Warp Propulsion System Operations
This document presents a brief description and discussion of the treknology behind Star Trek’s warp propulsion system. This material is based on reference materials such as the ST: TNG Technical Manual and the ST Encyclopedia. Any errors are solely my own responsibility. Comments or questions can be addressed to me via e-mail at firstname.lastname@example.org. For sake of simplicity and to enable easier understanding of the material, I am essentially ignoring or bypassing the pseudo-physics that lay behind the operation of the WPS and concentrating on the operational aspects of the system.
Section 1: Basic Description
The standard warp propulsion system (WPS) has 4 major components: the M/ARA (the Matter/Anti-matter Reactor Assembly—commonly referred to as the warp core); the EPS (Electro-Plasma System) distribution system; the Flight Control System (FCS)—which is shared with the Impulse and Reaction Control Systems (IPS and RCS, respectively); and the warp nacelles, which contain the warp coils and associated controls and support equipment. In addition, the ship’s SIF (Structural Integrity Field) and IDF (Inertial Damping Field) are required to be in operation.
The M/ARA provides the massive amounts of energy necessary for FTL travel (on the order of 2.44x1013 Megajoules is required to travel at warp 9.9—equivalent to the energy released by approximately 90 photon torpedoes) through a controlled matter/anti-matter reaction. The M/A reaction generates energetic plasma that is distributed to the warp nacelles and to ship hotel and equipment loads via the EPS conduits. Transformation of the plasma to a form of energy that can be used by the equipment occurs at or near the equipment, rather than in a central location.
Major EPS conduits run from the M/ARA to the nacelles (since this is the largest energy load on the ship). At the nacelles, the plasma is distributed to the warp coils in a sequence and amount determined by the FCS in order to generate the subspace fields necessary to achieve the desired velocity.
The WPS is non-Newtonian in nature—meaning that it is a reactionless drive. Motive force is supplied by a series of nested subspace fields (commonly called warp fields). Each field exerts a controlled amount of force against the previously generated field (picture, if you will, a series of soap bubbles expanding from a central source, each of which is "pushing" off of the bubble outside of it). The velocity vector is determined by the shape, timing, and strength of the field bubbles in a phenomenon called Asymmetrical Peristaltic Field Manipulation (APFM). APFM parameters are determined and controlled by the FCS.
The warp coils in the nacelle are energized in sequence from fore to aft. Warp factor (speed) is determined by the number of field layers, which in turn is determined by the firing frequency of the coils. The higher the firing frequency, the higher the warp factor.
Subspace field strength is measured in cochranes (named after the inventor of the Terran warp drive, Zefram Cochrane). There is a direct correlation between cochrane number, warp factor, and velocity in multiples of c (the speed of light):
Warp 1 = 1 cochrane = 1c
Warp 2 = 10 cochranes = 10c
Warp 3 = 39 cochranes = 39c
And so on… a complete listing of cochrane numbers and warp factors are available in the ST:TNG Technical Manual and the ST: Encyclopedia
The numbers listed above (and in the references) are ideal—the actual cochrane values are dependent upon the conditions obtaining in the space that the ship is traveling through, such as gas density, electric and magnetic fields present, and fluctuations in local subspace.
Power requirements are a function of the cochrane value of the warp field—the higher the cochrane value, the more energy required. Also, it takes a greater amount of power to initially establish the field than it does to maintain the field once it is established—this is called the peak transitional threshold. Once the threshold is crossed, power requirements are reduced. Graph 5.1.1 (Warp speed/power graph) on page 55 of the ST:TNG Technical Manual outlines the power requirements for warp flight).
It is also possible to travel at fractional warp factors (i.e. warp 2.5). A fractional warp factor occurs when the field strength exceeds that necessary for travel at a particular warp factor, but is insufficient to cross the transitional threshold to the next higher warp factor. Due to the specifics of the power curve between cochrane value and warp factor, however, it is often more energy efficient for prolonged travel to travel at the next higher integral warp factor (see graph 5.1.1 in the ST:TNG Tech Manual for details, p. 55).
Upper Velocity Limitations
As currently measured, the warp factor scale runs from 1 (the speed of light) to 10 (infinite speed). It is possible to asymptotically approach, but not to reach, warp 10 using current WPS designs. Power demand rises geometrically as warp 10 is approached. At the same time, coil efficiency drops dramatically due to material limitations. As warp 10 is approached, the required field frequency becomes higher and higher, finally becoming unattainable because it 1) exceeds the ability of the FCS to control and 2) the time interval required becomes shorter than Planck time (1.3x10-43 seconds)—the currently smallest possible unit of measurable time. Thus, even if it were possible to generate the nearly infinite amount of power required, it would be beyond the limitations of control systems to reach that velocity.
