The Everlasting Klingon Battlecruiser

The two(!) Discovery reboots of the D7 are not discussed here. Please refer to the database of Discovery Klingon Ship Classes.
Until TNG and early DS9, the lineage of Klingon battlecruisers was quite plausible. The D7, as it appeared in The Original Series, was in use in the 2260s. It was subsequently replaced by the visually similar K't'inga (the more detailed movie version), which remained in service until the late 24th century. There was a recognizable difference between the two ship classes and, although the service time of the K't'inga was already long, it still appeared credible in that there was at least one older, less advanced design. Whether the K't'ingas are extensive upgrades of existing D7-class ships or new builds used to be a matter of personal preference.

The situation has changed with VOY: "Prophecy" and especially ENT: "Unexpected". The battlecruisers that appear in these two episodes ignore (or retcon) visual evidence from TOS, and extend the lower limit for the life span of the K't'inga design to as many as 225 years.


Screen Evidence


The original D7 battlecruiser, designed by Matt Jefferies, was the only type of Klingon ship during TOS. It was introduced as late as in the third season episode "Elaan of Troyius". Prior to that occurrence Klingon ships had only been mentioned.

The model eventually built for the third season lacked the kind of fine details and the sophisticated lighting the original USS Enterprise model already had. In particular, the hull of the Klingon ship was completely smooth, without visible paneling. The color was the same gray used for the Enterprise, but only for the upper surfaces, while the rest of the model is a grayish green.

The designation as D7 was never mentioned in TOS, but first appeared in the Star Trek Encyclopedia I as a supposedly official designation. Ironically, the most prominent appearance of the D7 miniature was not even as a Klingon ship, but as the Romulan ships of Klingon design in "The Enterprise Incident".


Even though The Animated Series was not considered canon so far, Ronald D. Moore suggested that a D7 variant seen in TAS: "The Time Trap" could be the old D5 ship Kor mentions in DS9: "Once Unto the Breach". The ship is different from the D7 in that it has a protruding sensor (or rather torpedo) tube. Yet, since Star Trek Enterprise we know that the actual D5 is a distinct design that has almost nothing in common with the D7. So the TAS version is most likely just what it looks like and what it was originally meant to be: a slight variant of the standard D7 from TOS. More on the TAS battlecruiser can be found on my page on TAS Alien Ship Classes and in the Guide to Animated Trek.

Star Trek I

The production of "Star Trek: The Motion Picture" (TMP) necessitated a much more detailed model of a Klingon ship than the old one from TOS was. This new battlecruiser type named K't'inga may have been intended to be an upgraded version of the D7, just like the Enterprise in TMP was still supposed to be the very same ship that Kirk had commanded until 2270. The differences are considerable in both cases. Not only were many more details added, but also the proportions of several hull parts were changed. While the Enterprise legacy "forbids" us to doubt that the TMP starship is still essentially Kirk's TV Enterprise, the K't'inga would better be a different class than the D7. This would give either design a shorter overall life span.

Considering that we never saw a very detailed view of the TOS ship (also because there are just not many details!), it may have been possible to claim that the K't'inga was the very same type of ship as the D7 (where D7 may be the Federation designation instead of the obviously Klingon name K't'inga). This interpretation, however, was only an option until DS9: "Trials and Tribble-ations" clearly showed us a newly built D7 by Greg Jein, without all the K't'inga modifications except for the hull panels. Since then it is clear that there is supposed to be a difference indeed.

Star Trek VI

The K't'inga miniature was modified for "Star Trek: The Undiscovered Country". Innumerable tiny greebles were added to the model. Maybe this was intended to show that the Kronos One, as Chancellor Gorkon's flagship, was different from other K't'ingas. On the other hand, the modifications were really only cosmetic and hardly visible on screen, so we may claim that all K't'ingas always looked like this. This actually makes a lot more sense, since, of all spacefaring races, we wouldn't expect the Klingons to add golden ornaments to their ships. The additions must fulfill a purpose. Thus, they should be found on ships other than the Kronos One too.

There is, however, one more obvious difference: the plasma in the nacelles of the Kronos One from "Star Trek VI" shines cyan inside and outside, where there is no shine in TMP. On the other hand, Miranda-class ships suddenly have glowing nacelles since DS9 too. It seems to be much a matter of preference whether the Kronos One is essentially the same as every other K't'inga, or rather a variant. We actually don't know how the plasma flow in Klingon ships is controlled. It is possible that, unlike it seems to be on Federation ships, the nacelles are not lighted all the time.


