Possible acceleration systems

[The Architect]

From the Discord:

The Architect
It's for a personal project. The ship is meant to set up a colony and install "interstellar routers" in which entities coming from the main core can download themselves using something a bit similar to quantum entanglement
So he is the A.I. version of the cable guy
Also, the ship needs to be able to shoot pursuers because it passes near a volume where there is a higher probability of hostile rebels trying to destroy it
That weaponry would surely add significant weight

Drashner1Today at 2:20 PM
So - the subject of mass-beam propulsion is a large and involved one.  I'm going to provide an initial (high level - since the questions are somewhat high level at this point) answer to your questions here and then post some links to initial references that you can read to start to get a handle on the concepts. A lot will depend on the mass and speed you want for the ships - but this tech scales pretty readily, especially if you have neumann constructors to build the infrastructure.
Ok - specific (but high level) answers - Re size and frequency of the beam - This sounds sort of like a question that would apply to laser based beamed propulsion but not really to mass-beam propulsion. In other words you don't need a sail 1000 km across to intercept the beam. The beam solar power collectors and generator array can be large enough to be a naked eye nighttime object over interplanetary distances -but the actual beam it produces might be only tens of meters to hundreds of meters across.
Mass beams deliver their energy via the velocity of the beam rather than frequency (although I won't be surprised if someone here posts to say that frequency applies here in some fashion as well, but whatever.  One of the nice things with a mass beam is that you can 'tune' the velocity such that the maximum amount of energy is delivered to the target ship at any given time, making the system maximally efficient. The faster the ship is going, the faster the mass stream particles are fired at it. Lasers beams can't do this since light must always travel at the speed of light.
In terms of the size of the ship - If you really want bigger ships than a mass-beam system can support that - unless up to a very high point. But before we get to that point, I think we get into issues of what you want the ship to do, how you want it to do it, and how fast you want it to travel. Also, if you have neumann tech (which you kind of do need to make mass-beam travel practical on any large scale), then how big are the neumanns? And what else do you need on the ship besides neumanns? And what sort of weapons do you need/want, since you mention those?
All of these factors impact your ship and system design. Lacking details on those, I'm still quite confident that a mass beam system can be scaled to launch your ship up to some interstellar speed. At least as long as the masses and speeds involved are below what can be powered by intercepting a large fraction (or even all) the energy output of a star or generating the equivalent. That level of energy is a factor regardless of how you propel your ship btw. Assuming you aren't using a tech that extracts energy right from the vacuum or something, which isn't really considered to be possible anymore.
Anyway - references - For an easy starting point within OA itself, see here: https://www.orionsarm.com/eg-article/460c3685cd4c4
The EG article also has a reference at the end which provides a general RL overview of mass-beam propulsion physics and options. I'd recommend reading that as well.
After that, loop back to me (on the forum is fine and probably a better place for this depth of discussion) and we can talk about things in more detail, including answering any questions you have, details of how your proposed ship might operate, etc.

Indeed, I had forgotten the details of what mass beams are and treated them like laser beams. The footnote article was quite interesting, although I have not read all of it, but I think I get a better sense of how it works. Do you think it would be possible to use collimated solar wind instead of streams of micropellets?

But before we get to that point, I think we get into issues of what you want the ship to do, how you want it to do it, and how fast you want it to travel.

During flight, the ship needs to monitor the environment (although I don't think I need to get into details here), be able to make some level of course correction, resist to erosion, defend itself against hostiles. It can brake and accumulate energy by deploying a forward magsail towards the end. Ideally, it would run as fast as a Conversion drive or some drive of equivalent efficiency would permit. Ideally somewhere between 0.5 and 0.8c

Also, if you have neumann tech (which you kind of do need to make mass-beam travel practical on any large scale), then how big are the neumanns? And what else do you need on the ship besides neumanns? And what sort of weapons do you need/want, since you mention those?

I haven't figured how big the Neumanns are yet. I'm not sure I need to get into that kind of detail anyway. It's meant to be a philosophical story, so the technical side of things needs not be very developped, but I'd like to avoid if possible making up stuff that obviously wouldn't work for a reason I'd have missed. Also I try to not just recycle the ideas but attempt to introduce variants, like a cruder form of the tech that uses "natural" solar wind as mass stream particles.

A proposed idea is inspired from the Caplan thruster: a swarm of mirrors reflect some sunlight on a certain region of the sun, which then emits extra solar wind. This solar wind would then be collimated and beamed towards the ship's magsail.

