Space Elevator or Scramjet?

Tom Kalbfus · 2007-11-14 10:22:44

Which Technology will open up the space frontier to the masses? The Space Elevator or the Scramjet? Which technology would you bank on as being the one key piece that will get us off Earth. There is currently research going on in both fields.

Antius · 2007-11-14 11:22:06

Out of the two, I would have to say scramjet, for the simple reason that we known (roughly) how to manufacture them, whereas no one has a clear idea how to construct a space elevator from carbon nanotubes or flawless diamond filaments.

Actually, it may turn out to be neither of these two options. Other plausible options for dramatically reducing the cost of space access include Big Dumb Booster rockets, SSTO based upon nuclear thermal rocket engines, or bomb propelled Orion spacecraft.

BDBs are my personal favourite. Orion would have tremendous payload capacity, but has a clear disadvantage in terms of radioactive contamination of Earth's atmosphere, making it politically very difficult. nuclear thermal SSTOs would offer similar performance to scramjets but would be less technically challenging, but would also pose significant political challenges.

RedStreak · 2007-11-14 11:25:44

Of the two scramjets are the most likely to be developed first. However a space elevator would really, really open things up to the public since it would bypass the limiting fuel demands needed to reach orbit.

For timelines I'd give scramjets perhaps 20 years to be fully useable, and for space elevators...maybe 50 years earliest 100 years more likely.

Tom Kalbfus · 2007-11-14 12:28:03

But we're already a third of the way there for producing materials strong enough. 100 years? Seems as if everybody in the space community wants to build cathedrals.

I just can't see big dumb boosters making space travel a common everyday experience. You just can't have a daily shuttle to orbit where everytime you throwout the entire spaceship, you just can't.

maxie · 2007-11-14 13:57:13

How about neither of these 2 ?

Number04 · 2007-11-14 15:14:30

Scramjets.

They are cool, and people like cool things that are loud and go fast.

Just look at NASCAR

Yang Liwei Rocket · 2007-11-14 20:34:37

On the scramjet subject, I agree with what publiusr and GCNR once said on this development. The scramjet is fast but not good enough because it does not have the lift, it will provide a very limited payload and very limited results for a very high cost in research and development but it will have other applications such as warfare. The scramjet isn't really good for space travel but will have great military applications such as launching a newest high altitude fighter aircraft that can destroy targets with hypersonic missiles. The scramjet is the sprinter than keeps getting FATTER the more he climbs, scramjet launches need old fashioned rockets before for initial speed buildup and again good old fashioned rockets after for exo-atmospheric flight, so what is their use exactly then other than hitting desired military targets with hypersonic missiles at the scramjets cruise speed?

The space elevator is the ultimate dream, because the technology isn't there the concept is more of a jack and the beanstalk fairytale would be the ultimate megastructure much bigger than the Empire State building or the Great Wall. This would become a clean, safe and reliable method of lifting payloads into space and realizing the dream of people like Konstantin. Future breakthroughs such as Nano-technology may be needed to keep the elevator station in working order.
On a related note
http://www.esa.int/esaCP/SEMUI053R8F_index_0.html
The ESA Foton-M3 now claims a space tether world record

At the moment in time I tend to agree with Maxie

How about neither of these 2 ?

Antius · 2007-11-15 07:28:02

But we're already a third of the way there for producing materials strong enough. 100 years? Seems as if everybody in the space community wants to build cathedrals.
I just can't see big dumb boosters making space travel a common everyday experience. You just can't have a daily shuttle to orbit where everytime you throwout the entire spaceship, you just can't.

Building a space elevator will not provide a cheap access to space for the majority of human beings and there are serious persistant reasons to question whether they are possible at all. The capital costs put the cost of every other human project in the shade and are likely to require a significant fraction of the sustained income of all of humanity to achieve. Then there are the practical concerns of extending diamond fillament or nanotube finbre thousands of kilometres into space. This is not a project that we will see accomplished in our lifetimes or grandchildrens lifetimes. My impression is that many people on this list have a poor basic feel for the scale of the challenges involved in space projects and make unrealistic assumptions on what we are likley to see in our lifetimes.

