Space Elevator

[Brian H]

Aeronaut wrote:

Another major issue I see with Space Elevator besides the tether material is its throughput. What is the planned speed and the amount of payload it can deliver?
If we say that it can deliver a few tons of payload per day,
then the infrastructure costs (especially with alternative cheaper-than-currently methods) will be a very long term investment
and might not even pay for itself.

My understanding is moving 30 ton loads (probably gross earth weight) at 120 mph most of the trip, for a 30 to 45 minute trip each way. Say 720 gross tons per day for a guesstimate…
I’ve seen some suggestions of using simultaneous up-down transit to get both energy offset and mass maximization. The cable, also, can theoretically hold more that one car going up at a time.

But 120 mph takes 200 hours to get 24,000 miles up. AKA over 8 days!

[Breakable]

I don’t see myself a multi-load tether as a solution without improving the concept because it means that the strength of the tether must be increased to accommodate more load.
Actually I even wonder: what is the advantage of using a tether? Basically the only problem it addresses is avoiding reaction mass.
I would love to compare different lifting concepts on efficiency and see their advantages:fanned lifter vs plane vs balloon vs tether.
I think probably balloon would be the most efficient method for lifting.
Of course it would work only until the edge of atmosphere where you would need either a tether or reaction mass (balloon gas?).
That could reduce tether strength requirements and allow for multi-tethering or maybe produce a totally new orbital lifting concept combined with some innovative propulsion concept (dpf?).

[Breakable]

Just to point out that weather balloons can go as high as stratosphere
http://upload.wikimedia.org/wikipedia/commons/f/f9/Atmosphere_layers-en.svg
Definitely a SSTO vehicle 😀

[Aeronaut]

The quick trip is to the “off-shore” activities that will pop up around 60 miles. That’s where I expect the first tourist stops to be, followed by commercial access fees to use any or all of the tether as a launch system. The less reaction mass that you have to leave the ground and or orbit with, the smaller, lighter, and cheaper your launch vehicle gets. This also pays dividends in smaller thrusters and shorter burns, which also contribute to lower reaction mass requirements.

The tether is easy to “understand”, which makes it easier to sell than a pendulum or a balloon (why hasn’t somebody done this before?). The tether concept also eliminates the need for heat shielding and a retro-burn to re-enter the atmosphere. While this all will probably seem quaint to an “enlightened” reader in less than 50 years, its about the best we can do right now and is still light years ahead of what most people think is possible.

[vansig]

Breakable wrote:
Actually I even wonder: what is the advantage of using a tether? Basically the only problem it addresses is avoiding reaction mass.

reaction mass is the single largest problem in rocketry!

it’s time for new physics; i want that reactionless thruster now, please. there may be no other way to get to the stars

[Aeronaut]

vansig wrote:

Actually I even wonder: what is the advantage of using a tether? Basically the only problem it addresses is avoiding reaction mass.

reaction mass is the single largest problem in rocketry!

it’s time for new physics; i want that reactionless thruster now, please. there may be no other way to get to the stars

The tether also eliminates the need for multi-G force liftoff and re-entries, which opens space tourism to almost anybody. Just as reaction mass has geometric multipliers, minimizing it has geometric dividers. The less mass of any type that you need, the better off you are.

I’d like to see at least one variation of a tractor beam. One pushes against mass, the other pulls toward a large mass.

[Brian H]

Aeronaut wrote:
…

I’d like to see at least one variation of a tractor beam. One pushes against mass, the other pulls toward a large mass.

I’d like to chide you for wanting “spooky action at a distance”, were it not that that’s actually a good description of every field and force in physics. Phagh! :cheese: :grrr:

[Aeronaut]

Brian H wrote:

…

I’d like to see at least one variation of a tractor beam. One pushes against mass, the other pulls toward a large mass.

I’d like to chide you for wanting “spooky action at a distance”, were it not that that’s actually a good description of every field and force in physics. Phagh! :cheese: :grrr:

I’d also like to add a transporter to my wish list. Flip Phone’s already accomplished.

[Brian H]

Aeronaut wrote:

…

I’d like to see at least one variation of a tractor beam. One pushes against mass, the other pulls toward a large mass.

I’d like to chide you for wanting “spooky action at a distance”, were it not that that’s actually a good description of every field and force in physics. Phagh! :cheese: :grrr:

I’d also like to add a transporter to my wish list. Flip Phone’s already accomplished.
Sorry. Transporter: if it can send to one location, it can also send to 2 simultaneously, and perhaps leave the original intact. How many of you arguing about which you is the you-est do you want?

[Aeronaut]

Does it have to send to multiple locations?

[Brian H]

Aeronaut wrote: Does it have to send to multiple locations?

How would you stop the transmitted matter transport info from being “mirrored” at 2+ receivers? It’s like trying to enforce copyright on digital copies. :cheese:
So far, the only physics that even hints at matter transport is very brief and carefully pre-arranged entanglement events, AFAIK, however. The matter transporter is more like a “creation machine” than an actual physics possibility. Viz the “replicator”, which materializes gizmos and cordon bleu meals at the touch of a button.

[vansig]

okay i apologize for letting this topic off the rails by mentioning a reactionless thruster.

keeping it real and in the twenty-first century,
colossal carbon tubes have the specific strength needed for a space elevator.

if a climber could accelerate as it goes up, then at a modest 1.1g it would reach high subsonic speeds in five minutes.. at which point it would be ~44 km out.

at 300 m/s top speed, total travel time from surface to 30,000 km out would be ~28 hours. but after reaching space, it could perhaps go faster?

[Brian H]

Perhaps a lower G-number, with constant accel/decel throughout, using inductive braking to recapture some of the energy, would make for a shorter trip. The seats etc. would of course have to rotate to cushion the decel. after turnaround.

[Aeronaut]

The stuff I was reading several years ago was based on a fairly constant 120 MPH velocity in both directions, powered by laser(s). That’s plenty fast enough for tourists only going around 62 miles to get their astronaut wings and join the zero-g club. The vast majority of the 69,000 mile tether would be used as spaceports to various destinations in both launch and recovery modes.

[spaceshaft]

Hello.

I found this discussion because … to keep things short without anecdotal stuff, I was looking for candidate technologies for my own space elevator project and its stabilization.

Yes, I take advantage of discussion forums to advertise my much less sexy space elevator, namely the SpaceShaft so my apologies for this action. Of course there are other reasons why I do this besides the advertising, (which I do since I have no budget for such things,) but very importantly because of the concentration of gray matter in forums like this.

For now I will just place a hyperlink to some descriptions of what I am proposing, I hope you find it interesting since it answers a lot of the outstanding questions being discussed. I really hope you try to demolish my idea.

http://spaceshaft.org from where you will be redirected to the temporary page at http://spaceentrepreneurs.ning.com/profile/NeslonSemino since the SpaceShaft website is being redesigned.

Live long and prosper

[Author]

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