The K't'inga appeared in TNG a few times where the ship was shown as obsolete. The first times in "Heart of Glory" and in "The Emissary" were stock footage from TMP. During early TNG, the Bird-of-Prey was supposed to be the most advanced and most powerful Klingon ship, although the design can be at most a few years newer than that of the K't'inga. This was emphasized by the sometimes awkward upscaling of this ship type. In their role as capital ships, both the K't'inga and the BoP seem to have been eventually replaced by the Vor'cha that didn't show up until fourth season's "Reunion". The K't'inga, on the other hand, temporarily disappeared at the same time.


In DS9, beginning with "The Way of the Warrior", the K't'ingas suddenly returned as front-line ships, and they took part in all fleet operations during the Dominion War too. The perhaps best explanation is that the Klingons reactivated the aged ships when they urgently needed them for the large-scale invasion of Cardassia.

The plasma in the nacelles of the DS9 K't'ingas shines again, first green and later cyan as on the Kronos One. The absence or presence of the shining plasma, as already hinted at above, is not necessarily a sign that it is a class variant. The different color may point to a class variant though, although two variants at the same time would do anything but facilitate explanations.

Also, in "The Way of the Warrior", we see K't'ingas fire disruptor beams from the very forward end of the command section where the photon torpedo tube is supposed to be located since TMP. This may either be taken as a sign that the ships were refitted to extend their life spans, or it is just another error that we may decide to ignore. Even the Enterprise-D once fired the phaser from the torpedo tube in TNG: "Darmok", which was fixed for TNG-R.

DS9: "Trials and Tribble-ations"

This episode set a standard in that it did not change anything about the shortcomings of the props and sets of the 1960s. The Enterprise model and sets, the tricorders and even the Klingon foreheads are exactly as in the TOS episode "The Trouble with Tribbles". Interestingly, the D7 battlecruiser model didn't even yet exist when "The Trouble with Tribbles" was being produced, but it is a reasonable assumption that Koloth's ship in that episode was one. The only slight change is to the model of the D7, as reconstructed by Greg Jein. He added a faint "feather" pattern to the upper hull, to have at least a bit of details, and to make the difference to more recent Klingon ship models like the K't'inga and the BoP less obvious. Also, the hull color appears to be greenish.

The DS9 episode is actually the only time this design is called "D7" on screen (whereas a second mention in VOY: "Prophecy" refers to the wrong model). The first conclusion we need to draw is that the D7 and the K't'inga are meant to be two distinct designs. Otherwise Greg Jein could just have taken the K't'inga model. Secondly, with small exceptions, this homage to TOS demonstrates that we need to take the visual evidence from TOS seriously. We can't just ignore it and pretend that everything actually looks different (although this would have facilitated the forehead problem a lot).

VOY: "Prophecy"

Unlike DS9: "Trials and Tribble-ations", whose D7 fits in well, the Voyager episode creates a problem in the design history. The K't'inga model (with cyan nacelles like the Kronos One) is used to represent the ship verbally identified as D7 in VOY: "Prophecy". It is possible that D7 is the common Federation designation for both the Klingon cruiser from TOS and the K't'inga and that it only refers to the ship's size and basic structure. If this is so, the question is why Tom states that the class was decommissioned decades ago. This is quite obviously not the case with the K't'inga, although the crew doesn't necessarily know that the Klingons probably pulled many of them off the mothballs for the Dominion War. Therefore we may wish to ignore rather the exact appearance of the ship than the two clear statements.

The ship in "Prophecy" may be actually a D7, maybe a variant that bears a certain similarity to the K't'inga (especially in the bow section that can be seen very clearly), considering that we have never seen a detailed D7 anyway. Alternatively, Tom may be simply mistaken, if we don't want to ignore the K't'inga.

Update notice Mike Sussman, co-author of VOY: "Prophecy" along with Phyllis Strong, tells EAS: "I was reading your 'Everlasting Klingon Battlecruiser' article, and wanted to explain the discrepancy (to the best of my knowledge) in the Voyager episode, 'Prophecy.' As the co-writer on that script, I was the one who dropped the D-7 designation into the dialogue. I knew at the time that we'd seen Greg Jein's D-7 in 'Trials and Tribble-ations' and I assumed the optical department would simply reuse that model. That's what I get for assuming things! When the episode aired, I was surprised to see the movie-era Klingon ship. I believe that by Voyager's seventh season, all the effects were computer generated, and to my knowledge, a CG version of Jein's D-7 did not exist, and it would have cost a fair amount of money to design one in the computer. Had I been aware of this, I would have simply changed Tuvok's line to 'The tetrion readings indicate it's a K't'inga Class cruiser.' And obviously, Tom's line about the D-7 being retired decades ago would have had to be changed as well."