Scramjets of the other hand are a relatively near-term technology and BDBs are effectively present day technology. In terms of being cheap, it is doubtful that any technology will get you into space for anything less than your entire life savings, not now or in 100 years time. But BDBs take a technology that is at least proven and developed and reduce the cost to reasonable limits by simplifying the technology and making it suitable for common ship-yard grade manufacturing, ie, simple steel construction, pressure-fed ablative engines that are simple and easy to make, liquid (non-cryogenic) fuels that are easy to plumb and work with, etc.

Scramjets approach the problem from a slightly different angle and their higher capital and development costs are presumably offset by extensive reusability. For a BDB, it is often assumed that the lower (booster) stage will be reusable and the upper stage expendable. There are significant technological problems with the idea of producing a reusable vehicle capable of reaching orbital velecities. This relates both to the complexity of a vehicle capable of achieving sufficient mass ratios and the extensive maintenance that is required between launches.

cIclops · 2007-11-15 07:38:59

Building a space elevator will not provide a cheap access to space for the majority of human beings and there are serious persistant reasons to question whether they are possible at all. The capital costs put the cost of every other human project in the shade and are likely to require a significant fraction of the sustained income of all of humanity to achieve. Then there are the practical concerns of extending diamond fillament or nanotube finbre thousands of kilometres into space.

Estimates of the cost of building the SE are in the $10 billion range, by today's standards that is almost reasonable. Of course such estimates are based on the available of a fiber strong enough but there has been much progress towards such a material. The idea is to launch one fiber and use that to lift all the others, rather like building a suspension bridge. An Ares V for example could deliver the 50 tons or so of fiber to GEO for less than $1 billion. Even if these estimates are wrong by a factor of 10 (which is quite likely) $100 billion is less than 1% of world GDP currently at $50 trillion.

See the latest news about CNT fibers here

(This topic should be in the Transportation forum, it may move soon)

Tom Kalbfus · 2007-11-15 09:26:13

On the scramjet subject, I agree with what publiusr and GCNR once said on this development. The scramjet is fast but not good enough because it does not have the lift, it will provide a very limited payload and very limited results for a very high cost in research and development but it will have other applications such as warfare. The scramjet isn't really good for space travel but will have great military applications such as launching a newest high altitude fighter aircraft that can destroy targets with hypersonic missiles. The scramjet is the sprinter than keeps getting FATTER the more he climbs, scramjet launches need old fashioned rockets before for initial speed buildup and again good old fashioned rockets after for exo-atmospheric flight, so what is their use exactly then other than hitting desired military targets with hypersonic missiles at the scramjets cruise speed?

The space elevator is the ultimate dream, because the technology isn't there the concept is more of a jack and the beanstalk fairytale would be the ultimate megastructure much bigger than the Empire State building or the Great Wall. This would become a clean, safe and reliable method of lifting payloads into space and realizing the dream of people like Konstantin. Future breakthroughs such as Nano-technology may be needed to keep the elevator station in working order.
On a related note
http://www.esa.int/esaCP/SEMUI053R8F_index_0.html
The ESA Foton-M3 now claims a space tether world record
At the moment in time I tend to agree with Maxie
How about neither of these 2 ?

I've heard that they've achieved materials with one third the required strength, that is for a stationary Space Elevator over the equator in a 24 hour orbit, but lets look at what can be done with that material. What about a shorter Space elevator thats in an 8-hour orbit over the equator? The bottom part of such an elevator could terminate just above the atmosphere, it would circle the Earth once every 8 hours, this velocity is only 3/16th the required velocity of a low Earth orbit that circles the Earth every 90 minutes, this comes to about MACH 4.69, this is within easy reach of a scramjet.

My plan would therefore be this, take an Ares V rocket, launch a spool of this carbon nanotube ribbon into an 8-hour orbit over the equator, then unspool it so that the bottom of the ribbon ends at 115 km above the Equator. Build a Scramjet that can reach MACH 7, a speed which I am told is well achievable, it maybe takes off using conventional jets or with rocket assist, and then achieves MACH 7, it then pulls out of the atmosphere in a suborbital Arch. Onboard rockets bring it into position so it can grapple with the tether, and a climber attached to the grapple then ascends the ribbon hauling the scramjet up with it. A counterweight and the mass of the ribbon prevent the scramjet from dragging the ribbon into the atmosphere as it ascends, so it would seem that the scramjet and the Space Elevator can meet somewhere in the middle.

