"The Universe of Honor Harrington" - читать интересную книгу автора (Weber David)

(1) Background (General)

The first manned interstellar ship departed the Solar System on September 30, 2103. Although no other ship followed for almost fifty years, 2013 ce, became accepted as Year One of the Diaspora, and January 1 of that year became January 1, 01 pd for purposes of interstellar dating.

For over seven centuries after the Prometheus became the first manned starship, FTL movement remained impossible, leaving generation ships (followed in the fourth century pd by the development of practical cryogenic hibernation vessels) as the only means of long-distance interstellar expansion. The original starships used fairly straightforward reaction drives with hydrogen catcher fields to sustain boost after the initial onboard reaction mass was exhausted. Later generations attempted more esoteric propulsion systems, but though they graduated to fusion and photon drives, they remained locked into the sublight reaction principle until 725 pd, when the first crude hyper drive was tested in the Solar System.

The interface between normal and hyper-space was speed-critical, for if velocity at hyper translation exceeded .3 c, the translating starship was destroyed. In addition, a hypership had to reach the hyper limit of a star's gravity well before it could enter hyper, and the hyper limit varies with the spectral class of the star, as shown in Figure 1.

The original hyper drive was a man-killer. The casualty figures over the first fifty years of hyper travel were daunting. Worse, vessels which were destroyed were lost with all hands, which left no record of their fates and thus offered no clue as to the causes of their destruction. Eventually, however, it was determined that most had probably been lost to one of two phenomena, which became known as quot;grav shearquot; (see below) and quot;dimensional shearquot; (violent energy turbulence separating hyper bands from one another). Once this was recognized and the higher hyper bands were declared off limits, losses due to dimensional shear ended, but grav shear remained a highly dangerous and essentially unpredictable phenomenon for the next five centuries. Despite that unpredictability and continuing (though lower) loss rates, hyperships' FTL capabilities made them the vessel of choice for survey duties and other low-manpower requirement tasks. Crews of highly paid specialists willing to accept risky employment conditions were enlisted for survey work and for the early mail packets, but the loss rate continued to make any sort of interstellar bulk commerce impractical and insured that most colonists still moved aboard the much slower but more survivable cryogenic ships. As a consequence, the rate of advance of colonization did not increase terribly significantly during the period 725-1273 pd, although the ability to pick suitable targets for colonization (courtesy of the FTL survey crews) improved enormously.

The best speed possible in hyper prior to 1273 pd was about fifty times light-speed, a major plus over light-speed vessels but still too slow to tie distant stars together into any sort of interstellar community. It was sufficient to allow establishment of the oldest of the currently existing interstellar polities, the Solarian League, consisting of the oldest colony worlds within approximately ninety light-years of Sol.

The major problem limiting hyper speeds was that simply getting into hyper did not create a propulsive effect. Indeed, the initial translation into hyper was a complex energy transfer which reduced a starship's velocity by quot;bleeding offquot; momentum. In effect, a translating hypership lost approximately 92% of its normal-space velocity when entering hyper. This had unfortunate consequences in terms of reaction mass requirements, particularly since the fact that hydrogen catcher fields were inoperable in hyper meant one could not replenish one's reaction mass underway. On the other hand, the velocity bleed effect applied equally regardless of the direction of the translation (that is, one lost 92% of one's velocity whether one was entering hyper-space from normal-space or normal-space from hyper-space), which meant that leaving hyper automatically decelerated one's vessel to a normal-space velocity only 08% of whatever its velocity had been in hyper-space. This tremendously reduced the amount of deceleration required at the far end of a hyper voyage and so made reaction drives at least workable.

Since .3 c (approx. 89,907.6 km./sec.) was the maximum velocity at which an quot;upwardquot; translation into hyper-space could be made, the maximum initial velocity in hyper-space was .024 c (or 7,192.6 km./sec.). Making translation at speeds as high as .3 c was a rough experience and not particularly safe. The loss rate at .3 c was over 10%; dropping translation velocity to .23 c virtually eliminated ship losses in initial translation, and, since the difference in initial hyper velocity was less than 1,700 KPS, most captains routinely made translation at the lower speed. Even today, only military commanders in emergency conditions will make upward translation at .3 c. There is no safe upper speed on quot;downwardquot; translations. That is, a ship may translate from hyper-space to normal-space at any hyper-space velocity without risking destruction. (Which is not to say that the crews enjoy the experience or that it does not impose enormous wear and tear on hyper generators.) Further, translation from one hyper band to a higher band (see below) may be made at any velocity up to and including .6 c. No vessel may exceed .6 c in hyper (.8 in normal-space) because radiation and particle shields cannot protect them or their passengers at higher velocities.

