Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #57 on: 05/23/2016 01:19 AM »


These are significant complications. Might as well just solve them as well as you can with animal models and just go for it. After all, if the purpose of these experiments is to reduce risk and cost, the experiment would be just as risky and cost just as much as just trying the real thing and so would be pointless.

A mix of both human and animal is what makes sense. Also in LEO on an AG station with many gravity levels. The simplest solution is to do in depth monitoring of all the humans working there logging electronically there time at various G levels and microgravity and recording all their health (including cognitive and emotional) parameters daily with a combination of passive monitoring and more engaging diagnostic processes. The humans aren't controlled as to what time needs to be at different levels of acceleration, but the animals are and their regimes include breeding experiments and even in some cases dissection and vivisection (and lets try not to be too squeamish about this please).  Some of the humans will be involved in the animal research but I see a lot of other research and activity at such a station.
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Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #58 on: 06/01/2016 06:24 PM »
<snip>
Plus a habitat with artificial gravity for mice is not that hard, you don't need a large diameter. It would not even be too hard to have two levels with moon and Mars gravity.
Why wouldn't you need the same diameter as for humans? Mice are subject to motion sickness and tend to turn their heads a lot faster than humans do I think.

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #59 on: 06/01/2016 06:43 PM »
<snip>
Plus a habitat with artificial gravity for mice is not that hard, you don't need a large diameter. It would not even be too hard to have two levels with moon and Mars gravity.
Why wouldn't you need the same diameter as for humans? Mice are subject to motion sickness and tend to turn their heads a lot faster than humans do I think.
But the gradient over the body height (or even body length if they are climbing) is so much smaller than a human, at a radius of 2 meters for a mouse that is the equivalent of a 40 meter radius for a human if you measure the mouse length wise and more like 100 meters if the mouse is on all fours. That would allow for testing of 1 g at ~20rpm .3 at ~12rpm and .1g at ~6 rpm.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #60 on: 06/01/2016 08:13 PM »
The gravity gradient sure, but from everything I've read, the limit for diameter/rpm is motion sickness caused by turning the subject's head around any axis other than the rotational axis of the environment.

When you (or your mouse) turn your head in a rotating environment, the angular velocity of the centrifuge and the angular velocity of your head cross multiply, resulting in a perceived rotation around a different axis than the one you're turning your head at. Since that's not what your eyes are seeing, if the perceived angular velocity is too high, the result is motion sickness. The size of the head isn't important, what matters is its angular velocity and that of the environment.

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #61 on: 06/01/2016 08:29 PM »
The gravity gradient sure, but from everything I've read, the limit for diameter/rpm is motion sickness caused by turning the subject's head around any axis other than the rotational axis of the environment.

When you (or your mouse) turn your head in a rotating environment, the angular velocity of the centrifuge and the angular velocity of your head cross multiply, resulting in a perceived rotation around a different axis than the one you're turning your head at. Since that's not what your eyes are seeing, if the perceived angular velocity is too high, the result is motion sickness. The size of the head isn't important, what matters is its angular velocity and that of the environment.

Interesting, wouldn't a smaller animal with a higher metabolic rate like a mouse, be already used to higher angular velocities because they rotate their heads through much smaller circles (1cm radius vs 10 or 15 for a human) more quickly?
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #62 on: 06/01/2016 09:08 PM »
My understanding is different. What causes motion sickness is the difference of angular movement between head and feet. Which is a lot bigger for humans than mice. So a centrifuge can be as much smaller as the body of a mouse is.


Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #63 on: 06/01/2016 09:15 PM »
About humans reproducing under lower gravity. I am sure scientists would be very, very interested. But doing such a program from beginning of pregnancy to at least adolescence would be a long term program. Even with very optimistic cost estimates any space agency could not do that below 20 billion $. Chance of that money provided? Exactly ZERO. A lower cost estimate anyone?

Would Elon Musk be interested? Certainly. Would he do it? Chance again exactly ZERO. He would build his Mars base and let people have children there.

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #64 on: 06/01/2016 09:40 PM »
About humans reproducing under lower gravity. I am sure scientists would be very, very interested. But doing such a program from beginning of pregnancy to at least adolescence would be a long term program. Even with very optimistic cost estimates any space agency could not do that below 20 billion $. Chance of that money provided? Exactly ZERO. A lower cost estimate anyone?

Would Elon Musk be interested? Certainly. Would he do it? Chance again exactly ZERO. He would build his Mars base and let people have children there.

I hope they do it with primates between now and then
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Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #65 on: 06/01/2016 09:46 PM »
My understanding is different. What causes motion sickness is the difference of angular movement between head and feet. Which is a lot bigger for humans than mice. So a centrifuge can be as much smaller as the body of a mouse is.
Well, if you think about it, there is no difference in angular movement if you are standing on the inside of a centrifuge with your head "up" towards the center. Your feet rotate at the same rate as your head. There's a difference in linear velocity, but we can't perceive velocity. The problem is with the cross coupling of angular velocities.

There are lots of discussion on the net of all this, here's one. If you can provide a source for your belief, I'd be happy to look at it.

https://books.google.com/books?id=Z5VTZGRQvFoC&pg=PA38#v=onepage&q&f=false
« Last Edit: 06/01/2016 09:49 PM by RDoc »

Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #66 on: 06/01/2016 10:06 PM »
Interesting, wouldn't a smaller animal with a higher metabolic rate like a mouse, be already used to higher angular velocities because they rotate their heads through much smaller circles (1cm radius vs 10 or 15 for a human) more quickly?
The issue isn't how fast you (or your mouse) turn your head on the earth or in any other non-rotating environment. There, your vestibular system perceives the same rotation your eyes do, so everything is cool.

However, in a rotating environment, the rotation of the environment and the rotation of your head produce a "cross coupling", a vector cross product rotation, that has a component at right angles to both rotations. Your vestibular system thinks you are rotating your head around a different axis than your eyes do which is bad.

For example, if you are standing upright on the inside of a centrifuge and shake your head "no", side to side, your inner ear will think you twisted it with a shoulder to shoulder motion as well. Since your eyes don't see that, if the effect is strong enough, you'll experience motion sickness.

Apparently in high rotational rate centrifuges they sometimes use head restraints to avoid this.
« Last Edit: 06/01/2016 10:14 PM by RDoc »

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #67 on: 06/01/2016 10:13 PM »
Interesting, wouldn't a smaller animal with a higher metabolic rate like a mouse, be already used to higher angular velocities because they rotate their heads through much smaller circles (1cm radius vs 10 or 15 for a human) more quickly?
The issue isn't how fast you (or your mouse) turn your head on the earth or in any other non-rotating environment. There, your vestibular system perceives the same rotation your eyes do, so everything is cool.

However, in a rotating environment, the rotation of the environment and the rotation of your head produce a "cross coupling", a vector cross product rotation, that has a component at right angles to both rotations. Your vestibular system thinks you are rotating your head around a different axis than your eyes do which is bad.

For example, if you are standing upright on the inside of a centrifuge and nod forward and back, your inner ear will think you twisted it with a shoulder to shoulder side wise motion as well. Since your eyes don't see that, if the effect is strong enough, you'll experience motion sickness.

Apparently in high rotational rate centrifuges they sometimes use head restraints to avoid this.

