The Space Runway - a radical, simple way of getting to LEO

[az5_button]

If your ship is inducing eddy currents in the pipe, those eddy currents form magnetic fields which in turn introduce their own eddy currents in the ship's magnets.

The field from the pipe doesn't move relative to the ship, therefore no current is induced in the ship.

[az5_button]

b.lorenz: "you have actively support the payload in the vertical plane"

- this is possible with passive inductrack maglev tech, but the details are beyond what I have the time and knowledge to calculate. Further work with relevant experts would pin this down.

You're completely failing to address this important point.  Just claiming something will work but saying the details are beyond you isn't going to convince anyone.

I need help to solve this. I don't understand exactly how inductrack works, it's complicated.

See: https://e-reports-ext.llnl.gov/pdf/237852.pdf

The gist of it, I think, is you make a Halbach array https://en.wikipedia.org/wiki/Halbach_array . This is a series of magnetic fields in opposite directions.

Then you move it across a conducting surface, and there are induced eddy currents in the surface. At low speed it just acts as drag. But at higher speeds it creates a lot of lift.

See this video for example:

Now I don't know exactly what happens when you turn the speed up to 7800 m/s. I'm assuming you get a LOT of lift, probably too much actually, so the asymmetry of the Halbach array might have to be reduced to stop the magship from crashing into the ceiling.

As the speed decreases the lift force will fall, but the effective weight of the magship will also fall because it is approaching orbital speed. So it's entirely possible to levitate the thing.

And as long as the centre of gravity of the magship is slightly below the centre of electrodynamic lift, it's even stable. Stable!!!

[az5_button]

Then give us a flight rate and compare the full system costs of your proposal to the full system costs of doing the same thing with a scaled-up fully-reusable Starship-type vehicle.

The space runway synergizes with rockets. The rocket delivers 10x the payload (or more) to the runway than it can deliver to LEO because the delta-v required to get to the runway is so much lower (and the nature of the rocket equation). The runway is 10x better than the rocket, irrespective of how good the rocket is.

In fact there will be additional benefits, like being able to use a higher thrust rocket and lose less to gravity, and more mass available to make the rocket robust, meaning less maintenance of the rocket would be needed.

the dimensions of the maglev track, the size of the radiators, the size of the solar panels, and then give us a defensible estimate for the cost of maintaining that.

- there are no radiators. (and I don't understand where you got that from?).

- The "maglev track" is just an aluminium tube.

- the solar panels would indeed be large. To handle a 2000 ton payload from a BFR-class rocket, you need about 40GW of solar.

The maintenance cost would be relatively irrelevant when amortized on a per-kg basis. This thing would be lifting 11.6 megatons to orbit per year.

Obviously one wouldn't start with such a monster system.

[Coastal Ron]

the dimensions of the maglev track, the size of the radiators, the size of the solar panels, and then give us a defensible estimate for the cost of maintaining that.

- there are no radiators. (and I don't understand where you got that from?).

If you are using energy, regardless where it is coming from, it generate heat. Too much heat can degrade electronics and affect systems, so you need to have a way to remove the heat. Radiators are the usual way of doing that in space.

- The "maglev track" is just an aluminium tube.

No, it can't be "just an aluminum tube", because aluminum is not magnetic, so you can't make a maglev track out of it. And in general maglev tracks are very heavy, and very costly - $100M/mile was one estimate for a U.S. system, and that doesn't count the maintenance costs.

- the solar panels would indeed be large. To handle a 2000 ton payload from a BFR-class rocket, you need about 40GW of solar.

Not only the panel weight, but all of the electronics and support equipment that would be needed for a production facility of that size. And they are not maintenance free.

The maintenance cost would be relatively irrelevant when amortized on a per-kg basis. This thing would be lifting 11.6 megatons to orbit per year.

You can't say it will be irrelevant when every transportation system in the world has relevant maintenance costs. Nothing you are proposing removes the need for maintenance.

Obviously one wouldn't start with such a monster system.