Thoughts?

[stevebowers]

The 'collimated solar wind' idea may work for interplanetary transport, but for an interstellar boost system, it would be problematic. Solar wind particles are charged, so they could be collimated - but charged particles repel each other, so they would spread out and quickly lose focus. An interstellar acceleration pathway needs to be very long, so you need a beam that won't spread out.

The mass particles in an OA boostbeam are neutral, so they won't spread out. The most advanced versions use small but very smart particles that can 'home-in' on the spacecraft's sail, so they won't spread out at all, even by diffraction.

[The Architect]

Solar wind particles are charged, so they could be collimated - but charged particles repel each other, so they would spread out and quickly lose focus.

How far would they start significantly losing focus? I assume accelerations in the hundreds of Gs are not on the table.

Drashner
But before we get to that point, I think we get into issues of what you want the ship to do, how you want it to do it, and how fast you want it to travel. Also, if you have neumann tech (which you kind of do need to make mass-beam travel practical on any large scale), then how big are the neumanns? And what else do you need on the ship besides neumanns? And what sort of weapons do you need/want, since you mention those?

Alright, so I think I have a few more answers here. I've started reading the space warfare article and ever since then I'm reeling with all the possibilities in terms of story telling. This was one of the most transforming articles I've read so far.

So the ship is essentially a Von Neumann seed which has its own intellect. If the solar wind solution fails, I might want to replace it with a amat-fueled booster system to be discarded at 0.2 c once the magasail / conversion drive equivalent start functioning. After that I could have the system run anywhere between 0.5 and 0.8 c.

The ship must contain a number of mining units ready to work on any M-type asteroid. Basically, they will shoot a lesser asteroid, or somehow discharge enough energy into the center of a well-chosen 'pile of rubble' type of M-type asteroid (probably located near the Lagrange points of gas giants) to break it into its component parts. Then, during the few weeks that it takes for the asteroid parts to join back together, structures and thrusters are built on each of them so that when they get back together, they encase into each other with a huge construction facility at the center and mining units eating each part of the asteroid, until the time when there is nothing left but the junk. In the meantime, hundreds or thousands of other asteroids near the Lagrange point may have received a similar treatment.

I'd say it needs at least a hundred self-propelled mining units, plus some drones, of course a large array of sensors, many ways to collect energy (I assume a lot of antimatter could be generated during the magsail braking phase). I guess if the mining units can work very fast, they don't need to be very big. Hopefully all that fits into a handful of million tons.

As for weapons, I'd say lasers, X-ray for big / close targets and more conventional ones for longer distances. Weapons would be essentially defensive during interstellar flight.

[Drashner1]

Getting caught up on replies...

Indeed, I had forgotten the details of what mass beams are and treated them like laser beams. The footnote article was quite interesting, although I have not read all of it, but I think I get a better sense of how it works. Do you think it would be possible to use collimated solar wind instead of streams of micropellets?

Unfortunately, no. The particles making up the solar wind move at about 400km/s while even the slowest 'practical' interstellar velocity (1% of c) is 3000km/s. In order to accelerate a ship up to the sort of speeds you are contemplating a mass beam needs to be moving at least as fast as the ship (or the final velocity of the ship) and solar wind just doesn't do that.

You could use a very large magsail (or lightsail, or lightsail/magsail combo) to get your ship around a solar system or even start it traveling out of a solar system before other systems take over. But using the solar wind or passive light pressure alone to get up to any kind of 'practical' speed isn't doable. Although if you wanted to do something where the ship takes thousands of years to travel between stars with the protagonist coming out of stasis or activating (if a sophtware or AI) only when the ship is in a system or there's an emergency, that would be doable.

Also, the infrastructure needed to make a Caplan thruster type system work seems to me to be at least as large, and quite likely larger, than what would be needed for a mass-beam based system.

During flight, the ship needs to monitor the environment (although I don't think I need to get into details here), be able to make some level of course correction, resist to erosion, defend itself against hostiles. It can brake and accumulate energy by deploying a forward magsail towards the end. Ideally, it would run as fast as a Conversion drive or some drive of equivalent efficiency would permit. Ideally somewhere between 0.5 and 0.8c

Agreed, you probably don't need to worry about the details environmental monitoring on general principles, unless it plays a role in the story. Note that if the ship is potentially engaging in combat while in flight, being able to monitor the environment and detect incoming enemy ships/weapons could play a very important role in the story that could result in you needing/wanting to delve into this aspect of things more. But you know this project better than I so will defer to your judgement on this.

