Author Topic: Space Elevator Initiative  (Read 5233 times)

Offline SEI

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Space Elevator Initiative
« on: 05/28/2018 07:58 AM »
Calling all potential brain contributors.

Here is a new train of thought to come up
with a theoretical solution to a Space Elevator:



The aim of these brainstorm videos is to visualize
a potential solution to a Space Elevator.

As the videos progress, they build upon the previous videos
refining the content with new research and taking into account
feedback and comments.

Please subscribe and share with anyone you think may be interested
to contribute to this initiative.

Offline speedevil

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Re: Space Elevator Initiative
« Reply #1 on: 05/28/2018 09:42 AM »
I suggest you read on the topic before trying to create visualisations.
As one example, the usable atmosphere terminates at some 40-60km for lifting, and balloons get intractably large for lifting moderate payloads before that.

Offline SEI

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Re: Space Elevator Initiative
« Reply #2 on: 05/28/2018 10:24 AM »
Brilliant !
Thank you speedevil,

At no point was this meant to be a finished visualization.
The idea is to open up a discussion and brainstorm session and I find that visuals
are always a great means to ping-pong ideas.

I will of course continue my research on the height of the balloons as I do know that the current record
holds at 53 km.
In the next video I will modify the height of the 'FLOATING DOCKS' but I would greatly appreciate it if you could
help with some Maths or theories that would properly lock the height choice that will be made.

This, of course is only one of the many things that will need to be figured out, but I am inching through as many
parts of solving this equation as possible.

Again, thank you for your feedback
and I hope you would like to keep contributing.

Please subscribe and share!



Online TrevorMonty

Re: Space Elevator Initiative
« Reply #3 on: 05/28/2018 10:47 AM »
 I don't remember video link but it was presented by guy with speech impediamet, he did whole session on space structures.

Theory is you build metal ring in LEO, lower the better, can be at 80km. Place sections at time in orbit then join it can be thin cable. Next build structure around small section of ring and separate it from ring by permanent magnets. Operates like magnet trains. Ring spins at orbital velocity while structure stays stationary. Run cable to earth  for the elevator.
We now have stationary platform at 80km which spinning ring supports.  Platform can be miles long, enough for railgun system to launch vehicles into space. In theory platform can extended right around earth allow transport system.

Offline Barrie

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Re: Space Elevator Initiative
« Reply #4 on: 05/28/2018 11:41 AM »
I don't remember video link but it was presented by guy with speech impediamet, he did whole session on space structures.

Isaac Arthur on YouTube?  Lots of speculative videos about space megastructures from him

Offline speedevil

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Re: Space Elevator Initiative
« Reply #5 on: 05/28/2018 11:57 AM »
I don't remember video link but it was presented by guy with speech impediamet, he did whole session on space structures.

Theory is you build metal ring in LEO, lower the better, can be at 80km. Place sections at time in orbit then join it can be thin cable. Next build structure around small section of ring and separate it from ring by permanent magnets. Operates like magnet trains. Ring spins at orbital velocity while structure stays stationary. Run cable to earth  for the elevator.
We now have stationary platform at 80km which spinning ring supports.  Platform can be miles long, enough for railgun system to launch vehicles into space. In theory platform can extended right around earth allow transport system.
This is all nice to sketch on paper, and tends to fall apart badly when you realise that the required magnetic field and losses due to that, and total mass all makes it profoundly unphysical.

The orbital beanstalk, where you have a tether going to 40000km or so is easy to see where all the stress comes from, and it's fairly simple to calculate the mass from first principles and get a more-or-less correct answer.

In other cases, the forces can be hidden by implicit assumptions, and losses by assumptions there are no losses in magnetic structures.
As one example, your ring needs to be both considerably more massive than the 'station' and have a very large tension on it to support the excess speed it needs to support the station and remain in orbit, and not intersect with the atmosphere.

Megastructures tend to have megaforces, and unless you can give detailed explanations of the power consumption (for example) of your magnets, and why they do not in fact cause too much drag, you are at the 'if you light the bottom of a fuel tank you get a rocket, it's easy' level of explanation.



Offline CameronD

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Re: Space Elevator Initiative
« Reply #6 on: 05/29/2018 11:46 PM »
And on the subject of power: AIUI you a proposing to build a very effective lightning conductor, discharging atmospheric static electricity to ground on a semi-continuous basis.

Perhaps you'd do well to forget all this Space Elevator nonsense and build a power station instead?
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline SEI

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Re: Space Elevator Initiative
« Reply #7 on: 05/30/2018 02:30 PM »
I'm glad you bring up the power issue.
This of course will be an enormous topic when I get around to it. I've been toying with a few ideas so far,
one of which will need to be patented first.

It may well be that we can use this 'lighting rod' though as the or one of the sources of power to bring the pay-loads up among other things.




Offline aceshigh

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Re: Space Elevator Initiative
« Reply #8 on: 06/03/2018 01:10 AM »
I don't remember video link but it was presented by guy with speech impediamet, he did whole session on space structures.

Isaac Arthur on YouTube?  Lots of speculative videos about space megastructures from him

Asimov Clarke. He has sine very good videos.

