Space Elevators and Other Alternatives

[Nano-Passion]

So far it seems that space exploration/future tourism/etc has come to a halt due to its expenses.

So what is the status of cheaper alternatives to escaping the gravitational pull from the earth? There was a lot of talk about space elevators but nothing seems to get done (I hope I'm wrong).

 

[russ_watters]

Space elevators are a good idea in theory, but at the moment, no one really knows if they can be built and the expense of the initial construction would make for a long payback in launch cost savings. So no, not much is being done.

 

[mistergrinch]

Well the folks at Project Orion (nuclear fission propulsion) figured out a cheaper way to get out of the gravity well and explore the solar system 50 years ago, but they also calculated that each launch would kill several people on average. Centuries ago this wouldn't have stopped anyone form exploring the oceans. Today we want the universe without risk and without offending anyone, which isn't going to cut it for manned space exploration! We are living in a timid, "can't do", politically correct civilization, and the lack of results compared to previous decades and centuries of exploration speak for themselves...

 

[Nano-Passion]

Space elevators are a good idea in theory, but at the moment, no one really knows if they can be built and the expense of the initial construction would make for a long payback in launch cost savings. So no, not much is being done.

I think its one of those where we need strong leadership to get it started. Thats something that we don't have though, because who is the leader anyways?

Its pretty sad that the world keeps thinking about the now, and postpones the future... Because postponing the future is the easiest thing to do. Why worry about it now when the future can worry about it for us? Phew, that's a big load off our shoulders, its not like we are going to benefit off it anyways in our lifetime.

^^ This is what slows progress, but its society's natural tendency I guess..

 

[russ_watters]

Put off what exactly? Regardless, there are time horizons beyond which it isn't useful to try to plan. If there is no compelling need for the next 50 years or so, there are much more immediate needs to spend our money on.

 

[Nano-Passion]

Put off what exactly? Regardless, there are time horizons beyond which it isn't useful to try to plan. If there is no compelling need for the next 50 years or so, there are much more immediate needs to spend our money on.

Puting off space exploration to be exact.

Yes, urgent needs; but there are also important needs in the long-run. If society simply looks in the short term then we won't be going very far now would be. Just look at politics; they are constantly attending to urgent needs and leaving other problems for the future generations (like our stupendous US debt...)

But perhaps I am quite bias, not everyone is interested in space exploration... but that's likely because they won't be there to witness it.

 

[russ_watters]

Puting off space exploration to be exact.

Yes, urgent needs; but there are also important needs in the long-run. If society simply looks in the short term then we won't be going very far now would be. Just look at politics; they are constantly attending to urgent needs and leaving other problems for the future generations (like our stupendous US debt...)

But perhaps I am quite bias, not everyone is interested in space exploration... but that's likely because they won't be there to witness it.

Bias is only relevant if it prevents you from thinking logically: I'm also a huge fan of manned spaceflight, but that doesn't mean I think it is a practical need. Ie, what long-term need do you see for manned space exploration that outweighs dealing with the US national debt (the two pursuits are essentially mutually exclusive)?

 

[Carrock]

Well the folks at Project Orion (nuclear fission propulsion) figured out a cheaper way to get out of the gravity well and explore the solar system 50 years ago, but they also calculated that each launch would kill several people on average. Centuries ago this wouldn't have stopped anyone form exploring the oceans. Today we want the universe without risk and without offending anyone, which isn't going to cut it for manned space exploration! We are living in a timid, "can't do", politically correct civilization, and the lack of results compared to previous decades and centuries of exploration speak for themselves...

We're willing to let minimally trained people drive cars and frequently kill children and other non drivers which I suppose is brave, "can do" and politically incorrect.
More seriously, Isaac Newton designed the first buildable satellite launcher ( a gun on a mountaintop ) but no one tried to launch a satellite until the available technology made it practical.
With present technology, there are surely far more cost effective ways of spending money on spaceflight.

