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Offline Freeholder

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Space Station Economical Resupplies
« on: 10/12/2007 22:02:44 »
Space Station in orbit resupplies.  That is my topic.  I wonder if a hydrogen balloon would lift itself into the stratosphere?  And if it were weightbearing with,say, water to be given to the space station, could a snatching device be made?  I have something in m,ind something like how the fast mail strains operated by the post office in years gone by snatched from the station a sack of mail.

Now, since the orbits the space vehicles are moving in require a speed to stay up, That is the vehicles need a at around 24,000 mph (escape velocity I think) to stay in orbit, could a hooking device that would grab the supply without tearing it apart be imagined.

Or can another way be found that would provide supplies less expensively that the millions $
the supply socket costs now.  Arthur C Clarke proposed that a bucket convey system made up of the carbon fullerines could reach a stationary station.

And then, whatever is happening with the rail guns that can shove a vehicle to the escape velocity? Anybody hear anything? 

What do you think?

 


 

lyner

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« Reply #1 on: 10/12/2007 23:14:38 »
http://science.nasa.gov/headlines/y2000/ast07sep_1.htm
The Space Elevator.
I fancy this system most of all. Once it has built ("once"!) it is the cheapest way to get up into Low Earth Orbit.
 

another_someone

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« Reply #2 on: 11/12/2007 01:04:21 »
Aside from cost, I really am not comfortable with the safety aspects of a space elevator.

The problems with using a pickup from a balloon (although future technologies may overcome this) is that the present altitude record for a balloon is just short of 52Km.  In general, there is an inevitable conflict of requirements, in that a balloon can only where there is an atmosphere to give it lift, yet a space vehicle pickup, if it is to limit the amount of heat it has to tollerate, as well as the inevitable loss of energy associated with that, wishes to stay above the atmosphere altogether.

What is certainly very feasible is that some means is got to take a supply ship into low space orbit (no more than 100Km - the altitude achieved by Burt Runtan's SpaceShipOne), and then get picked up from there and pulled to a higher orbit by some sort of space tug of the kind you are talking about.

My own preferred fanciful way of getting a vehicle into low orbit is on a focused microwave beam.  The big problem with getting spacecraft into orbit is not the energy required to get them there (that is an unavoidable cost, whatever technology you use), but the cost of carrying the extra fuel to carry the fuel to get you there (this is a problem with any vehicle that must carry its own fuel with it as it rises through the atmosphere).  By using a microwave beam on which the space vehicle can be lifted up, the fuel for the lift remains on the ground, so the only actual fuel that is used is that required to actually lift the vehicle itself.
 

lyner

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« Reply #3 on: 11/12/2007 18:14:23 »
Quote
Aside from cost, I really am not comfortable with the safety aspects of a space elevator.
Why? Do you think people will run into it?
If it is ever made, there will be no other craft ,at height, likely to hit it (everyone would go by elevator) and aircraft could easily miss it - the same as they miss existing obstacles. We would, of course, need a huge exclusion zone.

A high altitude balloon would have a tiny payload and would have to dump its gas - or have to support a tether with which to haul it down. Helium is costly in large quantities (and getting costlier, I believe).

The microwave beam is discussed, on occasions and is, I agree, attractive but what are the sums involved? How big an array is needed to produce a sufficiently narrow beam which wouldn't waste transmitted energy? Many wavelengths, to produce a small spot beam, for sure. The receive antenna would need to be correspondingly large to catch the beam and could produce a lot of drag - energy which would need to be supplied. Some tradeoff would need to be reached.
What actual propulsion system would be used? A reaction system would still need to have something to force out of the back - the atmosphere would run out at altitude, and a source of propellant would have to be carried - extra weight to carry.
I did once read of a proposal for a net, kept aloft by microwave radiation pressure, which could be used as an alternative to satellites for transmitting signals. This would have been kept up by radiation pressure - a very weak force.
The system does have a strange fascination about it, though.
 

