What technology is most likely to take us to the stars??

[Sparky]

I don't think a mag-lev would be a good idea.... The track would just snap under the forces involved. Have you ever seen an industrial chimney fall down? They snap in half because of the different speeds they are going at at different points. It can be seen (although not very well) in the below link.

http://www.youtube.com/watch?v=3FAVG1AaZ98

Now imagine this track stretching to space! The speed of the Earth "underneath" it would cause it to snap like a toothpick unless it was made of an unbelievably strong material, far stronger than any we have today.

 

[Aught3]

^I'm not sure if you've grasped the idea. A spacelaunch track is like a space gun, but with a gentle acceleration so the cargo and passengers aren't exposed to high g-forces. The track could run up the side of a mountain (or man-made structure) but it doesn't extend into space. At least that's the idea behind normal spacelaunch tracks - I don't think Ozy is talking about anything too different to this.

 

[Sparky]

Oh. So it will be only a few km long and on a shallow angle? That seems far more reasonable

 

[JBeukema]

If we ever develop *real* artificial gravity, G-force won't be a problem anymore

 

[Darius]

The first 2km/s are the hardest. 2km/s would get you far enough to not have to deal with any meaningful air friction, and your thrust would be much more effective. You would probably be able to cut out the need for multi-stage rockets and get past the need for designing different engines for different altitudes.

Still, I admit that when I looked at the 6700km/hour number I was a bit sad that it wasn't a larger percentage of the escape velocity needed. But, advances in technology could still bring up this number, and I think its the most useful technique in terms of its other applications as well. It's still better than the Mach 17 that scram jets can go. And I can actually imagine of the building process of such a method, whereas the carbon nanofiber tether just breaks my mind in terms of how you actually Build it and what you do when it gets hit by a meteor or space debris.

First off, its not a nanofiber its actually a carbon nanocrystal, which is why it is so strong. The odds of the tether being hit with a meteor or space debris and surviving are just as likely as a maglev train being hit while being launched. (All concepts of repeatedly sending something into space will require at least some maintenance) In addition to this, precise accuracy is needed to launch the maglev train into the atmosphere at the correct time a space station orbits overhead, in order to prevent collision with satellites.

Building the nanocrystal tether will take time I can't deny that, but so will the amount of testing and precise calculations required for a successful maglev train to be sent to a space station.

 

[Ozymandyus]

The odds of the tether being hit with a meteor or space debris and surviving are just as likely as a maglev train being hit while being launched.

That's not true - a permanent structure has a much greater chance of being hit by something than a structure that is only in a dangerous area for a short time, both due to your elevator's greatly increased surface area (many hundreds of times larger) and its persistence in a dangerous zone (in space 24/7/365). The chance of a meteor striking a particular space elevator (the actual moving part of the proposed system) and a space shuttle would be about the same, but hitting a part of the elevator tether is a very different probability. In addition, the space shuttle being destroyed would cause almost no damage compared to that tether being destroyed - giant counterweight which may decay and eventually strike earth, and don't forget a giant falling nearly industructable carbon nanocrystal tower.

I'm not saying theres a large likelihood, but its pretty much bound to happen eventually. The ISS can move out of the way (and DOES) when dangerous space debris approaches... this space elevator could not.

 

[Netheralian]

That's not true - a permanent structure has a much greater chance of being hit by something than a structure that is only in a dangerous area for a short time, both due to your elevator's greatly increased surface area (many hundreds of times larger) and its persistence in a dangerous zone (in space 24/7/365). The chance of a meteor striking a particular space elevator (the actual moving part of the proposed system) and a space shuttle would be about the same, but hitting a part of the elevator tether is a very different probability. In addition, the space shuttle being destroyed would cause almost no damage compared to that tether being destroyed - giant counterweight which may decay and eventually strike earth, and don't forget a giant falling nearly industructable carbon nanocrystal tower.

I'm not saying theres a large likelihood, but its pretty much bound to happen eventually. The ISS can move out of the way (and DOES) when dangerous space debris approaches... this space elevator could not.

Finally a topic I am familiar with... too bad it is off the original topic...