Once a vessel enters hyper, it is placed in what might be considered a compressed dimension which corresponds on a point-by-point basis to quot;normal-spacequot; but places those points in much closer congruity. Hyper-space consists of multiple regions or layers — called quot;bandsquot; — of associated but discrete dimensions. Dr. Radhakrishnan (who, after Adrienne Warshawski, is considered to have been humanity's greatest hyper-physicist) called the hyper bands quot;the back-flash of creation,quot; for they might be considered echoes of normal-space, the consequence of the ultimate convergence of the mass of an entire normal-space universe. Or, as Dr. Warshawski once put it, quot;Gravity folds normal-space everywhere, by however small an amount, and hyper-space may be considered the 'inside' of all those little folds.quot;

In practical terms, this meant that for a ship in hyper, the distance between normal-space points was quot;shorter,quot; which allowed the vessel to move between them using a standard reaction drive at sublight speeds to attain an effective FTL capability. Even in hyper, ships were not capable of true faster-than-light movement; the relatively closer proximity of points in normal-space simply gave the appearance of FTL travel, which meant that as long as a vessel was dependent on its reaction drive and could not reach the higher hyper bands, its maximum apparent speed was limited to approximately sixty-two times that which the same vessel could have attained in normal-space.

Navigation, communication, and observation all are rendered difficult by the nature of hyper-space. Formed by gravitational distortion, hyper-space itself acts as a focusing glass, producing a cascade effect of ever more tightly warped space. The laws of relativistic physics apply at any given point in that space, but as a hypothetical observer looks quot;outwardquot; in hyper-space, his instruments show a rapidly increasing distortion. At ranges above about 20 LM (359,751,000 km.) that distortion becomes so pronounced that accurate observations are impossible. One says quot;about 20 LMquot; because, depending on local conditions, that range may vary up or down by as much as 12% — that is, from 17.6 LM (316,580,880 km.) to 22.4 LM (or 402,921,120 km.). A hypership thus travels at the center of a bubble of observation from 633,161,760 to 805,842,240 km. in diameter. Even within that sphere, observations and measurements can be highly suspect; in effect, the quot;bubblequot; may be thought of as the region in which an observer can tell something is out there and very roughly where. Exact, precise observations and measurements are all but impossible above ranges of 5,000,000 to 6,000,000 km., which would make navigational fixes impossible even if there were anything to take fixes on.

This seemed to rule out any practical use of hyper-space until the development of the first quot;hyper logquot; (known as the quot;HLquot; by spacers) in 731 pd. The HL is analogous to the inertial guidance units first developed on Old Earth in the 20th century ce. By combining the input from extremely acute sensor systems with known power inputs to a vessel's own propulsive systems and running a continuous back plot of gravity gradients passed through, the HL maintains a real-time quot;dead reckoningquot; position. Early HLs were accurate to within no more than 10 LS per light-month, which meant that, in a voyage of 60 light-years, the HL position might be out by as much as two light-hours. Early hyper-space navigators thus had to be extremely cautious and make generous allowances for error in plotting their voyages, but current (1900 pd) HLs are accurate to within .4 light-second per light-month (that is, the HL position at the end of a 60 light-year voyage would be off by no more than 288 light-seconds or less than 5 light-minutes).

From the beginning of hyper travel, it was known that there were multiple hyper bands and that the quot;higherquot; the band, the closer the congruity between points in normal-space and thus the higher the apparent FTL speed, but their use was impractical for two major reasons. First, translation from band to band bleeds off velocity much as the initial translation. The bleed-off for each higher band is approximately 92% of the bleed-off for the next lowest one (that is, the alpha band translation reduces velocity by 92%; the beta band bleed-off is 84.64%; the velocity loss for the gamma band is 77.87%, etc.), but it still had to be made up again after each translation, and this posed an insurmountable mass requirement for any reaction drive.

The second problem was that the interfaces between any two hyper bands are regions of highly unstable and powerful energy flows, creating the quot;dimensional shearquot; which had destroyed so many early hyperships, and dimensional shear becomes more violent as band levels increase. Moreover, even the relatively quot;safequot; lower bands which could be reliably reached were characterized by powerful energy surges and flows — currents, almost — of highly-charged particles and warped gravity waves. Adequate shielding could hold the radiation effects in check, but a grav shear within any band could rip the strongest ship to pieces.

