Black hole starship engines : Whoa

[Minecrafter1]

Who ever said the particle beam has to be at the speed of light? It only has to resist the photon pressure coming off the black hole for an instant, and to be sucked in by the event horizon itself when it hits it.

The numbers you are talking about would make the black hole pointless, because you are investing as much energy flinging stuff into it as it releases.

The paper mentions that creating an acretion disk around the black hole might be needed : then you just have to send your particles to be caught by the accretion disk. Come to think of it, you would not want the particles traveling at the speed of light or anywhere remotely close to it. You'd send them at the accretion disk at a low enough velocity that they would be slowed down by photon pressure and enter orbit around the black hole. That probably takes a very low velocity for your particle beam.

Edited December 20, 2013 by Minecrafter1

[Minecrafter1]

Re-read parts of the paper, thinking about actual mission designs.

Apparently, smaller and more energetic black holes give you a lot more acceleration. So, that brings to mind a modified engine proposal : for an interstellar mission, you use 2 black holes in your engine. If the mission is going to take 100 years (ship-time), you use a small and energetic one with a short lifespan to get you up to speed. You feed it as you fly to keep the power output constant. You have a longer-lived, less energetic black hole orbiting around it in the engine chamber.

Now, you deorbit the short-lived black hole so that it falls into the long lived one. I wonder if this will work... If it does, and they combine into one really long lived black hole, it works great. You have the masses figured out so that the black hole will lose mass over the next 100 years as you fly, providing the ship energy and thrust to sustain interstellar "cruising" speed. (and you gather interstellar matter as you fly using a ramscoop to reduce the amount of mass of the ship you lose)

As you get near the destination, you turn the engine around, and, as it loses mass, the engine naturally "throttles up" and it slows you down into the target system.

Once you arrive in system, you find an asteroid to eat and "quench" your engine, filling it full of mass to give it a much lower output, enough to power your new civilization but not waste excessive amounts of mass.

This reduces energy lost pointlessly accelerating you to high relativistic velocities : any civilization capable of this kind of technology would have immortal crewmembers who could sleep or otherwise go dormant for long journeys, so there's no reason to go faster than 0.9c or 0.5c or so.

Thinking about it further, I realize that just making the ship far more massive, such that you can quench the SBH with matter stored aboard the ship once you reach interstellar cruising speeds makes far more sense. (since that extra mass will also make your engine more efficient since it absorbs more of the gamma rays)

You could reach anywhere in our galaxy with this technology, although, you probably would want to make a refueling stop every few hundred years at some random star. Assuming any star has at least some mass around it (hard to think of a reason one wouldn't), and since your ship can basically eat any old matter to use as fuel, you're good to go. I wonder if you could skim above a star itself to gather gas, with this kind of engine performance, maybe so.

For an intergalactic journey : dunno. Only idea that comes to mind is you'd launch a ship, with incredible mass, and "multi-core" engine using many small and energetic SBHs. Get up to a high fraction of C, and combine them all into one big black hole with the 20,000+ year lifetime needed to cross that distance of space (even with relativity helping you out, it's a darn long time). Reading off the chart, it looks like it would take combining about 20 of them.

If physics won't let you combine them, then you had to have been carrying a long life SBH the entire time, and you eject the short lived ones before they explode.

20,000 years later, you use the energy from your remaining SBH to build several new ones (this is a really, really massive ship and can carry all that gear) and you use those as engines to slow you down.

To be frank, it only sounds slightly more difficult than doing an interstellar journey to a nearby star. Sure, your equipment has to work for a long time, but you would have many parallel systems, and every single sub-component would have integrated self-diagnostics. When something fails, robots remove the failed part, put it into an on-board factory, and manufacture a brand new part from information stored on the ship. Unlike DNA, as long as you use MD5 and data recovery information, your blueprints will never be corrupted, even over 30,000+ years. So your ship will always know how to make new parts used in itself, and as long as it has matter and at least 1 remaining factory that can make any part, it can eventually repair any damage.

Edited December 20, 2013 by Minecrafter1

[AngelLestat]

First, I never said nothing about the velocity requeriments, on the contrary, is the thing that I am asking.

And the existence of an acretion disk meanwhile you had 130 petawatts of energy radiating from the black hole is hard to imagine. At least for me.

[maccollo]

I gotta say, and this for some reason didn't strike me initially, is that this is probably one of the coolest ideas for a spaceship propulsion I've heard.

