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  #31  
Old August 12th 18, 03:09 PM posted to sci.space.policy
Niels Jørgen Kruse[_2_]
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Alain Fournier wrote:

On Aug/12/2018 at 3:25 AM, Niels Jørgen Kruse wrote :
Alain Fournier wrote:

And Mars being further away from the sun than Earth, one would prefer
having a "thicker blanket" to help control temperatures.


The lower gravity means the blanket is thicker than pressure would
suggest.


Thicker in terms of km. But I don't think that makes it much thicker in
terms of heat retention. I could be wrong but I think that the greater
scale height of Mars' atmosphere (meaning thicker atmosphere in terms of
km) will make convective heat loss slower but have no effect on
radiative heat loss. I also think that most of the heat loss would be
from thermal radiation not from convection, especially so if the
atmosphere is light (meaning low pressure at ground level).

The above is mostly speculation on my part. If anyone has knowledge
above speculation, I would really like you to share. Even if you have
only speculation that would be cool too, just not as much.


Surface gravity on Mars is lower by a factor of 2.64 than that of Earth.
That means you need 2.64 times the mass of atmosphere to create the same
air pressure.

--
Mvh./Regards, Niels Jørgen Kruse, Vanløse, Denmark
  #32  
Old August 12th 18, 03:23 PM posted to sci.space.policy
Alain Fournier[_3_]
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On Aug/12/2018 at 10:09 AM, Niels Jørgen Kruse wrote :
Alain Fournier wrote:

On Aug/12/2018 at 3:25 AM, Niels Jørgen Kruse wrote :
Alain Fournier wrote:

And Mars being further away from the sun than Earth, one would prefer
having a "thicker blanket" to help control temperatures.

The lower gravity means the blanket is thicker than pressure would
suggest.


Thicker in terms of km. But I don't think that makes it much thicker in
terms of heat retention. I could be wrong but I think that the greater
scale height of Mars' atmosphere (meaning thicker atmosphere in terms of
km) will make convective heat loss slower but have no effect on
radiative heat loss. I also think that most of the heat loss would be
from thermal radiation not from convection, especially so if the
atmosphere is light (meaning low pressure at ground level).

The above is mostly speculation on my part. If anyone has knowledge
above speculation, I would really like you to share. Even if you have
only speculation that would be cool too, just not as much.


Surface gravity on Mars is lower by a factor of 2.64 than that of Earth.
That means you need 2.64 times the mass of atmosphere to create the same
air pressure.


Right. I should have thought of that.


Alain Fournier
  #33  
Old August 12th 18, 11:06 PM posted to sci.space.policy
Fred J. McCall[_3_]
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JF Mezei wrote on Sat, 11 Aug 2018
22:12:03 -0400:

"Thickening" the atmosphere with CO2 or whethever to retain heat would
have a negative effect: solar panels would get less of the sun's energy.

The loss of solar efficiency would be worth it if you achieved a
shirt-sleeve atmpsphere on Mars. But if you still need pressurized
habitats, then making the oustide less cold at the expense of reducing
solar power efficiency is a trade off that designers of the habvitats
will have to debate.


Solar is marginal out at Mars anyway. Plan on nuclear.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
  #34  
Old August 14th 18, 05:25 AM posted to sci.space.policy
David Spain
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On 8/1/2018 7:43 PM, Alain Fournier wrote:

Jeff Findley and I have been having on sci.space.science a discussion
about water on Mars and terraforming Mars, that I appreciate very much.
Nobody else is contributing to the discussion, possibly because some of
you have given up on sci.space.science.

So if you haven't checked on sci.space.science for a while, I encourage
you to go check it out. And if you want to contribute to the discussion,
that would be great.


Alain Fournier


I don't want to sound snarky, but given the fact that NASA won't even
consider strong LEO gravity lab proposals pitched by Rand Simberg and
the SSI, for eventual ISS commercialization strategies, just so we can
find out if humans can live on Mars for more than a few years at a time
before succumbing to strange physiological conditions heretofore unheard
of, I find this whole issue, well, just not worth a discussion. Sorry
and a bit ****ed. Not a good time for pie in the sky with me.

Dave

  #35  
Old August 14th 18, 05:29 AM posted to sci.space.policy
David Spain
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On 8/14/2018 12:25 AM, David Spain wrote:
Not a good time for pie in the sky with me.

Dave

It doesn't help that on every clear night this month I can look up in
the east and see Mars, shining right back at me. It seems more remote
than ever. I hope Musk is successful. I hope it's not a graviational
death trap. Somebody should tell NASA it'd be better to know instead of
relying on hope and faith.

Dave



  #36  
Old August 15th 18, 12:16 PM posted to sci.space.policy
Jeff Findley[_6_]
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In article , says...