Section 2: Operations
WPS operations are controlled primarily by the FCS, in conjunction with engineering power generation and distribution control. Control is highly autonomous due to the short time intervals and complexity involved in FTL maneuvers.
Baseline course is entered into the FCS by the Flight Control Officer (FCO) with reference to the current navigational database and the transit requirements dictated by the ship’s operational requirements and tactical situation. Actual course followed is continually updated and adjusted as new data becomes available or as conditions change—with oversight provided by the FCO.
Maneuverability while in warp is made possible by selectively altering field strength, geometry, and frequency to alter the imparted velocity vector. Two warp nacelles (and associated coil sets) are used to create two balanced, interacting fields for vehicle maneuvers—WPS’s utilizing a singular or an odd numbered/asymmetric arrangement of nacelles require more complex control protocols and are usually avoided, if possible, within the design constraints. Experiments conducted in 2269 indicated that two nacelles are the optimum number for power generation and ship control.
Maneuvers while in warp are accomplished as follows. Yaw maneuvers (right and left turns) can be accomplished by selective alteration of field frequency generated by each nacelle. The ship will turn away from the side with a higher field frequency (because that side is moving slightly faster than the other side—much like turning a tracked vehicle by using differential braking). Pitch maneuvers (pitching the bow up or down) are accomplished by altering field geometry by increasing or decreasing the plasma flow to the forward warp coils in each nacelle, moving the axis of movement up or down in relation to the original baseline course. Banking movement is done by selectively altering pulse timing and field strength on each nacelle, thus moving one side up or down.
While the WPS produces no acceleration forces that act directly on the fabric of the ship, selective alteration of field parameters induces field stresses and field imbalances that are felt by the structure of the ship—by causing sections of the ship to move at slightly different velocities (thus requiring the use of the ship’s Inertial Damping Field (IDF) and Structural Integrity Field (SIF)).
Starship hull geometry affects warp operations by imparting geometric correction factors (for course maintenance and alterations) and by providing (or lacking) streamlining against local spatial conditions such as gas density (remembering that the warp field geometry is dependent in some regards upon hull geometry).
The WPS does not produce direct acceleration stresses on the ship’s structure or crew during operations (ST:TNG Tech Manual, p. 25), but stresses due occur due to field differentials between the fields generated by the 2 warp nacelles. This means that IDF and SIF operation is required during FTL travel. This also implies that warp maneuverability on a per ship basis is greater than the same ship’s maneuverability when using the IPS at STL velocities, because 1) acceleration stresses are not a concern and 2) the subspace fields have the additional property of effectively reducing the apparent mass of the vehicle. Thus roll, pitch, and yaw rates will be enhanced (within the operational parameters of the FCS’s ability to coordinate the movements). Maneuvers will take more space to perform (due to the higher velocity) but will take less time to accomplish.
Section 3: Fuel and Energy Considerations
Specific volume figures used are those for Galaxy class starships (such as the Enterprise-D). The Enterprise-D has a total anti-matter fuel capacity of 3000m3. Anti-deuterium has a density of 142 kg/m^3 at its boiling point—giving a Galaxy class starship a total of 426,000 kg of anti-matter (AM). Warp field energy requirements are based upon sustained travel and not the peak transitional threshold energy requirements.
At warp 6 (normal cruise velocity for the Enterprise-D), 1.176x109 MJ are required to form the required 392 cochrane field. 1 kg of anti-matter yields approximately 1.8x1011 MJ (also accounting for the kg of normal matter consumed). Thus, 0.00325 kg/sec of anti-matter are consumed traveling at warp 6. This means that it would take 4.15 years to consume the Enterprise-D's AM fuel load (which fits in with the 3 year mission duration when you factor in hotel and tactical energy loads—these loads appear to consume approximately 0.0009 kg of AM per second on average—or 3.26x108 MW. Most of this energy consumption would be caused by the tactical systems, such as shields and weapons).
At warp 9, 1.2128x1012 MJ are required to form the 1516 cochrane warp field. This translates to 3.37 kg/sec of AM consumption—which means that it would take only 35.11 HOURS to consume the total fuel load of a Galaxy class ship. This figure seems both logical and reasonable (remember that hotel and tactical energy loads will reduce this figure).
