The Starfleet Delta Symbol
by Bernd Schneider and Brad Wilder
Evolution of the SymbolEnterprise vs. Fleetwide UsageAddendum
The delta, sometimes also referred to as arrowhead, is the most recognizable insignia of Starfleet in-universe, and arguably of Star Trek in the real world as well. It exists since the earliest days of TOS and was worn by the crew of the original Enterprise as a chest patch. The insignia only became more common since the TOS movies and ultimately since TNG when it started to appear in many other forms. This article looks at the development of the symbol with countless examples.
Its widespread use raises the question whether the well-known symbol, now clearly standing for Starfleet as a whole, represented only the Enterprise at the time of TOS, to which there are different answers, depending on whether we lean more towards intent or towards canon usage including retcons. The article discusses these two different interpretations.
Finally, we also look at the outliers: premature uses of the delta and odd symbol variations.
Evolution of the Symbol
The Starfleet delta shows up in hundreds of variations, so here are just examples of the most common patterns, the most striking appearances, the most notable changes and the most curious forms of usage. The occurrences are listed in roughly chronological production order, ordered by series.
TOS pilots
We can see the Starfleet delta in both TOS pilots as chest patches. They are on all uniforms, with the exception of medical garments and field jackets. While the colors are still pale, the department symbols inside the deltas are already similar to how they would appear in the regular TOS episodes. Only the assignment of certain symbols to certain uniform colors is not yet consistent; they appear in seemingly random combinations. The delta itself starts off as a golden patch with golden embroidered edges in "The Cage", set in 2254. This version looks a bit cheap because of the coarse finish and harsh contrast of the black central symbol to the golden patch ground, and because the latter has no clear outline. Both was changed for the insignias in TOS: "Where No Man Has Gone Before" (ca. 2265). The patch, with its new and thinner black edge, as well as the symbol, are better defined now. The delta insignias from the second pilot almost look like those of the regular episodes, but somewhat smaller.
The Original Series
The delta patches of TOS (since 2266) are a bit larger and more pointy than those of the pilots; they are also highly reflective. We can see the delta on all standard uniforms, not on engineering jumpsuits or medical garments.
The delta can also be found on both the early and the later wrap-around shirt worn by Kirk, here placed horizontally. Christine Chapel's nurse uniform, unlike McCoy's, has a red cross as the central symbol, not the science pictogram. It is noticeable that during all of TOS, the delta never appears anywhere else but as this uniform patch - not on ship hulls, not on flags or seals, not on screens, not as wall or door decoration. And, more on a side note, the delta is nowhere seen in the TOS Mirror Universe in TOS: "Mirror, Mirror" - the upside-down "shield" version as in Discovery doesn't exist.
The Animated Series
The Animated Series overall faithfully reproduces the world of TOS - with some caveats as the drawing style and quality is concerned. We can see that the delta insignias of TAS are much more elongated and angular than in live action. They look like indented triangles or chevrons even in close shots.
Star Trek: The Motion Picture
Starting with the first feature film set in 2271, the delta gradually appears in more places. It still serves as a chest insignia for the Enterprise crew, now usually supplemented with a ring around the central shape. On the embroidered patch, this ring is filled with one of the new department colors. But we can also see the delta as a solid metal badge, as on Admiral Kirk's uniform. No patch appears on the field jackets. One other new symbol introduced for "Star Trek: The Motion Picture" is the medical emblem. It can be seen on McCoy's and Chapel's white medical tunics instead of a delta.
Several Starfleet personnel in the air tram station at the beginning of "Star Trek: The Motion Picture" can be seen with the delta insignia. But we can still pretend at this point that they are all Enterprise crew members, although this seems unlikely.
The delta now prominently appears on the hull of the Enterprise after the refit, replacing the "boomerang" emblem. In the TOS movies, the delta is consistently seen with the same inner symbol, the one that used to represent the command department at the time of TOS. The ship hulls are the exceptions and show, on a round red disk, an empty white delta, for the first time anywhere.