Offline SEI

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Re: Space Elevator Initiative
« Reply #9 on: 06/03/2018 05:11 PM »
Here are the current thoughts for the next video
regarding the height of each stage:
BASE               (5-10km)
FLOATING DOCKS    (60-80km)
OPUM               (80-200km)
SPACE DOCK            (340km)

Offline meberbs

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Re: Space Elevator Initiative
« Reply #10 on: 06/04/2018 07:15 PM »
Here are the current thoughts for the next video
regarding the height of each stage:
BASE               (5-10km)
FLOATING DOCKS    (60-80km)
OPUM               (80-200km)
SPACE DOCK            (340km)
Rather than making a video with different numbers you should do some actual research and calculations.

Check out the actual altitude of mountains, and the few bodies of water that manage to exist in the altitude range you are talking about. https://www.thoughtco.com/ten-highest-lakes-in-the-world-1435123

Note that 10 km is more than 1 km taller than Mt. Everest, showing that you have not put the slightest thought into this.

Other things to do:
-figure out how big your balloons would need to be to support themselves, the cable/other structures, and the payload as a function of altitude.
-estimate the drag experienced by your "opum" vs altitude, for starters you can make some simplifying assumptions about the cable, and ignore the torque due to the drag being stronger on the bottom.
-estimate how much fuel the opum would need.
-figure out where all that fuel would come from (It will certainly be larger than the payload you are bringing to orbit.)

Offline SEI

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Re: Space Elevator Initiative
« Reply #11 on: 06/05/2018 09:41 AM »
Couple of things:

-1) The height I'm suggesting is actually 5-10 km as mentioned in the overhead information
and in the post you replied to.
-2) You're assuming that it is a natural lake.

Usually, visualizations are used to demonstrate a solution but the purpose of this brainstorm is to come up with that solution so in no way is this even close to complete. I'm using it as a 'sketch-board' for lack of better word.
This is to trigger responses, criticism and solutions and it being in it's very early stages, this is
just start of a concept. It may well be that this will evolve into a completely different train-of-thought
eventually provided it is backed with solutions.

With regards to the other things:

-figure out how big your balloons would need to be to support themselves, the cable/other structures,
and the payload as a function of altitude.

Agreed, this is part of the many things I have to narrow down which are not demonstrated in this crude video
I've already tweaked some numbers for the next video and the FLOATING DOCKS would more be at a height between 60-80 km. The current record is 53 km but I'm assuming every thing will need to be pushed beyond our current possibilities.

-estimate the drag experienced by your "opum" vs altitude, for starters you can make some simplifying
assumptions about the cable, and ignore the torque due to the drag being stronger on the bottom.

This is definitely one of the hardest problems to solve. In the next video, so far (...and of course open for discussion), my idea is to add a ramp on top of the FLOATING DOCKS that accelerates the payload in a trajectory that coincides with the OPUM device that will pick-up the pay-load.
Also, the heights have changed for that too, now more at the 80-200 km level.
Hard to describe, so I will try my best to explain it visually in the next video for feedback.

-estimate how much fuel the opum would need.
-figure out where all that fuel would come from (It will certainly be larger than the payload you are bringing to orbit.)

I've not dived too deep in that yet as I'm trying to isolate some more fundamentals right now (such as heights)
but one video I watched interested me greatly:

I'm hoping this can reduce the amount of fuel/energy that is required.

A little extra information for the next video:

-An initial train-of-thought I have for the OPUM to SPACE DOCK and then SPACE DOCK to SUMMIT are drones.
Open to suggestions...








Offline meberbs

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Re: Space Elevator Initiative
« Reply #12 on: 06/05/2018 02:57 PM »
Couple of things:

-1) The height I'm suggesting is actually 5-10 km as mentioned in the overhead information
and in the post you replied to.
Maybe I wasn't clear enough. More than 20% of that range is taller than any point on Earth's surface. In fact outside central Asia (the Himalayas and nearby ranges) there are no points on the Earth's surface above 7 km.  Allowing part of your range to be obviously impossible indicates that you aren't putting in any effort at all to think about what you are doing.

-2) You're assuming that it is a natural lake.
There are reasons that there aren't high altitude lakes, namely that almost everything that is fits in your range is a mountain peak where you could not build what you are describing.

Usually, visualizations are used to demonstrate a solution but the purpose of this brainstorm is to come up with that solution so in no way is this even close to complete. I'm using it as a 'sketch-board' for lack of better word.
This is to trigger responses, criticism and solutions and it being in it's very early stages, this is
just start of a concept. It may well be that this will evolve into a completely different train-of-thought
eventually provided it is backed with solutions.
If you want responses and criticism, then don't ignore them. I told you that a significant part of your range for your base station was taller than Mt. Everest, yet you just repeated the same range.

I've already tweaked some numbers for the next video and the FLOATING DOCKS would more be at a height between 60-80 km. The current record is 53 km but I'm assuming every thing will need to be pushed beyond our current possibilities.
You are just making up numbers and changing them randomly. That is a waste of time. It is not hard to look up atmospheric density, and figure out the size of a balloon needed to support a given mass at a given altitude, and whether or not that makes any sense. You have already been told that 60 km is the upper limit that makes sense. If you don't believe that number, do some math and see for yourself.

This is definitely one of the hardest problems to solve. In the next video, so far (...and of course open for discussion), my idea is to add a ramp on top of the FLOATING DOCKS that accelerates the payload in a trajectory that coincides with the OPUM device that will pick-up the pay-load.
This does nothing to address the problem. It is also not hard to calculate. Drag = C_D*0.5*density*v^2 * A. For the cable C_D would be about that of a cylinder, which is around 1 (or close enough for the purpose of an initial estimate.

