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public space travel in 20 years?

Posted by: 4thdimension - Mon Jul 16, 2007 10:09 pm
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Post public space travel in 20 years?   Posted on: Mon Jul 16, 2007 10:09 pm
More than that, I want to know what you guys think of the probabilities of there being created a cheap, efficient, means of space travel that would allow us to go into space in large numbers within 20 years. Let's think outside the box here, old school NASA technology be damned. It's just holding us back.

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Post    Posted on: Mon Jul 16, 2007 10:13 pm
Cheap, hmmm not too sure but id imagine under 10k in 20 years quite easily! and holidays on Earth are a lot now anyway! Think Virgin Galactic said something about how they saw prices going.

Efficient, again think compared to now yes but its all relative.

Hopefully it will be a lot less ;)

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Post    Posted on: Mon Jul 16, 2007 10:18 pm
Yeah, It will get cheaper, I'm just surprised that we are still using rockets. That technology is in effect over a century old.

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Post    Posted on: Mon Jul 16, 2007 11:03 pm
you can use two magnets and force their opposite polls to come to rest, one on top of the other, of good size, to launch a shuttle right out of orbit. Two half mile long magnets would pack one hell of a bang when the one on top is released.
But NASA doesn't think like that, do they?

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Post    Posted on: Tue Jul 17, 2007 9:27 am
Then let me give you three short questions to think about..
How would you manufacture such large magnets?
How would you "force their opposite polls to come to rest, one on top of the other"?
And finally.. How high would the accelerations be when you release them in "one hell of a bang"?


You write that rocket technology is over a century old. When you look at developments in historical timeframes it isn't that much. For example just think about how long it took to make sail ships cross the planet.

Two more, more recent, technologies for comparison:
You use Cars over a century now and nobody complains about using them and basically they are the same.
You use trains a lot longer and people still use them.

Of course when you look at the potential development time that could have been used, then spaceflight could be farther. But I see the effects on the society for example as part of the whole development process. You not only have to develop something new, you also have to prepare the society for that.

And that gets me to the point why one could think that spaceflight developed very slowly. Too less money. Of course one could say, damn politicians. They only look at best two years in the future and have no visions. Partly right for sure, but as the society isn't prepared for further progress they also represent (often unknowingly) the society.

To finally answer your question about personal spaceflight:
I really don't know as for example I always ask me one question: What will happen after the first accident (be it suborbital or orbital).
Just think about that:
Every day many deadly car accidents take place.. well no one would think about no using his car afterwards. The society is prepared for that and accepts that.
When you have a plan crash, hundreds die at once. You have that in the news and talk about it but the next day you use the plane for the flight in your vaccations. The society accepts that (with some expectations: e.g. Concorde)
And then the big question: What do you think would happen when today let's say SpaceShipTwo will crash with passengers onboard? Just look at Challenger, Columbia.

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Post    Posted on: Tue Jul 17, 2007 12:52 pm
Two magnets will not work because the force is only high when the magnets are closest to each other and gets less very quickly as the magnets separate. The real magnetic launch ideas are electromagnetic guns, some of which have been discussed on this site in other forums. Other out of the box ideas include space elevator, airship to orbit, and laser launch, all of which have been discussed on this site. Out of the box ideas for what to use in space, after getting to orbit, include solar sail and nuclear propulsion.


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Post Rockets all the way...   Posted on: Tue Jul 17, 2007 1:02 pm
Personally I believe that rockets will provide the first economic path to space. I think they are even better than hybrids (aka space ship one etc). I can't see any hypersonic thing getting us anywhere, even in 40 years. Just look at *supersonic* passenger aircraft.

The thing with time frame is need. It will only take on successful venture to get the ball rolling. 20 years is more than enough time. Providing we don't end fighting more cold wars or some such nonsense.

But 20 years is also not that long. We are waiting for the right economic factors to come into play. The most important is cost. We can do more now for the same money than ever before. this will continue until space becomes a reality.

All IMHO or not so Humble as the case my be.


