"Stutterwarp Revisited", Copyright © 1988, 1998-2005 by
Lester W.
Smith originally appeared in _Challenge_ #33 (pages 50-52).
It is reproduced here by permission of the author.
Text-entry & HTML by:
Steve C.
It is understandable that the development of stutterwarp technology has had one of the greatest effects upon humanity in the history of the race. Suddenly, a culture that had been effectively bound to one star system found itself able to travel easily among the stars. This is not to say that there are now no limitations to where humans can travel, however. The limited availability of tantalum, the material necessary for the working of stutterwarp drives, and the limited distance that a stutterwarp engine can travel before requiring discharge both serve to keep routes of travel within certain boundaries. Perhaps in the future, humans will be able to simply point a ship in any direction and quickly travel any distance to reach their destination. But for now, we must work within the boundaries set upon us by our present understanding of physics.
From Dr. D. Bartholomew Wenthworth's opening comments to his Introductory Physics students, Chandler University, Hermes, the American Arm.
Most people are by now familiar with the basic concepts of stutterwaro operation. For those readers, this article will be of interest in explaining why there is a 7.7 light-year limit on the distance that can be travelled before a discharge is required, and what the effects are on ship and crew if that discharge is not made. The article also reveals a couple of new developments on the American Arm that are allowing the 7.7 limit to be circumvented somewhat. As well, definitions are made of exactly where a stutterwarp can be discharged. Finally, a discussion is included concerning the use of sensors in detecting vessels in space, particularly stutterwarp vessels.
But for those people who are new to the concept of the stutterwarp drive, the following short description is provided.
Stutterwarp drives operate on the same principle as the tunneling phenomenon in certain atomic particles. In essence, they allow a mass to be moved from one location in space to another location in space without travelling through the intervening area. The move is instantaneous. The jump is known as the Jerome Effect, after Dr. Emile Francois Jerome, who first demonstrated it with a hydrogen atom.
The distance that an object can be moved is relatively short in comparison to stellar distances - each jump is only several hundred meters, but the cycling time is very rapid, on the order of hundreds of thousands of times per second. Because of the nature of the jump, the cycling time is fixed, but the amount of charge buildup can vary, allowing distances jumped to be varied according to the travel speed desired. Greater masses require larger charges to jump the same distance as smaller masses, and more powerful engines are able to build these charges more quickly. Therefore, a smaller stutterwarp ship will travel faster than a large ship with the same engine (its lower mass means that each individual jump is longer), and ships with more powerful engines travel faster than ships of the same size with weaker engines (the higher charge means longer individual jumps).
All of this may seem like common sense, but common sense is a dangerous thing to trust when discussing the stutterwarp phenomenon. As an example, objects travelling by stutterwarp seem to have a velocity, but it is purely illusory. There is no feeling of thrust as there is with the use of drives such as those in rockets. If the stutterwarp drive is stopped, the vessel it propels also stops - immediately, completely, without any sense of deceleration. In fact, since stutterwarp movement is only pseudo-velocity, any velocity the vessel has when the stutterwarp is engaged (such as orbital velocity) is retained throughout the stutterwarp travel, even if the two are opposite one another in direction. Typically, therefore, a vessel will make its final approach to its point of destination in such a way as to match the velocity it retains (the orbital velocity from its point of origin) to the orbit it now requires.
As another example, stutterwarp efficiency drops in a gravity field. But this is not a smooth tapering off of efficiency as gravity increases. Instead, there is a sudden drop below light-speed capability at a point when gravity reaches 0.0001 G. A second drop occurs when gravity reaches 0.1 G, reducing stutterwarp efficiency to below that of conventional drives. The reason for these shelves of efficiency are not yet understood. It is, of course, very important for starship crews to be able to predict where these lines occur, but it is also very easy. The surface gravity (in G) of the object being approached is simply divided by the gravity limit being considered (either 0.0001G or 0.1 G); the the square root of the dividend provides the distance from the target object's center (in terms of the object's radius) at which that gravity is reached.