Also, the heights have changed for that too, now more at the 80-200 km level.
Hard to describe, so I will try my best to explain it visually in the next video for feedback.
Not really that hard to explain, save your time with the video and do some calculations instead.

-estimate how much fuel the opum would need.
-figure out where all that fuel would come from (It will certainly be larger than the payload you are bringing to orbit.)

I've not dived too deep in that yet as I'm trying to isolate some more fundamentals right now (such as heights)
These ARE the fundamentals. Without them you can't pick heights, because you are just making up numbers with no consideration for reality.

but one video I watched interested me greatly:
...
I'm hoping this can reduce the amount of fuel/energy that is required.
This both helps and hurts you. Importantly listen to the part of the video about plasma. Your cable will probably melt.

-An initial train-of-thought I have for the OPUM to SPACE DOCK and then SPACE DOCK to SUMMIT are drones.
Drone just means "unmanned vehicle" and that is already what I assumed you were planning, because it would be pointless to require them to be manned given modern technology.

And from the other thread (You are not using a space elevator, so it is off topic there)
The 'space elevator' name is more to stay in line with the existing concept of 'not using rockets' essentially.
I've labelled this a 'multi-stage approach elevator' for now as the ultimate goal is to get to space as efficiently as possible.
Even ignoring the slowing down assuming you somehow can get the atmosphere to slow you down just the right amount, you then need to accelerate the payload by around 7km/s in addition to re accelerating the rocket by most of that speed. This will require a gigantic rocket, not significantly different in size than the ones used at ground level. You are barely changing the amount of work done by rockets in your scenario.

If you publish another video with the useless numbers you have provided up to this point, and without looking up the rocket equation, and figuring out how much fuel you need, you will just be proving to people here that you don't have any interest in actually pursuing this idea.



« Last Edit: 06/05/2018 03:07 PM by meberbs »

Offline SEI

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Re: Space Elevator Initiative
« Reply #13 on: 06/05/2018 04:17 PM »
Interesting answers.

-With regards to the BASE height, a lot of my train-of-thought will actually be expressed
in my next video despite the message at the end of your post.
In a nut-shell, the idea will be to use landfill and waste to create the enormous structure
that I've depicted, hopefully solving two problems in one go. This is why I believe we can
go higher than nature.
 
-air density: maximum of 60 km for FLOATING DOCKS.
I will look into it and revise that.

-I'm not entirely sure why the ramp idea on the FLOATING DOCKS does nothing to address the problem.
If you bare with me until the next video perhaps we could re-engage that particular topic.

-Yes a lot of calculations for the OPUM consumption of energy even after the explanation in the video.
He does explain in the video the effect that the wings have and the 'skipping off' of the atmosphere.
Could that not be paired with let's say solar power gathered in orbit by the OPUM?
(a little side-note, but the OPUMS can potentially stay up in orbit and keep circling until they
fill-up in energy...assuming that is enough of course, you seem to have deeper knowledge of this,
what are your thoughts?)

-I'm wondering if graphene is the answer against the plasma effect?
   plasma temperature : 1650 C
   graphene melting point: 4627 C

-I'm opened to suggestions to rebrand from Space elevator to something else once we know what it is.

It seems apparent that you have much more knowledge about the Maths behind this than I do, and that you
can bring a lot to the mix, which is why I created this thread in the first place. If you would like to
keep helping to contribute or at least point me in the right direction, it would be very useful.

Offline veedriver22

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Re: Space Elevator Initiative
« Reply #14 on: 06/06/2018 04:32 PM »
Ramps don't cause acceleration.  You need power to get over them.   

Offline SEI

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Re: Space Elevator Initiative
« Reply #15 on: 06/06/2018 07:34 PM »
Yes of course.

Here is the initial idea:

1-The OPUM will be comprised of 2 stages, with basically the actual 'picking-up' stage going ahead of the 'mother' stage, then decelerating during the pass over the FLOATING DOCKS.

2-On the FLOATING DOCKS, the ramp structure will actually have a profile that coincides with the trajectory of the 'picking-up stage' of the OPUM. The pay-load goes to the start of the ramp and accelerates along a mag-lev rail.

When both trajectories are aligned and the difference in speed is lowered, the pay-load can be hooked up to the OPUM.

This is the initial idea so far and I will do a first draft of it in my next video.

Offline meberbs

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Re: Space Elevator Initiative
« Reply #16 on: 06/07/2018 03:24 AM »
Interesting answers.

-With regards to the BASE height, a lot of my train-of-thought will actually be expressed
in my next video despite the message at the end of your post.
In a nut-shell, the idea will be to use landfill and waste to create the enormous structure
that I've depicted, hopefully solving two problems in one go. This is why I believe we can
go higher than nature.
You don't need a video to describe that and no one needs to see that in a video to tell you that you can't do that. You are talking about literally building a man-made  Mt. Everest out of waste. Besides the fact that waste would not pile nicely into a useable structure (mountains are generally rock not dirt) You would be talking about moving an amount of material equal to around 1 million years worth of trash generated by the U.S. While it may not be completely technically impossible, the cost would be beyond absurd. Meanwhile, starting a few km higher gives you essentially no significant benefits.

Before you post more ideas, try to think about them yourself, and do some related research. If you want to build a mountain out of waste, then google "volume of trash in U.S." and also google "mass of Mt Everest."
 
