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back to article Space elevators, vacuum chutes: What next for big rocket tech?

We recently suggested that even the most advanced rocket currently slipping the surly bonds of Earth is nothing more than glorified V2, over 70 years since Hitler's Vergeltungswaffe 2 first lifted off the pad at Peenemünde. Today, we'll have a look at some technologies that may one day allow us to escape V2 designer Wernher von …

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Facepalm

That NASA and Amurrican flag on the space elevator fantasy picture ... most ridiculous.

Next: The Imperial Seal of the Holy Roman Empire on the Space Shuttle.

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Anonymous Coward

Yah, that should be a blend of the EU & Chinese flags!

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Pint

EU?

Including Cyprus, Greece, etc ? LOL.

More seriously, most of this sci-fi is so far in the future that it's more likely to be places like Brasil or the Philippines or somewhere in Africa taking up the slack. China and Europe will be full of the retired elderly by then. The future belongs to those with birth rates above 2.3 per lady.

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On the subject of space elevators Arthur C Clarke's The Fountains of Paradise is worth a read. In my opinions it's actually one of his best novels.

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And it's a good book for the author's notes at the back, in which he outlines the history of the space elevator concept- and also owns up to shifting Sri Lanka onto the equator.

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I think many others do the same in their sci-fi in intimation.

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he also found out...

... that because of the uneveness of the earth, he didn't need to move the island and his house was pretty much in the right place for the base station. Fabulous concept. (As an aside, the computer tech is really old fashioned)

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Go

"bell x1" BAH!

the americans just copied the miles M52!!

the breaking of the sound barrier sound have been a BRITISH success story!

plagiarise much?!

http://en.wikipedia.org/wiki/Miles_M.52

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Re: "bell x1" BAH!

Not the only example of US success from British research, and non reciprocal arrangements (they got our research but we got nothing back!!!)

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Re: "bell x1" BAH!

The X-1 was a rocket powered plane, not a turbojet. But like the M52, it had two wings and was pointy on one end, so I can understand your confusion.

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Facepalm

Re: "bell x1" BAH! @Don

You misunderstand I think....

I was pointing out that it was the fact we gave them our research that allowed them to solve a big stability issue they had been having (tails...), and then they didn't share theirs back....

I am all for sharing research, I just feel the US in general was a bit of a one way sponge for research in the past..

They are much better now.. just look at NIF & that HiPER will be able to build upon its research, shows that they are sharing...

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Niven & Pournelle

Their Footfall novel along with The Mote in God's Eye, used Orion and a few other DOD projects from the 50s, 60s and 70s for the drives in various scenarios. Indeed the heffalumps invading Earth in Footfall used laser powered shuttles.

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Re: Niven & Pournelle

Not to mention the heffalump invasion force parachuting in from orbit. Footfall was fun. It needs the special effects film treatment.

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Don't pictures of space shuttle glistening in the night look fantastic. The Russian one exemplifies it; but I've some of NASA's and they're the same. An era has passed now she no longer flies.

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just confirms what I suspected

i always suspected rocket science was bunch of bullshit

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Re: just confirms what I suspected

What's your opinion of brain surgery?

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Re: just confirms what I suspected

Sorry, some explanation required there. Why do you think it's bullshit.

I mean, I could just as easily say you are made entirely of bullshit. I've produced just as much evidence.

So common, rather than blurting stuff out, let's have a reasoned argument about why you think it's bullshit.

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Joke

Re: just confirms what I suspected

http://www.youtube.com/watch?v=THNPmhBl-8I

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Re: just confirms what I suspected

Well, with brain surgery there is no long pointed tube that thrusts, so I assume it must be cow shit, rather than bull.

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Nice round up, but the only one sounding practical in the near term is Skylon, long term space elevators look good.

I really hope someone throws some cash at Skylon soon, although their progressing quite nicely from the sound of it!

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It's worth pointing out the cost figures for Skylon are expected to be around 10 million dollars per launch with one Skylon having a lifespan of at least 200 flights.

15 tonnes lifted to LEO for only 10 mil? And the 1st prototype is expected to fly in 2018? Point out anything the Americans have coming down the pipeline within the next 20 years that'll match that.

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Anonymous Coward

Space elevators are, unfortunately, still firmly in the land of science fiction. The elevator has to have a counterweight beyond GEO, and GEO is really, really far away. Like, really far. Super far. So far it's amazing we can even put satellites there far. The idea of tethering an asteroid or whatever beyond that, and then stringing a near infinitely strong, thirty thousand+ mile long column of carbon nanotubes between the equator and it is, frankly, absurd.

