NASA Space Elevator Feasibility: NASA Announces New Launch Vehicle and CEV

[LunchBox]

What I wish is that lots of money would be dumped into a ribbon-type space elevator or a space fountain That's the real way to get to space cheaply and safely.

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

Cheers...

 

[SkepticJ]

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

Cheers...

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.

 

[enigma]

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.

 

[SkepticJ]

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.

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 http://quest.arc.nasa.gov/aero/wright/background/otto.jpg

 

[enigma]

Would you please give links etc. to such data?

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.

 

[SkepticJ]

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.

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.

 

[Ki Man]

20 mile high elevator.

what the heck is the top of it going to lead to? what's the point? is it going to be like the cn tower but blown up in size 20x? threes no point in going up if there's 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 going to 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.

 

[SkepticJ]

20 mile high elevator.

what the heck is the top of it going to lead to? what's the point? is it going to be like the cn tower but blown up in size 20x? threes no point in going up if there's 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 going to 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.

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

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? Arguments from Incredulity aren't valid arguments.

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

 

[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 going to do when its up there? were not going to 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 going to 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 there's no point in an elevator in the first place. and there's always the danger of being hit by lowflying aircraft AND satalites. if a b-29 hit the empire state building, somethings going to hit this baby sometime.

 

[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!)

 

[SkepticJ]

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 going to do when its up there? were not going to 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 going to 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 there's no point in an elevator in the first place. and there's always the danger of being hit by lowflying aircraft AND satalites. if a b-29 hit the empire state building, somethings going to hit this baby sometime.

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.

 

[Ki Man]

What I wish is that lots of money would be dumped into a ribbon-type space elevator or a space fountain That's the real way to get to space cheaply and safely.

since when is building an elevator many many miles high cheap

I never said its impossible, but there's 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 going to hear anything from me for a while until i get better at speaking.

 

[SkepticJ]

since when is building an elevator many many miles high cheap

I never said its impossible, but there's 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 going to hear anything from me for a while until i get better at speaking.

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.

 

[Ki Man]

the quote i was referring 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 into begin with.

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

 

[enigma]

cheaper like the shuttle is cheaper?

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

 

[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.

 

[enigma]

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.

 

[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 into 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!

I could go on... but... well... [URL=[URL=[PLAIN]http://groups.msn.com/_Secure/0TwDtAuIY!vxCf!LqsXBkoLXuJ0MS!*SqpH8VwXdtWpv4XVx7NBucxjJh2umHmm2c83SmaHcre6HAhkr33eDqi82b2CUpiYc1WH7nGFtSe74!5sVUE*1!vg/beating-a-dead-horse.gif[/URL] pretty much sums up what I'm already doing.

Cheers...

 

[FredGarvin]

Ah, but this wouldn't be a problem to a space fountain which I linked.

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.

 

[enigma]

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.

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

Wikipedia knows all

 

[Ki Man]

i'm thinking more like, large version of spaceship one, maybe not as huge as i said with the 747

 

[SkepticJ]

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 into 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!

I could go on... but... well... [URL=[URL=[PLAIN]http://groups.msn.com/_Secure/0TwDtAuIY!vxCf!LqsXBkoLXuJ0MS!*SqpH8VwXdtWpv4XVx7NBucxjJh2umHmm2c83SmaHcre6HAhkr33eDqi82b2CUpiYc1WH7nGFtSe74!5sVUE*1!vg/beating-a-dead-horse.gif[/URL] pretty much sums up what I'm already doing.

Cheers...

Yep, total crap. Those people at Lawrence Livermore National Laboratory are time wasting idiots; and so was Robert Lull Forward.

1. Amazing this can happen, since much of the tower is above atmosphere of any appreciable thickness. The thinner the air, less less the force of the wind per the wind's speed. Even if magnets of this size would be needed I see no problem. Particle accelerators, km in length, have been around longer than I have.
We know where the jet streams are. We could build it where the streams never go, if they'd be a problem.

2. From what? You'll have to explain in detail.

You lack the ability to read what the links I give say I see. You're "Oh, mass pellets being shot up, energy lost, debunked!" without even looking at the math these people did. Sloppy. So? If you think 2km per sec. gun velocity is current science fiction you'd be wrong. There are rail guns that can shoot spike-like rounds at 7+km per second already. IIRC the finned spike projectiles have a mass of about a kilogram. The rail gun is less than 20 meters long IIRC. Particle accelerators get particles, with mass, up to just below the speed of light, currently.

