Background informationfor the Iagyh War storiesby Frej Wasastjerna
Inversion drive, inversion bombs(see Early Warning, Reconnaissance) According to the laws of physics in the Iagyh War universe, under certain circumstances particles can change mass from positive to negative, a process known as inversion. This releases an amount of energy equal to 2mc2. For this to happen, a very intense gravitational field is required, obtained by compressing a mass of at least 1013 tons (usually a fair-sized asteroid) to the verge of collapse into a black hole. This compression is obtained with a gravity amplifier, which produces a brief burst of intense gravity, compressing any surrounding matter and destroying itself in the process. After the initial compression, magnetic fields are used to move the mass, known as a drive kernel, and to control its rate of spin, which controls the rate of energy release. The drive kernel can remain active and release energy even when its mass has dropped considerably below the 1013 ton limit needed to initiate the reaction.
In an inversion ship, the energy released by the drive kernel is used to propel the ship. In the earliest inversion ships, positive and negative mass particles annihilated each other with no further energy release. (Charge was conserved through simultaneous annihilation of positively and negatively charged particles, easily ensured at the very high density prevailing in a drive kernel.) The energy released by the inversion process took the form of hard gamma rays, converted into light by an atmosphere of matter evaporating from the hot kernel. This light was reflected by a light sail about a million kilometers in diameter, propelling the ship. In later, more sophisticated designs the energy was used to accelerate charged particles to high energies. These particles were then channeled aft by magnetic fields, propelling the ship. The negative mass particles were also not annihilated but were accelerated forward, providing additional thrust and energy.
The drive kernel can be shut down by speeding up its spin to the point where its gravity is no longer sufficient to keep it compressed, but then it can no longer be restarted unless a new gravity amplifier is provided and the remaining mass exceeds the 1013 ton limit. If, on the other hand, the spin is slowed down far enough, the drive kernel will collapse into a black hole, instantaneously releasing an energy equivalent to much of its remaining mass. This will release an extremely intense burst of hard gamma radiation. This is how an inversion bomb works.
Nega-mass propulsion(see Reconnaissance, Till Death Do Us Part) Once drive kernel technology had progressed to the point where negative mass particles could be obtained, applications were promptly found for that. Nega-mass factories were built (usually in the far outer reaches of planetary systems, for safety) in which the primary purpose of a drive kernel was to produce nega-mass, with vast amounts of energy as a side benefit.
The most important application of nega-mass was spacecraft propulsion. Consider a positive mass of +m and a negative mass of -m with a force F, say a repulsive force, acting between them. The positive mass will accelerate away from the negative mass at a rate of a = F/m. The negative mass will be thrust away from the positive one by the repulsive force, but a negative mass accelerates in a direction opposite to a force working on it, so it will accelerate toward the positive mass. Its acceleration will be a = (-F)/(-m), the same as that of the positive mass provided the absolute values of the masses are the same. Thus the two will go on accelerating in the direction of the positive mass so long as the force acts on them. Note that no energy is expended, since the masses do not move relative to each other. This does not violate conservation of energy, because the net mass is zero and the kinetic energy remains zero. Momentum is conserved for the same reason.
The conservation of momentum and energy holds for unequal masses as well, which can be demonstrated as follows. (Readers who want to avoid math can skip this paragraph.) Let us consider a positive mass of m+ and a negative mass of -m-, both initially at rest. (Note that m- denotes the absolute value of the negative mass.) At time 0 a force F starts acting between them. At time t their velocities are v+ = Ft/m+ for the positive mass v- = -Ft/(-m-) = Ft/m- for the negative mass, both in the same direction. They have moved the distance s+ = ½Ft2/m+ for the positive mass and s- = -½Ft2/(-m-) = ½Ft2/m- for the negative mass. Their total momentum is p = m+(Ft/m+) - m-(Ft/m-) = 0. Their total kinetic energy is Ekin = ½m+(Ft/m+)2 - ½m-(Ft/m-)2 = ½(Ft)2/m+ - ½(Ft)2/m-. This is non-zero if the masses are unequal, but the work done by the force is W = Fs+ - Fs- = ½(Ft)2/m+ - ½(Ft)2/m-, which is the same as the kinetic energy, so energy is also conserved.
