Space elevator - closer to reality

how long would a launch ramp need to be in order to maglev/railgun equipment into space without destroying it? it seems like it might be easier to railgun our materials into space and assemble them there. perhaps have very small robots build larger ones, which would then build larger ones, which would then build our space stations. All of it starting small enough, and hardy enough, to withstand a railgun's acceleration. just a thought.

 

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All the comments are good, even the very negative ones. It appears the CNT ribbon will not be strong enough for a starter thread with a cross sectonal area of one square millimeter. Thicker and/or wider means rapidly escalating cost and the need for a heavy lift rocket to get it to Geo orbit or splice many separately lifted to space segments. A dozen other problems may be show stoppers. I agree a supersonic rotating tether has a better chance of sucess and will test in part the feasability of the much more useful space elevator. The motors that propel the lift robots/ climbers will get hot. Heat is difficult to dispose of in a vacuum. The laser beam that powers the lift robots will heat the ribbon dangerously close to the failure temperature of the epoxy binder at least occasionally. Neil

 

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Hereis a paste from a tread I wrote about a year ago. Post subject: Alternative space elevator
Some apparently brilliant people think we can't build the space
elevator as Dr. Edwards envisions, so let's analyze some
alternatives. Space rated tether may fall short of projections
for CNT = carbon nano tube. Segments 3700 kilometers =
2200 miles long, 20 micrometers thick, 100,000 micrometers
wide = two million square micrometers = 2 square millimeters
= 0.02 square centimeters = 0.02 grams per cm length = two
grams per meter of tether = 7,400,000 grams of CNT =
7.4 metric tones of CNT if the average density is one
(same as water). This permits starting construction as soon
as 1% of the required CNT = carbon nano tube is available,
even if the CNT is slightly substandard. This can be launched
from the space shuttle or several other existing launch systems.
Corealis effect will make it more horizontal than vertical, but
an ion engine pulling one end to an atitude of 4000 kilometers
will make it approximately vertical in a few weeks. Gravity and
centripetal force help, but they are slow. A half ton climber
can start moving on the tether as soon as the first kilometer
has been unwound off the reel. The climber can get its power
from surface of Earth lasers just as Dr. Edwards plans, except
the solar panel is a moving target. If problems occur at 4000
kilometers, we may have to rethink laser propulsion. Control
of the climber should be temporarily from the space shuttle
as it may be some help in unwinding the tether. The climber
can start adding a thread before the tether reaches vertical.
At 37 kilometers per hour, average, it will take 100 hours to
add one re-enforcing thread. Hopefully improved models can
lay thread faster. After the thread is in place the reel will be
released making the climber lighter and faster. Fast start
and direction reversals will be tested making transients of
various kinds on the tether. A stretch transient will reflect
back and forth between the ion engine and the climber with
a period up to one day, if the transient moves at an average
speed of 308 kilometers per hour. Maximum resonance will
be attempted to learn how to make, utilize and surpress
transients. This tether should attempt to snatch a payload
from Earth's upper atmosphere with a compression transient
as this may be a partial alternative to a laser powered elevator.
A lot of energy is stored in a transient on a 100,000 kilometer
tether. The climber needs to be tested at full power, in
vacuum, in sunlight AND bathed in the energy from the Earth
laser to be sure it will not overheat. Likely a large radiator
will be necessary to dispose of waste heat.
Assuming the first segment looks good, ten are needed to
geo altitude, 27 to the far end = 100,000 kilometers altitude.
The tether slows as each segment is added, until the tether
is stationary (except for trancients) with respect to the
equator of Earth, before the last segment is added. This
shorter segment is designed to be reliable in Earth's
atmosphere. The weight of last shorter segment pulls the
entire tether downward slowly to the anchoring point on an
at sea platform. Ballast is enroute to the far end to stop the
tether from falling toward Earth. A properly timed
compression transient (10 day period?) can help restore
tension after the tether is attached to the at sea platform.
I'm sure I have some errors, so please correct, embellish
and/or comment. Neil

 

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And then some jerk in a Cessna flies right through it!

