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 "inertial sump," 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 "deeper" 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 "bleed-off" 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 "gravity fault," 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.