Offline Pumblechook

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« Reply #4 on: 11/12/2007 20:15:10 »
Proposals I have seen for a space power station beaming power to Earth users a 2 km diameter parabolic dish in space and 4 sq km of rectennas panels on Earth working at 2.45 GHz..rather large!   Working the other way..2 km would be 20 times the diameter of the biggest dish we have on Earth... 400 times the area.   The dish would have be an accurate curve within 12 mm (1/2 inch).
 

another_someone

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« Reply #5 on: 11/12/2007 20:17:21 »
Quote
Aside from cost, I really am not comfortable with the safety aspects of a space elevator.
Why? Do you think people will run into it?
If it is ever made, there will be no other craft ,at height, likely to hit it (everyone would go by elevator) and aircraft could easily miss it - the same as they miss existing obstacles. We would, of course, need a huge exclusion zone.

Aircraft could easily miss, they also could easily miss the WTC buildings.

Given that this structure reaches out into space, you will also have to take account of collision with high velocity space objects (e.g. a meteor).  Even low altitude anthropogenic space debris becomes an issue.

There is also simply the risk of catastrophic failure.  This is a huge building, more like a bridge than a skyscraper, and could easily be subject to failure through error of design, poor maintenance, or endless other causes.  You will ofcourse have to factor in the effects of vibrational resonance, etc.

If it does fail, you will not only have risk to people on the elevator, but to the population subjected to falling debris beneath the elevator.

How to you undertake the continual inspection and maintenance of the structure, and have you factored in the costs for this?

A high altitude balloon would have a tiny payload and would have to dump its gas - or have to support a tether with which to haul it down. Helium is costly in large quantities (and getting costlier, I believe).

No, I don't believe helium is practical, but hydrogen is.  Since the major disasters involving hydrogen balloons before WWII, our understanding of managing the safety of hydrogen has improved significantly (after all, the space shuttle launch system contains enough of the stuff), and I don't see it as any less safe than methane, or numerous other materials we feel perfectly comfortable handling these days.  Hydrogen is lighter than helium, and so would actually be a preferable gas to use in that respect, and far more available.

I don't thing the balloon idea will work (as I said, the problem as I see it is that it could not get high enough to allow a space tug to pick it up - and as you say, how you bring the balloon down for reuse is another matter), but I think the issue of availability of helium is a red herring.

The microwave beam is discussed, on occasions and is, I agree, attractive but what are the sums involved? How big an array is needed to produce a sufficiently narrow beam which wouldn't waste transmitted energy? Many wavelengths, to produce a small spot beam, for sure. The receive antenna would need to be correspondingly large to catch the beam and could produce a lot of drag - energy which would need to be supplied. Some tradeoff would need to be reached.
What actual propulsion system would be used? A reaction system would still need to have something to force out of the back - the atmosphere would run out at altitude, and a source of propellant would have to be carried - extra weight to carry.
I did once read of a proposal for a net, kept aloft by microwave radiation pressure, which could be used as an alternative to satellites for transmitting signals. This would have been kept up by radiation pressure - a very weak force.
The system does have a strange fascination about it, though.

My own idea (probably has been thought of elsewhere) would not be a mass reaction propulsion system at all, but an electromagnetic reaction system.  The idea is that the base of the vehicle would have an array of antennae that receive the incoming microwaves, and would use the power to generate an outgoing microwave that would interact with the incoming microwave to create a repulsive force (essentially magnetic levitation at a distance, and at high frequency).

Yes, it would need a large cross sectional area (not that the cross sectional area of the space shuttle's fuel tank is exactly small), but the amount of drag created is highly dependent of speed, and if one is not looking at a mach 3 flight (at least not while in the denser part of the atmosphere), then the drag could be kept to manageable levels.

The ground array may need to be large, but it need not be a single antenna, but divided amongst lots of small, widely separated, antenna, creating a synthetic antenna of large size.  The ground antenna itself could be synchronised by using a low power locator transmission generated in the vehicle onto which the desperate ground signals are locked.  This would even allow the transmitting antennae to be located aboard ships deployed in the middle of the ocean, with the ships subjected to the motions of the sea, but remaining locked onto the locator signal.  It would also compensate to some extent  for any refraction caused by atmospheric effects, since the locator signal would be subject to the same refection.
« Last Edit: 11/12/2007 20:24:41 by another_someone »
 

Offline Pumblechook

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« Reply #6 on: 11/12/2007 20:26:22 »
---The ground array may need to be large, but it need not be a single antenna, but divided amongst lots of small, widely separated, antenna, creating a synthetic antenna of large size. ---

No..  That technique can be used in radio astronomy to increase resolution but this does not increase the overall gain.    You get lots of wasteful sidelobes. Getting the phasing right with widely space antennas is very difficult. 
 

