# Original space travel idea?



## cakrit (Apr 27, 2013)

Hello everyone, I have searched a bit for an appropriate forum to discuss an idea I had, about sending space probes (or robots/jump-gates whatever) to distant stars. The method I am about to describe is unlike any ideas I am personally aware of and has the following advantages over them:

Achieves near-light speed, without exotic propulsion systems.
Eliminates the risk of losing the spacecraft due to system failures, collisions etc.
Does not rely on the discovery of unknown physical laws or methods to circumvent the speed of light barrier.
It also has some disadvantages:

Can not be used to transport living organisms (single cells maybe, but that's another story).
Requires technology that may not be available for several decades.
The idea is to accelerate individual supercharged nanites near the speed of light and direct the nanite beam towards the target planet in such a way, that the beam is trapped by the planet's magnetic field and ends up orbiting the planet. At that point, either via some kind of built-in mechanism or a trigger signal sent after the beam, the nanites are activated to form a utility fog that assembles the probe.
The following capabilities are required:

Nanotechnology that allows a space probe to emerge from an appropriate utility fog.
A means of either supercharging the individual nanobots, or encapsulating each of them in charged capsules.
Instruments that permit accurate determination of the magnetic field around a distant planet.
A means of accelerating the charged nanobots or capsules to very high speeds, e.g. with a space-based accelerator, similar to our particle accelerators.
A means of targeting the beams of nanobots/capsules so precisely, that we can guarantee that a sufficient percentage will end up orbiting the target planet, in a very precisely determined orbit.

I've made some calculations regarding the necessary charge (physics major back in the days) and it looks like it could be done 

The wildest part of the idea is the utility fog part, which will probably soon escape the realm of science fiction. What do you think? Have you read anything similar in a sci-fi novel?


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## cakrit (Apr 27, 2013)

Since I'm a newbie and not allowed to post links, my calculations give the following for a spherical nanite:
For a mass m = ~10-16Kgr 
the required surface charge density D = ~1C/m^2

Negatively charging the sphere (adding electrons) would result in high field emission(i.e. the charge would dissipate). Advances in Field emission suppressing technology may be required to ensure that the necessary charge is maintained. Alternatively, the material could be positively charged and have a lattice structure such that the ions are held firmly in place.  

Accelerating the mass would require an accelerator like the LHC, which currently accelerates bunches of ~10^11protons  which have exactly the proposed mass (*10-27Kgr/proton = 10^-16Kgr). To accelerate 2808 bunches in a single beam, the LHC requires 362MJ per beam.


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## BetaWolf (Apr 27, 2013)

Assembling the probe from nanobots once it arrives at its destination does seem original, but I've no knowledge of the physics involved, so I can't help you there. Now that I think about it, you could also turn it around and write about alien contact on Earth based on the same principle. Good luck.


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## Ursa major (Apr 27, 2013)

That is an interesting concept, cakrit. (I can't say whether it's original or not, but I've never heard of it.)


My only concern (driven as much by my own ignorance as anything else) concerns the events at the far end. Given that something accelerated to near the speed of light and then aimed through a near vacuum is likely to be travelling close to the speed of light at its destination, I have my doubts whether a planet's magnetic field is going to be able to permanently capture, in orbit, your nanites. I can see some hitting the planet, and some whose course might be altered, but not being captured.

However, I'm open to being persuaded that this is, indeed, possible.


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## jastius (Apr 27, 2013)

what about a chemical condensation filter that would draw away electrons into .. say hydrogen which would be supercooled in space and allow itself to be used as a temporary crystal matrix that could dissipate into the cloud as a matter source upon arrival. advances in hydrogen bubble memory systems have been made.  that way as long as everything is cold. nothing happens. its stable.   i think you have to get into fractilization though for actual unit building.  you need something that requires no extra go button. a chemical fractal program held in cold stasis would work.

have you seen the new carbon building triggers? who would have thunk that basic carbon that is used in so many carbon fiber technologies is more electron attractive then metals of any nature?  but you could have your little go-bot pick up the stuff as it travels then use lightning as a power agent... of course that would mean descending to the troposphere of said planet.


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## BetaWolf (Apr 27, 2013)

Ursa raises a good point. You would need some opposing force at the other end to decelerate the nanites.


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## jastius (Apr 27, 2013)

just have the whole thing crash into the atmosphere, it will decelerate and bounce along a bit skipping over the surface, then it should attain a proper orbit.


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## Overread (Apr 27, 2013)

jastius said:


> just have the whole thing crash into the atmosphere, it will decelerate and bounce along a bit skipping over the surface, then it should attain a proper orbit.



That sounds rather messy - ok for a single object, but for a stream of nanites that then have to find each other and reassemble into a functional object I could see that they'd have such a high chance of spreading out and losing each other that you'd have to send an excess of nanites for whatever it was you wanted to build. 

That could work if you could design some kind of docking station - so you fire a massive stream of nanites at the target, whereupon it constructs a docking port which acts as a focus for more nanites so that you can then stream more and have most if not all collect at the dock (and then reassemble).


