Slashdot Mirror
Continued Success for Space Elevator Tests
Jacki O writes "According to their Web site the Space Elevator company Lifport recently managed to get their platform and climbing robot to the mile-high mark over the Arizona desert." From the announcement: "A revolutionary way to send cargo into space, the LiftPort Space Elevator will consist of a carbon nanotube composite ribbon eventually stretching some 62,000 miles from earth to space. The LiftPort Space Elevator will be anchored to an offshore sea platform near the equator in the Pacific Ocean, and to a small man-made counterweight in space. Mechanical lifters are expected to move up and down the ribbon, carrying such items as people, satellites and solar power systems into space."
I stood outside my door this morning in Flagstaff, which is 6200 feet above the Arizona desert.
"Made up/misattributed quote that makes me look smart. I am on
The robot only made it around 1500 feet. The cable was a mile long.
...but it seems like the climber is the easy-ish part of a space elevator. If they were doing work with the carbon nanotubes, I'd be much more impressed.
Every year during my review, I just pray the words "slashdot.org" aren't mentioned.
A little progress is better than no progress.
-IOVAR Web Dev Platform
The article said that the platform (held up by baloons) at the end of the teather was a mile up. The climbing device reached 1500 feet, 500 feet further than previous attempts, but still quite a bit short of a mile.
I'm out of my mind right now, but feel free to leave a message.....
I think the theory for this method of transportation was disproved by Wile E Coyote a few years ago.
I've read Gunnm, these space elevators can only lead to a power struggle between the elites at the top of the tower and the service people at the bottom (with a few crafty middle men getting rich transporting the goods!) http://en.wikipedia.org/wiki/Battle_Angel/
#include "forums.h"
int main() {while (bollox) postcount++;}
I'm just wondering, won't these things become a lightning magnet? You say it can be grounded, but what happens when these things stretch into higher parts of the atmosphere with more ions flying around?
For those who have not experienced this particular pleasure: the obligatory Wikipedia reference.
Take a string, tie a rock to it and swing it around your head. Then you'll get the picture.
http://en.wikipedia.org/wiki/Space_elevator
A space bird.
Every year during my review, I just pray the words "slashdot.org" aren't mentioned.
The most common proposal is a tether, usually in the form of a cable or ribbon, that spans from the surface to a point beyond geosynchronous orbit. As the planet rotates, the inertia at the end of the tether counteracts gravity and keeps the tether taut. Vehicles can then climb the tether and escape the planet's gravity without the use of rockets. Such a structure could eventually permit delivery of great quantities of cargo and people to orbit, and at costs only a fraction of those associated with current means.
Seriously, what does the robot on, what type of power supply does the robot have? It only made it 1500' on a mile long cable. Is that because it's energy supply ran out? Science fiction writers usually say ground based "lasers" or "microwave transmitters" but is that more feasible than 62,000 miles of carbon nanotubing?
The platform, a proprietary system that the company has named "HALE" (High Altitude Long Endurance), was secured in place by an arrangement of high altitude balloons, which were also used to launch it
Uhm, how useful will this be when they try to extend the elevator outside the atmosphere? Presumably, they have alternative methods worked out for stabilizing the zero-gravity portions, but somehow, Space Elevator == balloons is not nearly as exciting as Space Elevator == really cool new future technology.
I'll be excited when I can take the Space Elevator up to my penthouse suite at Hotel LaGrange. Unless, of course, I look out and see there are freaking balloons still involved.
...sometimes, in order to hurt someone very badly, you have to tell that person terrible lies. - PA
The platform, a proprietary system that the company has named "HALE"
Oh come on, they're just asking for it.
It's useful in that objects can use it to climb up and out of the Earth's atmosphere and into orbit, thus saving in the exorbitant costs, financial and environmental, in using rockets. From orbit after escaping Earth's gravity, it's a much easier prospect to jet off to the moon. Although there's use in just sticking things in orbit, as well.