A nega-mass ship uses lumps of negative-mass matter, technically known as pips, enclosed in pip chambers where they are held in place by electromagnetic forces. In principle a ship with exact balance between positive and negative mass, zero net mass, could travel through space using only these forces and expending no energy, provided it were not affected by any outside forces except gravity (for the effect of gravity on negative mass, see below). In practice exactly zero net mass is hard to achieve and maintain, and spaceships are affected by surface forces such as light pressure and stellar winds. These surface forces are small but cannot be neglected by nega-mass ships. Therefore it is customary for nega-mass ships to maintain a slightly positive net mass and to use an auxiliary drive, usually exhaust from a fusion reactor, to provide the thrust needed to accelerate the net mass to the desired velocity. Of course this means a slow decrease in the net mass, so to keep it in the desired range a ship may jettison small nega-mass pips from time to time. Another type of auxiliary drive that is sometimes used on in-system ships is the plasma propeller, a set of electromagnetic fields acting on the plasma of a stellar wind. Using this plasma as reaction mass avoids the mass loss of a fusion drive, but it works only in environments where the plasma density is sufficient.
It is considered desirable to keep not only the total mass of a ship close to zero but also the dipole and quadrupole moments of mass, to ensure that the ship can accelerate freely in any direction and to facilitate turning. If the forces acting on the positive and negative masses are not sufficiently well balanced to keep them in their proper relative positions, the results is called mass misalignment. In mild cases this merely leads to a non-zero dipole moment of mass. If the ship then accelerates in a direction not aligned with the dipole, this results in a tendency for the ship to turn relative to the negative mass distribution, leading to worse misalignment. If a misalignment gets bad enough, the pips may touch the chamber walls. Since a pip accelerates in a direction opposite to the force acting on it, this contact may make the pips push harder and harder against the walls, leading to dangerously high acceleration of the ship or to the pips tearing through the walls and exiting the ship, piercing anything that gets in their way. Thus serious mass misalignment is something that must be avoided.
In a gravitational field negative mass tends to fall downward just like positive mass. In Newtonian terms, the gravitational force between positive and negative masses is repulsive, but this makes the negative mass accelerate towrds the positive one. In terms of general relativity, the curvature of space-time affects all masses equally, regardless of their magnitude or even sign.
Thus gravity does not interfere with the operation of a nega-mass ship with proper mass balance. Keeping the pips from falling requires a downward-directed force acting on them, and the reaction will thrust the ship upward, enabling it to hover if required.
However, unloading a nega-mass ship with near-zero net mass in the loaded state causes problems. This will result in a substantial negative net mass. If the force acting on the pips is sufficient to prevent them from falling, the weight of the positive mass will be insufficient to keep it from accelerating upward. If the force is just sufficient to balance the weight of the positive mass, it will be insufficient to keep the pips from falling. Either way a serious mass misalignment will ensue. It is, of course, possible to choose the former option and then use some kind of auxiliary drive to keep the ship in place, but this is at least inconvenient and may be impossible if the auxiliary drive is not strong enough. Civilian freighters or passenger ships use two ways of solving this problem: either they take on ballast, usually water, after having landed but before unloading, or the spaceport is equipped with equipment to grab the ship and hold it in place.
Landing on a planet with an atmosphere also requires taking into account such forces as buoyancy, winds and air resistance. To overcome these, nega-mass ships intended to enter atmospheres are usually equipped with propellers or ion jets.
Military spaceships and missiles (see Reconnaissance, Till Death Do Us Part) In the Iagyh War, inversion bombs were not used much. Sterilizing a planet with inversion bombs requires at least 4 such bombs in a tetrahedral pattern, preferably
To kill all opposition on a planet, a more effective means is a heavy rammer missile. Take an inversion ship, accelerate it to its maximum kinetic energy and ram a planet. For an Earth-size planet hit by a standard-sized heavy rammer missile, the impact is not quite sufficient to blow the planet apart but ample to blow the atmosphere, hydrosphere and part of the crust into space and to melt any remaining solid rock. This has the disadvantage that the planet is not habitable or even suitable for terraforming for a long time afterwards, but in a desperate conflict for survival this is not a fatal flaw.