Using Sol as an example, the surface gravity, 27.89 G, can be divided by 0.0001 G for a result of 278,900. The square root of this is 528.11, the number of solar radii at which 0.0001 G is felt. Since Sol's radius is 696,000 kilometers, 0.0001 G can be felt at 376,564,560 kilometers (528.11 radii X 696,000 kilometers) from Sol's center, or 366,868,560 kilometers from its surface (one less radius). This is somewhat over two astronomical units, about the distance from Sol to the asteroid belt. The same formula gives us 10,927,408 as the distance from Sol's surface to the point at which 0.1 G can be felt. Stutterwarp drive efficiency would drop below that of conventional drives at this distance, but this is close enough to Sol (about one fifth of the distance from Sol to Mercury) that the crew of such a vessel could be expected to have greater things to worry about.
As a stutterwarp cycles, it builds up a charge residue on tantalum coils within the drive unit. This residue is not dangerous in itself, but once it passes a threshold limit, the tantalum coils begin to rapdily disintegrate, giving off a deadly radiation that cannot be shielded by any presently developed means. In the course of this disintegration, the drive unit is ruined, and any life forms within several hundred meters are killed by the radiation.
The charge residue on the coils can be easily discharged into any significant gravity well. That is to say, if the drive is maneuvered into a gravity field of 0.1 G or greater, it can be discharged. Therefore, a stutterwarp vessel must approah a body close enough to establish a distant orbit before its drive can be discharged. Unfortunately, this is also the distance at which stutterwarp efficiency drops below that of other drives. For this reason, most starships also have some sort of drive system that allows them to maneuver while this deep into a gravity well. Even starships without secondary drives can maintain orbit by using their stutterwarps to adjust for orbital decay. To leave orbit, these vessels typically plot a trajectory in which they begin to drop toward the body they are circling but are then slingshotted past and out of orbit. Once they pass the 0.1 G limit on their way out, their stutterwarps regain enough efficiency to propel them onward. This can be a tricky maneuver, however, and most crews prefer to use some sort of thruster instead.
The stutterwarp's charge residue is directly related to the distance travelled. Some very experienced engineers can calibrate the drives in such a way that the residue is spread very evenly over all components, allowing discharge to be delayed for up to 24 hours and the total distance travelled to be increased, but this is very difficult. For all practical purposes, 7.7 light-years is the limit. This applies even to drives that are on-line but are not propelling the ship. In some of the earliest experiments with stutterwarp, drones were sent out with double drives. Both drives were running, but only one at a time was actively propelling the drone. The intent was to operate the first drive to the 7.7 light-year limit, dump it, and use the second drive to bring the drone back. The drones never returned. It was soon determined that the second, passive drive had also picked up a residue from the cycling of the first drive. Later, manned vessels proved this theory to be true. The only way an inactive stutterwarp drive could be transported without building up a charge residue on its coils was if it was off-line during the other drive's operation.
The difficulty with this is that many delicate elements of a stutterwarp drive are held in magnetic suspension during operation. It takes many hours and quite a lot of skill to bring an inactive drive on-line and calibrate it without damaging it or destroying it. (It is even more difficult to take an active drive unit off-line without destroying it.) It is, of course, impossible with unmanned probes. Also, the technique has been relatively unimportant until lately because it presumed that any previously running drive would be jettisoned to prevent it from irradiating the ship. But dumping stutterwarp drives is a very expensive way to travel. Recently, however, another use has been found for carrying an inactive drive.
Compared to the other two Arms of human exploration, the American Arm is a dead end. No one knows for sure just how far the branches of the French and Chinese Arms stretch; it is possible that they reach to the farthest edges of the galaxy. The American Arm, however, runs to Zeta Herculis on one branch, Eliis on another, and DM-46 11370 on a third, but no farther. Much effort has been put into breaching these dead ends, and two techniques have recently been developed.
Tugships: The Trilon Corporation recently acquired plans for a stutterwarp tug vessel. This ship is designed to project its stutterwarp field around a ship it tows, allowing the second ship's engines to remain off-line. The tug travels out to 3.85 light-years - half the 7.7 light-year distance - then releases the towed ship and returns to its starting point to discharge. The towed ship then brings its own engines on-line and travels up to another 7.7 light-years - a total of 11.55 light-years distance in all. This technology could expand the number of stars that can be reached to nearly three times the current number.