I mean black holes are sort of perceived in popular culture as the ultimate monsters of the universe. Just the idea of us being able to tame the power contained in them and using them for our benefit is sort mind boggling.

[Minecrafter1]

Well, I'm no physicist, but that 140 petawatts is mostly gamma rays. As I understand it, at that wavelength they will tend to pass through matter - this is why you need so much mass to shield against them. Radiowaves get stopped with a thin grid of metal, infrared requires a thicker solid barrier, visible light requires a more solid material than infrared, UV requires an even stronger and heavier barrier, and so on. In "laymans" knowledge it seems obvious that gamma rays will buzz right on through most matter, including a thin acretion disk that is just a few thousand kilograms of matter yet to be eaten by the SBH.

I agree there are too many uncertainties as to what will happen. No one ever knows how big a particle an SBH this size can even eat.

Which reminds me : a future civilization, if it were possible, might choose to deliberately make a big enough SBH to actually quench our star. Think about how much energy our star wastes every day - more than we could ever use. If we converted it to a giant black hole, it would radiate a lot less energy and would live far longer. Also, it would be a lot more efficient since it would eventually convert 100% of it's mass to gamma rays. (versus stellar fusion which will convert everything to iron and then stop)

[Minecrafter1]

I gotta say, and this for some reason didn't strike me initially, is that this is probably one of the coolest ideas for a spaceship propulsion I've heard.

I mean black holes are sort of perceived in popular culture as the ultimate monsters of the universe. Just the idea of us being able to tame the power contained in them and using them for our benefit is sort mind boggling.

Agree. Rereading the paper, it noted a very nasty problem with antimatter containment. The same forces that would keep your antimatter contained in your ship (you might store it all as frozen anti-hydrogen or as pellets of anti-iron or something) will tend to force normal matter that leaks in to your containment system towards the center. In turn, if you collided with interstellar dust, it would punch into your antimatter confinement tanks and release enough energy to destroy them (and your ship, possibly)

The other problem with antimatter is that even if you solve this problem, it is not an energy source. Your starship would gradually burn through it's antimatter fuel load and be out. If you get to another star system safely, before you can leave you would have to build a gigantic facility, much larger than your ship, to collect sunlight and convert the energy to antimatter. The conversion process may also be horrendously inefficient (like 0.00001%), although, I have read of reasonably efficient proposals.

Versus an SBH ship, where you just have to grab a few hundred thousand tons of fresh matter from somewhere and you're ready to go. I guess if your black hole is a "picky eater", you might need straight hydrogen, but if it can eat heavier elements, then anything will work. (no one knows how big a particle a small SBH can consume)

You can also refuel as you fly, apparently, there's about 1 kg of interstellar hydrogen for every "earth sized volume" of space you fly through according to wikipedia. Not quite sure how that equates to your SBH's fuel consumption, whether or not you would gain fuel or not.

[Aladran]

I liked the SETI part

A SBH capable of driving a starship produces Hawking radiation which ultimately

gives rise to gamma rays, neutrinos, antineutrinos, electrons, positrons,

protons, and antiprotons [5]. Gamma ray telescopes are already in use and

thereby one might think that a careful search through the gamma ray sky could

conceivably turn up evidence of an extraterrestrial starship (cf. [18]). However,

gamma rays produced by a SBH in a distant starship might be extremely difficult

to detect if the

We now have other clues of what to search for

[ZetaX]

This seems to contradict the Bolzano theorem

It doesn't. If you think it does, you will have to give more reasoning.

[AngelLestat]

Of course this idea is great, is the ultimate machine! You drop any trash into and you get e=mc2, also in the paper if I remember well, there is a plan how to make other kinds of black holes to produce more black holes after those. But this idea has so many issues that for now remains label like a "curious proposal".

One year ago I was asking some stuffs about the Avatar Ship to Adam Crowl, he was very kind to answer, then this Crane idea come out into the discussion. This is what he answer me:

You might have noticed that I made some helpful comments on that preprint that get acknowledged. So I do have a few thoughts on using black-holes – however it will be immensely more difficult than matter-antimatter, something that I disagree with Louis Crane on. Concentrating a million tons of energy into a near infinitesimal point is an immensely challenging task. Directing the decay products into useful thrust will be another immensely challenging task. And force-feeding such a tiny hole will be incredibly hard. Three “miracles†of physics will be required. If Louis is right with his Meduso-Anthropic Principle, then it must be possible.

