Discussion on sci.space.science

JF Mezei wrote on Thu, 16 Aug 2018
15:56:48 -0400:

On 2018-08-16 15:46, Fred J. McCall wrote:

You appear to have forgotten the whole "increased atmospheric
pressure" thing, Mayfly.

So you are claiming it should be possible to get 14.7 PSI atmosphere on
Martian ground ?


Of course it's 'possible'. It's just (large-scale) engineering.


or are you going for 5 PSI with pure O2 as atmosphere for humans in
suits and insiude habitable volume ?


This is a horrible idea for all sorts of reasons. And once again
you're forgetting the whole idea that people will be OUTSIDE for some
appreciable amount of time.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

"Scott M. Kozel" wrote on Thu, 16 Aug 2018
14:17:43 -0700 (PDT):

On Thursday, August 16, 2018 at 4:03:53 PM UTC-4, Fred J. McCall wrote:
"Scott M. Kozel" wrote on Thu, 16 Aug 2018

The Tunguska object is a mystery. As you suggested a comet-like body
melts and outgasses as it comes closer to the Sun. Usually well underway
within 2 astronomical units from the Sun (Mars being within that). So
the questions outstanding are how did a comet get that close to the Earth
without being sighted, how did it stay intact enough to cause a massive
explosion in the atmosphere.

Visibility varies based on comet composition. It got so deep because
it didn't soak up enough heat to reach critical temperature until it
was so deep.

One theory is that it was a rocky object that came into the atmosphere
at a nearly flat angle and at extremely high velocity (70,000 mph or more)
and traveled several miles in the atmosphere and completely disintegrated
in a multi-megaton explosion to where no significant meteorite remained.
That scenario probably passes the physics test.

Like I said it is still a mystery among scientists that have studied it.
Several good theories but no conclusion.

"No one knows for sure" doesn't equate to "my niche hypothesis is
correct".

No, but that is one of the theories.


So is that it was a big natural gas explosion and nothing from space
was involved at all. That doesn't make it likely and it doesn't
explain a lot of things, like the observed noctiluminescence. And the
word you want is 'hypothesis', not 'theory'.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

On Friday, August 17, 2018 at 12:49:19 AM UTC-4, Fred J. McCall wrote:
"Scott M. Kozel" wrote on Thu, 16 Aug 2018
On Thursday, August 16, 2018 at 4:03:53 PM UTC-4, Fred J. McCall wrote:

"No one knows for sure" doesn't equate to "my niche hypothesis is
correct".

No, but that is one of the theories.

So is that it was a big natural gas explosion and nothing from space
was involved at all. That doesn't make it likely and it doesn't
explain a lot of things, like the observed noctiluminescence. And the
word you want is 'hypothesis', not 'theory'.

I would be interested in knowing how NASA determined such a detailed
"generally agreed upon theory". Size, velocity, mass, temperature,
explosion height, explosion size.

Actually the last 2 could be derived from the treefall patterns.

In article ,
says...

On 2018-08-15 20:16, Jeff Findley wrote:

Nuclear fission or nuclear fusion powered rocket engine using some of
the volatiles from the Kuiper belt object as reaction mass. You'd
almost surely combine that with some gravity assist flybys and the like.
But, as you said before, this would be a very long process.


Woopty do.

When you consider the low gravity of Mars, and that to increase PSI are
ground level, you will need to add a HUGE amount of atmpsophere most of
which will be so high as to be useless, it becomes far more efficient
to just build pressurized shelters (which you need to build anyways) and
just add the atmosphere needed to pressurize the shelters and energy to
heat them.

In the near term, shelters would be the way to go. Again, terraforming
will take thousands of years.

And since such a colony would have limited O2 supply, it is more likely
that the CO2 would get recycled into Carbon and O2 as part of ECLSS of
the habitable volumes. aka: they aren't going to dump CO2 into outside
atmosphere.

Surely. But, in the short term, just as surely O2 will also be produced
from CO2 and H2O found locally.

QUESTION:

In theoretical terraforming scenario where lots of CO2 is added, with
so much of atmpsphere very thin and very high, would the CO2 reflect the
heat back to ground level in a significant way? Or would it trap heat at
such a high altitude that ground level would see little change ?

