Growing a beanstalk

[chrispenycate]

When I attacked the “orbital tower“ in “future inventions“ I ground the thread to a halt for quite some time (nobody was used to me back then, now it’s much easier) and it was assumed I was opposed to the concept. Not at all; I was criticising time scales. One of the major problems is the mass at the top of the string ; getting an indian rope to stand upright is one thing, being able to climb up it is a quite different matter. This stabilising lump should be at least a couple of orders of magnitude more massive than the payloads climbing up to it, otherwise those loads will destabilise its orbit, ultimately pulling it down on the heads of those living in the tropics. So no fiddly little bits like the international space station ; think big.
The “fountains of paradise“ tower moved an asteroid into geostationary orbit, which presupposes a flourishing space industry (and a long lead time, and a population on Earth who were sufficiently confident in space technology to accept a dinosaur killer of Damoclese meing manouvered into place above them) Another solution would be a mass driver on the moon, patiently firing off lumps small enough to me acceptable risks if any went astray, and a robot collection force sticking them together into one big block. Lots of years to produce a sufficiently heavy chunk, but you can be doing other things at the same time. Still, it needs a functioning moonbase, and a lot of heavy engineering up there before you can start. Here’s a third possibility, requiring no esoteric technology, indeed we could build it now. Rather than write a technical article, I’ve written it as a story ; a very bad story, with no characterisation, not one for critques, but not just a factual rundown.
It wanted to get longer ; and possibly it’s too definitive for a discussion thread, but here it is, probable spelling mistakes and all.

[chrispenycate]

Beanstalk

Equador was delighted. Not the entire population, of course, but enough that the spoil-sports could be ignored : After all, it would be more than ten years before the actual launch would take place, ten years while international money poured into the country. Certainly, most of this money was paid to foriegn specialists, but even they spent a fair amount of it locally, while there were always bits that stuck. Besides, the transport systems, road, air. wide gauge railway, the industries that were cheaper to set up on site, everything from power networks to an educational infrastructure that were paid for by a planet were a mighty rent for an slight inconvenience a decade down the line, when politicians and no few voters would no longer be around to take responsibility.
The middle of a jungle ; the few inhabitants bought off with bribes, a county-sized area roped off, security posts and fences installed, alarms and soldiers, cameras and underground detectors, flight preventers that would shoot down a bat, let alone a hang-glider or hopper balloon. The DNA of everyone with clearance to the site was stored and coded, magnetic photographic tatoos could be compared with records at a moments notice. Construction workers’ positions were monitored continuously.
A construction project big as a smatt town was laid out to the millimetre Razed down to bedrock, flattened, smoothed.. No opportunity for error, in this biggest project in history. The pillars were installed and work started on the largest artificial flat surface on Earth, metres and metres thick, welded, poured, rivetted and screwed by workers so widely separated that their intercom phones needed tens of relay stations, that it wasworth having several different helicopter landing pads. Big, heavy, and enormously solid. Cranes lifted containers from all over the world onto this raised surface, where huge truks crawled ant like to deliver them to further cranes, where constructions higher than skyscrapers were taking place, The great pyramid could have been sat on this plte, with no risk of it buckling, and looked like a pimple. All superlatives went out of the window as nations stove for the “estest“ Steering rockets biggere than Saturn fivesblended into te detail under a dome which could have sheltered all the football pitches in the world, braced, and butressed, all weak spots packed. Mass ? Anything that could conceivably be useful in orbit was shock mounted into the megastructure. The factory to manufacture the actual cable.to be lowered back to Earth is there in triplicate ; cheaper than having to fly out spare parts, muh so than having to do the operation over. All over the planet employment was at a maximum as peasants who were no longer essential on the agricultural front joined the production lne for the dream.
More than a million workers directly, ten times that in logistics and administration, and fife hundred times that in the streams of components and raw materials, food and power, security and comfort that kept this army going. Never mind the politics and backbiting, the spirit of mankind had been kindled, and through the thin air and the heat, at nightime under lights that could be seen from the moon, ignoring festivals religious or secular, the work went on, construction went on the control systems were installed, tested, retested and duplicated, triplicated. At a snail’s pace from a distance, advancing faster than anyone had any right to hope for, men and their machines of a hundred races and asmany manufacturers coöperating and competing, taking drink together rather than trying to kill each other as millenia of tradition would demand ; that could come later, when the job was over. The Olympics of those years were dull, insipid things ; everyone knew where the true brightest and best of every nation could be found.
Finally, eighteen years and two months from the day the first bulldozer, watched by smug politicians and cheering crowds, had first broken sod, the dome was closed, the triply redundant components triply checked, the tiny human cargo (twelve people, of as wide a variety of races, sexes, and abilities as could be found) had been sealed in, breathing canned air for over a week, The countdown started, and the security teams did a last sweep of the area, collecting up a few last ecoguerillas who, unable to prevent the launch tried to at least attain the status of martyr. Bunkers battened down ; even at fifty kilometres from the epicenter, the shock would be massive,
The first hydrogem bomb was buried below the middle of the baseplate. A pepperpot of tunnels directed the shock wave, but mostly it just vaporised or pulverised the rock. The pillars disappeared but the enormous, clumsy contraption was actually rising when the second fusion explosion added itself to the inferno. The third was dropped from the vessel itself, an air burst but still close enough to the surface tfor the reflected wave to add to the projectile force. Any renaining protestors (along with all the natural jungle life) were by now so finely distributed that forensic science would never find a clue of their existance. More bombs ; the ship is now in free flight, and rising fast, gaining speed and height. Cheering crowds, unable, however they’ve been warned, to imagine the immensity of the phenomenon, have organs ruptured by the shockwave, sunburnt or blinded, deafened ou even dead. Still it lifts, the Atlantic appears, far far below. Not that those inside are aware of this ; the violence of their propulsion system excludes all observation. Flat on their waterbeds, they have no say in what is going on, conditions calculated by inertial guidance, inside their determinedly kicked football.
The observation planes, flying as close as they dare to this sequence of bikini blasts (one too close, and it spirals down untill its crew can abandon it and bail out, clinging to the data they’ve recorded as tightly as to their parachutes) see the ocean before them dimple as the airbornr shock wave hits it, driving a gentle ring of ripple which will be a mighty wave when it hits the Atlantic dikes, already strained by the disappearing icecaps. And benighted Africa and Europe see the western strobe dawn like lightning across the sea.
The edge of the atmosphere, and individual bombs are less effective, Still, almost enough velocity has been gained, if it crashes now a new dinosaur killer could reduce the diversity of species on the planet, possibly including one so full of hubris they believe they can carry fire back to the gods. Still the explosions continue, lifting it out of Earth’s shadow, out of the lower junk belts and towards its target zone, a Clarke orbit fixed above a single point on the equator.
The shaking stops ; time to stop relying on dead reconning, and take some observations of the true state of affairs ; the circularity of the orbit, with what precision it’s lined up with the Earth’s rotation. As the plasma cools, humans talk to humans, computers to their kin, and water isolated astronauts suit up, and crawl to release panels covering the jets, the outlets for the factory cables, windows, hatches. The Indian hermaphrodite makes the prepared speech, explaining that the flight was for everyone, not only preparing the way for a new simplicity for exploring space, but using up the arsenal of death, riding potential extinction of all life, bridled to offer man the stars.