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## nightdreamer (Apr 28, 2013)

This does strike me as a truly original idea; I've never come across anything like it.  And for that reason alone, it is worth pursuing.  But the technological challenges will be pretty steep.

In particular, you could never send a charged beam between star systems for a number of reasons:

1. As you do so, the potential between the beam and its source would continuously increase, requiring ever more energy to continue to send nanoparticles.  At some point, the potential would eventually pull them back.  For positively charged particles, for example, you would also have to project a negative charge such as electrons to keep the charge balanced, and they would eventually find each other, resulting in a neutral beam.

2. A charged beam would repel itself and disperse.

3. There is a galactic magnetic field and local stellar magnetic fields than can be very complex and chaotic, especially around neutron stars and black holes.  These would make aiming a charged beam across interstellar distances very difficult.

On the other hand, if the beam were neutral, it would not be trapped by a planetary magnetic field at the other end.

I don't want to discourage you because the idea is so cool that it deserves to be pursued.  The utility fog is especially interesting.  I'm wondering if you can do something with quantum entanglement there, but that would be bordering on new physics.

Above all, don't give up.  I'd like to see where this idea goes.


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## BetaWolf (Apr 28, 2013)

Interesting post, nightdreamer. Might I suggest starting the story with testing it closer to home? Mars or a Jovian moon perhaps? If the story is about developing the beam itself and getting it to work in say Alpha Centauri system.


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## cakrit (Apr 28, 2013)

Wow! What a wonderful forum! Thank you all. I will address each reply separately, so I can reach my quota soon enough and be able to add links for reference.
It will take some time and I'm on GMT+3 timezone, so bear with me...


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## cakrit (Apr 28, 2013)

BetaWolf said:


> Now that I think about it, you could also turn it around and write about alien contact on Earth based on the same principle. Good luck.



The idea actually came to me by playing a sci fi scenario in my head. We contact a distant alien species via normal electromagnetic signals and they ask for our permission to construct a jump gate around our planet, so they can come and speak to us in person (because communication takes several years). They have no way of knowing the exact magnetic field around our planet and in our solar system in general, so they can't do it if we don't give them the information. What would it take for us to trust them enough to give them the info?


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## cakrit (Apr 28, 2013)

Ursa major said:


> I have my doubts whether a planet's magnetic field is going to be able to permanently capture, in orbit, your nanites. I can see some hitting the planet, and some whose course might be altered, but not being captured.





Overread said:


> That sounds rather messy - ok for a single object, but for a stream of nanites that then have to find each other and reassemble into a functional object I could see that they'd have such a high chance of spreading out and losing each other that you'd have to send an excess of nanites for whatever it was you wanted to build.



Quite messy, indeed. As nightdreamer said, we are talking about chaotic systems. It would be extremely difficult to manage to get the nanites hitting the magnetic field at exactly the right angle and yes, maybe only a fraction of them would end up at just the right orbit. But we don't really care, because it's just a matter of piling up more and more of them. The better we get at it, the higher the percentage of the ones that do get captured. The main question is how you can manage to get at least one to get captured, as nightdreamer said:



nightdreamer said:


> There is a galactic magnetic field and local stellar magnetic fields than can be very complex and chaotic, especially around neutron stars and black holes.  These would make aiming a charged beam across interstellar distances very difficult.
> 
> On the other hand, if the beam were neutral, it would not be trapped by a planetary magnetic field at the other end.



Remember that the assumptions include precise determination of the magnetic fields involved and precise targeting capabilities. The latter may be much easier than the former (see my previous post, regarding aliens asking for data from us, because they can't do it by themselves).

Still, the key is that we are not sending a single, continuous beam, but short packets of charged mini spheres. We could even send them one at a time, if it made more sense. The main question is, can we know where each of them ended up so we can correct the next batch? I'm not sure and it might involve adding some kind of trace signal to each nanite.




Overread said:


> That could work if you could design some kind of docking station - so you fire a massive stream of nanites at the target, whereupon it constructs a docking port which acts as a focus for more nanites so that you can then stream more and have most if not all collect at the dock (and then reassemble).



Definitely cool idea. The nanites would somehow have to find each other if they are ever to form the cloud. I haven't thought much of exactly what would need to happen on the other end, until we end up with a solar-powered satellite moving at much slower speeds than c, but I will explore that further.


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## cakrit (Apr 28, 2013)

nightdreamer said:


> In particular, you could never send a charged beam between star systems for a number of reasons:
> 
> 1. As you do so, the potential between the beam and its source would continuously increase, requiring ever more energy to continue to send nanoparticles.  At some point, the potential would eventually pull them back.  For positively charged particles, for example, you would also have to project a negative charge such as electrons to keep the charge balanced, and they would eventually find each other, resulting in a neutral beam.
> 
> 2. A charged beam would repel itself and disperse.