This is a detail I am not at all familiar with. The more general point
is that CO2, and other added gases, will add both pressure and increase
the atmospheric temperature of Mars. In the "short term" (which is
still thousands of years), this would lead to an atmosphere where you
could venture outside without a bulky, heavy, pressure suit. A
breathing mask and eye protection would suffice.

In the long term, plants would convert the CO2, ammonia, and other stuff
humans don't like to breathe much of into O2 and biomass (that's where
the carbon goes). This eventually (many thousands of years more) leads
to an atmosphere where you can step outside without any protection just
like on earth.

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.

In article ,
says...

On Thursday, August 16, 2018 at 12:08:28 AM UTC-4, JF Mezei wrote:

QUESTION:

In theoretical terraforming scenario where lots of CO2 is added, with
so much of atmpsphere very thin and very high, would the CO2 reflect the
heat back to ground level in a significant way? Or would it trap heat at
such a high altitude that ground level would see little change ?

One of the articles that I found, said that if the terraforming process
went awry, that fixing the issues might make the whole process far more
difficult and time consuming than it would be from starting with the
virgin planet.

True. There is always a chance that something might go awry. But there
is also the chance something will go awry with earth's climate as well
(natural cycles, man made problems, and etc.). There are no guarantees
in this universe.

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.

In article ,
says...

On 2018-08-16 15:46, Fred J. McCall wrote:

You appear to have forgotten the whole "increased atmospheric
pressure" thing, Mayfly.

So you are claiming it should be possible to get 14.7 PSI atmosphere on
Martian ground ?

You don't need 14.7 PSI! What's the pressure in Denver Colorado? Next,
what is the pressure at the highest habitable points in South America?
Google it man!

or are you going for 5 PSI with pure O2 as atmosphere for humans in
suits and insiude habitable volume ?

There is a whole wide range of atmospheric mixes between pure O2 and
earth's 80% N2 20% O2. Humans can breathe pretty much any mix of O2 and
N2 as long as the partial pressure of O2 is high enough.

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.

On Saturday, August 18, 2018 at 8:28:40 AM UTC-4, Jeff Findley wrote:
In article ,
says...

One of the articles that I found, said that if the terraforming process
went awry, that fixing the issues might make the whole process far more
difficult and time consuming than it would be from starting with the
virgin planet.

True. There is always a chance that something might go awry. But there
is also the chance something will go awry with earth's climate as well
(natural cycles, man made problems, and etc.). There are no guarantees
in this universe.

True. The Sun could go nova and expand its envelope to beyond the orbit
of Mars.

In article ,
says...

On Thursday, August 16, 2018 at 12:08:37 AM UTC-4, Fred J. McCall wrote:
"Scott M. Kozel" wrote on Wed, 15 Aug 2018

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


It will take sometime between a week and forever.

A week is a bit of a stretch.

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


The same way you move anything else in space.

So it is an engineering problem. Just like if someone proposed
increasing the diameter of the orbit of Venus by 10 million miles as
part of its terraforming process.

An object 1/4 mile in diameter would probably be in the billions
of tons. Where will the energy be found ...

Well, the object is essentially MADE of fuel, so you just send out a
tug engine and burn part of the object to get it to Mars. Or you
build a mass driver tug and throw part of the object to move the rest
of it. Or ...

You need an oxidizer in addition to the fuel (methane, ethane, other
hydrocarbons).

No you don't. You need a very hot heat source. That can be fission
(today) or fusion (just 5 or so years away, if you believe the fusion
proponents).

Why do you care if it makes a crater and what makes you think it
would? These things are mostly volatiles. They're going to melt on
the way down. Worst case you get something like Tunguska, which made
a big blast but left no crater at all that we can find.

Depends on the velocity and angle of entry. Presumably the Tunguska
object entered the atmosphere and a very high velocity but a very
shallow angle. A steep angle might have had the object hit the Earth
mostly intact.

These objects will be under power. Hopefully we'll be able to hit Mars
at the desired trajectory.

A cubic mile of ices coming in at 20,000 mph and an angle of 70+
degrees to the ground?