Few comments - a space elevator is not specifically a permanent structure. Some of the latest designs have the earth end tethered to what is essentially a movable oil rig platform. In this way it has a limited ability to avoid storms and potential space debris/meteor strike.

The counterweight must be beyond geostationary so it is already probably moving at an escape velocity - any breakage in the cable would eject the counterweight rather than it crashing to earth. You would however probably have a mid station at geosynchronous orbit which is also in a stable orbit. If you loose the counterweight you would probably have to breakup the cable otherwise the whole thing would probable come crashing back to earth - although this in itself isn't really a problem either.

An earth based space elevator should be something like 36,000 kms long (geosynchronous) + additional length to the counterweight. Estimates on mass for a small elevator are something around 20 tonnes so lets assume 100 tonnes for now. That gives you a mass of 2.7kg/km - its not really going to do that much damage - the stuff that doesn't burn up in the atmosphere that is. I've seen descriptions of it that suggest it would be somewhat like a falling leaf due to the air resistance.

Probably old info now, but I recall some years ago that cost was in the region of about $10 billion. The tallest buildings in the world at the moment costs more than this. Of course this assumes CNTs being commercially mass produced which is still a way off...

The technology is apparently now close. I.e. we are within an order of magnitude of the tensile strength requirements... But the theoretical strength exceeds requirements.

Benefits are enormous - cost reduction of mass to space of two orders of magnitude. Design effort of all spacecraft (and spacecraft mass) severely reduced as you no longer need to survive a violent launch. And you have a free earth escape trajectory at the counterweight end of the tether that also provides a non-zero G work environment. Look at all the interplanetary science we could do then!

 

[Sparky]

@ Netheralian

Verrrry impressive knowledge! And good explanation too

 

[Netheralian]

@ Netheralian

Verrrry impressive knowledge! And good explanation too

Such flattery...

Apart from the week or so of elevator music on the way up it would be kind of awesome working at the counterweight end with the earth always sitting squarely above you - and would be about 400x the size of the moon as seen from Earth...

 

[Ozymandyus]

Sorry that I continue to play the part of the skeptic, but where are you getting this information about cost and tonnage of the elevator? I can't seem to find any information to confirm.

A 36,0000 mile nanotube crystal structure that weighed 100 tons would cost WAY more than 10-20 billion... Just the materials (which are not available yet and therefore have no price) would cost much more than that. As of the moment we can't produce a structure longer than a few centimeters with anything near the tensile strength we are looking for here. Mass production of such an elevator seems laughable - surely we would only build one or two at the MOST. The actual construction is hard to even imagine - how do you build a nanocrystal tether 36,000 miles long? This would be a rigid structure, you would need scaffolding or air vehicles to lift the pieces into place and to somehow fuse it to the rest of the structure - its not like you can just build something a thousand miles long and then leverage it up. You would have to somehow launch a counterweight weighing many hundreds or thousands of tons into space, presumably in pieces by shuttles. And we haven't even talked about the actual Lifters that would need all kinds of technology to survive the different weather conditions, motors for the lifting, power sources, etc AND heat shielding to survive re-entry, presuming you didn't send them back down the tether which would make you only able to send one elevator at a time on journeys that take days.

I mean Jesus Christ we're talking about a lot of money here. These things always sound nice when looking at them on paper but in reality they never work out that way.

When you look at the required costs associated with propelling a craft into space per kg - the only cost that we cannot possible get rid of is the cost of propellant - but this is only $50/kg to put something into geosynchronous orbit. Once we have the technology that would make a long life single stage shuttle feasible, this is the ONLY cost that matters. The technology involved in such a rocket is really no more than would be required to build this elevator. If I talked about the costs of Mass Produced shuttles these costs become even more reasonable - and shuttles are the sort of things that you could feasibly mass produce, as opposed to 36,000km long rigid nanocrystal structures. Some of the costs of propellant could even be significantly reduced by rocket sled launches.

 

[CupOfWater]

I have faith in wormholes.

 

[Netheralian]

A 36,0000 mile nanotube crystal structure that weighed 100 tons would cost WAY more than 10-20 billion... Just the materials (which are not available yet and therefore have no price) would cost much more than that.