On 8/1/2018 7:43 PM, Alain Fournier wrote:

Jeff Findley and I have been having on sci.space.science a discussion
about water on Mars and terraforming Mars, that I appreciate very much.
Nobody else is contributing to the discussion, possibly because some of
you have given up on sci.space.science.

So if you haven't checked on sci.space.science for a while, I encourage
you to go check it out. And if you want to contribute to the discussion,
that would be great.


Alain Fournier


I don't want to sound snarky, but given the fact that NASA won't even
consider strong LEO gravity lab proposals pitched by Rand Simberg and
the SSI, for eventual ISS commercialization strategies, just so we can
find out if humans can live on Mars for more than a few years at a time
before succumbing to strange physiological conditions heretofore unheard
of, I find this whole issue, well, just not worth a discussion. Sorry
and a bit ****ed. Not a good time for pie in the sky with me.


I agree with you and I've been there.

Right now my opinion is that NASA has become a boat anchor when it comes
to crewed space exploration. They spend orders of magnitude more time
and effort "naval gazing" while thinking about theoretical crew safety
than they do actually flying crew. We're very close to flying
commercial crew but the certifications are what's holding things up.
Every little thing they object to causes some sort of redesign and
"fix" which draws out the schedule.

But, at the same time, terraforming will take hundreds or thousands of
years. Not something we're ever going to watch live on YouTube like a
rocket launch. All of us here will no doubt be long gone when the first
Kuiper belt object is dropped on Mars.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #37  
Old August 15th 18, 12:18 PM posted to sci.space.policy
Jeff Findley[_6_]
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In article , says...

On 8/14/2018 12:25 AM, David Spain wrote:
Not a good time for pie in the sky with me.

Dave

It doesn't help that on every clear night this month I can look up in
the east and see Mars, shining right back at me. It seems more remote
than ever. I hope Musk is successful. I hope it's not a graviational
death trap. Somebody should tell NASA it'd be better to know instead of
relying on hope and faith.


We could test this by connecting a tether between a BFS and a BFS tanker
and spin them in LEO for a year or so. This would test out long term
life support, power, propulsion, and other systems while also serving as
a Mars gravity test.

Or we just go and see how people actually react to Mars gravity. My
guess is that Musk would choose this option.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #38  
Old August 15th 18, 09:05 PM posted to sci.space.policy
Scott M. Kozel[_2_]
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On Wednesday, August 15, 2018 at 7:16:13 AM UTC-4, Jeff Findley wrote:

But, at the same time, terraforming will take hundreds or thousands of
years. Not something we're ever going to watch live on YouTube like a
rocket launch.


One website article I found said more like 100,000 years.

All of us here will no doubt be long gone when the first
Kuiper belt object is dropped on Mars.


Just how do you go about "dropping a Kuiper belt object on Mars?"

An object 1/4 mile in diameter would probably be in the billions
of tons. Where will the energy be found to transfer that to a
Mars solar orbit perigee, then accelerate it up to Mars solar
orbit speed, then decelerate it to Mars surface at a speed that
won't create a massive crater on the scale of the one out in
Arizona?

How many hundreds or thousands of such objects would be needed?
  #39  
Old August 16th 18, 12:38 AM posted to sci.space.policy
Alain Fournier[_3_]
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Posts: 548
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On Aug/15/2018 at 4:05 PM, Scott M. Kozel wrote :
On Wednesday, August 15, 2018 at 7:16:13 AM UTC-4, Jeff Findley wrote:

But, at the same time, terraforming will take hundreds or thousands of
years. Not something we're ever going to watch live on YouTube like a
rocket launch.


One website article I found said more like 100,000 years.

All of us here will no doubt be long gone when the first
Kuiper belt object is dropped on Mars.


Just how do you go about "dropping a Kuiper belt object on Mars?"

An object 1/4 mile in diameter would probably be in the billions
of tons. Where will the energy be found to transfer that to a
Mars solar orbit perigee, then accelerate it up to Mars solar
orbit speed, then decelerate it to Mars surface at a speed that
won't create a massive crater on the scale of the one out in
Arizona?


Why not have another crater on Mars? And why not slam the objects at
high speed into Mars. When the thing hits the surface, it will
decelerate. Yes you will lose a little mass that will escape because of
the energy released on impact. You just bring in more objects to compensate.

How many hundreds or thousands of such objects would be needed?


Many thousands.


Alain Fournier
  #40  
Old August 16th 18, 01:11 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
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Jeff Findley wrote on Wed, 15 Aug 2018
07:18:37 -0400:


Or we just go and see how people actually react to Mars gravity. My
guess is that Musk would choose this option.


Musk will almost certainly 'just go', but he'll 'just go' in a way
that lets him find his way before any disasters occur and given BFR
he'll always have a way to bring a small settlement home.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
 




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