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Gaussian Cooridor

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Thu, 2013-01-31 21:37

Erenthia

Gaussian Cooridor

I was trying to think of a way ships could travel more quickly throughout the solar system. Reaction mass seems to be the major limiting factor, so I was thinking: What if you had way-stations throughout the system - not fuel depots, but giant electromagnetic rings, attached to massive asteroids, solar powered, and able to maneuver via solar sails. Essentially they would amount to kinetic energy capacitors, storing up the sun's energy over long periods of time and providing short bursts of power. Physically they would operate like colossal coil guns stretched across the entire solar system. In principal you could get by without bring any reaction mass at all, but that does seem dangerous. The problem is, I can't even [i]begin[/i] to guess at what kind of speed-up would be realistic with this sort of infrastructure in place. Obviously you'd still need to decelerate and such a system would seem vulnerable to acts of terrorism, but still it's intriguing. Anyone want to take a stab at it?

—

The end really is coming. What comes after that is anyone's guess.

Thu, 2013-01-31 23:38

NewtonPulsifer NewtonPulsifer's picture

Gaussian could work - a

Gaussian could work - a problem is it doesn't have great efficiency at long range - but there's plenty of options to transfer momentum if you have a network of waystations. A big problem with waystations is the [i]stations themselves[/i] potentially need to be travelling at an appreciable clip or otherwise you don't have enough time to transfer momentum because you zip by them too quickly. A good way is to stick a big spring and a pusher plate on your ship. The waystations fire mass drivers at the butt of the ship. Not a dignified way to travel, but the efficiency is really good. There's bouncing photons back and forth between two mirrors. Each additional bounce gets you more momentum for your watt. 3000 times amplification has already been demonstrated - 35 micronewtons for a 1.7 watt laser. MIT developed a mirror that can do 100,000 times. That gets you roughly 1167 micronewtons for 1.7 watts, or 686 micronewtons per watt (1458 watts per newton). Maybe EP tech can do better than 100,000 times. You could have a network of bolastations. The ship enters the first bolastation at the center, moves down the tether and then launches from the tip of the tether at say 5km/sec, then does a rinse/repeat cycle as it comes along more bolastations on the way. The big problem with the bolastations is you essentially need an assortment of "speed lanes" each with waystations travelling at a different km/sec. Seems like you'd need too many stations with anything but the resonant laser mirror solution (it has the best range and it is the most tolerant of velocity differences between the waystation and spacecraft). Some of these solutions can also double as a weapon, and thus benefit from being subsidized by defense budgets.

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Fri, 2013-02-01 05:24

Arenamontanus Arenamontanus's picture

Yes, the big problem is that

Yes, the big problem is that you want to have a slow acceleration as you pass each station, or your ship and its contents get squashed. So the stations shouldn't be a single coil but rather a bit of coilgun barrel. The problem is that this heavy barrel needs to be reoriented each time a ship arrives so that it can be perfectly aligned with where it is going. Very cumbersome (and don't even think of misalignments!) However, this kind of setup might works well when ships only arrive from one slowly changing direction. So for a common trajectory - say between Mars and Luna - you could use this. Even more likely is using coils or bolas to send capsules within a constellation of habitats. You can even launch capsules using habitat rotation and catch them at the other end. No reaction mass needed, no mess. Just don't break the capture system.

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Fri, 2013-02-01 18:53

Ranxerox

Conservation of momentum problems?

The amount of forward momentum applied the ship will be applied in reverse to the accelerator ring. Presumably the accelerator ring is a good deal more massive than the ships, but still if a lot of velocity is being added to the ship the effect on the ring wouldn't be negligible. So to keep your rings in place you are going to need reaction mass. So you will need to place your rings strategically.

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Fri, 2013-02-01 20:40

Erenthia

Yeah, you'd need solar sails,

Yeah, you'd need solar sails, and probably some amount of rocketry for fine tuning on final approach, but the computing power required for that is trivial. But how much of a speed-up is realistic for such a system? Obviously it's going to vary depending on where you are and where your going, but I imagine there some kind of upper-bound on how much of a speed boost you could get out of that system. I'm just hoping someone here can get my in the right ball-park.

—

The end really is coming. What comes after that is anyone's guess.