The cost info is years old and I can't remember the source - sorry for the lack of reference. Mass - 18000kg is quoted on Wikipedia - so i just added a bit of safety factor. However the mass is related to the physics of the thing staying up there. It needs to be super light otherwise it does collapse under its own weight. I will see if i can find some good references for you - maybe will start a new thread on it...

Of course the flaw in the cost argument is as you say. CNTs aren't commercially available yet and hence the price is a guess that is based on them being comercially available at a reasonable price. But due to the desire of these materials once they can be easily mass produced there will be a huge demand and hence hopefully the associated cost will go down.

As of the moment we can't produce a structure longer than a few centimeters with anything near the tensile strength we are looking for here.

Will try to find some more references on strength before commenting on this.

Mass production of such an elevator seems laughable - surely we would only build one or two at the MOST.

I don't believe anyone mentioned mass producing elevators - the only mass production I suggested was carbon nano tubes (CNT).

The actual construction is hard to even imagine - how do you build a nanocrystal tether 36,000 miles long? This would be a rigid structure, you would need scaffolding or air vehicles to lift the pieces into place and to somehow fuse it to the rest of the structure - its not like you can just build something a thousand miles long and then leverage it up. You would have to somehow launch a counterweight weighing many hundreds or thousands of tons into space, presumably in pieces by shuttles.

The structure isn't rigid at all, and you don't build it from he ground up. You actually build it from the mid point and go out in both directions. I.e. you have to start from an orbitally stable position and keep your centre of mass there. Which is why most Elevator designs are around the 72,000 km length. But as the tether is orbitally stable in a geosynchronous orbit it will just hang from the sky until it can be grabbed and connected to your ground station.

Obviously this entails some CNT manufacturing system that produces them in-orbit. You would then launch the raw materials and the manufacturing capability up. This is some of where the associated costing comes from - i think it assumes a reasonable price (admittedly currently not real) for the CNTs and then most of the rest of the cost comes form launching its required mass into Geo-orbit. Which is not easy or cheap - I think the existing heavy lift rockets available (ariane 5, atlas etc) can only get about 5,000 to geo orbit.

You don't really need a counter wieght - it could be part of the cable that is just extended further. Check wikipedia - a cable extended to 144,000 km would give you enough velocity for a free trajectory to Jupiter from which you can get a gravity assist out of the solar system. Anyway, once the cable is out you can start adding additional mass to whereever you want your counterweight by bringing it up from the ground in small parts at first but gradually increasing.

And we haven't even talked about the actual Lifters that would need all kinds of technology to survive the different weather conditions, motors for the lifting, power sources, etc AND heat shielding to survive re-entry, presuming you didn't send them back down the tether which would make you only able to send one elevator at a time on journeys that take days.

Lifters surviving differnt weather conditions? What are you talking about. Atmostphere extends 100km at most with the more servere weather conditions (due to air drag via atmospheric density) at less the 10km. You could just not lift when there is a storm around!!! And anyway, to be feasible you want a lifter that moves pretty quickly - i.e. more than 100 km/h (although speeds would be higher again once you get past midpoint and you have the centrifugal force flinging you out or gravity assisting on the journey home.

No reentry required - your on a tether - you don't have to enter the atmosphere at km's/second. So no ablative heat shielding required. Only thermal management for orbital environments.

Technology - there are competitions going on for the lifters for some years now. They aren't great yet but progress is rapidly being made. The energy supply of choice would be beamed from the ground station - simple photovoltaic cells could then power your lifter up.

Whats wrong with journey times of days? And there could be strategies for sending multiple lifters at the same time with possibly a "hand over" part way. I'm sure this has been thought of...

Actually one of the arguments I have against it technically would be thermal expansion. A cable with a thermal mass as low as this thing would be doing a lot of very fast expansion/contraction during solar exposure each day putting huge stresses on the cable...

I mean Jesus Christ we're talking about a lot of money here. These things always sound nice when looking at them on paper but in reality they never work out that way.

Who?
I'm talking about 2 orders of magnitude saving on launch costs alone!!!! You can also reduce your spacecraft engineering and design cost, and maintenace and refueling becomes possible.

And if it takes the entire NASA budget for 1 year (near $18 billion) then great - it would be worth it and would pay off within a few years.