Regarding #1, I don't think I properly explained how the "beam" works. We use an accelerator to slowly  increase the speed of a batch of nanites (they are charged, so it can do it). Each nanite in the batch leaves the accelerator by itself and just maintains its momentum. I don't know if the potential buildup at the target would become an issue, but it has to do with what exactly happens after they are in orbit. I suppose that the nanites will have to start attracting each other at some point, in order to begin interacting with each other, which brings me to #2. 

Even if it were a continuous beam of charged nanites we would be sending, my understanding from my physics days is that would actually become more focused. Moving charges generate magnetic fields in such a way, that they actually attract nearby charges moving in the same direction. It's the reason electrical wires attract each other. If you are aware of a different mechanism for ion beams, please share, I could not find anything.


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## cakrit (Apr 28, 2013)

BetaWolf said:


> Might I suggest starting the story with testing it closer to home? Mars or a Jovian moon perhaps? If the story is about developing the beam itself and getting it to work in say Alpha Centauri system.



Of course that would be the only reasonable way to start. You crawl before you walk!


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## cakrit (Apr 28, 2013)

jastius said:


> what about a chemical condensation filter that would draw away electrons into .. say hydrogen which would be supercooled in space and allow itself to be used as a temporary crystal matrix that could dissipate into the cloud as a matter source upon arrival. advances in hydrogen bubble memory systems have been made.  that way as long as everything is cold. nothing happens. its stable.   i think you have to get into fractilization though for actual unit building.  you need something that requires no extra go button. a chemical fractal program held in cold stasis would work.
> 
> have you seen the new carbon building triggers? who would have thunk that basic carbon that is used in so many carbon fiber technologies is more electron attractive then metals of any nature?  but you could have your little go-bot pick up the stuff as it travels then use lightning as a power agent... of course that would mean descending to the troposphere of said planet.



Please elaborate. I am not aware of the technologies and how exactly they might be applied here. The problem to be solved at the destination is how to get from single nanites orbiting at near-light speeds to a solar-powered mechanism that managed to reduce its speed and orbital radius. To get to the troposphere you first need to slow down, without losing your charge. How do you do that? I don't have any answers yet, I was more focused on whether it's possible to send them in the first place. I will definitely start thinking about it and it seems like you may have something here.


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## Brian G Turner (Apr 28, 2013)

Other concerns would be:

- Both the originator of the beam and the target will be in motion, so that would need to be corrected for
- You are still going to have to construct an incredibly massive number of nanites to cover distances measured in the span of light years
- Even at the speed of light, it is still going to take years, decades, millenia, to connect with non-local targets

So far I think the main problems are the sheer volume of material nanites required would be restrictive, plus the big challenge of breaking the light barrier has not been addressed so any success will take an extremely long time.


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## jastius (Apr 28, 2013)

use the charge.. ( use the force luke...) 
okay so you have a positively charged thing that is basically being slingshoted like a superball through galactic outer regions because of its slickness in being positively charges. well the problem seems to be 1- how do you keep the beam going, and  2- how do you get it to stop.   both of these problems can be solved through limited fusion capabilities. splitting hydrogen. that way you get a bomber load of these things collecting around each other like a snowball rolling down a hill as they travel, using their own power source as fuel ..  at the other end you have a creature of enough mass to begin the replication cycle and as these hydrogen atoms are attached in bubble memory matrix form the blueprints continue for the replication of the original machine form. 
once there at super light, the smooth super bouncy has to transform into soft and sticky to adhere to its planetary orbital. when we are talking about nano size the atmosphere is hit by that stuff all the time. but you take a whole wack load of positive and try to bounce it off its polar opposite, you have a whole bunch of sticky all of a sudden. stasis, and result in out-surge of energy. the energy starts the process by unlocking the fractal building program. the nanos would have to be composed of something that would be readily available at the other end and has a matrix that can lend itself to hydrogen bubble memory and carbon came to mind. plenty of building materials in that. you see you can not have traditional computer memory systems in a beamed object... you  have taken apart the positives and negatives that make it up and there is no way to to retro start a chip upon your destination so you have to use a different tech to bypass this problem. then the problem after that is containment fields for the different aspects of the nanos and a trigger to start reaction, which has to be something available upon reentry. there is no light speed remote control system. so no signal from here and no signal capable of being carried equals chemical signal upon achieving a certain predetermined state. after that the problem is in replication. .. but the best way i know of in non-programming programming is a chemical fractal convergence matrix. that wakes up when you get there. the fractals automatically start rebuilding themselves in the nature of all fractals and upon converging rebuild your nanos into machines. i just like the idea of a triple based trigger system- energy / light/ gravity/ electro magnitism / heat vs. cold... otherwise the thing might sticky to a singularity and when the aliens jump through or we do there'd be some mighty unhappy campers.
i love this thread.. super cool idea and very god in the machine concepts.


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## cakrit (Apr 28, 2013)

I said:


> - Both the originator of the beam and the target will be in motion, so that would need to be corrected for


Obviously. You also need to avoid the Van Allen belt, which is teeming with annoying particles trapped in orbit at near-light speeds. 