Tom Kalbfus · 2007-11-15 09:59:23

But we're already a third of the way there for producing materials strong enough. 100 years? Seems as if everybody in the space community wants to build cathedrals.
I just can't see big dumb boosters making space travel a common everyday experience. You just can't have a daily shuttle to orbit where everytime you throwout the entire spaceship, you just can't.
Building a space elevator will not provide a cheap access to space for the majority of human beings and there are serious persistant reasons to question whether they are possible at all. The capital costs put the cost of every other human project in the shade and are likely to require a significant fraction of the sustained income of all of humanity to achieve. Then there are the practical concerns of extending diamond fillament or nanotube finbre thousands of kilometres into space. This is not a project that we will see accomplished in our lifetimes or grandchildrens lifetimes. My impression is that many people on this list have a poor basic feel for the scale of the challenges involved in space projects and make unrealistic assumptions on what we are likley to see in our lifetimes.
Scramjets of the other hand are a relatively near-term technology and BDBs are effectively present day technology. In terms of being cheap, it is doubtful that any technology will get you into space for anything less than your entire life savings, not now or in 100 years time. But BDBs take a technology that is at least proven and developed and reduce the cost to reasonable limits by simplifying the technology and making it suitable for common ship-yard grade manufacturing, ie, simple steel construction, pressure-fed ablative engines that are simple and easy to make, liquid (non-cryogenic) fuels that are easy to plumb and work with, etc.
Scramjets approach the problem from a slightly different angle and their higher capital and development costs are presumably offset by extensive reusability. For a BDB, it is often assumed that the lower (booster) stage will be reusable and the upper stage expendable. There are significant technological problems with the idea of producing a reusable vehicle capable of reaching orbital velecities. This relates both to the complexity of a vehicle capable of achieving sufficient mass ratios and the extensive maintenance that is required between launches.

That is an example of a 20th century, "it can't be done" mindset. No one has really attempted to build a space elevator, there is a great difference between "It hasn't been done" and "it can't be done".

For me, I find it unacceptable to have to live in the "20th Century" for the rest of my life no matter that the calendar date may actually be. The reason for the lack of progress is space travel technologies is that people aren't trying things out, they give up on projects before they achieve results, or they get distracted and move on to other things before they complete the project they are working on, and some how they always seem to fall short before they achieve something that will provide cheap access to space.

I can just imagine the way you are thinking, you are thinking that:
a) A space elevator will provide cheap access to space.
b) Cheap access to space is impossible.
So therefore
c) A Space elevator must be impossible.

You are not sure how or why it is impossible, but you sound reasonably assured that whatever avenue we try to obtain cheap access to space, something will rise up to stop us. As if there is some unwritten rule that prevents the majority of us from going into space. Such a self-defeating attitude is part of what is keeping us out of space.

The 21st century has only just begun and already you are proscribing the limits of that century's technologies. It a way that's a very arrogant attitude, as if some late Victorian in 1907 deems himself the expert of all things possible in the 20th century. This attitude doesn't really say much for all the scientists and engineers, most of whom are yet to be born, who are going to try to figure this all out. I figure with your attitude, their is no point in hiring them if we simply have you to tell us that it can not be done. After all, why waste time and resource on efforts that you say will fail? We've got better things to spend out money on than innovation, right? You tell us the research won't go anywhere, so based on your authority, what self-respecting investor would invest in a technology company?

Yeah, I'm being a little sarcastic here. All throughout history, there have always been naysayers, people who say "Man can't fly", or that "light bulb won't work" and tell Thomas Edison to quite wasting his time and resources on a project that is doomed to failue.

I think SpaceShipOne has shown us that there is no magical barrier that always thwarts us from getting into space cheaply and that NASA doesn't always know everything about the subject, but people must take risks to get there, rather than comfort themselves with self-defeating reassurances of failuer that prevent them from trying.

The old methodology of building big expensive liquid fueled rockets that sit on a launch pad, may get a few people to Mars, but it will accomplish very little beyond that. What I want is changing the way we live as a species, not just adding a few more pictures to our science textbooks.