Typically there is a tipping point between demand and supply that allows for significant changes in the economics of something. For air travel at the beginning of the jet age it was a lack of airport terminals that allowed for the Boeing 747 to become a logical change to the aircraft of the day. But as we see today, as the hub-and-spoke has changed to direct flights, the age of the 747 (and the Airbus A380) is coming to an end - with Airbus losing money on the A380.

So anyone that THINKS about investing in this has to wonder if it will be needed long enough to make back their sizable investment. And it won't be worth investing in UNTIL there is already a massive and demonstrated demand for material from Earth to destinations in space, and once that market is there they may not feel the need to build this rather limited transportation solution.

[ChrisWilson68]

- The "maglev track" is just an aluminium tube.

After carefully considering everything you've said in all your posts, this one line from your latest posts sums it up for me.  It's very clear you have no idea what you're talking about.

Aluminum isn't magnetic.  You made this mistake upthread, and someone pointed it out then, but you apparently forgot again.  And you're confusing the tube you're supposedly using to accelerate the vehicle up to orbital speed through eddy currents with the "maglev track" you used to hand-wave away the enormous problem you're ignoring of gravity losses.

I don't know how you expect anyone to take you seriously when you can't even keep track of your own proposals.  Your replies here make it clear you don't really have a coherent proposal here at all, just an idea that is ever-morphing in response to criticism, never becoming firm enough to have a serious discussion about.

[Asteroza]

I just realized this is effectively the same as a cable catapult unbomber design I had written about here previously in an unbomber thread, just with a solid track rather than one based on mass and drag sail tension on a catapult ribbon.

That design had a long ribbon in orbit with effectively embedded inductrak, so the effective drag of the maglev mechanism does the velocity change. To keep the ribbon roughly straight along an orbital track, you had a forward vertical ED tether with substantial masses at the center and end points (ED tether provides reboost to the system by dragging the whole thing forward, end masses provide a tension mechanism for the ribbon while in use), and a trailing drag sail to keep the ribbon taut. Users would place a cable clamp/maglev shuttle/ribbon rider on the ribbon after the forward end overtakes them to "slow down". Inductrak has a design specific max drag speed (exceeding this doesn't seem to increase drag) which makes it interesting for conventional maglev use, so for heavier spacecraft, the ribbon needs to be wider/longer to "stop" the spacecraft before it strikes the trailing drag sail. Inductrak also ceases to be useful below certain design speeds, so you lose the drag and maglev, so at that point you would need some other final speed adjustment method and guidance. Since Inductrak is passive, your primary worry is dissipating the heat in the coils embedded in the ribbon, but since it's already a nice wide and flat ribbon, it doubles as a radiator.

[az5_button]

No, it can't be "just an aluminum tube", because aluminum is not magnetic, so y

Actually it can, and the track material is a *non-magnetic* conductive material. Watch the video above!

As to the issues of economics, I don't want to stray too far from technical considerations, but for large amounts of cargo to space (and back again!) I think this system is simply unbeatable. It's going to be 10× cheaper than rockets, and if you invest in coilgun infrastructure on the ground then it could be even better.

Now even if all that is true, one needs a market for all that cargo up and down. But for the purposes of this discussion I think it's best to assume that such a market exists and then ask what the best technical solutions are.

As for maintenance, ideally the runway would be low maintenance. There are some open issues about that, like whether it would use ion engines or geomagnetic reboost to gain velocity, and whether the power would be solar photovoltaic or solar thermal. Ideally it would use geomagnetic with concetrating photovoltaic cells, there would actually be very little that could break or go wrong.

But if there is a lot of maintenance, I don't think it's that bad. The runway will lift huge amounts of material - so much that it's worth paying for maintenance on it.

[az5_button]

- The "maglev track" is just an aluminium tube.

After carefully considering everything you've said in all your posts, this one line from your latest posts sums it up for me.  It's very clear you have no idea what you're talking about.

Aluminum isn't magnetic.  You made this mistake upthread, and someone pointed it out then, but you apparently forgot again.  And you're confusing the tube you're supposedly using to accelerate the vehicle up to orbital speed through eddy currents with the "maglev track" you used to hand-wave away the enormous problem you're ignoring of gravity losses..