Later TOS Movies
"Star Trek: The Wrath of Khan" takes place in 2285 and brings a completely new uniform style, and different delta insignias along with it. They are metal badges like Kirk's from the first movie, and usually placed on a white field when worn with the "Monster Maroon" uniform jackets. They appear standalone on cadets' uniforms (which are also used by enlisted personnel) and on Saavik's loose-fit shirt. Khan famously wears a broken delta emblem as necklace on his exposed chest, which is anachronistic because he was exiled well before this insignia was first seen. Engineering suits like Peter Preston's have the insignia on the left shoulder, still following the color pattern established in the previous movie.
Technically, "Star Trek: The Wrath of Khan", is the first movie that requires the interpretation that the delta represents another ship just as well, namely of the USS Reliant (on the crew's uniforms as well as on the ship's hull). "Star Trek III: The Search for Spock" adds the Excelsior and the Grissom in this regard and firmly establishes that the delta is the insignia of Starfleet (or at least, of Starfleet ships).
Sulu's tea cup in "Star Trek: The Undiscovered Country" may be the first instance of an ordinary item with a Starfleet logo. We will see many more of such Starfleet brandings in the 24th century and in the reboots and other Trek series since 2017. The same movie also shows us a large Starfleet Headquarters wall emblem, the first of its kind, but here just with lettering and still without any other elements besides the delta on a round shield. What's more, we can see windows or light panels with the Starfleet delta, the way it appears on ship hulls. It is possible that the sixth movie was influenced in this regard by the style of TNG, which was being produced in parallel.
The Next Generation
Since the time of TNG, the Starfleet delta insignia doubles as a communicator. It is made of metal or of a similar solid material, with a silver delta on a now oval golden ground, and it looks identical for all Starfleet personnel. Only Wesley gets an all-silver badge in his role as acting ensign in TNG: "The Child". It is also notable that the inner (former "command") symbol is gone now. Uniforms on the Enterprise change in season 3 (2366), but communicators remain the same.
Delta symbols on starship or shuttle hulls are now on oval ground like on the uniforms, while the colors are still white on red as in the TOS movies.
The delta is placed on the dedication plaque of the Enterprise (and of many ships that will follow). In TNG, Starfleet logos increasingly appear on door labels, as well as on various pieces of cargo or equipment. Also, they are prominently seen in the insets of the doors of Ten Forward since TNG: "The Child".
The Starfleet delta occasionally shows up on monitors from now, but usually not as prominently as the Federation seal, which traditionally appears at the end of a video call. Furthermore, the Starfleet Academy emblem first seen in TNG: "The First Duty" includes the Starfleet delta.
Future Starfleet as shown in TNG: "Future Imperfect" uses a communicator that combines the delta with the rank insignia. Curiously the exact same style as in this fake future will reappear in an actual quantum reality in TNG: "Parallels". Vice versa, we see Starfleet deltas from the past in a couple of TNG episodes, but none of the are new.
Another communicator from a possible future will be introduced in TNG: "All Good Things" and reappear in DS9: "The Visitor", VOY: "Timeless" and VOY: "Endgame". A similar design will ultimately appear in the "real" future of Star Trek Picard.
Deep Space Nine
In DS9, the Starfleet delta remains almost as prominent as it used to be in TNG, although the series is set on a space station of Cardassian design. Commbadges are nearly as common a sight. While the DS9 uniforms are a different pattern from the beginning, the communicators are initially the same as in TNG. The switch to a delta on a hollow rounded rectangle comes at the beginning of season 3, set in 2371. At the same time on the Enterprise-D in "Star Trek Generations", the new commbadge is introduced while some of the crew are still wearing the uniform style from the TV series, just as Worf when he arrives on the station in DS9: "The Way of the Warrior". The dress uniforms remain the same anyway. All uniforms on Deep Space 9 (and in all of Starfleet) change yet again after "Star Trek: First Contact", but the second commbadge remains in use until the end of the series.