Course corrections in the realm of STL interstellar flight are doable, but take a long time. Given the already established use of magsails and such, your best bet might be to configure the magsail to interact unevenly with the galactic magnetic field to allow the ship to turn. Such turns will be very gradual (think years to decades to accomplish, depending on how much you want to turn), but in principle the ship could do a 180 given enough time. You can also in principle use this to generate electricity onboard. Like magsail based braking, this will also tend to slow the ship a bit, so this isn't something you can just use without limit. But its doable and the details may or may not be something you need to do a deep dive on.

Combat at interstellar speeds in a STL framework is not a topic that comes up a lot in SF. I/OA can offer some notions (and also contribute to the OA projects info on this since this sort of thing also applies to OA), but I'd also recommend seeing if Sevoris has some thoughts on it or can point you at relevant posts on the ToughSF blog. One of the biggest single factors may be the amount of kinetic energy wrapped up in the ships and how that can be used (or have to be defended against) in combat. Put another way - one of the most effective weapons in this kind of fight could be throwing a bag of gravel (or even just a bunch of glitter or a lightsail) overboard and slowing it enough so that your opponent then runs into it at high speed with an effect like a bunch of high explosives going off in their face.

Magsail braking can work very well, and works better the faster the ship is moving. I can point you at an article by Robert Zubrin about this. See HERE and the references at the end. Note that decel via this method starts out at multiple gravities and then drops off over a period of years (assuming high initial speed) and ceases to be effective once the ship slows down to about one half of one percent of the speed of light (1500km/s). After that you need some kind of other system to get down to 'interplanetary speeds' - rockets or some combo of rockets and other things probably.

In the OA setting, we presume that the Y11k versions of magbrakes can also operate as a ramscoop and collect/slow down/package and store interstellar material during the decel phase so that it can be used as reaction mass once the magbrake stops being effective. We don't have any hard numbers on this to share, but it seems doable. Using the energy generated during decel to make antimatter is a new (and fun) variant, but I'm not sure how much electricity you could actually extract or how much amat you might be able to make this way based on the energy available. That might be possible to calculate in terms of what the absolute physical limit is although the details could be left vague. And not sure you want to/need to get so much into the weeds to even calc the absolute limit for purposes of this story. Basically, it's an editorial choice on your part mostly.

In terms of the ship's velocity (.5-.8c) - Beamrider tech can do this in principle as long as you can keep the beam focused long enough. My preferred method is the 'smart dust' approach proposed by G. David Nordley in which a 'beacon laser' shines on the dust (which is actually a complex nanotech built construct) which in turn ejects parts of itself to push itself back into the focus of the beam. This system has limits (exactly how limited is open enough that you can partly make an editorial choice in this area), which generally mean the ship will want to accelerate hard at first and get up to cruise speed quickly while still close enough for the beams to work.

In terms of OA, for reaction drive ships with ramscoops, we describe using boostbeams to get the ship up to 'ramming speed' (the speed where the ramscoop works), then switching over to rocket drive using the scoop until the scoop is no longer effective (ramscoops have their own issues), then coasting until it is time to deploy the magbrake to slow down. This method has the option of only needing to get the ship up to ramming speed (generally ranging from 1% to 5% of c depending on who you ask) rather than all the way up to cruise speed. So your boostbeam energy and accelerator systems could be vastly smaller than those needed to get the ship all the way to .5-.8c.

In terms of drive specifics - Assuming you don't have conversion drive based on magnetic monopoles, you could use something involving antimatter (there are lots of designs). If you really want to push the limits of amat tech, I'd refer you to the q-mirror article HERE. Q-balls are a real think in RL theoretical physics and if you wanted to use a Q-mirror you could basically match OA monopole conversion capabilities or even exceed them in some respects depending on the details.

Ok - I think that about covers things for now.

Hope this helps,

Todd

[The Architect]

The particles making up the solar wind move at about 400km/s

That's a major bummer indeed
 
There is the obvious reason why it wouldn't work I was missing, on top of what's already been said


I'll come back for the rest later, and on the other thread too where I had an interesting idea

For now I'm thinking that if I go the route of a "disposable" amat-fueled engine for the acceleration up to 0.1c, the engine could then be used to drop small stealth monitoring systems on or a little way off the trail behind the starship. They could all decelerate with magsail breaking while powering up to stay alive as long as possible and then stay afloat around 0.01c towards volumes the Cathedral (Orwellian AI core) wants explored or monitored. They would self-destruct if anything tries to catch them or when they power is depleted.