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« Reply #7 on: 11/12/2007 20:34:09 »
---The ground array may need to be large, but it need not be a single antenna, but divided amongst lots of small, widely separated, antenna, creating a synthetic antenna of large size. ---

No..  That technique can be used in radio astronomy to increase resolution but this does not increase the overall gain.    You get lots of wasteful sidelobes. Getting the phasing right with widely space antennas is very difficult. 

The phasing should not be an issue - that is the purpose of the locator transmission from the vehicle itself - if the individual transmitters lock their phases on to the same incoming transmission from the locator signal, then their phases should be correctly maintained.

Sidelobes may be wasteful, but exactly how wasteful?  Even if you lose 50% of the power that way, that is substantially better than the current fuel usage for space launch.

I was at least as concerned about losses due to atmospheric heating caused by the microwaves, but I would still expect that to be highly preferable to anything we have now.
« Last Edit: 11/12/2007 20:38:12 by another_someone »
 

Offline Pumblechook

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« Reply #8 on: 11/12/2007 20:52:18 »
A phasing system could be made to work I suppose.  Sideloads would be considerable I would have thought.   I am fimiliar with stacking yagi antennas and you have to have them within 1 to 2 wavelenths of one another...very close.,,to avoid excessive sidelobes.     Think about just 2 antennas widely space..  Say each with a one degree beam.  The two signals combine at a point where the path length is the same  but also at thousands of other points where the path difference is N Wavelengths within half a degree of the bearing of main beam.  It is very similar to the interference patterns caused by letting light pass through two slits.  I suspect also that  individual paths would not be stable enough either in terms of not travelling in straight lines and also arriving in phase due to slight changes in the speed of transmission as the atmosphere varies in pressure and humidity from point to point.  The inonosphere can cause probs ...may cause variable phase shifts ...and polarisation changes...Faraday rotation.
« Last Edit: 11/12/2007 20:59:30 by Pumblechook »
 

Offline Pumblechook

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« Reply #9 on: 11/12/2007 21:08:22 »
As ragards atmospheric attenuation.  This is normally negligible below 30 GHz but heavy rain can be a problem above 10 GHz.   
Maybe once or twice a year our satlellite TV signals disappear for a few minutes during very wet weather.  They need to fade by about 6dB (1/4 of normal signal) for the receiver to fail.  As part of an another thread on microwave ovens I did an experiment.  3 sheets of wet paper (total thickness 0.3mm when dry) was enough to make the receiver fail when put over the horn of the Low Noise Block..frequency was 12 GHz. 
« Last Edit: 11/12/2007 21:12:55 by Pumblechook »
 

another_someone

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« Reply #10 on: 11/12/2007 21:37:23 »
A phasing system could be made to work I suppose.  Sideloads would be considerable I would have thought.   I am fimiliar with stacking yagi antennas and you have to have them within 1 to 2 wavelenths of one another...very close.,,to avoid excessive sidelobes.     Think about just 2 antennas widely space..  Say each with a one degree beam.  The two signals combine at a point where the path length is the same  but also at thousands of other points where the path difference is N Wavelengths within half a degree of the bearing of main beam.  It is very similar to the interference patterns caused by letting light pass through two slits.

This is true with two antennae, but you could easily have 30 antennae spread around.  Yes, there is a cost involved, but we are talking about totally reusable components in an industry that regards millions of dollars as small change.

  I suspect also that  individual paths would not be stable enough either in terms of not travelling in straight lines and also arriving in phase due to slight changes in the speed of transmission as the atmosphere varies in pressure and humidity from point to point.  The inonosphere can cause probs ...may cause variable phase shifts ...and polarisation changes...Faraday rotation.

All this is true, but the whole point is that (assuming the locator transmission used a frequency not far off the upbeam transmission frequency), then this should effect equally the location signal, so the upbeam would be automatically adjusted for any phase shifts caused by atmospheric conditions (you could even, with a bit more work, even adjust for for different attenuations along different signal paths by measuring the attenuation of the locator signal coming back down the same signal path).