The cadets of Red Squad wear a special extra insignia on their uniform, which is composed of a large command symbol on a delta shield, both sideways.
DS9 notably introduces the Starfleet Command seal, which consists of the delta symbol with an additional "swoosh" or stylized spacecraft trajectory and which can be seen in many variations in DS9, Voyager and later shows. It is visible as a fully colored seal, standalone and on flags, as a belt buckle as well as in a variety of simplifications.
The door labels on the Defiant sport the Starfleet delta. It can also be found on coffee mugs used aboard the ship. Most newly created deltas have the rounded rectangle background, just like the commbadge. This also applies to dedication plaques.
The Defiant crew travels back in time and gets carefully reconstructed TOS uniforms to blend in in DS9: "Trials and Tribble-ations".
In the course of DS9, the use of Starfleet symbols on screens significantly increases, often on tactical displays. The Dominion/Cardassian enemy forces sometimes use the Federation seal and sometimes the Starfleet delta for the tactical planning.
Voyager
Voyager's commbadges, just like the uniforms on the ship, remain the same throughout the series, starting in 2371 when the model is brand new. They are worn by the regular crew, but also by all adult guests, such as Neelix, Kes or Seven of Nine. No new delta insignias are introduced in the show. But speaking of a "new" variation, there are the hilariously enlarged commbadges of the impostors in VOY: "Live Fast and Prosper".
USS Voyager, the shuttles and the Delta Flyer sport a new variation of the Starfleet delta on their hulls, which is introduced at the same time on the Defiant too and later seen on other Starfleet ships. It is yellow now, without a round outline.
We can see familiar forms of the delta from the past, such as the badge from the TOS movies. But there is also one from the future. The temporal agents from the 29th century can be seen with deltas that are sideways. Henry Starling's Chronowerx logo is based on this design.
Like DS9, Voyager also shows some varieties of the Starfleet Command seal, which can be seen on different flags, as a building emblem and on glass panes.
The eponymous probe in the episode "Friendship One" from the 21st century sports an anachronistic delta symbol.
TNG Movies
"Star Trek: Generations" (2371) comes with the aforementioned uniform chaos, but consistently uses the new commbadge as on DS9. We can also see signage with the delta symbol in some places.
As already mentioned, "First Contact" (2373) introduces new uniforms but doesn't change the commbadge. We can see a personal tea cup with the delta insignia in the movie. Also, the door labels on the Enterprise-E include this symbol. "Insurrection" and "Nemesis" show more labels with the Starfleet delta. The latter movie also has one of the few instances of the delta as a central symbol on a monitor, where usually the Federation seal would be placed.
Enterprise
There are no delta insignias in Star Trek Enterprise, which predates the creation of the Federation, with the obvious exception of "These Are The Voyages".
Abramsverse
Due to the setting in a parallel universe (and in an unclaimed past in the prelude), "Star Trek (2009)" is free to introduce all-new emblems. The Starfleet chest insignias comes in many variations, sometimes solid, sometimes embroidered and sometimes just printed. The badges of the Enterprise crew feature central department symbols, inspired by those in TOS and including the red cross. The uniform style is similar too, yet branded with small deltas all over in the first two movies. This overdecoration was abandoned for "Star Trek Beyond".
The field uniform jackets have a shoulder patch with the delta and additional writing: "Starfleet - United Federation of Planets". The gray dress uniforms, as seen on two occasions in "Star Trek Into Darkness", sport different chest emblems. The hats that belong to this uniform are a unique oddity in the Star Trek Universe, and the delta badges on them are unusual as well, as they are supplemented with two "wings". The deltas on the Franklin uniforms in "Star Trek Beyond" are the earliest use as a Starfleet insignia in the known chronology.
