?

tlb wrote:PS: the absolute worst thing I have seen occurs in Star Wars, where they show an anti-gravity oxcart. Either put wheels on it or use a faction of the energy that is levitating it, to get rid of the ox and move it forward.

I disagree--Star Wars repulsars seem to be basically zero-energy devices. Levitating doesn't actually do any work, thus there is no theoretical requirement for energy. While it's a major hand-wave look through the series, all ground effect repulsars work that way.

tlb wrote:It is ridiculous because the only motion that it imparts to the rest of the ship, is to be drawn into the black hole. So there has to be something that holds the ship out and that has to completely cancel the hole's force on the ship.

Therefore, where does the system get net motion? If an astronaut stands on an asteroid, the two of them do not start moving due to the force the asteroid is imposing on the person; there still has to be an unbalanced force to cause movement. You cannot justify that to me by saying Star Trek does it.

Loren Pechtel wrote:The pseudo black hole is vastly more massive than the ship, it's movement can be ignored.

Yes, but so what? The ship is not going to go anywhere, except into the black hole; unless something prevents it. For there to be useful motion, the center of mass of this ship & black hole system has to move; in the mechanism proposed by the book, the ship has to cause the black hole to move; which will drag the ship along behind it.

If there were a good way to make the black hole move, then why not apply it directly to the ship and eliminate the massive weight penalty of the now extraneous black hole???

ThinksMarkedly wrote:Actually, it is. A billion-tonne black hole would have a Schwarzschild radius of 1.5 femtometres, would last for 1.5 trillion years and would give off 356 MW of power in Hawking radiation. And a one-billion tonne black hole at 1 m of distance is no more gravitationally dangerous than a one-billion tonne asteroid at 1 m of distance -- for comparison, the Dimorphos moon that the DART impacted with has an estimated mass of 5 billion tonnes.

1) For a black hole of that size the Hawking radiation makes it dangerous.

2) The reason black holes are gravitationally dangerous is that they're small enough you can actually get in danger. Good luck getting 1m from a billion tons of anything not degenerate (remember, it's from the center and no digging allowed) and good luck containing a billion tons of degenerate matter in anything less than a Slaver stasis field.

tlb wrote:PS: the absolute worst thing I have seen occurs in Star Wars, where they show an anti-gravity oxcart. Either put wheels on it or use a faction of the energy that is levitating it, to get rid of the ox and move it forward.

Loren Pechtel wrote:I disagree--Star Wars repulsars seem to be basically zero-energy devices. Levitating doesn't actually do any work, thus there is no theoretical requirement for energy. While it's a major hand-wave look through the series, all ground effect repulsars work that way.

That is still the worst thing I have ever seen, and your explanation makes me hate it even more.

tlb wrote:I actually mentioned this as the only possible answer the last time I discussed this ridiculous method in this forum. I rejected it then and now, because the energy required to repeatedly create and destroy would be better spent by just moving the ship (and no you cannot regain all the energy needed to create a new one, when you destroy the previous one). This does even begin to discuss the oscillating tidal effects such a process would entail, that are most likely to destroy the ship after killing all life on it.

Loren Pechtel wrote:I don't think those drives are actually creating black holes. Rather, they are gravity projectors, creating a gravitational field of that density but with no mass inside. No energy is involved in the "destruction", you are simply turning off the projector. I actually find the Hammer missiles of the A Learning Experience books more realistic as there's no game of switching them on and off, it's simply a pseudo black hole in front of the missile. It still has the tide and tiny size problem, though.

If it has the tide, then it also has the effective mass of a black hole. A field is a thing and it contains energy that has to be put in when the field is created and will be released somehow when the field collapses.

If the projector is holding it in fixed relation to the ship, then there is no net movement.

Anyway, you need to get your story straight; because you previously said this:

Loren Pechtel wrote:The pseudo black hole is vastly more massive than the ship, it's movement can be ignored.

tlb wrote:A drone will not be as stealthy, if it includes a buckler; which has the same physical characteristics as a sidewall.

It won't be as stealthy but it shouldn't be all that different.

I do not think that you have completely thought through what happens with a hit by a counter missile. Yes, the fragments might initially have the momentum of your missile; but the destruction of that missile will also add outward momentum to the elements of that cloud, causing it to spread.

