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  #11  
Old March 5th 21, 11:15 PM posted to sci.space.policy
David Spain
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Default Mars colonization

On 3/4/2021 2:30 AM, Frank Scrooby wrote:

If and when colonists want to move to soil based agriculture there is a simple-ish solution to the perchlorate problem: H2O. Enough warm water will dissolve and or reactive with the perchlorates, allowing for simple mechanical methods like filtering or evaporation to remove and isolate the offending compounds. If water is not readily available in sufficient quantities good ol' bakin' and shakin' will do to. Setup a solar thermal concentrator that can heat your reaction chamber up to a few hundred odd degrees Kelvin (1000 would be a nice round number) with an extremely high atmospheric pressure (like a few Earth atmosphere equivalents). Expose soil, give it some time to get hot and shake it around to loosen up things. Then reduce the atmosphere pressure via release valve. Between the photons and the rush for lighter elements' atoms to fill the 'vacuum'. What is left behind will be dead and dry, but at least it won't be toxic anymore. And you now have a pressure vessel somewhere filled with the baked off volatiles. Any long term colony is going have uses for those.

For the curious: NASA cooperated with another Organisation on a study called MAGIC (which stands for Mars AGricultural something something). It proposes an automated hydroponic greenhouse as a supplement to crew meals.

Anyway.

Regards
Frank



Came to this posting late. Threaded out of order in my news client. This
makes sense, but in the short term I suspect hydroponics will be the
first setup to grow food, since that is a much simpler setup and
conserves precious water until adequate Martian sources can be secured.

Soil isn't needed to start out.

Dave

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  #12  
Old March 8th 21, 06:40 PM posted to sci.space.policy
jacob navia
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Default Mars colonization

Le 01/03/2021 Ã* 01:27, Alain Fournier a écritÂ*:
SpaceX plans on building Starship to transport Mars colonist and
equipment for a Mars colony. But they mostly expect other companies and
organizations to handle the actual establishment of a base on Mars :
habitats, greenhouses... Starship seems to be advancing well, but I
haven't heard much about others working on the necessities for living on
Mars. Have any of you heard about others having such plans?


Alain Fournier


All this "To mars" stuff is just vaporwware. Humans have no technology
to send any of hem to mars now, and (luckily) they will not have it in
the next 20 years.

  #14  
Old March 8th 21, 10:14 PM posted to sci.space.policy
Alain Fournier[_3_]
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On Mar/8/2021 at 14:19, Jeff Findley wrote :
In article , says...

Le 01/03/2021 à 01:27, Alain Fournier a écrit*:
SpaceX plans on building Starship to transport Mars colonist and
equipment for a Mars colony. But they mostly expect other companies and
organizations to handle the actual establishment of a base on Mars :
habitats, greenhouses... Starship seems to be advancing well, but I
haven't heard much about others working on the necessities for living on
Mars. Have any of you heard about others having such plans?


All this "To mars" stuff is just vaporwware. Humans have no technology
to send any of hem to mars now, and (luckily) they will not have it in
the next 20 years.


I personally think we'll see humans set foot on Mars in less than 20
years. Actual colonies on Mars will take a bit longer. ;-)


Depending on what is your definition of a colony, the first one could
very well be in less than 20 years. I personally think that in less than
20 years there will be some people living on Mars and considering Mars
as their home or some people living on Mars with no planed date for
their return to Earth. That is a rather weak definition of what is a
colony, and even so, it is not a sure thing that it will happen within
20 years, but I think it will happen.

For a stronger definition of a colony, such as a group living on Mars
and capable of growing and surviving indefinitely without receiving
supplies from Earth, yes I would say that will take more than 20 years.


Alain Fournier
  #15  
Old March 9th 21, 06:46 AM posted to sci.space.policy
Frank Scrooby[_2_]
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Default Mars colonization

Greetings all,
On Tuesday, March 9, 2021 at 12:14:43 AM UTC+2, Alain Fournier wrote:
much snipped

For a stronger definition of a colony, such as a group living on Mars
and capable of growing and surviving indefinitely without receiving
supplies from Earth, yes I would say that will take more than 20 years.