But, how pronounced that cross coupling must depend on the relative diameters of the two circular motions and the relative amounts of angular momentum. The mouses motion is a much smaller circle than a humans.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #68 on: 06/01/2016 10:23 PM »
But, how pronounced that cross coupling must depend on the relative diameters of the two circular motions and the relative amounts of angular momentum. The mouses motion is a much smaller circle than a humans.
No, it's just angular velocity, rpm, and has nothing to do with the mass of the object, which would be momentum, or it's size.

Consider a penny glued to the center of a truck tire on the end of the axle. As the truck goes down the road, the penny and the tread on the tire rotate at exactly the same rpm, angular velocity. Actually, if you glue the penny on the sidewall just in from the edge, it still rotates at the same angular velocity as well.
« Last Edit: 06/01/2016 10:24 PM by RDoc »

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #69 on: 06/01/2016 10:26 PM »
But, how pronounced that cross coupling must depend on the relative diameters of the two circular motions and the relative amounts of angular momentum. The mouses motion is a much smaller circle than a humans.
No, it's just angular velocity, rpm, and has nothing to do with the mass of the object.

Consider a penny glued to the center of a truck tire on the end of the axle. As the truck goes down the road, the penny and the tread on the tire rotate at exactly the same rpm, angular velocity. Actually, if you glue the penny on the sidewall just in from the edge, it still rotates at the same angular velocity as well.

But the penny is not making these coupled motions you speak of where there are intersecting planes of rotation. I still don't accept this argument without some experimental data on mice at >1g in a centrifuge here on earth, have you got some links to such?
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #70 on: 06/01/2016 10:36 PM »
But the penny is not making these coupled motions you speak of where there are intersecting planes of rotation. I still don't accept this argument without some experimental data on mice at >1g in a centrifuge here on earth, have you got some links to such?
Follow the link I gave earlier, it explains the problem in terms of angular velocity.

https://books.google.com/books?id=Z5VTZGRQvFoC&pg=PA38#v=onepage&q&f=false

If you're unsure of how angular velocity vectors interact, there are a bunch of videos and explanations in the various physics lessons online. They tend to use calculus or linear algebra notation however. There are also some discussions and illustrations of the "right hand rule" that may be more accessible.
« Last Edit: 06/01/2016 10:37 PM by RDoc »

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #71 on: 06/01/2016 10:43 PM »
But the penny is not making these coupled motions you speak of where there are intersecting planes of rotation. I still don't accept this argument without some experimental data on mice at >1g in a centrifuge here on earth, have you got some links to such?
Follow the link I gave earlier, it explains the problem in terms of angular velocity.

https://books.google.com/books?id=Z5VTZGRQvFoC&pg=PA38#v=onepage&q&f=false

If you're unsure of how angular velocity vectors interact, there are a bunch of videos and explanations in the various physics lessons online. They tend to use calculus or linear algebra notation however. There are also some discussions and illustrations of the "right hand rule" that may be more accessible.

No it does not contain what I asked about, it describes gravity + centrifugal tests with humans at speeds up to 23rpm (which is less than needed for the mouse experiments in space with the 2 meter radius device at 1g) but it did not describe anything about testing with mice in those environments. It did discuss mice and other animals in microgravity.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #72 on: 06/01/2016 10:51 PM »
No it does not contain what I asked about, it describes gravity + centrifugal tests with humans at speeds up to 23rpm (which is less than needed for the mouse experiments in space with the 2 meter radius device at 1g) but it did not describe anything about testing with mice in those environments. It did discuss mice and other animals in microgravity.
Hmm, you might want to do some of your own research, but here's a reference to rat motion sickness testing. Notice that they only talk about rotational rate, and it's in the same range as for humans 10-25 rpm or so.

https://books.google.com/books?id=Jr-m3bMy7IUC&pg=PA100&lpg=PA100#v=onepage&q&f=false

Offline nadreck

Re: Artificial Gravity - Why Weight?
« Reply #73 on: 06/01/2016 10:53 PM »
No it does not contain what I asked about, it describes gravity + centrifugal tests with humans at speeds up to 23rpm (which is less than needed for the mouse experiments in space with the 2 meter radius device at 1g) but it did not describe anything about testing with mice in those environments. It did discuss mice and other animals in microgravity.
Hmm, you might want to do some of your own research, but here's a reference to rat motion sickness testing. Notice that they only talk about rotational rate, and it's in the same range as for humans 10-25 rpm or so.

https://books.google.com/books?id=Jr-m3bMy7IUC&pg=PA100&lpg=PA100#v=onepage&q&f=false

Then in that case a 2 meter radius system would work with mice.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline RDoc

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Re: Artificial Gravity - Why Weight?
« Reply #74 on: 06/02/2016 03:31 AM »
Yeah, OK, whatever.

Online Eric Hedman

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Re: Artificial Gravity - Why Weight?
« Reply #75 on: 06/02/2016 03:51 AM »
Here is a perspective on the problems Scott Kelly's 340 days in space are causing him:

http://abcnews.go.com/Technology/wireStory/nasas-yearlong-spaceman-sore-feet-fatigue-39373874

Offline Hotblack Desiato

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Re: Artificial Gravity - Why Weight?
« Reply #76 on: 06/02/2016 07:00 AM »
Regarding the momentum gradient in small centrifuges: okay, it is a problem, but how big is it?

People have been on small maritime ships for extended periods of time (months, years, decades), yes some had motion sickness, but many others have worked around it. And the motions of ships hit by waves are much more complex and random than a slowly yet steady spinning spaceship. So, people will adapt to it (or sit with motion sickness for 4-6 months in their cabins, trying to get around it). it'll not be pleasant, but better than the alternative.

Offline hydra9

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Re: Artificial Gravity - Why Weight?
« Reply #77 on: 06/02/2016 04:42 PM »
Deploying artificial gravity habitats to Mars would not be difficult to do if we used chemical rockets and propellant depots.


SLS Derived Artificial Gravity Habitats for Space Stations and Interplanetary Vehicles

http://newpapyrusmagazine.blogspot.com/2016/04/sls-derived-artificial-gravity-habitats.html


First Human Voyages to the Martian Moons Using SLS and IVF Derived Technologies

http://newpapyrusmagazine.blogspot.com/2015/11/first-human-voyages-to-martian-moons.html

Marcel

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Re: Artificial Gravity - Why Weight?
« Reply #78 on: 06/04/2016 03:32 PM »
I don't get it. The record stay in space is 438 days. Mars would be 900 days. There are demonstrable health effects which increase with time in zero g.

For humanity to go to Mars, or space, rotating habitats are a must. Why not develop this technology? It's difficult but necessary.


Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #79 on: 06/04/2016 04:09 PM »
I don't get it. The record stay in space is 438 days. Mars would be 900 days. There are demonstrable health effects which increase with time in zero g.

For humanity to go to Mars, or space, rotating habitats are a must. Why not develop this technology? It's difficult but necessary.

No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Offline Lee Jay

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Re: Artificial Gravity - Why Weight?
« Reply #80 on: 06/04/2016 04:40 PM »
No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Only if there's a fast transit, only if everyone goes to the surface, and only if Mars gravity is safe for two years, none of which has been demonstrated.

Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #81 on: 06/04/2016 05:02 PM »
No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Only if there's a fast transit, only if everyone goes to the surface, and only if Mars gravity is safe for two years, none of which has been demonstrated.

According to the medical experts I referenced earlier in the thread who study the issue, you are absolutely correct.

Offline The Amazing Catstronaut

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Re: Artificial Gravity - Why Weight?
« Reply #82 on: 06/04/2016 05:10 PM »
Musk recently mentioned three month transit times if I'm recalling everything correctly. Under such conditions the need for artificial gravity would be significantly reduced.

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Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #83 on: 06/04/2016 05:17 PM »
No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Only if there's a fast transit, only if everyone goes to the surface, and only if Mars gravity is safe for two years, none of which has been demonstrated.

Wrong. He talked about a full mission. And remember the first mission planned by NASA is an orbital mission. Without rotating habitats.

Offline stoker5432

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Re: Artificial Gravity - Why Weight?
« Reply #84 on: 06/04/2016 05:23 PM »
No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Only if there's a fast transit, only if everyone goes to the surface, and only if Mars gravity is safe for two years, none of which has been demonstrated.

Wrong. He talked about a full mission. And remember the first mission planned by NASA is an orbital mission. Without rotating habitats.

Poor Scott Kelly. They subjected him to almost of year of microgravity, but they had it all figured out. I'm sure he'll relish that thought as he's going through the significant amount of rehab he need's from his mission.

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Re: Artificial Gravity - Why Weight?
« Reply #85 on: 06/04/2016 05:38 PM »
No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Only if there's a fast transit, only if everyone goes to the surface, and only if Mars gravity is safe for two years, none of which has been demonstrated.

Wrong. He talked about a full mission. And remember the first mission planned by NASA is an orbital mission. Without rotating habitats.

Poor Scott Kelly. They subjected him to almost of year of microgravity, but they had it all figured out. I'm sure he'll relish that thought as he's going through the significant amount of rehab he need's from his mission.
Basically, yeah. The Russians have sent 6 astronauts for trips over 300 days, plus the one that joined Scott. And one of those trips was 437 days long, significantly longer than Scott Kelly's trip. The cosmonaut actually walked from the capsule on his own two legs, stole a cigarette from his comrade, and said, "We can fly to Mars."

It is a little crazy to me that we'd prefer to guinea pig more astronauts in LEO when we know the risk is low enough that they'll be able to follow through with the trip. At this point, we're going to do it either way, so we're pretty much putting astronauts at risk just so we put a finer point on the numbers.
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Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #86 on: 06/04/2016 06:08 PM »
Poor Scott Kelly.

Ask him if he would reverse his decision to quit when he is offered a microgravity trip to Mars in 3 years.

Unfortunately he is probably going to be too old in 10 years.

Offline stoker5432

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Re: Artificial Gravity - Why Weight?
« Reply #87 on: 06/04/2016 07:40 PM »
Poor Scott Kelly.

Ask him if he would reverse his decision to quit when he is offered a microgravity trip to Mars in 3 years.

Unfortunately he is probably going to be too old in 10 years.

Would he even have that choice now? What about the career radiation limits?

Offline stoker5432

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Re: Artificial Gravity - Why Weight?
« Reply #88 on: 06/04/2016 07:49 PM »
The cosmonaut actually walked from the capsule on his own two legs, stole a cigarette from his comrade, and said, "We can fly to Mars."

Not saying your wrong, but I really dislike this rational. People walk out of hospitals everyday that are in terrible shape and have no business doing anything strenuous. Kelly himself is confirming this with his recent comments on his overall health. We don't know the detailed medical records of any of these people.

In Mars's case I think speed is the best solution as of now. I really like that Elon has indicated he wants 3 months travel time to Mars.
« Last Edit: 06/04/2016 07:52 PM by stoker5432 »

Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #89 on: 06/04/2016 08:05 PM »
In this discussion it seems relevant that Musk said at RecodeDotNet that they are aiming for 90 day trips times to mars (and back I presume) and 30 days later. Which is interestingly very much in line with what I was hoping for. Such short trip times (if they can indeed make them happen), should make artificial gravity unnecessary. Of course there is still the problem of the low Martian gravity for the duration of the stay. Not sure how long they are planning to keep people there initially. That will be interesting to learn (probably in September).

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #90 on: 06/04/2016 08:19 PM »
Not sure how long they are planning to keep people there initially. That will be interesting to learn (probably in September).

My best guess, some will return, when the next crew arrives, some will stay.

Offline The Amazing Catstronaut

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Re: Artificial Gravity - Why Weight?
« Reply #91 on: 06/04/2016 08:32 PM »
Speed is also the psychologically healthy option. You're going to Mars to get to Mars, not for staring out into the endless forever of nothing during transfer.
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Offline Elmar Moelzer

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Re: Artificial Gravity - Why Weight?
« Reply #92 on: 06/04/2016 09:06 PM »
My best guess, some will return, when the next crew arrives, some will stay.
Well that would imply at least 2 years stay, which I find a rather risky proposition for a first mission. The long stay would also require a lot more consumables, habitats, etc. I would assume that they would only stay for a few weeks initially (as long as practical given return trajectories, etc). I might be wrong, though.
« Last Edit: 06/04/2016 09:06 PM by Elmar Moelzer »

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #93 on: 06/04/2016 09:18 PM »
My best guess, some will return, when the next crew arrives, some will stay.
Well that would imply at least 2 years stay, which I find a rather risky proposition for a first mission. The long stay would also require a lot more consumables, habitats, etc. I would assume that they would only stay for a few weeks initially (as long as practical given return trajectories, etc). I might be wrong, though.

That's quite possible, I would not claim it as certain. However I am not that concerned about supplies. MCT is supposed to transport 100 people and on that first flight there may be 10, also unmanned precursor missions should have placed extra supplies. There's local water and air supply too.

I am under the impression it will be a permanent base from the first landing.

Isn't the planned NASA mission for 300 days? That's not a full synod but a long term stay too.

Online Coastal Ron

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Re: Artificial Gravity - Why Weight?
« Reply #94 on: 06/04/2016 10:05 PM »
In this discussion it seems relevant that Musk said at RecodeDotNet that they are aiming for 90 day trips times to mars (and back I presume) and 30 days later. Which is interestingly very much in line with what I was hoping for. Such short trip times (if they can indeed make them happen), should make artificial gravity unnecessary. Of course there is still the problem of the low Martian gravity for the duration of the stay. Not sure how long they are planning to keep people there initially. That will be interesting to learn (probably in September).

For the foreseeable future, Mars is the highest gravity location safe for humans beyond Earth, yet it only has 1/3 the gravity of Earth.  If it turns out that low gravity has deleterious effects like no-gravity does, artificial gravity stations at the point of exploration/colonization may be required for long duration stays.

While maybe low gravity effects can be mitigated by medical advancements or even genetic alterations, it's unlikely that everyone that goes to space will be able to acclimate quickly, so I think artificial gravity stations will be necessary going forward.