There was an article in Analog (WAAAAY back when) on the math behind space elevator cables, and they indicated that unless a material such as carbon fibers (nanotubes and the like weren't even on the horizon then) were developed to commercial viability then the required strength to weight ratio would make the cable waaay too wide at its halfway point.
Less is more.
Regardless of how many descriptions of a space elevator I read, I can not grasp a visual of the process. Anyone have a video of something like the post topic?
Bury me in mashed potatoes.
...won't it whiplash and kill people all over the world?
Mac OS X and Windows XP working side by side to fight back the night.
The centripetal force is what holds it down, not what holds it up. From an inertial frame of reference, there is no force that holds it up; that's simply a function of its own inertia. If you wish to use the Earth as your reference frame (as you are doing) you must invent a force, called a centrifugal force, to account for the fact that a spinning object is not an inertial reference frame.
I have seen the future, and it is inconvenient.
...when they extend that thing if the moon gets nervous?
The race isn't always to the swift... but that's the way to bet!
According to their Web site the Space Elevator company Lifport recently managed to get their platform and climbing robot to the mile-high mark over the Arizona desert.
In other news today, Denver-based Space Elevator company Black Shaft Industries have succeeded in achieving a height of 35 feet with their platform and climber, still easily besting their rivals Lifport. "We had a head start," acknowledges Chief Engineer, Michael Wesznick, "but our elevator didn't really need it. Plus, it has a cooler name." Wesznick went on to claim, that the elevator in question (named "Darth-Vator" to those of you who were wondering) will be the "father of all other space elevators", and, adding to this reporter's confustion, will at some point in the future "betray the Emperor to save it's son's life." Personally, I'm rooting for Lifport.
Perhaps the point is that the first mile is significantly more difficult than the next 61,999?
No. 62 miles is the completely arbitrary definition of "space", but a space elevator that ended at that altitude would simply fall back down. By necessity, the center of mass (radially from the surface of the Earth) must be at or near geosynchronous orbit, so it naturally remains centered over its ground anchor. Geosynchronous orbit is at 22,241 miles above sea level. So, by gradually tapering the cable and extending it past GEO, the center of mass ends up there. Alternatively, you can have a large mass like a captured asteroid or something as an anchor just on the far side of GEO, although you should also have some counterweights you can move around on the cable to keep the center of mass in the right place as a load moves up from the surface. Additionally, keeping the center of mass just a little bit further out that necessary ensures that the space elevator will have just enough tension to keep it taut, giving the climbers an easier job.
Why don't we just build a 500 mile high pyramid of some description? And maybe run a ramp up it, and a pulley system maybe so we can use very simple earthbound techniques to get projectiles to an incredible speed before liftoff? Alternately, its surely easier and cheaper to get a launch from 500 miles up, or put the tail end of a space elevator there. And we could do it with existing technology easily. Its like the question, if there were stairs going to the moon, could you walk it... the answer to that one is yes.
What he can't kill, he has sex on. Trent.
there would be plenty of time to recover and string a new tether.
What I have always wondered is if anyone has calculated how much the Earth's rotation is expected to slow down once we start sending mass up that thing. You know, like the ice skater who sticks her arms out to slow down and pulls them in to speed up? There's no such thing as a free ride, and the energy "savings" will eventually become apparent, it will have come from the Earth's angular momentum. I wonder what climate trouble we will have then.
Seven puppies were harmed during the making of this post.
and shoot laser beams out of your head that powers the robot...
and have safety procedures in place in case the string breaks, and the robot comes plummeting towards your head...
and have the multinational population living on the surface of your head come to some agreement about who's going to finance, maintain, and operate the thing...
> Perhaps the point is that the first mile is
> significantly more difficult than the next 61,999?
Er...except it's not. As you leave the atmosphere there's temperature extremes...radiation...vacuum. Not to mention every mile you extend the elevator increases the strain the structure must support. The first mile is the *easiest*.
