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  #21  
Old August 10th 18, 07:52 PM posted to sci.space.policy
Greg \(Strider\) Moore
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"JF Mezei" wrote in message ...

On 2018-08-09 16:52, Fred J. McCall wrote:

It's all about time scales. Can you add enough gas fast enough and
will it lose it slowly enough to be worthwhile.



You don't build and then board a leaky lifeboat unless you are damned
sure another boat will come in before it sinks.


You do if there's no other lifeboat at all.
But that's not even the point. I'll let you in on a hint. Pretty much all
boats leak. It's a matter of rate.

If the boat takes on 1 liter/hour and I can pump out 10 liter/hour, I'm not
worried.
If the boat takes on 1 liter/hour and it takes 1,000,000 liters to sink the
boat, I'm not worried.



Why spend the money/effort to add atmpsphere to Mars knowing that it
will be lost and you'll either have to continuously add to it, or
eventually leave Mars to get onto another planet?


Because those times are measured in centuries and quite manageable.

Much simpler to build a domed city then to terraform Mars.


Upfront sure. But then... you have to maintain your dome. And here's the
kicker, I can guarantee your dome WILL leak.
So why build a dome if you simply know it will leak? (using your logic).



And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?


You know, there's a thriving city here in the US that's a mile up... and has
an average psi of 12psi.
And that's not even all that extreme for human limits.



If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?


You know, last time I was in Denver, I was wearing shorts and a t-shirt. (of
course the next day I nearly missed my flight due to the snowstorm.)


--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net
IT Disaster Response -
https://www.amazon.com/Disaster-Resp...dp/1484221834/

  #22  
Old August 10th 18, 11:08 PM posted to sci.space.policy
Fred J. McCall[_3_]
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JF Mezei wrote on Fri, 10 Aug 2018
13:20:08 -0400:

On 2018-08-09 16:52, Fred J. McCall wrote:

It's all about time scales. Can you add enough gas fast enough and
will it lose it slowly enough to be worthwhile.


You don't build and then board a leaky lifeboat unless you are damned
sure another boat will come in before it sinks.


Sorry, but that makes no sense.


Why spend the money/effort to add atmpsphere to Mars knowing that it
will be lost and you'll either have to continuously add to it, or
eventually leave Mars to get onto another planet?


Because if you can add enough gas in a few generations and it takes
100,000 years to bleed off, that's a pretty good deal.


Much simpler to build a domed city then to terraform Mars.


Well, no, because then you just get some little domes instead of an
entire planet.


And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?

If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?


My God, do you ever bother to research anything even a little bit
before you start nit picking? Here, read this for a start to
educating yourself:

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


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson
  #23  
Old August 11th 18, 12:33 AM posted to sci.space.policy
Alain Fournier[_3_]
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On Aug/10/2018 at 2:52 PM, Greg (Strider) Moore wrote :
"JF Mezei"Â* wrote in message ...


And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?


You know, there's a thriving city here in the US that's a mile up... and
has an average psi of 12psi.
And that's not even all that extreme for human limits.



If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?


You know, last time I was in Denver, I was wearing shorts and a t-shirt.
(of course the next day I nearly missed my flight due to the snowstorm.)


What you put in parentheses is important. Snow storms are much rarer in
Washington D.C. than in Denver, though they are approximately at the
same latitude. The main reason for that is because you have less air
over your head in Denver, altitude of about 1600m, than in D.C.,
altitude of about 0m. More snow, isn't really the problem here, it is
the cold. If you terraform Mars with less atmospheric pressure than on
Earth you will likely have colder temperatures.

That isn't a show stopper. But it is something that should be taken into
consideration when planning what kind of atmosphere you plan to have on
a terraformed Mars.


Alain Fournier
  #24  
Old August 11th 18, 02:14 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Alain Fournier wrote on Fri, 10 Aug 2018
19:33:15 -0400:

On Aug/10/2018 at 2:52 PM, Greg (Strider) Moore wrote :
"JF Mezei"* wrote in message ...


And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?


You know, there's a thriving city here in the US that's a mile up... and
has an average psi of 12psi.
And that's not even all that extreme for human limits.



If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?


You know, last time I was in Denver, I was wearing shorts and a t-shirt.
(of course the next day I nearly missed my flight due to the snowstorm.)


What you put in parentheses is important. Snow storms are much rarer in
Washington D.C. than in Denver, though they are approximately at the
same latitude. The main reason for that is because you have less air
over your head in Denver, altitude of about 1600m, than in D.C.,
altitude of about 0m. More snow, isn't really the problem here, it is
the cold. If you terraform Mars with less atmospheric pressure than on
Earth you will likely have colder temperatures.


Actually, you get more snow in Denver because of the Rockies. Denver
gets pretty warm in summer, so it's not just thinner air equating to
colder temps.


--
"Rule Number One for Slayers - Don't die."
-- Buffy, the Vampire Slayer
  #25  
Old August 11th 18, 12:12 PM posted to sci.space.policy
Jeff Findley[_6_]
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In article ,
says...

On 2018-08-09 16:52, Fred J. McCall wrote:

It's all about time scales. Can you add enough gas fast enough and
will it lose it slowly enough to be worthwhile.



You don't build and then board a leaky lifeboat unless you are damned
sure another boat will come in before it sinks.


All inflatable life boats have a leak rate that's non-zero. The point
is that the leak rate is far less than what would impact the use of the
life boat. Since a life boat will be used for days (or perhaps weeks at
most) as long as the leak rate is low enough, the boat is never in any
danger of sinking.

