# Space elevator feasibility; split from: NASA Announces New Launch Vehicle and CEV

1. Sep 21, 2005

### LunchBox

Yeah, they'll have those right after they have satellites that can scratch your ass with a laser beam from space.

Cheers...

2. Sep 21, 2005

### SkepticJ

While I admire your skepticism, you seem to have never heard of carbon nanotubes have you? They're already strong enough to create such a ribbon, give it a few decades. Remember, we'll never break the speed of sound, land on the moon or split the atom; don't be absurd.

3. Sep 22, 2005

### enigma

Staff Emeritus
I'm afraid Lunchbox is right on this one...

It's possible... (possibly), but anyone who says that building it is anything short of the most complicated engineering feat ever attempted has their head in the clouds and their pie in the sky.

Between grounding out the Van Allen Belts and the slightest gravitational, atmospheric, or solar pressure perturbations exciting 1047th natural mode of the ribbon and causing it to oscillate out of control... I just don't think it's possible in our lifetime, nor the lifetimes of our children or our children's children's children.

4. Sep 22, 2005

### SkepticJ

Would you please give links etc. to such data? I've seen "show stopping" problems(at least they appear to be before rebuttals are given) with space elevators before, and I'm not persuaded they aren't feasible yet. I'm not saying one will be built within thirty years, but not within my great great grandchildren's lives? Come on. For one thing I'm only twenty, and for another, in a smaller span of "grands" we've gone from this to this and this

5. Sep 23, 2005

### enigma

Staff Emeritus
A few semesters of stuctures vibrations courses is my only source. Damping out a string under tension with one fixed end and one free end will be damn near impossible.

There was a shuttle experiment where they extended wires a hundred meters or so radially and the current produced destroyed the experiment, and the shuttle wasn't even in the VA belt. A space elevator is thousands of kilometers long. Even if the ribbon is built strong enough to withstand the current, due to IXB, you'll get a time-varying tangential force on top of the floating string in tension model which now also needs to be damped out.

I did a bunch of research a few years back and read reports by David Smitherman at NASA which said that it will be feasible in the next century, but I am highly skeptical that his analysis was thorough.

Again, I'm the first person to say guffaw to anyone who says it will never happen... but I don't think this one will be attainable anytime soon.

6. Sep 25, 2005

### SkepticJ

Ah, but this wouldn't be a problem to a space fountain which I linked. A space fountain isn't under tension, it's under compression. It's held up using mass beams (steams of mass pellets shot out of an auto fire magnetic accelerator gun) Another advantage to space fountains is they need not be built on the equator. One could build one at the North Pole if they wanted to, it would be stupid and fuel wasting, but could be done. The best place for a space fountain would be at the equator, to give the cars traveling up it that added boost from the spin of the Earth; just like rockets make use of.

7. Sep 25, 2005

### Ki Man

20 mile high elevator.

what the heck is the top of it going to lead to? whats the point? is it gonna be like the cn tower but blown up in size 20x? threes no point in going up if theres nothing to do when your up there.

i feel sorry for the "astronaut" who has to be first to ride it.

not impossible idea but not very plausible. your gonna make a building/stucture partially leave the atmoshere while still tethered tot he ground.

maybe it can happen. right after pigs take over england and i can go around the world with the press of a button while having my but scratched by a satalite guided laser while being served fruit that came from our new martian neighbors.

8. Sep 25, 2005

### SkepticJ

One would think we could dispense with strawman arguments and engage critical thinking at a science forum. :yuck:

It'd be far taller than 20 miles. I space fountain could be 200 mi. high to provive service to low Earth orbit; or as high as you want to go. They have no limit in height. You should read up on them at the link I gave, or at this link before you strawman and mock them.
A "beanstalk" ribbon type elevator, which has the problem noted in this thread, would go up about 60,000 miles into the sky.

Oh I don't know, how about a space station or something? What do we sent those Russian craft or the Shuttle into space for?
The idea is that craft ride up into orbit and then detach from the elevator at the height they want to go to; or go on to the end.