Chris Mattern
Do the maths: taking the earth as 6,000,000m across and an average density of 2t/m^3:
Volume ~ 4/3 * 3 * (3,000,000)^3 ~ 115,000,000,000,000,000,000 m^3
Mass ~2xvolume tons: ~300,000,000,000,000,000,000 t
To take a billionth part out would be 300 billion tons.
Much of a problem?
Only another 99.99954% of the way to go! . Wohooo!
Free Software: Like love, it grows best when given away.
But who knows, maybe they do mean 62,000 miles? I thought the elevator's main purpose was to get things in and out of just the atmosphere, as to avoid all the problems with expensive and dangerous rocket launches and dangerous re-entries.
We don't use rocket to get above the atmosphere. Planes can pretty much do that. Balloons can (and regularly do) do that. That's the easy part.
We use rockets to get velocity, because you need a ridiculous velocity in order to actually orbit the Earth at a low height.
You do not, however, need a ridiculous velocity in order to orbit at a very, very high height. At geosynchronous orbit, you need no velocity, because you've already got the speed from the Earth's rotation.
So yes, they do mean 62,000 miles (100,000 km). And the benefits you get from a cable like that are insane. Costs/pound to launch things into space become negligible. Transit to the Moon becomes cheap and fast, because the end of the cable is actually moving faster than orbital velocity.
In fact, if you climbed all the way to the end of the cable, and let go with good timing, you'd end up past Jupiter (and on a direct trajectory, too, no mucking about in Lagrange points).
Yes, it's moderately insane. Yes, it's ridiculously difficult. But it would also end up being one of the biggest changes in human industry that has ever occurred. Space solar power plants beaming down power becomes feasible. Large-scale structures built in space become easy.
Plus, once we get the technology, we can build them on other planets as well. The Moon. Mars. It basically eliminates almost all of the serious difficulties of space flight.
While traveling to the moon will be easier you have not escaped from the earths gravity well at 62000 miles.
GENERATION 27: The first time you see this, copy it into your sig on any forum and add 1 to the generation.
There are other ways to get into space without extending a strucuture beyond geosynchronous orbit. Check out launch loop and this wikipedia page.
By necessity, the center of mass (radially from the surface of the Earth) must be at or near geosynchronous orbit, so it naturally remains centered over its ground anchor
For the simple case, yes. But (IIRC) Robert Forward proposed a modified concept that utilized solar sails to stabalize the orbit and allow for them to be in other orbits. Or it may have just allowed for non-equatorial placement, or both -- I don't recall exactly and I'm certainly not a rocket scientist/orbital mechanics expert.
Hate to reply to myself, but when you have an idea... Eh you could even put a couple of hundred pulleys going up one side, with a couple of nuclear power stations buried in there to power them (and internal elevators going up and down, as well as any other power requirements). Surely you could reach escape velocity with ease and en masse by using very cost effective nuclear power like this... and also it could be based in a sea somewhere, so returning vessels could splash down nearby. Now that would be a serious spaceport! :D And all readily doable and not making the greens shriek or anything (except for a 500 mile by 300 mile strip of ocean that we weren't using anyway :D). Or if that doesn't sit right, the equatorial third world nation of choice would be more than happy to make itself richer than America and Europe combined by hosting the world's first true spaceport...
What he can't kill, he has sex on. Trent.
Really? Are you sure? Can you build a bearing for a 20-cm wheel that will be able to turn 500 million times with zero chance of failure? And can you do it lightly? And in vacuum?
While we don't have the ribbon yet, we don't have the climber, and we don't have the power delivery system either. That's why it's called inventing. They're doing something that hasn't been done before.
And when you've got multiple independent difficult problems, you might as well work on all of them at once. Which they are doing.
Go and read the talks on building the climber at the last space elevator conference before you call it "trivial".
