Re: Is it this easy to live on Mars?

Now, no one likes being called narrow minded in the modern age. But
its clear that there are no known propulsion systems that will allow
us to lift off from the surface of Venus once there. Even so, there
may be other propulsion systems developed that might allow it.

Here is one;

http://en.wikipedia.org/wiki/Arcjet_rocket

An adaptation of an arcjet rocket into an arcjet jet operates at a
temperature of 2,100C well above Venus' 460 C and at a pressure from
930 Mpa - which provides a propulsion system capable of returning
samples from the surface, and later, perhaps, human crews.

Using the Venusian atmosphere itself at a working fluid in such an
engine array, would reduce propellant requirements further.

This system would have to be powered by microwaves from space or a
balloon hovering above the landing site since nothing else will
penetrate the thick cloud layer.

So, the revised conditions are;

Vf = 10.85 km/sec
Ve = 16.00 km/sec

u = 1 - 1/exp(Vf/Ve)
u = 0.493

using the same 8% structural fraction this means that 42.7% of the
total mass is payload. That means that a 10 ton capsule can be fired
to escape velocity by a 23.4 ton launcher on the Venus surface of
which 11.5 tons is propellant and 1.9 tons is structure and 10 tons is
the referenced capsule.

So, this system would need delivered to Venus the super performing
engine launcher and the power supply.

Pulling 2 gees at Venus requires about 50 tons of thrust be
generated. That's about 500 kilonewtons of force by an engine with a
16,000 m/sec exhaust speed. means 31.25 kg/sec of mass flow rate and 4
billion watts of microwave energy delivered to the vehicle.

A balloon hovering at 50 km altitude, filled with oxygen/nitrogen
atmosphere intercepts 2,800 watts/m2 from all directions both above
and below. The balloon covered with high efficiency light weight
solar cells convert 1,000 watts to electricity per square meter.
This means a spherical balloon covered with such cells would need to
have a surface area of 4 million sq meters - 4 square kilometers -
which means the balloon is 1.12 km in diameter (3,702 ft)

Assuming a thin film mems based solar cell microwave system that's 100
microns thick - masses 480 tonnes with this 4 million sq meter area.

Now, such a thin film system could be built on Earth orbit - using
technology similar to solar powersats - and then use solar wind and
solar light pressure to navigate from Earth to Venus - and either stay
in orbit or descend to float above Venus. Once you had a system in
place, you could do both. Have a permanent orbiting station, and
several permanent floating stations.

You would now be ready to mount an expedition to the Venusian surface.

Each station could dispatch several landers to a wide range of
locations across the planet - all of which would return to the
orbiting station.

As mentioned previously, the same technology that allowed the
operation of the arcjet rocket, would also allow operation as a jet.
So, it is quite possible that the lander system would return to the
balloon station - to be resupplied and replenished- for another
landing elsewhere.

Three or four landers per balloon - operated in sequence - would also
operate as propulsive units to navigate the station through the skies
of Venus.

An orbiting powersat station at Venus with four landers using advanced
arcjet propulsion- and a crew on board - would be the minimal sort of
system.for landing.

But note this requires several advanced technologies be developed at
once.

Not the least of which is a very high temperature refrigeration unit
which would consume considerable amounts of power - beamed from the
overhead source.

A multi-stage titanium/carbon refrigeration unit with an appropriate
mix of compressors and evaporators - and working fluids - would
operate efficiently on Venus - rejecting heat at about 1,000 C (1,768
F) and maintaining a 22 C (72 F) cabin temperature. These might even
be quite small using MEMs technology.

A small cabin might require only a few megawatts of continuous energy
to maintain temperatures under these conditions - which is less than
0.1% of the power needed for the rockets. So, a hovering balloon
could maintain a number of landing parties powered up - and perhaps
even a base or two on the surface.

With gigawatts of power from the balloon station, it would be rather
simple to process the surface rocks into glass with the appropriate
equipment. Such glass could be blown into a massive spherical
pressure vessel and evacuated - the interior surface vapor deposited
with a layer of aerogel material and another layer of glass deposited
atop that.- and evaporator coils deposited on that - with another
layer of glass atop that.

Within this evacuated and refrigerated sphere a station may be built,
and filled with oxygen and nitrogen and water vapor, and illuminated
with LED lighting.

In this way, very small amounts of imported material and machinery may
use Venusian materials to build infrastructure on the Venus surface.

A 1.12 km diameter glass sphere 30 meters thick and layered with
thinner sheets of silica aerogel/carbon/glass/ films - with multi-
stage evaporators operating with appropriate refrigerants - can
maintain a constant temperature within the sphere.

This glass sphere has the same 4 million sq meters of surface area.-
thermal conductivity of aerogels is 8 mW/m-K

http://eetd.lbl.gov/ECS/Aerogels/sa-thermal.html
http://en.wikipedia.org/wiki/Thermal_conductivity


H = k * A * delta-T / x

k = 8e-3 W/(mK)
delta-T is 438 K
A = 4e+6 m2
x = 1 m

H = 8e-3 * 4e+6 * 438 / 1 = 14.016 MWatts

So a refrigerator has to be set up to REJECT that must heat to
maintain conditions on the surface of Venus INSIDE the 1.12 km
diameter sphere.

Which is minimal compared to the 4 GW of power avaialble at 50 km
altitude.and above with the low mass system already described.

Heat pumps require about 65% of the heat they transfer to operate.
Assuming we can achieve this at Venus - this means we would need 9.11
MW to operate the refrigerator for this dome.

The interior filled with floors every 60 meters - would have 18 floors
and total 12 sq kilometers. At Earth normal illumination averages
126 watts per square meter - with 1,000 watts peak. This is 1.5 GW.-
still below the power level of the balloon or station described
above.

To maintain constant power draw - the station would have six sections
that follow six cosine curves that are 4 hours or 60 degrees out of
phase. One section would be midnight - another noon - yet another
sunrise or sunset.

Limited to 4 GW total power, two such stations could be supported per
ballon station. A separate pwoer supply would be needed for vehicle
launch and landing - or service periodically interrupted while
spaceflight operations were underway.

The need to pump out the heat produced by the lighting adds
substantially to the size of the refrigerator. adding 375 MW to the
load.-assuming nearly perfectly efficient LED light sources. Lower
efficiency light sources add even more to the power requirements -
both lighting and cooling.

This however is the scale of system that is possible to build with a
500 metric ton payload dispatched to Venus. - and is comparable to
what is possible on Mars with a similar 500 ton payload there.

Its not the thin film system described for Mars or one using off the
shelf rocket technology. A venus base requires substantailly more
materials be processed. It also requires advances in a large number
of technologies - from nanottech, to propulsion to power systems to
refrigerators to advanced AI and robotics.

Some would greet these requirements with glee - saying these are
reasons to go to Venus, not avoid it.
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