No, it's not a mistake, this is how inductrack works. It uses the magnetic field induced by eddy current to levitate. The inductrack is just a piece of non-magnetic conducting material.

You should watch the veritasium video above.  I also linked the inductrack paper above but I haven't gone through it.

[gaballard]

This thread is depressing.

[az5_button]

This thread is depressing.

Why? I think it's been very useful!

[ChrisWilson68]

But if there is a lot of maintenance, I don't think it's that bad. The runway will lift huge amounts of material - so much that it's worth paying for maintenance on it.

If you can't come up with any defensible numbers for the costs, you really can't say it's worth paying for.

[Coastal Ron]

No, it can't be "just an aluminum tube", because aluminum is not magnetic, so y

Actually it can, and the track material is a *non-magnetic* conductive material. Watch the video above!

I just did, and it confirmed what I know which is that the "vehicle" can be made from aluminum, but the track is made from magnets. How else are you creating the magnetic fields?

And FYI, the recycling industry uses the ability to induce magnetic fields in aluminum in order to reject aluminum out of falling waste streams, but it takes big magnets to do that (here is a company that makes them).

So again, it's not just an aluminum tube, it would have to be a (heavy) tube with a high density of magnets.

You need to acknowledge this if you want to be seen as being open to accepting help. Do you?

[az5_button]

I just did, and it confirmed what I know which is that the "vehicle" can be made from aluminum, but the track is made from magnets. How else are you creating the magnetic fields?

...

So again, it's not just an aluminum tube, it would have to be a (heavy) tube with a high density of magnets.

You need to acknowledge this if you want to be seen as being open to accepting help. Do you?

The magnets would be on the vehicle ("magship"), and the track is just a conductive non-magnetic tube.

The tube is non-magnetic, but when a current is induced in it by the vehicle passing over it, a magnetic field is produced which levitates the ship.

This is how inductrack works.

[az5_button]

But if there is a lot of maintenance, I don't think it's that bad. The runway will lift huge amounts of material - so much that it's worth paying for maintenance on it.

If you can't come up with any defensible numbers for the costs, you really can't say it's worth paying for.

Maintenance cost isn't easy to estimate at this stage. What's the maintenance cost of an airport or a seaport, for example? Though we don't know exactly what those numbers are, we know they are small per kg of air freight or sea freight because they are amortized over a huge amount of cargo that uses the airport or seaport, and each kg of cargo imposes only a tiny expense.

The key to making maintenance cost low is making the system simple and reducing wear and tear caused by use. One possible cause of such wear and tear is supersonic shockwaves in the metal tube, and I am currently not sure how to deal with this.

Maintenance costs like replacing failed solar panels or faulty wires are not much of a worry to me. And at this stage I think it's counterproductive to focus on such things - better to first fix the big issues like how the inductrack works, magship design, and the shockwave problem.

[QuantumG]

Makes more sense to use circular magnets on a metallic rod to me... but on the other hand, if you can make your long tube from spent rocket stages (possibly SSTO delivered) then that'd make sense 

[az5_button]

I just realized this is effectively the same as a cable catapult unbomber design I had written about here previously in an unbomber thread, just with a solid track rather than one based on mass and drag sail tension on a catapult ribbon.

That design had a long ribbon in orbit with effectively embedded inductrak, so the effective drag of the maglev mechanism does the velocity change. To keep the ribbon roughly straight along an orbital track, you had a forward vertical ED tether with substantial masses at the center and end points (ED tether provides reboost to the system by dragging the whole thing forward, end masses provide a tension mechanism for the ribbon while in use), and a trailing drag sail to keep the ribbon taut. Users would place a cable clamp/maglev shuttle/ribbon rider on the ribbon after the forward end overtakes them to "slow down". Inductrak has a design specific max drag speed (exceeding this doesn't seem to increase drag) which makes it interesting for conventional maglev use, so for heavier spacecraft, the ribbon needs to be wider/longer to "stop" the spacecraft before it strikes the trailing drag sail. Inductrak also ceases to be useful below certain design speeds, so you lose the drag and maglev, so at that point you would need some other final speed adjustment method and guidance. Since Inductrak is passive, your primary worry is dissipating the heat in the coils embedded in the ribbon, but since it's already a nice wide and flat ribbon, it doubles as a radiator.