Delta symbols can be seen on the communicators, on different kinds of signage, on dedication plaques (including the one the Franklin that predates the timeline split) and on items of daily use.
"Star Trek (2009)" also shows a variation of the Starfleet Command emblem, as is barely visible at two points in the movie.
Discovery and Short Treks
We can see a completely new style of uniforms than in TOS in the first season of Discovery (2256/57), as well as new delta emblems. They are metal badges now, they come with insets in analogy to those of TOS, but they have an edge that runs straight down, splitting the insignia into two levels. Ranks insignias are integrated as pips. Tilly's cadet badge has no pips but is placed on a rectangular field. Admiral uniforms come with an additional laurel around the badge. Section 31 infamously uses a black badge. The delta definitely represents the whole of Starfleet. The "new" and more TOS-like Enterprise uniform, as first seen in DIS: "Brother", comes with an even badge, without an edge running though it: It is similar in shape to the classic patches from "Where No Man Has Gone Before".
The arguably biggest delta of the series is the one that Georgiou and Burnham walk into the sand in "The Vulcan Hello".
We can see the Starfleet Command seal, in a familiar variation that supplements the delta with a swoosh and with writing, very often in Discovery and in modern Trek as a whole. It frequently appears on shuttle hulls, on equipment, on some uniforms as a shoulder patch, on viewscreens - and on caskets. The same pattern is also used to represent individual ships, often in a simplified black&white style. The most prominent use of the ship seal is in the Discovery's huge shuttlebay, colored on the wall and monochrome on the floor. There is also such a seal on the sickbay floor.
Discovery introduces the previously unseen inverted delta shield as a symbol that supplements the "sword through Earth" insignia of the Terran Empire. This insignia reappears on the ISS Enterprise in DIS: "Mirrors".
32nd century Starfleet badges still use the delta shape, embedded in an overall oval device that doubles as a personal transporter. It still (or again) incorporates the dividing line that runs straight down the symbol.
As the ship gets upgraded to 32nd century standards, the Discovery also receives ship emblems in the new style, still with a hint of the swoosh. But the large floor emblem in the shuttlebay remains the same. Overall, the delta appears somewhat less frequently in the 32nd century than in Discovery's version of the 23rd century. When it does, it is mostly the simplified Starfleet Command or ship seal.
Picard
Star Trek Picard notably introduces late-24th and early 25th century Starfleet uniforms and insignias. As already mentioned in the entry for TNG, the future insignia first seen in "All Good Things" is used for real now. Well, the shapes of the two stripes forming the base of the badge are somewhat different, and they are not golden but gray. Interestingly, in the season finale PIC: "The Last Generation", this color is switched to gold, perhaps to look more like on the "classic" future insignia.
Overall, the first two seasons don't show many Starfleet badges due to the setting of the show. But there are two special variations. When Picard visits Starfleet Headquarters in PIC: "Maps and Legends", he is given a visitor badge with a delta-shaped cutout. In seasons 2 and 3, Picard is reinstated and can be seen with a small delta emblem when off-duty.
In the flashbacks of PIC: "The End is the Beginning", we can see that the badge first seen in 2371 is still in use in the year 2385. This familiar variant also shows up in the illusions in PIC: "Monsters". Picard keeps an even older TNG-era communicator in a box, which beeps in PIC: "The Next Generation". We can see the same variation on the dedication plaque on the bridge of the salvaged Enterprise-D in "Vox".
The Starfleet Command emblem used in Picard resembles the one of Discovery, with its split delta shield. We can see it on various occasions, especially in seasons 1 and 2, on monitors, as wall or floor decorations or on the flag in PIC: "The Star Gazer".
We can see delta symbols mostly on monitors, also on door labels and occasionally as decoration.
In Q's "Confederation", a more angular delta badge replaces the familiar one of the Federation Starfleet.