Antius · 2007-11-15 11:19:21

But we're already a third of the way there for producing materials strong enough. 100 years? Seems as if everybody in the space community wants to build cathedrals.
I just can't see big dumb boosters making space travel a common everyday experience. You just can't have a daily shuttle to orbit where everytime you throwout the entire spaceship, you just can't.
Building a space elevator will not provide a cheap access to space for the majority of human beings and there are serious persistant reasons to question whether they are possible at all. The capital costs put the cost of every other human project in the shade and are likely to require a significant fraction of the sustained income of all of humanity to achieve. Then there are the practical concerns of extending diamond fillament or nanotube finbre thousands of kilometres into space. This is not a project that we will see accomplished in our lifetimes or grandchildrens lifetimes. My impression is that many people on this list have a poor basic feel for the scale of the challenges involved in space projects and make unrealistic assumptions on what we are likley to see in our lifetimes.
Scramjets of the other hand are a relatively near-term technology and BDBs are effectively present day technology. In terms of being cheap, it is doubtful that any technology will get you into space for anything less than your entire life savings, not now or in 100 years time. But BDBs take a technology that is at least proven and developed and reduce the cost to reasonable limits by simplifying the technology and making it suitable for common ship-yard grade manufacturing, ie, simple steel construction, pressure-fed ablative engines that are simple and easy to make, liquid (non-cryogenic) fuels that are easy to plumb and work with, etc.
Scramjets approach the problem from a slightly different angle and their higher capital and development costs are presumably offset by extensive reusability. For a BDB, it is often assumed that the lower (booster) stage will be reusable and the upper stage expendable. There are significant technological problems with the idea of producing a reusable vehicle capable of reaching orbital velecities. This relates both to the complexity of a vehicle capable of achieving sufficient mass ratios and the extensive maintenance that is required between launches.
That is an example of a 20th century, "it can't be done" mindset. No one has really attempted to build a space elevator, there is a great difference between "It hasn't been done" and "it can't be done".
For me, I find it unacceptable to have to live in the "20th Century" for the rest of my life no matter that the calendar date may actually be. The reason for the lack of progress is space travel technologies is that people aren't trying things out, they give up on projects before they achieve results, or they get distracted and move on to other things before they complete the project they are working on, and some how they always seem to fall short before they achieve something that will provide cheap access to space.
I can just imagine the way you are thinking, you are thinking that:
a) A space elevator will provide cheap access to space.
b) Cheap access to space is impossible.
So therefore
c) A Space elevator must be impossible.
You are not sure how or why it is impossible, but you sound reasonably assured that whatever avenue we try to obtain cheap access to space, something will rise up to stop us. As if there is some unwritten rule that prevents the majority of us from going into space. Such a self-defeating attitude is part of what is keeping us out of space.
The 21st century has only just begun and already you are proscribing the limits of that century's technologies. It a way that's a very arrogant attitude, as if some late Victorian in 1907 deems himself the expert of all things possible in the 20th century. This attitude doesn't really say much for all the scientists and engineers, most of whom are yet to be born, who are going to try to figure this all out. I figure with your attitude, their is no point in hiring them if we simply have you to tell us that it can not be done. After all, why waste time and resource on efforts that you say will fail? We've got better things to spend out money on than innovation, right? You tell us the research won't go anywhere, so based on your authority, what self-respecting investor would invest in a technology company?
Yeah, I'm being a little sarcastic here. All throughout history, there have always been naysayers, people who say "Man can't fly", or that "light bulb won't work" and tell Thomas Edison to quite wasting his time and resources on a project that is doomed to failue.
I think SpaceShipOne has shown us that there is no magical barrier that always thwarts us from getting into space cheaply and that NASA doesn't always know everything about the subject, but people must take risks to get there, rather than comfort themselves with self-defeating reassurances of failuer that prevent them from trying.
The old methodology of building big expensive liquid fueled rockets that sit on a launch pad, may get a few people to Mars, but it will accomplish very little beyond that. What I want is changing the way we live as a species, not just adding a few more pictures to our science textbooks.

You believe that building a space elevator is achievable in the near term. I have strong doubts that (1) Materials science is capable of yielding a sufficiently strong carbon fibre nanotube that is 36,000km long and that (2) The capital costs will be affordable in the near term.

I am not a luddite and I try not to be over-conservative.

Tom Kalbfus · 2007-11-15 16:13:12

And you think 100 years of the creative and inventive talents of a whole bunch of engineers and scientists will fail to solve this problem?

I'm optimistic about the Space Elevator in part because its success, unlike Apollo, is not entirely in the hands of Government. We don't have to fight the political battles in Congress and the Senate to secure funding for nanotube research and materials science, there are alot of reasons to fund it, the material has many uses, as a consequence, finding investors should not be that hard. The Pentagon is also interested in this material, for one thing, it would make excellent armor for soldiers. Its not just a matter of whether people are interested in going into space. Wars can be won or lost depending on the personal armor that is worn. Our task is the remove the excuses that naysayers have for not going into space. The people investing in SpaceShipOne simply ignored them.