I said:


> - You are still going to have to construct an incredibly massive number of nanites to cover distances measured in the span of light years



You don't need a continuous beam. You send a few bunches, then wait for a few years, to see if your calculations were right (assuming you can track them, of course). You then send more and more of them, always in bunches.



I said:


> - Even at the speed of light, it is still going to take years, decades, millenia, to connect with non-local targets


Of course. The speed of light barrier is a bummer, but we don't know if and when we'll be able to circumvent it. BUT, suppose the way we do actually get around it requires two jump gates that somehow utilize entaglement for teleportation. We can send the nanites with half the entagled particles at light speed to our destination, so they can construct the remote gate. We can then teleport what we want from our gate, instantly. 



I said:


> So far I think the main problems are the sheer volume of material nanites required would be restrictive, plus the big challenge of breaking the light barrier has not been addressed so any success will take an extremely long time.



The amount of nanites depends only on two things, the number you need orbiting the target and your accuracy (i.e. what % of the nanites you send actually achieve orbit). I really don't know which of the two would be the biggest issue. Still, my guess is that the cost of building and maintaining an accelerator like the LHC in space would probably be orders of magnitude higher than the cost of constructing the huge number of nanites needed.


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## cakrit (Apr 28, 2013)

jastius said:


> 1- how do you keep the beam going



You don't need to keep it going. Inertia does it for you. There's nothing in the way to slow it down. 

I will try to digest the rest of your post. It's all very new to me, so I have to do some reading first.


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## chrispenycate (Apr 28, 2013)

I'm not sure it would be possible to get enough information into a true nanite that the build up to a complex system would be possible. I know, practically all stories based round nanotech assume von Neumann capabilities, while all present experiments are concentrated on nanites created within a larger framework, and it's only faith that makes the linkage, but you could use larger projectiles, dust-grain size. The optimum would be that every particle contain all of the information, plus some limited read out and manipulative possibilities and energy handling - whoops, we're up to the size of a living cell.

The charged particles are going to actively repel each other, in orbit as well as in transit; outside of the nucleus electrostatic forces are among the strongest we know. You could possibly compensate for this by sending two beams from opposite sides of the solar system, intersecting at the target, where they attract each other and neutralise, so they can co-operate in building their larger structure. This still doesn't get rid of that relitavistic mV, which I can't see any mere planetary field absorbing (and atmospheric friction? On something that size with that much energy? I love the idea of the blue trails of Cherenkoff radiation as the individual nanites are heated to millions of degrees, massive cosmic rays colliding with air molecules, but there's no way to get rid of enough energy with a passage which doesn't include a fair amount of the planet's crust that they're not still way above escape velocity). Perhaps a close approach to the star, using its considerably more intense magnetic field to bend the beams into planetary orbit while decelerating them? Probably not, even then; there's really a lot of energy to dispose of.  

And there's no feedback for the fractions of second of arc that make the difference between your target planet and a next door galaxy. Photon pressure, variations in solar wind; the slightest deviation at source, a touch of Heiseberg, or even a tough of Murphy, and there's no correction factor possible. Most of your original particles will be lost (which is why it's better not to distribute the data between lots of different travelling paths).


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## Vertigo (Apr 28, 2013)

I agree with Chripsy your problem is going to be losing all that speed at the destination. Travelling at near light speeds mean that capturing the nanites into orbit would be almost like trying to capture the protons in a beam of light into orbit.

Not sure what the answer to that one would be, but I like the idea; quite novel!


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## jastius (Apr 28, 2013)

chrispy this is why i think the best possibility at the moment is a fractal building type thing. if even one nano reaches destination then the fractrals will build into the the type of cloud machine matrix he is talking about. fractals are absolutely delicious, very complex results from small amounts of information and if you have converging fractals you can achieve something as complex as dna and even a human body. it would be possible in this manner if you had a chemical memory source to rebuild a human being upon another planet  far far away...  of course there is no guarantee that the individual thus created would run true to form. 

and we are talking subatomics here. negligible size of discharge but more then enough to power up a building field inside the matrix. and i agree with you that the beam needs some kind of guidance, chrispy. i think reliance upon inertia is too problematic. that is why i suggested a renewing beam that would adjust to target upon each renewal. refocus, refocus, refocus...

as for tracking..though sound doesn't travel as fast as light you could use a sound pulse set off before the package was sent to bounce off the package and return at destination... 
then you just wait for the call to come through.


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## cakrit (Apr 28, 2013)

chrispenycate said:


> The optimum would be that every particle contain all of the information, plus some limited read out and manipulative possibilities and energy handling - whoops, we're up to the size of a living cell.