I'd rather you did, because your link doesn't come up for me.

 

[LunchBox]

Those people at Lawrence Livermore National Laboratory

...

(Psst... just because the people work for a place who's name ends in "national laboratory" doesn't mean they have a direct pipeline to the wisdom of the ages. In fact, they are just as likely to be wrong as anyone else... I know... I work with these people from time to time.)

1. Amazing this can happen

...

Isn't it? I've always found vibrations to be an interesting topic. The numbers were for comparison. Now, in the 'articles' you link, the authors stress how only a spindly, lightweight structure will be needed. Spindly, lightweight structures have extremely small bending (EI) stiffnesses. The Sears Tower is practically rigid compared with a 'space fountain' structure. Pick your favorite 'space fountain' design (as the articles you linked surprisingly had no structure sizing) and perform a sinusoidal gust loading along the height... I imagine the tip displacement value will astonish you.

2. From what? You'll have to explain in detail.

...

Ok... I'll explain. The gust loading will not be even over the side area of the structure facing the wind. This difference in loading along the windward face will create a torque on the structure. And spindly structures have even lower torsional (GJ) stiffnesses than bending stiffnesses.

You lack the ability to read what the links I give say I see.

No... they just fail to say anything useful...

You're "Oh, mass pellets being shot up, energy lost, debunked!" without even looking at the math these people did.

I'll assume you meant 'your' and not 'you are'. I saw no 'math' in your Wikipedia article and the only technical publication linked from there was on a 'launch loop', not a 'space fountain'. The wonderful catch-all in the Wikipedia article

but Roderick Hyde worked out all the engineering design details for a Space Fountain and showed that there were no show-stoppers.

really means that the problems were manageable within the scope of the universe we occupy, not that the problems were practically solvable, or that they were economically practical. I would ABSOLUTELY LOVE to see that analysis done by Roderick Hyde. If you have it, please send me a link or a pdf. Also, always remember Akin's Law of Spacecraft Design Number 17

So? If you think 2km per sec. gun velocity is current science fiction you'd be wrong. There are rail guns that can shoot spike-like rounds at 7+km per second already.

No... I didn't say that they were science fiction. In fact, I am a huge proponent of rail gun technology. As soon as it becomes economically feasible, I think the military should put those bad boys on EVERYTHING. However, what I was referring to was the atmospheric drag that will suck momentum from these projectiles. Not only that, but the projectiles will need to be ferromagnetic in order to be redirected at the top and bottom of the tower. The atmospheric drag on a projectile traveling at Mach 6+ will cause tremendous heating and could exceed the Curie temperature of the material making it no longer ferromagnetic. Also, the velocity of the returning projectiles will will be limited by the terminal velocity of the projectile profile. All these losses will add up to necessitate a tremendous energy expenditure to bring the projectiles back up to speed at the bottom of the 'space fountain'.

Now look, maybe I started a little harsh, but I'm sick and tired of people thinking you can get to space easily by climbing successively taller trees. My goal it not to stifle creativity... far from it. However, I think a little realism and practicality needs to be brought into every discussion. Oh and I was serious about wanting to see that analysis...

Cheers...

 

[russ_watters]

i'm thinking more like, large version of spaceship one, maybe not as huge as i said with the 747

The important thing to know about SpaceShip One is that it is not a space ship. It's just the most expensive amusement park ride ever created. Ok, so I'm not sure if there is a formal definition of the term, but my point is that Spaceship One does not come anywhere close to achieving orbit, which is what it must be able to do have any real use. So scaling it up would accomplish little of value.

Also, while SpaceShip One had a number of unique design features, the overall concept is an old one, the same as the X-15. The performance is somewhat less than what the X-15 achieved 50 years ago.

 

[DaveC426913]

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

I was unaware that there was "good" physics and "bad" physics.
As SkepticJ says: "Space fountains don't violate known physics."

Perhaps what you meant was that there are a number of technical hurdles to overcome. To which I think most of us agree. We only disagree on how much, how long and how costly.

since when is building an elevator many many miles high cheap

When? Why, by trip #2!

The whole point of these devices is that, utterly unlike any kind of rocket, you only put out the expense once, not every time.

 

[Danger]

enigma, re: your technical problems mentioned in post #5, would any or all of these also apply to a skyhook?

 

[SkepticJ]

...