Lower Decks
Delta badges in Lower Decks are simply white with a black outline. We will see the live-action interpretation in SNW: "Those Old Scientists". Aside from the badges, we can see the Starfleet emblem on spacesuits, PADDs, cargo crates and many other pieces of equipment, usually as a simple delta without any other elements. The most notable appearance of such a simple insignia is in the shuttlebay of the Cerritos and of other vessels.
Legacy uniforms and badges are seen on several occasions in the series. As the series is set around 2380, the "First Contact" commbadge is still in use and can be seen repeatedly. An old insignia on a disk appears on a transporter station and on the uniforms of Starbase 80 personnel. The "Boimler Effect" diploma is adorned by a vintage movie-era delta.
The delta also shows up in decorative form, such as on shoe soles, on Boimler's Tom Paris plate or in the bar on the Cerritos. The journalist Victoria Nuzé shows a Starfleet delta in the title card for her report "Starfleet's Shame".
The clearly memorable delta insignia of Lower Decks is Badgey, the holographic avatar created by Rutherford, and his clones such as Goodgey.
Prodigy
The Janeway hologram and, some time later, the young crew of the Protostar can be seen with comm badges that are unique to this ship. They have something like an inner arrow pointing down inside the usual delta shape. This pattern is also found on the ship emblem, as it is placed on the floor of the lobby.
The ordinary Starfleet officers as this time wear a commbadge similar to the ones in Picard seasons 1 and 2. But the base is golden and not gray from the start - they are exactly like the ones in TNG: "All Good Things" that otherwise don't exist in live action.
Simple Starfleet deltas can be seen on pieces of equipment. And there is one case of branding that just takes it too far. A Starfleet screwhead? Comes on!
Prodigy shows a variety of full and simplified Starfleet Command emblems. The full versions faithfully follow the transition from DS9 style to PIC style in live action.
Classic insignias can be seen at various points, including TNG-style communicators (but on copper ground?) and the TOS patch.
Strange New Worlds
Strange New Worlds continues where Discovery left after season 2 in 2259 - continuity-wise and style-wise. Well, the uniforms are new yet again, but the delta badges, including the department symbols, are familiar. Only the red cross of medical personnel appears to be gone.
Admiral April's badge is adorned by an additional laurel. "A Quality of Mercy" shows us a reimagination of the patch that Hansen wore in TOS: "Balance of Terror". The same episode also has a slight redesign of the "Monster Maroon" uniform with the according insignia.
Spock's badge on the alleged "standard issue hat" in "Charades" is odd because it is sideways. On all other variations, the thicker part is on the left.
Strange New Worlds continues to show the Starfleet Command seal on many occasions, as well as the ship seal. The latter doesn't have a swoosh. Just like the SNW delta badges don't have the vertical edge, it is now missing on the Command seal as well - unlike in Picard. Whenever a delta appears on a big viewscreen or on a hand-held device (which happens very often in SNW), it is mostly this more elaborate seal, not the simple symbol.
A curious use of the delta symbol is the one created by the inhabitants of Rigel VII in "Among the Lotus Eaters". Decorative emblems can be seen on cups.
The real-life versions of Lower Decks commbadges can be seen in SNW: "Those Old Scientists". Vice versa, the episode also shows the SNW badges in animated form.
A strange mutation of the delta badge appears in the alternate reality of SNW: "Tomorrow and Tomorrow and Tomorrow". It does not have much in common with the delta but is mentioned for the sake of completion, just like the fictional patches from SNW: "A Space Adventure Hour".
Starfleet Academy
Starfleet's insignias in SFA are generally like in Discovery's 32nd century. The personnel of Starfleet Academy can be seen with special badges, whose delta is placed on an outline of the USS Athena. Cadets also have such badges, but with a printed on delta. Don't swallow it! The War College uses a different badge, consisting of a delta and a swoosh. Protective suits feature lighted or florescent insignias.