[The Architect]

During flight, the ship needs to monitor the environment (although I don't think I need to get into details here), be able to make some level of course correction, resist to erosion, defend itself against hostiles. It can brake and accumulate energy by deploying a forward magsail towards the end. Ideally, it would run as fast as a Conversion drive or some drive of equivalent efficiency would permit. Ideally somewhere between 0.5 and 0.8c

Agreed, you probably don't need to worry about the details environmental monitoring on general principles, unless it plays a role in the story. Note that if the ship is potentially engaging in combat while in flight, being able to monitor the environment and detect incoming enemy ships/weapons could play a very important role in the story that could result in you needing/wanting to delve into this aspect of things more.

You're absolutely right about that. There is surely a page in the EG about that, I'll use it as a starting point in case it mentions sensors I don't know yet. I would imagine that at interstellar distances passive sensors would be the most important. I'll look this up in more detail

Course corrections in the realm of STL interstellar flight are doable, but take a long time. Given the already established use of magsails and such, your best bet might be to configure the magsail to interact unevenly with the galactic magnetic field to allow the ship to turn. Such turns will be very gradual (think years to decades to accomplish, depending on how much you want to turn), but in principle the ship could do a 180 given enough time. You can also in principle use this to generate electricity onboard. Like magsail based braking, this will also tend to slow the ship a bit, so this isn't something you can just use without limit. But its doable and the details may or may not be something you need to do a deep dive on.

As I understand it at the moment, only very minor course corrections can result in making the position of the starship impossible to figure out if it temporarily shuts down its drive and uses asymmetric magsail drag to change course by a random tiny fraction and then wait until the search volume becomes very big. Of course, the pursuers can also go stealthy and it becomes a game of cat and mouse, which could make for interesting peripeteia in the story. For example the starship could deploy decoys matching its drive signature to make the pursuers reveal their positions and drive them off until it's out of range of their detection and can start accelerating a little without being detected, and increase acceleration slowly as it falls away. Of course this would only work on a small number of pursuers. I would then have one pursuer with a very different signature manage to sneak up very close and send a miniature unit able to land on the starship, survive on the hull and dodge potential defences, get inside and remain dormant until later in the story when it is activated.

Combat at interstellar speeds in a STL framework is not a topic that comes up a lot in SF. I/OA can offer some notions (and also contribute to the OA projects info on this since this sort of thing also applies to OA), but I'd also recommend seeing if Sevoris has some thoughts on it or can point you at relevant posts on the ToughSF blog. One of the biggest single factors may be the amount of kinetic energy wrapped up in the ships and how that can be used (or have to be defended against) in combat. Put another way - one of the most effective weapons in this kind of fight could be throwing a bag of gravel (or even just a bunch of glitter or a lightsail) overboard and slowing it enough so that your opponent then runs into it at high speed with an effect like a bunch of high explosives going off in their face.

This is an interesting subject to delve in indeed. It is touched on in the Space Warfare, Modern EG article. I'll dig the matter some more. See if Isaac Arthur has anything interesting. I'm also digging the ToughSF blog, which has a lot of interesting articles.

Magsail braking can work very well, and works better the faster the ship is moving. I can point you at an article by Robert Zubrin about this. See HERE and the references at the end. Note that decel via this method starts out at multiple gravities and then drops off over a period of years (assuming high initial speed) and ceases to be effective once the ship slows down to about one half of one percent of the speed of light (1500km/s). After that you need some kind of other system to get down to 'interplanetary speeds' - rockets or some combo of rockets and other things probably.

In the OA setting, we presume that the Y11k versions of magbrakes can also operate as a ramscoop and collect/slow down/package and store interstellar material during the decel phase so that it can be used as reaction mass once the magbrake stops being effective. We don't have any hard numbers on this to share, but it seems doable. Using the energy generated during decel to make antimatter is a new (and fun) variant, but I'm not sure how much electricity you could actually extract or how much amat you might be able to make this way based on the energy available. That might be possible to calculate in terms of what the absolute physical limit is although the details could be left vague. And not sure you want to/need to get so much into the weeds to even calc the absolute limit for purposes of this story. Basically, it's an editorial choice on your part mostly.