I remember seeing an article (don't remember if online or a periodical) that said essentially that it would depend where the break happens. The stuff high up will burn on reentry and the stuff way down would wrap around earth very slowly, kinda like a leaf falling down. The counterweight would either escape earth or go into a higher orbit but moment would be conserved. I don't think a nuke would do much to it. More than likely an attach at the anchor point on earth or an attack on the strand itself is what would happen. Then there is the problem of all this junk that is in orbit between earth and the counterweight that would also like to snap the strand. Some kind of protection would have to be developed. Once one strand is up then redundancy can be built in by putting even more strands. Safety wise, the most dangerous object was the elevator cabin itself since it would be bulkier.
Does the firm have any ideas on how to avoid tremendous death and destruction if this immensely long cable were to fall to the Earth, possibly hitting certain areas twice as badly if it were long enough to wrap more than once around?
Yes. They're going to deploy a massive cushion around the Earth, consisting of a total of about 5000 trillion metric tons of gas. Roughly 78% will be nitrogen, and 21% will be oxygen.
If the cable breaks, the lower half will encounter this cushion at extremely high velocities, ripping it apart and causing it to flutter harmlessly to the ground.
No news about whether or not they'll patent the idea.
A guy gets on at the bottom and punches all the buttons. For 100,000 km your're thinking, "asshole!"
Give a man a fish and you have fed him for today. Teach a man to fish, and he'll say "WHERE'S MY FISH, YOU IDIOT?"
Don't mock the Society for the Conservation of Angular Momentum. It's a real problem and could lead to the heat death of the Universe if it isn't taken seriously, and soon.
The point is that the cable is by far the hardest part. We aren't even close. When we are 75% of the way to producing an adequate cable we can start the other parts. I bet we would still finish those other components before the cable is ready.
It's just a bit silly really... like building the lunar lander for Apollo but having boosters no larger than a bottle rocket.
Get closer to the Saturn V THEN build the lander!
It will depend on where it breaks. Cut it at the counterweight and it will wrap itself around the earth pretty fast. The top will burn on re-entry, the bottom would be going so slow that it will be easy to get out of its way and even then it would no cause much damage, kinda like falling leafs since it is so light and has such a big section. You cut it at the base (on earth) and it will jump up by whatever tension it had at the bottom and if it goes high enough from the dense bottom part of the atmosphere then it may be possible to reattach it. If not it just may end up as a whipping mass but still with its CG in geostationary orbit. Cut it anywhere else and you get a mix. The stuff over the cut will go higher based on how much tension was at that point, and the stuff under will fall. It would make a VERY tempting target given the amount of money that would go into it and how little you'd need to make all that dissapear.
Sorry, no. There is no such thing as centrifugal force, period. It's a convenient construct for laymen to think of things, and that's it.
Your strange example of tar is pretty easy to explain. When a car is in the process of a turn, it has forward inertia. As the law states, "an object in motion tends to stay in motion", but the action of the tires and their friction with the pavement counteracts this tendency, thus the car turns instead of continuing straight instead of running off the road. Over time, the asphalt deforms due to this frictional force (again, caused by the forward inertia of the cars).
Thanks for visiting the site. Our provider went berserk at the load and downed the entire kit and kaboodle. We are working on the issue (our CMS is to blame) and should return to service Real Soon Now.
Slashdot. Such a mixed blessing.
Display some adaptability.
A space elevator is theoretically feasible, but the challenges are far from trivial. I laugh at people who suggest one can be built starting today for $10 billion. Some of the estimates I've heard put the cost of developing all the technology for and building the first elevator at several $trillion, or equivalent to the federal government's entire annual budget. Of course, if we ever get one up, subsequent elevators are far cheaper.
Don't laugh. Building one today is quite impossible, of course, because we haven't yet developed the technology. But it could be feasible in ten years if we worked hard enough at it.
For comparison, look at the manned space program. JFK proclaimed the US would put a man on the moon before the decade (60's) was over. That was in 62 or 63. Armstrong set foot on the moon in 69 IIRC. The technology didn't exist when JFK made his speech, but with the enormous amount of funding the USA put into the space program after that, it was all developed on a very fast timescale.