In my calculations, I have assumed nanites with mass ~10^-16Kgr, which is 100 times less than a cell and 10 times more than a virus. The heavier they get the more information they can carry and the more capabilities they can have, but the harder it is to accelerate them and charge them enough so that they can get trapped. Both of the latter are engineering problems of course and you can simply throw more money into them. The exact nature of such a cloud is definitely the most speculative part of the idea, but we know that nature has managed to build exquisite little machines that do a hell of a lot more than what we are asking here. 



chrispenycate said:


> The charged particles are going to actively repel each other, in orbit as well as in transit;



I have to repeat that charges moving in the same direction actually attract each other, due to the magnetic fields they generate. The electrostatic force will come into effect if we slow them down before they lose the charge. I will try to do the calculations to see what exactly happens between two charges moving in parallel, but there should be an equilibrium distance inversely proportional to some power of the velocity. 



chrispenycate said:


> You could possibly compensate for this by sending two beams from opposite sides of the solar system, intersecting at the target, where they attract each other and neutralise, so they can co-operate in building their larger structure.This still doesn't get rid of that relitavistic mV...


Yes, the first version of my idea had two beams travelling in opposing directions and colliding on the other side of the planet. However, the collision would most likely turn everything into a mess of exotic particles and high energy radiation. Moreover, the attraction would only manage to deflect most of the nanites and send them outside the orbit. 



chrispenycate said:


> there's really a lot of energy to dispose of.


I know! I don't have an answer right now. My first idea was that the slowing down would be handled by the first structure they would build (let's call it the caterpillar stage). The caterpillar's job would be to collect the other nanites (how?) and gather enough energy (from photosynthesis or collisions with other particles?) to slow down, until it can enter a lower orbit. As it the machine grows, the orbit begins to be determined by gravitational rather than electromagnetic forces. There are quite a few ideas you have all proposed and I need time to think about them (or understand some of them!). 



chrispenycate said:


> it's better not to distribute the data between lots of different travelling paths).


Definitely! We expect to lose most of them on the way.


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## jastius (Apr 28, 2013)

but cakrit if they snowball they will slowdown.


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## cakrit (Apr 28, 2013)

I was wrong regarding the attraction of moving charges. At the speed of light, the electric and magnetic forces would simply cancel each other. At anything below that, the electric force takes over and they start repelling each other. Wires with moving currents are attracted to one another because they are not charged, so the only active force is the magnetic one.


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## cakrit (Apr 28, 2013)

jastius said:


> but cakrit if they snowball they will slowdown.



As I said, I'm still trying to understand your idea. We have no idea of how exactly the 'snowball' is spinning at any given moment, so I don't know how it would know which way to eject (what and when?) to increase or decrease its momentum. It was your ideas that I need to think about, along with a couple of other suggestions. Analysis is easy. Synthesis is a bitch.


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## cakrit (Apr 28, 2013)

jastius said:


> but you take a whole wack load of positive and try to bounce it off its polar opposite, you have a whole bunch of sticky all of a sudden. stasis, and result in out-surge of energy.



I said before that I didn't get how the 'snowball' would be able to reduce momentum and then I thought that the above was what you expected would slow down the nanites. What exactly do you mean by the polar opposite? Where did we find the negatively charged pole? Magnetic poles are totally different.


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## Abernovo (Apr 28, 2013)

I've never seen anything like this, so as others have said, it's worth looking at. Apart from the problem of losing speed and energy at the far end of the journey, I can see another potential pitfall. 

That is, the actual motion of the stars and planets over time. Because everything is moving, you have to aim the beam to where the distant star or planet will be at point X, taking into account that you've got fossil light coming to you and fluctuations and wobbles may take place. The issue gets more complicated the more distant the target is, both with the lag in information and with more objects potentially crossing the beam's path.

There you are, having it planned out, and an asteroid, its orbit altered by an unexpected and uncalculated encounter with a gas giant's gravity, cuts through the beam, knocking 20% of the nanites out. The end result would be a failure, and you wouldn't even know it, unless you possessed a quantum entanglement messaging system (yes, I've been reading Nancy Kress ). This could be one of the touches of Murphy that Chrispy referred to.

Not a deal-breaker, but one that would require significant calculations on the team sending the nanites out and the smallest error could result in total failure, which itself could be a plot thread. I think you'd need a high redundancy level for the nanites.


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## jastius (Apr 29, 2013)

according to this guy it is a multilayer field not just one pole or the other.

* Magnetic fields of the earth *



​
   The Earth's magnetic field on Earth this is not equivalent to a  magnetic dipole with magnetic S pole near the geographic north pole, and  the magnetic field N pole near the geographic South Pole, but rather  presents another special kind of magnetism .   It is a natural phenomenon caused by the movement of liquid metal in  the core of the planet and is present on Earth and other bodies  celestesSol.  as 

   It extends from the core gradually fading into outer space (no limit),  with known electromagnetic effects in the magnetosphere that protects us  from solar wind, but also allows diverse phenomena as the orientation  of the rocks at mid-ocean ridges, the magnetoreception of some animals  and orientation of people through compasses. 

   A compass points to the North-South direction because it is a  magnetized needle immersed in the Earth's magnetic field: from this  point of view, the Earth behaves like a giant magnet and has magnetic  poles, which, at present, do not match with the geographic poles. 