If you've got the materials and knowledge to engineer a space elevator, there are far more reasonable (and safe) options, like the space fountain, which combines magnetic acceleration and space elevator concepts to find a happy medium.

Some might point out that space elevators could be useful on lower-mass objects like Mars, the Moon or big asteroids. The problem there is that their GEO orbits are still proportionally far away - if GEO is close enough to use a space elevator, gravity is weak enough to use a simple maglev launch sled.

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One idea missed

That's the satellite with giant rotating arms which scoops a balloon out of the atmosphere and deposits it into space. Thanks to Charles Stross "Saturn's Children" for introducing me to this idea. It's probably even more hairy than a space elevator as an engineering project, but doesn't require quite such strong materials.

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@AC

Well for me I'd include space fountains and launch loops in with space elevators as it is really just a different way to build a physical link with space and you ride in an elevator ;-)

but for the next 100 years we need skylon or bigger versions of it..

Every other tech uses multiple components, meaning more points of failure..

With skylon you have two engines, can run it from an almost normal runway basically, and so far the tech has been proven, nothing about it is radical any more...

Maybe they say 200 launches each, but who's to say that can't be extended with a damn good refurbishment after 200...

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Childcatcher

@AC Space elevators in the land of science fiction

Some might point out that space elevators could be useful on lower-mass objects like Mars, the Moon or big asteroids. The problem there is that their GEO orbits are still proportionally far away - if GEO is close enough to use a space elevator, gravity is weak enough to use a simple maglev launch sled.

I had not heard of a space fountain before; I had always assumed the elevator portion of the space elevator would use magnetic lifting rather than mechanical. Also, setting up a space elevator on the moon might make sense in as much as it provides a lower bar to get over in developing the technology for use on(ish) Earth - plus, you get a nifty moon base as part of the package. Of course there would be other problems not covered by this model (e.g. wind sheer), and it would require getting there with all of the materials needed to build it or starting a mining operation locally...

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FAIL

Space elevators simply won't work. Never.

The difference between a very big Eifel tower and a space elevator is, that the tower is rigid. And we need rigid because the speed of an object on the surface of the earth is much slower than the speed of an object at GEO. So going up the tower, we have a vertical component, and the horizontal component we take from the earths rotation around its axis.

Not so with the space ribbon. This means with every object we send up, the counterweight will start to lag. Energy is taken from the counterweight to speed up payload, so it will lag and it's orbit will decay. And this will get worse with every payload we send up.

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Pint

Re: Space elevators simply won't work. Never.

Unless you ferry reaction mass to the counterweight and boost it a bit....

But yeah there's basically the point "It's not an elevator, it's a railgun with an additional vertical component, or something. Deal with it, nerd!"

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Feasible Space Elevators

Trying to span the depth of the Earth's gravity well with a single structure is terribly non-optimal from an engineering standpoint for a number of reasons. Smaller elevators, however, are quite feasible with off the shelf carbon fiber.

Imagine a rotating cable with a tip velocity of 2400 m/s, and a comfortable 1 gravity at the tip. The radius then works out to 587 km. You don't want the tip to enter the atmosphere, so you set the orbit of the center to 750 km, and the lowest point is then 163 km. The center then orbits at 7.48 km/s, and the tip is moving 2.4 km/s less or 5.08 km/s. Subract the Earth's rotation and you have a velocity of 4.61 km/s relative to the ground.

Your launch vehicle now has a much less challenging job than getting all the way to orbit by itself. It merely needs to reach a landing platform at the tip of the cable. To return to Earth, it has much less velocity to dissipate, so the re-entry heating is much less. Cargo heading to higher orbit merely rides for half a rotation, then lets go. It now is moving at 2.4 km/s above orbit velocity, which puts you in a high transfer orbit.

The load on the cable varies linearly from center to tips, therefore is equal to a cable under 1 g half the length, or 293 km. Good carbon fiber has a breaking length at 1 gravity of 360 km. We want a decent margin of safety, so only load the cable to 40% of ultimate strength. This requires tapering the cable from center to tip, as each point has to support the payload + cable outside that radius, but the taper ratio is not severe, about 7:1 in area.