The problem I find with great big liquid-fueled boosters is that Congress can always get "Hippie Syndrome" and pull the plug on the operation, like they did during the Apollo Years, and all that equipment and hardware we developed gets wasted. One of the reasons I don't want to wait until 2031 to rebuild the hardware we had in the 1960s. I think it should all be done in ten years. If we could do it in 10 years in the 1960s we should do it again today rather than slowing things down and wasting time in an effort to save money from our annual expenditures. My schedule is to get all the Moon-Mars stuff dine in the first ten years, and then use that program as an incentive for private industry to foster development of an improvement over that obsolete throwaway "big booster" technology we use to get things into space. My main problem with the Shuttle is our inability to walk away from a failure, we might as well stuck with the Saturn V, and it doesn't take a genius to reproduce technology we've already had. But going around in circles and not making progress in space transportation is not the direction I like to see us heading in for the rest of my life. Why after 50 years don't we have cheaper access to space? What are the excuses? You'd think after 50 years of working on something we would have made a little progress, I take that as a sign that we were doing something wrong. the answer isn't just to continue doing more of it wrong and have more patience that someday our distant great great great great great grandchildren may someday be able to achieve orbit by warping the manifold of space time.

Commodore · 2007-11-15 16:32:50

I think scram jets will do it first, and is vital to pushing development of the other. If airline style Earth to LEO service can be established and the price of a ticket can be brought down from the current $200K to something more reasonable, then normal people will actually do it. And those normal people will demand a destination, which will push space development that only a space elevator can provide.

Admiral_Ritt · 2007-11-15 18:22:02

I think the first nation that figures out how to combine
Scramjet tech with Near Equatorial Sled Launch facilities will win the
Space race.

Boeing's Sea-Launch System can launch I believe 35% more mass into
LOE compared with Higher latitude launches. Do not sneer at 35%, because it conversly means that it requires 35% less fuel for the mass
launch.

All you need is an island near the equator where you can lay 6 miles of
Track. If you can run up your Sled/booster to 5.000 mph on the rail a
scramjet becomes much more efficient. (and if you can't make such a booster reusable, then you're fired) With a take off angle of
20 degrees Most of that orbital energy will really help things.

The Space Elevator Reminds me of fusion reactors, theoretically possible
but darn the engineering is getting in the way. (did anyone notice that
it is very easy to create space debris to cripple anything up there in LEO
including a tenous tether)

Dayton Kitchens · 2007-11-15 19:06:49

I look at it this way.

One way or another, to build a space elevator you will have to get literally hundreds of thousands of tons of hardware into orbit.

To do that, we'll have to be able to boost hundreds of thousands of tons up there ECONOMICALLY.

Which means at that point, we'll have relatively cheap surface to orbit transport already.

Which will dramatically undermine the reasons for building an elevator in the first place.

Tom Kalbfus · 2007-11-15 22:00:59

I look at it this way.
One way or another, to build a space elevator you will have to get literally hundreds of thousands of tons of hardware into orbit.
To do that, we'll have to be able to boost hundreds of thousands of tons up there ECONOMICALLY.
Which means at that point, we'll have relatively cheap surface to orbit transport already.
Which will dramatically undermine the reasons for building an elevator in the first place.

No, not really.

Think about it. Once a space elevator is up, it can lift another 100,000 tons into orbit, and then you'd have two space elevators, those two space elevators can then lift another 200,000 tons into orbit in the same amount of time, and then you'd have four space elevators. Those four space elevators would then lift 400,000 tons into orbit and then you'd have 8 space elevators, those 8 space elevators would lift 800,000 tons into orbit and then you'd have 16 space elevators, this progression goes on and on until you have enough space elevators to make access to space cheap for everyone. I think it would be well worth the cost of lifting that initial 100,000 tons into orbit, don't you think? But who said the initial set up would have to be 100,000 tons? Make it thinner and then you'd have a less capable space elevator that can lift 50,000 tons, make it thinner still and you'd have one which could lift 25,000 tons. I don't know what the minimum practical mass of the very first space elevator would be, but it is a boot strapping process to get all the others up their, you only just have to worry about the first one. Remember, unlike rockets, space elevators don't get used up when they do their lifting, so long as you don't over stress them at any one time, they can go on and on lifting more things into orbit, and more space elevators can then be lowered down from the sky. I think this idea is alot better than scramjets if they could be made to work.