Hyper-space grav waves take the form of wide, deep volumes of space, as much as fifty light-years across and averaging half their width in depth, of focused gravitational stress quot;movingquot; through hyper-space. Actually, the wave itself might be thought of as stationary, but energy and charged particles trapped in its influence are driven along it at light— or near-light-speed. In that sense, the grav wave serves as a carrier for other energies and remains motionless but for a (relatively) slow side-slipping or drifting. In large part, it is this grav wave drift which makes them so dangerous; survey ships with modern sensors can plot them quite accurately, but they may not be in the same place when the next ship happens along. The major waves in the more heavily traveled portions of the galaxy have been charted with reasonable accuracy, for sufficient observational data has been amassed to predict their usual drift patterns. In addition, most waves are considered quot;locked,quot; meaning that their rate of shift is low and that they maintain effectively fixed relationships with other quot;lockedquot; waves. But there are also waves which are not locked — whose patterns (if, in fact, they have patterns at all) are not only not understood but can change with blinding speed. One of the most famous of these is the Selkir Shear between the Andermani Empire and the Silesian Confederacy, but there are many others, and those in less well-traveled (and thus less well-surveyed) areas, especially, can be extremely treacherous.

The heart of any grav wave is far more powerful than its fringes, or, put another way, a quot;grav wavequot; consists of many layers of quot;grav eddies.quot; For the most part, all aspects of the wave have the same basic orientation, but it is possible for a wave to include counter-layers of reverse quot;flowquot; at unpredictable vertical levels. Despite the size of a grav wave, most of hyper-space is free of them; the real monsters that are more than ten or fifteen light-years wide are rare, and even in hyper the distances between them are vast, though the average interval between grav waves becomes progressively shorter as one translates higher into the hyper bands. The great danger of grav waves to early-generation hyperships lay in the phenomenon known as quot;grav shear.quot; This is experienced as a vessel moves into the area of influence of a grav wave and, even more strongly, in areas in which two or more grav waves impact upon one another. At those points, the gravitational force exerted on one portion of the vessel's structure might be hundreds or even thousands of times as great as that exerted on the remainder of its fabric, with catastrophic consequences for any ship ever built.

In theory, a ship could so align itself as to quot;slidequot; into the grav wave at an extremely gradual angle, avoiding the sudden, cataclysmic shear which would otherwise tear it apart. In practice, the only way to avoid the destructive shearing effect was to avoid grav waves altogether, yet that was well nigh impossible. Grav waves might be widely spaced, but it was impossible to detect them at all until a ship was directly on top of one, and with no way to see one coming, there was no way to plot a course to avoid it. It was possible to recognize when one actually entered the periphery of a grav wave, and if one were on exactly the right vector, prompt emergency evasion gave one a chance (though not a good one) of surviving the encounter, but the grav wave remained the most feared and fearsome peril of hyper travel.

Then, in 1246 pd, the first phased array gravity drive, or impeller, was designed on Beowulf, the colonized world of the Sigma Draconis System. This was a reactionless sublight drive which artificially replicated the grav waves which had been observed in hyper-space for centuries. The impeller drive used a series of nodal generators to create a pair of stressed bands in normal-space, one quot;abovequot; and one quot;belowquot; the mounting ship. Inclined towards one another, these produced a sort of wedge-shaped quasi-hyper-space in those regions, having no direct effect upon the generating vessel but creating what might be called a quot;tame grav wavequot; which was capable of attaining near-light speeds very quickly. Because of the angle at which the bands were generated relative to one another, the vessel rode a small pocket of normal-space (open ahead of the vessel and closing in astern) trapped between the grav waves, much as a surfboard rides the crest or curl of a wave, which was driven along between the stress bands. Since the stress bands were waves and not particles, the quot;impeller wedgequot; was able, theoretically, at least, to attain an instantaneous light-speed velocity. Unfortunately, the normal-space quot;pocketquot; had to deal with the conservation of inertia, which meant that the effective acceleration of a manned ship was limited to that which produced a g force the crew could survive. Nonetheless, these higher rates of acceleration could be maintained indefinitely, and no reaction mass was required; so long as the generators had power, the drive's endurance was effectively unlimited.