"unbomber" - yes that is kind of what this is!

Interesting, so you had a version of this except it was a tension structure rather than a compression structure?

Can you link to it?

Were you aware of Kingsbury's spaceport?

[A_M_Swallow]

Instead of using the Space Runway as an upper stage it could be used as a kick stage. The payloads could be sent to GEO, lunar orbit and Mars orbit.

The payload and tube would be at approximately the same speed so the entry would be a docking rather than an instantaneous bullseye.

[Asteroza]

I just realized this is effectively the same as a cable catapult unbomber design I had written about here previously in an unbomber thread, just with a solid track rather than one based on mass and drag sail tension on a catapult ribbon.

That design had a long ribbon in orbit with effectively embedded inductrak, so the effective drag of the maglev mechanism does the velocity change. To keep the ribbon roughly straight along an orbital track, you had a forward vertical ED tether with substantial masses at the center and end points (ED tether provides reboost to the system by dragging the whole thing forward, end masses provide a tension mechanism for the ribbon while in use), and a trailing drag sail to keep the ribbon taut. Users would place a cable clamp/maglev shuttle/ribbon rider on the ribbon after the forward end overtakes them to "slow down". Inductrak has a design specific max drag speed (exceeding this doesn't seem to increase drag) which makes it interesting for conventional maglev use, so for heavier spacecraft, the ribbon needs to be wider/longer to "stop" the spacecraft before it strikes the trailing drag sail. Inductrak also ceases to be useful below certain design speeds, so you lose the drag and maglev, so at that point you would need some other final speed adjustment method and guidance. Since Inductrak is passive, your primary worry is dissipating the heat in the coils embedded in the ribbon, but since it's already a nice wide and flat ribbon, it doubles as a radiator.

"unbomber" - yes that is kind of what this is!

Interesting, so you had a version of this except it was a tension structure rather than a compression structure?

Can you link to it?

Were you aware of Kingsbury's spaceport?

Unbomber, reverse bomber, fishing, HASTOL, there are a lot of similar names for the idea of dragging something into orbit from above, typically dependent on large orbital infrastructure (system itself when it is a massive structure, or the supporting infrastructure economy such as propellant depots).

No, I wasn't aware of Kingsbury's spaceport in literature actually.

Forum search is failing me, but I think this is the main thread where I described a tension based system...

https://forum.nasaspaceflight.com/index.php?topic=35648.msg1255896#msg1255896

The small spark of an idea was that if you are dragging something into orbit, it's a lot like a ring on a whip being accelerated from handle to tip.

I suppose in theory the ribbon setup also allows accelerating an already coorbital payload faster to go to a higher orbit, but requires running an actual active linear motor on the ribbon (the ostensible cable catapult part) using the same ribbon clamp. If the ribbon remains passive, then that means you need a lot of electric power onboard the clamp/vehicle.

[Coastal Ron]

The magnets would be on the vehicle ("magship"), and the track is just a conductive non-magnetic tube.

The tube is non-magnetic, but when a current is induced in it by the vehicle passing over it, a magnetic field is produced which levitates the ship.

This is how inductrack works.

So each vehicle has to carry a heavy load of not just magnets, but power sources to energize the magnets? There goes your mass advantage.

Have you done the calculation to find out how big the magnets need to be, and what their power consumption requires?

[az5_button]

So each vehicle has to carry a heavy load of not just magnets, but power sources to energize the magnets? There goes your mass advantage.

Have you done the calculation to find out how big the magnets need to be, and what their power consumption requires?

The preferred method is permanent magnets, not electromagnets. The reason is simple: permanent magnets have fewer ways to go wrong.

The amount of such magnets depends on the vehicle speed, wall thickness and required g-force.

The calculation is over on the stack exchange space post, seems to indicate that the required field is about 0.01T, and drom some basic scaling I think the ship can be 1% magnets if the wall thickness is 1% of the tube diameter.