-I'm not entirely sure why the ramp idea on the FLOATING DOCKS does nothing to address the problem.
The problem is atmospheric drag on the OPUM and the many km long tether hanging from it (and speeds are such that drag matters even at altitudes where buoyancy is negligible.). A ramp for the payload is simply unrelated, and pre accelerating the payload, would only imply the tether moving even faster relative to the atmosphere.

-Yes a lot of calculations for the OPUM consumption of energy even after the explanation in the video.
He does explain in the video the effect that the wings have and the 'skipping off' of the atmosphere.
Could that not be paired with let's say solar power gathered in orbit by the OPUM?
(a little side-note, but the OPUMS can potentially stay up in orbit and keep circling until they
fill-up in energy...assuming that is enough of course, you seem to have deeper knowledge of this,
what are your thoughts?)
Energy is basically irrelevant, the problem is reaction mass. In space you have to throw propellant out the back in order to accelerate. This takes a lot of propellant. I can help you calculate a rough estimate, but the answer will be just to counter drag and accelerate the payload will take more than the mass of the payload. All of that fuel has to come from somewhere.

-I'm wondering if graphene is the answer against the plasma effect?
   plasma temperature : 1650 C
   graphene melting point: 4627 C
The plasma contains oxygen. from google:
Quote
Graphene combusts at 350 C

It seems apparent that you have much more knowledge about the Maths behind this than I do, and that you
can bring a lot to the mix, which is why I created this thread in the first place. If you would like to
keep helping to contribute or at least point me in the right direction, it would be very useful.
I am willing to help you with the math, but there is no point for me doing the math myself. I know what the answers will be in general from related experience. Telling you the conclusion won't help you much though, if you learn to do the calculations yourself, you can then re-run them for whatever variation you think of and see if it helps, and then you can skip a few dozen videos worth of ideas that don't work.

Offline supersubie

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Re: Space Elevator Initiative
« Reply #17 on: 06/07/2018 09:57 AM »
I don't remember video link but it was presented by guy with speech impediamet, he did whole session on space structures.

Theory is you build metal ring in LEO, lower the better, can be at 80km. Place sections at time in orbit then join it can be thin cable. Next build structure around small section of ring and separate it from ring by permanent magnets. Operates like magnet trains. Ring spins at orbital velocity while structure stays stationary. Run cable to earth  for the elevator.
We now have stationary platform at 80km which spinning ring supports.  Platform can be miles long, enough for railgun system to launch vehicles into space. In theory platform can extended right around earth allow transport system.

I believe the video you are looking for it Isaac Arthurs space elevator video from his Upward Bound series. Really worth watching a lot of this series if you are into building mega infrastructure to get us into space.


Offline SEI

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Re: Space Elevator Initiative
« Reply #18 on: 06/07/2018 10:45 AM »
Not entirely sure about you Maths or facts here:

Assuming the US generates 230 million tons of trash a year
and the mass of Mt Everest from Base Camp to Summit is
162 trillion kg, then:

162 000 000 000 000 / 230 000 000 000 = 704.3478 years
Quite a bit away from a million years

Here are a couple of other interesting facts:

-1.18 trillion KG of garbage is generated in the world every year
162 000 000 000 000 / 1 180 000 000 000 = 137.2881 years

-The global Waste is on an upward hill

-There is the existing waste stacked up in landfills around
the world that can be used.



I'm suspecting there will be some treatment to the waste and structural
work that will need to happen for that waste to be a solid enough foundation.

You've mention the absurdity of the cost. Do you have any calculations
you've done to back that?

I would also like to think that any meter gained in height for the BASE
is less energy that will eventually need to be used to defy gravity.



I agree that accelerating the pay-load implies moving the tether faster
relative to the atmosphere. The reasoning behind the acceleration is to
dampen the impact of hooking-up the pay-load. The faster the pay-load
is propelled, the less the OPUM (pick-up stage) has to
accelerate/decelerate/accelerate.
Yes, please do help to calculate the rough estimate and share the equations
so I can play around with the numbers.


I may need some enlightenment about plasma/combustion here. Any thoughts on
figuring out what the temperature of the tether would be? (let's say at ISS speed for now)
 
could we combine the strength of Graphene with a coating like the one on the space
shuttle thermal tiles? This would add to the drag of course.

Offline meberbs

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Re: Space Elevator Initiative
« Reply #19 on: 06/07/2018 02:28 PM »
Not entirely sure about you Maths or facts here:

Assuming the US generates 230 million tons of trash a year
and the mass of Mt Everest from Base Camp to Summit is
162 trillion kg, then:

162 000 000 000 000 / 230 000 000 000 = 704.3478 years
Quite a bit away from a million years
I was looking at numbers too quickly, forgot to convert tons and kg, still 1000 years worth. (order of magnitude is what matters here)

You've mention the absurdity of the cost. Do you have any calculations
you've done to back that?
Yes, but again, you should be doing some thinking on your own. How about you estimate the cost instead. (Hint: number of households in the U.S. times how much they pay for waste disposal will estimate how much it costs to move that much trash. Then consider the extra processing you mentioned, and needing to ship it across the continent. Look up global bulk cargo rates if you want to use global trash figures.)

I would also like to think that any meter gained in height for the BASE
is less energy that will eventually need to be used to defy gravity.
What you "would like to" think is irrelevant. Going to orbit is about moving very fast, not about defying gravity. Getting altitude is a small part of the problem of getting to orbit. Even magically teleporting an object to 400 km would still only save you less than 10% of the energy to get to orbit. If you can get a floating structure that extends up to 60 km, extending it down a few extra kilometers will be many, many times easier than literally building a mountain.