At warp 9.9, 2.7261x1013 MJ are required to form the 3029 cochrane warp field. This translates to 151.45 kg/sec of AM consumption—meaning that it would take 46.9 MINUTES to consume the total fuel load of a Galaxy class ship. Of course, at warp 9.9, engine auto-shutdown occurs after 10 minutes of operation.
Section 4: Additional Questions and Considerations
The Technical Manual is unclear as to whether the warp field energy requirements given are applicable to all ships or only to the Enterprise-D. Two arguments can be made: 1) the requirements are platform specific (due to differences in the generated field size and geometry necessary for specific platforms); or 2) the requirements are general—due to the fact that a 300 cochrane field is a 300 cochrane field, no matter where it is generated. The non-specific labeling of the graph on page 55 tends to support argument 2—but argument 1 seems to be more technologically viable.
During TNG, specific limitations were placed upon Starfleet vessels concerning traveling at speeds greater than warp 5 (due to damage caused to subspace by travel at higher warp factors). This problem seems to have been corrected by Starfleet R & D and a re-engineering of warp field geometries. The moving nacelles on Intrepid class ships seem to represent one specific solution to this problem.
The anti-matter used as fuel by starships is manufactured by Starfleet—using a combination of solar and fusion power in order to minimize energy losses. Even so, energy efficiency is still only 86% for the process (see p. 67 of the Tech Man for details). This loss is acceptable because of the capabilities and energy density provided by using anti-matter as fuel.
Section 5: Why it will take Voyager more than 75 years to get home.
Voyager started off (IIRC) about 70,000 light years from the nearest border of the UFP. The assumption in the Voyager seems to be that 9,500 LY equals 10 years travel (950 LY/year). This would mean that Voyager is traveling at an AVERAGE speed of 950c (or about warp 7.822). If Voyager spends only 25% of their time trying to find supplies, make trade deals, stop to see the pretty subspace anomaly, help the Borg defeat Species 8472.... etc, then the actual speed would have to be 25% higher to maintain the average speed (meaning that they would have to travel at ~1188c—or about warp 8.365. If they spend 50% of their time doing these things, then Voyager would have to travel at 1425c, and so on.
Traveling at warp 8 (1024c--keeping the numbers easy) requires 1.54x10^11 MJ (per unit time) to form and maintain the required warp field. As noted above, the energy yield of 1 kg of AM is 1.8x10^11 MJ, so this means that 0.85 kg of AM are consumed per second at warp 8. Voyager's precise fuel capacity is unknown, but a figure of 60% of a Galaxy class' capacity (which is probably high) seems to be a reasonable basis for calculation--this is about 256,000 kg.
At warp 8 it would take less than 3.5 DAYS to consume all of Voyager’s AM fuel. At this point, Voyager would either have to buy or make more AM. They may or may not be able to buy some. To make this much AM requires at least 2,560,000 kg of deuterium (not plain old hydrogen, but deuterium). While there is lots of H floating around, 2H is not so easy to find (I forget the exact isotopic ratio between H and 2H). Collecting and processing this amount of 2H would require several days (increasing the speed that Voyager needs to maintain in order to maintain the AVERAGE speed of 950c).
This would soon become a vicious circle. In a trip of 60 years (accounting for the 10 years that Kes gave them) this means that Voyager would have to stop to refuel 6,446 times--about 107 times a year. If it takes two days on average to refuel (which, I believe is being VERY generous) then 214 days a year are spent refueling, say another 30 days are spent doing various other things (the stuff we see on the episodes)--for a total of 244 days per year of down time. This leaves 121.25 days for travel (this is about 33% of the year).
This amount of down (or non-travel) time would require a travel speed of 1672c (above warp 9) to maintain the 950c average speed, and the fuel consumption rate would increase by more than a factor of 7--which means that Voyager would have to refuel after about 12 HOURS of travel--requiring another increase in speed to again make up for lost time.
It seems obvious to us as members of the audience that SOMETHING will happen to get the ship home. It will be "unexpected" and will shave decades off the travel time (maybe Kes will come back, or Q will intervene, or they will find a wormhole, etc.). The normal travel time to the UFP means nothing, because that is not how they are going to get there.
If you go to the ST Encyclopedia and look at the warp chart, it takes 10 years at warp 8 to cover 10k LY--70 years to travel 70k LY. Warp 8 is not a sustainable speed for logistical reasons (see above). Warp 6 is a bit more sustainable and it would take 25 years to cover 10k LY and 175 years to cover 70k LY at that speed. So, minus the 10 years that Kes saved them, you are looking at 165 years for Voyager to get back to the UFP at an AVERAGE speed of warp 6.
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