I think I'll leave the details vague and just mention the drive can somehow convert interstellar dust into amat during the decel phase and then store it to use later as reaction mass to brake to interplanetary speeds.

In terms of the ship's velocity (.5-.8c) - Beamrider tech can do this in principle as long as you can keep the beam focused long enough. My preferred method is the 'smart dust' approach proposed by G. David Nordley in which a 'beacon laser' shines on the dust (which is actually a complex nanotech built construct) which in turn ejects parts of itself to push itself back into the focus of the beam. This system has limits (exactly how limited is open enough that you can partly make an editorial choice in this area), which generally mean the ship will want to accelerate hard at first and get up to cruise speed quickly while still close enough for the beams to work.

In terms of OA, for reaction drive ships with ramscoops, we describe using boostbeams to get the ship up to 'ramming speed' (the speed where the ramscoop works), then switching over to rocket drive using the scoop until the scoop is no longer effective (ramscoops have their own issues), then coasting until it is time to deploy the magbrake to slow down. This method has the option of only needing to get the ship up to ramming speed (generally ranging from 1% to 5% of c depending on who you ask) rather than all the way up to cruise speed. So your boostbeam energy and accelerator systems could be vastly smaller than those needed to get the ship all the way to .5-.8c.

I would like to avoid taking too much from OA, but at the same time I find the magsail to be a powerful symbol for its obvious analogy with old ship sails so I had started trying to come up with alternate designs using the magsail. So there would be 2 acceleration systems, the initial one and the one with a working ramscoop design (conversion drive equivalent, with amat probably).

I would then need to make a choice for the first acceleration system. I would like to avoid using OA's boostbeam and could look into Nordley's design if I want to have a sail used during that phase as well. The drawback is that it would make me have to either describe a complex system that has no bearing over the story or handwave it, which the readers may not appreciate either. I could alternately use something like an amat engine module that would detach itself at 0.1c when the magsail / CDrive-amat-equivalent starts functioning, and then fit another purpose (interstellar space surveillance). The advantage here I think is that the general concept of antimatter is simple enough to understand for the reader and if I reuse it in various forms, that will be one less thing the reader will have to learn about in order to understand the story, or put simply it will lower the conceptual load for the reader. I want to make sure I don't choke them with a conceptual fire hose.

In terms of drive specifics - Assuming you don't have conversion drive based on magnetic monopoles, you could use something involving antimatter (there are lots of designs). If you really want to push the limits of amat tech, I'd refer you to the q-mirror article HERE. Q-balls are a real think in RL theoretical physics and if you wanted to use a Q-mirror you could basically match OA monopole conversion capabilities or even exceed them in some respects depending on the details.

That's interesting, I'll have a look at that and see if there would be some payoff in making it matter in the story. If not, that will be useful for me to have a better sense of how things operate in this department

[The Architect]

relevant posts on the ToughSF blog. One of the biggest single factors may be the amount of kinetic energy wrapped up in the ships and how that can be used (or have to be defended against) in combat. Put another way - one of the most effective weapons in this kind of fight could be throwing a bag of gravel (or even just a bunch of glitter or a lightsail) overboard and slowing it enough so that your opponent then runs into it at high speed with an effect like a bunch of high explosives going off in their face.

Coming back to this, I think I've found the relevant article
http://toughsf.blogspot.com/2016/10/the-...ombat.html
One thing I notice here is that long range space combat is considered 10,000 km. This may be why there is very little about interstellar STL combat. I assume that at relativistic speeds you see and get seen a very long time before you can get anywhere near combat range. In this case, dodging techniques like using decoys would probably be deemed preferable. Combat would be the last resort when the starship is already failing at dodging and getting to that point may require a very large number of pursuers or sheer luck or a combination of both. Which is of course what is going to happen.
And then we would fall into that long range combat situation. The starship would have the superiority in weapons but the pursuers would have a superiority in numbers. The enemy would use some clarketech that allows them to split at will to multiply the targets and perhaps even recombine. And there would be a point where the starship is overwhelmed, at which point a new player shows up and basically saves the day. The new player would attempt communication, but the starship would just shoot it down according to standard procedure. Although not before it ejects a stealth microscopic module that will land in the starship's deceleration field (another clarketech that absorbs the kinetic energy of anything below a certain size (say a 100 microns?) that might hit the hull either straight at the front or at sideways angles relative to the direction of flight and is small enough to have escaped detection/deflection/destruction), manage to survive on or even inside the starship's hull and lay low.