In terms of interstellar flight, however, the impeller drive was afflicted by one enormous drawback which was not at first appreciated. In essence, it enormously increased the danger grav shear had always presented to reactor drive vessels, for the interference between the immense strength of a grav wave and the artificially produced gravitic stress of an impeller wedge will vaporize a starship almost instantly.

In the military sphere, it was soon discovered that although the bow (or quot;throatquot;) and stern aspects of an impeller wedge must remain open, additional quot;sidewallquot; grav waves could be generated to close its open sides and serve as shields against hostile fire, as not even an energy beam (generated using then-current technology) could penetrate a wave front in which effective local gravity went from zero to several hundred thousand gravities. The problem of generating an energy beam powerful enough to quot;burn throughquot; even at pointblank ranges was not to be solved for centuries, but within fifty years grav penetrators had been designed for missile weapons, which could also make full use of the incredible acceleration potential of the impeller drive. Since that time, there has been a constant race between defensive designers working new wrinkles in manipulation of the gravity wave to defeat new penetrators and offensive designers adapting their penetrators to defeat the new counters.

The interstellar drawbacks of impeller drive became quickly and disastrously clear to Beowulf's shipbuilders, and for several decades it seemed likely that the new drive would be limited solely to interplanetary traffic. In 1273 pd, however, the scientist Adrienne Warshawski of Old Terra recognized a previously unsuspected FTL implication of the new technology. Prior to her Fleetwing tests in that year, all efforts to employ it in hyper-space had ended in unmitigated disaster, but Dr. Warshawski found a way around the problem. She had already invented a new device capable of scanning hyper-space for grav waves and wave shifts within five light-seconds of a starship (to this day, all grav scanners are known as quot;warshawskisquot; by starship crews), which made it possible to use impeller drive between hyper-space grav waves, since they could now be seen and avoided.

That, alone, would have been sufficient to earn Warshawski undying renown, but beneficial as it was, its significance paled beside her next leap forward, for in working out her detector, Dr. Warshawski had penetrated far more deeply into the nature of the grav wave phenomenon than any of her predecessors, and she suddenly realized that it would be possible to build an impeller drive which could be reconfigured at will to project its grav waves at right angles to the generating vessel. There was no converging effect to move a pocket of normal-space, but these perpendicular grav fields could be brought into phase with the grav wave, thus eliminating the interference effect between impellers and the wave. More, the new fields would stabilize a vessel relative to the grav wave, allowing a transition into it which eliminated the traditional dangers grav shear presented to the ship's physical structure. In effect, the alterations she made to Fleetwing to produce her quot;alpha nodesquot; provided the ship with gigantic, immaterial sails: circular, plate-like gravity bands over two hundred kilometers in diameter. Coupled with her grav wave detector to plot and quot;readquot; grav waves, they would permit a starship to literally quot;set her sailsquot; and use the focused radiation hurtling along hyper-space's naturally occurring grav waves to derive incredible accelerations.

Not only that, but the interface between sail and natural grav wave produced an eddy of preposterously high energy levels which could be quot;siphoned offquot; to power the starship. Effectively, once a starship quot;set sailquot; it drew sufficient power to maintain and trim its sails and also for every other energy requirement and could thus shut down its onboard power plants until the time came to leave hyper-space. A Warshawski Sail hypership thus had no need for reaction mass, required very little fuel mass, and could sustain high rates of acceleration indefinitely, which meant that the velocity loss associated with quot;cracking the wallquot; between hyper bands could be regained and that use of the upper bands was no longer impractical.

This last point was a crucial factor in attaining higher interstellar transit times. The maximum safe velocity in any hyper band remained .6 c, but the higher bands, with their closer point-to-point congruencies, added a significant multiplier to the FTL equivalent of that velocity. Prior to the Warshawski Sail, not only had dimension shear made translating into the upper bands dangerous, but the successive velocity losses had made it highly uneconomical for any reaction drive ship. Now the lost velocity could be rapidly regained and the higher, quot;fasterquot; bands could be used to sustain a much higher average velocity. As a result, the dreaded grav wave became the path to ever more efficient hyper travel, and captains who had previously avoided them in terror now used their new instrumentation to find them and cruised on standard impeller drive between them.