I agree that accelerating the pay-load implies moving the tether faster
relative to the atmosphere. The reasoning behind the acceleration is to
dampen the impact of hooking-up the pay-load. The faster the pay-load
is propelled, the less the OPUM (pick-up stage) has to
accelerate/decelerate/accelerate.
Yes, please do help to calculate the rough estimate and share the equations
so I can play around with the numbers.
First step is drag calculation. I already gave you the equation a couple posts back. Air density as a function of altitude can be researched online. Velocity is up to your design choices (varies with altitude along tether) area is determined by cable length and width. Cable width is determined by cable material density and strength to weight ratio (Assume kevlar for now) also determined by payload mass you want to design for. As a recommendation, you can break the cable into smaller segments, and pretend each segment has a constant velocity and ambient air density, based on the segment midpoint, then add up the results. For a first pass 5-10 km long segments is a good starting point for you. (There is calculus that does this better, but this is a good rough numerical equivalent.)

I may need some enlightenment about plasma/combustion here. Any thoughts on
figuring out what the temperature of the tether would be? (let's say at ISS speed for now)
Plasma means the material is so hot the electrons which bind atoms together into molecules have completely escaped from the atoms. Only special designed materials have properties that allow them to survive this environment. You can estimate the temperature you are dealing with using T = T_amb*(1+0.2*M^2) In this equation M is Mach number (velocity divided by speed of sound) and you can estimate T_amb as about 210 K, and the speed of sound for that temperature is 290 m/s. One of the few things working in your favor is that low density means that the heating is only a problem below maybe 100km, so that is the altitude below which air speed must be kept relatively low.
 
could we combine the strength of Graphene with a coating like the one on the space
shuttle thermal tiles? This would add to the drag of course.
Not really, thermal protection for re-entry speeds wears out with time and use. It would make getting an acceptable strength/weight on the cable extremely difficult even if it wouldn't be a maintenance nightmare. The only practical solution is to make sure nothing in dense atmosphere is moving near orbital speed.

Offline Paul451

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Re: Space Elevator Initiative
« Reply #20 on: 06/15/2018 04:57 PM »
SEI,

Re: Pick-up and release.

Given that you have a >100km tether on the "OPUM", and it's rotating during pick-up fast enough for the tip-velocity to counter orbital-velocity, then why wouldn't it just continue to rotate around a full circle, and release the payload at orbital+rotational velocity. It could fling the payload well beyond escape velocity (and by adjusting the release radius, any transfer orbit under that. Eliminating transfer burns between OPUM and Dock, and Dock and Summit.) The concept in the video requires the tip to accelerate to ~7km/s, pickup the payload, then decelerate 7km/s again.

[edit: fixed the acronym and added the bit about transfer burns.]

Re: Lake Impossible.

There's no point in having the base move. At 50 or more km height, the top would be able to move many kilometres back and forth even if the base is static. Indeed, preventing such movement from lower altitude winds would be a bigger issue. Which means that you'd want the tether under tension to prevent wobbles, which means you need positive net buoyancy and a strongly anchored base.



If you can get a floating structure that extends up to 60 km, extending it down a few extra kilometers will be many, many times easier than literally building a mountain.

Especially when the connections between the platforms already involves tethers tens of kilometres long.

Re: Thermal/re-entry issues for the pickup tether.

The pickup seems to be clumsily based on a rotovator. So the entry speed is enormously reduced, sub-sonic ideally, and is almost entirely vertical (the horizontal component mostly cancelled out. Mostly.) Of course, that doesn't explain the orbital mechanics shown in the video.
« Last Edit: 06/15/2018 05:11 PM by Paul451 »

Offline Paul451

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Re: Space Elevator Initiative
« Reply #21 on: 06/15/2018 05:05 PM »
Off-topic aside:



Re: Orbital Ring.

Ring spins at orbital velocity while structure stays stationary.

Nope. The ring has to spin faster than orbital velocity, or there's no momentum to transfer to the stationary structure.



Re: Orbital Ring.

As one example, your ring needs to be [...] have a very large tension on it to support the excess speed it needs to support the station and remain in orbit

No, the superorbital ring isn't under tension. It doesn't even need to be solid and is usually modelled as a particle stream. (Indeed, I'm not sure that a solid ring would be a good idea.)

[edit: typo]
« Last Edit: 06/15/2018 05:14 PM by Paul451 »

Offline SEI

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Re: Space Elevator Initiative
« Reply #22 on: 06/17/2018 08:18 AM »
Thank you meberbs and Paul 451,

A lot to think about indeed.
This video is now unfortunately too old, so the whole 100 km tether and the pick-up
aren't relevant anymore.  I will update this in the next video after having isolated
a few things first. I'm still investigating that at this point and will share.

Regarding the flinging of the pay-load, the original idea was to 'elevate' the pay-load
along the tether. The SPACE DOCK stage is there really as a platform for anything that needs
to be in low-orbit, such as satellites etc... The SUMMIT is for space travel.
You have introduced an interesting concept though, maybe some pay-loads just simply by-pass
the SPACE DOCK and go straight to the SUMMIT when necessary.

It hasn't been discussed thoroughly yet but there will definitely be room for figuring out
the transition between OPUM - DOCK - SUMMIT.