When you look at the required costs associated with propelling a craft into space per kg - the only cost that we cannot possible get rid of is the cost of propellant - but this is only $50/kg to put something into geosynchronous orbit.

Umm - where did you get this from? Cost of putting a spacecraft into LEO orbit is of the order of $10,000/kg (about 4 times that to GEO). If you can find me a launcher that will do it for $50/kg we can make a fortune together!!!

 

[Grimlock]

Finally a topic I am familiar with... too bad it is off the original topic...

Yes and No in a sense it is actually VERY much on topic.

Right now we are firmly stuck on the earth the farthest distant we have ever traveled with maned space flight is the moon which in a way properly could be compared (in solar system terms) to walk down to the local mall and back.

In other words Not very far.

The main problem is that escaping earths gravity requires ALOT of money and traveling to other planets even more.

Take Mars we would need almost as much fuel to leave Mars as we would leaving Earth that,´s a SHITLOAD of fuel and properly even a bigger shitload of money would be required to make this come true.

That alone makes it VERY hard for us to even come any nearer, other then in our dreams and in game, to colonize Mars.

And if we can,´t colonize Mars, how the fuck do you expect any future colonizations of other planets much less the evolution of technology to make it real, to come close at being possible, the cost for such a thing would be ginourmus and go beyond any countries recourses to do so.

Now with the space elevator (they better haver some good music or movie because i refuse to listen or watch Hana Montana for a whole week, if there was nothing else i think i would jump out of the nearest air lock after just one day) suddenly things look less complicated.
We would be able to lunch spaceships from space stations and as such the fuel we would need to reach planets such as Mars would be SIGNIFICANTLY lessened and properly also the cost.

With easier access to space and other planets, much more research could be done on the subject of living on other planets and space travels.

As such Solar/laser sails or other technologies tied in with the subject of reaching other solar systems could properly gets years shaved of, because of the space elevator so if seen in that light you could say that space elevators where on tropic, as it could functions as one of the steppingstones towards the catalysts needed to researched and evolve the technology needed to reach other planets.

Besides a Debate isn,´t a debate if it isn,´t allowed to go off topic a little bit now and then as long as it is in some way related to the topic debated (if we where suddenly debating how to remove nose hair in a space travel topic THAT would be going to far of Topic).

So as long as it is somewhat related to the topic at hand, i don,´t mind if the debate goes of topic a little now and then.

 

[Ozymandyus]

$50/kg sent into space is the cost of the propellant, as I said. It costs more because of the REAL costs of building a shuttle and using partially or wholly non-reusable rockets. If we removed those costs by mass producing shuttles and making them fully reusable, we would only have the cost of propellant, an occasional catastrophic failure, and repairs and upkeep costs. If we made shuttles out of carbon nanotubes materials they would be ten to a hundred times lighter and stronger, decreasing the cost of propellant/KG and increasing shuttle longevity.

When people say it would only cost X to bring stuff into space via elevator, they often ignore these Real costs, costs of building and maintaining the elevator and possible catastrophic failure. All costs are idealized when the proponents of a new technology are talking about it - it always turns out to cost many hundreds of times more in reality. Same thing happened with the space program.

A carbon nanotube constructed tether like the one proposed would indeed be mostly rigid, it would flex a little but its not like a rope. The sort of structure that has the tensile strength we are talking about is only VERY minimally flexible, its more like crystal than it is like fibers or cable. Even a single carbon nanofiber barely flexes, why you think a gigantic structure made out of them would be More pliable I have no idea.

As for the platforms that move cargo: The weather conditions were including the harshness of space, a vacuum is not a particularly friendly place. And if you are going to be only using the elevator when the weather is nice, and the trip up takes days, and you have to move the platform when certain weather conditions are coming or whatever... moving a multi hundred ton platform that extends into space seems is a very costly endeavor, a bit akin to trying to move a skyscraper. The sort of energy it would take to move it is pretty tremendous and costly, and exerts strain on the tether and the point it attaches to the platform. As for the detaching from the tether and floating back down to earth, that was the design of the space elevators that I've read about, perhaps there is a a better way - who knows.