The problems with tugships are that they are very slow - their drives must move a lot of mass when towing another ship - and there must be a tugship facility at both ends of a route in order to bring the towed ship's engines back off-line and to provide a tug to haul it one-third of the way back in the other direction. (Remember, the towed ship could not travel 7.7 light-years to meet a tug and then be hauled back, for its engines would continue to build a charge residue while it was being towed.)
Brown Dwarfs: Another recent development on the American Arm has been the use of a system to discover the location of solitary brown dwarfs that could serve as discharge points between star systems that are more than 7.7 light-years apart. Near the middle of the 23rd century, facilities began to be built along the American Arm to gather astronomical readings from various locations. By coordinating information gathered at the observatories all along the Arm, astronomical bodies could be located that were previously undiscoverable. Recently, these observatories have turned to the task of locating brown dwarfs. As these brown dwarfs give off very little radiation, they are very difficult for astronomers to locate. By using this system, however, a few brown dwarfs have been identified, and it is expected that more will be found in the future. The difficulties of coordinating such widely scattered observatories are staggering, however, so the program is of limited utility.
Vessels travelling at stutterwarp speeds pose special problems in terms of detecting objects around them. Despite the fact that the vessels are effectively travelling at faster than light, any electromagnetic means they might use to identify themselves or others are still limited to light speed. Continuous beacons located on navigational hazards work well, of course, for the same reason that stars can be seen: The emitted energy is present at every point along a starship's route.
But energy given off by a moving starship, whether intentional such as radio messages, or unintentional such as engine heat emissions, will be outraced by the ship itself. Only within a star's gravity well where stutterwarps drop below light-speed do such emissions run ahead of the ship.
Outside of a gravity well, then, by the time a ship is detected, it is too far away to make the information of much use. Inside a gravity well, on the other hand, it can be picked up by a variety of sensors.
Military Sensors: Military sensors, whether passive or active, are intended for one purpose: tracking a target. As a consequence, they can identify a vessel very accurately, but only at short ranges of less than 20,000,000 kilometers.
Navigational Sensors: Navigational sensors can also be used to detect a ship. Each type of sensor has a different purpose and a different effective range, and these individual differences are described below.
Deep System Scan: Deep system scanners collect electromagnetic emissions such as light and heat from objects in a system. They view one narrow wedge of space at a time, and after many hours of panning across the skies, a picture can be built of what bodies the system in question contains. Deep system scans are very accurate at picking up such things as planets, moons, rings, asteroid belts, and the like. They can also pick up the emissions of a vessel with an actively operating power plant, but cannot identify the vessel for targeting. The effective range for deep system scanners is approximately 150 AU, but obviously the greater the distance to the object being scanned, the less accurate the information concerning its present status and location. Deep system scanners are a passive form of sensor; their operation cannot be picked up by other vessels.
Gravitational Scan: Grav scanners operate as another form of passive sensor. They register the gravitational field of local bodies and project them onto a holographic screen. Because of the ties between stutterwarp technology and gravitational fields, actively operating stutterwarp drives show up as a long line on the grav scan screen. Power plant emissions cannot be picked up by grav scans, however, so a vessel at All Stop could be within a few meters of a grav scanner and not be detected. The effective range of a grav scanner is approximately one AU.
Navigational Radar: Like the deep system scan, navigational radar will indicate the presence of every body within its range. But where deep system scans focus on one narrow wedge of space at a time, navigational radar sweeps the entire surrounding area and projects it onto a holographic screen. Nav radar will only detect an object's presence, not identify what that object is. It will, however, give away the sensing vessel by the radar emissions it gives off when using the navigational radar. This sensor's range is also approximately one AU. It is commonly used for maneuvering in an area where many bodies are present, and many times it is the only sensor mounted on interplanetary commercial vessels.
...Construction and operation may not seem very important to the average citizen in the 24th century. But, as can be determined from the above information, these dictate the development of human space exploration, which in turn has a profound effect on our culture and our economy. The realities of stutterwarp technology, therefore, touch all of our lives. Let us appreciate the labor that has gone into developing it into the tool it is today, and let us support the experts who work to improve it and thus open other worlds to the expansion of our race tomorrow.
- Lester W. Smith