Even with the great strides made by SpaceX I'm still somewhat cynical of the 20-ish year deadline for Humans on Mars. Let's just put it down to me having been disappointed by lack of progress in the past (NASA and Washington, I'm talking about you, and Apollo and Skylab, and the X-33 and the whole damn Shuttle program).

I'm forgetting who did it but one of the historical colony leaders got where they were going, unloaded and then torched the ships (i'm not thinking of William I, it might be Cortez, or one of his contemporaries. Not necessarily smart, but it gives people a definite message: You are not going home the same way you came.

The equivalent on Mars would sending your Mars Habitat to Mars and instead of sending your Mars Ascent vehicle (or Mars Return Vehicle) sending another Mars Hab packed with supplies. No MAV/MRV no way home for another 18 months (it is 18 months). Better get that hydroponic greenhouse deployed, and find the best water containing regolith to mine.


Alain Fournier


Regards
Frank
  #16  
Old March 11th 21, 01:17 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default Mars colonization

In article ,
says...

On 2021-03-08 14:19, Jeff Findley wrote:

I personally think we'll see humans set foot on Mars in less than 20
years. Actual colonies on Mars will take a bit longer. ;-)



It's a catch 22 with current plans. For humans to set foot and not
return, a colony must be sent/built ahead.

For humans to set foot on mars for a camping trip and come back to
Earth, you need to have fuel production developped on mars ahead since
the campers are only there for a few days. Or have Starships send fuel
ahead of time. Either way, it is a whole lot of starships needed. And
the big issue is whether the window is large enough that you can send
everything ahead and wait until it has succesfully landed because
putting the crew past point of no return.


Due to orbital mechanics, every couple of years there is a "window" when
you can send spacecraft to Mars using a minimum amount of delta-V.

is there a possibility with the right alignment of planets to arrive at
Mars and "slingshot" back to Earth with very little fuel? aka: if you
find out that the needed fuel crashed on mars can you return to earth
with the fuel you would have used to land?


Good question. I'm sure the mission planners at NASA know this answer.
But, free return trajectories do exist for an earth-Mars-earth trip.
Cite:

https://en.wikipedia.org/wiki/Free-return_trajectory

The trick would be to change a trajectory which planned on ending with a
Mars landing to one that's a free return. That delta-V is left for the
reader to calculate. ;-)

Jeff
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  #17  
Old March 11th 21, 08:00 PM posted to sci.space.policy
Alain Fournier[_3_]
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Default Mars colonization

On Mar/11/2021 at 14:11, JF Mezei wrote :
On 2021-03-11 08:17, Jeff Findley wrote:

Due to orbital mechanics, every couple of years there is a "window" when
you can send spacecraft to Mars using a minimum amount of delta-V.


And this is the problem. Not much point in sending fuel ahead if by the
time you realise the fuel vehicle crashed, the crew are already on their
way to Mars. And using different windows means a very long time between
sending supplies and sending crew.


No one is planning a mission the way you describe it here. You don't
send fuel from Earth to Mars. You send some kind of apparatus that will
make fuel on Mars using in situ resources (some mission architecture
plan on sending hydrogen from Earth, but that is a small mass fraction
of the oxidiser and fuel). You do that at least one launch window before
sending humans. You don't send humans before your fuel factory on Mars
has succeeded.

Good question. I'm sure the mission planners at NASA know this answer.
But, free return trajectories do exist for an earth-Mars-earth trip.
Cite:

https://en.wikipedia.org/wiki/Free-return_trajectory


But that brings up ECLSS and food. If you have to slingshot and be
autonomous for another year to get back to Earth, that means that when
you leave earth, you leave with a hell of a lot of supplies and water.
And it also means you need some pretty fancy ECLSS to reclaim as much as
you can for water and oxygen. I have to wonder if SpaceX would take ISS
system designs or make their own from scratch. In later case, they are
a long way from having a Mars crewed mission.


A mission profile with a free return (nearly free return) trajectory
follows a path similar to a mission with a short stay on Mars. It
wouldn't take a year. More like 7 months. But it is more energy
expensive than a mission following a Hohmann transfer trajectory.

Almost worth considering putting people in induced coma for 6 months
with intravenous feeds to keep them alive followed by strong exercise
regimen to bring them back to shape.


That would be a whole new ballgame.

