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Another problem with longer flights



 
 
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  #31  
Old January 30th 09, 04:55 PM posted to sci.space.policy
Rand Simberg[_1_]
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Posts: 8,311
Default Another problem with longer flights

On Thu, 29 Jan 2009 22:59:24 +0100, in a place far, far away, jacob
navia made the phosphor on my monitor glow in such
a way as to indicate that:

Pat Flannery wrote:


jacob navia wrote:

There are serious hints of living beings in Mars,


If by "beings" you mean bacteria...


If there are bacteria, there is surely something that eats those
bacteria.


Why?

Then, there are surely others that eat the bacterial eaters.

The bacteria could be at the base of a food chain.


They could also be at the top.
  #32  
Old January 30th 09, 04:59 PM posted to sci.space.policy
Rand Simberg[_1_]
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Posts: 8,311
Default Another problem with longer flights

On Thu, 29 Jan 2009 19:49:49 -0500, in a place far, far away,
"Jonathan" made the phosphor on my monitor glow in
such a way as to indicate that:


"jacob navia" wrote in message
...

In any case we need to explore more with robots first. Imagine
sending people only to find out that they can't establish anything
there... What a waste of time!

You just confirm what I am arguing :-)




This research certainly means the debate between robots and humans
as explorers has ended.


Nonsense.

The winner is obvious.


Only to the illogical.
  #33  
Old January 30th 09, 09:14 PM posted to sci.space.policy
Pat Flannery
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Posts: 18,465
Default Another problem with longer flights



Rick Jones wrote:
That presumes Europa started thawed and then froze right - with the
ice expanding inwards as well as outwards? Otherwise, since water
expands when it freezes, if it started frozen and had its core thawed
by tidal (?) forces there might not be as much pressure.


I wasn't thinking of it generating pressure by squeezing the water
(which is pretty much incompressible anyway, but simply from the weight
of ice on top of the water... the gravity is far lower than that of
Earth (about 1/6 ours, like the Moon) but that means if you have a ice
shell six miles thick over you it will generate the same amount of
pressure as it you were around one mile deep in the ocean. Military subs
tend to operate at a maximum depth of 1,000 -1,300 feet, so that means
if the ice crust on Europa is over around a mile thick, you are going to
have a very hard time building a habitat under it or venturing outside
of it in any sort of diving suit.
Unfortunately, no one knows just how thick the ice is, with estimates
ranging from around 700 feet to around 19 miles:
http://en.wikipedia.org/wiki/Europa_(moon)
If the lower estimate is correct, you could swim around in it in
conventional scuba gear, as it would be like if you were around 100 feet
deep on Earth. If the upper estimate is right, then it would mean that
you could only move around in it in some sort of deep submergence
vehicle, as it would be equivalent to being three miles deep in the
ocean on Earth.
Since the truth probably lies between these two extremes, it's pretty
unlikely you are going to be doing much swimming in the cold Europian
seas unless you are wearing some sort of a atmospheric diving suit with
propellers on it, and probably even that wouldn't be tough enough.
Which is just as well, as Europian Sono-Squids, though not as dangerous
as Titanic Titanian Methane Muskies, are still nothing to be trifled
with - particularly given they have a average IQ approaching that of
Einstein, and a hunger as rapacious as that of a six-year-old at the
movies. They would look upon human divers in hard suits entering their
realm as simply witless snack food that had delivered itself into their
hands like so many salted-in-the-shell peanuts and gnaw on them as they
discussed the finer nuances of the thirteen body problem. :-)

Pat
  #34  
Old January 30th 09, 09:27 PM posted to sci.space.policy
Pat Flannery
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Posts: 18,465
Default Another problem with longer flights



jacob navia wrote:
Pat Flannery wrote:


jacob navia wrote:

There are serious hints of living beings in Mars,


If by "beings" you mean bacteria...


If there are bacteria, there is surely something that eats those
bacteria.

Then, there are surely others that eat the bacterial eaters.