I imagine a scramjet would undergo alot of wear and tear by traveling through the atmosphere at hypersonic speeds, they would be maintenance hogs when compared to other aircraft, I'm sure of that. Space Elevators, at least the conventional "beanstalk" kind remain stationary relative to the surface of the Earth, it is the Earth's rotation that keeps them upright, and the Earth has alot of rotational momentum in it. You could easily lift all the human beings off of Earth and as many belongings they'd care to bring with them without noticably changing the Earth's rotation rate. Space Elevators could easily be the salvation of the Earth, that and high taxes, meddlesome intrusive governments, and the low taxes and freedom of space would serve to drive most humans into space, as that is where the economic opportunities would lie, and people would bring little pieces of Earth with them, recreating Earth's environment in many different artificial habitats throughout the Solar System. That is the objective, getting the Earth to reproduce, Terraforming Mars and Venus also fall into this category.

Terraformer · 2007-11-16 06:12:52

Neither of them. Helium balloon launchings and Magnetic rail guns ae the way to go. The space elevator idea could be used to lift cargo, people, and craft up to a balloon in suborbital space whee a magnetic rail gun would launch them into orbit using a booster for the final bit.

Antius · 2007-11-16 08:24:24

Neither of them. Helium balloon launchings and Magnetic rail guns ae the way to go. The space elevator idea could be used to lift cargo, people, and craft up to a balloon in suborbital space whee a magnetic rail gun would launch them into orbit using a booster for the final bit.

Interesting idea. The obvious difficulty of using a mass driver in the Earth's atmosphere is the heat and pressure wave generated, as the projectile plows through the air. How far up would we need to go before this effect would be tollerably easy to design around?

One problem with attempting to tether a balloon in the upper atmosphere is the mass of the cable needed to hold it is place. If we can build a carbon fibre 50 kilometres long, why not go the whole hog and build one 36,000km long?

Terraformer · 2007-11-16 08:30:22

Or we could just use cheap suborbital scramjet like craft to get there. Or skybreaker airships.

Tom Kalbfus · 2007-11-16 09:01:55

Neither of them. Helium balloon launchings and Magnetic rail guns ae the way to go. The space elevator idea could be used to lift cargo, people, and craft up to a balloon in suborbital space whee a magnetic rail gun would launch them into orbit using a booster for the final bit.
Interesting idea. The obvious difficulty of using a mass driver in the Earth's atmosphere is the heat and pressure wave generated, as the projectile plows through the air. How far up would we need to go before this effect would be tollerably easy to design around?
One problem with attempting to tether a balloon in the upper atmosphere is the mass of the cable needed to hold it is place. If we can build a carbon fibre 50 kilometres long, why not go the whole hog and build one 36,000km long?

By making the Space Elevator Non-stationary, you can make it shorter. For example, a 747 can go halfway around the World in 12 hours, that way it can meet up with the dangling end of a Space Elevator in a 12-hour orbit. If the 747 is a cargo jet, it can open up the payload bay doors and the cargo inside can be attached to the Space Elevator car, and the car would hoist up the cargo out of the cargo bay and into space. With faster airplanes, you can have shorter space elevators.

Antius · 2007-11-16 09:16:07

Neither of them. Helium balloon launchings and Magnetic rail guns ae the way to go. The space elevator idea could be used to lift cargo, people, and craft up to a balloon in suborbital space whee a magnetic rail gun would launch them into orbit using a booster for the final bit.
Interesting idea. The obvious difficulty of using a mass driver in the Earth's atmosphere is the heat and pressure wave generated, as the projectile plows through the air. How far up would we need to go before this effect would be tollerably easy to design around?
One problem with attempting to tether a balloon in the upper atmosphere is the mass of the cable needed to hold it is place. If we can build a carbon fibre 50 kilometres long, why not go the whole hog and build one 36,000km long?
By making the Space Elevator Non-stationary, you can make it shorter. For example, a 747 can go halfway around the World in 12 hours, that way it can meet up with the dangling end of a Space Elevator in a 12-hour orbit. If the 747 is a cargo jet, it can open up the payload bay doors and the cargo inside can be attached to the Space Elevator car, and the car would hoist up the cargo out of the cargo bay and into space. With faster airplanes, you can have shorter space elevators.