But when does that intercept happen? Let's consider a kamikaze coming in at .99c, lightspeed detection at 10 million km (the recon drone certainly wouldn't be spotted at that distance.) Oops, the kamikaze is really only 100,000 km out. I'll be generous and assume a countermissile perfectly aligned. The drone has only .33 seconds of flight left, thus the CM gets only that much time. I forget CM accelerations, I think they're in the ballpark of 1Mm/s. That takes it to 330km/s and if I'm remembering my physics right it impacts about 50km from the target.

Whatever the exact nature of a wedge-on-wedge kill that's going to be very energetic, I assume the kamikaze is vaporized in the process. It's not going to be meaningfully slowed, however--by Newtonian math it has only a millionth of the energy of the kamikaze (and that's assuming equal mass--given the size difference it's more like 10 million) and Einsteinian math only adds to the problem.

Note that the kamikaze only has 170 Newtonian microseconds of flight left--23 Einsteinian microseconds. How much is it going to disperse in that time?

Note that I have given the defender some very optimistic assumptions here and they still can't get it unless they can shoot with FTL data.

tlb wrote:Yes, but so what? The ship is not going to go anywhere, except into the black hole; unless something prevents it. For there to be useful motion, the center of mass of this ship & black hole system has to move; in the mechanism proposed by the book, the ship has to cause the black hole to move; which will drag the ship along behind it.

If there were a good way to make the black hole move, then why not apply it directly to the ship and eliminate the massive weight penalty of the now extraneous black hole???

The thing is the black hole isn't real, it doesn't need to be moved.

(Now, I suspect that if you can create gravity you could use it as a drive directly by simply projecting it forward, the only benefit of the black hole is messing with incoming weapons and in extremis, ramming. You still have the tide problem, though.)

tlb wrote:Yes, but so what? The ship is not going to go anywhere, except into the black hole; unless something prevents it. For there to be useful motion, the center of mass of this ship & black hole system has to move; in the mechanism proposed by the book, the ship has to cause the black hole to move; which will drag the ship along behind it.

If there were a good way to make the black hole move, then why not apply it directly to the ship and eliminate the massive weight penalty of the now extraneous black hole???

Loren Pechtel wrote:The thing is the black hole isn't real, it doesn't need to be moved.

(Now, I suspect that if you can create gravity you could use it as a drive directly by simply projecting it forward, the only benefit of the black hole is messing with incoming weapons and in extremis, ramming. You still have the tide problem, though.)

I will accept if you say that it is not a real black hole; but it does have a reality, it has all of the attributes of the black hole that it is counterfeiting. What means that it has all of the energy requirements to create it and keep it running.

The protection offered by an artificial black might be useful, but that is not a good enough reason to use it as your primary drive.

Just projecting to a fixed spot does not provide motion. It has to be projected and allowed to move in such a way that it and the ship fall toward each other (so there are equal and opposite forces acting on it and the ship). Then it has to collapse before the ship is destroyed and a new field projected further out and so on. The act of creating and collapsing the field cannot impose any additional forces on the ship (I am not convinced that requirement can be met, because the attraction spot has gained momentum - equal and opposite forces mean there is no net momentum change).

There is no special avenue in this method that would allow more than sub-light flight.

Loren Pechtel wrote:

cthia wrote:But that dependence might be a result of not being able to reach viable ramming speeds. And those speeds, the god of the HV has decreed, apparently begins at ~ .9C.

You don't need that sort of velocity to ram--you just need a way past the wedge. The logic behind the laserhead made sense in the SDM era, but the MDM changed things--it is almost as survivable ramming as it is at maximum standoff. Sure, it's a sitting duck for the point defenses, but the point defenses will be reloading during that last .2 seconds.

You still need standoff to get around wedges and you might need to use some standoff to avoid fratricide if too many missiles make it through (but I think this unlikely, if they are even tens of microseconds apart there will be no fratricide), but the desired attack should always be ram.

Well also a way through the sidewall. I don't know what, if any, velocity would let a missile pierce that. But we know that in HotQ a pair of 78-ton impacts at 0.25c on a BC's sidewall were harmless.