Why? If mag lev rails went up the side of the space fountain tower the elevator car could reach the top in less than a few hours. The ribbon type's transit time might be up to a few weeks from bottom to top. As long as some good Led Zeppelin music was playing over the speakers, Internet link with the ground, TV beamed up and perhaps love mate(s) as well the ride up would be great.

This matters why? What, you're talking about making a metal tube soar through the air using metal "wings" and loud tube-like things with spinning "turbines" to propell them? Carry four-hundred people as well? At 30,000 ft.? At 600mph? Across an entire ocean on one tank of fuel? :rofl: Arguments from Incredulity aren't valid arguments.

*Sigh* I won't dignify this pile of BS hyperbole with a response longer than this.

Last edited: Sep 25, 2005
9. Sep 25, 2005

### Ki Man

thats different. planes have good physics backing them up. this is just... whoa.

think about it. even if we had a design that would stand the test of time, altitude, weather, and earthquakes, along with hunderds of other things, how the heck are we planning on building this thing? AND how much will this cost? AND what are we gonna do when its up there? were not gonna be able to leave what ever is at the top of the elevator in any way other than going back down the elevator. we're gonna be limited to spacewalks unless we have a spacecraft taken up there, but if we take a spacecraft up there its probably going to be using rocketsto get there so then theres no point in an elevator in the first place. and theres always the danger of being hit by lowflying aircraft AND satalites. if a b-29 hit the empire state building, somethings gonna hit this baby sometime.

10. Sep 25, 2005

### Intuitive

I remember reading about an article that a dirigible made of rigid nano tubes and if the area of displacement was as large as a football field, You could lift 800 lbs of mass, The Rigid dirigible was an evacuated Blimp and contain a football field size vacuum of displacement, You can could put more into space this way and it's reusable, If you have efficient vacuum pumps and a super material like nanotubes, If I had the money to make it I bet I could win some X prize, The rigid evacuated dirigible will seek an equal equalibrium of space.

If you can created a super hard vacuum in a rigid dirigible it would be pushed up to space.

I bet if we had a good engineer team work on this we could have a blimp in space, work out all the bugs. (Specific Gravity is our friend, Buddy up!)

11. Sep 25, 2005

### SkepticJ

Space fountains don't violate known physics. If they did I wouldn't suggest them as a possible way to space. If you want to keep talking about them it's best you actually read how they'd work at the links I gave.

Would you care to explain what negative effect altitude above sea level would have on metals? Ummm, I have; please don't be condescending with me. Read the links, they explain how they'd be made.
Can you read? I said the stuff that goes up detaches from the tower. Nothing is "stuck" any more than payloads are stuck to the Space Shuttle or other rockets that take them to orbit or beyond. If you're not going to stop being stupid with me I'm not going to spend time conversing with you any longer; your choice what happens.
No, the most energy use is getting from the ground up to orbit; which is what the elevator does. Once you're in orbit rockets can be much smaller to get where you want to go. Air space around such a tower would be as tight as the space around a government building. Idiots or terrorists would be shot down long before they could hit the tower. We have a thing called RADAR for tracking things in orbit. How do you think we can keep the ISS or Shuttle from impacting with objects? Because we know where they are. A tower won't be built in the orbital paths of satellites.
The B-29 that you speak of hit the Empire State Building in heavy fog, before the days of RADAR and it still didn't make the tower fall. Name a modern event where a plane hit a building by accident and you'd have a better point. Such a tower would, as a last resort, have guns similar to the missile defence guns on Navy ships that shred enemy missles into tiny, tiny bits several miles away. Such a tower could have missles, and would have protective ocean and aircraft that could take out threats.

12. Sep 25, 2005

### Ki Man

since when is building an elevator many many miles high cheap

I never said its impossible, but theres a whole lot of hurdles we need to jump before we can start taking this to the next level.

*sigh* everything i say always comes out wrong. i need to work on my charisma. your not gonna hear anything from me for a while until i get better at speaking.