Bias is only relevant if it prevents you from thinking logically: I'm also a huge fan of manned spaceflight, but that doesn't mean I think it is a practical need. Ie, what long-term need do you see for manned space exploration that outweighs dealing with the US national debt (the two pursuits are essentially mutually exclusive)?

I'd say the two are both (almost) impossible - they involve increased taxes...
People spend money on things like education, entertainment and tourism for which a utilitarian would say they have no long term need.
If enough people wanted the government to spend more money on (manned) space exploration why should it be required to demonstrate long-term need?

In a republic of wolves and squirrels, wolves would eat acorns.

 

[Vanadium 50]

More seriously, Isaac Newton designed the first buildable satellite launcher ( a gun on a mountaintop ) but no one tried to launch a satellite until the available technology made it practical.

That won't work. A gun alone cannot put a satellite into orbit.

 

[JaredJames]

Well the folks at Project Orion (nuclear fission propulsion) figured out a cheaper way to get out of the gravity well and explore the solar system 50 years ago, but they also calculated that each launch would kill several people on average. Centuries ago this wouldn't have stopped anyone form exploring the oceans. Today we want the universe without risk and without offending anyone, which isn't going to cut it for manned space exploration! We are living in a timid, "can't do", politically correct civilization, and the lack of results compared to previous decades and centuries of exploration speak for themselves...

And if you were one of the people told you had to die because they wanted to get to space?

Complete non-sense.

There is a difference between the risk involved once you're in space and exploring to risking the lives of people on Earth simply to get you there.

 

[Andy Resnick]

So far it seems that space exploration/future tourism/etc has come to a halt due to its expenses.

So what is the status of cheaper alternatives to escaping the gravitational pull from the earth? There was a lot of talk about space elevators but nothing seems to get done (I hope I'm wrong).

Your thesis is flawed- on what basis is a space elevator a cheaper technology? It does not exist- you must account for the cost to develop, test, and verify the device before using it.

This is also true of all the other unbuilt "cheaper" alternatives. How much time and money is required to reduce those fanciful ideas into practice?

And, while all that activity is going on, what should happen in the meantime- should existing activities be put on hold? Or are you advocating for NASA's budgets to be doubled/tripled for the next, say, 50 years? And what happens if the magic technology you are advocating does not meet it's promise? What will you say to the taxpayers then?

If you want to be taken seriously, you need to do a better job of accounting for all these expenses/possibilities. Only then can you argue that one method is cheaper than another (already existing and proven) method.

 

[russ_watters]

If enough people wanted the government to spend more money on (manned) space exploration why should it be required to demonstrate long-term need?

Sure, we can do whatever we want, but why would people want to? You implied that space travel was a long-term need. If it's just something we would do for fun, then there is no need for it and you'll have a hard time convincing people to spend trillions of dollars on it when there are things we actually need to spend that money on.

 

[sophiecentaur]

The only reason for any government to decide to put more people, further out into Space would be a military one. That is the only excuse that can be used for such vast expenditure - it was last time and it would be next time. Hopefully we won't be in a post WW2 -type situation for a long long time.
The high tech solution to many problems is often not really the best - just the sexiest. The on-going situation with the stricken Japanese Nuclear Power Stations is a chilling example of just where Technology can take us. Ignoring the potential cost in lives and health, just how much per kWh does this correspond to, in real terms? There will be possible parallel risks in a project such as the elevator but will they be acknowledged? I doubt it.
Meanwhile, we have billions of humans living in really dire circumstances. But that's a different budget; a different compartment in our minds.

 

[ladykrimson]

So far it seems that space exploration/future tourism/etc has come to a halt due to its expenses.

So what is the status of cheaper alternatives to escaping the gravitational pull from the earth? There was a lot of talk about space elevators but nothing seems to get done (I hope I'm wrong).