In the interest of methodology, I would like to compartmentalize the discussion a little bit.
Here are my thoughts/questions regarding firstly the BASE so that we can reach some sort of
consensus:

The mountain of waste:

The cost as far as I have calculated is very high and not necessarily eco-friendly which out-ways
the benefit of a communal landfill. I am however, still investigating a few options, mainly pipelines.
The thoughts have been based on all the garbage converging to a single point on the planet,
but perhaps multiple 'space elevators' might relax that eventually.
In any case, meberbs is right regarding the actual gain of creating a mountain versus dropping
more cable.

The lake:

I admit, I only introduced a lake because I had seen it in other videos. I assumed that it was
to allow for the base to have some wiggle room. I do like your idea of having to anchor the BASE
which was part of my next study. If the solution is to have an anchored base, then perhaps the idea
of a mountain might have some new purpose, such as to get as close as possible to the stratosphere
where the winds are more stable.

Offline meberbs

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Re: Space Elevator Initiative
« Reply #23 on: 06/17/2018 03:29 PM »
The mountain of waste:

The cost as far as I have calculated is very high and not necessarily eco-friendly which out-ways
the benefit of a communal landfill. I am however, still investigating a few options, mainly pipelines.
The thoughts have been based on all the garbage converging to a single point on the planet,
but perhaps multiple 'space elevators' might relax that eventually.
In any case, meberbs is right regarding the actual gain of creating a mountain versus dropping
more cable.
I have nothing specific to add right now, but I just want to thank you for actually listening to advice. All too frequently people come by with ideas, asking for thoughts, but end up being completely inflexible when confronted with issues with their plans.

Offline Paul451

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Re: Space Elevator Initiative
« Reply #24 on: 06/17/2018 07:51 PM »
You have introduced an interesting concept though, maybe some pay-loads just simply by-pass
the SPACE DOCK and go straight to the SUMMIT when necessary.

You might have missed my point. I wasn't saying to eliminate the other orbital stations, I said to use the tether to eliminate the rocket burn that is required to move the payload to another orbit. Any orbital change requires delta-v. Using the tether's velocity to not only capture, but also release, allows you to "cheat". (You can also use smaller rotovators at the higher orbits to capture the payload, avoiding even the small circularisation burns. Similarly, a rotovator in low-lunar orbit can exchange payloads between TLI and the lunar surface.)

Your concept seems to be recreating the rotovator concept, so you might as well take advantage of it. (Reading up on rotovators will give you a short-cut to understanding the pros & cons, and the calculations used.) The thing added by your concept is the floating platform at intercept altitude. Most use high-altitude aircraft or suborbital rockets to reach the intercept height.

Offline meberbs

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Re: Space Elevator Initiative
« Reply #25 on: 06/17/2018 09:21 PM »
I wasn't saying to eliminate the other orbital stations, I said to use the tether to eliminate the rocket burn that is required to move the payload to another orbit.
Just as a point of clarification, depending on design, this eliminates the need for chemical rocket burns. Some system is needed to keep this type of apparatus in orbit and spinning. As long as the mass of the payload is not too large a fraction of the on-orbit system, this allows a lower thrust, but more efficient propulsion method.

Offline SEI

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Re: Space Elevator Initiative
« Reply #26 on: 06/18/2018 10:59 AM »
I see.
I'm not entirely sure yet if this will apply to the new design of the OPUM stage.

Rotovators are definitely interesting and they may be a good solution for
the SPACE DOCK and SUMMIT stages to send and receive.

Offline alexterrell

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Re: Space Elevator Initiative
« Reply #27 on: 06/18/2018 12:09 PM »
In terms of balloons ...

This sci fi short story: http://space.nss.org/settlement/MikeCombs/bridge.htm
Has balloons holding up a linear accelerator at an altitude of 24km.

This was written before SpaceX and well before BFR which has taken the steam out of elevators etc - as in $100/kg is good enough.

Offline Paul451

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Re: Space Elevator Initiative
« Reply #28 on: 06/19/2018 06:05 AM »
Just as a point of clarification, [...] Some system is needed to keep this type of apparatus in orbit and spinning.

Yeah, but that applies to any momentum exchange tether, including SEI's. So I assume it'll already have something. Flinging a payload still reduces your fuel requirements by 80% or more.

Offline SEI

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Re: Space Elevator Initiative
« Reply #29 on: 06/19/2018 03:54 PM »
Here are some thoughts so far for the BASE and the first floor (20KM):

-Base is anchored down at altitude of 5 km                           
-cables go to 20Km high where they meet the first floor


__________________________________________
1) The balloons would be geodesic spheres:

The spheres would be made of some graphene-based material.
The sphere would be a double-layered geodesic sphere with
hydrogen filling the 'sandwiched' layer
Inside the sphere would be a partial vacuum/hydrogen mix
to reduce implosion risk.

--------
Equation to determine neutral buoyancy: R = 3TD/A
R: radius cm
T: skin thickness cm
D: Density = (2.2g/cm3)
A: Density air

R = 3 X 0.1 X 2.2 / 1.2 X 10^-3 = 550 cm

a vacuum sphere with a diameter of 11m, 0.1 cm's worth of
graphene shell at sea level would be neutrally buoyant.

--------
Now, Assuming:
30 M diameter geodesic vacuum sphere:
-0.1 cm worth of Graphene for double-layer
-20Km altitude, the winds are calmer.

