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#1
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Black-hole powered thruster?
The scientist who recently announced that they may have created an
extremely short-lived black hole in the lab got me thinking; is the following a plausible design for a thruster system?: Black holes can have charge, so we should be able to suspend a sufficiently small black hole somehow, and hold it in place. Also, as black holes get smaller, their 'temperature' increases and they emit more radiation, right? It seems to me that if you fed matter to the black hole at the same rate it was emitting energy, and you could reflect all that energy out the back of a rocket engine, you'd have the ultimate matter-to-energy conversion device, right? You'd have to feed charged matter to the black hole, I guess, so it maintains charge, and perhaps the 'startup' would be expensive in energy/equipment, but would this work, in principle? A common problem with nuclear thrusters seems to be a requirement for large amounts of shielding; Wouldn't this avoid that need? As I understand it, black holes would give off blackbody radiation, which isn't 'hard', so shielding requirements would be lower. any feedback, or am I totally out there? |
#2
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Mike wrote:
The scientist who recently announced that they may have created an extremely short-lived black hole in the lab got me thinking; is the following a plausible design for a thruster system?: No. A small black hole evaporates too fast to be of use. As an example, if I recall correctly, a 600 ton mass black hole evaporates totally in 1 second. Another way of saying this is that to create a 600 ton black hole, you have to put in several orders of magnitude more energy than this, in 1 second. This is more energy in 1 second than humanity has used over its lifetime. Not Real Soon Now. The size of black hole you need to get to before it gets 'cool' enough to handle (let's say a lifetime of a year) is really quite large. |
#3
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Well, but if we are talking about psuedo-fake stuff anyway - hows this:
1. Make a 600 ton black hole in a reflecting cone. 2. Feed 600 ton/s of matter into the black hole through the tip of the cone. 3. The matter is converted into light/radiation, and is emitted through the cone. Isp: 30,000,000 Thrust: 18,000,000,000 tons See, a great engine design - only a few small engineering problems left - where do I sign up for funding? -David |
#4
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On 21 Mar 2005 23:16:13 GMT
Ian Stirling wrote: No. A small black hole evaporates too fast to be of use. As an example, if I recall correctly, a 600 ton mass black hole evaporates totally in 1 second. Another way of saying this is that to create a 600 ton black hole, you have to put in several orders of magnitude more energy than this, in 1 second. You can feed the mass/energy into the black hole in the form of mass, assuming that you can push it against the flow of mass/energy from the evaporating black hole. The advantage of feeding mass in is that it has a higher density and is easier to manipulate in large quantities. Once you have got it stable you can feed matter in slowly and use the resulting radiation as a power source. -- Michael Smith Network Applications www.netapps.com.au | +61 (0) 416 062 898 Web Hosting | Internet Services |
#5
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Antimatter is a better fuel for space craft.
"Mike" wrote in message oups.com... The scientist who recently announced that they may have created an extremely short-lived black hole in the lab got me thinking; is the following a plausible design for a thruster system?: Black holes can have charge, so we should be able to suspend a sufficiently small black hole somehow, and hold it in place. Also, as black holes get smaller, their 'temperature' increases and they emit more radiation, right? It seems to me that if you fed matter to the black hole at the same rate it was emitting energy, and you could reflect all that energy out the back of a rocket engine, you'd have the ultimate matter-to-energy conversion device, right? You'd have to feed charged matter to the black hole, I guess, so it maintains charge, and perhaps the 'startup' would be expensive in energy/equipment, but would this work, in principle? A common problem with nuclear thrusters seems to be a requirement for large amounts of shielding; Wouldn't this avoid that need? As I understand it, black holes would give off blackbody radiation, which isn't 'hard', so shielding requirements would be lower. any feedback, or am I totally out there? |
#6
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Michael Smith wrote:
On 21 Mar 2005 23:16:13 GMT Ian Stirling wrote: No. A small black hole evaporates too fast to be of use. As an example, if I recall correctly, a 600 ton mass black hole evaporates totally in 1 second. Another way of saying this is that to create a 600 ton black hole, you have to put in several orders of magnitude more energy than this, in 1 second. You can feed the mass/energy into the black hole in the form of mass, assuming that you can push it against the flow of mass/energy from the evaporating black hole. The advantage of feeding mass in is that it has a higher density and is easier to manipulate in large quantities. Once you have got it stable you can feed matter in slowly and use the resulting radiation as a power source. Oh yes, it's just a simple engineering problem. Once you can focus hundreds of tons per second of energy on a subatomic target. We're only, 20, or maybe 30 orders of magnitude away from this. Should be sometime next week. Wedensday? |