Also, life rafts quite often come equipped with manual air pumps to make
up for any losses caused by leaks caused by debris or other incidents
which happen after deployment. This is akin to adding a bit more
atmosphere when necessary.

Why spend the money/effort to add atmpsphere to Mars knowing that it
will be lost and you'll either have to continuously add to it, or
eventually leave Mars to get onto another planet?


Nothing humans build lasts on the timescales we're talking about here.
The oldest human artifacts are on the order of thousands of years old.
Mars lost its atmosphere over millions and millions of years.

Much simpler to build a domed city then to terraform Mars.


No one is saying otherwise, but eventually domes just aren't good enough
to contain your expanding population and another long term solution is
needed.

And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?


Look at Venus. This isn't a problem. One earth standard atmosphere of
pressure is actually very little.

If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?


You can. You just have to drop enough Kuiper belt objects on it. This
is an engineering problem, not a physics problem. Nothing in physics
prevents this from happening.

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.
  #26  
Old August 11th 18, 01:57 PM posted to sci.space.policy
Alain Fournier[_3_]
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On Aug/10/2018 at 9:14 PM, Fred J. McCall wrote :
Alain Fournier wrote on Fri, 10 Aug 2018
19:33:15 -0400:

On Aug/10/2018 at 2:52 PM, Greg (Strider) Moore wrote :
"JF Mezei"Â* wrote in message ...


And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?

You know, there's a thriving city here in the US that's a mile up... and
has an average psi of 12psi.
And that's not even all that extreme for human limits.



If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?

You know, last time I was in Denver, I was wearing shorts and a t-shirt.
(of course the next day I nearly missed my flight due to the snowstorm.)


What you put in parentheses is important. Snow storms are much rarer in
Washington D.C. than in Denver, though they are approximately at the
same latitude. The main reason for that is because you have less air
over your head in Denver, altitude of about 1600m, than in D.C.,
altitude of about 0m. More snow, isn't really the problem here, it is
the cold. If you terraform Mars with less atmospheric pressure than on
Earth you will likely have colder temperatures.


Actually, you get more snow in Denver because of the Rockies. Denver
gets pretty warm in summer, so it's not just thinner air equating to
colder temps.


Correct. There are many things that affect temperatures. Nonetheless,
locations at higher altitudes do tend to have colder temperatures than
locations at lower altitudes. And that is mostly because of thinner air.
And Mars being further away from the sun than Earth, one would prefer
having a "thicker blanket" to help control temperatures.


Alain Fournier
  #27  
Old August 11th 18, 07:35 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Alain Fournier wrote on Sat, 11 Aug 2018
08:57:03 -0400:

On Aug/10/2018 at 9:14 PM, Fred J. McCall wrote :
Alain Fournier wrote on Fri, 10 Aug 2018
19:33:15 -0400:

On Aug/10/2018 at 2:52 PM, Greg (Strider) Moore wrote :
"JF Mezei"* wrote in message ...

And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?

You know, there's a thriving city here in the US that's a mile up... and
has an average psi of 12psi.
And that's not even all that extreme for human limits.



If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?

You know, last time I was in Denver, I was wearing shorts and a t-shirt.
(of course the next day I nearly missed my flight due to the snowstorm.)


What you put in parentheses is important. Snow storms are much rarer in
Washington D.C. than in Denver, though they are approximately at the
same latitude. The main reason for that is because you have less air
over your head in Denver, altitude of about 1600m, than in D.C.,
altitude of about 0m. More snow, isn't really the problem here, it is
the cold. If you terraform Mars with less atmospheric pressure than on
Earth you will likely have colder temperatures.


Actually, you get more snow in Denver because of the Rockies. Denver
gets pretty warm in summer, so it's not just thinner air equating to
colder temps.


Correct. There are many things that affect temperatures. Nonetheless,
locations at higher altitudes do tend to have colder temperatures than
locations at lower altitudes. And that is mostly because of thinner air.
And Mars being further away from the sun than Earth, one would prefer
having a "thicker blanket" to help control temperatures.


Some truth there, but the reason you really get that is that it's
easier for ground heat to radiate away at night because there is less
air and it's usually clear. That means there's less heat buildup at
ground level. So Denver gets 100+ temperatures during the day
(because the clear air allows more ground heating) but relatively
cooler temperatures at night (because ground heat can radiate away
more easily through the clear air). You can get the same effect as a
thick air blanket by just having an overcast atmosphere to reflect
heat back toward the ground. Snow off the mountains actually tends to
moderate temperatures in Denver in winter, since that will reflect
heat back toward the ground. Let the air get cold enough to clear a
bit and the snow stops.


--
"Rule Number One for Slayers - Don't die."
-- Buffy, the Vampire Slayer
  #28  
Old August 12th 18, 08:25 AM posted to sci.space.policy
Niels Jørgen Kruse[_2_]
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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.

--
Mvh./Regards, Niels Jørgen Kruse, Vanløse, Denmark
  #29  
Old August 12th 18, 12:33 PM posted to sci.space.policy
Alain Fournier[_3_]
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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.


Alain Fournier
  #30  
Old August 12th 18, 12:40 PM posted to sci.space.policy
Alain Fournier[_3_]
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On Aug/11/2018 at 10:12 PM, JF Mezei wrote :
"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 panels usually make energy from visible light. CO2 isn't very
opaque for visible light. Even one full atmosphere of pressure from CO2
wouldn't reduce solar panels output much. So I don't think this is much
of a problem.


Alain Fournier
 




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