Somebody mention a gamma ray laser, like many of you know, gamma rays are really hard to manage it. So you cant have mirrors (for now), maybe some kind of rusty lens made of gold. That picture one of the problems that Adam is comment, try to focus all that energy in infinitesimal point is something that is out of our dreams.

I agree there are too many uncertainties as to what will happen. No one ever knows how big a particle an SBH this size can even eat.

And I think we have yet to hear what quantum mechanics has to say about this, after all is within its frame of reference and was totally ignored.

The other problem with antimatter is that even if you solve this problem, it is not an energy source. Your starship would gradually burn through it's antimatter fuel load and be out. If you get to another star system safely, before you can leave you would have to build a gigantic facility, much larger than your ship, to collect sunlight and convert the energy to antimatter. The conversion process may also be horrendously inefficient (like 0.00001%), although, I have read of reasonably efficient proposals.

The 2 main problems of the antimatter is how you get it, and how you storage, every else is "manageable".

It doesn't. If you think it does, you will have to give more reasoning.

If you had any continuous function that goes from 5 to 20, then you can predict that it has to pass in one moment for 8.

When you said that when you create a black hole goes directly to the size that you mention without pass their intermediate states violates that theorem, or best to said, the common sense

Of course if you inject a lot of energy very quick when you create it, then you will not find "many" problems with its initial state. But the event horizon start to exist from its first moments.

[ZetaX]

If you had any continuous function that goes from 5 to 20, then you can predict that it has to pass in one moment for 8.

When you said that when you create a black hole goes directly to the size that you mention without pass their intermediate states violates that theorem, or best to said, the common sense

Of course if you inject a lot of energy very quick when you create it, then you will not find "many" problems with its initial state. But the event horizon start to exist from its first moments.

This still makes no sense and is no consistent argument at all. Something is either a black hole or not. You can't be 70% BH and 30% non-BH. This has absolutely nothing to do with quickness (unless you wait some days/months/millenia for that hydrogen cloud to contract to a star or more likely a smaller BH by shrinking its volume; both are not what this is about).

The Schwarzschild radius is a function of mass, and it is indeed continuous, but being a BH means that to have all that mass inside it. It's the same for a supernova, the BH formed by them is also not just microscopic and then grows, but is large to begin with.

[jfull]

Honestly, I feel like this will eventually be created by some civilization some day.

This really shows how singularities aren't the all-consuming holes in space that they are usually depicted as.

[AngelLestat]

So.. you are saying that the event horizon appears only "after" the whole imploding process is finish? Please, think in those words a min before answer.

[Minecrafter1]

Well, suppose you have an incredible amount of matter set up to come at your black hole. It occurs to me that you could set up a stream of collimated particles into orbit around some body . You would set up thousands of these streams, all orbiting in some complex matter, with course correction stations out in space in various places to maintain the loops.

All told, you could have thousands of tons of matter out there in the form of high speed particles. There would be a convergence point where all the orbits intersected. You'd set the gamma ray lasers up there.

You turn on the lasers, and for an instant, an event horizon exists. It would be such a tiny black hole that it would be radiating energy away just as fast as it was gaining it.

But you time it so all these particle beams also enter the event horizon at the same instant. In theory, maybe the black hole could gain enough tons of mass that it doesn't emit energy faster than you can charge it up.

[Minecrafter1]

Thing about it, I'm not sure how to set up the orbital mechanics to create that collision. The concept is simple : somehow store up a gigantic amount of energy in the form of particle beams that will all intersect on your nascent event horizon at the same time. I mean, at that instant, the black hole is so small that it is at the very bottom of the chart in the linked paper, and is emitting many thousands of petawatts of energy. You need to cram enough mass into it in a fraction of a second to get the mass to the point it can be dealt with.

Tricky business, but once you do it, you have an engine you can use for years.

[ZetaX]

So.. you are saying that the event horizon appears only "after" the whole imploding process is finish? Please, think in those words a min before answer.

Please you think a min before answering: is there a tiny event horizon within you¿ If yes, you have gotten a lot of things wrong. If no, then where does one come form if you are pressed into a sufficiently small volume, if not by "simply appearing"¿

Things get a bit more complocated if seen relativistically, so lets just use something at your/the hydrogen sphere's surface as an observer, just to avoid nitpicking; or just think semi-classically on those matters.

[andrewas]

So.. you are saying that the event horizon appears only "after" the whole imploding process is finish? Please, think in those words a min before answer.