Volume of sphere: V = 4/3pi r3
air displaced at 20 km = 0.088

LIFT = 1244.07 kg

--------
Rounding off:

-30 M sphere of hydrogen would weigh at sea level : 
 14137.17 X 0.083 = 1173.385 kg   
 lift would only be -> 70 kg

-The exact vacuum/hydrogen ratio or amount of graphene needed
 are unknown to me at this point in time but let's assume a
 contingency number of 20% which would bring the lift capacity
 of the geodesic sphere to:

LIFT = 1,000 kg (a round-number starting point for now)

--------
Average lift of column of geodesic spheres from 5-20km

at 05 km, lift = 10404.98  kg
at 10 km, lift =  5838.66  kg
at 15 km, lift =  2742.62  kg   
at 20 km, lift =  1244.07  kg

average lift = 5057.5825
If we remove 20% contingency and round off
average lift = 4000 KG

if
15000 / 30 = 500 spheres stack
then
500 spheres with average lift capacity of 4000kg

COLUMN OF GEODESIC SPHERES LIFT = 2000 tons from 5-20km


_______________________________
2) The weight of the structure:


-weight of cable:
   -If Kevlar:
      kevlar = 8 g/cm^3 = 8000000 = 8 tons / m^3
   
      1 cable size = 0.1 X 0.1 X 15,000 = 150 m^3
      1200 tons of kevlar
      Assume 5 cables (unknown):
      6000 tons of kevlar

   -If graphene:
      graphene = 2.2 g/cm^3 = 2200000 = 2.2 tons / m^3
      graphene 40 times stronger than kevlar

      If was equivalent in graphene:
      1650 tons of graphene
      but graphene being 40 times stronger => 41.25 tons

   -lift apparatus and pay-load = (unknown), assume 100 tons

   -structure : (unknown), assume almost equivalent to cable: 5900 tons   

-TOTAL WEIGHT: 12,000 tons if structure in kevlar

thought: this is just a starting point of an estimate, need to figure out structure,
other materials etc...
How much cable is actually needed ?
Is kevlar the right material?
What role can graphene have?

____________________________________
3) The drag of the geodesic spheres:

   If
   surface of 30m circle = 706.858 m^2
   Then total surface of a column of geodesic spheres is:
   500 X 706.858 = 353429 m^2
   Add
   10% contingency = 388771.9
   round off to 390000 m^2
   and
   3 bands of 5 km -> 390000 m^2 / 3 = 130000 m^2   

   Highest wind speed to withstand = 140 m/s = 504 km/h

   D = 1/2PV^2 DA

   05-10km: D = 1/2 X (0.7362 + 0.4127 / 2) X 140 X 0.5 X 130000 = 2613747 N
   10-15km: D = 1/2 X (0.4127 + 0.1937 / 2) X 140 X 0.5 X 130000 = 1379560 N   
   15-20km: D = 1/2 X (0.1937 + 0.0880 / 2) X 140 X 0.5 X 130000 =  640867 N

TOTAL WIND DRAG PER COLUMN OF SPHERES = 4634174 N

_________________________
4) Lifting the structure:

   If
   structure weight = 12,000,000 tons
   then one configuration could be:
   -4 X column of geodesic spheres = 8000 tons of lift
      Total drag would be: 18536696 N
      (drag of structure not included)
   -Array of 4000 geodesic spheres to make up first floor = 4000 tons of lift
      Drag of first floor to be determined depending on shape

TOTAL OF 6000 GEODESIC SPHERES

____________________
5) Further thoughts:

-The height of the mountain can be altered to help the equation.

-I'm thinking a first floor would be useful for stability, maintenance
etc... This may be an 'old school' way of thinking about this structure though.
Do we need floors or is there an umbilical cord only approach to reach eventually
the FLOATING DOCKS ?

-Is 20 km the optimum first floor? This seems to be where the winds quiet down,
 but perhaps there needs to be a lower floor than that.

-The column of spheres holding the cable and structure would probably help with
 safety. If the elevator was severed, the column of spheres would drop in altitude
 at first until it reached a neutral buoyancy altitude and bob, preventing crashing
 to the ground.

-How do we stabilize the structure? What are the solutions? fans that constantly
 re-adjust the position etc...




This is only a first draft to start plugging in some numbers.
I am missing quite a bit of knowledge on structural design and engineering if anyone
can point me in the right direction to help with the numbers and the accuracy of
my approach. And of course, let me know if some numbers or facts are incorrect.

Offline Paul451

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Re: Space Elevator Initiative
« Reply #30 on: 06/21/2018 02:32 AM »
SEI,

Why do you think a 1mm thick wall of graphene would withstand around 1400 tonnes of pressure? (Remember, it's not tensile strength that matters for an evacuated shell, but bending resistance.)

Offline SEI

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Re: Space Elevator Initiative
« Reply #31 on: 06/22/2018 02:44 PM »
Spot on question Paul451, admitedly I was originally focusing on these
spheres at higher altitude for the FLOATING DOCK and I seemed to have
concentrated only on lift capacity when going back down towards the BASE.
I forgot to think about pressure and buckling.

That's only part of the problem here though as I am struggling with all the
parts of the equation that I need to find out about. I have found a graphene
composite with a flexural strength of 116 N/mm^2 (the same as perspex) so far.


Here was the reasoning behind the numbers and how they came about.

1-This first document:

https://pdfs.semanticscholar.org/c050/8576da956a3e01c44c4b13c58728c9d33b51.pdf

According to his research, a vacuum sphere with a diameter of 250 cm and a thickness
of 0.1 cm of perspex would have neutral buoyancy.