If the US (and better yet, some partner countries) put forth the enormous funding necessary now like was done in the 60's, I don't see why a space elevator being constructed by 2015 couldn't be a reality.
Um, you can go to infinity and not escape the Earth's gravity well.
m l). If you just want to go to the moon you're going to want to cast off from the cable at a significantly lower altitude, otherwise you're going to make a BIG crater.
The critical factor is how fast you're going in relation to how hard gravity is pulling on you. When you're in geosynchronous orbit you're moving fast enough to stay forever at the same height. If you're HIGHER than geosynch, but still moving at the same speed (1 rotation / 24 hours) you're going to drift AWAY from Earth if you let go. If your cable is long enough you can go a LONG way away. A 62,000 mile cable is more than enough to go to Jupiter (http://www.isr.us/Downloads/niac_pdf/chapter7.ht
I don't deny that it may be possible to build a space elevator in 10 years if we start throwing money at it like crazy, but developing the technology will be expensive. I seem to remember reading somewhere that the amount of money invested in the manned space program from Mercury up through Apollo 11 was around $100 billion, in 1960's dollars. I would classify this effort on the same level. We've seriously never done something like this before. Goddard launched his first liquid fueled rockets around the 1900's. I don't really know whether to say our current progress is on par with his, 60-70 years before we walked on the moon, or closer to that in the 1960's when Kennedy declared his vision, less than 10 years before it happened. Meanwhile however, Liftport is operating on a few million dollars a year, at best, and CNT companies a little bit more.
Other facts about geostationary orbits:
Other geostationary orbits are not a problem... there are however many other obits that COULD intersect with the cable though.
Have you thought for yourself today?
IAARRS (I am a retired rocket scientist, and have participated in a NASA
Space Elevator workshop, and been on a science panel with one of the Liftport
guys - I guess that makes me a relative expert)
A tower going up from the ground meeting a cable coming down from orbit is
more efficent than a cable going all the way to the ground, if, and this is
important, the strength of the cable is substantially less than the depth
of the earth's gravity well.
Here's why: As you build a longer cable or a taller column of constant area
under gravity, the stress gets higher. In a column the maximum stress is at
the bottom, and in a cable it is at the top. Eventually you exceed the
strength of the material.
The Earth's gravity well is equal to one gee times the radius of the planet
= 6,378 km. A space elevator is centered at GEO, which is 97% of the way out
of the Earth's gravity well, so we need to span 6,167 km at one gee.
The strongest readily available carbon fiber that is not made of nanotubes
is about 1 million psi in strength. It has a density of 0.067 lb/in^3, so
if you had a cable 15 million inches long under one gee, it would be at the
limit of it's strength. 15 megainches = 381 km, which is a factor of 15
below what we need.
You can build towers or cables longer than the strength limit if you make
them progressively wider to keep the stress below the limit of the material.
Each 15 inches of length in the cable above adds one millionth to the stress,
therefore the area has to increase by one millionth. Over a 381 km length,
the area of the cable increases by a factor of e (2.718...). This length,
found by dividing strength by the density of the material, is called the
scale length. If you have 16.2 scale length to cover (6167/381), your
cable area increases by e^16.2 = ~10 million.
A graphite/epoxy composite is needed for a tower. Bare fibers are okay in
tension, but you need to stiffen them for a compression structure. Typically
using the same fibers, the composite will be 30% as strong in compression as
the bare fibers are in tension. Now assume you build a tower up and a cable
down with the same area ratios from bottom to top. The tower's scale height
is 114 km, so the combined scale heights for the tower + cable = 495 km.
Now you need 6167/495 = 12.5 scale heights. e^12.5 = ~250,000, which is
a factor of 40 improvement.
If you have carbon nanotube cable which has, say a 10 million psi strength,
your scale length is 3810 km, and your area only needs to grow by a factor
of 5 from bottom to top, so the reduction possible by using a tower is much
less helpful. Of course, we are not making 10 million psi cable in useful
quantities yet.