The challenge is that any station big enough to provide refuge for a colony is currently too big to build or move using our current abilities and cost structures.  And it's mainly the cost of moving mass to space that needs to come down, since I believe that we have the technology necessary to build at least the 1st generation of rotating space stations.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Mark K

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Re: Artificial Gravity - Why Weight?
« Reply #95 on: 06/04/2016 11:22 PM »

The challenge is that any station big enough to provide refuge for a colony is currently too big to build or move using our current abilities and cost structures.  And it's mainly the cost of moving mass to space that needs to come down, since I believe that we have the technology necessary to build at least the 1st generation of rotating space stations.

"Refuge for a colony" Why would you not just create an artificial gravity area on the surface by the colony? You would just need a banked train really.

That has got to be simpler than sending people up to space?

Offline philw1776

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Re: Artificial Gravity - Why Weight?
« Reply #96 on: 06/04/2016 11:49 PM »
It's ironic that space fans have no problem assuming all kinds of advances in aerospace enabling a Mars mission which we can't do today while they ignore the incredible biotech and medicine revolution ongoing which has at least the possibility of mitigating both radiation and zero gee problems with primates.
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Offline ZachF

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Re: Artificial Gravity - Why Weight?
« Reply #97 on: 06/13/2016 06:51 AM »
Gas stations in space with prepositioned supplies and propellant are the fastest way to send crew to Mars, but it appears to be limited to about 3 months one way with existing technology.
I think there was a concept for a VASIMIR based mission with a slightly over 30 day trip time. MSNW is also working on a new fusion drive that could result in 30 day trip times with a space craft that fits into a single BFR launch (with payload to spare) or a single SLS launch (with no margin).
There's a 39-day VASIMR mission described here:

http://www.adastrarocket.com/Andrew-SPESIF-2011.pdf

If I'm reading the paper correctly, the 39 day mission requires a 200MW nuclear reactor with power density of around 0.8kg/kW.   It mentions in passing that 4kg/kW is the best that's currently achievable.

A Molten Salt reactor could probably do <1kg/kw. Read up on the "fireball" reactor designed for a nuclear powered plane.

http://energyfromthorium.com/pdf/ORNL-2387.pdf

Offline ZachF

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Re: Artificial Gravity - Why Weight?
« Reply #98 on: 06/13/2016 07:07 AM »
I don't get it. The record stay in space is 438 days. Mars would be 900 days. There are demonstrable health effects which increase with time in zero g.

For humanity to go to Mars, or space, rotating habitats are a must. Why not develop this technology? It's difficult but necessary.

No, I don't get it. Rotating habitats are not a must. They are not difficult, they are unnecessary. That's what Charles Bolden said in a Congress hearing. They have learned enough about mitigating zero gravity problems for a Mars mission duration.

Could many of the muscular/skeletal problems of low Mars G be mitigated by just wearing a weight suit? I know it might not have a impact on other areas, but just curious.

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #99 on: 06/13/2016 08:01 AM »
Could many of the muscular/skeletal problems of low Mars G be mitigated by just wearing a weight suit? I know it might not have a impact on other areas, but just curious.

Let's see what kind, if any, problems do arise. I have my personal pet idea on dealing with any problems. Vibration plates. Any remaining changes will hopefully be just adjustment to a new environment.

http://www.fitday.com/fitness-articles/fitness/equipment/do-vibration-plates-really-work.html

From the comments it seems they need to be used with caution. The comments are worth reading along with the article.

Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #100 on: 06/13/2016 04:34 PM »
Could many of the muscular/skeletal problems of low Mars G be mitigated by just wearing a weight suit? I know it might not have a impact on other areas, but just curious.

Would a weighted suit prevent vision impairment due to low gravity? Just wondering.

See "Microgravity and Vision Impairments in Astronauts" by Dr. Erik Seedhouse (ISBN 978-3-319-17870-7).

Centrifuging might provide benefits to the entire body, not just the musculoskeletal system.
« Last Edit: 06/13/2016 04:37 PM by WindyCity »

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #101 on: 06/13/2016 05:04 PM »
In a recent Congress hearing NASA administror Bolden stated that the present theory on the causes of vision impairment is high CO2 content in the ISS atmosphere. They have reduced CO2. Final results are not yet in though.

Online Robotbeat

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Re: Artificial Gravity - Why Weight?
« Reply #102 on: 06/13/2016 05:16 PM »
The cosmonaut actually walked from the capsule on his own two legs, stole a cigarette from his comrade, and said, "We can fly to Mars."

Not saying your wrong, but I really dislike this rational. People walk out of hospitals everyday that are in terrible shape and have no business doing anything strenuous. Kelly himself is confirming this with his recent comments on his overall health. We don't know the detailed medical records of any of these people.

In Mars's case I think speed is the best solution as of now. I really like that Elon has indicated he wants 3 months travel time to Mars.
Scott (edited) Kelly also spent twice as long in microgravity as you would in even a NASA-esque 6 month trip to Mars.

A 100 day or 3 month trip would be no problem.
« Last Edit: 06/13/2016 08:00 PM by Robotbeat »
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Online Robotbeat

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Re: Artificial Gravity - Why Weight?
« Reply #103 on: 06/13/2016 05:17 PM »
Gas stations in space with prepositioned supplies and propellant are the fastest way to send crew to Mars, but it appears to be limited to about 3 months one way with existing technology.
I think there was a concept for a VASIMIR based mission with a slightly over 30 day trip time. MSNW is also working on a new fusion drive that could result in 30 day trip times with a space craft that fits into a single BFR launch (with payload to spare) or a single SLS launch (with no margin).
There's a 39-day VASIMR mission described here:

http://www.adastrarocket.com/Andrew-SPESIF-2011.pdf

If I'm reading the paper correctly, the 39 day mission requires a 200MW nuclear reactor with power density of around 0.8kg/kW.   It mentions in passing that 4kg/kW is the best that's currently achievable.

A Molten Salt reactor could probably do <1kg/kw. Read up on the "fireball" reactor designed for a nuclear powered plane.

http://energyfromthorium.com/pdf/ORNL-2387.pdf
Umm, a plane has the benefit of pumping heat into the atmosphere. In space, you have to radiate it.

Radiators are what kill the chance at high specific power nuclear reactors in orbit.

Also, solar can do on the order of 1kW/kg.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline philw1776

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Re: Artificial Gravity - Why Weight?
« Reply #104 on: 06/13/2016 06:28 PM »
We need to dissect Mark Kelly to put an end to the speculation about health effects.

#dissectMarkKellyNow
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Offline philw1776

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Re: Artificial Gravity - Why Weight?
« Reply #105 on: 06/13/2016 07:23 PM »
BOTH twins.  You need a control.
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Re: Artificial Gravity - Why Weight?
« Reply #106 on: 06/13/2016 07:50 PM »
They are doing research on astros coming back from micro-g all the time:

Terry W. Virts ‏@AstroTerry  4h4 hours ago
My last day in the magnet- today was my landing+1 year final MRI, studying my brain and eyesight changes

But yeah, back on to the topic of artificial gravity.

Offline stoker5432

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Re: Artificial Gravity - Why Weight?
« Reply #107 on: 06/13/2016 07:52 PM »
Mark Kelly also spent twice as long in microgravity as you would in even a NASA-esque 6 month trip to Mars.

Scott Kelly was the one who spent 340 days in space.

