I suspect my following questions demonstrate such high level of confusion, that I am not sure if they even mean what I think they mean, but still I think this is the best place to ask them:
My mental model of something very small hitting with very high energy something big is “Warner Bros cartoon”-like: one fast billard ball very quickly makes a hole in the big object by dislocating just one or a few more billard balls accelerating them all in the same direction without much effect to the integrity of the rest of the big object. I recall XKCD What If series explicitly addresing this mental model as flawed. Still, what if the big object is very flat, like a sail, and very loosely connected like a net? In general: is there any hope to make a spacecraft which simply doesn’t care about being hit, because (due to some “error codes” or “nanobots/regeneration”) can tolerate holes and holes are the only thing caused by impacts to it?
If there are particles which penetrate (almost) everything, why not make spacecraft from them? (Are neutrinos alien’s network?:))
If photons are so low mass, why not use something more massive to shoot the sail with?
Are there any “repulsive” / “potential energy” phenomena one could use to decelerate—I mean things like buouyancy, where (obviously in this example I am talking about very small velocities) a vehicle entering atmosphere could perhaps use a big balloon to covert kinetic energy to potential energy of buoyancy (with added benefit of being able to reuse some of this energy for going back home)? For another example, could a sufficiently advanced civilisation aim in between two stars so that the net force of their gravity pulled the spacecraft backwards till it (briefly) stops? I know this examples are silly, I just try to explain what would count as “this kind of solution”.
For 1, the mental model for non-relativistic but high speeds should be “a shallow crater is instantaneously vaporized out of the material going fast” and for relativistic speeds, it should be the same thing but with the vaporization directed in a deeper hole (energy doesn’t spread out as much, it keeps in a narrow cone) instead of in all directions. However, your idea of having a spacecraft as a big flat sheet and being able to tolerate having a bunch of holes being shot in it is promising. The main issue that I see is that this approach is incompatible with a lot of things that (as far as we know) can only be done with solid chunks of matter, like antimatter energy capture, or having sideways boosting-rockets, and once you start armoring the solid chunks in the floaty sail, you’re sort of back in the same situation. So it seems like an interesting approach and it’d be cool if it could work but I’m not quite sure it can (not entirely confident that it couldn’t, just that it would require a bunch of weird solutions to stuff like “how does your sheet of tissue boost sideways at 0.1% of lightspeed”.
For 2, the problem is that the particles which are highly penetrating are either unstable (muons, kaons, neutrons...) and will fall apart well before arrival (and that’s completely dodging the issue of making bulk matter out of them), or they are stable (neutrinos, dark matter), and don’t interact with anything, and since they don’t really interact with anything, this means they especially don’t interact with themselves (well, at least we know this for neutrinos), so they can’t hold together any structure, nor can they interact with matter at the destination. Making a craft out of neutrinos is ridiculously more difficult than making a craft out of room-temperature air. If they can go through a light-year of lead without issue, they aren’t exactly going to stick to each other. Heck, I think you’d actually have better luck trying to make a spaceship out of pure light.
For 3, it’s because in order to use ricocheting mass to power your starcraft, you need to already have some way of ramping the mass up to relativistic speeds so it can get to the rapidly retreating starcraft in the first place, and you need an awful lot of mass. Light already starts off at the most relativistic speed of all, and around a star you already have astronomical amounts of light available for free.
For 4, there sort of is, but mostly not. The gravity example has the problem of the speeding up of the craft when it has the two stars ahead of it perfectly counterbalancing the backwards deceleration when the two stars are behind it. For potentials like gravity or electrical fields or pretty much anything you’d want to use, there’s an inverse-square law for them, which means that they aren’t really relevant unless you’re fairly close to a star. The one instance I can think of where something like your approach is the case is the electric sail design in the final part. In interstellar space, it brakes against the thin soup of protons as usual, but nearby a star, the “wind” of particles streaming out from the star acts as a more effective brake and it can sail on that (going out), or use it for better deceleration (coming in). Think of it as a sail slowing a boat down when the air is stationary, and slowing down even better when the wind is blowing against you.
I was afraid my questions might get ridiculed or ignored, but instead I’ve got a very gentle and simply expressed explanations helping me get out of confusion. Thank you for taking your time for writing your answer so clearly :)
Usual neutrinos or dark matter won’t work, but if we go to the extremely speculative realm, there might be some “hidden sector” of matter that doesn’t normally interact with ordinary matter but allows complex structure. Producing it and doing anything with it would be very hard, but not necessarily impossible.