(Psst... just because the people work for a place who's name ends in "national laboratory" doesn't mean they have a direct pipeline to the wisdom of the ages. In fact, they are just as likely to be wrong as anyone else... I know... I work with these people from time to time.)

...

Isn't it? I've always found vibrations to be an interesting topic. The numbers were for comparison. Now, in the 'articles' you link, the authors stress how only a spindly, lightweight structure will be needed. Spindly, lightweight structures have extremely small bending (EI) stiffnesses. The Sears Tower is practically rigid compared with a 'space fountain' structure. Pick your favorite 'space fountain' design (as the articles you linked surprisingly had no structure sizing) and perform a sinusoidal gust loading along the height... I imagine the tip displacement value will astonish you.

...

Ok... I'll explain. The gust loading will not be even over the side area of the structure facing the wind. This difference in loading along the windward face will create a torque on the structure. And spindly structures have even lower torsional (GJ) stiffnesses than bending stiffnesses.



No... they just fail to say anything useful...



I'll assume you meant 'your' and not 'you are'. I saw no 'math' in your Wikipedia article and the only technical publication linked from there was on a 'launch loop', not a 'space fountain'. The wonderful catch-all in the Wikipedia article really means that the problems were manageable within the scope of the universe we occupy, not that the problems were practically solvable, or that they were economically practical. I would ABSOLUTELY LOVE to see that analysis done by Roderick Hyde. If you have it, please send me a link or a pdf. Also, always remember Akin's Law of Spacecraft Design Number 17



No... I didn't say that they were science fiction. In fact, I am a huge proponent of rail gun technology. As soon as it becomes economically feasible, I think the military should put those bad boys on EVERYTHING. However, what I was referring to was the atmospheric drag that will suck momentum from these projectiles. Not only that, but the projectiles will need to be ferromagnetic in order to be redirected at the top and bottom of the tower. The atmospheric drag on a projectile traveling at Mach 6+ will cause tremendous heating and could exceed the Curie temperature of the material making it no longer ferromagnetic. Also, the velocity of the returning projectiles will will be limited by the terminal velocity of the projectile profile. All these losses will add up to necessitate a tremendous energy expenditure to bring the projectiles back up to speed at the bottom of the 'space fountain'.

Now look, maybe I started a little harsh, but I'm sick and tired of people thinking you can get to space easily by climbing successively taller trees. My goal it not to stifle creativity... far from it. However, I think a little realism and practicality needs to be brought into every discussion. Oh and I was serious about wanting to see that analysis...

Cheers...

Government Labs don't usually write stuff that is BS though. If it involves physics breaking stuff they have to show that physics, as it was understood up to that point, isn't correct. This, as far as I know, hasn't happened yet.

Right.

That's because it's a general concept. The towers could be whatever diameter, mass etc. is wanted/needed.

That's better.

Neither did your non-functioning "link". You might want to go back and fix that, because I can't be privy to the "debunking" of "crap" concept space fountains.

It's very ironic your critiquing of my typing flaw when you, while using a sock puppet, made this typing error: "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."
I think you and Ki Man are one and the same because of these two quotes:

"having my but scratched by a satalite guided laser"-Ki Man

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

Even if you're not one and the same, this should do: "Also, the velocity of the returning projectiles will will be limited by..."

If you're going to debate with me, do it with one account, mmmmkay?

If you're not one and the same person, a little advice, don't correct people's typing in a debate and in a pissy manner. Especially in a debate with someone that is anal retentive about doing correct spelling in his own work.
Be nice to me and I'll be nice to you in return.

Vacuum pipes, which the streams travel through, make this a non-issue. No air, no drag. *sigh* I guess I'll have to say everything that the linked papers say before you get it. Why, oh, why did I waste my time? What's the difference between this "manageable within the scope of the universe we occupy" and this "not that the problems were practically solvable"? http://www.answers.com/practical&r=67 seems to fit both. Economic is another matter though.

I'll probably have to read through Dr. Robert Forward's Indistinguishable from Magic to find the calculations/analysis. Said book has a lot of information on Space Fountains in it; plus other stuff.

