Re: How would you connect two space stations?
From: William Mook (william.mook_at_mokindustries.com)
Date: 02/18/05
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Date: 18 Feb 2005 08:04:46 -0800
Imagine a transparent spherical structure made ofa stationary glass
bubble. This glass is blown from silicon oxide and sodium carbonate
with a blowing agent in zero gee from asteroidal feedstock using a
solar furnace.
Once the glass bubble is blown to sufficient size and appropriate
thickness, it is 'tapped' with access ports at its 'poles' and
evacuated of the blowing gas (carbon dioxide generated from an oxide
reaction).
Materials are inserted through the access ports and floated down to the
interior of the glass bubble.
The final materials brought to this stationary pressure vessel is are
aluminum air locks - connected with an aluminum structure - which
inserted in the access holes.
The sphere is pressurized with an oxygen/nitrogen atmosphere at this
point to create a shirt-sleeve environment.
The materials placed on the interior of the glass pressure vessel are
erected into a strip magnetically levitated strip covering half the
interior surface. The stationary portion of the strip facing outward
through the glass is covered with solar cells which power the strip.
The moving portion of the strip, facing inward away from the glass, is
moved by solar power, accelerating to a speed necessary to maintain the
desired gee forces (0.5gee in this case)
There is a region between the stationary (or nearly stationary)
pressure vessel and moving band that consists rings that move with
gradually increase speed - the difference between each band speed is
about 2 kilometers per hour - the speed of a moving sidewalk. This set
of moving bands operates in a way very similar to the 'slidewalks' in
Issac Asimov's stories and in Robert Heinlein's short story "The Roads
Must Roll" with each band moving slightly faster than the previous
band.
One may float from the zero gee portion to a slowly moving band, and
then navigate from band to band in an easy manner as speeds and gee
forces gradually increase - until the wide central band is reached.
This allows for constant traffic between the stationary and moving
portions of the 'station' and with clever design provides for air
circulation and a number of other features.
Another method of navigating between the rotating and non rotating
portion of the station would be some sort of small aircraft that had an
operating speed that exceeded the speed of rotation at the station's
moving periphery. In this case a person could have a small aircraft at
their home in the moving section of the station, and take off,
navigating first to cancel the motion of the moving band, and then
landing on any portion of the moving portion of the station.
So one could walk to their destination or fly. When taking a vehicle
it will also be possible to fly out of station through one of the
airlocks mentioned previously. An aircraft could seamlessly dock with
a more energetic rocket propelled stage on its way through an automated
airlock the served the station to avoid hazardous accumulations of
rocket propellants within the pressure vessel.
One can also imagine a solar powered continuous airlock that operating
like a rotating door. Outbound sections would automatically
depressurize and the gases removed would be used to automatically
re-pressurize inbound sections of the airlock. That way, continuous
traffic could be maintained with space outside the pressure vessel as
well.
Leakage along the moving seams would have to be made up on a regular
basis, but in a high-traffic situation this materials that would be
made into make-up gas would be a very small portion of the total
traffic volume.
Putting numbers to this general picture we can imagine a stationary
bubble 1,000 meters in diameter. With an atmospheric pressure of
101,325 pascals the total pressure exerted by the air would be around;
F = pi * r^2 * p
where pi = 3.14159
r = 500 m
p = 101,325 pascals
F = 79,580,468,906 Newtons
http://www.engin.umich.edu/students/support/mepo/ELRC/me211/flash2/spherical_02.swf
The thin wall stress is given by;
sigma * 2 * pi * r * t
Where sigma = tensile strength of bulk glass is 0.487 GPa.
pi = 3.14159
r = 500 m
t = unknown
Solving for t;
t = F/(sigma * 2 * pi * r) = 5.2 cm
This is 163,361 cubic meters of glass - so this gives us the size and
mass of the original oxide powders that must be blown into a 1,000 m
diameter sphere.
Now rotational motion exerts an acceleration amounting to;
a = v^2 / r
and r=426 m (average between 363.5 (rim) and 500 (center)
while a = 4.91 m/sec/sec
so, we can solve for V of the band
V = sqrt(a * r) = 46.73 m/sec --> 164 kph
(about 100 mph)
So, if each band increased in speed by 2 kph, you'd need 82 bands to
accelerate to this speed. If each band were 2 m wide the set would
cover 164 meters along the circumference of the sphere. If the central
band started at 45 degrees - measured from the nearest airlock/pole -
then 164 meters would traverse 18.8 degrees - so, the first 2 kph band
would be positioned 26.2 degrees from the pole.
If the band were cylindrical in nature, and didn't follow the pressure
vessel wall, it would have a radius of 363.5 meters and the velocity to
attain 4.91 meters/sec/sec would be
V = sqrt (4.91 * 363.5) = 42.25 m/sec --> 152 kph
This would permit space under the cylindrical band for stationary
equipment that kept the band moving, it would also provide for a
constant gee force and direcdtion across the band. There would also be
fewer transition bands needed since the speed is also lower. The area
would be less than following the pressure vessel wall though.
Light would be available through the glass bubble, additional light
could be reflected through the glass in concentrated form and expanded
by appropriate optics - if needed.
Small areas of solar collectors operating at high intensity could be
placed in the high concentrated light source to provide power and heat
if needed as well.
Michael Smith wrote:
> On Fri, 18 Feb 2005 05:08:44 GMT
> "Mike Rhino" <october2003@alexanderpics.com> wrote:
>
> > Suppose you wanted two space stations, one with zero g and one with
.5
> > g with regular traffic going between them. Should they be
connected
> > together and how? When people move about within a space ship, that
> > changes the center of gravity. The spinning ship may have a wobble
> > which would cause a problem with rigid connectors. Slightly
flexible
> > could work. A connection would allow you to send power from zero g
> > solar collectors to a spinning ship.
>
> If the zero G platform is built strong enough to take some gravity
(the
> ISS is not) then it could be carefully coupled via a bearing to the
> rotating structure. The rotating structure could be trimmed by
pumping
> water around the rim.
>
> A better option would be to rotate the (near) zero G structure but
keep
> it close to the axis so gravity is low.
>
> Or you could use gravity gradients to provide gravity on an elongated
> station, and part of it will be in microgravity.
> --
> Michael Smith
> Network Applications
> www.netapps.com.au | +61 (0) 416 062 898
> Web Hosting | Internet Services
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