 

The ribbon will be black so even an alert pilot could crash into the ribbon. The plane would likely be totaled. Any chance the ribbon would be unsevered? Neil

 

Space Taxi

Create a SPACE PULLEY instead of Space Elevator. ​

We can have a pulley hanging form space just above the atmosphere. The pulley hangs from a geo-stationary Space Taxi Station.

A small Space Taxi is released up using a very very large helium balloons. A platform can be made that has large number of huge helium balloons below it. The Space Taxi is stationed on this platform before the whole platform is released.

When the platform reaches to the limit that it rise up in the atmosphere, Space Taxi takes off form the platform using jets propulsion and quickly reaches to the hook of the Space pulley which is just above the atmosphere and hooks itself to it. After this the Space Taxi station just pulls up the Space Taxi.

Note : All this is done with minimum fuel requirements compared to the other technologies, so what say ?

PS. A compressor can be used to bring the balloon Platform back on earth.

 

A compressor needs lots of energy, otherwise it is a good way to reuse the helium. The world supply of cheap helium is inadequite for lots of "very,very large" balloons. Hydrogen presents a negligible fire hazzard as long as the balloons stay above about 50,000 feet. Mathematicians claim launch from 50,000 feet is not as beneficial as we think, but it is a valid method of getting into space. One of the problems is we need to accelerate about 17,000 miles per hour to reach LEO = Low Earth Orbit. Neil

 

PS> wont it be cheaper to launch from mount everest, or the tallest mountains in the world ?

Thank Neil Cox, Atleasts there are some brainy people left in this forum who would respond to my posts.

1) After lanching it dosent matter how long the balloons take to come back down, hence a solar compressor would help in reducing the launch pads weight.

2) I didnt knew that, why cant we make more ?

3) Why cant we create smart material balloons that will never leak the hydrogen, after all dont we use hydrogen for propulsion today ? these days people also talk of hydrogen cars.

4) I think Any cost saving should be welcomed. Are U telling here that balloons cant go beyond 50000 feet ?

5) So ? Wont it be better if we get low air resistance and greater height to reach there ?

 

Launching from tall mountains helps. Unpleasent for the humans is the main hold up. Improved robotics may make launch from moutain tops practical by the time we have a launch site constructed on a high mountain top. 1 Do you have a design for a solar compressor in mind? How long may matter. Time is money if there is a back log of customers ready to launch. 2 Nearly all helium is separated from natural gas and volitiles in petrolium in a few locations. At present helium is a low value by-product. High demand would increase the price by perhaps 100 times before it would be cost effective to extract the tiny amount of helium from the atmosphere. 3 Linde claims they have a non-leaking tank for hydrogen cars, so it is likely possible to reduce the hydrogen losses from balloons. 4 Potential cost savings are often ignored for various reasons. I think 130,000 feet is the record altitude for a balloon, but the payload decreases rapidly above about 50,000 feet. 70,000 feet might be the best trade off for your launch platform. 5 I agree lower air resistance is likely more important than being closer to space for your space pully and platform 6 mechanical friction at thousands of points along your pully system may be the show stopper which is why magnetic levitation is one alternative being considerd. Neil

 

As far as I know the French Bullet train is the closest to a large scale fast rail gun built to date. Much faster would be necessary to reach GEO or low Earth orbit even starting from the top of a very high moutain, mostly due to air resistance. It might be possible to build a rail gun 29,000 feet tall using CNT = carbon nano tubes, but we need to work up gradually to such a monster or we will make too many costly errors. The CNT is not yet available in construction quantities, and it may not be worth the high cost for most applications when it is mass produced. Neil

 

" mechanical friction at thousands of points along your pully system may be the show stopper which is why magnetic levitation is one alternative being considerd.
- Neil Cox"

Whats that ? there is gona be only one point of friction.

 

doesn't an elevator have to be anchored from the equator?

There isn't much equatorial land (above sea level) to begin with so I think just finding a place to put it, let alone one that could handle the kind of air/sea traffic an elevator would have, is a bigger issue than altitude or planes crashing into it. After all, illuminating the small part of the elevator that intersects commercial or military airspace is a tiny issue compared to actually building the thing.