 

[Ki Man]

meh, ignore what i said before i was drunk or something (not literally)

if this is about 200 miles high, how quickly will we be traveling to get up this thing. is it going to be like a 5 hour take your time kind of thing as you go straight up into the atmosphere or is it going to be somekind of accelerated trip to make you get there quickly. i understand what's backing this up now, i can have a concept design done some time this week.

how fast are we talking? how high is it going to be (estimate) and how big is the elevator going to have to be (like how wide is it going to need to be at most and what kind of things are going to need to be carried up by the elevator carts.)?

and no this is not lunchbox! i doubt he is a 13 year old living in south california. i just thought using his comment in my own would be a good idea. outside of the forum i am not associated with him.

i am not him. he's not smart enough to be me lol

okay there ARE similarities in our posts but if a mod checked out our IP adresses he'd see that they are different (unless lunchbox is really my sister which i really really doubt). can i get a mods help here.

 

[hitssquad]

Space-elevator at Yahoo

if this is about 200 miles high

It goes to geostationary orbit, which is about 22,200 miles high.

how quickly will we be traveling to get up this thing.

There exists a variety of space-elevator conceptions. There are speculation links at the bottom of this page...
en.wikipedia.org/wiki/Space_elevator#See_also

...and a good space-elevator discussion group here:
groups.yahoo.com/group/space-elevator

 

[enigma]

Government Labs don't usually write stuff that is BS though.

Usually, no. Occasionally? Yes. Just because you have PhD after your name does not mean you can't make mistakes or overlook certain aspects of a problem. That's why designs are always done in groups. In this case, the idea has so many critical engineering details neglected as to be worthless. Where is the report? All I've seen is a non-technical Wikipedia article.

Neither did your non-functioning "link". You might want to go back and fix that, because I can't be privy to the "debunking" of "crap" concept space fountains.

Link works fine for me. Links to the website of University of Maryland's Space Systems lab director Dr. Dave Akin. Law #17 states:

17. The fact that an analysis appears in print has no relationship to the likelihood of its being correct.

Something which is absolutely true. I have read many technical journals with blatant errors that got overlooked.

Even if you're not one and the same,

Lunchbox and Ki Man are not the same person.

Vacuum pipes, which the streams travel through, make this a non-issue. No air, no drag.

It is proposing a pump which drains the air (and keeps the air drained) out of a pipe _200 miles long_?!? Amazing what is trivially attainable when you just wave the magic "engineers can do anything... and easily" wand.

Steel is unable to sustain its own weight in the Earth's gravity field if it's on the order of 10 miles long. Stresses inside the structure due to the gravity loading will cause it to fail, even if it's being pushed up at the end. The failures would occur in the middle anyways.

Until I see an in-depth technical analysis which covers structure vibrations and stress analyses, I'm going to say it's not feasible as well, just from back-of-the-envelope calculations.

I guess I'll have to say everything that the linked papers say before you get it

I see a grand total of zero linked technical papers in this thread, or the one which I separated this discussion out of.

 

[hitssquad]

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

Ribbon-type space elevators do not need to be anchored on the equator. They can be anchored anywhere, including the poles.

 

[blimkie]

meh, ignore what i said before i was drunk or something (not literally)



how fast are we talking? how high is it going to be (estimate) and how big is the elevator going to have to be (like how wide is it going to need to be at most and what kind of things are going to need to be carried up by the elevator carts.)?

Ki man the space elevator is not an actualy elevator as u have in the CN tower empire state etc.
Its not gonne be built as if it were a massive cn tower reaching into space. Keyword "ribbons" made from carbon nano tubes its flexible.


IM NOT saying that it is 100% possible because i don't know all the complicated physics involved exceeding high school. The idea was for a spacecraft to latch onto the ribbon and drive itself into space at a slower velocity than rocket ships and supposedly be more safer. A company called lift port has smalled scale models suspended by balloons. The question is can they create one much larger and extend it into space.
I watched a small piece about it discovery channel last night and was quite suprised but beleives they can make this work by 2018. http://liftport.com/research1.php

 

[SkepticJ]

Ribbon-type space elevators do not need to be anchored on the equator. They can be anchored anywhere, including the poles.

Until the asteroid falls out of the sky blowing the Arctic ice sheet or Antarctica a new crater. It's the centripital force of the asteroid on the end that holds the ribbon tight. Other places as well have a problem, because geosynchronous orbit can only happen above the equator.

 

[SkepticJ]

Usually, no. Occasionally? Yes. Just because you have PhD after your name does not mean you can't make mistakes or overlook certain aspects of a problem. That's why designs are always done in groups. In this case, the idea has so many critical engineering details neglected as to be worthless. Where is the report? All I've seen is a non-technical Wikipedia article.