The series notably introduces a new Starfleet Academy emblem, which simply consists of the Starfleet delta, without the Golden Gate Bridge. The round Academy seal is often combined with a shape that looks like an inverted "U" and that resembles the planform of the USS Athena, just like the commbadges of the Academy. Both the Academy seal and the War College seal can be seen on flags too.
Decorative deltas can be found in numerous places at Starfleet Academy, such as on walls, floors, pillars, chairs, desks or screens. They range from highly stylized deltas to variations of the Academy emblem.
Enterprise vs. Fleetwide Usage
At outlined in the above history, all crew members of the original USS Enterprise NCC-1701 consistently wear a delta emblem on their uniforms, with an inner symbol denoting the ship's department they belong to (command, science, operations). This is true in a time frame from at least 2254 ("The Cage") to 2268 (the end of TOS). We my want to include TAS. Other TOS-era Starfleet personnel is usually seen with the same uniform style, colors and rank insignias, but with different chest patches. One of these other emblems resembles a flower. It is commonly associated with Starfleet Command. Chest insignias other than the delta and Starfleet Command can be seen in three TOS episodes, always worn by ship crew members: (U)SS Antares in TOS: "Charlie X", USS Constellation in TOS: "The Doomsday Machine", USS Exeter in TOS: "The Omega Glory". ENT: "In a Mirror Darkly" adds the emblem of the USS Defiant to the mix.
The USS Huron crew in TAS: "More Tribbles, More Troubles" can be seen with a different insignia as well. This would give us five appearances of (ship?) emblems other than the delta, three during TOS, and two more inspired by the diversity of TOS symbols.
For decades, it seemed to be set in stone that the delta represented specifically the Enterprise at the time of TOS, and that each starship (or at least, each of the twelve Starship/Constitution-class vessels) had its individual symbol. This used to be the commonly accepted explanation for the different emblems until 2017. And it was more or less official (albeit not canon) because the existence of individual ship emblems was confirmed in all editions of the Star Trek Encyclopedia.
In all uniform styles since "Star Trek: The Motion Picture" (2271), all of Starfleet's personnel consistently wears the delta (in many slight variations). We can still see the personnel of the Epsilon IX station with an individual chest emblem in 2271, so the transition may not have been abrupt, though. Anyway, if the delta previously was the symbol of the Enterprise, there are two possibilities: Either the famous voyages of the Starship Enterprise have inspired Starfleet to adopt the ship's individual symbol for the whole organization, or the delta had been a common identification symbol of Starfleet already prior to TOS, and was worn exclusively on the Enterprise only for that limited period - maybe because the Enterprise was the fleet's flagship or was considered something otherwise special. The latter is supported by the appearance of the delta as soon as on the Friendship One UESPA probe.
An article published at startrek.com in 2017 sheds new light on this very old issue. In a memorandum from December 18, 1967, Bob Justman, on behalf of Gene Roddenberry, stated that the delta is meant to be the common insignia of all starship crews. The crew of the Antares, which were already seen with a different emblem at the time of the memo, are members of the merchant marine and "not entitled to bear this proud insignia". We can make the same case for the USS Huron emblem that was created later and is not mentioned in the article. The memo purportedly came too late to prevent William Ware Theiss from creating different insignias for Commodore Decker (USS Constellation) and still for Captain Tracey and Dr. Carter (USS Exeter). "The Omega Glory" was just being filmed at the date of the document.
While behind-the-scenes information like Justman's memo would be overruled by canon evidence, it is worthwhile to review the delta issue in light of the idea of a common starship crew emblem. In fact, we could see non-Enterprise starship personnel with delta insignias on two occasions in TOS: two Starfleet officers who are not in Kirk's crew in the Starbase club in "Court Martial" (possibly more, but only these two implicitly identify themselves as being from another ship) and bodies of Defiant crewmen in "The Tholian Web". These would support the theory that all starship personnel wear the delta insignia. Since we never see any of his crew (because they have left the ship and are all dead by the time), we may explain Commodore Decker's different emblem with him being a flag officer with a permanent field commission. This makes Tracey and Carter the only anomalies at the time of TOS, because why should just these two have a different insignia than the rest of their dead crew that we never see? Overall, it seems like the lesser evil to go with the conclusion of the startrek.com article and accept the two Exeter officers with their non-standard emblem as an exception, so the crew members in the Starbase club and on the Defiant would wear a regular emblem.