Another consideration: you might need 2 starships to return from Mars.
You send one from Earth to Mars solely with supplies needed for the
return journey. Lands on Mars. Once the crewed vehicle comes in, they
need to fuel both ships which take off and meet in space so the
food/water can be transfered to the crewed vehicle.


Coming from Earth, would landing and then taking off back to Earth end
up requiring less food than entering Mars orbit and when the crewed
vehicle takes off from Mars, it forst goes to orbit to meet with supply
ship and then heads to Earth? (thsi woudld also allow refueling
assuming both the tanker and the supply ship are in same orbit).


A Starship should be able to take-off from Mars and go to Earth without
in orbit resupply or refuel.


Alain Fournier
  #18  
Old March 11th 21, 08:07 PM posted to sci.space.policy
Alain Fournier[_3_]
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Default Mars colonization

On Mar/11/2021 at 14:32, JF Mezei wrote :
Another question:

Say you have decided your expedition will land at the equivalent of
Greenwich on mars (0" longitude, 51° latitude N).

How difficult is it to send multiple ships to that precise location so
they land within walking distance from each other?

Since Mars rotates, and since we're talking about a direct entry from
your transit velocity vector doesn't that require that you arrive at
atmosphere entry at a time where your destination (Greenwich) has
rotated to be directly in your path?

Is this accomplished with long term micro adjustements is speed for the
whole transit so you arrive at the right time, or is transit speed
pretty much precisely fixed due to orbital mechanics and you need to so
a more significan speed adjustment as you near Mars to let Mars rotate a
bit more or less so you have your target in your path ?

Just curious on how much flexibility a fleet of Starships bringling
supplies would have in terms of departing Earth and landing all at the
same spot.


Not a major issue. You make small adjustments when still far away from
Mars to get at the right place at the right time. Even if you just want
to reach Mars anywhere, you still do mid-course corrections because
aiming for Mars from Earth would require to much precision without
corrections.

The fact that you want to adjust for the exact location (and therefore
time of arrival) only slightly complicates the computations for your
mid-course corrections.


Alain Fournier
  #19  
Old March 11th 21, 10:18 PM posted to sci.space.policy
snidely
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Default Mars colonization

On Thursday, Alain Fournier exclaimed wildly:
On Mar/11/2021 at 14:32, JF Mezei wrote :
Another question:

Say you have decided your expedition will land at the equivalent of
Greenwich on mars (0" longitude, 51° latitude N).

How difficult is it to send multiple ships to that precise location so
they land within walking distance from each other?

Since Mars rotates, and since we're talking about a direct entry from
your transit velocity vector doesn't that require that you arrive at
atmosphere entry at a time where your destination (Greenwich) has
rotated to be directly in your path?

Is this accomplished with long term micro adjustements is speed for the
whole transit so you arrive at the right time, or is transit speed
pretty much precisely fixed due to orbital mechanics and you need to so
a more significan speed adjustment as you near Mars to let Mars rotate a
bit more or less so you have your target in your path ?

Just curious on how much flexibility a fleet of Starships bringling
supplies would have in terms of departing Earth and landing all at the
same spot.


Not a major issue. You make small adjustments when still far away from Mars
to get at the right place at the right time. Even if you just want to reach
Mars anywhere, you still do mid-course corrections because aiming for Mars
from Earth would require to much precision without corrections.

The fact that you want to adjust for the exact location (and therefore time
of arrival) only slightly complicates the computations for your mid-course
corrections.


And Perry was targeted pretty precisely, so the calculations are well
understood in practice as well as in theory.

/dps

--
"What do you think of my cart, Miss Morland? A neat one, is not it?
Well hung: curricle-hung in fact. Come sit by me and we'll test the
springs."
(Speculative fiction by H.Lacedaemonian.)
  #20  
Old March 12th 21, 03:36 PM posted to sci.space.policy
Alain Fournier[_3_]
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Default Mars colonization

On Mar/11/2021 at 15:00, Alain Fournier wrote :
On Mar/11/2021 at 14:11, JF Mezei wrote :


But that brings up ECLSS and food. If you have to slingshot and be
autonomous for another year to get back to Earth, that means that when
you leave earth, you leave with a hell of a lot of supplies and water.
And it also means you need some pretty fancy ECLSS to reclaim as much as
you can for water and oxygen.Â* I have to wonder if SpaceX would take ISS
system designs or make their own from scratch.Â* In later case, they are
a long way from having a Mars crewed mission.