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Post    Posted on: Tue Jul 17, 2007 2:47 pm
Ok i hate to double post but here are some figures.

the 747-400ER takes over 192 metric tons of fuel with a take off weight of 416 tons. That almost a 1:1 fuel ratio and its max speed is not even 300 m/s.

h2/o2 fuel combination needs a 10:1 ratio for a max speed of over 7000m/s. This sounds not that unreasonable.

We give rockets a hard time because of the current crop of rockets. But i don't think they deserve ridicule. They are in fact very good at what they do. Which is get up to very very high velocity's. Also every alternative does not sound like it really solves anything. Remember the fuel is cheap, the cost come from elsewhere.

So I'm punting for a VTVL SSTO rocket. ... With dense fuels unless its huge.

Considering that people can spend 10K on a plasma TV. It sounds like a reasonable price. I would pay that without a second thought.


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Post    Posted on: Tue Jul 17, 2007 8:06 pm
campbelp2002 wrote:
Two magnets will not work because the force is only high when the magnets are closest to each other and gets less very quickly as the magnets separate.

Bear in mind that the repulsion force between high grade neo magnets over about 15 meters long is not even as big as than their individual weights so a magnet half a mile long wouldn't even begin to move, no matter what you tried to make it from.


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Post    Posted on: Wed Jul 18, 2007 8:20 am
Hello, delt0r,

regarding technologies like the space elevator it is clear that they are more economic than rockets because - in particular they use the abundance of energy in space available in the form of solar power, fast moving ions and the like.

The use of rockets in so far is to install the initial versions of such technologies. In so far rockets might be limited to installations in the future.

Even NASA has a tendency to turn to such new technologies - under www.welt.de there was an article several weeks ago saying that there is work on the concept to install a catapult in orbit to launch vehicles towards the Moon without consuming fuel. The catapult in essence would be a rotating arm or boom or truss or structure - don't know at the moment how to call it most properly - a vehicle would dock to after reaching orbit. The arm would rotate permanently and the designers already have figured out that and how a vehicle can dock to the arm safely - according to that article. It is NOT a tether and does NOT have to do with magnets.

The installation of such technologies in orbits around other planets can be done this propellant-saving way.

It urgently must be doubted if something that is economical at one moment will stay economical after that moment.

Hello, nihiladrem,

from my point of view it is not sure that the repulsion force can't be got higher than the individual weights of the magnets - it depends on the weight of the materials the components are made of. If the magnets are electromagnets - which I suspect here - the wires tend to be made of a different material than the cylinder magnetized by them. But next there is a new light material that might be used. This material could make the magnets lighter while it would keep the repulsion force of the heavier version - the nanocarbontubes. They are conductors and so might be used as wires of an electromagnet. They also can be magnetic themselves.

So there might be a way perhaps to light magnets with a repulsion force larger than their weight.



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Post    Posted on: Wed Jul 18, 2007 12:05 pm
Ekkehard Augustin wrote:
from my point of view it is not sure that the repulsion force can't be got higher than the individual weights of the magnets - it depends on the weight of the materials the components are made of. If the magnets are electromagnets - which I suspect here - the wires tend to be made of a different material than the cylinder magnetized by them.
You are quite right, I was deliberately assuming something monolithic. But while you could theoretically get half-mile long electromagnets to separate - you couldn't then reach orbital speeds that way - or indeed speeds approaching that. It appeared to me that the original post really didn't imply an electromagnet, but seemed to be based on the notion that very big magnets would inherently achieve huge speeds as they repelled. That isn't the case of course - making it bigger is just a source of really huge problems.
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But next there is a new light material that might be used. This material could make the magnets lighter while it would keep the repulsion force of the heavier version - the nanocarbontubes. They are conductors and so might be used as wires of an electromagnet. They also can be magnetic themselves.
Note - there's nothing useful you can use as a core in such an electromagnet - e.g. iron doesn't help at very high field-strengths. You just use a big current loop. The loop is held in tension and squashed along it's axis by the magnetic forces. A nice way to think of these forces it is that the whole volume of the magnet is made of little bar magnets which you have arranged together, they're compressed along their length because they attract each other that way - but they're trying to push each other outwards because their poles are touching other like-poles to the sides and that's where the tension comes from.
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So there might be a way perhaps to light magnets with a repulsion force larger than their weight.
I appreciate that light, strong electromagnet materials would allow for separation, but the actual concept of trying to reach orbit that way is so broken, I would not want to hold out any of what would be completely false hope.