​
  The South Magnetic Pole is 1800 kilometers from the Geographical North Pole.   Consequently, a compass does not point exactly to the north  geographically, the difference, measured in degrees, is called magnetic  declination.  The magnetic declination of the observation depends, for example currently in Madrid (Spain) is about 3 ° west.  The magnetic south pole is moving through the northern Canadian northbound Alaska. 
  Posted by   Saeed Halls in   15:53 ​​No comments:


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## nightdreamer (Apr 29, 2013)

cakrit said:


> Even if it were a continuous beam of charged nanites we would be sending, my understanding from my physics days is that would actually become more focused. Moving charges generate magnetic fields in such a way, that they actually attract nearby charges moving in the same direction. It's the reason electrical wires attract each other. If you are aware of a different mechanism for ion beams, please share, I could not find anything.



Interesting that you brought that up, because there is a paradox there, and I forget how it resolves.  From a "stationary" reference frame such as the Earth, then yes, it would seem that the beam would converge because of magnetic forces.  But from the frame of the particles themselves, there is no motion, and so electric forces would cause the particles to diverge.  The problem is, the same behavior must be observed from both frames.  Either way, charged beams do diverge.  I ran into this before and had a physicist explain it to me, but I've forgotten what the explanation was.


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## cakrit (Apr 29, 2013)

nightdreamer said:


> Interesting that you brought that up, because there is a paradox there, and I forget how it resolves.  From a "stationary" reference frame such as the Earth, then yes, it would seem that the beam would converge because of magnetic forces.  But from the frame of the particles themselves, there is no motion, and so electric forces would cause the particles to diverge.  The problem is, the same behavior must be observed from both frames.  Either way, charged beams do diverge.  I ran into this before and had a physicist explain it to me, but I've forgotten what the explanation was.



See post #26. I was wrong. At the speed of light, the two forces cancel each other out. Anything below that, dispersal. So you were right and I was wrong.


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## nightdreamer (Apr 29, 2013)

Oops!  Missed #26.  Sorry.  I figured out the difference with wires pretty quick, but was still bothered by the beam, because I knew that if the magnetic field transformed with velocity, then the electric field had to also, and that's something they don't teach you in freshman physics.  I don't think we even covered it undergrad electromagnetics.  I finally found what I was looking for here, but frankly, I got lost (twice) in the derivations, so I still don't understand it.  I might run over to the physics department someday to get another explanation in English, but probably won't unless I really have to know. C'est la vie!  Anyway, keep working on it.


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## chrispenycate (Apr 29, 2013)

Encapsulation! 

Our major problems are divergence of the beam due to electrostatic repulsion and lack of any auto correction once en route, right (apart from the nano bit, but that's just engineering)? And slowing down. So we build a container for the bits we want to arrive, and we don't give it a charge, we make its shell conductive. Quite a big shell, about the size of a pinhead, and sophisticated to the level of the nanotech.  Now we use a Laithwaite linear accelerator – a 'rail gun', but the coils on this are spaced at planetary diameters, rather than centimetres, and the entire thing is a couple of AU in length (of course we build it in space; nowhere else is big enough). No rigid structure, you use laser interferometry to detect the precise position of the coils and adjust the polyphase generator to compensate for imperfections.   

The shell is big enough that brownian movement due to photon impacts and random gas molecules is essentially eliminated, and sophisticated enough that it can be directed to make minor course corrections (extremely minor, but anything more than that would require fuel reserves, and a rapidly escalating mass/complexity. Better to accept a certain loss percentage).

Shortly before arriving in the target system it deploys its parachute, monomolecular thickness metallic film (any conductor, doesn't have to be ferromagnetic; Heinlein got it wrong in TMaHM) which uses photon pressure and solar wind as a first braking measure, dandelion seeds and was the conductor to which the linear accelerator applied the original forces to get it up to cruising speed (yes, you could deploy the parachute as soon as you've left the accelerator, build an immense laser bank/power generator in Mercury orbit and add a few more metres per second with photon pressure, but light sails are old hat ).

As you pass close by the planet you eject the nanites with enough velocity that they are captured into orbit, incidentally accelerating the empty capsules up to nearly as fast as their original cruising speed (yes, I know. Ejecting the nanites directly towards the parachute. Either you can use an annular parachute and aim through the middle, or gut your chute loose assuming the extra pressure on it will take it far away from your main container 


Black marks; Vertigo, it's photons, not protons and jastius:- shame! Sound in space? It'd have to be electromagnetic, laser or maser, and could double up as communications and doppler radar.

And information theory states that, fractals notwithstanding, there is a definite lower limit to how much data is needed to describe a system of a certain complexity. If you wanted to describe a uric acid crystal or a honeycomb, that's very little data, if you wanted to describe a bee, or my toe joint in which that acid is crystallising, that's a whole different question, and if you wanted to describe the ecology, flowering plants and social insects you need masses more irreducible data. Not that we couldn't compress data a long way, but you can only acquire so much information, it is not infinitely expandable.


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## Vertigo (Apr 29, 2013)

chrispenycate said:


> Black marks; Vertigo, it's photons, not protons and jastius:- shame! Sound in space? It'd have to be electromagnetic, laser or maser, and could double up as communications and doppler radar.