As for the cost estimates, did someone just take the cost of carbon nanotubes and multiple it by the weight, because thats about right for the 10 billion number... Thats like saying, concrete only costs 4cents/pd, and this building will weigh 50 tons... we could build it for like 4000 bucks!

Even if we do mass produce nanotubes for almost nothing and launch 200 tons of them into space: using your figures just for the launching of them would cost 400,000x$10,000/lb = 4,000,000,000 - nearly half the cost of your estimate just to move the raw materials into place. The cost of building a manufacturing plant at this altitude? Look no further than the costs for the ISS so far - it would need to be Many times larger than the ISS to be able to perform such a task of construction. The ISS is estimated to cost 100 Billion. This would be very close to the cost just to build a manufacturing plant in space. There are so many unaccounted for costs here, I think a number closer to 10 Trillion is necessary, probably more. Everyone always thinks this stuff could be so cheap, but it never will be - do you honestly believe building a 60000KM structure into space from highly advanced materials could cost LESS than a BRIDGE a mile long?? I mean.. HOW can anyone think that?

Anyway, if scientists think it will work they should do it, I obviously don't know anything particular about the subject. I just know that whenever people make early cost estimates like this, they always undershoot it by a LOT - that's just experience talking. I've enjoyed the discussion a lot either way and learned some stuff about space elevators... good times.

 

[AzureInsanity]

Meh, it seems unlikely that we'll ever reach the stars. Humanity spends too much time bickering over this planet to worry about going to others. There's an effort but it doesn't seem to be making any ground. Getting into space is such a big deal because of funding. We last visited the moon 40 years ago =/ and it's our next door neighbor.

 

[Ozymandyus]

We haven't sent Manned missions, but we've sent quite a few robotic missions out to the different planets. We have no reason to send humans back to these planets until we can start building permanent structures, which hopefully will be prebuilt by robotic missions.

It's just so much cheaper to send unmanned missions, and makes more sense to wait on technology a bit before spending billions on technology that will only cost millions within a decade. We also have some major problems to solve still like lightweight shielding and renewable energy - shuttles that had fusion generators would be much better for longer space missions.

I'm pretty sure the missions will get underway within the next 200 years or so, if we survive that long. Which I think we will.

 

[TheInquisitor]

I came across this article on Universe Today.

http://www.universetoday.com/2009/04/03/warp-drives-probably-impossible-after-all/

Apparently the Star Trek warp drive has some serious problems, not just the fact that we'd need something like 10^45 Joules of energy to do it, but Hawking radiation would cook anything inside the bubble to something like 10^30 Kelvin.

Apparently this isn't such a problem if you don't try to push it past light speed. So it would still perhaps be a useful way of accelerating to high speeds without the problem of G forces. I never understood why the warp drive in Star Trek couldn't be used at slow speeds. Why do they even need those primitive fusion driven impulse engines at all?

But as Lawrence Krauss (author of the Physics of Star Trek) said, "Truth is stranger than fiction, and the best is yet to come."

 

[Th1sWasATriumph]

When the sun goes Bye bye, we will have to leave this solar system, do you want to wait till that time to start figuring out how the fuck are we gone escape this mess, or should we start now so that when the sun finally goes off we won,´t stand around looking like a bunch of loosers.

The sun will die in a few BILLION years, I wouldn't be surprised if we have technology in place in a few thousand. Plenty of time, don't sweat it.

 

[ebbixx]

You bet! When I retire I'm gonna have a beach house on mars! =D

Enjoy your last few months with your tumors. Before one gets to Mars, you'll have to resolve the problem of prolonged exposure to cosmic radiation, among other nasties.


I'm with the Penguin... though I doubt we have a better than even chance of making it to Mars if current trends continue.

We're much more likely to be spending most of our ingenuity moving away from the sea shore (or making most major urban centers resemble Rotterdam) for the next hundred years, considering the "progress" made so far in addressing climate change. Though I suppose Mars counts as "away from the seashore." Though perhaps your "beach house" comment suggests we'll be shipping excess meltwater to Mars to make that beach?

 

[Icefire9atla]

Well, the first thing that we will use to take us to the stars will either be suspended animation or generation ships.
Probably powered by fusion (helium- 3 maybe?).

But, the other two options are certainly possible further into the future. My bet is on wormholes.