If you wanted to go further, each upbeam from each ground transmitter could itself send a unique identification signal either encoded in the power beam, or alongside it; and the locator signal could also encode the health (relative attenuation, etc.) of each identification signal, so giving the ground stations even more information to allow them to adjust their power signals.

And ofcourse, the more transmitters you use, the less significant is an adverse signal path from a transmitter.
« Last Edit: 11/12/2007 21:48:38 by another_someone »
 

Offline Pumblechook

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« Reply #11 on: 11/12/2007 22:03:48 »
Keeping 30 transmitters locked in frequency and phase (with path compensation) and (less critical) amplitude is not  going to easy.  On the other hand constructing huge steerable parabolas would not be easy either.   
 

Offline syhprum

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« Reply #12 on: 11/12/2007 22:20:26 »
Should we perhaps reconsider whether we need a space station ?, does it serve any scientific or political purpose ?.
I understand about 100 billion pounds has been spent on it so far and many worthy scientific projects sacrificed to build and maintain it.
 

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« Reply #13 on: 11/12/2007 22:41:08 »
Keeping 30 transmitters locked in frequency and phase (with path compensation) and (less critical) amplitude is not  going to easy.  On the other hand constructing huge steerable parabolas would not be easy either.   

You are not keeping 30 transmitters locked in frequency and phase.  You are keeping one transmitter locked in frequency and phase, and reproducing that 30 times.

Each transmitter is locked onto the locator signal, and is totally ignorant of the other 29 transmitters.

The only case where there may need to be some recognition that there are 30 transmitters is in the computer within the vehicle itself that is analysing the health signal sent alongside the power beam, and so sending information back to each ground transmitter to say that station X is 5% attenuated, while station Y is 7% attenuated, so station Y should boost its power a bit to compensate.  Not rocket science (well, it is, but it is not :)).  Similarly, the internal computer within the vehicle can asses the transit time of each incoming signal, and tell a ground station to alter its phase, which it will do in relation to the common clock signal that the ground station receives from the locator beacon.

The whole thing merely depends on time signals encoded in each transmission, and maintaining time accurate to within about 1/8th of a cycle of the power transmission carrier signal (which should be possible with atomic clocks).

The biggest headache is making sure you carefully calculate the signal delays in the transmitters and receivers of the control signals to ensure that you can carefully calculate the actual time time in transit of the signal (although, in reality, the actual time in transit does not matter so much as relative time in transit, so as long as you can make sure that all the signal delays are the same, it does not matter exactly how long they are).

Given the size of the target we are looking at, I would guess we could use a wavelength of anything around 2cm to 10cm; which would correspond to a frequency just above one hundred megahertz.  We could, I would imagine, comfortably go to longer wavelengths yet (the base of the vehicle could be enlarged to 10 metres or more - the space shuttle external tank is over 27m is cross section).

This would allow an atomic clock, with an accuracy of better than 5 nanoseconds per day, to remain within 1/8th of a cycle (within 1.25 nanoseconds) for about 6 hours.
« Last Edit: 11/12/2007 23:40:14 by another_someone »
 

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« Reply #14 on: 11/12/2007 22:46:54 »
Should we perhaps reconsider whether we need a space station ?, does it serve any scientific or political purpose ?.
I understand about 100 billion pounds has been spent on it so far and many worthy scientific projects sacrificed to build and maintain it.

Not really the question that is relevant.


The relevant question is whether the dozen or so space launches we have each year is sufficient for our future space needs (whether that be to supply a space station, whether it be for interplanetary exploration, whether it be to launch communication satellites, whether it be to develop zero gravity industrial processes - whatever opportunities space may bring).

Whether specifically a space station is something we want or not is one question, but the real question is whether we wish any significant long term presence in space at all.  Even maintaining our present level of space launches, although feasible with current technology, is expensive and not particularly environmentally friendly (let alone, not particularly safe).  I don't see what we are doing at present (let alone any ramping up of capacity, in whatever way) to be sustainable in the long term; so we either stop almost all extraterrestrial activity, or we have to think of better ways of going about it.
 

lyner

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« Reply #15 on: 11/12/2007 23:40:47 »
Have you actually done the sums to calculate the strength of what is surely no more than light pressure?  Or, it could be magnetic force involving the Earths magnetic field?
 

