Voyager, as a series, places a great emphasis on drive technologies. Centered as it is on the epic seven year journey of the USS Voyager across the galaxy, it provides a very interesting look at warp drive.
In summary, Voyager averages a speed of ~10,000c towards Earth, and was anticipated to average ~1,000c. As Voyager's path is not quite a straight line, Voyager's total average speed is slightly higher in both cases - as much as 2000c and 20,000c respectively.
Voyager consistently has difficulties with its warp core and with fuel supplies. This helps to explain why Voyager is most often slow ; however, Voyager also moves at moderate and fast speeds . It is unclear why Voyager's current speed varies so wildly, but it seems as if given adequate fuel supplies and an intact warp drive, it would seem as if Voyager could have traveled home in somewhere between three months and three years.
Voyager also gives some key details of the warp core's operation. Warp plasma ranges in the millions of kelvins and is maintained at 2.5-50 megapascal pressures; warp drive may be engaged near planets, although not within atmosphere. Meanwhile, FTL sensors can pick up ships at 3-20 light years' range reasonably accurately under most circumstances.
The Voyage of Voyager
By taking the episodes in order, we can estimate Voyager's average speed in each interval. Seasons 4 and 5 in particular are filled with information about Voyager's progress, while seasons 1-3 involve relatively little travel on Voyager's part, and seasons 6-7
In the beginning of the series ("Caretaker"), Voyager is flung "more than" 70,000 light years from home. It is estimated that Voyager will need 75 years to get back, or slightly under 1,000 c. The series takes place over a span of roughly seven years, meaning that the average speed towards home is slightly over 10,000c.
Numerous incidents display a dramatic difference between the distance Voyager has traveled and the distance remaining. For example, Voyager has traveled at least 10,000 light years before "The Year of Hell," and still has 65,000 light years remaining, meaning that Voyager traveled 2 light years for every light year closer it got towards Earth.
A similar thing happens in "Gravity," where Paris expects Voyager to have been averaging 1800c away from his current position, and in "Dark Frontier," where a 20,000 light year Borg conduit moving Voyager from 50,000 to 35,000 light years from Earth saves 15 years of travel.
The theme of Voyager desperately searching for fuel and needed engine parts will be repeated in "Phage," "The Cloud," "Heros and Demons," "Tattoo," "Resistance," "Innocence," "Flashback," "Blood Fever, "Real Life," "Demon," "Bliss," and other episodes; apparently the Caretaker incident did quite a number on the engines. Dilithium, polyferranide, antimatter, deuterium, tellerium - they need everything.
In "Course: Oblivion," duplicate Voyager is 2 years from home on a straight line trip through the core of the galaxy. Duplicate Voyager's warp core is described as healthy. It seems as if Voyager has been having an uneventful trip lately, and everything going right.
It is revealed that this duplicate was created in "Demon" around the end of the fourth season; in the episode immediately afterwards ("One"), Voyager is placed as having traveled 15,000 light years. Bracketing with other episodes, the time passed between the two episodes has been somewhere between 3 months and a year.
This means that duplicate Voyager traveled an average speed of 20,000-27,000c towards Earth at a steady supercruise on its healthy and well-fueled warp core (built by the demon planet), and would have made the whole voyage in only 2.6-3.5 years.
"Equinox" gives us an even more remarkable example of the value of good fuel. The U.S.S. Equinox travels 10,000 light years in two weeks using a normal warp drive and an alternative fuel source; this is an average speed of 260,000c. Presumably, given a sufficient quantity of fuel, Voyager could match or exceed this speed.
Warp drive details:
"Caretaker" - 2100 kilopascals reported in the warp core as a microfracture threatens a core breach; this is reported as a pressure at which the dilithium reaction may not be restarted. later, this is stabilized to 2500 kilopascals, to everyone's relief. 53 megapascals is critical pressure - "Twisted." The warp core itself operates under roughly 25 atmospheres of pressure - possibly more normally.
In "Persistence of Vision," Kes sets the warp core to a sequence involving a 3 million kelvin temperature.
"Parallax" - the warp core's efficiency is "down another 14 percent." The condition of Voyager's engine is quite clear. By "Resistance" a season later, the reaction rate is "down to 12 percent" as a result of an emergency; dialogue indicates the reaction rate was returned to at least 18 percent before normal operation of the ship resumed.