Last edited: Sep 25, 2005
13. Sep 25, 2005

### SkepticJ

It's not cheap, at first. I don't know if you know this or not, but every time the US's Space Shuttle goes into orbit, the effort that went into that feat costs the tax paying public about 1,000,000,000 US Dollars. This breaks down to about $10,000 dollars per pound to get a payload into space. Why did Dennis Tito, the first space tourist, have to pay$20,000,000? Because of his weight and the weight of the air, water, food and fuel that was needed to keep him alive. Plus a tiny bit of profit to the Russians for their trouble, I guess. I'm all for NASA and the Russian's space program. In fact I wish they got about $0.05 per tax dollar instead of the$0.01 or less they get. During the Apollo program NASA got about \$0.04 per tax dollar, and we had missions to the effing moon! But I digress. A space elevator would cost a lot up front, but the cost after that would be very low; the level of low that would let you take a tourist trip to space, if millions of other people weren't on the waiting list cash in hand, that is.

Yes, there is things that need to be developed to make the idea even more economical. Such as higher temp superconductor materials to cut down on the energy lost as heat from slowing down the mass beams and speeding them up again. And better magnetic guns.
Talk to you again on Tuesday, have to go until then.

14. Sep 25, 2005

### Ki Man

the quote i was refering too said that the ribbon would be a cheap and safe alternative. safe, maybe. cheap? definitely not

money money money money

going to space costs billions in to begin with.

what about 2 or 3 stage jet/rocket aircraft. definitely cheaper, re-usable, and reasonable safe.

15. Sep 25, 2005

### enigma

Staff Emeritus
cheaper like the shuttle is cheaper?

Re-usable spacecraft are some of the most expensive things on the planet.

16. Sep 25, 2005

### Ki Man

cheaper as in a small craft being carried up on something kind of like a boeing 747 and then shooting off when its high enough, then entering another stage, wheich means it will take less than a giant red tank of fuel 300 feet large and 2 boosters to get up. just enough for an airliner and some small rockets.

17. Sep 26, 2005

### enigma

Staff Emeritus
So instead of having one single system to get to 7.75 kilometers per SECOND and 250 kilometers high, you propose that designing all of the interlinkages and safety systems so you can launch it from 0.25 kilometers per second and 10 kilometers up?

All that and you now need to size the rocket small enough to be able to be carried by a 747. I'm sorry... if it was more feasible to launch from a plane for larger rockets, they'd do it.

18. Sep 26, 2005

### LunchBox

I gots some numbers

I just tried to post this and my browser crapped out on me... f'ing FireFox... anywho... here it is in condensed form because I don't feel like retyping it all...

SkepticJ... your 'space fountain' is crap. Your grandchildren's grandchildren's grandchildren won't see it. Here's why:

1.) Bending. This thing will sway like a drunken frat whore at Mardi Gras. For comparison, the Sears Tower, at 1450 ft, sways an average of 6 in to either side. Comparing that ratio with the 656000 ft 'space fountain' yields a sway of 226 ft. Now, that's to BOTH SIDES. So the magnetic catch on the redirector needs to be 500 FEET IN DIAMETER! And that's for AVERAGE SWAY. This thing will also be cutting through the jet stream so that 226 ft mean sway is so conservative, W is telling it to back off.

2.) Torsion. Everything from 1.) applies. Oops... just increased the necessary magnetic catch diameter.

3.) Projectiles. These things will require a TREMENDOUS amount of energy just to get to the top with NO residual energy. Oh, and you need residual energy to keep the structure from falling down like a lightweight frat pledge at initiation. (Wow... two drunken references in an analysis... new record.) The amount of energy required just to get the projectile to the top is 2 MJ/kg... yes 2 MILLION Joules per kilogram. Even assuming you have a rail launcher that is 1 km long, that is a required initial velocity of 2 km/s. Oh, and all of those numbers are excluding aerodynamic drag which will be substantial on a projectile leaving an accelerator at SIX TIMES THE SPEED OF SOUND!

Cheers...

19. Sep 26, 2005

### FredGarvin

You provided no link that I can see. I am a huge skeptic of the elevator notion but I would like to see something on the fountain idea before I start with my views on the subject.

20. Sep 26, 2005

### enigma

Staff Emeritus
He did, but it got trimmed when I split the threads.

Wikipedia knows all