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Re: Artificial Gravity - Why Weight?
« Reply #108 on: 06/13/2016 08:01 PM »
Mark Kelly also spent twice as long in microgravity as you would in even a NASA-esque 6 month trip to Mars.

Scott Kelly was the one who spent 340 days in space.
How can you know for sure?? ;)

(Thanks, edited)
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Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #109 on: 06/14/2016 05:36 AM »
In a recent Congress hearing NASA administror Bolden stated that the present theory on the causes of vision impairment is high CO2 content in the ISS atmosphere. They have reduced CO2. Final results are not yet in though.

Interesting. A real plus, if true.

Offline JamesH65

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Re: Artificial Gravity - Why Weight?
« Reply #110 on: 06/14/2016 09:49 AM »
The cosmonaut actually walked from the capsule on his own two legs, stole a cigarette from his comrade, and said, "We can fly to Mars."

Not saying your wrong, but I really dislike this rational. People walk out of hospitals everyday that are in terrible shape and have no business doing anything strenuous. Kelly himself is confirming this with his recent comments on his overall health. We don't know the detailed medical records of any of these people.

In Mars's case I think speed is the best solution as of now. I really like that Elon has indicated he wants 3 months travel time to Mars.
Scott (edited) Kelly also spent twice as long in microgravity as you would in even a NASA-esque 6 month trip to Mars.

A 100 day or 3 month trip would be no problem.

I think it would be a problem, I think NASA/Russia might be the only people who really know.

Offline CW

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Re: Artificial Gravity - Why Weight?
« Reply #111 on: 06/19/2016 06:52 PM »
Having a big spaceship with two counter-rotating habitat toruses in LEO (with e.g. a diameter of 100m and rotating at up to 4rpm) might have a surprising and very lucrative business model that comes with it. Think about it:

- When a launch window to Mars is not open for the best of 2 years, use the spaceship as a hotel for truly rich people who want to enjoy the LEO view under Earth or Mars gravity once in a while. There are truckloads of true multi-millionaires available who don't know what to do with their wealth, except taking a luxury ride on a space rocket to a spaceship to be able to talk about it at cocktail parties, where they can recruit more well-paying customers.
- Offer trips to the LEOing 'hotel' for initially 1 million USD per person and week. With room for up to e.g. 100 persons on the ship, there is a maximum business opportunity of 100 million USD per week, or up to 5.2 billion USD per year.
- With each load of ship guests, transport 100+ metric tons of fuel and cargo into LEO and fill up the large spaceship tanks while using the fully reusable super heavy lift vehicle (SHLV).
- Assuming an SHLV manufacturing cost of 100 million USD and 12x full reuse, the SHLV is basically paid for after one fully booked flight to the spaceship 'hotel'.
- For the next reusable 12 flights with an SHLV, a fully booked flight earns SpaceX e.g. 90 million USD or 1.08 billion USD over the lifetime of an SHLV (assuming 10 million USD refurbishment costs per flight).
- Build 4 SHLVs per year and have a maximum yearly space tourism business opportunity of around 4.32 billion USD - per year.
- Reinvest most of this into R&D for colony equipment and more spaceship modules. Start building another spaceship of the same type.
- Use a lot of these tourism earnings to send cargo to Mars in fully automated cargo transporters that do not need life support and all that 'nonsense' that humans would need.
- When the launch window to Mars opens up, close down the tourism business. Get your Mars personnel onto the ship and get on your way.
- While torus spaceship #1 is on its way to Mars, torus spaceship #2 is being built and finished  by using previous space tourism earnings, before spaceship #1 returns back to Earth.
- Meanwhile, colonists traveling to and from Mars can enjoy an Earth-like environment. Gravity simulation can be seamlessly adjusted from 1g to 0.38g to train the colonists' motor neurons for the new environment on Mars. You don't want to get out of your lander and flail around on the surface of the new world like a broken doll, when you should be focused on setting up base ASAP.

----------

This small exercise in creating an answer, as to why it makes sense to build a gravity simulating spaceship, indicates that this presents a way to open up a lucrative business field to get the funds necessary to quickly construct a Mars colony. A spaceship dry mass of e.g. 10'000 metric tons in LEO plus a few 1000 tons of rocket fuel can be put into LEO within 2 years, if an SHLV starts once a week. Hell, maybe the final SHLV can even put 200 metric tons of cargo into LEO in one go, eventually. So what, if it takes 2 years to get the materials into LEO? Why should one care, as long as the bills are paid for by ongoing lucrative business?

From a human perspective, I think that a Mars transit should be like boarding a nice ocean liner. Mars transits should not feel like you being a tuna put into a tin can and the can tossed into empty space for 6 months. I think that Musk's approach will be a multi-phase endeavor, just as his Tesla Motors cars were basically a 3-phase endeavor: Roadster (phase I) -> Model S (phase II) -> Model 3 (phase III) .

I believe that the result of SpaceX's efforts will be a highly refined product, not simply a tin can coasting to and from planets. And I simply can't imagine as to why Musk should have a final product that sucks so badly that you wish you were dead when you're locked up in a tin can for 3 to 6 months.

Out there, there is a star ocean. I think we should not travel these seas in barebone rafts, but in decently sized and cool products that make traveling to and from other planets a fun thing to do (like driving a Tesla car is helluva fun). Simulated gravity is IMO an absolute necessity, for physical but also psychological health. I'm not designing the spaceship, but I think Musk will do the right thing - again :) .
« Last Edit: 06/19/2016 07:32 PM by CW »
Reality is weirder than fiction

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Re: Artificial Gravity - Why Weight?
« Reply #112 on: 08/06/2016 07:53 PM »
www.nasaspaceflight.com/2016/08/nasa-progress-deep-space-habitat-development/

Quote
Specifically, Mr. Hale was interested in how artificial gravity might help address some of the issues facing long-duration microgravity missions.

Mr Gerstenmaier responded that NASA had no studies showing the need for artificial gravity, leading Mr. Hale to point out “you’ve got a lot of really critical things that you’re trying to investigate, and if it pans out that you can’t mitigate one of those risks” with what is currently under development, might artificial gravity be something to consider.

Mr. Gerstenmaier responded that all microgravity considerations are currently mitigatable with the systems in place or under development.

Further, Mr. Gerstenmaier noted that “you’re never gonna provide a partial gravity environment throughout the entire vehicle.

“I think the changes associated with trying to provide partial gravity are so fundamental and large … that I don’t think that’s an area that’s really a problem.  [We have] real problems that need to be addressed, and partial gravity isn’t something that we should be spending quality time on right now.”
 

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #113 on: 08/09/2016 12:58 PM »
They are doing research on astros coming back from micro-g all the time:

Terry W. Virts ‏@AstroTerry  4h4 hours ago
My last day in the magnet- today was my landing+1 year final MRI, studying my brain and eyesight changes

But yeah, back on to the topic of artificial gravity.

Chris, you can probably hazard a more educated guess at my question than anyone else here (maybe Jim?).

I gather there are pro-spin-gravity proponents within NASA leadship and, if not anti-, then "spin-gravity-is-not-a-current-priority" people within NASA.

Any idea what the split is?  My impression is that at best it is 20/80 pro spin gravity...