Not quite sure that I understand this. Are you describing a tether, with one end in space and the other within the Earths atmosphere?

Tom Kalbfus · 2007-11-16 11:18:46

Yes, the tether has one end in space, and the other end in Earth's Atmosphere, but not attached to the Earth, it would descend to about the typical cruising altitude of a 747. The vehicle that meets up with it would be a cargo jet though. You could have a passenger module inside or another module that hooks to the car of the space elevator and is raised up into space. There is of course the problem of atmospheric drag, the tether would slice through the atmosphere. I think that can be counteracted with a counterweight on the other end. The tether is long enough to use some effects of Earth's magnetic field for propulsion. In any case the elevator would orbit the Earth at twice the Earth's rotation rate, this means it would complete an orbit once every 12 hours along the equator, it would pass over the same spot on Earth once every 24 hours, this is about the speed of a typical passenger jet. If you had a more advanced jet, such as a scramjet for instance, or even SpaceShipOne, the lower end of the tether would not have to drag through the atmosphere. The aircraft would dock with the tether in space.

Terraformer · 2007-11-16 12:32:29

Which orbit would the sattelite end be in?

Austin Stanley · 2007-11-16 18:25:41

Of the two options I favor the space elevator. It is true that the material technology is not there yet, but solid progress is being made in this area. Materials science is one of those things that kinds of sneaks up on yah. Often times we don't realize the revolution that it happening until it has already taken place. Such was the case with plastics, aluminum, fiberglass, and now carbon fibers. These sorts of things slip into our lives casually as the technologies mature and the prices drop, often so subtly we don't notice them. Something similar will probably happen with buckytubes and other advanced materials. In any case if keep along at the same rate of improvement in materials technology we have been a space elevator will eventually be possible.

For scramjets I am not so optimistic. While I have little doubt that they can be built, I doubt they will ever revolutionize space access. They are two complex, to heavy, and two demanding in engineering terms to work for space. As others have said their most likely application is in missiles.

In any case if a space elevator CAN be built it will revolutionize space access, no doubt at all. Access to orbit will become as cheap as it could realisticly go. A scramjet has no chance of revolutionizing space in the same way.

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#1 2007-11-14 10:22:44

Re: Space Elevator or Scramjet?

#2 2007-11-14 11:22:06

Re: Space Elevator or Scramjet?

#3 2007-11-14 11:25:44

Re: Space Elevator or Scramjet?

#4 2007-11-14 12:28:03

Re: Space Elevator or Scramjet?

#5 2007-11-14 13:57:13

Re: Space Elevator or Scramjet?

#6 2007-11-14 15:14:30

Re: Space Elevator or Scramjet?

#7 2007-11-14 20:34:37

Re: Space Elevator or Scramjet?

#8 2007-11-15 07:28:02

Re: Space Elevator or Scramjet?

#9 2007-11-15 07:38:59

Re: Space Elevator or Scramjet?

#10 2007-11-15 09:26:13

Re: Space Elevator or Scramjet?

#11 2007-11-15 09:59:23

Re: Space Elevator or Scramjet?

#12 2007-11-15 11:19:21

Re: Space Elevator or Scramjet?

#13 2007-11-15 16:13:12

Re: Space Elevator or Scramjet?

#14 2007-11-15 16:32:50

Re: Space Elevator or Scramjet?

#15 2007-11-15 18:22:02

Re: Space Elevator or Scramjet?

#16 2007-11-15 19:06:49

Re: Space Elevator or Scramjet?

#17 2007-11-15 22:00:59

Re: Space Elevator or Scramjet?

#18 2007-11-16 06:12:52

Re: Space Elevator or Scramjet?

#19 2007-11-16 08:24:24

Re: Space Elevator or Scramjet?

#20 2007-11-16 08:30:22

Re: Space Elevator or Scramjet?

#21 2007-11-16 09:01:55

Re: Space Elevator or Scramjet?

#22 2007-11-16 09:16:07

Re: Space Elevator or Scramjet?

#23 2007-11-16 11:18:46

Re: Space Elevator or Scramjet?

#24 2007-11-16 12:32:29

Re: Space Elevator or Scramjet?

#25 2007-11-16 18:25:41

Re: Space Elevator or Scramjet?

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