 
Whoops, missed that Chrispy, honestly, I did mean photons.


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## jastius (Apr 29, 2013)

radiowaves chrispy, television transmission signals  etc, not sound per se but a signalling device sent out before it is needed. then as the bitty bots cross the paths they recorrect their course.  ... and i did say encapsulate the bitty bots.. i suggested an exterior matrix thingie to hold memory and rejigger more bitty bots en route.
and crispy if they can make an artery upon a computer bio-printer why can't the bitty bots carry the equations to reprint what is basically a two dementional vortex gateway splash-pad. the interstices of the fractals will coalese into the more complicated equations. we aren't talking about a star trek transporter on the first run out, only that  would be possible with work to encode information that way and transfer it. and as for biomatter, chrispy you don't have to recode for the whole structure, only one living cell and a grow thing to prepare it in. it would hold its own instructions for reforming.  
(and chrispy, you need more cranberry juice for your poor toes.)


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## cakrit (Apr 29, 2013)

@crispy
- Getting rid of the charge when you no longer need it, is not that hard. If you negatively charge it you just create a spike on your surface, if you positively charge it you can either collect the electrons trapped in the Van Allen belt, or generate them. And of course, you could probably have an outer charged capsule that releases a neutral nanite. If the shell isn't charged when it gets there, my understanding is that you rely on gravity for the nanite that gets shot out of the capsule to orbit the planet. Correct? 
- What kind of momentum reduction could we expect from such a sail? If we can slow down the structure enough, then there's no need to shoot the nanites in the opposite direction. We just reduce the speed enough for gravity to take over. 
- If the momentum reduction is not enough, shooting the nanite in the opposite direction is certainly a good idea, but the energy required depends on the entire structure's momentum vs the mass of the nanite itself. If the capsule's mass is comparable to the nanite's mass we need a big explosion and it would be very hard for the nanite to survive it. If the capsule is much much heavier than the nanite, it will take a hell of a lot more energy to send it there.
- I'm not convinced that any course corrections will be feasible. The structure will probably be spinning like crazy, unless you include yet another mechanism, to correct for the spin (i.e. more mass and more energy).

One thing I never took account of in my calculations is the effect of the near-light speed on the momentum (the nanites will behave like they have more mass than they actually do). I just ignored gravity altogether and I think I need to add it to the calculations.


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## chrispenycate (Apr 29, 2013)

Spike? You obviously didn't do valve electronics. Spike will work fine in atmosphere where there are some molecules to ionise; not so effective in vacuum.

Yes, I want the orbit set by gravity. It might pretty feeble relative to electro-magnetic forces, but it doesn't go round in pairs, attractive/repulsive, like girls at a dance. So it doesn't tend to cancel out with distance.

I really don't think we can get enough delta v from a light sail to bring us from relativistic speeds down to interplanetary, and gravity's not going to help. I was assuming nanites were close enough to solid state to take fairly brutal accelerations; I cheerfully admit it would be nice having a long, thin capsule so deceleration could be applied more gradually, but a) something long enough to make an appreciable difference would be more massive, more energy requiring in the launch system and b) – well, a needle just isn't as convenient a shape to steer as a sphere. Nothing to do with air resistance, just dynamic stability.

Oh, sorry. I haven't selected your idea to throw stones at, I just get this way occasionally. Most of the long term residents are used to me  by now. Welcome to the Chrons; intense enough for you?


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## cakrit (Apr 29, 2013)

Turns out that the gravitational force can be used only after we get down to around 10^3m/sec (for a geo-stationary orbit at around 10^7m). For a circular orbit, the mass of our object has nothing to do with it. The mass cancels out and the only things that matter are the orbital radius and the velocity.


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## cakrit (Apr 29, 2013)

chrispenycate said:


> Oh, sorry. I haven't selected your idea to throw stones at, I just get this way occasionally. Most of the long term residents are used to me  by now. Welcome to the Chrons; intense enough for you?



Are you joking? I'm loving this! But really, maintaining a high charge is much harder than losing it, due to field emission. I am finally able to post a link to my calculations.

We WILL get it (and I hope it will not require entering the atmosphere and magically surviving it).


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## cakrit (Apr 29, 2013)

I think we might be able to work with elliptic orbits. The speed will be near c at the pericenter and lower (can't tell by how much right now) at the apocenter. There may be a way to gradually release charge, so that at each pass from the pericenter, we have a lower speed. This type of calculation will be a bit hard for me, but I'll try to give it a shot. Oh, and this type of method would most definitely require corrective actions. There's probably no way to avoid the effect of solar wind etc if you start having large ellipses.


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## Vertigo (Apr 29, 2013)

That's your problem I suspect (the detailed physics for this one are beyond me sadly) but I suspect an elliptic orbit with near C speeds at the pericentre is going to be and awfully big orbit with an extremely long period. Sadly, I also suspect any attempt to bring that speed down is going to take so long it might negate the benefit of sending it at such high speeds in the first place.