Offline yg1968

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Re: Artificial Gravity - Why Weight?
« Reply #114 on: 08/09/2016 03:01 PM »
During the NAC teleconference, Gerst mentionned that partial gravity may create additionnal problems. He said that you could likely not have gravity in the entire ship. So you could have vestibular problems when going from zero G to a partial gravity module. Gerst sounded pretty negative on the idea of partial gravity. But he said that the testing of partial gravity on mice on ISS should let them know if partial gravity can be helpful. But he didn't seem to think that it was necessary or helpful for Mars.

See above.

Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #115 on: 08/11/2016 05:13 PM »
Why would the Mars transit vehicle need to have "partial gravity"? The schemes I've heard of involve spinning the space ship at the end of a tether attached to a spent stage or other counterweight. Gerstenmaier's remarks indicate that NASA considers the mission risks of prolonged exposure to zero-G during transit to Mars and partial G on the surface of the planet to be manageable with, I'm guessing, exercise and perhaps medications. He indicates that the cost of implementing artificial gravity technology would not be worth it. I've encountered opinions that say otherwise. The hazards of prolonged zero-G are more, well, weighty, that Gerst's words point out.

Offline stoker5432

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Re: Artificial Gravity - Why Weight?
« Reply #116 on: 08/11/2016 06:44 PM »
SEP

Offline mvpel

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Re: Artificial Gravity - Why Weight?
« Reply #117 on: 08/11/2016 08:41 PM »
A relevant blast from the past in the NSF Forum "HLV / SLS / Orion / Constellation" section:

Artificial Gravity for Mars vehicle - started May 4, 2008
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline philw1776

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Re: Artificial Gravity - Why Weight?
« Reply #118 on: 08/13/2016 02:26 PM »
SEP

Even scaled up several powers of 10 any low thrust SEP acceleration gravity would be inconsequential. 
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline stoker5432

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Re: Artificial Gravity - Why Weight?
« Reply #119 on: 08/13/2016 04:20 PM »
SEP

Even scaled up several powers of 10 any low thrust SEP acceleration gravity would be inconsequential.

I thought I had deleted that post. Oh well. This was in reference to the spinning of the entire spacecraft which would not be possible using SEP. NASA and SEP are joined at the hip.

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #120 on: 08/15/2016 05:10 PM »
SEP

Even scaled up several powers of 10 any low thrust SEP acceleration gravity would be inconsequential.

I thought I had deleted that post. Oh well. This was in reference to the spinning of the entire spacecraft which would not be possible using SEP. NASA and SEP are joined at the hip.

Not sure why you think SEP and spin gravity are mutually exclusive?

Spin gravity spacecraft need to have a "sun-side" and a "star-side", because if your spin section is of any significant size, you'll need solar panels/radiators on the spin section itself. Also, you want the solar panels in constant sun and the radiators in constant shadow despite the spin. So the spin axis always points to the sun, and since your spinning spacecraft probably has a stationary/stabilised central axis section to point communication antenna dishes accurately, it would make sense to put a SEP on each end of that central axis to balance the loads.  The thrust vector is radial/perpendicular to the axis of spin, which works because your trajectory is spiraling out at a tangent to the sun anyway.

Extra bonus of this config is that you get to call your ship a TIE (twin ion engine) ;)

Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #121 on: 08/17/2016 06:02 AM »
An excellent article on the technology and challenges of spinning spacecraft to produce artificial gravity:

http://chapters.marssociety.org/usa/oh/aero2.htm

Offline Impaler

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Re: Artificial Gravity - Why Weight?
« Reply #122 on: 08/17/2016 08:09 AM »
SEP

Even scaled up several powers of 10 any low thrust SEP acceleration gravity would be inconsequential.

I thought I had deleted that post. Oh well. This was in reference to the spinning of the entire spacecraft which would not be possible using SEP. NASA and SEP are joined at the hip.

Not sure why you think SEP and spin gravity are mutually exclusive?

 The thrust vector is radial/perpendicular to the axis of spin, which works because your trajectory is spiraling out at a tangent to the sun anyway.


No the thrust vector can swing around a good deal in order to capture into a planets gravity well, though the thrust vector is always confined to the 2D plane of the heliocentric orbit.  Your design would need to be modified by having a hinged 'wrist' under the engine count to gimbal them along with long boom arms to the propellant plumes don't strike the craft.

Personally I would go with a non rotating  structural axis perpendicular to the orbital plane, on both ends are the solar arrays which remain pointed at the sun, habitation, propellant and engine pods are in stacks of rings along the central axis, this allows a clear path for thrust in any direction.

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #123 on: 08/18/2016 10:14 AM »
No the thrust vector can swing around a good deal in order to capture into a planets gravity well, though the thrust vector is always confined to the 2D plane of the heliocentric orbit.  Your design would need to be modified by having a hinged 'wrist' under the engine count to gimbal them along with long boom arms to the propellant plumes don't strike the craft.

Personally I would go with a non rotating  structural axis perpendicular to the orbital plane, on both ends are the solar arrays which remain pointed at the sun, habitation, propellant and engine pods are in stacks of rings along the central axis, this allows a clear path for thrust in any direction.

Fair enough, but not sure why you think SEP would be used during capture into any gravity well? That doesn't seem well suited to its strengths imo.  It was only done with Dawn because it was low mass and they weren't in a hurry, and even then it took a couple months to settle into a working orbit around Ceres.   Especially for HSF, chemical propulsion can more effficiently give the deltaV required when leaving/arriving at gravity wells, but  SEP will come into its own during the cruise phases.

As far as avoiding propellent plumes impacting on the craft, the modules on the non-rotating axis will probably be quite large/long themselves: making sure there's no conflict would require some planning, but shouldn't be a big issue since the propellent output isn't exactly dense.

Offline envy887

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Re: Artificial Gravity - Why Weight?
« Reply #124 on: 10/03/2016 04:58 PM »
The ITS spacecraft is big enough to spin at 2 RPM and produce .25 m/s of acceleration at the rim.

Is that enough gravity to be useful for things like eating, showing, using a toilet, settling dust, and other things that are a giant pain in 0 g?

Online Eric Hedman

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Re: Artificial Gravity - Why Weight?
« Reply #125 on: 10/26/2016 05:03 PM »
I'm not sure if this is the right place, but I found this article about lower back muscle atrophy:

http://www.cnn.com/2016/10/26/health/astronaut-back-pain-spine-health-space/index.html

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #126 on: 02/04/2017 03:11 AM »
It's ironic that space fans have no problem assuming all kinds of advances in aerospace enabling a Mars mission which we can't do today while they ignore the incredible biotech and medicine revolution ongoing which has at least the possibility of mitigating both radiation and zero gee problems with primates.

The advances in biotech are great, but it isn't magic.  My own phd in immunology only served to convince me that the engineering problems of spin gravity are far easier to solve than pharmaceutical mitigation of long-term symptoms from microgravity.  Because we can only use drugs to trigger/block processes which our genomes already possess the code for.  Radiation levels in space, for example, might be something we will treat using drugs, because life has always had to deal with radiation, albeit at lower levels.  We will probably develop upon the existing drugs that will enhance the radiation repair processes we already possess.