The event horizon appears when the density in a given region of space is sufficiently high. The smaller the space, the higher the critical density. So you don't get a small black hole that grows to the needed size, you get a region of increasing density that is suddenly a black hole.

[K^2]

The event horizon appears when the density in a given region of space is sufficiently high. The smaller the space, the higher the critical density. So you don't get a small black hole that grows to the needed size, you get a region of increasing density that is suddenly a black hole.

Sort of. GR is non-linear, so your very first sentence is not strictly true. It all very much depends on the matter arrangement.

But if we are talking about a sphere of matter whose density you start increasing, yes, it will happen exactly as you say. Event horizon will form once the radius of the sphere is less than Scwarzschild radius for the mass of that sphere. Note that density does not need to be uniform. It only has to be spherically symmetrical.

There is, however, a catch. Matter will typically begin collapsing long before that, which will form a shock wave. In a star, that shock wave becomes a super nova event. But even with a smaller object, it will shed some of its mass before forming a black hole. I don't know if there is a size limit there. Perhaps, for a small enough black hole, all of the mass would collapse inward. But like I said, we've only properly studied two ways a black hole can form, which is core collapse, or hadron collisions. There is no known way to achieve required densities by any other mechanism.

What velocity your matter needs to reach to enter in this SBH?

Just enough to push past the radiation pressure. I can do an estimate, for a proton beam, if you like. A neutron beam would require much lower velocity, because it has lower EM cross-section, but it's harder to organize as well. I think a proton beam is going to be more efficient despite the cross-section. It won't be anywhere close to mc², though, at any rate.

[Minecrafter1]

Oh. I didn't read the paper right. Totally dead wrong.

This is even more AWESOME than I realized earlier.

The paper says "1*10^9 tons of "nuclear lasers", and 1*10^-3 times the mass of the lasers become gamma rays.

I did the math real quick, and right off the bat the newly formed SBH has a mass of 1 million tons. That means it would be only radiating 56 petawatts or so, and would last for the next 16 years or more if you didn't feed it.

Now, uh, nuclear lasers....I'm not certain, but it kind of sounds like he meant 10^9 tons of atomic bombs and their lasing media.

So basically it's a gigantic bomb that produces a black hole in one titantic explosion, apparently. It all goes up in an amazing flash and at the middle you find a new SBH.

Not sure what the solar panels are for...

[Dispatcher]

The lasing mass is significant. The solar panels are to collect the energy needed for the initial gamma ray laser pulse. In my correspondence with one of the authors a few years ago, it was obvious to me that he is aware of the technology challenges associated with such a project. Either way, black holes or antimatter; it might take many generations before we have the capacity to move forward in any practical terms.

[nhnifong]

I find the "meduso-anthropic" principle mentioned at the end to be the most interesting part. If universes exist inside the black holes of other universes, perhaps there is some relation between the properties of the black hole and the universe within. Our universe appears to be expanding, but not staying constant. Perhaps it is a natural black hole that is eating matter steadily and not an artificial one being held constant for the purpose of energy production.

[AngelLestat]

Thing about it, I'm not sure how to set up the orbital mechanics to create that collision. The concept is simple : somehow store up a gigantic amount of energy in the form of particle beams that will all intersect on your nascent event horizon at the same time. I mean, at that instant, the black hole is so small that it is at the very bottom of the chart in the linked paper, and is emitting many thousands of petawatts of energy. You need to cram enough mass into it in a fraction of a second to get the mass to the point it can be dealt with..

Very tricky.

Please you think a min before answering: is there a tiny event horizon within you¿ If yes, you have gotten a lot of things wrong. If no, then where does one come form if you are pressed into a sufficiently small volume, if not by "simply appearing"¿

Things get a bit more complocated if seen relativistically, so lets just use something at your/the hydrogen sphere's surface as an observer, just to avoid nitpicking; or just think semi-classically on those matters.

The event horizon appears when the density in a given region of space is sufficiently high. The smaller the space, the higher the critical density. So you don't get a small black hole that grows to the needed size, you get a region of increasing density that is suddenly a black hole.

I am not sure what ZetaX was trying to said, but I guess both think similar.

Suddenly.. that is good term to explain ordinary daily events, but not so good for physsics.

Is like to said we have a big bang and suddenly we have the universe like we know it.

How much time this "suddenly" takes? Lets try to clarify this with some examples.