[dreamwalker]

Hey chris, could you please explain the bit where they have nuclear explosions, I mean, when I have an nuclear explosion in a story, I really wanna know why

[chrispenycate]

There is no known chemical reaction that would give me a fraction of the energy I need to get this mother moving, and I set the rule that it had to be possible with today's technology, no major discoveries in either physics or materials science required. A smaller one using atom (fission) bombs would have been possible, but very nearly as messy, so why not go whole hog (what's a few hundred thousand extra cancer cases due to the pulverised plutonium in the upper atmosphere, after all)
But the other reason is to reduce the number of nuclear weapons available on Earth, and the risk of any of them falling into the hands of someone who thinks of them as some kind of giant conventional weapon (or someone with God on his side who doesn't care)
After all, you only have to get that right once (and if you get it wrong, I doubt whether many people will have the leisure to criticise.)

So fusion, because it's the only energy source powerful enough, and bombs, because they're the only way we now know to induce fusion.
How would you move ten or twenty megatonnes into orbit?

[dreamwalker]

Originally Posted by chrispenycate

So fusion, because it's the only energy source powerful enough, and bombs, because they're the only way we now know to induce fusion.
How would you move ten or twenty megatonnes into orbit?

Depends on the time scale.
However, i think it would be more likely that we'd gather that mass from the moon, or earth crossing asteriod.
As a rule, If the materials needed arnt avialible in sufficient quanties in space, then they probably won't be avalible from effecient sources on the earth.

I do have a problem with wanted to use up all of the nuclear weapons on the earth... As long as the foundation of knowledge is there, these bombs can always be made again from scratch.

[chrispenycate]

Grabbing an asteroid of dinosaur-killer proportions and nudging it gently into geostationary orbit would take a long time, a space industry built from nothing (I was tempted to say 'from the ground up' but it's more likely to be 'from the sky down') and be extremely dangerous; an error which involves it getting into Earth intercept orbit would likely be fatal for civilisation.

