Re: Is it this easy to live on Earth?

On Oct 6, 1:26 am, BradGuth <bradg...@xxxxxxxxx> wrote:
On Oct 5, 7:41 pm, Willie.Moo...@xxxxxxxxx wrote:





This will have been the 7th time I've said the same thing, and the 7th
time you have ignored it.

The work required to raise the pressure of a gas from one pressure to
another is given by;

   W = n R T * ln(Pa/Pb)

Where n = moles
           R = rydberg constant = 8.314
           T = temperature (Kelvins)
         ln( ) = natural logarithm function
        Pa = the higher pressure
        Pb = the lower pressure

The atmosphere of Mars is 0.13% oxygen by volume
and its atmospheric pressure is no less than 0.6 kpa

So the partial pressure of oxygen on Mars is 0.00078 kpa

The atmosphere of Earth is 21% oxygen by volume
and its atmospheric pressure is 101.3 kpa.

So the partial pressure of oxygen on Earth is 21.273 kpa

The ratio of these two pressures is 27,273

The logarithm of 27,273 is 10.2

The temperature on Mars averages 220 K

An adult male consumes no more than 909 grams of oxygen per day
Oxygen molecules are O2 - which total 32 atomic mass units.   That
means that 1 mole of oxygen molecules equal 32 grams - this means that
909 grams is 28.4 moles

So, the amount of work needed to raise the pressure of 28.4 moles of
oxygen in the Mars atmosphere from 0.00078 kpa to 21.273 kpa is

   W = 28.4 * 8.314 * 220 * 10.2 = 529,847.89 joules

Divide this by 86,400 seconds in 24 hours - and this obtains 6.1 watts
continuous.

Now, oxygen requires 0.92 joules per gram per K.   Room temperature is
295 K - 75 K higher  than 220 K.   So, to raise 909 grams 75 K
requires an additional 62,721 joules.   Again divided by 86,400
seconds in a day this averages out to 0.73 watts.

So, to raise oxygen pressure to breathable levels and heat it to room
temperature requires less than 7 watts per person.

A similar calculation regarding water vapor in both Earth's atmosphere
and Mars' atmosphere obtains a lesser figure - the sum of all figures
is less than 10 watts per person.

In that case, cooling off a toasty and robust atmosphere and otherwise
extracting or converting in order to obtain as much O2 as you'd like
is another no brainer of hardly any local energy demand, and this is
especially impressive since none of the required energy (no matters
how much) need be imported, and unlike Mars as having essentially
zilch worth of water, there's likely hundreds of teratonnes of easily
accessible water within them acidic clouds surrounding Venus, which
also means that Venus already has nitrogen and mineral salts to work
with.

We couldn't have done it without you.

~ Brad Guth Brad_Guth Brad.Guth BradGuth BG- Hide quoted text -

- Show quoted text -

This is the fifth time I've said this - there is no free oxygen in the
Venusian atmosphere at all! Oxygen under high pressure and
temperature tends to react with things to form oxides. Which is what
happened on Venus, so the process will not work there. You can use
energy to break down CO2 into C and O2 - but that requires far more
energy to do that resulting in a higher power level per person.

No matter, the solar power available to a balloon floating at 50 km
altitude - where the temperature and pressure are survivable - is
rather high.

The main difficulty for anyone floating above the surface, or in
jimsuit

http://www.achievement.org/autodoc/photocredit/achievers/ear0-007

on the high pressure high temp surface - is the deep gravity well
presented by Venus.

To escape Venus requires 11 km/sec
To escape Mars requires 6 km/sec

Using the best available rockets our exhaust speed is 4.5 km/sec

So, this means

For Venus you need a 91.4% propellant fraction
For Mars you need a 73.7% propellant fraciton

With a structural fraction of 5% this means that

For Venus you need 278 tonnes for every 10 tonnes useful payload
landed on Venus

For Mars you need 47 tonnes for every 10 tonnes useful payload
landing on Mars.

Finally, lets not forget the stringent surface conditions on Venus
when compared to Mars. Pressure is 92x as high as on Eearth and
temperature is higher than can be achieved in your oven at high heat
at home.

We can build pressure suits and refirgerators that can survive in this
environment, even one filled with a sulfuric acid vapor.