Lets imagine a massive star with 100 times the mass of our sun.

in some moment the fussion reacion pressure and its iron core collapse against gravity, so the molecules that are more close to the center starts to squeeze until a new kind of matter with only neutrons is form (I am avoding all details of this process of course), after that even the new neutron structure can not stand the pressure and in the center a subatomic black hole arises from planck scale growing until its corresponding radius depending on the amount of matter that su.ck into.

Of course the whole process maybe takes seconds or less. But let me remind you that in one second there is an infinite number of moments that can not be ignored.

However in your stand, you guess that a black hole with radius that is aproximate to the star mass appears from nothing?

Or maybe a smaller black hole with a particular size appears and then start to grow? What is that particular size?

If there was a particular size like that it would appear in some of the many equations already studied.

Is clear enought this time?

Sort of. GR is non-linear, so your very first sentence is not strictly true. It all very much depends on the matter arrangement.

But if we are talking about a sphere of matter whose density you start increasing, yes, it will happen exactly as you say. Event horizon will form once the radius of the sphere is less than Scwarzschild radius for the mass of that sphere. Note that density does not need to be uniform. It only has to be spherically symmetrical.

There is, however, a catch. Matter will typically begin collapsing long before that, which will form a shock wave. In a star, that shock wave becomes a super nova event. But even with a smaller object, it will shed some of its mass before forming a black hole. I don't know if there is a size limit there. Perhaps, for a small enough black hole, all of the mass would collapse inward. But like I said, we've only properly studied two ways a black hole can form, which is core collapse, or hadron collisions. There is no known way to achieve required densities by any other mechanism.

This a good way of disagree without loosing votes , you should consider a career in politics like science adviser.

Just enough to push past the radiation pressure. I can do an estimate, for a proton beam, if you like. A neutron beam would require much lower velocity, because it has lower EM cross-section, but it's harder to organize as well. I think a proton beam is going to be more efficient despite the cross-section. It won't be anywhere close to mc², though, at any rate.

You make it sound so easier.. You stop to picture the practical scene?

Well I will take your word that you spend less energy in the feed that you gain from the matter that you are introduccing.

Edited December 21, 2013 by AngelLestat

[PTNLemay]

Not to hijack the thread, but I remember seeing charts and calculators about this sort of stuff, and they seem very much in contradiction to one another. This chart from Atomic Rockets (see bellow) shows that a singularity in the vicinity of what Minecraftet1 is talking about (~140 PW) will last somewhere between 3.5 to 5 years.

But this online calculator gives me very different values. http://xaonon.dyndns.org/hawking/ If you input a mass of 0.673 megatons, it gives you a lifespan of 2.562688e+10 seconds. Now am I just futzing the math, or does that not represent over 800 years?

25 626 880 000 seconds,

31 556 900 seconds in a year

Divide the two and you get... 812 years. So which one is correct?

EDIT:

I also checked with mass to luminosity (which I take to mean energetic output). At 404 kilotons the chart says it will give off 367 petawatts. But using the same mass, the calculator gives me 2.18 petawatts. That's a difference of 2 orders of magnitude. I must be missing something... maybe the two are presenting different kinds of black holes.

Edited December 21, 2013 by PTNLemay

[Minecrafter1]

Paper uses a different method for calculating the lifespans. We'll never know for sure until we do experiments.

It would actually be a good thing if lifespans were long, because then it would be much easier to make an SBH.

[ZetaX]

AngelLestat: There can't be a microscopic black hole inside a neutron star because nothing in there is dense enough (the density of a microscopic BH is extreme even compared to a neutron star; at least if calculated classically/relativistically). What is dense enough is the star as a whole, and maybe a slightly slower volume, but still a very makroscopic one (some kilometers in diamater, probably).

I am repeating myself, and you ignored it the last two times already: A black hole is some (spherical) volume with enough mass inside it to form an event horizon. For a given radius, there is either enough mass inside it or not, and the required density inside the volume is lower the larger the radius gets. Therefore, some smaller part around the center may not have enough mass to be a BH by itself, but the larger volume of the exact same density can.

(Fun fact: by most estimates the whole universe is one, still you and I are not).

[AngelLestat]

Ok you are right. Of course it can be a horizon even without a singularity. I made a mess with the vocabulary.

And how I can not deal with this problem from the singularity point of view, becouse once a horizon event is form our theories break.

About the neuntron matter example, I start with a 100 solar masses star, in this case, the material is transformed into pure neutron and after that it will compress to form a singularity.

Is more, I was totally agree with K2 definition, but I dint see it from that point of view.

The universe like some others is a good example.