To actually return to the topic at hand, I believe there are a few problems that need to be resolved before a space elevator can come to be. The space elevator is dependent on a very long cable, one side connected to Earth and one side connected to a station in orbit. This tether would have to be 24,000 miles long. Should it ever snap, a cable that long could do some serious damage on Earth. Radiation exposure for travelers passing through the Van Allen radiation belt is another concern. Also, space debris and micrometeors could damage the tether. Orbital objects that are not in sync and below the maximum altitude of the cable would eventually collide with it. And finally, the materials desired for the tether have not been discovered yet.

 

[Carrock]

That won't work. A gun alone cannot put a satellite into orbit.

As far as I recall, Newton proposed to fire a satellite horizontally into orbit from the top of (the world's highest?) mountain.
If you neglect air friction, it's only necessary to ensure the gun is removed before the satellite comes back round.
If you claim air friction and perturbation means it's not truly in orbit, then the same is true of the ISS.

Sure, we can do whatever we want, but why would people want to? You implied that space travel was a long-term need. If it's just something we would do for fun, then there is no need for it and you'll have a hard time convincing people to spend trillions of dollars on it when there are things we actually need to spend that money on.

My point was that we don't "need" to do most of the things we spend money on and that includes manned space flight.
I doubt much of the money Richard Nixon saved by committing America not to return to the moon before 2000 was spent on things people "needed".

 

[JaredJames]

As far as I recall, Newton proposed to fire a satellite horizontally into orbit from the top of (the world's highest?) mountain.
If you neglect air friction, it's only necessary to ensure the gun is removed before the satellite comes back round.
If you claim air friction and perturbation means it's not truly in orbit, then the same is true of the ISS.

It takes the ISS orbiting at nearly 30,000km/h to remain in an average orbit of 350km. Now take the height of everest (29km) and calculate the speed required to achieve one orbit. (Here's a hint, it's unachievable by a gun).

I doubt much of the money Richard Nixon saved by committing America not to return to the moon before 2000 was spent on things people "needed".

That will need backing up, either way.

 

[russ_watters]

As far as I recall, Newton proposed to fire a satellite horizontally into orbit from the top of (the world's highest?) mountain.
If you neglect air friction, it's only necessary to ensure the gun is removed before the satellite comes back round.

I'm pretty sure that V50 was talking about reality. A 400 year old thought experiment is a useful learning tool, but it doesn't have much to do with reality.

If you claim air friction and perturbation means it's not truly in orbit, then the same is true of the ISS.

Not really. A gun on mount Everest would probably not be able to even get it's projectile back to itself (to complete one orbit) because of that friction and certainly couldn't do two. The ISS can orbit just fine for weeks (months?) without a boost.

...and as said above, that's even assuming it could be built to accelerate a projectile that fast...and not destroy the projectile!

My point was that we don't "need" to do most of the things we spend money on and that includes manned space flight.
I doubt much of the money Richard Nixon saved by committing America not to return to the moon before 2000 was spent on things people "needed".

On the orders of magnitude of cost we're discussing - a trillion dollars or more - the only comparable components of the US budget are things we need to spend money on:
1. Healtcare.
2. Retirement savings.
3. Interest on the debt.
4. The military.

There can certainly be debate about how much and how to spend on these things, but the point is that an exploration trip to Mars, for example, would have a major impact on our ability to spend money on these needs.

 

[sophiecentaur]

If that list is in order of 'preference' or 'urgency' then number 4 could very easily get up to number 1, just like it did in the 50s. Then, if military considerations come into play and another JFK put up the challenge, all your spending money dollars could go, literally, up the shute! Though, as a weapon, perhaps such a big target would be a bit vulnerable. SO perhaps not.

 

[Carrock]

I'm pretty sure that DH was talking about reality. A 400 year old thought experiment is a useful learning tool, but it doesn't have much to do with reality. Not really. A gun on mount Everest would probably not be able to even get it's projectile back to itself (to complete one orbit) because of that friction and certainly couldn't do two. The ISS can orbit just fine for weeks (months?) without a boost.