We cannot build a rocket engine today however that operates at the
pressure and temperature of Venus' atmosphere. Their performance is
seriously degraded to nearly nothing. That's because the conditions
inside today's rocket chambers, approximate the temperature and
pressure on the surface of Venus.,

What is needed to operate on Venus is something like an arcjet rocket
- whose pressure and temperature of operation is several times greater
than the surface of Venus - and then a power supply adequate to
running the thing.

With an exhaust velocity of 16 km/sec - even on teh surface of Venus,
an arcjet can boost off the surface to 11 km/sec with only 49.8%
propellant fraction. With a 5% structural fraction this means that
22.1 tonnes vehicle can loft 10 tonnes to escape from the surface.

Since the arcjet rocket can use the atmosphere itself as a working
fluid, this amount of propellant can be reduced further to perhaps 5
tonnes or less - for use in the upper atmosphere.

The difficulty that must be addressed is the power required by the
rocket to produce adequate thrust. To lift 22.1 tonnes with an arcjet
rocket requires 4 gigawatts of electrical power be generated on Venus
and beamed through the thick atmosphere.

This may be achieved by releasing a light weight 4 km diameter balloon
whose surface is covered with MEMs solar cells and microwave emitters
- that beam energy to the descending capsule. If made thinly enough
this balloon may be made to mass only 30 tonnes or so. So, two
capsules are sent to Venus, the balloon unmanned, enters the
atmosphere and descends to 50 km - and deploys. It is sent a few days
ahead of the manned capsule. Successful deployment means the manned
capsule descends to the surface for exploration and then uses arcject
to launch back to Earth, leaving the power balloon for future
explorers.

Now the fact that Venus requires;

1) the development of special high pressure high temp suits
2) the development of advanced refirgeration
3) the development of advanced arcjet rocket technology
4) the development of advanced solar power technology

means that it will likely occur after, some think well after, the
exploration of Mars.

I tend to think that those in an age that desires to explore new
worlds will view these challenges as reasons to explore Venus not
reasons to avoid Venus.

And, yes, the 4 GW power plant used to power the arcjet rocket? It
will be tapped to run refrigeration and extract oxygen from Venus'
atmosphere. Not by molecular sieve, since no free oxygen exists on
Venus. But, by direct decomposition of CO2 into C and O2. along with
the direct decomposition of H2SO4 into H2O and SO2 to create water.
These are high energy operations compared compressing gases with a
molecular sieve, but small energy compared to the 4 GW power level
needed to generate the thrust to loft a 22 tonne capsule to Venus
escape.

.

Relevant Pages

  • Re: Is it this easy to live on Earth?
    ... Pa = the higher pressure ... temperature requires less than 7 watts per person. ... and Mars' atmosphere obtains a lesser figure - the sum of all figures ... also means that Venus already has nitrogen and mineral salts to work ...
    (sci.space.policy)
  • Re: Where can you see the back of your head?
    ... there and somehow avoid being crushed to death by the atmospheric ... pressure, and if you can also survive heat slightly greater than the ... I think the atmosphere on Venus is thick and murky enough that you couldn't see very far at all; certainly not all the way around the circumference of Venus. ...
    (rec.puzzles)
  • Re: The weather and the many different factors that drive it...
    ... > winds travel upwards and suck air away from the surface of the Earth ... > like a giant vacuum cleaner, decreasing the air pressure above the ... > the levels in the atmosphere involved. ... > Troposphere where in reality the Stratosphere has a part to play. ...
    (sci.geo.meteorology)
  • Re: The Cold Equations
    ... I have seen closeup photos of Venus taken by the Russian Lander. ... pressure, immense heat, rivers of sulphur. ... On the Moon, for instance, you retrofire until ... >>Absolute stealth is absolutely necessary for all U.S. armed forces. ...
    (sci.space.shuttle)
  • Re: world with less air pressure - survivable?
    ... provides a great pressure garment - you don't "explode in a vacuum", ... At 37 deg-C, the vapor pressure of water is 0.07 Atm, ... Why do you think a lower-density or lower-pressure atmosphere would ... but also the atmospheric temperature gradient. ...
    (rec.arts.sf.science)