But I also thing you're overstating their resistance to point defense. Even if an MDM was traveling infinitely close to the speed of light it'd still take it 11.7 seconds to cover the 3.5 million km envelope of a Mk31 CM. Sure at that speed it'd take about 0.333s to cover the PDLC envelope. And yes, the current cycle rate on an point defense laser emitters is 16 seconds; but a Nike-class BC(L) carries 30*14=420 such emitters on each flank, allowing it to keeps up a steady 25 shots/second; meaning it could get off at least 7 shots at a MDM closing at lightspeed - so not all the emitters are going to be recharging during that 1/3rd of a second it takes for light to streak through the PDLC envelope. (And of course capital ships mount even more clusters)

But, more importantly to my mind, at even normal MDM terminal velocity the missile has no ability to turn a corners. And while there may be some velocity at which a missile can blow through a sidewall, there's no evidence the same would every be true of a wedge. So all the ship would need to do to be utterly invulnerable to missile ramming attacks; not matter how high velocity they were, was roll just far enough that the wedge is interposed between the missile and the hull.

At that point you're back to have to make a 'snap shot' with a laserhead because there's no ramming target left.


And trying to reach those speeds with a drone drive is going to be a long slow process; as even in flat out, non-stealthy, mode like we saw at Mobius they've got less than 1/2 the acceleration of the low accel setting of a missile. Try to keep the accel low enough that you can hide the acceleration from just distant grav sensors and it's a quarter of that (or about 11% of the missile's low accel). So for a semi-stealthy accel you're looking at an hour and 21 minutes, covering over half a billion km (~32 lightminutes) to get to just the 0.8c an MDM can hit in 9 minutes. And at that velocity the bow shock is going to be really noticeable when it flies by your distant FTL-comm equipped picket. So even with a stealthy drive it's not sneaking up on a first line target at that velocity. (And against a 2nd or 3rd rate opponent you don't need to do anything fancy, your laserheads will rip them apart anyway)

tlb wrote:

tlb wrote:It is ridiculous because the only motion that it imparts to the rest of the ship, is to be drawn into the black hole. So there has to be something that holds the ship out and that has to completely cancel the hole's force on the ship.

Therefore, where does the system get net motion? If an astronaut stands on an asteroid, the two of them do not start moving due to the force the asteroid is imposing on the person; there still has to be an unbalanced force to cause movement. You cannot justify that to me by saying Star Trek does it.

Loren Pechtel wrote:The pseudo black hole is vastly more massive than the ship, it's movement can be ignored.

Yes, but so what? The ship is not going to go anywhere, except into the black hole; unless something prevents it. For there to be useful motion, the center of mass of this ship & black hole system has to move; in the mechanism proposed by the book, the ship has to cause the black hole to move; which will drag the ship along behind it.

If there were a good way to make the black hole move, then why not apply it directly to the ship and eliminate the massive weight penalty of the now extraneous black hole???

The gravitational attraction between two neodymium magnets would be greater than the attraction of a magnet and an object.

Tlb, when you initially stated that the black hole was in the nose of the ship, all I could come up with is that a second black hole would be created at its Swarsczchild radius at the bow of the ship and the two enormous forces would take care of the rest.

At any rate, we must not overlook the possibility of the black hole warping spacetime and the ship taking advantage of the "shortcut." We are all aware of the explanation of folding space onto itself like a sheet of paper and ships taking the shortcut through the middle. That is why I do not have a problem with Star Trek's warp nacelles warping (bending) spacetime, thus, providing the same benefit of traveling FTL. This is also the wind beneath my wings upstream, tlb, when I stated that these two methods of propulsion are variations of the same theme. And logically sound in my book.

All of the objections seem to be centered around the problems with the "small fries" that come with the order, but if there is an entity who is intelligent enough to successfully prepare and serve the main course for consumption should have no problem fixing the side orders.

The gravitational attraction between two black holes is immense, and the process creates something called the Lense-Thirring effect. Frame dragging.

"... an interpretation of GR where gravitational forces are so strong that they “drag” the very fabric of spacetime with them."

This can be witnessed mathematically inside the Swarsczchild radius (SR) of a black hole. IMO.

Also, if two black holes are created at their SR from each other and are spinning, they might create a corrider between the two for a ship to be shot through like a whiplash.

Or, if a second BH is created ahead of the first their attraction would be even greater, pulling the tethered ship along with.