Because this design is 40 times shorter, it is much less exposed to meteor and debris damage, but they still are a risk. Therefore you build the cable out of something like 21 strands, of which 7 are spares, and cross-connect them every 5 km. So when the inevitable impact happens, you only have to replace the one 5 km segment, which is 0.02% of the total structure. The "single cable" illustrations like the one in this article are just terribly unrealistic from a safety standpoint.

This type of rotating space elevator is called a Rotovator, and can start being useful while under construction, so you don't have to build it all at once. As the length increases, and tip velocity goes up, the launch vehicle needs less velocity, and can therefore carry more payload. If some of the payload is more cable for the Rotovator, the increased cargo on later flights "pays back" the payload spent on launching the cable. This payback time in cargo mass can be relatively short.

You can build a second Rotovator in high orbit, which captures payload sent up by the first one in low orbit, and forwards them to interplanetary trajectories. Since kinetic energy is not free, you need onboard electric thrusters to maintain the Rotovator orbits, but those have ten times higher efficiency than conventional rockets, so you still come out very much ahead on net cargo.

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Devil

Re: Space elevators simply won't work. Never.

No it won't... it will stay as tight as a string.

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Happy

Ummm Space Elevators are easy.

Get ONE thread up, in whole or in part, then get up a counter weight - a very small one, enough to allow a second thread to be pulled up.

Then add more threads, more counter weight, etc., etc., etc...

1000Km sections, glue on the overlapping joints.... easy.

Once the thread is strong enough, and the counter weight is enough to take it from a goat track into a single lane highway.....

Away we go.

10 metric ton loads.....

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Pint

On Space Elevators - add a damn pulley already

Space Elevator concepts often include laser beam system to beam energy from the ground up to the crawler. I think that's a stupid approach.

Instead just use a pulley at the top end, on the counterweight. The carbon nanotube string obviously needs to be twice as long. At the bottom end is a simple motor. The crawler is rolled out, clamped to the string, fire up the motor and off you go.

Efficiency might be improved if there was another one coming down on the opposite side of the loop at the same time. They might want to slow down to pass, or use winglets to assure separation.

Critics of this Pulley amendment to the Space Elevator concept will claim that "it's completely impractical" to add a pulley and make the string twice as long. I guess they forgot that we're discussing the gol-damn SPACE ELEVATOR concept - itself completely impractical to the point of insanity.

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FAIL

Re: Space elevators simply won't work. Never.

Dear mr "Destroy All Monsters", if that is your real name. Could you please calculate for me how much reaction mass would be required to give the counterweight "a bit of a boost"? Then compare that to the reaction mass required using a conventional rocket? Of course you can't, because you're calling other people pointing out the bleeding obvious "nerds" you have no clue of the real world around you.

But I can.

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Facepalm

Re: Feasible Space Elevators

Yes, this would work like pulling yourself up by your bootstraps. Why don't you jump in a lake and show us?

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Happy

Re: Space elevators simply won't work. Never.

Really? I like your argument...

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Re: Feasible Space Elevators

You clearly don't understand orbital mechanics. Of course grabbing a sub-orbital cargo and accelerating it to higher orbit will lower the Rotovator orbit. That I why I mentioned on-board propulsion to make up the kinetic energy lost.

That allows you to substitute low efficiency rocket (on an unassisted rocket) for high efficiency electric thrusters (on the Rotovator), saving you 90% of the propellant consumption, which turns into more payload.

I spent a career in Boeing's space systems division, and am writing a book on the subject ( http://en.wikibooks.org/wiki/Space_Transport_and_Engineering_Methods ) so please credit me with having a clue what I am talking about.

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Facepalm

Re: Feasible Space Elevators

Designers of Space Elevators should not ignore the Coriolis-force, unless they are writing a work of fiction.

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Re: Feasible Space Elevators

I haven't ignored it. For a Rotovator design, you hook on and ride half a rotation and then let go. The forces are purely radial in that case. If you are climbing from the tip of rotation to the center, you do see a Coriolis effect, but let's look at the numbers.

Assume you have a maglev-type track that lifts a payload from the tip to center in 3 hours (200 km/s for a ~600 km radius), and the tip velocity is 2400 m/s. Therefore you much transfer 0.22 m/s angular velocity to the structure. The radial tension in the structure is 9.8 m/s at the tip, so you produce 2.2% deflection from purely radial while climbing. This is a manageable deflection of the cable structure.

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FAIL

Re: Space elevators simply won't work. Never.

This means with every object we send up, the counterweight will start to lag. Energy is taken from the counterweight to speed up payload, so it will lag and it's orbit will decay. And this will get worse with every payload we send up.