2-From this patent, the double-layered approach that is being explained using more exotic
materials seem to strengthen the structure greatly.

http://akhmeteli.org/wp-content/uploads/2011/08/vacuum_balloons_cip.pdf

3-Both these approaches were based on spheres, so the stronger geodesic sphere structure
should help even more. (not entirely sure how to demonstrate the amount though)

4-I have allowed 20% of contingency for a mix of hydrogen/vaccum and possibly thickness
of the shell. knowing that I was missing elements to the equation, this was specifically
to help the buckling problem.

5-Other things I have missed include:

-mentioning that maybe more internal structure would be needed
-calculation is based on the mass of pure graphene, not a composite
-no evacuation device has been accounted for to create the vacuum
-inversely, regulation of the hydrogen level
-effect of temperature
-no paint weight has been accounted for

It may well be that the spheres for each altitude will have to have their own sets of optimal
parameters. Any thoughts on how to approach this?

Offline SEI

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Re: Space Elevator Initiative
« Reply #32 on: 07/12/2018 09:57 AM »
Here is the new video to recap what's been discussed and to introduce some new ideas as they stand




There are still quite a lot of unknowns and caveats but let's continue the discussion

Offline Paul451

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Re: Space Elevator Initiative
« Reply #33 on: 07/12/2018 11:53 AM »
SEI,

You're still burning a lot of fuel decelerating and re-accelerating the OPUM part. And the whole thing seems unnecessary, given your other assumptions.

If you think you can accelerate the payload to near-orbital velocity, why not orbital velocity? (Even if it includes a rocket-engine and carries itself into orbit, you'd be wasting less fuel than you will with OPUM's tragectory.)

Worse, the g-load on that launch oval-ring is insane. The turns have a 5km radius, I don't know what "near" orbital velocity you mean, but at 7km/s you are pulling 1000 g's. At just 5km/s, you are doing 500 g's. Anything about 2.25km/s, you exceed 100 g's on the turns.

But the thing is, if you think your payloads can tolerate 1000 g's, you would only need a 3km linear track to reach orbital velocity. With 50km of linear track, same length as your oval ring but straightened, you can reach orbital velocity at just 60 g's. There's absolutely no advantage to having an ring/oval track. Same length of track, vastly, vastly lower g-loads.

Aside 1: You may have an exaggerated view of atmospheric "skip". It doesn't save you any energy. All it means is that you come in shallow enough that re-entry drag doesn't lower your apogee all the way into the atmosphere. You still experience massive drag (lowering your apogee somewhat) and you still have to raise your perigee (and then apogee) using high-thrust rockets.

Aside 2: Geosync is not "Free of Earth's gravity". It's just a regular old orbit than happens to have an orbital period the same as Earth's rotation. To transfer between LEO and GTO still requires a 4km/s burn. (Plus a 1km/s circularisation burn.)

Not trying to be insulting, but I think you need to spend time playing with orbital mechanics until it becomes more intuitive. People rave over Kerbal Space Program. Also pick up the basic physics equations for linear and rotational acceleration (or find a trustworthly online calculator).



Aside 3, your previous reply to me: Why do you think a geodesic is stronger than a sphere for compression?

Offline SEI

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Re: Space Elevator Initiative
« Reply #34 on: 07/13/2018 09:21 AM »
I had looked at the linear acceleration and one of my original designs for the ramp was a slightly bent straight line.
However, to reach 7km/s at a tolerable 5Gs for humans, you need approximately 490 Km of track.
Not just that, assuming the Pay-load is 5,000 Kg, the Power needed would be approximately 850,000 kW to
accelerate the Pay-load in 140 seconds.
This is where the idea for the oval ramp came about; to get more track through revolutions and to relax the
amount of Gs during the acceleration process.
I have however failed to think about the rotational acceleration and yes... 1000 Gs is insane!
Side note: The added advantage of the oval track was the safety feature to decelerate in case the connection
with the OPUM didn't happen.

I had also started questioning the need for the OPUM stage.
My reasoning for it was that the Pay-load (at 5,000Kg) could be solely used for cargo/passengers, extra fuel
and as a heat-shield. The OPUM was there to be the mechanism part of the vehicle.
If the Pay-load needs to be self-propelled to reach the SPACE DOCK, then it probably would need to be bigger
and it would be even more demanding on the ramp.

From what I've read on the Buckminster Fuller Insitute page, geodesic domes seem to be structurally more strong. I thought the straightness of the triangular shapes is what gives the geodesic dome it's structural strength, ...and extrapolating from that the same for a sphere.
Or am I misinterpreting square panels VS triangular ones only? Would a perfect sphere be the optimal structure?

Offline Paul451

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Re: Space Elevator Initiative
« Reply #35 on: 07/13/2018 02:44 PM »
My reasoning for it was that the Pay-load (at 5,000Kg) could be solely used for cargo/passengers, extra fuel
and as a heat-shield. The OPUM was there to be the mechanism part of the vehicle.
If the Pay-load needs to be self-propelled to reach the SPACE DOCK, then it probably would need to be bigger
and it would be even more demanding on the ramp.

No. Each payload would need to carry enough fuel to restore OPUM from that dip and lift (the latter including the mass of the payload) which is necessary for each pick-up. Think about the mass of OPUM (and its rocket engines and payload-capture system), vs the mass of a single upper-stage type engine for the payload sled.

Moreso, if you merely accelerate the payload a little faster, to orbital velocity, then you only need a small engine to circularise the orbit at apogee.

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