Daniel
I was on digg earlier, (sorry /.) and was seriously taken aback by the ignorance of the geek masses there.
I never thought someone who spends time looking at cutting edge science would have problems concieving of the validity of the space elevator. The tensile strength of the filament has been built to about 1/3 the necessary strength in less than 3 years. A method is in process to produce the filament en-mass when it gets up to strength, and NASA is backing the robot climber contest. every aspect of the project is being chipped away at relentlessly (and with notable progress). The location in the mid-pacific has been scoped out. (few storms, intl waters, far far away from anything but more pacific ocean, etc.)
There are preliminary designs for the sea platform. The counterweight as currently concieved will consist of a.) the least mass possible bunch of research oriented electronica, and b.)the first hundred or so test run ballasts.
These people are serious. check before scoffing.
I word things very carefully. Read it again. I said "planes can pretty much do that." I was actually thinking about commercial airlines, which fly above 72% of the atmosphere.
But, of course, there's this nugget from Wikipedia:
Balloons typically reach altitudes of 100K feet, which is above all but a fraction of a percent (it's a few Torr).
simply by building our velocity high enough to escape velocity while in the atmosphere and letting inertia take us out.
Ignoring that whole "air resistance" and "speed of sound" thing.
And curiously, if it wasn't for those two things, we could do that right now.
We use rockets for velocity, not altitude. If you doubt me, consider that the Space Shuttle's two solid rocket boosters shut off at lower altitudes than the X-15. Why don't we use a jet to boost the Shuttle to that altitude? Because the SRBs get the Shuttle to a much, much higher speed.
There's nothing "special" about Geosynchronous orbit which means you can "get the velocity from the Earth".
I get velocity from the Earth all the time. It's called standing on the ground. (Curiously enough, if I didn't, I would start flowing in these little circly patterns, called Hadley cells, which are what happens when you have a viscous medium gravitationally sitting on top of a rotating sphere. If the atmosphere extended enough, it essentially wouldn't be rotating.)
That's what special about geosynchronous orbit. Orbital velocity is slow enough that I can use the Earth's rotation to supply it.
You DO have velocity.
Which I got... from the Earth. Like, when a plane lands, after heading west, how the Earth speeds it up in a matter of seconds?
The idea is at that height, escape velocity is negligable.
It's not "negligible" - it's two thousand miles an hour (curiously, roughly 1 km/s). It's just neglible in the rotating frame of the Earth.
Hell, you don't even need to reach escape velocity - just build a pyramid 36000km high, hoist stuff slowly up the side, then give it a gentle push!
Alien tourists would come to see the only planet in the galaxy that looks like an ice cream cone...
What part of "a well regulated militia" do you not understand?
The point is that the cable is by far the hardest part.
You don't know that. Ask a materials scientist working on carbon nanotubes how long it will take to get that cable, and you might get an answer of "5 years". Ask an engineer how long it will take to design that climber (and the subsequent power delivery system) and they might say "5 years" as well.
It's a difficult problem, and the climber's power needs drive the power delivery system. So it makes sense to work on the climber first.
When we are 75% of the way to producing an adequate cable we can start the other parts.
That's an extremely naive business model. They're working on the two things in parallel.
like building the lunar lander for Apollo but having boosters no larger than a bottle rocket.
You think people weren't planning the lunar lander well in advance of having the launch capability of reaching the moon?
..\/
_/\_
has a lesser mass than
/....\
\..../
_\/_
Aside from that, if you build the tower first, you can launch from the tower to build the rope, and start getting significant returns much sooner.
Last of all, it's easier to blow the second example free in a case of terrorist attack. It's rather hard to do much to the first. And if it does break free, it does tons less damage in the first case (the tower+rope).
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
Your post makes me incredibly glad I learned physics using only metric units.
Megainches??? Do real scientists seriously use such a measurment?