"Tattoo" tells us that the warp engines, engaged without inertial dampers, would leave nothing of the crew but smears on the wall.
"Flashbacks" states clearly for the record that ships of the TOS/STI-VI era were "half as fast" as modern vessels. In "11:59," Ensign Kim informs us that space travel in 2210 involved stasis for a six month trip to Beta Capricornis. Presuming this means Beta Capricorni, which is a complex star system 328 light years from Earth, giving 660c for colony vessels midway between ENT and TOS.
Territory "hundreds of sectors" across in "The Swarm" would add 15 months at maximum warp, which (incidentally) Voyager cannot achieve.
The narrowest point turns out to be 4 days at maximum warp to conveniently cut through. 12 hours at warp 9.75 covers a third of this.
"Year of Hell" - the Krenim time ship is limited to warp 6 thanks to its propulsion system and mass.
"Prey" - a Hirogen ship, with its dicyclic warp engines, has covered a great deal of ground in the past five years, and impressively visited 90 star systems in the past year.
"Drone" - a warp core produces "4,000 teradynes per second." This seems a difficult statement to explain (a dyne is a unit of force), although not much more than the order to vent "three million isodynes" from the warp nacelles in "Gravity."
In order to go to warp in "Dragon's Teeth," Voyager must clear the thermosphere for 280 km of altitude. "Fury" - it's not recommended to make turns while at warp.
In a story Neelix tells in "The Haunting of Deck 12," the crew collected enough deuterium to fuel them for a thousand light years. It turns out the story was true, and this was one of the technical details that the ex-Borg children didn't correct him on.
The Grand Voyage:
"Caretaker" - "more than" 70,000 light years, and an estimated 75 years' travel.
Voyager then spends three seasons (three years) covering very little distance.
"The Gift" - at the beginning of the fourth season, Kes throws Voyager "beyond Borg space" - a distance of 9,500 light years, which is estimated to take ten years off travel time. Equivalent travel in originally estimated travel time: Slightly under 13 years.
Four episodes later, in "The Raven," Voyager is stated to be 10,000 light years from Borg space.
Two episodes after "The Raven," in "Year of Hell," Seven of Nine makes a course plot correction estimated to shave 5 years off the trip. As this is explicitly stated to be exactly three years after the activation of the EMH, which happens in "Caretaker," Voyager has 57 years of travel remaining.
At day 70 of the "Year of Hell," Voyager is cited to be 65,000 light years from home, in spite of having covered at least 10,000 light years in previous episodes. With roughly 57 years remaining, Voyager is expected to average 1,140c, and scheduled for a wide detour around Krenim space.
"Message in a Bottle" - Voyager contacts the USS Prometheus through the Hirogen network. Distance is 60,000 light years. The Caretaker incident is referred to as "four years ago," meaning that Voyager has averaged 5,000c over the last year.
In "Hunters," they are again ~60,000 light years from home; although aired after "Message in a Bottle," this is noted as "almost four years" from the Caretaker incident.
By "One," Voyager has covered 15,000 light years. 110 light years are traveled during "One," and an additional 300 are gained through the use of a slipstream drive in "Hope and Fear." We may optimistically call this three months travel or so based on how direct a route Voyager seems to be taking.
Total equivalent travel time remaining: 55.75 years.
Season five begins with "Night," where a 2500 light year wide expanse of emptiness awaits. This is anticipated to require 2 years and 2 months to cross; skipping it after two months shaves two years off. Total travel time remaining: 53.5 years.
By "Timeless," Voyager has been in the Delta Quadrant for "four years, two months, eleven days." A brief slipstream journey shaves ten years off the time, leaving them 50,000 light years from home in "Gravity;" The remaining distance home could be covered in three months using quantum slipstream drive, according to the bogus message. Arcturis, however, intends to travel in several hours to Borg space. Time remaining: 43.5 years - i.e., Voyager needs to average 1,150c towards Earth, or would have averaged 200,000c using the slipstream drive.
Paris expects Voyager to have covered 300 more light years in the first apparent two months he was stuck on the ground, for a current speed of 1800c.
In "Dark Frontier," Voyager gains 20,000 light years and 15 years from a Borg conduit. Travel time remaining: 28.5 years.