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Post SE and Magnets   Posted on: Wed Jul 18, 2007 12:08 pm
@Ekkehard Augustin

Yes its SE are "more efficient", But not cheaper. How many missions can i do with the mass of a SE. the cable needs to be AT LEAST 40,000km long. With a material that does not exist. (note carbon nanotubes have not been made long enough to qualify.) And if we do have such a material then rockets are *also* easier and cheaper. Its like planes vers Trains over oceans. A train across a floating bridge would be more efficient than a plane....we could make the bridge.......

finally SE only get you to one orbital plane. It can't replace rockets outright.

Personally I like SE. If we can make the material with the required strength then one day humanity might build one. But CATS will have happened already before that. The right thing to do for SE is nothing. A material with high strength to weight ratio is so immensely useful that if its possible at all, it will be done.

On the other note: You can get magnets that can support there own weight. But the force goes down to the inverse cube of distance. That is when you double the distance the force drops to 1/8th of the original. It would make a fun toy. But it won't launch anything. Compressed air would do a better job.

We really don't need mega engineering to get to space. In fact if we do it will never be cheap. IMO

And please please remember that launch cost of rockets have almost nothing to do with the cost of fuel and especially LOX which is almost free.


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Post    Posted on: Wed Jul 18, 2007 12:38 pm
Hello, nihiladrem,

I personally didn't have in mind to launch from a surface into an orbit using magnets but imagine that 4thdimension might have had in mind simply to increase the number of people that go to the Moon, to Mars or from one orbit to another - I imagined that because he mentions space travel.

I have problems to imagine to launch from surface into orbit via his magnet-based idea - but the idea might be applied to launch something from one orbit into another or even to into an interplanetatry trajectory (although itmight be required to do a large number of such magnetic repulsion launches).



Hello, delt0r,

Bradley C. Edwards of NASA has investigated Space Elevators in a NIAC study and has in mind a tether 100,000 km long - having in mind that at the end of that tether vehicles could be launched towards Mercury, Moon and the outer planets.

There are several threads about nanocarbontubes in this section. They include links and references to articles that report problems as well as chances. One link or article reported that a method has been found to get infinite long nanocarbontube-tethers. Another one - older if I remember correct - said that it is not possible but the scientific work that got that result obviously - no wonder - seems to have been based on particular assumptions and conditions. Because of this I doubt very much if the scientific result is valid in general. In particlular it does NOT consider what Edwards has in mind in his study - he doesn't use one single one-atom-tether. The study says that the investment into teh space elevator according to that concept would be an investment of $ 15 bio. which would be spread over several years - this investment easyly could be dne by a consortium of several countries and companies.

The problem regarding the orbital plane might be solved via the rotating structures for example. There is an old thread about that idea already but that thread has been turned to quite another topic long ago and shouldn't be revitalized because of other properties also - so I perhaps will initiate a new thread quoting a few posts of mine posted in that old thread.

Since the investment needs to be only once to do a lot of launches the depreciation per launch will be very low - while the investment into one expendable rocket must be depreciated by one launch in total which menas that the depreciation per launch is very much higher than for the space elevator. That is cheaper indeed ecause the amount of ressources to be applied plus the amount of ressources consumed is much higher in the case of the rocket than in the case of Bradley's space elevator. And there is a good chance that this holds for a comparison to reusable rockets also because the space elevator would have access to the abundant amount of solar power etc. in space.

...



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Post    Posted on: Wed Jul 18, 2007 12:38 pm
Hello, nihiladrem,

I personally didn't have in mind to launch from a surface into an orbit using magnets but imagine that 4thdimension might have had in mind simply to increase the number of people that go to the Moon, to Mars or from one orbit to another - I imagined that because he mentions space travel.