No orbital decay. The energy to reach escape velocity comes from Earth's rotation, all you need is fuel to lift the car to the required altitude.

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Re: Space elevators simply won't work. Never.

Sorry, forgot the rest:

The lag incurred by lifting the car is compensated by keeping the elevator cable under sufficient tension. When the car stops, the centrifugal force will straighten out the lag.

NASA put money into this. You think they'd have done that if it required the same amount of fuel as conventional reaction thrusters?

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Mushroom

Re: Space elevators simply won't work. Never.

I say use the Project Orion system to get a 5000+ ton platform with all the nano tube cables you could ever want into orbit and then you can start to work on it.

I'm sure with modern computer blast modelling we could make cheap powerful enough atomic charges with a radiation half-life of say just a few days/weeks so the environmental risk would be much much lower.

If we could get a few thousand tons of materials into space it really would start the way.

Just one Orion launch is maybe all that's ever needed.

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Boffin

Re: Feasible Space Elevators

So... According to Wikipedia - http://en.wikipedia.org/wiki/Space_elevator - Tsiolkovsky's original idea was a tower, which would be in compression. Current thinking resolves around a cable, in tension. Is there a feasible midpoint, which is neither in compression nor tension?

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Anonymous Coward

Re: "Space elevators simply won't work. Never."

Space elevators will never not work.

Or in other words, space elevators will always work.

It's very amusing how morons have an awful propensity to say the exact opposite of what they wanted to, because they are not intelligent enough to understand the meanings of the words they are trying to use.

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That's what happens when you leave development up to governments

So the basic rocket used in the 1940s is little different from the ones in use today - 50+ years later. Quel suprise!

Government agencies have little reason to pursue developments - they're expensive, they don't always work and even if you do make a thingy work better, all you get is a pat on the back and a memo of thanks.

Compare that with the (commercially driven) aircraft industry. Coming out of WW1, in 1918 aircraft were still made from wood, with 1 or 2 piston engines and room for one or two "lucky" drivers (though some of the "latest" bombers could carry 6 people). And they were about as reliable as Windows 3.1 However there were lots of civil aviation companies - all competing for government contracts and commercial uptake. Hence, 50 years and a few more wars later we had Jumbo jets.

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Take a look at some '50s research

http://library.sciencemadness.org/library/books/ignition.pdf

That is a summary of liquid propellant research (the good, the bad and the insane). They tried everything at least twice (US Navy or Army funding). I cannot imagine work like that being repeated today for at least three reasons. Governments are out of money. When they do spend money, they are useless at asking for what they need and even if they get that right, they ask companies that are experts at taking the money, delivering nothing and getting another contract to do the same thing again.

After reading about it, I can see why 50's tech is so enduring. (Spacex Falcon 9 is kerosene/LOX.)

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Windows

Re: That's what happens when you leave development up to governments

You know absolutely NOTHING about aviation history.

But that's typical of people who try to make everything a political agenda.

Take a day off, sock puppet and google some history.

< you

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FAIL

Re: That's what happens when you leave development up to governments

Yes, but cars still have four wheels an engine and a steering wheel.

But wait, they were saved by the government a couple of years ago, perhaps that's why?

But seriously, get of you "company good / government bad" horse. It's limping. Badly. It needs to be put down.

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Re: That's what happens when you leave development up to governments

Cars were saved by government?????

Laughing Obama.jpg

And really, the only thing that needs putting down is excessive government (What is excessive? Everything beyond a government managing the receptions of other government's diplomats: select the restaurants and all that) . Hell, we could have done a lot more with a few world wars less, for starters.

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Happy

Re: That's what happens when you leave development up to governments

Yes: www.dispatch.com/content/stories/editorials/2012/10/31/obama-helped-when-car-makers-needed-it.html

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Mushroom

The reality is...

until we invent / discover a better source of power, a 'vacuum propeller' and we all work together, we are going to be stuck in the local area.

Mind you, given that it looks like something / someone a while back was re-fueling at our sun, do we really want to get to far out there.... now where is my tin-foil hat.

ka-boom, cos thats all we can manage at the moment - firework on a stick :D

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Re: The reality is...

"ka-boom, cos thats all we can manage at the moment - firework on a stick"

Yeah, but, then again, our cars all basicly run on fireworks in a can (ok, cans), so it's a valid power source if not the most efficient.

That said, I sure would like to get off this rock. Would someone fix that please?!

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