Could a human walk on Titan's surface?

Michael Barlow wrote:

"BllFs6" wrote in message

Also...being surrounded by a "cold" vacuum isnt nearly as bad as being
surrounded by a cold gas...

trying to keep warm in a vacuum vs a dense atmosphere is like trying to

keep

warm in cold air vs cold water....

being in titans dense and chilly atmosphere would suck the heat out pretty
fast...but I would be surprised if decent insulation and a heat source

couldnt
keep a titan vistor warm


-Just an observation-

I brought and read many books to work all relating to the different
sciences of astronomy and physics and someone asked a question about space,
I don't recall the specific question but it mentioned the vacuum of space.

It is true to a *extremely* good approximation. It is difficult on the
Earth to produce a vacuum that is as good as in geostationary orbit.
Only a handful of particle accelerator chambers have a harder vacuum.

Hard vacuum in orbit is a nuisance for spacecraft since metal surfaces
can potentially cold weld when you don't want them to due to the lack of
oxide impurities on their surface.

I stated as a matter of fact that he should be thinking the other way
around, Space is not a vacuum, planets and stars are just points that have
higher pressure then outer space. I'm positive that I'm right but yet I see
people here and other space related places that should know better
suggesting space is a vacuum. So, am I right and if so why do the people
that should know better don't know better? And, If I'm wrong, could someone
enlighten me why?

Because the pressure even in our solar system is very very low. And in
interstellar and then intergalactic space it is even lower.

http://deoxy.org/vacuum.htm

Will serve as a rough guide to vacuums and their corresponding particle
densities. Hydrogen in interstellar space is around 1000 times less
dense than the best vacuum we have ever produced on Earth.
(it is mostly Helium that remains in a terrestrial vacuum)

Regards,
Martin Brown

Michael Barlow wrote:
I brought and read many books to work all relating to the different
sciences of astronomy and physics and someone asked a question about space,
I don't recall the specific question but it mentioned the vacuum of space.
I stated as a matter of fact that he should be thinking the other way
around, Space is not a vacuum, planets and stars are just points that have
higher pressure then outer space. I'm positive that I'm right but yet I see
people here and other space related places that should know better
suggesting space is a vacuum. So, am I right and if so why do the people
that should know better don't know better? And, If I'm wrong, could someone
enlighten me why?

You're both right--just in different ways.

Although, strictly speaking, space is not a vacuum, it is a hell of a
lot emptier than what we consider a very hard vacuum here on the Earth.
Interstellar space density is on the order of atoms per tens of cc.
Even in the solar system, it's on the order of atoms or perhaps tens
of atoms per cc. We cannot, as far as I know, achieve such vacuums with
our current technology.

As far as the difference between being in "the cold air" and "the cold
of space" is concerned, space is essentially a vacuum. There is only
one way for a space suit in space to lose heat: radiation. On Titan,
one loses heat in all three ways: radiation, convection with the cold
atmosphere, and conduction through contact with the ground.

At such cold temperatures, the problem will be movement. Humans have
joints, so our space suits must, too. It is these joints that will most
likely experience failure as they become brittle in the extreme cold.
We all remember what happened to the Challenger when its rubber O-ring
lost elasticity and the seal was broken. And that was at a temperature
hundreds of degrees higher than Titan!

No, I imagine that even if humans were to venture to Titan in person,
we would end up still carrying out "walks" robotically. The only
inherent advantage then accruing to a human on Titan rather than back
at home would be the lack of a time delay.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Brian Tung wrote:

Michael Barlow wrote:

I brought and read many books to work all relating to the different
sciences of astronomy and physics and someone asked a question about space,
I don't recall the specific question but it mentioned the vacuum of space.

You're both right--just in different ways.

Although, strictly speaking, space is not a vacuum, it is a hell of a
lot emptier than what we consider a very hard vacuum here on the Earth.
Interstellar space density is on the order of atoms per tens of cc.
Even in the solar system, it's on the order of atoms or perhaps tens
of atoms per cc. We cannot, as far as I know, achieve such vacuums with
our current technology.

We can, but not for very long. I was surprised to see how much the very
best terrestrial vacuum had improved since I was last involved.

Apparently itis now of the order of 1000 atoms/cm^3 or about what you
get in orbit 1000km above the Earth's surface. 10^10 atoms/cm^3 was
bleeding edge terrestrial hard vacuum not all that long ago (and is
still good enough for most production semicon chip lines).

Regards,
Martin Brown

RichA wrote:
Given current spacesuit technology, how long
could a person survive on the surface
of that moon?
-Rich
More to the point, what could they see ? It must be pretty darned dark
out at Titan.

Steve

Thanks Brian, and Martin.
--
Michael A. Barlow

"Martin Brown" wrote in message
...
Brian Tung wrote:

Michael Barlow wrote:

I brought and read many books to work all relating to the different
sciences of astronomy and physics and someone asked a question about
space,
I don't recall the specific question but it mentioned the vacuum of
space.

You're both right--just in different ways.

Although, strictly speaking, space is not a vacuum, it is a hell of a
lot emptier than what we consider a very hard vacuum here on the Earth.
Interstellar space density is on the order of atoms per tens of cc.
Even in the solar system, it's on the order of atoms or perhaps tens
of atoms per cc. We cannot, as far as I know, achieve such vacuums with
our current technology.

We can, but not for very long. I was surprised to see how much the very
best terrestrial vacuum had improved since I was last involved.

Apparently itis now of the order of 1000 atoms/cm^3 or about what you
get in orbit 1000km above the Earth's surface. 10^10 atoms/cm^3 was
bleeding edge terrestrial hard vacuum not all that long ago (and is
still good enough for most production semicon chip lines).

Regards,
Martin Brown

On Tue, 18 Jan 2005 20:39:16 +0000, Steve wrote:

More to the point, what could they see ? It must be pretty darned dark
out at Titan.

I'm sure you could see comfortably- perhaps like a dark, stormy day on Earth.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Steve wrote:
More to the point, what could they see ? It must be pretty darned dark
out at Titan.

Saturn, and therefore Titan, are about 10 astronomical units away from
the Sun. They therefore get about 1 percent of the light that the Earth
does. Titan's clouds then reflect another half of that away; the rest
of the light, amounting to half a percent of what we get on a clear day,
contributes to the overcast glow at the surface.

That may not sound like much, but it's "only" a drop of less than six
magnitudes--nearly 2,000 times as bright as a night illuminated by the
Full Moon, in other words. Think twilight just after sunset and my
guess is you're pretty close.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Chris L Peterson wrote:

On Tue, 18 Jan 2005 20:39:16 +0000, Steve wrote:


More to the point, what could they see ? It must be pretty darned dark
out at Titan.


I'm sure you could see comfortably- perhaps like a dark, stormy day on Earth.

Thanks Chris,
I should have searched first...
http://saturn.jpl.nasa.gov/science/titan-atmosphere.cfm

"350 times brighter than earth on a moonlit night". So pretty bright.

Steve

Steve wrote:
"350 times brighter than earth on a moonlit night". So pretty bright.

Interesting! So either I've erred in my calculations, or the clouds of
Titan reflect more light than I suspected.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

What about on Mars, without a spacesuit?

Warmest temperatures on Mars are something like +40F (+4C) as I recall.
Could a human at one of these warm locations take a big gulp of air
inside the spaceship and run outside holding his breath for a few
seconds, then run back inside, without getting killed? Assuming no dust
storms, volcanoes, etc. are in progress at the time, of course. What
would kill him, if anything?