I suspect my following questions demonstrate such high level of confusion, that I am not sure if they even mean what I think they mean, but still I think this is the best place to ask them:
My mental model of something very small hitting with very high energy something big is “Warner Bros cartoon”-like: one fast billard ball very quickly makes a hole in the big object by dislocating just one or a few more billard balls accelerating them all in the same direction without much effect to the integrity of the rest of the big object. I recall XKCD What If series explicitly addresing this mental model as flawed. Still, what if the big object is very flat, like a sail, and very loosely connected like a net? In general: is there any hope to make a spacecraft which simply doesn’t care about being hit, because (due to some “error codes” or “nanobots/regeneration”) can tolerate holes and holes are the only thing caused by impacts to it?
If there are particles which penetrate (almost) everything, why not make spacecraft from them? (Are neutrinos alien’s network?:))
If photons are so low mass, why not use something more massive to shoot the sail with?
Are there any “repulsive” / “potential energy” phenomena one could use to decelerate—I mean things like buouyancy, where (obviously in this example I am talking about very small velocities) a vehicle entering atmosphere could perhaps use a big balloon to covert kinetic energy to potential energy of buoyancy (with added benefit of being able to reuse some of this energy for going back home)? For another example, could a sufficiently advanced civilisation aim in between two stars so that the net force of their gravity pulled the spacecraft backwards till it (briefly) stops? I know this examples are silly, I just try to explain what would count as “this kind of solution”.
For 1, the mental model for non-relativistic but high speeds should be “a shallow crater is instantaneously vaporized out of the material going fast” and for relativistic speeds, it should be the same thing but with the vaporization directed in a deeper hole (energy doesn’t spread out as much, it keeps in a narrow cone) instead of in all directions. However, your idea of having a spacecraft as a big flat sheet and being able to tolerate having a bunch of holes being shot in it is promising. The main issue that I see is that this approach is incompatible with a lot of things that (as far as we know) can only be done with solid chunks of matter, like antimatter energy capture, or having sideways boosting-rockets, and once you start armoring the solid chunks in the floaty sail, you’re sort of back in the same situation. So it seems like an interesting approach and it’d be cool if it could work but I’m not quite sure it can (not entirely confident that it couldn’t, just that it would require a bunch of weird solutions to stuff like “how does your sheet of tissue boost sideways at 0.1% of lightspeed”.
For 2, the problem is that the particles which are highly penetrating are either unstable (muons, kaons, neutrons...) and will fall apart well before arrival (and that’s completely dodging the issue of making bulk matter out of them), or they are stable (neutrinos, dark matter), and don’t interact with anything, and since they don’t really interact with anything, this means they especially don’t interact with themselves (well, at least we know this for neutrinos), so they can’t hold together any structure, nor can they interact with matter at the destination. Making a craft out of neutrinos is ridiculously more difficult than making a craft out of room-temperature air. If they can go through a light-year of lead without issue, they aren’t exactly going to stick to each other. Heck, I think you’d actually have better luck trying to make a spaceship out of pure light.
For 3, it’s because in order to use ricocheting mass to power your starcraft, you need to already have some way of ramping the mass up to relativistic speeds so it can get to the rapidly retreating starcraft in the first place, and you need an awful lot of mass. Light already starts off at the most relativistic speed of all, and around a star you already have astronomical amounts of light available for free.
For 4, there sort of is, but mostly not. The gravity example has the problem of the speeding up of the craft when it has the two stars ahead of it perfectly counterbalancing the backwards deceleration when the two stars are behind it. For potentials like gravity or electrical fields or pretty much anything you’d want to use, there’s an inverse-square law for them, which means that they aren’t really relevant unless you’re fairly close to a star. The one instance I can think of where something like your approach is the case is the electric sail design in the final part. In interstellar space, it brakes against the thin soup of protons as usual, but nearby a star, the “wind” of particles streaming out from the star acts as a more effective brake and it can sail on that (going out), or use it for better deceleration (coming in). Think of it as a sail slowing a boat down when the air is stationary, and slowing down even better when the wind is blowing against you.
I was afraid my questions might get ridiculed or ignored, but instead I’ve got a very gentle and simply expressed explanations helping me get out of confusion. Thank you for taking your time for writing your answer so clearly :)
Usual neutrinos or dark matter won’t work, but if we go to the extremely speculative realm, there might be some “hidden sector” of matter that doesn’t normally interact with ordinary matter but allows complex structure. Producing it and doing anything with it would be very hard, but not necessarily impossible.