Inversion ships can also be used as transports. Since the mass of an inversion ship is immense anyway, one can load a trillion tons or so of cargo on it without slowing it down much. For this reason, inversion ships were widely used for interstellar colonization, and they were also used to transport troops. However, it was realized by human strategists at the outset of the war and by their Iagyh counterparts not long afterward that conquering a planetary system held by a prepared enemy is very difficult, partly because the defender usually has at least a decade longer to prepare. On the other hand, heavy rammer missiles are very hard to stop, partly because of their mass, partly because the defender has little warning since the missiles follow hard on the heels of any light or other radiation revealing their approach. Thus destroying a planetary system, except for its gas giants, is easy.
For small moons and asteroids, oneills (O'Neill-type space colonies) and such, using heavy rammer missiles to destroy them is wasteful. Instead light rammer missiles were used. Typically such a missile would be a massive metal rod equipped with a nega-mass drive. The pips would be jettisoned somewhat before impact, given sufficient lateral velocity to miss the target, to ensure that they would absorb none of the impact energy.
To mop up any remaining opposition, warships were used. These were unmanned, controlled instead by artificial intelligences that could stand higher accelerations than a human or Iagyh, required no life support systems and could think about a million times faster than protoplasmic brains. They were also more intelligent, though usually not very creative, and immune to such problems as boredom.
Ground troops were also mainly robotic. The reconnaissance mission described in Reconnaissance and Azzy was an exception. In the last wars fought by humans before encountering Iagyhs, no artificial intelligences worthy of the name existed yet, so there was no experience of how they would have behaved in war. Nor was there time to conduct a thorough research,development and testing program to develop reliable combat robots. On the other hand, ample historical information on human behavior in war existed, although it was all nearly seven centuries old or older. Thus it was decided to use humans for this mission. Likewise, it was decided to use mainly twenty-first century designs for weapons because they had been battle-tested. (Also, very little progress had happened in small arms technology, partly because post-twenty-first century discoveries in physics were mostly not applicable to small arms, partly because weapons development had been discouraged or forbidden in the pacifistic societies that emerged from the ruins left by the Fourth World War.)
Some human cultures resented the fact that robots had reduced humans to passive bystanders in war, as in so much else. This led to the development of methods to record a human personality and transfer it into an electronic brain. Till Death Do Us Part describes what the results could be like.
Space warships mostly used nega-mass propulsion because of their theoretically unlimited delta-v, allowing interstellar travel, their stealth and their excellent maneuverability, permitting high acceleration in any direction without a need to turn. Their main weapons were nega-mass missiles, which could be launched without upsetting the mass balance of the ship and which themselves enjoyed the advantages recounted above.
A typical "short-range" nega-mass missile was slightly larger than a beer can and contained an electronic brain (of rather limited intelligence, since a highly intelligent brain would have required a larger missile and would not have been much more useful), sensors for finding the target and homing on it, several lasers and telescopes for tight-beam communication with the launching ship and other missiles, a considerable number of small pip chambers, some kind of auxiliary drive (usually microrocket arrays) and a few grams of antimatter as a warhead. "Long-range" missiles were also built, with some of their pip chambers in a ring-like structure surrounding the body of the missile and connected to it through wires that could be shortened or lengthened. The resulting ability to move these pip chambers relative to the rest of the missile conveyed a greater tolerance for mass misalignment, making the missiles less susceptible to being disabled by such external factors as shock waves from explosions, but this advantage was slight, at least compared to late-generation short-range missiles, and the bulk and poor stealth of long-range missiles led to their being used in relatively small numbers.
Warships typically also carried an armament of lasers and neutbeams (neutral-particle beams), but since the power available from the small fusion reactor of a warship was not all that great, and since at least neutbeams were rather un-stealthy, these beam weapons were mostly limited to use as defenses against missiles -- and were, in fact, not very effective against the thousands of missiles a ship might launch.
