Author Topic: Artificial Gravity - Why Weight?  (Read 55892 times)

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.

Offline Robotbeat

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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.

Offline 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?

Offline 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
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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.
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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.

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