I have problems to imagine to launch from surface into orbit via his magnet-based idea - but the idea might be applied to launch something from one orbit into another or even to into an interplanetatry trajectory (although itmight be required to do a large number of such magnetic repulsion launches).



Hello, delt0r,

Bradley C. Edwards of NASA has investigated Space Elevators in a NIAC study and has in mind a tether 100,000 km long - having in mind that at the end of that tether vehicles could be launched towards Mercury, Moon and the outer planets.

There are several threads about nanocarbontubes in this section. They include links and references to articles that report problems as well as chances. One link or article reported that a method has been found to get infinite long nanocarbontube-tethers. Another one - older if I remember correct - said that it is not possible but the scientific work that got that result obviously - no wonder - seems to have been based on particular assumptions and conditions. Because of this I doubt very much if the scientific result is valid in general. In particlular it does NOT consider what Edwards has in mind in his study - he doesn't use one single one-atom-tether. The study says that the investment into teh space elevator according to that concept would be an investment of $ 15 bio. which would be spread over several years - this investment easyly could be dne by a consortium of several countries and companies.

The problem regarding the orbital plane might be solved via the rotating structures for example. There is an old thread about that idea already but that thread has been turned to quite another topic long ago and shouldn't be revitalized because of other properties also - so I perhaps will initiate a new thread quoting a few posts of mine posted in that old thread.

Since the investment needs to be only once to do a lot of launches the depreciation per launch will be very low - while the investment into one expendable rocket must be depreciated by one launch in total which menas that the depreciation per launch is very much higher than for the space elevator. That is cheaper indeed ecause the amount of ressources to be applied plus the amount of ressources consumed is much higher in the case of the rocket than in the case of Bradley's space elevator. And there is a good chance that this holds for a comparison to reusable rockets also because the space elevator would have access to the abundant amount of solar power etc. in space.

...



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Post Beanstalks   Posted on: Wed Jul 18, 2007 1:25 pm
Yes but the consumed resources are cheap, LOX is almost FREE and makes up over half the propellant mass. Nanotubes are not cheap. Hell they cost much more than gold or even platinum. We cannot make the cable yet. Bulk material strength is ALWAYS much lower than its tiny components. Thats why glass fiber is better than glass. Or carbon fiber is better than graphite. Or boron fibers are stronger than boron.

You get dislocations and There are MESURMENTS that show that they can be rather common in nanotubes. Fact is we don't know if such a material can be even made let along economically enough for a SE. As for price estimates...based on a material that DOES NOT EXIST? The infinite cable are lots of short fibers and it was not stronger than traditional carbon fiber (1-2GPa UTS rho ~1500-2000 kg /m3) IIRC (I read a lot of papers). There are no one atom carbon fibers, and if there was they wouldn't have the required strength. Normal carbon fiber bonds are the wrong type (mostly). Thats why folk are excited about nano tubes. They use the strong bond. But bulk strength will have to wait until we have better composite methods. (matrix bonding is still a big problem). Remember that metals are much weaker than pure bond strength suggests because of dislocations.

We haven't even mentioned problems with micrometers that could break some fibers. These fibers are under soo much tension that the energy released could be a very very serious problem and may trigger a cascading failure.

And rockets can be reusable. A 18:1 mass ratio LOX/JET-A1 that is reusable would be the ticket. Propellants are so cheap that tickets will need to be well below 10K per person before we need a "fuel surcharge" on ticket price. It would be particular easy to build if we assume we have nano fibers of 1/2 the strength required for a SE (30GPa, 2000kg/m3, or about 10-30 times better than CC ).

Also the fact remains. We can build rockets NOW. We cannot make the material that we need for a SE. There is zero chance one will be build one within 20 years.

Propellant mass is not your enemy. Costs are.

And the last thing is. How are you going to get the thing there in the first place? You need CATS first....All of that 15B would not even start to cover the cost of launch of even a precursor cable, assuming that the cable was free to make......

A transatlantic bridge/tunnel is more likely in the next 20 years than a SE.


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