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## chrispenycate (Apr 29, 2013)

Ah, you're thinking of a little accelerator, like the LHC. Hardly reaches St. Genis from Meyrin (I live on the other side of Geneva). And goes round and round, with the velocity and mass increasing with each circuit.

I was thinking of a big accelerator built in space, and planning for a linear, at least light minutes in length. Perhaps even a structure, but mainly held in place by continuous correction by some form of drive, probably multidirectional ion projectors. Probably fusion generators at each acceleration coil/plate. Focusing coils practically the entire length. Only a few kilowatts, those, so probably get their power either by microwave beaming or superconducting cables from the node points. Expensive, yes, but easily extendable, adaptable when you need more oomph.

Um (_takes off science pedant hat, puts it down next to grammar pedant hat, and puts on mod hat_) In this site we sort of prefer people not to do multiple sequential posts. Oh, it happens, 'specially when commenting on writing challenges, but we definitely prefer using the multiple quote function (that's the pair of commas just next to "quote”) to answering each post individually, particularly as a way of getting to fifteen posts and link. While this is primarily to discourage spammers, and I understand that your enthusiasm was not to tell people about your new book or sell sport shoes, now you can link, do you think you could restrain yourself to one post at a time, per thread? Come over to the aspiring writers region and learn to put your technical ideas into elegant, reader-satisfying prose (well, no, I haven't got that far yet). Comment on your favourite authors, learn about what other people are reading… there are lots of friendly, polite, knowledgeable even helpful residents. 

Or even, to improve your writing skills, get involved in the writing challenges. Don't get stuck in one little thread.


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## cakrit (Apr 29, 2013)

chrispenycate said:


> In this site we sort of prefer people not to do multiple sequential posts. Oh, it happens, 'specially when commenting on writing challenges, but we definitely prefer using the multiple quote function (that's the pair of commas just next to "quote”) to answering each post individually, particularly as a way of getting to fifteen posts and link. While this is primarily to discourage spammers, and I understand that your enthusiasm was not to tell people about your new book or sell sport shoes, now you can link, do you think you could restrain yourself to one post at a time, per thread? Come over to the aspiring writers region and learn to put your technical ideas into elegant, reader-satisfying prose (well, no, I haven't got that far yet). Comment on your favourite authors, learn about what other people are reading… there are lots of friendly, polite, knowledgeable even helpful residents.
> 
> Or even, to improve your writing skills, get involved in the writing challenges. Don't get stuck in one little thread.



A private message even with this paternalistic tone would have been welcome and I would have answered very politely, explaining to you why half of the things you wrote make no sense in my case. Now all I can say is good bye and too bad.


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## Mirannan (Apr 29, 2013)

Very interesting idea. A couple of points IMHO worth making: First of all, the beam spread caused by mutual repulsion could be handled by neutralising the beam just after it's been accelerated - maybe by firing a diffuse electron beam at a very narrow angle to the nanite stream.

Secondly, one way of approaching the deceleration problem at the other end might be to use aerobraking in a big way. Sure, Earthlike planets don't have thick enough atmospheres to do the job - but there is nothing to say that there can't be a stop along the way. Make the first stop for the beam a nice fat local gas giant. I imagine that Saturn would be able to stop the beam!

After all, one could design the nanites to work at optimum efficiency in a gas giant atmosphere.

What a lovely thought. Our first warning of an interstellar invasion is that the equatorial region of Jupiter starts glowing blue...


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## jastius (Apr 30, 2013)

what about slingshoting around a planet not to increase velocity but to decrease it.. oh wait. Mirannan you just said that... my bad.

Cakrit, please don't be upset; no offense was meant by any of us and especially not chrispy. its actually his job to regulate things around here. 

I looked over your equations, and they are a thing of beauty.  are you sure about the acceleration factor? no conjunctive relativism factor?  

i hope you are still peeking in. i will really miss  having a concrete problem for my head to chew on.  i haven't had this much fun since i explained to my third grade teacher why the computer hard drive kept shorting out.

And Mirannan, wouldn't that be a red shift across jupiter?  deceleration and all imitating the wavelength of a quasar...


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## Mirannan (May 1, 2013)

Jastius, my idea was a lot simpler and more brutal than that. Simply fire the beam directly at a handy gas giant. IMHO slingshotting at relativistic speeds is unlikely to work, unless you have a handy neutron star or black hole. As far as I know, the greatest possible velocity change from a slingshot is of the order of the escape velocity of the object you're using; completely trivial, when the item being slingshot is travelling at close to the speed of light.


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## cakrit (May 10, 2013)

FYI, slowing down can be achieved by induction heating (due to eddy currents) and transfer of energy to spin. Both require changing magnetic fields. For a dipole like earth, the magnetic field is stronger near the poles, which actually causes the plasma to be trapped (check out magnetic mirroring and drift). So the charged spheres can probably be captured in the same way and slowly lose both their charge and kinetic energy. I'm not going to continue here, at some point maybe I'll write a short story or something.


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