Koban 6: Conflict and Empire (44 page)

“We have excellent focusing close to the projectors, and very precise control over where the center of that focal point is generated. We can shift that focal point with considerable exactness and speed, to move it along a straight line between the projectors, and even outside of the ship, although with less exact precision as the distance away increases to hundreds of miles. The straight line we would use inside a Scout is the centerline of the evacuated launch tube we plan to install along the long axis of the ship, mounted near the ceiling, just as long as the spacecraft. A half-meter long dense metal projectile will be accelerated along that tube, in vacuum, by the gravitational attraction of our focused point of gravity. There is no propulsion force pushing it, just gravitational attraction.”

He directed Mirikami’s attention to a gleaming silvery rod sitting on a table, sharply tapered at both ends, perhaps a half meter long and no thicker than his thumb, with what appeared to be a thin glass coating.

“That is one of our projectiles. Neither the gravitational focal point, nor that rod, must make contact with the tube during launch. Until the rod leaves the tube it is magnetically levitated to avoid contact, and the magnetic field we use is shielded from external detection because the tube doesn’t extend beyond the stealth effect of the ship’s hull.

“The rod is accelerated from the center part of the tube in either direction, exiting at the ship’s front or rear, depending on the command given to the Scout’s AI. You’ll use the AI’s navigation steering control to aim the Scout towards, or away from a target, but gravitational steering and acceleration continues after launch, by continuously shifting the gravity field focal point in front of the rod. Initially, there will only be four projectiles held in a replaceable, pre-evacuated magazine, which can slide reload projectiles into the center part of the tube. If this system proves as effective as we hope, then larger magazines can be produced, and multiple launchers can be installed on our larger ships.”

Mirikami was surprised at how the two scientists, both from non-aggressive species, had voluntarily considered the details of making a new weapon. Clearly, humans were having a bad influence on previously pacifist races. Except, his gut told him that such a low energy propulsion system couldn’t make it as effective a projectile weapon as a rail gun, or as the sliver gun sniper rifle, both of which used magnetic acceleration coils. Nevertheless, he respected their desire to contribute to the defense of the Federation.

Blue wasn’t finished yet. “For a quicker magazine change, the launch tube has two vacuum seals, near the center of the tube, to allow a new magazine to be inserted. Any air that leaks into the tube must be removed, which is vital, and those molecules are flushed out by several fast cleaning runs, using a weaker gravity field, clearing both ends of the launcher before you can fire the next projectile. Does that make sense to you, Tet?”

After his previous error in judgment concerning his two friend’s research, Mirikami answered carefully, using more tact this time.

He began with compliments. “You’ve done a remarkable job of studying the requirements for this weapon, and outside of the complex gravity projectors required, which already exist, it’s an incredibly simple concept, with the only moving physical part being the projectile, which due to levitation, never touches anything, so it’s as frictionless as a rail gun projectile. The shifting focal point for the gravity field isn’t anything material, so there’s no heating or wear and tear on the launch tube, which I’ll admit is superior to a rail gun that suffers from overheating.”

Now, he eased gently into his critique. “To be effective against an enemy ship or orbital platform, a projectile weapon like the PU’s railgun platform sends hundreds of massive slugs at orbital velocities, and spreads them out to overwhelm a target’s ability to avoid them, or to use their lasers to vaporize them. The sliver gun, the spec ops premiere sniper rifle, isn’t fast firing, and uses a one and a half gram, tungsten carbide and cobalt covered sliver of metal, fired at a velocity of around ten miles per second.”

He summarized their advantages and shortcomings. “The PU’s rail guns send two pound slugs of dense depleted uranium, in large enough numbers to do significant physical damage, but they can be detected and avoided, or hit by defensive lasers, and they kick back the gun platforms. The sliver gun fires an ultrafast tiny projectile with great accuracy, and the far higher velocity makes it impossible to intercept or avoid. However, the tiny sliver only has enough energy to do localized damage, although with considerable penetration. And they also have a recoil problem.” Now he provided practical details, to let them figure out on their own why their weapon wouldn’t measure up to either of his examples, let alone be an improvement.

“Your longer rod probably has four or five times the mass of a rail gun slug, but the PU rail guns send hundreds of slugs at a target in seconds, with a closing velocity of eighteen or twenty thousand miles per hour, comparable to orbital velocities, because the platform is also in orbit. When there are a lot of guns and thousands of slugs, they’re harder to intercept with lasers, and a spread of them is difficult for a ship to avoid. In spite of that, good armor, as most warships have, will reduce the damage when they do strike.

“A sliver gun’s needle is traveling much faster than a rail gun slug, about ten to twelve miles per second, depending on the power setting, but it has little more mass than a fly. It does impressive damage, penetrating deep for its tiny size, and is impossible to track and hit with a laser. Against a ship or a space dock, it’s a mere insect bite.”

He waited for their logic to deduce what the limits and vulnerability would be for a low rate of fire weapon, with a slow moving massive projectile. They had brilliant scientific minds, so it wasn’t a long wait.

Coldar said, “I have never heard of a sliver gun. That was a curious comparison, although I think one that is completely inapplicable to our current project.” He was capable of some degree of tactfulness.

Blue was less tactful, to the point of uncharacteristic bluntness. “Those are altogether pointless comparisons. Our heavier projectile will reach over a hundred miles per
second
before it even reaches the end of the launch tube, and increases its velocity by at least a factor of ten after that. Unlike your examples, it can receive guidance after exiting the launcher, to improve accuracy if your aim wasn’t too far off from the optimum impact point. The rod will strike its target with perhaps a million times the force of a smaller rail gun slug, and arrive with a vastly higher velocity than does the sliver gun’s projectile. Would that do significant damage?”