Link works fine for me. Links to the website of University of Maryland's Space Systems lab director Dr. Dave Akin. Law #17 states:...

It is proposing a pump which drains the air (and keeps the air drained) out of a pipe _200 miles long_?!? Amazing what is trivially attainable when you just wave the magic "engineers can do anything... and easily" wand.

Good point. I'll see if I can find that technical paper. Google searches aren't finding anything, but I'll keep trying to get it.

No, not that link; the link in post #18's bottom. It doesn't work for me.

Shouldn't be hard at all. For one thing, the pipe could be very narrow in diameter; which means less air inside. For another thing, the vacuum pump isn't fighting against gravity. If you had a pipe as tall as this, connected even just a small vacuum pump, it could eventually suck all the air out. "Eventually" wouldn't do, so something like a 777's jet engine powered vacuum pump would do nicely. It'd probably be able to suck the pipe to a vacuum in several hours to a day. Since the top of the pipe is above the atmosphere no more, or very, very little and slowly, will get in again that way. Going through the pipe material itself, hydrogen and helium are the only gases I know of that can squeeze through metal. There's not much of either gas in Earth's atmosphere, because they rise to the top of the atmosphere and are blown away by Sol's solar wind.

 

[hitssquad]

because geosynchronous orbit can only happen above the equator.

It can happen anywhere, if you have a ribbon. If the ribbon were anchored at a pole, it would not align with Earth's axis.

 

[SkepticJ]

Ok, idea I had. Made a "spacecone" composed of fountain towers at angles. Kind of like a giant teepee tent. Wind blows against towers and the other towers on the other side take the sway load using their compressive strength. I wonder if they'll name the idea after me?

 

[hitssquad]

the other towers on the other side take the sway load using their compressive strength.

I.e., the Eiffel Tower.

google.com/search?q=eiffel+tower+compressive+strength

 

[blimkie]

Yea or similar to the i giant pyramid hotel they plan to build sumwhere in japan or sum asian place out of nano tubes. saw it on extreme engineering. the ideas has been thought of


/\
/\/\
/\/\/\

 

[Ki Man]

yes, the physics involved here is too advanced for me, but i still understand all of the concepts of the building and concepts must happen before details can be laid.

i saw the episode your talking about. the building was like this

---/\
--/\/\
-/\/\/\

but diferent. what about a pyramid with a tower on top and then from the top of the tower comes the ribbon, the ribbon goes up and is tethered at the end by a space station where spacecraft are docked and waiting to be taken to the moon or something

something like this: (ignore these little lines going sideways like this -)

---[spaceport]
------[ ]
------\ /
-------lll
-------lll (ribbon)
-------lll
-------lll
-------lll
------llllllll
------llllllll (tower)
------llllllll
------llllllll
-----/\/\/\
----/\/\/\/\ (pyramid)
---/\/\/\/\/\
--/\/\/\/\/\/\
-/\/\/\/\/\/\/\
/\/\/\/\/\/\/\/\

 

[blimkie]

yea i made mine like that but when i posted it it all mvoed to the left lol

 

[blimkie]

i think it be easiest to have acess to the ribbon as close to the ground that way heavy space crafts done have to be lifted up heghts exceleing skyscrapers to be attached to the ribbon. My suggestion woul be to have and anchor buried underground so teh ribbon is ground level. Then build any structures such as mission control around it but leavy plenty of space around the ribbon.

 

[Ki Man]

buried anchor would work very well.

when the time comes for us to pick a space station before we finish the las mile or so, do you think ISS would work or would we have to build a whole new station

i say build a new one

 

[Kenneth Mann]

Ribbon-type space elevators do not need to be anchored on the equator. They can be anchored anywhere, including the poles.

You are not correct here. What would hold the system up (keep it all from falling to the ground) is the orbital impetus. That is not sufficient, however. Anywhere other than in a synchronous orbit, the 'ribbon' would wrap itself around the Earth like a maypole, and this means that it must be in a synchronous orbit. To complicate matters, however is the tremendous weight of the assembly that would be 'hanging down' from that orbit. To compensate, an equal weight would have to pull 'up' from that synchronous orbit point, extending it a great deal upward, beyond synchronous. Then, that lower part would attempt to run itself ahead of rest if it is not anchored to the ground (ie, the lower the orbit of any part, the faster it will travel).