The bacteria could be at the base of a food chain.


Or they could be the only link in the food chain, as they appear to all
live deep underground if they exist - an area that has been notably free
from the evolution of large sophisticated lifeforms on Earth, although
I'm sure Edgar Rice Burroughs (Burrows?) could have come up with some
pretty frightening things living underground on Mars, probably with
eight legs and under the control of some blind albino race of cave
Martians, whose voluptuous women don't even realize that their skimpy
brassieres are on inside out.

Pat
  #35  
Old January 30th 09, 10:31 PM posted to sci.space.policy
Rick Jones[_3_]
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Posts: 587
Default Another problem with longer flights

Pat Flannery wrote:


Rick Jones wrote:
That presumes Europa started thawed and then froze right - with the
ice expanding inwards as well as outwards? Otherwise, since water
expands when it freezes, if it started frozen and had its core thawed
by tidal (?) forces there might not be as much pressure.


I wasn't thinking of it generating pressure by squeezing the water
(which is pretty much incompressible anyway, but simply from the
weight of ice on top of the water...


But water ice expands right? I was thinking more along the lines of
the ice forming a shell that sort of pulled away from the water
beneath it. Or if you will the water pulling away from the shell as
it contracted relative to the ice. I dunno, call it a Dysan sphere
made of ice? (OK, _LOTS_ of handwaving .

In otherwords is the ice actually supported by the water, or does it
simply form a hard shell around the water with its own structure
supporting it?

rick jones

They would look upon human divers in hard suits entering their realm
as simply witless snack food that had delivered itself into their
hands like so many salted-in-the-shell peanuts and gnaw on them as
they discussed the finer nuances of the thirteen body problem. :-)


Or discovered how this new food didn't really sit will with their
digestive systems


--
portable adj, code that compiles under more than one compiler
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
  #36  
Old January 30th 09, 11:33 PM posted to sci.space.policy
Pat Flannery
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Posts: 18,465
Default Another problem with longer flights



Rick Jones wrote:

But water ice expands right? I was thinking more along the lines of
the ice forming a shell that sort of pulled away from the water
beneath it. Or if you will the water pulling away from the shell as
it contracted relative to the ice. I dunno, call it a Dysan sphere
made of ice? (OK, _LOTS_ of handwaving .


All the cracks in it would probably rule out any sort of sub-ice voids
of any major size, but who knows?

Or discovered how this new food didn't really sit will with their
digestive systems


All joking aside, if the waters of Europa really are quite salty and
full of minerals as has been speculated, that could make them
electrically conductive enough for creatures living in them to use
sensory organs based on some form of electrical conduction to detect
things in their environment, as well as sound detection (which would
work very well indeed, as there would be no wave noise to contend with).
Without having to deal with storms, and only having thermal upwelling
rather than strong currents to contend with, animals in such a
environment might be very fragilely built and of quite large size.

Pat
  #37  
Old January 30th 09, 11:51 PM posted to sci.space.policy
Rick Jones[_3_]
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Posts: 587
Default Another problem with longer flights

Pat Flannery wrote:
All joking aside, if the waters of Europa really are quite salty and
full of minerals as has been speculated, that could make them
electrically conductive enough for creatures living in them to use
sensory organs based on some form of electrical conduction to detect
things in their environment, as well as sound detection (which would
work very well indeed, as there would be no wave noise to contend
with).


I seem to recall that one of the reasons it was/is popular for
submarines to hide under the Arctic ice was it was very noisy. Given
the cracks and tidal forces on Europa couldn't it be pretty noise too?

rick jones
--
The glass is neither half-empty nor half-full. The glass has a leak.
The real question is "Can it be patched?"
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
  #38  
Old January 31st 09, 12:05 AM posted to sci.space.policy
BradGuth
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Posts: 21,544
Default Another problem with longer flights

On Jan 27, 7:02*am, jacob navia wrote:
In any trip for humans beyond the moon (mars and beyond)
artificial gravity is a necessity.