ENT: "Unexpected"

In Enterprise, finally, there is one appearance of a Klingon ship that strains the credibility of the design lineage to the extreme. A Klingon vessel identified by T'Pol as a "Klingon battlecruiser" shows up in ENT: "Unexpected". It is clearly the K't'inga model, and not even a supposedly older D7. More precisely, the ship has the same cyan nacelle color as already the Kronos One, the ship from "Prophecy" and one from DS9: "What You Leave Behind". Enterprise therefore predates the whole class (and even the class variant, if one believes in the nacelle colors as distinguishing marks) by a full 120 years, so that K't'ingas would be in service for at least 225 years(!) altogether, from 2151 to 2376. While it may make sense to refit an old starship several times to keep it up to date, it is implausible that the same basic design should be built without visual changes for up to 200 years. Even if only single ships had been reactivated after 100 years or so, it just would make no sense except for a useless suicide mission.

In a similar fashion as already the Voyager episode where the D7 became the K't'inga, "Unexpected" denies that there was ever a difference between "old" and "new" battlecruisers, as we are clearly shown that there is only one design (variant) for 225 years. In this respect, it is also sad that Enterprise does not bother to pay respect to TOS the way DS9: "Trials and Tribble-ations" skillfully did.

Update notice In Star Trek: The Magazine the issue with the battlecruiser in "Unexpected" was explained: "As Rob (Bonchune) explains, John Eaves had designed a new Klingon ship specifically for this scene. 'It was kind of the same shape as the original Klingon battle cruiser; just a little more primitive. The way John had done it was very much like the original series one, so it had very few windows, and they were small and red. So, when I dropped the ship into the scenes that we had worked out, you couldn't see that it had windows. At the time, it never dawned on me that this would be an issue, but I understand why it is, because in STAR TREK if there are windows they are obvious.' The producers saw the model only a few working hours before the show was due to be delivered. They decided it could only be used with major changes, but after their work on Broken Bow the team was simply too exhausted to work through the night in a desperate attempt to get the shots ready. Instead, the producers made the decision to use an old model. 'We wound up going back to a version of the Klingon ship that had been built for DEEP SPACE NINE,' Mitch (Suskin) says. 'But that particular type of Klingon ship will not be used again, because they decided that it just didn't fit into their vision for this universe.' Rob admits that, he for one, is sorry the old ship was used, but acknowledges there was no alternative. 'As a fan I really regret that that ship is in there, but people were just working too much. After Broken Bow, everyone had already worked so much overtime'." - Apology accepted! Thanks!

ENT: "Judgment"

This episode introduces us to what we can see as a "true" Klingon battlecruiser of the 22nd century, namely the D5. This ship type had been mentioned in DS9: "Once More Unto the Breach" by Kor as an outdated cruiser. Whilst it is pleasant that a fitting ship was designed, unlike it was the case in "Unexpected", the two unfortunately look too different to be the same design.

TOS Remastered

For the remastered version of TOS, a CG model of the original D7 was created, rather than of the K't'inga. The model has a little bit of surface detailing, but unlike in "Trials and Tribble-ations" there is nothing like a feather pattern. Mike Okuda tells us about the CG version used in the remastered episodes: "The Klingon ship was basically in two forms. In early episodes, when it was very small on the screen, it was the original version of the ship, which had essentially no surface detail. In 'The Enterprise Incident', 'Elaan of Troyius', and 'Day of the Dove', the ship was reworked somewhat to add surface texture. And, of course, in 'The Enterprise Incident' we added the Romulan bird markings."

Star Trek (2009)

In "Star Trek (2009)" we can see Klingon "Warbirds" [sic!], whose lines are similar to those of the classic D7 or K't'inga, in the Kirk's Kobayashi Maru scenario in 2258. This has to be a different, previously unseen class though, and the divergent timeline readily justifies its existence.



There is no solution that would allow us to explain all visual evidence and all dialogue. To start with, should we accept that a capital Klingon ship could remain substantially the same for 225 years? The common explanation in fanon is that Klingons are warriors, as opposed to engineers who would more likely frequently come up with new ship designs, is insufficient in my view. Warriors need always the best weapons. Even the good old bat'leth may have been improved several times using new alloys, and the same likely applies to ship hulls. The Klingons are not Hirogen, they want to win a battle and not have the thrill of fighting a superior enemy with traditional hunting rituals (or outdated ships). They are eager to get the new holotechnology in "Unexpected" as well as they quickly adopt cloaking devices prior to "Star Trek III", so it is implausible that their ships should always stay the same.