Then, the complications are just so great as to stagger the mind. The part that extends below synchronous wants to pull itself ahead in orbit, so even if it is anchored below, the lateral distortion forces would be incredible. Next, the weight of that part hanging down would be enormous. Not even the much ballyhooed nanotube structures would have anywhere the near the tensile strength to handle the needs of a structure this tall hanging down (I don't believe; --- maybe some super-super-super-nanotubes of the distant future will be able to). Then, there is the equal "weight" of the counterbalancing part pulling up, and its 'lateral backward' pull in orbit on the assembly. All in all, I just don't see it being done in the near future. Finally, I just don't see how you would handle the tendency of the upper part (beyond synchronous) to wrap itself around. You can't anchor that part.

KM

 

[blimkie]

Well KI Man, I also think a new station would be handy, i say on the moon. The prupose of building the space staion on the moon is to conserve fuel because so much is burned escaping Earth's gravity, however a vast amounts of fuel would still have to be burned to get the crafts to the station. The space elevator would further contribute to decreasning the amount of fuel we burn. It would also allow an object to travel to space much safer.

 

[Danger]

Well KI Man, I also think a new station would be handy, i say on the moon.

I have an idea here (or, more correctly, my 14 beers and I have an idea). Let's just solidly anchor a bucky cable between Earth and the moon. Since the moon is already tide-locked with one face toward us, it's only the orbital period that presents a problem. Linking them with a non-elastic cable will eventually slow down the moon's orbital period, and to some extent the Earth's rotational one, until the moon is geosynchronous. Then all we have to do is climb up the cable like monkeys in space suits.

 

[JesseM]

Then, the complications are just so great as to stagger the mind. The part that extends below synchronous wants to pull itself ahead in orbit, so even if it is anchored below, the lateral distortion forces would be incredible. Next, the weight of that part hanging down would be enormous. Not even the much ballyhooed nanotube structures would have anywhere the near the tensile strength to handle the needs of a structure this tall hanging down (I don't believe; --- maybe some super-super-super-nanotubes of the distant future will be able to). Then, there is the equal "weight" of the counterbalancing part pulling up, and its 'lateral backward' pull in orbit on the assembly. All in all, I just don't see it being done in the near future. Finally, I just don't see how you would handle the tendency of the upper part (beyond synchronous) to wrap itself around. You can't anchor that part.

Have you analyzed the engineering details of proposed space elevators to see if these issues are addressed? If not, you might want to check out something like the book by Bradley Edwards, which apparently contains a lot of detailed analysis of such engineering issues. Here's a collection of references, some available online:

http://www.spaceelevator.com/docs/

Included are two articles written by Bradley Edwards for NASA:

http://www.spaceelevator.com/docs/472Edwards.pdf
http://www.spaceelevator.com/docs/521Edwards.pdf

The second article indicates they've done a lot of calculations and simulations to check the stability of the space elevator:

14
Ribbon Dynamics
The dynamics of the elevator, in general, are fairly straightforward but to ensure proper operation we need to examine the details of the elevator dynamics.

In 1975, Jerome Pearson published a technical article that included the a discussion on the natural frequency of the space elevator. Pearson found that the natural frequency depended on the taper ratio of the cable and in some cases would be near the critical 12 and 24 hour periods that could be problematic. Pearson also stated an ugly equation for calculating the shape of the cable as a function of the material strength, planetary mass, and planetary rotation speed.

We have taken Pearson’s original equation and attempted to simplify it into a more usable and intuitive form. However, this equation does not simplify well and like Pearson we have resorted to an analytical solution. In our case, however, we have ready access to spreadsheets that easily handle these types of calculations. We have composed a set of spreadsheets that produce ribbon profiles, tension levels, linear velocities, counterweight mass and total system mass. This spreadsheet is designed to handle different planetary bodies, rotation rates and applications.

Another spreadsheet we have composed is similar but for elevators with their anchors located off the equator. In this case the ribbon is found to sag toward the equatorial plane but remain entirely on the side as the anchor. This sag in the ribbon is due to the non-axial pull of gravity on the ribbon. The magnitude of the sag depends on the planetary rotation, planetary gravity and mass to tension ratio of the ribbon. In the case of a Martian cable, where anchoring the cable off the equator would allow it to avoid the moons this calculation is critically important. In the Martian case the cable extends parallel to the equatorial plane with only a 3 km sag back toward the equatorial plane when the cable is moved 900 km from the equator. This simple reanchoring of the cable would allow us to avoid any difficulties with the Martian moons.