Of course, there wasn't always a grav wave going the direction a starship needed, but with the grav detector to keep a ship clear of naturally occurring grav waves impeller drive could, at last, be used in hyper-space. In addition, it was possible for a Warshawski Sail ship to quot;reachquot; across a wave (which might be thought of as sailing with a quot;quartering breezequot;) at angles of up to about 60° before the sails began losing drive and up to approximately 85° before all drive was lost. By the same token, a hypership could sail quot;close-hauled,quot; or into a grav wave, at approach angles of 45°. At angles above 45°, it was necessary to quot;tack into the wave,quot; which naturally meant that return passages would be slower than outgoing passages through the same region of prevailing grav waves. Thus the old quot;windjammerquot; technology of Earth's seas had reemerged in the interstellar age, transmuted into the intricacies of hyper-space and FTL travel. By 1750 pd, however, sail tuners had been upgraded to a point which permitted the quot;grab factorquot; of a sail to be manipulated with far more sophistication than Dr. Warshawski's original technology had permitted. Indeed, it became possible to create a negative grab factor which, in effect, permitted a starship to sail directly quot;into the wind,quot; although with a marginally greater danger of sail failure.

The Warshawski Sail also made it possible to quot;crack the wallquot; between hyper bands with much greater impunity. Breaking into a higher hyper band was (and is) still no bed of roses, and ships occasionally come to grief in the transition even today, but a Warshawski Sail ship inserts itself into a grav wave going in the right direction and rides it through, rather like an aircraft riding an updraft. This access to the higher bands meant the first generation Warshawski Sail could move a starship at an apparent velocity of just over 800 c, but an upper limit on velocity remained, created by the range capability of the vessel's grav wave detectors. In the higher bands, the grav waves were both more powerful and tightly-spaced due to the increasingly stressed nature of hyper-space in those regions. This meant that the five-light-second detection range of the original Warshawski offered insufficient warning time to venture much above the gamma bands, thus imposing the absolute speed limitation. In addition, the problems of acceleration remained. The Warshawski Sail could be adjusted by decreasing the strength of the field, thus allowing a greater proportion of the grav wave's power to quot;leakquot; through it, to hold acceleration down to something a human body could tolerate, but the old bugaboo of quot;g forcesquot; remained a problem for the next century or so.

Then, in 1384 pd, a physicist by the name of Shigematsu Radhakrishnan added another major breakthrough in the form of the inertial compensator. The compensator turned the grav wave (natural or artificial) associated with a vessel into a sort of quot;inertial sump,quot; dumping the inertial forces of acceleration into the grav wave and thus exempting the vessel's crew from the g forces associated with acceleration. Within the limits of its efficiency, it completely eliminated g force, placing an accelerating vessel in a permanent state of internal zero-gee, but its capacity to damp inertia was directly proportional to the power of the grav wave around it and inversely proportional to both the volume of the field and the mass of the vessel about which it was generated. The first factor meant that it was far more effective for starships than for sublight ships, as the former drew upon the greater energy of the naturally occurring grav waves of hyper-space, and the second meant it was more effective for smaller ships than for larger ones. The natural grav waves of hyper-space, with their incomparably greater power, offered a much quot;deeperquot; sump than the artificial stress bands of the impeller drive, which meant that a Warshawski Sail ship could deflect vastly more g force from its passengers than one under impeller drive. In general terms, the compensator permitted humans to endure acceleration rates approaching 550 g under impeller drive and 4-5,000 g under sail, which allows hyperships to make up quot;bleed-offquot; velocity very quickly after translation. These numbers are for military compensators, which tend to be more massive, more energy and maintenance intensive, and much more expensive than those used in most merchant construction. Military compensators allow higher acceleration — and warships cannot afford to be less maneuverable than their foes — but only at the cost of penalties merchant ships as a whole cannot afford.

In practical terms, the maximum acceleration a ship can pull is defined in Figure 2.

These accelerations are with inertial compensator safety margins cut to zero. Normally, warships operate with a 20% safety margin, while MS safety margins run as high as 35%. Note also that the cargo carried by a starship is less important than the table above might suggest. The numbers in Figure 2 use mass as the determining factor, but the size of the field is of very nearly equal importance. A 7.5 million-ton freighter with empty cargo holds would require the same size field as one with full holds, and so would have the same effective acceleration capability.

Note also that in 1900 pd, 8,500,000 tons represented the edge of a plateau in inertial compensator capability. Above 8,500,000 tons, warship accelerations fell off by approximately 1 g per 2,500 tons, so that a warship of 8,502,500 tons would have a maximum acceleration of 419 g and a warship of 9,547,500 tons would have a maximum acceleration of 1 g. The same basic curves were followed for merchant vessels.

