The Universe of Honor Harrington

(2) Warshawski Sail Logistics

By their very natures, the impeller drive and Warshawski Sail had a tremendous impact on the size of spacecraft. With the advent of the impeller drive, mass as such ceased to be a major consideration for sublight travel. With the introduction of the Warshawski Sail, the same became true for starships, as well. In consequence, bulk cargo carriers are entirely practical. Transport of interplanetary or interstellar cargoes is actually cheaper than surface or atmospheric transportation (even with countergrav transporters), though even at 1,200 c (the speed of an average bulk carrier) hauling a cargo 300 light-years takes 2.4 months. It is thus possible to transport even such bulk items as raw ore or food stuffs profitably over interstellar distances.

By the same token, this mass-carrying capability means interstellar military operations, including planetary invasions and occupations, are entirely practical. A starship represents a prodigious initial investment (more because of its size than any other factor), but it will last almost forever, its operational costs are low, and a ship which can be configured to carry livestock and farm equipment can also be configured to carry assault troops and armored vehicles.

Hyperships come in three basic categories: the low-speed bulk carrier; the high-speed personnel carrier; and warships.

The maximum acceleration and responsiveness of a Warshawski Sail starship is dependent upon the power or "grab value" of its sails and the efficiency of its inertial compensator. The more powerful (and massive) the sail generator, the greater the efficiency with which it can utilize the power of the grav wave; the more efficient the compensator, the higher the acceleration its crew can endure. Moreover, it requires an extraordinarily powerful sail, relative to the mass of the mounting ship, to endure the violent conditions of the upper hyper bands. This means that larger ships, with the hull volume to devote to really powerful sails, have greater inherent power and maximum theoretical average velocities (transit times) because they ought to be able to pull more acceleration from a given grav wave (thus reaching their optimum velocity of .6 c more rapidly) and to access the higher hyper bands (where the "shorter" distances effectively multiply their .6 c constant velocity by a quite preposterous factor).

There are, however, offsetting factors. The more powerful a Warshawski Sail, the slower its response time in realigning to a shift in the grav wave. This is potentially disastrous, but is, once more, offset to some extent by the ability of the more powerful sail to withstand greater stress. That is, it isn't as necessary to the starship's survival that it be able to reset or trim a sail to survive fluctuations in the grav wave about it. Put another way, a bigger ship with more powerful generators can "carry more sail" under given grav wave conditions than a smaller vessel and, all other things being equal, run the smaller vessel down.

But, of course, things aren't quite that simple. For starters, a smaller, less massive vessel gains more drive from the same sail strength. Because it is less massive, it accelerates more quickly for the same power. And the inertial compensator, marvelous as it may be, becomes more effective as its field area grows smaller and the mounting vessel's mass decreases, which means that a smaller ship can take advantage of its acceleration advantage over a larger vessel riding the same grav wave (and hence having access to the same "inertia sump") without killing its crew. If the smaller vessel can accelerate to .6 c (the highest survivable speed in hyper-space) before the larger ship, the larger ship's theoretical speed advantage is meaningless, as it can never overhaul. Under extreme grav wave conditions, the larger ship can maintain a greater effective acceleration, compensator or no, because the smaller ship's lighter sails are forced to "reef" (reduce their "grab factor") lest their generators burn out. This is particularly true in and above the zeta band, and few merchant ships ever venture that high. Even fairly small warships tend to have extremely powerful sails for their displacement, so that they can reach those higher bands, but smaller ships are simply unable to match the mass of a large ship's sail generators. This means that in some circumstances the larger ship can climb higher in the hyper bands and/or derive sufficiently more usable drive from a grav wave to offset its lower compensator efficiency.

In addition, smaller ships with less powerful sails can trim them much more rapidly and with greater precision. In wet-navy terms, smaller ships tend to be "quicker in the stays," able to adjust course with much greater rapidity and to take the maximum advantage of the power available to them from a given sail force. This means that a smaller ship with an aggressive sail handler for a captain can actually turn in a faster passage time over most hyper voyages than a bigger ship. There are, however, some passages (known to starship crews as "the Roaring Deeps") where exceptionally powerful, exceptionally steady grav waves operate. In these regions, the bigger ship, with its more powerful sails, is able to make full use of its theoretical advantages and will routinely run down smaller vessels.

In sublight movement, the larger vessel's more powerful sails (which equate to a more powerful impeller drive, as well) do not give it a speed advantage because of the nature of the inertial compensator. The curve of the compensator's most efficient operation means that a smaller vessel (with a smaller area to enclose in its compensator field) can pull substantially higher accelerations, and no amount of brute impeller power can create an artificial grav wave with a sufficiently deep inertial sump to overcome this fundamental disadvantage of a large ship. Capital ships thus are as fast as lighter warships in sustained flight but tend to be slower to accelerate or decelerate.

The tuning or trimming components of a Warshawski Sail generator are its most expensive and quickest wearing parts, and they wear out much more rapidly on more powerful generators with their higher designed power loads. Because of this, bulk carriers tend to use relatively low-powered sails and the lower hyper bands, which limits their practical speeds to perhaps 1,000-1,500 c. Passenger ships and those vessels specializing in transport of critical cargoes accept the higher overhead cost associated with more powerful sails and run in the range of 1,500-2,000 c. For the most part (though there are exceptions) only warships are designed around the most powerful sails and compensators their displacement will permit, giving speeds of up to 3,000 c. A bulk carrier's tuning components may last as long as fifty years between replacements and those of a passenger ship up to twenty years, but a warship is likely to require complete tuner overhaul and replacement as frequently as once every eight to ten years. On the other hand, a warship may spend decades "laid up" in orbit, making no demands at all upon its sails, so the actual life span of a given set of tuners may vary widely between ships of the same class, depending upon their employment history.