What these and the dynamics work discussed below imply is that from a system stability and operations it is possible to move the anchor tens of degrees off of the equator if other factors (weather) permit.

In addition to the spreadsheets that we have assembled, David Lang has conducted computer simulations on the dynamics of the system. The code Lang is using was originally designed for modeling the ProSEDs experiment. Lang has modified it to examine the elevator scenario. The results from these simulations show that the elevator is dynamically stable for a large range of perturbations. The natural frequencies were found to be 7 hours for in-plane (orbital plane) oscillations and 24 hours for out-of-plan oscillations. The out-of-plane number is misleadinghowever. For any elevator or geosynchronous satellite a 24 hour period is found for the out-of plane because that simply implies an inclined orbit. For determining the stability, Lang gave the system various angular deviations, initial velocities and also quickly reeled in some length of the ribbon at the anchor. At some limit in each of these cases the elevator becomes unstable. What was found was that angles of tens of degrees were required to create a catastrophic failure. (The energy required to move the counterweight this far is equivalent to that required to lift 3000 loaded semi trailers kilometers into the air.) It was also found that reeling in 3000 km of ribbon in 6 hours will create a catastrophic failure. Each of these perturbations is well beyond any we expect to encounter. The events leading up to any of these are easily avoidable.

Lang also suggested that we consider a pulse type of movement for avoidance of orbital objects rather than a translational as we have been proposing. The difference is that in the pulse situation the anchor station is moved one kilometer and moved back to its starting position. This will send a wave up the ribbon to avoid an orbital object. The pulse will reflect off the counterweight and return to the anchor where an inverse pulse maneuver is conducted to eliminate the pulse. The result is a quiet system. In our proposal the anchor would be moved and remain there. This would send a long pulse that could oscillate up and down the ribbon for some time. Simultaneous pulses and a complex movement of the ribbon would result. This is a simplified explanation of a complex operation and response but the point is that there are operations that still need optimization.

Along with the computer simulations we have conducted some hardware tests of various ribbon designs and damage scenarios. The tests included several sets of ribbons with parallel and diagonal fibers composed of plastic fibers and epoxies or tape sandwiches. The ribbons ranged from two to four feet in length and were placed under high tension loads.

In the ribbon tests we found much of what was expected and predicted by our models. In situations where there is continuous rigid connection between adjacent axial fibers, aligned or diagonal, high stress points are created at the edges of the damaged area. These high stress points tend to be the starting point for zipper type tears and greatly reduce the optimal strength of the ribbon. On the contrary, ribbons with non-rigid interconnects between fibers had minimal stress points and yielded at high tensions and larger damage. A full description of the optimal ribbon design is found in our book. Similar tests are now being arranged at Rutgers to explore the degradation that might occur. We have also started to set up ribbons close to what will most likely be the final design.

 

[hitssquad]

The latitudes of space-elevator anchorage

Ribbon-type space elevators do not need to be anchored on the equator. They can be anchored anywhere, including the poles.

What would hold the system up (keep it all from falling to the ground) is the orbital impetus.

Yes.

Anywhere other than in a synchronous orbit, the 'ribbon' would wrap itself around the Earth like a maypole

Yes. That is why a synchronous orbit would be selected for the poles, just as for any other latitude at which ribbon-type space elevators might be anchored.

 

[FredGarvin]

It worrys me when a source that is being quoted makes basic mistakes. Since when is a resonant frequency measured in hours? That is obviously the period of a couple of the modes. I have a very hard time believing that something that long, that has to endure the weather would not have many, many more modes excited.

 

[LunchBox]

Yes. That is why a synchronous orbit would be selected for the poles, just as for any other latitude at which ribbon-type space elevators might be anchored.

All orbits MUST lie in a plane which intersects the center of mass of the massive body (in this case, the Earth). An object in orbit about the north pole must pass over the south pole (and vice versa). The ribbon connecting the other anchoring mass would be wrapped around the Earth due to the anchoring mass "orbiting" the Earth.

The same goes for any other latitude.

The reason a geoSTATIONARY (not geosynchronous) orbit works is that the orbital period of the minor mass (anchor) is equal to the rotational period of the major mass (Earth) and, since on the equator, the minor mass is always over the same point. Thus the equator is the only place a skyhook is astrodynamically feasible.

Cheers...

 

[hitssquad]

All orbits MUST lie in a plane which intersects the center of mass of the massive body

This is not the case for orbiting bodies which are tethered.
images.google.com/images?q=tetherball