#7
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"Mike" :
The scientist who recently announced that they may have created an extremely short-lived black hole in the lab got me thinking; is the following a plausible design for a thruster system?: That is a hard claim to just take your word on, could I get an URL please. Earl Colby Pottinger -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
#8
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Well,if you really could make a black hole it would be far better than
antimatter. Antimatter allows energy storage, but does not provide an energy source and is difficult to contain. A black hole would take normal matter and convert it into intense blackbody radiation. So you could use any matter for fuel, and it would emit the "mass" at the speed of light. The logical continuation of this theory (or playing pretend, depending on your grasp on reality) - make a buzzard ramjet out of "black hole material." The scoop converts the incoming matter to energy, which is reflected in such a way as to provide propulsion. And if you are racing someone you dont like, you can "accidently" run them over! Sounds like a great plot device for a SF novel, eh? -David |
#9
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Wikipedia has some nice articles on black holes, and the math has been
mostly worked out for you. I wasn't able to figure out my basic question, though, which is why having, say, iron converted 100% into hard gamma rays doesn't decrease entropy. Anyway, you've got this black hole electromagnetically suspended in a stupendously violent plasma flow. Throttle control is really bad: The hole weighs enough that actually dumping mass in to balance the radiative mass loss is irrelevant in the short term. So at least you don't have to worry about the earlier poster's point on pushing mass into the hole against the radiation pressure, or at least, not during rocket operation. Long term, adding mass will be necessary to keep the radiation power from the thing increasing! Positioning seems hard: you are trying to hold this thing in position with electromagnetic charge, in the middle of a plasma storm. Lest it appear I know what I'm talking about, I have no idea how the force of the electric field is conveyed to the black hole, when photons, which I thought were responsible for conveying that force, cannot escape the hole to perform the equal and opposite reaction on the stuff around it. Power is: P = h*c^6/(15360*pi*G^2*M^2) Mass flow is: P/c^2 = h*c^4/(15360*pi*G^2*M^2) So a balanced 1 kg/s mass flow into the black hole would require a 1.58e8 kg black hole. If 1e2 kg/s mass is uniformly heated and ejected through a perfect nozzle by the resulting radiation, velocity would be v^2 = 2*P/m v = 4.2e7 m/s Thrust is 4.2e9 N. Note that the rocket is doing this the whole time you are fabricating it, attaching the payload, etc. Thrust-to-mass is 26 m/s/s. This thing could take off from the ground, if the intense gamma radiation from the exhaust wasn't, you know, a big deal. You probably need orders of magnitude more mass flow for film cooling, which is going to increase the amount of thrust by orders of magnitude. To get that down, you'll need a larger black hole, but the mass sensitivity is good enough that it looks like black holes the mass of a few Saturn Vs will do the trick. The gamma rays will be pretty hard. Temp = h* c^3/(8*pi*k*G*M) which would be 4.87e15 Kelvins, at which the radiation peak will be at 5.9e-19 meters. The whole thing seems implausible, but I am very curious about the concept of film cooling something that hot. I would imagine the gammas don't get very far through the plasma. I wonder if the plasma itself can support a significant temperature delta, and I wonder what kind of material flow rate would be required to balance the rate at which hot gas at the edge of the plasma turns to plasma from the radiation. I also suspect this temperature may be high enough to dissociate nuclei, which would tend to make the exhaust radioactive even after it had cooled off. |
#10
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David Sounds like a great plot device for a SF novel, eh?
Especially if you suppose that making a megaton black hole is impossible, so that such things must be found. On a cosmological scale, they flash out of existence shortly after they get small enough to become usable. I would expect that newly usable small black holes would be incredibly rare, immensely valuable, and detectable across fairly large distances. And that brings lots of folks to the scene, all trying to grab the loot. And it's winner-takes-all: getting there is probably a pretty marginal prospect, interstellar travel being so inconvenient and so on, so anyone who doesn't get the hole isn't going back home empty handed, but just not going home at all. With just mass, spin, and charge, it doesn't seem like there are a lot of different ways to poison the well, either, assuming you already have one of these holes and don't want anyone else to have one. Is there any way to reduce the mass of a stellar-mass-sized black hole... in a hurry? |
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