Space.com reports:
[1]

quote
Astronauts that spend long months aboard the International Space Station
lose bone strength faster than previously thought and have a higher risk
of breaking their hips later in life, a new study reports.

A survey of 13 space station astronauts found that their bone strength
dipped by at least 14 percent on the average during their half-year
stays aboard the orbiting laboratory.

Three of the astronauts lost up to 30 percent of their bone strength
during their long-duration spaceflights, putting them on par with the
bone strength of older women with osteoporosis on Earth, the study
reported.
end quote

If in only 6 months trips they lose 14% of their bone strength,
in a trip of 2 years (the minimum time for a Mars trip) the strength
of their bones would disminish in such a measure that it would be a one
way trip only. They could not resist earth gravity when they come back.

This means that artificial gravity is a must for any trip that takes
more than 2-3 months. Note that the risk of breaking their bones much
later in life increases since apparently is very difficult to get
the lost strength back.

This is another big problem with humans in space and with human
spaceflight.

[1]http://www.space.com/scienceastronomy/090126-astronauts-bone-strength....
--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatiquehttp://www.cs.virginia.edu/~lcc-win32


Why do you folks keep excluding cosmic and secondary/recoil radiation?

~ BG
  #39  
Old January 31st 09, 12:12 AM posted to sci.space.policy
BradGuth
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Posts: 21,544
Default Another problem with longer flights

On Jan 29, 1:59*pm, jacob navia wrote:
Pat Flannery wrote:

jacob navia wrote:


* There are serious hints of living beings in Mars,


If by "beings" you mean bacteria...


If there are bacteria, there is surely something that eats those
bacteria.

Then, there are surely others that eat the bacterial eaters.

The bacteria could be at the base of a food chain.

*We know now, that Europa has an ocean below
* the ice. This means that we could establish a submarine settlement in
* there (if there is no life or if the life there is not incompatible
* with ours). The same in Enceladus.


The water pressure might be pretty high, as some estimates put the ice
cover as being many miles thick.


Pat


Most literature I have read put the ice cover as a very thin layer
of ice, since there was some dark liquid oozing out of the cracks in
many photographs sent by the Galileo spacecraft. An impact crater in the
ice hints also to a thin layer.

In any case we would not know anything about Europa if the robot
Galileo wouldn't have been there in the first place.

In any case we need to explore more with robots first. Imagine
sending people only to find out that they can't establish anything
there... What a waste of time!

You just confirm what I am arguing :-)

--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatiquehttp://www.cs.virginia.edu/~lcc-win32


Robots will cost us 0.1% of whatever a human outfitted expedition
would demand. However, the one-way human mission has terrific
potential.

Put those one-way tickets up for grabs on eBay, and see how much our
NASA gets offered (minimum bid $100M).

~ BG
  #40  
Old January 31st 09, 01:32 AM posted to sci.space.policy
Pat Flannery
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Posts: 18,465
Default Another problem with longer flights



Rick Jones wrote:

I seem to recall that one of the reasons it was/is popular for
submarines to hide under the Arctic ice was it was very noisy. Given
the cracks and tidal forces on Europa couldn't it be pretty noise too?


It could be, but I would think it would be less so than in the arctic
due to lacking anything like summer thawing and winter freezing. A lot
of noise in the polar oceans is probably due to icebergs toppling over
or fracturing and ice flows grinding together.
Still, ice fracturing can make a very weird and loud noise*. We hear a
lot of that come early spring on our local reservoir as the ice starts
to melt, and I didn't think of that problem in regards to under-ice
noise on Europa.

* Which is hard to describe - it sort of resembles the sound made by a
saw used as a musical instrument by bending it back and forth rapidly.
What it really resembles is the sound made when that guy punches one of
The Dirty Dozen in the top of his steel helmet in the latrine fight
scene in the movie "The Dirty Dozen". :-)

Pat
 




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