...and as said above, that's even assuming it could be built to accelerate a projectile that fast...and not destroy the projectile! On the orders of magnitude of cost we're discussing - a trillion dollars or more - the only comparable components of the US budget are things we need to spend money on:
1. Healtcare.
2. Retirement savings.
3. Interest on the debt.
4. The military.

There can certainly be debate about how much and how to spend on these things, but the point is that an exploration trip to Mars, for example, would have a major impact on our ability to spend money on these needs.

It takes the ISS orbiting at nearly 30,000km/h to remain in an average orbit of 350km. Now take the height of everest (29km) and calculate the speed required to achieve one orbit. (Here's a hint, it's unachievable by a gun).


That will need backing up, either way.

There is plenty of evidence a space gun is feasible but not necessarily economic. eg
http://www.astronautix.com/lvs/maret2g1.htm" .
There are certainly economic limits to the velocity a gun can impart, but I'd be very surprised if you can find any theoretical limit.

If you claim air friction and perturbation means it's not truly in orbit, then the same is true of the ISS.

A gun on mount Everest would probably not be able to even get it's projectile back to itself (to complete one orbit) because of that friction and certainly couldn't do two. The ISS can orbit just fine for weeks (months?) without a boost.

I agree 100% with this.
Please specify for how long an object has to be traveling at orbital velocity before it is in orbit.

I doubt much of the money Richard Nixon saved by committing America not to return to the moon before 2000 was spent on things people "needed".

That will need backing up, either way.

I think it would be impossible to get ten people to agree on whether any particular use of the money was needed.
I failed to state that my real objection to saying whether something is 'needed' or not is that it is usually an attempt to put an objective veneer on a subjective value judgment.

Back on topic...
Manned spaceflight: only justifiable to transport people to moons and planets where they are better than machines - whether they are more cost effective is arguable.

Space Elevator: currently too expensive and probably always too dangerous.

Mars voyage: worth doing eventually, but not before returning to the moon. (There was a plan in the Apollo program to build a space gun (ok, linear accelerator) to launch spacecraft from the moon.) - oops, off topic again...

 

[JaredJames]

There is plenty of evidence a space gun is feasible but not necessarily economic. eg
http://www.astronautix.com/lvs/maret2g1.htm" .
There are certainly economic limits to the velocity a gun can impart, but I'd be very surprised if you can find any theoretical limit.

I agree 100% with this.
Please specify for how long an object has to be traveling at orbital velocity before it is in orbit.

Did you check the numbers for a speed that you'd have to fire a projectile horizontally off everest for it to orbit only once?

Not to mention the fact we don't have materials that can survive those sort of speeds (within an atmosphere). For proof, see the problems we have with scram jets - the air resistance destroys them.

 

[Vanadium 50]

If you launch with a gun from earth, the lowest point is exactly where you launched it from - i.e. on the ground. You can't get it in a real orbit (where the lowest point is > 100 km up)

 

[mistergrinch]

On the topic of space guns, I like this design for a nuclear space cannon: http://nextbigfuture.com/2009/02/nuclear-orion-home-run-shot-all-fallout.html

 

[D H]

I'm in a bed & breakfast with a lousy internet connection, so I can't see than nextbigfuture.com reference. I have my suspicions, however. Is it all blown out of proportion? (Sorry for the bad pun.) Does it whitewash / completely ignore known downsides? Does it whitewash / completely ignore the fact that such a device hasn't been built, even on a vastly reduced scale? nextbigfuture.com is not a reputable source.

This gets to the heart of all of these next big futures in aerospace engineering. None of them are aerospace engineering. Certainly not space elevators. They're still science fiction. Rail guns? Science fiction. Fission-based rockets? Science fiction.

In this case, given what just happened in Japan, it is science fiction that ignores political reality. Nuclear rockets are a nonstarter just because of the public perception that anything nucular is bad, and not just pollute the local stream bad. Godzilla / Armageddon bad.

 

[russ_watters]

If that list is in order of 'preference'...