In 1502 pd, the first practical countergravity generator was developed by the Anderson Shipbuilding Corporation of New Glasgow. This had only limited applications for space travel (though it did mean cargoes could be lifted into orbit for negligible energy costs), but incalculable ones for planetary transport industries, rendering rail, road, and oceanic transport of bulk cargoes obsolete overnight. In 1581 pd, however, Dr. Ignatius Peterson, building on the work of the Anderson Corporation, Dr. Warshawski, and Dr. Radhakrishnan, mated countergrav technology with that of the impeller drive and created the first generator with sufficiently precise incremental control to produce an internal gravity field for a ship, thus permitting vessels with inertial compensators to be designed with a permanent up/down orientation. This proved a tremendous boon to long-haul starships, for it had always been difficult to design centrifugal spin sections into Warshawski Sail hyperships. Now that was no longer necessary. In addition, the decreased energy costs to transfer cargo in and out of a gravity well, coupled with the low energy and mass costs of the Warshawski sail itself and the greatly decreased risks of dimensional and grav shear, interstellar shipment of bulk cargo became a practical reality. In point of fact, on a per-ton basis, interstellar freight can be moved more cheaply than by any other form of transport in history.

By 1790 pd, the latest generation Warshawskis could detect grav wave fronts at ranges of up to just over twenty light-seconds. A hundred years later (the time of our story) the range is up to eight light-minutes for grav wave detection and 240 light-seconds (4 light-minutes) for turbulence detection. As a result, 20th Century pd military starships routinely operate as high as the theta band of hyper-space. This translates an actual velocity of .6 c to an apparent velocity of something like 3,000 c. The explored hyper bands and their bleed-off factors and speed multipliers over normal-space are given in Figure 3.

In addition to his inertial compensator, Dr. Radhakrishnan also enjoys the credit for being the first to develop the math to predict and detect wormhole junctions, although the first was not actually detected until 1447 pd, many years after his death. The mechanism of the junction is still imperfectly understood, but for all intents and purposes a junction is a quot;gravity fault,quot; or a gravitic distortion so powerful as to fold hyper-space and breach the interface between it and normal-space. The result is a direct point-to-point congruence between points in normal-space which are seldom separated by less than 100 light-years and may be separated by several thousand. A hyper drive is required to utilize them, and ships cannot maintain stability or course control through a wormhole junction without Warshawski Sails. Nonetheless, the movement from normal-space to normal-space is effectively instantaneous, regardless of the distance traversed, and the energy cost is negligible.

The use of the junctions required the evolution of a new six-dimensional math, but the effort was well worthwhile, particularly since a single wormhole junction may have several different termini. Wormholes remain extremely rare phenomena, and astrophysicists continue to debate many aspects of the theories which describe them. No one has yet proposed a technique to mathematically predict the destinations of any given wormhole with reliable accuracy, but work on better models continues. At the present, mathematics can generally predict the total number of termini a wormhole will possess, but the locations of those termini cannot be ascertained without a surveying transit, and such first transits remain very tricky and dangerous.

There are other ambiguities in the current understanding of wormholes, as well. In theory, for example, one should be able to go from any terminus of a wormhole junction directly to any other. In fact, one may go from the central nexus of the junction to any of its other termini and vice versa but cannot reach any secondary terminus from another secondary. That is, one might go from point A to points B, C, or D but could not go from B to C or D without returning to A and reorienting one's vessel.

Despite their incompletely understood nature, the junctions opened a whole new aspect of FTL travel and became focusing points or funnels for trade. There were not many of them, and one certainly could not use them to travel directly to any star not connected to them, but one could move from any star within a few dozen light years of a wormhole terminus to the terminus then jump instantly three or four hundred light-years in the direction of one's final destination with a tremendous overall savings in transit time.

In addition, of course, the discovery of wormhole junctions and a technique for their use imposed an entirely new pattern on the ongoing Diaspora. Theretofore, expansion had been roughly spherical, spreading out from the center in an irregular but recognizable globular pattern. Thereafter, expansion became far more ragged as wormhole junctions gave virtually instantaneous access to far distant reaches of space. Moreover, wormhole junctions are primarily associated with mid-range main sequence stars (F, G, and K), which gives a high probability of finding habitable planets in relatively close proximity to their far termini.

Once initial access to the far end of a wormhole junction had been attained, the habitable world at the far end (if there was one) tended to act as the central focus for its own quot;mini-Diaspora,quot; creating globular quadrants of explored space which might be light-centuries away from the next closest explored star system.