By the end of the season and the beginning of the new season, "Equinox," they are 35,000 light years from home, and expected to average 1,230c towards Earth.
"The Voyager Conspiracy" - Voyager has been travelling for five years (we are now deep into the sixth season.) A subspace catapult slings Voyager possibly as much as 5,000 light years, shaving three years off their journey in one hour's travel - three years average travel carried out at 1,700c, apparently. Travel time remaining: 24.75 years. Average speed towards Earth required: 1,210c.
"Live Fast and Prosper" - Voyager is apparently 30,000 light years from home, according to con artists posing as Janeway and Chakotay. Neelix confirms that Voyager is the only Federation starship in 30,000 light years. Then, in "Imperfection," Janeway describes Voyager as 30,000 light years closer to home. In season seven, "Inside Man" places Voyager still ~30,000 light years from home.
Voyager is capable of very swift motion for a brief about of time - up to warp 9.975, according to "Caretaker" and "Relativity," which should be very fast given that "Threshold" places warp 10 at infinite speed. However, it very often moves at a speed measurably slower than 1,000c.
The "Dreadnaught" will reach a system 10 light years away in three weeks' time, for a speed of ~170c. After increasing speed to warp 9, it is 51 hours from the target. Similarly, in "Lifesigns," a system ten light years away is one that Voyager will "pass nearby" in roughly 22 days for a cruising speed of ~170c. In "Counterpoint," a nebula 2.36 light years away will take Voyager two days to travel to, for a speed of 430c.
In "One," a nebula over 110 light years across would require a over a month to travel through, and over a year to fly around - suggesting that Voyager can't clock much more than 500c while flying around the Nebula.
Two days of high warp gets Voyager 3.8 light years in "Hunters," placing Voyager's high warp at 700c.
In "The 37s," Paris states that Voyager's top speed is a rather more moderate 4 billion miles per second, i.e., 21,500c. In "Maneuvers," they intend to use the transporter at a relative speed of half that - 2 billion miles per second, i.e., 10,750c. Scanners located the ship at 0.4 light years' distance.
40 light years would take Voyager five days in "Scorpion," giving us an overall speed of 3,000c for Voyager in a hurry. In "Hope and Fear," it takes Voyager two days at "high warp" to catch up to a moment's 15 light year slipstream travel.
In "Memorial," the Delta Flyer scanned fifteen planets in fourteen days. This suggests reasonable speeds in light of Voyager's overall progress.
In "Inside Man," the USS Carolina could zip 0.7 light years over to a red giant in two hours at maximum warp. After over one hour, they are still a half light year away, although still on track to arrest the Ferengi, placing their speed as 4400c faster than the Ferengi.
"Flesh and Blood" - a Hirogen ship and Voyager will catch up to a hijacked Hirogen ship with two hours' time and a starting gap of a half light year. This places Voyager at 2200c faster than the hijacked ship. In "Prey," a half light year takes some other Hirogen ships four hours to cover, for a speed of 1100c.
"Time and Again" - While travelling at warp 7, they will be "passing" a red dwarf system in forty minutes, and can shortly tell if there are M-class planets or not. This suggests remarkably high speed, as in "Emanations," in which Voyager travels 0.6 light years in what appears to be a matter of seconds. In "Favourite Sun" - while limping away at warp 3, Voyager will be caught in two minutes, and will pass a star system in the mean time.
"Alliances" - scanning for a shuttle should work within two light years.
A full sweep in "Threshold" comes up negative for any signs of a shuttle within five parsecs.
The Voth pick up Voyager easily at 90 light years in "Distant Origin."
"Scorpion:" Voyager picks up a transwarp signature 5.8 light years away. Moments later, Voyager has been pulled out of warp.
The Borg then close to 2.1 light years with a fleet of fifteen vessels. Moments later, they are in "visual range." The cubes scan them, and then pass on.
Voyager loses sensor lock at 5.1 light years out, after the cubes are defeated.
"Collective" - a Borg cube sneaks up on the Delta Flyer using a dispersal field.
"Flesh and Blood" - Voyager detects a highjacked Hirogen vessel 50 seconds out.
"Workforce" - Chakotay has a real-time chat with the EMH at eight light years' distance. Due to the extreme range, the signal was transmitted using a triaxialating frequency on a covariant subspace band.