The list is in the order they popped into my head. But I think they are the largest individual expenditures of the US government.

 

[russ_watters]

There is plenty of evidence a space gun is feasible but not necessarily economic. eg
http://www.astronautix.com/lvs/maret2g1.htm" .

No, there really isn't. That link, for example, is a rocket fired from a gun, not a gun alone.

Since it's never been done, it is certainly a stretch to say it is feasible, in any sense of the word.

There are certainly economic limits to the velocity a gun can impart, but I'd be very surprised if you can find any theoretical limit.

Besides the fact (again) that a gun alone can't put an object in orbit (the payload needs to contain a rocket in order to shape the trajectory into an orbit), the theoretical limits that haven't been dealt with yet would include g-forces on materials, frictional heating (both in the gun and out of the gun) and gas dynamics.

I agree 100% with this.
Please specify for how long an object has to be traveling at orbital velocity before it is in orbit.

I wouldn't consider an object to be in orbit unless it's trajectory carried it around the Earth at least once without crashing. Otherwise you could throw a baseball and consider it to be in orbit. While it may be instructive to do that in some contexts, quibbling about it in this thread seems like trolling to me. No matter what label you put on it, you obviously do see the vast difference between what the ISS is doing and what a gun on Everest could do.

I think it would be impossible to get ten people to agree on whether any particular use of the money was needed.
I failed to state that my real objection to saying whether something is 'needed' or not is that it is usually an attempt to put an objective veneer on a subjective value judgment.

You can't get more than about 6 of 10 to agree on even the most fundamental scientific ideas, but the universe doesn't care if people understand it or not, so that requirement isn't really worth much.

If tomorrow, the people of the US decided that all government healthcare expenditures be re-directed to a crash-program to put a man on Mars, it wouldn't change the reality of the fact that healthcare spending is needed. One way or another, people will spend money on healthcare.

However, the point of needs vs wants is still relevant enough: because those needs I listed are very real and very, very important, you'll have a very, very hard time convincing a large enough to matter fraction of the population that spending money on the 'want' of a mission to Mars is more important.

Manned spaceflight: only justifiable to transport people to moons and planets where they are better than machines - whether they are more cost effective is arguable.

In a world of fininte money, "cost effective" is a component of "better". It's part of the reason the space program is structured the way it is.

 

[russ_watters]

I'm in a bed & breakfast with a lousy internet connection, so I can't see than nextbigfuture.com reference. I have my suspicions, however. Is it all blown out of proportion?

Er, well, it's not what you were thinking: it's a Project Orion knockoff. I suppose if you really reach, you could call a nuclear bomb-powered rocket a gun, since it propels itself with explosions like a glossed-over gun (which doesn't propel its projectile with explosions, despite the popular perception)...

 

[D H]

Er, well, it's not what you were thinking: it's a Project Orion knockoff.

That's exactly what I was thinking. Project Orion was science fiction, is still science fiction, will remain science fiction for a long, long time. The true next big future has to be technically, economically, and politically feasible. Orion might be technically feasible, so it gets one out of three, maybe.

 

[ngc1333]

And if you were one of the people told you had to die because they wanted to get to space?

Complete non-sense.

There is a difference between the risk involved once you're in space and exploring to risking the lives of people on Earth simply to get you there.

Air pollution kills millions of people every year, just to put things in prospective.

 

[JaredJames]

Air pollution kills millions of people every year, just to put things in prospective.

Your point being?

 

[sophiecentaur]

Air pollution kills millions of people every year, just to put things in prospective.

I sort of see where you're coming from but two wrongs don't make a right.
The number of deaths caused by some sources of pollution has been reduced greatly, by legislation. Pity the legislation seldom seems to reach as far as the poor and underprivileged masses throughout the world. But that's commercial pressures - which, btw, are unlikely to overcome the objections of rich and articulate societies which may perceive the risk of an elevator failure as far outweighing the risks to gold miners in South America.