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« Reply #16 on: 12/12/2007 01:17:10 »
Have you actually done the sums to calculate the strength of what is surely no more than light pressure?  Or, it could be magnetic force involving the Earths magnetic field?

Very difficult to accurately calculate without knowing lots of issues concerning how focussed the beam is, what the conversion efficiencies are, etc.

Looking at commercial electromagnets, they seem t be able to light about 2.2 tonnes per kilowatt.  So, for a 100 tonne vehicle (including payload), it would require about 50 kilowatts of power to lift.

Clearly, we are dealing with oscillating electromagnetic fields rather than stationary magnetic fields, and we are dealing with fields that are focused over a great distance rather than locally generated.  We are also dealing with fields that are trying to react against induced fields rather than fields relying on paramagnetism.

One linear motor that I can see in use for maglev train applications claims about 5000lbs of thrust (453Kg) for 1.125MW of power.  Since linear motors used induced fields for their reaction, they would be closer to ideas here than DC electromagnets.  This would imply that you would require 248MW of power to lift 100 metric tonnes.

Ofcourse, any power over and above that required to life the vehicle amounts to upward acceleration.  A 10% increase over that required to lift the vehicle would amount to an upward acceleration of about 0.9ms-2, which would amount to about 2mph upward acceleration per second.

I cannot say that I would have the least idea where to start calculating all the parameters without a lot of experimentation.
 

Offline daveshorts

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« Reply #17 on: 12/12/2007 10:11:14 »
Going back to the original question, one reason that this is not done is that lifting you up even to 200km doesn't get you into orbit, you then have to accelerate up to about 24 000km/hr or you just fall back down again.

This requires significantly more energy than lifting you up there. I am not saying that you wouldn't need a much smaller rocket as it would probably save most of the first stage on the rocket which is usually the biggest, but it doesn't save as much energy as you would think.
 

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« Reply #18 on: 12/12/2007 15:26:24 »
Going back to the original question, one reason that this is not done is that lifting you up even to 200km doesn't get you into orbit, you then have to accelerate up to about 24 000km/hr or you just fall back down again.

This requires significantly more energy than lifting you up there. I am not saying that you wouldn't need a much smaller rocket as it would probably save most of the first stage on the rocket which is usually the biggest, but it doesn't save as much energy as you would think.

Yes, it requires energy, but my understanding is the manner in which the energy is supplied.

My understanding is that if the tug that pulls the supply ship is massive enough (and it would have to be very massive to be meaningful), then most of the extra energy (maybe even all of that energy) could be supplied simply from the kinetic energy of the tug.  Then, the tug will lose some kinetic energy, and will need to recover that energy before it picks up the next supply ship, but with enough tugs available, each tug could pick up only one supply ship a year, and spend the rest of the year slowly picking up its lost kinetic energy (e.g. through some slow solar powered mechanism - e.g. solar sails).
 

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« Reply #19 on: 12/12/2007 17:15:42 »
Although can you imagine the actual manoeuvre, you would have to go from stationary to 24000kph in the stretch of your tether.  Even if you have a long tether, you then have a huge amount of elastic energy to dissipate somehow without causing the payload to collide with the tug...
 

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« Reply #20 on: 12/12/2007 18:47:37 »
Although can you imagine the actual manoeuvre, you would have to go from stationary to 24000kph in the stretch of your tether.  Even if you have a long tether, you then have a huge amount of elastic energy to dissipate somehow without causing the payload to collide with the tug...

Although I can imagine various ways to mitigate that, I do agree it is a non-trivial concept at many levels.  All I was suggesting is that one can imagine a theoretically possible way of achieving it, not that it would be easy.

I would imagine that much of the 'elastic energy' would best be taken up by a winch (much like the slack taken up on a fishing line when a large fish first bites, where the line is first allowed to spool out, before being reeled in). Ofcourse, managing the friction on the winch could be a bit challenging.
« Last Edit: 12/12/2007 18:51:55 by another_someone »
 

Offline BolianAdmiral

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« Reply #21 on: 12/12/2007 21:14:55 »
The space elevator is perhaps the most ridiculous idea yet. Not only would it look just silly as all hell, I don't care how super-strong they make that thing... if you have ANY construct that thin, in relation to the size of the Earth and the Moon, it'll just snap like a twig, end of discussion. I really don't see why anyone at all supports the idea of a space elevator... it's just so incredibly silly.