Stealth (see Reconnaissance, Till Death Do Us Part) Since a nega-mass drive uses no energy, warships in the Iagyh War could be quite stealthy even when accelerating. This potential was used heavily by both sides. While civilian ships usually maintained a positive net mass of hundreds of grams or more, warships preparing for combat usually adjusted their net mass to a few grams. They also had low-observable auxiliary drives such as mass drivers. Since a warship using only passive sensors and not firing beam weapons needed little energy, it was also possible to keep the surface cool. In particular, when enemy forces were expected to be nearby, the surface of a warship would be cooled by liquid helium to about 2.7 K, the temperature of the cosmic microwave background, though this low a temperature could not be maintained indefinitely. Thus the infrared emissions of the ship would be undetectable. The surface coatings of warships were designed to absorb electromagnetic radiation at all wavelengths as well as possible, especially in the radar and optical wavelength ranges.
In addition, warships were given angular shapes intended to reflect incoming electromagnetic radiation in only a few directions, where it was hoped that the enemy would not be. There were also attempts to develop active devices to suppress radar echoes through destructive interference, but the problems bedeviling this approach were never satisfactorily solved.
Of course, much effort was also expended on developing instruments to detect enemy ships, but nonetheless stealth had the upper hand in the Iagyh War. Most often enemy ships would be detected because they happened to occult a star or were silhouetted against a nearby planet, a nebula or another extended object. A sufficiently powerful and sensitive radar could detect enemy ships out to some tens of kilometers, but it would also reveal the position of the transmitting ship to enemies thousands of times more distant.
The same methods were also used to make nega-mass missiles stealthy and worked even better for them, aided by their small size.
Appearance of ships For early inversion ships, the dominant feature of their appearance was the lightsail, about a million kilometers in diameter. When the drive was active and the ship was viewed from the rear, there would also be an extremely brilliant light source.
More modern inversion ships are roughly spherical in shape, some hundreds of kilometers in diameter. Although the fraction of the produced energy that was released as electromagnetic radiation is carefully minimized, there is still enough of it to make the spherical shell glow brightly at least in the infrared, often even at visible wavelengths.
In-system nega-mass ships can have just about any shape. One popular shape is a cylinder with pointed ends and a fusion reactor at each end. The reactor can in principle be an open lattice of superconducting coils enclosing the hydrogen-boron or hydrogen-lithium plasma, but in most planetary systems it is legally required to be enclosed in X-ray shielding.
The void between planetary systems is a very good vacuum by most standards but is not completely empty. As tenuous as the interstellar medium is, hitting the atoms in it at relativistic speeds produces harmful radiation, and the ship needs to be shielded from it, especially if it carries passengers, whether actively living or in nanosuspension. Thus interstellar nega-mass ships are very slightly tapered cylinders or multi-sided prisms with a shield at the thick end. There is usually a fusion reactor at the center of mass, which tends to be close to the thick end. Therefore, if the reactor is not enclosed (in warships it always is for the sake of stealth), the cylinder or prism is interrupted near the thick end, with the reactor visible in the gap.
In civilian ships the front surface of the shield is usually flat, but in warships it is normally slanted or pyramid-shaped for stealth reasons.
Other issues
Each of the four main cultures of Thalassa (shippers, dwalers, fliers and spacers, see Early Warning) contained numerous ethnically based subcultures. The Taucet Space Marines preferred to staff each unit with members of the same subculture as far as possible. Thus the squad to which Vladimir Polikarpov belonged was composed mainly of spacers of Russian origin, still speaking Russian among themselves.
By the time the Iagyh War broke out, both humans and iagyhs had reached a scientific and technological plateau from which further progress was very difficult. In fact the iagyhs, somewhat more intelligent than humans but less creative, had been stuck on that plateau for millennia and would probably never have progressed beyond it. Humans managed to do that only after the war had already lasted for centuries.
Out-takes I want to preserve from earlier story versions
After the men had taken care of their ablutions and dressed, a crewman brought them their breakfast -- field rations. "Hmmpff! I suppose they want us nice and angry when we go down so we ll fight hard," Sergei Rogatchi grumbled, as he inserted the rations in the microwave oven above his bunk to heat them. (From Reconnaissance, before the assault)
One well-known disadvantage [of the nega-mass drive] was the need to maintain mass balance, keeping the ship's net mass very close to zero to minimize the requirement for auxiliary propulsion. Another, less well-known disadvantage, (From Reconnaissance)
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