I'm sure some of it will go "boom" when it hits. So what? Mars already
has craters. What's a few more? Just don't hit anywhere near your
"HAB" domes.

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.

In article ,
says...

On Saturday, August 18, 2018 at 8:28:40 AM UTC-4, Jeff Findley wrote:
In article ,
says...

One of the articles that I found, said that if the terraforming process
went awry, that fixing the issues might make the whole process far more
difficult and time consuming than it would be from starting with the
virgin planet.

True. There is always a chance that something might go awry. But there
is also the chance something will go awry with earth's climate as well
(natural cycles, man made problems, and etc.). There are no guarantees
in this universe.

True. The Sun could go nova and expand its envelope to beyond the orbit
of Mars.

I'm sure it will, eventually. If humans want to survive on that sort of
timescale, we need to GTFO of the solar system. On that timescale,
terraforming Mars is "practice" for terraforming exosolar planetary
bodies.

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.

Le Aug/18/2018 Ã* 8:26 AM, Jeff Findley a écritÂ*:
In article ,
says...

On 2018-08-15 20:16, Jeff Findley wrote:

Nuclear fission or nuclear fusion powered rocket engine using some of
the volatiles from the Kuiper belt object as reaction mass. You'd
almost surely combine that with some gravity assist flybys and the like.
But, as you said before, this would be a very long process.


Woopty do.

When you consider the low gravity of Mars, and that to increase PSI are
ground level, you will need to add a HUGE amount of atmpsophere most of
which will be so high as to be useless, it becomes far more efficient
to just build pressurized shelters (which you need to build anyways) and
just add the atmosphere needed to pressurize the shelters and energy to
heat them.

In the near term, shelters would be the way to go. Again, terraforming
will take thousands of years.

And since such a colony would have limited O2 supply, it is more likely
that the CO2 would get recycled into Carbon and O2 as part of ECLSS of
the habitable volumes. aka: they aren't going to dump CO2 into outside
atmosphere.

Surely. But, in the short term, just as surely O2 will also be produced
from CO2 and H2O found locally.

QUESTION:

In theoretical terraforming scenario where lots of CO2 is added, with
so much of atmpsphere very thin and very high, would the CO2 reflect the
heat back to ground level in a significant way? Or would it trap heat at
such a high altitude that ground level would see little change ?

This is a detail I am not at all familiar with. The more general point
is that CO2, and other added gases, will add both pressure and increase
the atmospheric temperature of Mars. In the "short term" (which is
still thousands of years), this would lead to an atmosphere where you
could venture outside without a bulky, heavy, pressure suit. A
breathing mask and eye protection would suffice.

CO2 is quite transparent to visible light. Sun light will go right
through and hit the ground where it will be transformed into heat. CO2
is much less transparent to infra-red radiation. So heat at ground level
will have a somewhat hard time escaping to space. It will do so by
heating the atmosphere a little higher which will then heat the
atmosphere again a little higher etc.

In the long term, plants would convert the CO2, ammonia, and other stuff
humans don't like to breathe much of into O2 and biomass (that's where
the carbon goes). This eventually (many thousands of years more) leads
to an atmosphere where you can step outside without any protection just
like on earth.

Just a little more detail about humans not liking to breathe CO2. Of
course we have some CO2 in our atmosphere, it isn't toxic for most
people. But as about anything else the dose does matter. As you increase
CO2 concentrations you increase the incidence of panic attacks. If I
remember correctly at 20% CO2 100% of subjects will have a panic attack
within 10 minutes. (DO NOT TRY THIS ON YOUR OWN, THIS SHOULD ONLY BE
DONE WITH QUALIFIED PERSONNEL SUPERVISING, THE OUTCOME CAN BE DEATH
WITHOUT YOU BEING ABLE TO DO ANYTHING ABOUT IT AFTER THE VERY FIRST
SIGNS. I REPEAT DO NOT TRY THIS.) Some people have panic attacks in our
regular atmosphere, the incidence just goes up as you raise the CO2
concentration. So I wouldn't recommend going out breathing the
atmosphere in a terraformed Mars until CO2 levels are quite low even if
the O2 levels are acceptable.


Alain Fournier