The best way to go about resupplying the ISS would be to have a set of unmanned and computer-controlled "tanker" orbiter shuttles, that could be launched into space and fuel or resupply the station, via docking, and then return to Earth to be prepped for the next run.
 

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« Reply #22 on: 12/12/2007 21:45:46 »
You can't use the same principles used for maglev (for distances of a few cm) to a vehicle at a distance of many miles. What sort of field pattern would you need and what size of electromagnet would you need?
You would have to use em waves, if you want to concentrate the field and that leaves you with a minuscule force, explainable in terms of momentum change of photons (fractions of a Newton for kW/sq metre power density). Where would the extra factor of a million come from and what would hou do with all the wasted energy (reflected or dissipated)?
This problem is, actually, a simple application of Maxwell's equations, which also predict light pressure and I don't think there's a valid way round it.

The space elevator is perhaps the most ridiculous idea yet. Not only would it look just silly as all hell, I don't care how super-strong they make that thing... if you have ANY construct that thin, in relation to the size of the Earth and the Moon, it'll just snap like a twig, end of discussion. I really don't see why anyone at all supports the idea of a space elevator... it's just so incredibly silly.

The best way to go about resupplying the ISS would be to have a set of unmanned and computer-controlled "tanker" orbiter shuttles, that could be launched into space and fuel or resupply the station, via docking, and then return to Earth to be prepped for the next run.
Well, that's me well and truly dumped on!
However - why should anything be snapped like a twig? It would bend - by many km, of course. The size, related to the earth is irrelevant - the earth is not going to be jerking about in any surprise fashion; it will be going round steadily, just as it is now. It only has to be strong enough to handle manmade impacts. The Twin Towers were built on the cheap and only fell down because they caught fire - not due to the initial impact.
The elevator system has been considered seriously but, of course, it awaits some suitable material for the tether.

Where do the 'tankers' save you any energy? You need just the same amount of fuel, however you care to lift your payload of fuel for the other rockets to use. The re-usable stages on the shuttle already do the same job as your tankers but could, of course, do a better job if they could be flown back to land safely rather than needing to be fished out of the sea and reconditioned.
 

Offline BolianAdmiral

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« Reply #23 on: 13/12/2007 00:45:26 »
The Earth rotates at about 1,000 MPH... there will come a point in altitude, where the spped will have an effect on even the strongest structure that is that thin, compared with the Earth's surface... it will bend to a degree, and then just be sheared or snapped or pulled off.

Tankers or other unmanned vehicles would be better, because they'd be cheaper, resusable, won't look uber-silly, and are just plain more practical than building an elevator to space. The very mental visual of a space elevator being built is so comical to me, because of its impracticality. I mean, just the cost alone would be as sky-high as the elevator.
 

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« Reply #24 on: 13/12/2007 01:09:38 »
You can't use the same principles used for maglev (for distances of a few cm) to a vehicle at a distance of many miles. What sort of field pattern would you need and what size of electromagnet would you need?
You would have to use em waves, if you want to concentrate the field and that leaves you with a minuscule force, explainable in terms of momentum change of photons (fractions of a Newton for kW/sq metre power density). Where would the extra factor of a million come from and what would hou do with all the wasted energy (reflected or dissipated)?
This problem is, actually, a simple application of Maxwell's equations, which also predict light pressure and I don't think there's a valid way round it.

OK, I shall go through some of the issues as I see them (some ideas have come in and gone out of my concept at various times, but discussing them does make clearer what needs to be in, and what can remain out - not that it proves it will work, only that if it is to work, what are the ways it needs to address its problems).

It may be that a simple beam will provide no more pressure than you suggest, with most of the radiation remaining within the reflected beam - which is why (that and to minimise problems associated with high power radio beams bouncing all over the place, into people's homes, etc.) from the beginning the requirement was that whatever solution was to be achieved had to bring uncontrolled reflections down to negligible levels (can never be zero, but there has to be very strict limits placed upon the power dissipated in that way).

