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?

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.

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

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

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?

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?

"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

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

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.

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?