-- If you try to fail and succeed, which have you done? - Uli's moose
I never called the robotics "trivial", I called them simple in comparison to the CNT ribbon. I am a materials scientist working on Carbon Nanotubes (to also reply to your post below), and while growth isn't my concentration, I do know from the literature that the fastest growth acheived for CNTs is 10-100 microns/sec.
Now CNTs are only strong if they are continuous. In other words, if you spin a thread of them the tube to tube bonding would probably not be strong enough for the elevator. So to build the ribbon you have to grow continuous nanotubes to the length you want the ribbon. If we assume the upper limit on the nanotube growth rate I stated above, then it would take approximately half a million years to grow one mile of ribbon.
Since I'm not working directly on the ribbon I could be wrong about a few things, but the point is that there are several very tough technological obstacles to growing the ribbon. In contrast the climbers build on technology we already have, so that's why I said they are simple to build in comparison to the ribbon.
Centrifugal and Coriolis forces don't exist in an inertial reference frame, but are a necessary addition to real forces to make Newton's laws of motion work in a rotating reference frame. They are not only used by laymen; if it's easier to understand or calculate something in a rotating reference frame then scientists will use them. I've read that the calculation of the Lagrange points is easier done that way.
This quote from http://en.wikipedia.org/wiki/Centrifugal_force is perhaps instructive:
"Because rotating frames are not vital for understanding mechanics, science teachers often de-emphasize the fictitious centrifugal force that arises in a rotating reference frame. However, in their zeal to stamp out the misunderstanding of the term in this one case, they may try to expunge it from the language entirely."
I think it's a bit funny that every time centrifugal forces are mentioned, someone pops out of the woodwork to complain that they don't exist, but no one seems to mind explanations citing a Coriolis force. Both are pseudo-forces and have equal legitimacy.
a,e,i,o,u and sometimes w and y (at be if of up cwm by)
it appears to me that you hold the belief that if you go straight up from the Earth, you'll keep rotating in line with the point you launched from on the surface.
:)
I will if I keep holding onto a giant pole. Which is what this is.
"Pretty much" only scores with horseshoes and hand grenades
The Shuttle SRBs shut off at nearly the same altitude as balloons reach. Scientific balloons are up at 40-50 kilometers. At that point, you're above 99.9% of the atmosphere. If you really wanted to, you could get almost arbitrarily high - it's just a question of how large you'd like the balloon to be. Like I said. But you don't use balloons instead of the SRBs, because the SRBs supply humongoid amounts of velocity as well.
To orbit, you have to get all the way out of the atmosphere
To orbit, you need velocity. Whether or not there's atmosphere only tells you how long you're going to orbit for as your velocity bleeds away thanks to air resistance.
Heck, the Space Station is still in the atmosphere, and it's orbiting.
There are a whole host of ways to get things to high altitude, but none of them really work clearly better than rockets because you need velocity - that is, none, save the space elevator, which accelerates very, very very gently over a very, very long cable.
Orbiting tethers, for instance, could pick up a payload off of a balloon-launched payload. That'd get you to a high altitude, but in order to pick up the velocity required, the payload would experience a supremely ridiculous amount of stress when the tether picked it up.
Or you could launch a rocket off of a balloon-supported platform. But again, the stress would be insane because the amount of velocity you need to gain in such a short time is so high.
Or we could build a really, really tall tower. But unless we get out really, really far, that tower won't do a tiny bit of good, because the (angular) velocity you need is so freaking high that, again, the stress would be nuts. Or you'd use a rocket - but the fuel savings on the rocket wouldn't be that large.
The atmosphere is essentially gone by 50 km. It's down 3 orders of magnitude. At 100 km, it's down 6 orders of magnitude. At 150 km, it's down 9 orders of magnitude. But even building a gigantic tower out to 150 km wouldn't significantly help with launching a spacecraft. You'd still need a rocket.
Actually no. At geosynchronous height you still need orbital speed.
Yah, yah, it should've said "angular" velocity there, not velocity. I do, however, commend you on saying that in one paragraph rather than 5 as the other poster did.