However, in the ~4 billion years of evolution on Earth.  Gravity has always been 9.81 m/s2.  Neutral buoyancy is as close as we can get, but it is not the same (e.g. even the simplest multicellular creatures can determine up from down).  A reasonable prediction therefore is that there is no drug/combination of drugs that can properly deal with extended microgravity over the long term (multiple years/generations).  The open question is whether lunar or martian gravity is enough, or whether we will regularly have to return to spin gravity (higher g-levels) to compensate.

Offline WindyCity

Re: Artificial Gravity - Why Weight?
« Reply #127 on: 02/04/2017 03:40 AM »
The open question is whether lunar or martian gravity is enough, or whether we will regularly have to return to spin gravity (higher g-levels) to compensate.

Precisely. Periodic sessions in a centrifuge might prevent physiological damage from low-g exposure. Experimental study could determine the optimal strength and duration of the treatment. Age, weight, gender, health, etc. would probably all factor into determining appropriate RPMs and time spent aboard the apparatus.  Questions such as, "Would shorter times at >G be equivalent to longer times at G" could be studied. I think that mikelepage is probably right that the nausea and disorientation caused by centrifuging would be easier to counteract than finding a drug or drugs to prevent bone loss, vision problems, muscle atrophy, etc.

Offline Aussie_Space_Nut

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Re: Artificial Gravity - Why Weight?
« Reply #128 on: 02/26/2017 03:08 AM »
I tend to agree with the last few posts here.

1) We absolutley know without any doubt whatsoever that 1g is good for you.

2) We absolutley know without any doubt whatsoever that extended stays in a 0g environment is not good for you.

3) We absolutely know without any doubt whatsoever that many people can get used to a boat being tossed around on the sea. Not everyone, but most people.

We have not needed to do a spin gravity experiment in space up to now because no one intended to stay in a low g or a 0g environment long term. (years)

But we are coming to that time. My hunch is that for due diligence reasons someone will have to put up a long term spin gravity station of some kind to offset the risks. IMHO to not do so is reckless.

2 ITS spaceships linked by a tube in LEO will do. :-)

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #129 on: 02/26/2017 07:57 AM »
We do know without a trace of doubt that going to Mars in microgravity does not pose major problems.

We can not know for sure if Mars gravity is sufficient to keep people healthy. If not it would be a major obstacle for a Mars settlement.

Going outward of Mars may require artificial gravity. That leaves the question if it is needed for all the time or just daily training for an our or so would be enough and people can deal with changing gravity. It is worth trying in LEO before we send out people for long distance trave.

Online Dao Angkan

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Re: Artificial Gravity - Why Weight?
« Reply #130 on: 02/26/2017 11:48 PM »
The ITS spacecraft is big enough to spin at 2 RPM and produce .25 m/s of acceleration at the rim.

Is that enough gravity to be useful for things like eating, showing, using a toilet, settling dust, and other things that are a giant pain in 0 g?

About 1/15 of Mars gravity. A 70kg man could wear a 969kg suit to acclimatise to Mars gravity. It would help with muscle atrophy. Tungsten has a density of 19.25 g/cm3, an average man is said to have a surface area of 19,000 cm2. A Tungsten suit would have to average a thickness of 2.65 cm.

To approximate Earth weight would require an almost 2.7 ton suit with a thickness of 7.32 cm. Not so practical.

Such a suit might also help with radiation shielding.


Offline nacnud

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Re: Artificial Gravity - Why Weight?
« Reply #131 on: 02/27/2017 01:37 AM »
I don't think a heavy suit, or resistance suit, would have the same physiological effects as gravity, natural or artificial.

Online Dao Angkan

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Re: Artificial Gravity - Why Weight?
« Reply #132 on: 02/27/2017 02:42 AM »
Not meant to be the same, just compensate to some degree. Weighted vests can help to halt bone loss, and build muscle. It's the same principle.

On Mars a Tungsten suit would need to average 3mm thickness to approximate Earth weight. That's very practical, and would seem like a sensible practice to have Tungsten lined clothes to maintain fitness.
« Last Edit: 02/27/2017 03:26 AM by Dao Angkan »

Offline guckyfan

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Re: Artificial Gravity - Why Weight?
« Reply #133 on: 02/27/2017 07:43 AM »
About 1/15 of Mars gravity. A 70kg man could wear a 969kg suit to acclimatise to Mars gravity.

That much mass comes with inertia. While weight scales with gravity, inertia is always the same. No way to move around with a ton of mass.

Offline Jet Black

Re: Artificial Gravity - Why Weight?
« Reply #134 on: 02/27/2017 09:14 AM »
The ITS spacecraft is big enough to spin at 2 RPM and produce .25 m/s of acceleration at the rim.

Is that enough gravity to be useful for things like eating, showing, using a toilet, settling dust, and other things that are a giant pain in 0 g?

About 1/15 of Mars gravity. A 70kg man could wear a 969kg suit to acclimatise to Mars gravity. It would help with muscle atrophy. Tungsten has a density of 19.25 g/cm3, an average man is said to have a surface area of 19,000 cm2. A Tungsten suit would have to average a thickness of 2.65 cm.

To approximate Earth weight would require an almost 2.7 ton suit with a thickness of 7.32 cm. Not so practical.

Such a suit might also help with radiation shielding.

a couple of issues there are that it doesn't really help with internal processes such as in the vestibular system, though it may help with compression on the bones. The other issue is inertia - it's not just weight that is the issue, but to accelerate and decelerate all that mass whenever you do anything would be a huge amount of hard work.
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline Rei

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Re: Artificial Gravity - Why Weight?
« Reply #135 on: 02/27/2017 10:03 AM »
Gravity is one of the reasons why I prefer Venus as a destination over Mars; if 8.7 m/s at flight altitude isn't enough then there's no hope for the Moon, Mars, or almost anywhere else in our solar system.  Likewise, if Venus's natural atmospheric radiation shielding isn't enough, then that makes the shielding requirements on other celestial bodies painfully great.

Not that I'm not hopeful that Mars's gravitational issues can be shown to be tolerable or worked around  :)

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #136 on: 03/02/2017 07:48 AM »
Gravity is one of the reasons why I prefer Venus as a destination over Mars; if 8.7 m/s at flight altitude isn't enough then there's no hope for the Moon, Mars, or almost anywhere else in our solar system.  Likewise, if Venus's natural atmospheric radiation shielding isn't enough, then that makes the shielding requirements on other celestial bodies painfully great.

Not that I'm not hopeful that Mars's gravitational issues can be shown to be tolerable or worked around  :)

Gravity is one of the reasons I prefer spin-gravity habitats on/around asteroids ahead of the moon, Mars and Venus ;)  I believe these planetary mass bodies will be significant tourist attractions & work sites for adults, but I think it's going to be a long time before we decide it's okay for pregnant women or families with developing children/teenagers to be anywhere other than 1xg habitats.  Spin gravity habitats which can provide 1xg will need to be large, and therefore must be built in microgravity environments with access to resources (ie around asteroids).

Whether or not non-1xg gravity is "enough" is with respect to adult human health is an open question over the years/lifetime timescale.  On evolutionary time scales however, anything other than exactly 1xg can be expected to produce drastic and unpredictable adaptations to emerge.  Not necessarily bad mind you, just different, and we probably want to quantify the effects of 1xg spin-gravity over generations first.