One of the differences between a simple beam bouncing off a mirrored surface and a maglev system is that, however leaky, the maglev system nonetheless forms part of a magnetic circuit, where most of the energy remains within the circuit.  Thus, it does not matter how much of the magnetic field is converted into acceleration since, so long as the field remains contained within the circuit, ultimately 100% much be converted into acceleration, because there is nowhere else for it to go.  Ofcourse, this is an ideal position, and in the real world there will always be losses in the system, so some proportion of the magnetic lines will be wasted, and not converted into acceleration at all.  Nonetheless, it does demonstrate that the only way to go is to create a circuit from the EM waves that mimics the magnetic circuit of the maglev system.  If we achieve this, then we solve the problem of unwanted reflections, and the problem of most of the wasted energy.

So, the question is how do we lock the EM wave into a circuit?

One way in which this is done in laboratory conditions is, if one has to mirrored surfaces that are exactly parallel to each other, and introduce an EM wave between them, then you can create a standing wave that simply bounces betwixt one mirror and its opposite number.

OK, lets step out of the laboratory and back to the launch site.  There is no way that the mirrors on the underside of the launch vehicle are ever going to be, let alone remain, parallel to even one, let alone all, of the 30 ground stations transmitting the lift beam.  So we need to modify the solution somewhat.

The problem we have is that a simple mirror will only reflect an EM wave in the plane of the mirror itself, and will not reflect it along the incoming path unless the plane of the mirror happens to be perpendicular to the incoming path.  I believe that there are, and has been since the 1960s, meta-materials that will allow an incoming EM wave (only over a narrow bandwidth, but that is not a significant limitation for us) to reflect and incoming EM wave precisely along the path it came in, no matter in what direction the incoming EM wave is coming from.  Since this is happening in the bulk of the meta-material, it is not actually happening across a plane at all, so the orientation of the beam with respect to a plane is of no consequence.

If one excludes thermal losses and wave scattering for the moment, then in theory, if one surrounds the lift beam transmitting aerial with this meta-material, and covers the base of the launch vehicle with this meta-material, then one can generate a perpetual standing wave (irrespective of location and orientation of the reflectors involved) that will last until all the energy contained within the EM wave has been converted into upthrust.

Ofcourse, one aspect of this that I have presently ignored, is that a standing wave, in order to be maintained, must not only be accurately reflected the incoming path, but the points of reflection must be an integral multiple of the half wavelength of the EM wave.

The problem is that, even if one could maintain such an accurate distance between one ground station and the launch vehicle, as soon as the launch vehicle begins to move, that distance will have changed, and the standing wave will collapse.  To do that with 30 ground stations and the launch vehicle would be inconceivable, even in a transient manner.

That means either that the point of reflection within the meta-material has to be constantly changing, in order to maintain a standing wave, or we need another solution to maintaining a circuit.  It may be possible to design a meta-material that somehow maintains this standing wave by changing the virtual point of reflection within its body as the distances change, but I do not know enough (or virtually anything) about the meta-materials and their design to make any assumption that this may be possible.

So the other alternative is to maintain a feedback of the EM wave without resorting to standing waves.  This would still require the use of the same meta-meterial on the base of the launch vehicle to reflect back the incoming EM wave, but the ground station would use a very different philosophy.

The ground stations transmitters, rather than being surrounded by this meta-material, would be surrounded by receiving dipoles, that will receive the reflected wave, rectify the wave, and then send that energy back into the newly synthesised upbeam that is phase controlled as I described in the earlier posts.

I believe that in a lossless system (an ideal world), this would convert 100% of the transmitted EM beam into uplift of the launch vehicle, because there is simply nowhere else for the energy to go.

Ofcourse, the real world is not lossless.  I have taken no account of thermal losses that may occur in the meta-material when it reflects the wave.  I have taken no account of thermal losses, or secondary emissions, that may occur in the ground station as it receives in reflected wave and turns that energy around into the upbeam.  I have taken no account of scattering of the wave when in transit between the ground station and the launch vehicle.  No doubt there are other losses also that I have not taken account of.

The real question, that I have no idea of, is whether these losses can be kept to a low enough level to ensure that most of the energy of the wave (or, at least, an adequate percentage of the energy of the wave) is converted into uplift rather than lost in these various real world inefficiencies.
« Last Edit: 13/12/2007 02:17:42 by another_someone »
 

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Space Station Economical Resupplies
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