Moreover, Klingons are at war more or less all the time. They frequently lose and need to replace ships, much rather than an organization of peaceful exploration. When they require new ships anyway, wouldn't this be a perfect opportunity to redesign them? There is even canon evidence for this notion, since T'Pol says, "There are many classes of [Klingon] ships." in ENT: "Sleeping Dogs". During TOS, the Klingons were clearly on the same technological level as the Federation, which makes a lot of sense since it was supposed to reflect the Cold War in the real world. At that time, the Soviets and the Americans kept the balance of power by developing new horrible weapons and countermeasures almost in parallel. It doesn't seem that the Klingons were very busy to develop anything new from 2151 to the end of the Cold War if they are still using up their old rust buckets.

If we believe in the visuals of VOY: "Prophecy" and ENT: "Unexpected", we would have to ignore that TOS/TOS-R and DS9: "Trials and Tribble-ations" showed us a reasonably different ship type, which may have been a predecessor of the K't'inga. If one ship class in service for 225 years is already implausible enough, why should a second ship, very similar to the other one, exist either in parallel for at least 100 years (if the D7 was already in the time of TOS) or only for a short period (which would imply that the D7 was a complete failure and that the fairly new ships were scrapped in favor of a design that was already 120 years old)? Even if we seek the explanation in different ship yards or different Klingon houses building similar yet distinct ships, we would still have trouble with the fact that there were either only D7s or only K't'ingas in what we have seen of the Klingon fleet. Like with the Klingon forehead problem too, this would ultimately require that we ignore the visual evidence in the least "relevant" era (which would once again have to be TOS, as sad as it is).

It is still possible that the Klingons have been building the same basic ship hull with only minor modifications through the centuries. Maybe the Klingons, who were never fond of scientists, generally gained access to new technologies by conquest, and with this strategy they may have hit the wall some time in the 22nd century. Maybe it is a traditional hull shape and there was no need to alter it even as the technology became more advanced. On the other hand, in chronological order we have first seen the K't'inga on Enterprise, then the D7 in TOS and then the K't'inga again, and I wouldn't like to pretend that either the K't'inga predated the D7 or that they are all the same anyway. Maintaining the idea that the battlecruiser is a traditional basic design that didn't change too much in 225 years, it will be best for technical plausibility to respect the difference between D7 (23rd century) and K't'inga (23rd/24th century), and have one design that predates both of them.



In the case of the Klingon battlecruiser I am glad that the people in charge care so much about their job and also about technical continuity. Mike Sussman tells us that the ship we were intended to see in "Prophecy" was the D7. Moreover, the article in Star Trek: The Magazine clearly recommends to ignore the exact look of the battlecruiser in "Unexpected". The ship we were supposed to see is a yet unseen older design. In this light and with the above findings in mind, I think there is no point in making up convoluted explanations why a ship from the 22nd century should look exactly like one from the 24th century, whereas there are variants of the class that exist for only a small fraction of the more than 200 years. Enterprise made up for the error by introducing fitting ships, such as the D5 as a genuine 22nd century battlecruiser. But the ship in "Unexpected" looks so much like the K't'inga and so little like the D5 that it still needs to be explained.

These two suggestions allow us to maintain the D7 as an older variant or rather a predecessor of the K't'inga. It would also provide us with a reasonable design lineage of Klingon ships from what I call the "battlecruiser type" (the design of Eaves's and Bonchune's D4 but perhaps named D6), over the D7 to the K't'inga. The D5 from ENT: "Judgment" may be a different type of battlecruiser of roughly the same age as the unclassified ship. The presumable design lineage is summarized in the following table.

Battlecruiser design evolution


Battlecruiser type (D6?)


From mid-22nd century
to mid-23rd century
From mid-22nd century
to mid-23rd century
From early 23rd century
to around 2270
From around 2270
to around 2376
Length: uncertain Length: unknown Length: 228m Length: 214m


See Also

Klingon Ship Classes - from all eras

Starship Gallery - D7 & K't'inga



Thanks go to Daystrom Institute Technical Library, where I found some more facts and suggestions, and to The Guardian of Forever and Neutral Zone Starship Database for some of the screen caps. Thanks also to Kris Olinger, Tony Midyett, Markus Glanzer, Theron Williams and Daniel Rooth for suggestions. Special thanks to Mike Sussman and Mike Okuda.


Klingon Battlecruiser @ DITL
for a second opinion about this issue


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