To say Mirikami was taken aback would be a gross understatement. “How in hell can you combine their features, and then increase the best aspects of both of those examples, high mass and high velocity, with a weapon you told me is powered only by gravity?”

Coldar asked a basic question, hoping to add a measure of scientific understanding to Mirikami’s misunderstanding of gravity. “Could your new ship, the Mark II, lift off from the surface of a neutron star, assuming it could have survived the landing without being crushed to a smear of atoms?”

“I…, well I don't know. I never gave something like that any thought, or ran a calculation. The Normal Space drive is all that would be available to my ship in that deep a gravity well. We would need a high energy tachyon, caught prior to entering the gravity well, with a mass energy equivalent to or greater than that of the neutron star.” He saw what was being implied, and offered a counter point.

“There isn’t any ship, or crew, that can survive a projected gravity field with the mass of a star inside the volume of its hull. We’d collapse into what would become a black hole, at nearly the velocity of light, not even rotating into Tachyon Space since we’d fall into that from outside the event horizon.”

Blue looked at Coldar, who rotated one eyestalk towards his cohort and said, “Our friend seems to have the capacity to understand the forces involved, but I believe his everyday physical experience with gravity is obscuring his ability to extrapolate.”

Mirikami was annoyed, being talked about as if he wasn’t here. “Blue, your
friend
has the capacity to listen to you if you’d bother to explain it to a nonscientist. I keep telling everyone that I’m a simple Spacer. Explain to a Spacer how gravity will push a rod out of that launcher at thousands of miles per second.”

Coldar modified his explanation, to draw on the experience of the only Spacer in the room. “First, there is no push involved with gravity. If the Mark was at the surface of a normal sized G class star, could its Normal Space drive pull it away?”

“Again, no one would deliberately try that as a test, but I know that it could.”

Blue pounced on his admission. “Excellent. I’m confident you can tell us why the Mark could pull away from the surface of the G class star Coldar described, but probably not from the surface of a far smaller neutron star. What is the difference in those two cases?”

“The force of gravity, naturally. It’s proportional to the square of the distance from the center, and the total mass involved. Closer in, the greater the force, or the greater the space-time curvature, if you prefer. But there can’t be that great a concentration of mass placed close to, let alone inside a ship. How do you propose to do that?”

“Tet, we didn’t say the mass would approach the mass of a star, or even of a planet while the focal point is within the ship’s hull. That was your assumption, because in your everyday experience strong gravity comes from large masses with considerable physical size, and you normally walk on the surface of a planet, far from its center of gravity. Collapsing Koban’s sun into a black hole wouldn’t affect the orbits of its planets. They would be subject to the same curvature of space-time, keeping them moving in their present orbits. As you would agree, you can’t get too close to that event horizon or your Normal Space drive can’t pull you away.”

Mirikami asked, “How small of a mass are you considering, and how close will it be to the rod?”

“It’s small enough and massive enough to produce a tiny black hole at the scale we need, but too low of a total mass to significantly attract objects more than a hand span away. It is mass energy in a very small package, but not massive enough to affect the rest of the ship. Being a mini black hole is why we can’t let it touch the sides of the launcher or the end of the projectile, or it would
eat
groves in our tube and destroy the tip of the rod. That isn’t a problem, not with the atomic level of precision we can use to position the focal point of the gravity field, when it’s physically close to the projectors.”

“OK, so I presume you put the mass of a mountain in your black hole, but that’s not a lot of attraction. I’ve walked on ten-mile-wide asteroids, and a hard toe tap could have put me in orbit.”

“The mass of an even larger asteroid is more like what we use, but as you say, not a lot of attraction, since you could easily fly off its surface if you flexed your foot too hard. In Haven’s gravity, such a mass held a foot over your head would only lift your hair against Haven’s thousands of miles more remote center of gravity. Distance is again the key.”

Trying to be patient, Mirikami reminded them. “I arrived here late because of the visit to the gene labs. I’m not regaining any of that lost time.”

Blue spoke faster. “We can place that mini black hole’s event horizon an atom’s width from the end of the rod. As the rod is attracted to it, the AI will shift the gravitational focal point ahead of the rod’s movement. The acceleration is continuous, there is no back reaction from a thrust on the rod because we are not pushing against its mass. It is essentially in free fall towards that strong gravitational focal point, with the ship’s gravity being insignificant.

“The acceleration of gravity is directly proportional to the mass, and inversely proportional to the distance squared.” He wrote the formula on a wall screen, of
g=G*M/R^2
.

“If we reduce a given separation distance, R, in half, the resulting acceleration is four times higher. We maintain the separation between the rod and the black hole at about the width of a hydrogen atom, so the acceleration is large even though the mass isn’t stellar in scale, and we keep moving the black hole ahead of the rod via our gravity projectors, using the immense tachyon power available to us. We are stealing some small measure of that energy to move the rod, magnifying the effect for the weak force of gravity.

“It’s advantageous because we have unlimited energy which we can control precisely, the launch has no back reaction on the ship, the rod’s speed makes it all but undetectable when fired, and using our gravity projectors, it can change course as it accelerates away, making it hard to detect, and nearly impossible to hit. It probably can’t be traced back to the invisible small ship where it originated if we curve its course slightly as it accelerates, at an ever increasing rate.”

“How does it keep accelerating, and receive steering?” Mirikami wondered.

Once the rod clears the launcher, and pulls a safe distance from the ship, we can greatly increase the tachyon energy fed into the gravitational field, increasing the effective mass of the mini black hole, and the acceleration will increase dramatically. We gradually increase the event horizon’s spacing ahead of the rod with increasing distance, due to focusing uncertainty with greater range, but we think we can achieve a significant fraction of the velocity of light within a few miles, one percent, or a bit more.”