Sat, 2013-02-02 07:40

Arenamontanus Arenamontanus's picture

If you have a coil of length

If you have a coil of length L and it can provide an acceleration a to a craft entering with velocity v, then it has L/v seconds to act, and will be able to give a delta-v of aL/v. So if we assume an acceleration of 1 G (~10 m/s^2) and a typical spacecraft speed of 10 km/s, you get a delta-v of 0.001 m/s per meter of coil. Not impressive. The problem is of course the wimpy acceleration: we know EP has railguns able to give you multi-km/s velocities over the span of a few meters, but then we are talking up to millions of Gs. Spacecraft (and crew) will hardly survive more than 10 G, and that still just gives you 0.01 m/s per meter coil. There is nothing to stop you from having a 100 kilometre long coil giving you 100-1000 m/s, but now alignment becomes really tight: assuming the ship fills half of the coil diameter and is 50 meters across, the aspect ratio will be 1:2000 - a deviation from the axis of 0.025 degrees will lead to disaster. I like the idea of coil waystations (there was a grand sketch of how such a system might look in the singularity subplot of Barnes "Mother of Storms"), but I think they are hard to actually get to work.

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Sat, 2013-02-02 11:21

Erenthia

I will take a look at Mother

I will take a look at Mother of Storms, but I'm not looking for too much detail. The question I'm trying to answer is, "given a system wide infrastructure how much faster could ships travel throughout the solar system" I was originally thinking something like a network of coil-guns would be the best way to go, but even a giant infrastructure of metallic hydrogen "gas stations" would be conceivable, albeit more subject to piracy. The point is not so much the nature of the infrastructure. So if I said, "travel times are reduced by 75% from core EP" because of this infrastructure would I be off by too much?

—

The end really is coming. What comes after that is anyone's guess.

Sat, 2013-02-02 12:54

Arenamontanus Arenamontanus's picture

It is just a page or two in

It is just a page or two in the novel, but his system largely used railguns launching streams of metal that an attached coil on the ship used to gain momentum. So in a sense it was the reverse. (The novel has a few EP-usable ideas in the singularity subplot - this is how really enhanced people lived just up to the Fall - but the rest of the novel is mainly meteorology porn, plus elements of violence porn against guilty and innocent people/cities). I think the delta-v you can get from this kind of system is mildly limited. While you don't suffer the rocket equation, the velocities of stuff involved likely are not going to be enough to truly change things. Assuming it to be two or three times better is probably safe, but not orders of magnitude. (Of course, coilguns can really send you off at high speed if you can stand high acceleration or have a long coilgun. In an upcoming paper we use coilguns to send probes at 99% of lightspeed. The energy demands are, however, a tad high. )

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Sat, 2013-02-02 13:09

Erenthia

Based on the nature of EP, I

Based on the nature of EP, I've decided that this system would very rarely -if ever- be used by biomorphs. In fact it would make more sense to be used by ships with special, g-hardened synthmorphs. That seems like it would dramatically increase the amount of delta-v you could squeeze out of the system. And if you really need to move your biomorph from one place to another, you package it.

—

The end really is coming. What comes after that is anyone's guess.

Sat, 2013-02-02 13:48

#10

NewtonPulsifer NewtonPulsifer's picture

You're not likely to get more

You're not likely to get more than 40km/sec top speed. So for a fusion passenger ship with a 400km/sec delta-v (top speed 200-400km/sec depending if it aerobrakes/aerocaptures at the end). Bulk cargo ships usually have only 40km/sec delta-v. So for "bulk" travel it could reduce travel times by up to 66% but it would only reduce fusion passenger liners travel time by 16.7% or less. EDIT: The speed difference is analagous to upgrading your 100km/hr train system to 300km/hr. Very nice, but the 1100km/hr (okay now 1300km/hr - the analogy breaks down a little here) passenger airline is still going to get you there much faster. Oh, and the trip usually takes like a week per AU of distance on the passenger airline. Okay, this analogy sucks :)

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Sat, 2013-02-02 15:18

#11

Erenthia

*writes those numbers down*

*writes those numbers down* gotcha. It sounds a lot like when phone networks were first laid down. The infrastructure is so expensive that it's hardly worth using, but once that's paid off it's really just the cost of energy. I think the killer app for this infrastructure is the ability to not use fuel at all (and it's faster than with solar sails). I may swap the coils for a constellation of high powered lasers (or use both) but that part I can work on my own. Thanks

—

The end really is coming. What comes after that is anyone's guess.