A mission profile with a free return (nearly free return) trajectory
follows a path similar to a mission with a short stay on Mars. It
wouldn't take a year. More like 7 months. But it is more energy
expensive than a mission following a Hohmann transfer trajectory.


I thought I could entertain you a little more about orbital mechanics.

First, let's look at the base case. You want to go to Mars with the
least energy expensive trajectory. That is a Hohmann transfer orbit.
From Earth, you fire your rockets to increase your speed in the
direction of Earth's orbit around the sun. After that burn you are in an
orbit with its perihelion at Earth's orbital altitude and aphelion at
Mars' orbit. You just need to time your departure so you arrive at
aphelion when Mars happens to be at that same spot. That would be a
trajectory you would use for a probe, not for humans because the trip
from Earth to Mars takes 259 days (8.5 months). Your trip from Earth to
Mars is half of an elliptical orbit. When you want to go back to Earth,
you basically do the second half of that orbit, but once again you have
to time your departure so Earth is at the right spot when you arrive at
perihelion. So you have to stay about 9 months on Mars (or 9 months +
n*26 months).

If all you want to do on Mars is to plant the Canadian flag and come
back, the trip with the Hohmann transfer orbits takes you 26 months.
That is a little long for the five minutes it takes to actually plant
the Mexican flag. So you might want to spend a little more fuel and do
it faster.

To see how you could do the trip faster it helps to imagine what would
happen if an inhabitant of Mercury decided to go to Mars with a Hohmann
transfer orbit. The elliptical orbit with perihelion at Mercury's
altitude and aphelion at Mars' altitude has a semi-major axis of about 1
astronomical unit (more like 0.95, but to keep things simple let's
assume it is 1). That means that the orbital period of that orbit is
about 1 year. So if you are on such an elliptical orbit and you time it
so it passes near Earth, then you will pass near Earth each year. Of
course, if what you want to do is go from Earth to Mars, you don't need
to time it so it passes near Mercury, you just depart from Earth on this
trajectory at a time which is suitable so you arrive near Mars at
aphelion. Now we know that on an elliptical orbit you have higher speed
near periapsis and slower speed near apoapsis. So between Earth and
Mars, your angular rate will be less than the average rate over a
complete orbit of one revolution per year. So if you go to Mars and then
try to come immediately back with such a trajectory, when you will reach
Earth's orbit, Earth will be farther away and you won't like that.

What you want to do is the opposite of an Hohmann transfer orbit from
Mercury. Imagine this time that you leave Earth on a Hohmann transfer
orbit for Neptune. In the lower part of the orbit (e.g. between Earth
and Mars) your angular rate will be higher than that of Earth. So if you
go to Mars with such a trajectory, plant the Kazakh flag (for Make
Benefit Glorious Nation of Kazakhstan) and immediately come back to
Earth with a trajectory again with periapsis at Earth orbit and apoapsis
at Neptune orbit, then you will get to Earth orbit in front of Earth,
since your angular rate is higher than that of Earth. You can easily
solve that problem by staying on Mars for a while after having planted
the flag of China. Since Mars' orbital angular rate is lower than that
of Earth, Earth will catch up during your stay. The problem with that is
that you spent enough fuel to reach Neptune just to get to Mars. So if
you want to stay only five minutes on Mars to plant the flag of
Zimbabwe, you choose a transfer orbit with an apoapsis at X, where X is
a distance from the sun somewhere between Mars (which would return you
behind Earth) and Neptune (which would return you in front of Earth)
such that you return at Earth (X is in fact somewhere in the asteroid belt).

If you want to go even faster than that, you can choose the trajectory
of an orbit with periapsis lower than Earth and apoapsis higher than X
mentioned above. But that will cost you in delta-V.

Now, about the free return trajectory if you decide that you don't
really want to plant the flag of [choose your country here] on Mars.
When you reach Mars, you have the right speed to return to Earth, your
only problem is that you are not going in the right direction. But by
passing by Mars, gravity will change your direction, you just need to
properly choose at what altitude you do your Mars flyby.


Alain Fournier
 




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