Offline Rei

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Re: Artificial Gravity - Why Weight?
« Reply #137 on: 03/02/2017 10:13 AM »
Gravity is one of the reasons I prefer spin-gravity habitats on/around asteroids ahead of the moon, Mars and Venus ;)

Re, Venus: What, ~8.7 m/s^2 isn't close enough to 9.81 for you?  ;)

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Spin gravity habitats which can provide 1xg will need to be large, and therefore must be built in microgravity environments with access to resources (ie around asteroids).

You're talking something vastly into the future if you're talking about building whole habitats in space from asteroid materials.

Given that tether experiments in space have had a less than stellar track record, I'd say that counterweighted rollable trusses look to probably be the best option at this point in time.

Offline Lumina

Re: Artificial Gravity - Why Weight?
« Reply #138 on: 03/02/2017 08:37 PM »
What about mice bred in a centrifuge on the ISS?

I believe the Russians have carried out some in-orbit experiments with mice in centrifuges and that the health benefits were dramatic.

If you look at the list of negative health effects from space travel, the negative effects from microgravity are more far reaching and more immediate than the effects from radiation.

If the plan is to mitigate impacts from radiation, it makes sense to also mitigate impacts from microgravity.

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #139 on: 03/04/2017 08:50 AM »
Gravity is one of the reasons I prefer spin-gravity habitats on/around asteroids ahead of the moon, Mars and Venus ;)

Re, Venus: What, ~8.7 m/s^2 isn't close enough to 9.81 for you?  ;)

9.81 is closer to 9.81.  Very close, in fact ::)

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Spin gravity habitats which can provide 1xg will need to be large, and therefore must be built in microgravity environments with access to resources (ie around asteroids).

You're talking something vastly into the future if you're talking about building whole habitats in space from asteroid materials.

Given that tether experiments in space have had a less than stellar track record, I'd say that counterweighted rollable trusses look to probably be the best option at this point in time.

Not quite sure what you mean by counterweighted rollable trusses (I'm assuming you mean baton-stations/tumbling pigeons?).  Agreed on tethers.  There is a third option I'm calling DEployable Spin Gravity Array (DeSGA - small animation attached), which I would put on space craft intended to support humans working out at asteroids.

But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.  You use the regolith as your compressive component, and import (steel) cables from Earth as your tensile component when you want to fuse the whole thing together.  Such massive structures will be much easier to work with in microgravity.


Offline lamontagne

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Re: Artificial Gravity - Why Weight?
« Reply #140 on: 03/05/2017 12:40 AM »


But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.  You use the regolith as your compressive component, and import (steel) cables from Earth as your tensile component when you want to fuse the whole thing together.  Such massive structures will be much easier to work with in microgravity.



How about using basalt fibers to reinforce some form of concrete?
http://novitsky1.narod.ru/babv1.html.htm
Or even basalt fiber to reinforce sintered basalt?  The fiber has higher strength because of the low defects, and the sintered basalt serves as fill.

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #141 on: 03/13/2017 04:09 AM »
But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.  You use the regolith as your compressive component, and import (steel) cables from Earth as your tensile component when you want to fuse the whole thing together.  Such massive structures will be much easier to work with in microgravity.

How about using basalt fibers to reinforce some form of concrete?
http://novitsky1.narod.ru/babv1.html.htm
Or even basalt fiber to reinforce sintered basalt?  The fiber has higher strength because of the low defects, and the sintered basalt serves as fill.

Interesting, I started responding to this days ago but apparently I never posted it.  I googled this at the time and found that the fibers can only be obtained from particular quarries? I wonder how likely we are to find something like this at asteroids. Or were you thinking to ship it from Earth? Must be pretty massive.

Offline Rei

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Re: Artificial Gravity - Why Weight?
« Reply #142 on: 03/13/2017 11:59 AM »
I'm actually building a house out of basalt fibre reinforced concrete

Note that as a general rule, you don't use raw fibres, you use fibres embedded in a plastic binder. I've seen videos from one guy who's building homes just out of raw roving, but from the longevity studies I've seen, I wouldn't trust that. Even if you were only using raw fibre, this would be incompatible with basalt sintering; the fibres lose their strength when you heat them to sintering temperatures. The plastic would be lost first of course. And basalt doesn't sinter well, it likes to fracture. That said, basalt aggregate often makes for a very good concrete. You need a proper binder, though.

I would be hesitant to attempt production of basalt fibre offworld. I've read about the nuances of the production processes and it's not something I'd expect to work well in the "simple / low maintenance / low human involvement" category.  It's tougher than glass fibre production - temperatures are higher, the melt is optically opaque so overhead heating doesn't work well, and various components tend to precipitate out of the mix at different temperatures. Blowing methods would be harder on Mars than on Earth due to the low density (the local environment shouldn't affect the approaches based on drawing from spinnerets)

As for the "particular quarries" thing... that's more a statement of the fact that you can't just use any old basalt and get the same properties.  Each source has to be qualified on its own. Basalt fibre reinforcement is a relatively small (but growing) market these days.  Still, it has a lot of appealing properties. In most regards carbon fibre is significantly superior, but CF is very expensive and requires a lot more energy to produce.  But compared to glass fibre, BFRP is "somewhat better" in almost every measure.
« Last Edit: 03/13/2017 11:59 AM by Rei »

Offline Rei

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Re: Artificial Gravity - Why Weight?
« Reply #143 on: 03/13/2017 12:19 PM »
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Not quite sure what you mean by counterweighted rollable trusses (I'm assuming you mean baton-stations/tumbling pigeons?)

Rollable composite trusses:



Based on the same principle that lets tape measures work, but taken to much more extreme ends - each strand rolls out to a nearly circular cross section, with snap locks that join the two sides together.  For trusses, all of the truss elements are rolled up together, so the whole truss snaps out and locks.  It's a really interesting tech; it's been worked on for decades, but it finally seems to be maturing.

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There is a third option I'm calling DEployable Spin Gravity Array (DeSGA - small animation attached), which I would put on space craft intended to support humans working out at asteroids.

Interesting.  Seems more complicated than rollable trusses, and seems to fundamentally require large fairings.. but otherwise I see no reason why that wouldn't work.  How do people move between segments?  Is there an airlock at each end that joins up when the structure folds out to a ring?

But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.


It's the "stamping / sintering" around a mould (aka having to relocate it, having the sinterer not just be some enclosed hollow, etc)  that raises big question marks in my mind.  But, who knows?  :)  Work with sintering asteroid material for return to Earth could certainly advance the TRL enough to make it worth a shot.  The latter has always seemed the most obvious way to make asteroid mining with Earth return economic: sinter to a hollow aeroshell shape (simple enclosed mould) and eject with a quench gun (it's iron-bearing, after all) onto an earth-crossing trajectory, either for aerocapture to orbit, or to impact within a particular target ellipse.  Aka, it's its own ablator and entry body.  But to do that you'd have to be able to justify the easily-multi-billion-dollar-per-component cost of developing A) mining infrastructure, B) sintering infrastructure, C) power infrastructure, and D) a quench gun with the capability to impart several km/s dV.  If you've gotten that far, I guess the next stage of having a mobile sinterer and non-self-contained mould might not be so far fetched  ;)
« Last Edit: 03/13/2017 05:09 PM by Rei »

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