Sat, 2013-02-02 16:21

#12

NewtonPulsifer NewtonPulsifer's picture

Yes a kitchen sink approach

Yes a kitchen sink approach might actually be the most cost effective (laser, magsail, coil guns launching canisters of fuel to the ship all together etc.) To be able to pull 40km/sec with only metallic hydrogen positional thrusters in the equivalent of a cargo container could make "slow" transport exceedingly cheap.

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Thu, 2013-02-07 11:54

#13

Static DET5 Static DET5's picture

Came to say this...

Came to say this... "To be able to pull 40km/sec with only metallic hydrogen positional thrusters in the equivalent of a cargo container could make "slow" transport exceedingly cheap." The big deal is moving stuff cheaply. If you want to move stuff any other way, you can throw money/resources at it, which will let you move it the way you want to. I think you've got a plausible system for moving resources throughout the void. I could easily see this system being used to toss ice towards the inner system. Erect the magnetic launcher (one coil, several coils, pick your flavor) and power it (How much fusable material do you have?). Pack your cylinders full of ice (the cylinders could be reused) Use ion thrusters to aim your launch system (Again, you've got reaction mass as long as you have your mine-able ice ball) Mag-throw your mass down the gravity well Fine tune your vector using the onboard ice payload and more ion thrusters You really don't need a "catch" module with this scenario. Launch towards another gravitational body and use gravity braking to slow the payload. You could use an identical launch system to slow the payload. It makes sense to have them (launch systems) at the destination so that the payload canisters can be launched back up the gravity well. Someone might want to look at the economies/mathematics involved. Launching payload canisters towards the outer rim with anything in them may not be as practical. Out on the mining side, once the resource is depleted, pack the launcher system up and move on to the next location.

Thu, 2013-02-07 14:06

#14

Erenthia

And that gives me a plausible

And that gives me a plausible method for how the system evolved. It would have started with a series of coil guns designed and put in place for terraforming Mars. Once people started living in the Main Belt, they would have modified it to send generic cargo between Mars and the Main Belt. After that happened people would start realizing the utility of the system and set up habs with a little distance between them and the coil guns (for safety purposes) but probably within a short flight of them. New settlements in other places would setup coil guns to be part of the network and eventually laser boosting and in-flight refueling via rail-gun delivered fuel canisters would be added. Additionally, the coil-gun stations probably keep a few cargo-pods loaded with ice or rock on standby just in case they detect a rogue cargo pod, one either accidentally or deliberately set on a course that would destroy a habitat. If such a rogue is detected it can load up the standby pod and shoot the rogue pod out of the sky - so to speak. That adds a lot to the system, thank you.

—

The end really is coming. What comes after that is anyone's guess.

Tue, 2013-02-12 17:29

#15

athanasius athanasius's picture

i'v read about commercial

i'v read about commercial stations that boost passing spaceships traveling around with coilgun mass streams in Rimward. Is more cost effective accelerate fuel pallets toward the ship, they transfert momentum and can be used for omnidirectional thrust. Is also possible to create stations that collect enetgy than beam it to target ships acting as external, stationary engine, using both metods your ship have an huge payload ratio but must work along whel defined route, like a modern light train... for docking use thugs!

Tue, 2013-02-12 18:27

#16

Quincey Forder Quincey Forder's picture

athanasius wrote:i'v read

athanasius wrote:
i'v read about commercial stations that boost passing spaceships traveling around with coilgun mass streams in Rimward. Is more cost effective accelerate fuel pallets toward the ship, they transfert momentum and can be used for omnidirectional thrust. Is also possible to create stations that collect enetgy than beam it to target ships acting as external, stationary engine, using both metods your ship have an huge payload ratio but must work along whel defined route, like a modern light train... for docking use thugs!

On which page did you see it? That system reminds me a lot of what you could see in Cowboy Bebop or Zone of The Enders; Dolores, I. If it was used during the Pre-Fall system expension, it's likely they're now disaffected, derelict and occupied by squatters, be them Scum, Brinkers, Exhumans or something even worse Good setting if you want to have a bit of an old school DMT style donjon in EP universe

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