A linear accelerator on the moon would take even longer, but without most of the danger; a missed shot would become a meteorite, with the potential to destroy a city, at most (and plenty of time to calculate the trajectory and evacuate) And preliminary construction on the tower itself could start before all the counterweight was in place.

But the advantage of sending the package up from Earth, if you can eliminate the impossible energy price (and, joule for joule, hydrogen bombs are very cheap) is that most of your manufacturing can be done in an environment humans are used to, and understand.

[Urlik]

rather than trying to grab a dinosaur killer or firing bits of the moon, why not compromise and collect the smaller asteroids and meteors to use as the base for the geostationary platform?

or instead of breaking bits off the moon, how about breaking Cruithne up into manageable pieces and attaching rockets to them?

there is also 2002 AA29 which could be broken up into manageable chunks for manouvering into the necessary orbit.

[Nik]

Sorry, as a former Poul Anderson fan, I just had to yell that...
---
Um, I recently saw a bizarre but plausible proposal to stack rigid balloons to build a genuine orbital tower. Think 'million bouncy castles', end upon end unto 'infinity'. No counterweight required. No 'Extinction Level Event' if skyhook breaks. Each inflated section capable of making a moderately soft landing. Each section with active mass damping. Able to do a 'galloping gertie' to dodge satellites etc. Enough flexibility to 'hang together' if several compartments of sections are perforated by flecks. Self-sealing using internal 'paint guns' etc.

(Yeah, yeah, over-pressure is relative to working height's atmospheric pressure...)

Stack acts as 'support structure' for 'aerial ropeway' that does not need to support itself...

Anyone seen more on this ??

[Heinleinaddict]

I can't believe the concept of a working space elevator is so close to fruition..

[skeptical]

The idea of using nuclear explosions as propulsion is not new. It was termed the Orion Project, and was investigated by NASA, but rejected as being too risky.
http://en.wikipedia.org/wiki/Project...ear_propulsion)

The Niven/Pournelle book called Footfall uses an Orion spacecraft to attack their alien invaders, successfully. http://en.wikipedia.org/wiki/Footfall

Personally, I do not think we need anything so hazardous. When humanity eventually works to build a space elevator, we will begin with a space craft in stationary orbit, which will simultaneously lower a ribbon to Earth, and send another ribbon outwards. Gravity will pull one down, and centrifugal action direct the other outwards. The initial ribbons can be quite small and lightweight, and be used to haul mass into space to create a second, more massive ribbon.

Incidentally, while a counter-weight is probably going to be used, it is not strictly necessary. If the entire ribbon length is 78,000 kms, the outer length will pull the entire system taut without a counterweight.

[skeptical]

P.S.

The latest New Scientist has an item about a first step towards our tower into space. This one goes only 20 kilometres.
Inflatable stairway to heaven - opinion - 08 June 2009 - New Scientist

However, even 20 kms up permits a lot of value. It could be used as a launch platform for spacecraft, or for all sorts of research apparatus. The tower is based on inflatable modules stacked on top of each other, stabilised with gyroscopes. The value of this approach is that it could be done using today's materials.

On top of the tower, it is already dark, as if it were in space. It is above most of the bulk of the atmosphere. It could carry a pressurised tourist hotel. Perhaps astronomical instruments etc.

[Nik]

Yup, that was the one !!

Kin walk off with my NS if I even blink...

[Dave]

Slightly off-topic but to any Civil Engineers out there - Do you think there is any limit to the height of an actual grounded building?

I'm seeing many new towers going up around the world. The Taipei 101 will soon be dwarfed by the Burj Dubai. The Burj Dubai is so tall, it's still a secret how tall it will eventually be. I'm sure it won't stay the tallest building for long.

I think that for health and safety reasons - fire, earthquake, terrorism - these towers cannot be safe. It seems to me they are being built simply because they can be. And for the status and wealth they represent.

But other than those reasons, is there any physical limit to the height they can be? what is the point when with our current materials they cannot support their own weight? At what point is there a limit to elevator technology that means that it is infeasible to commute between floors? At what point do you need an Oxygen mask?

[skeptical]

Dave
I already mentioned a tower design to 20 kms above sea level (admittedly built on a mountain). However, even though a limit to height no doubt exists, humans are still a hell of a long way from achieving it. We will no doubt exceed the Burj Dubai by many, many times. Perhaps by several powers of ten. The likely limit is economic rather than due to engineering constraints.

[Xelebes]

The limit for height is around 15 km, I think. That is when not even a mountain can sustain the mass before the mantle gives way, or so I hear.