If we take into account ENT: "In a Mirror, Darkly", however, the situation is different. The assumption that the delta is the universal starship symbol now produces quite a few more exceptions to the rule. The startrek.com article discreetly ignores the Enterprise episode (maybe because it is based on "false" suppositions). But even though ENT: "In a Mirror, Darkly" episode disregards the rule that Roddenberry and Justman made up (or rather, was made without any knowledge of the obscure document), it is fully canon and has definitely more weight than the meanwhile resurfaced memo.
The crew of the Kelvin can be seen wearing the Starfleet delta on their uniforms as soon as in 2233. Therefore it is still a possibility in the Abramsverse that the delta represented all crews of Starfleet before it became a special symbol of the Enterprise for a limited time in the 2260s.
As shown in detail in the history above, Star Trek Discovery and Strange New Worlds show all Starfleet personnel exclusively with the Starfleet delta in the 23rd century, now apparently with the more or less official blessing from the startrek.com article that something like individual ship emblems never existed. It doesn't seem to be a coincidence that the article was published right after the launch of Discovery in 2017.
Addendum
Pre-Federation usage
It is interesting to note that the long-range probe Friendship One (UESPA-1) in the Voyager episode of the same name sports the delta, here as the symbol of the UESPA (United Earth Space Probe Agency), as early as in 2067. But Earth Starfleet has apparently abandoned or has never used the delta symbol by 2143, as we can see a somewhat different, NASA-like Starfleet Command symbol, perhaps symbolizing a spacecraft trajectory, in ENT: "First Flight" and in other episodes taking place between 2151 and 2155. ENT: "Demons" finally showed a seal with this Starfleet symbol and the additional words "United Earth Space Probe Agency", implying that Starfleet Command is a part of UESPA. If both organizations are the same or one is a department of the other, it is only plausible that symbols are interchangeable and that at a later date the delta could come into use again - even if the UESPA was renamed, demerged or abandoned some time between ENT and TOS.
The "boomerang" symbol
The "boomerang" symbol can be seen as the pennant on Federation Starfleet ships at the time of TOS, such as the USS Enterprise NCC-1701. The symbol is also visible as a wall decoration in the courtroom in TOS: "Court Martial". A more angular boomerang appears as the individual ship emblem of the USS Defiant NCC-1764 in ENT: "In a Mirror, Darkly". It is unknown what the boomerang signifies. It looks a bit like the Starfleet delta. Considering that the Starfleet delta is turned by 90 degrees when displayed on ship hulls (since 2271) or on Kirk's first-season wrap-around uniform (2265), just like the boomerang, it is well possible that the boomerang is an alternative Starfleet emblem - but one that was abandoned, perhaps because it looked so crude.
A modified boomerang reappears on the pennant of the (U.)S.S. Raven NAR-32450 in VOY: "Dark Frontier", here denoting either a civilian ship registered in the Federation or a Starfleet science ship, depending on which of the two conflicting prefixes that were mentioned, SS or USS, we lend more credence.
The boomerang, rather than the delta, also appears on the reboot Enterprise in DIS and SNW. Unlike the proportions of the ship itself, this detail was faithfully reproduced and not retconned to comply with the insignia seen on later ships.
See Also
The Changing Styles of Starfleet Uniforms - keeping track of the many changes and the resulting problems
Starfleet Uniform & Rank Issues - mismatched rank insignias, odd uniform choices and bloopers like missing pips
Other History Inconsistencies - about the TOS movie timeline, the UESPA, first contact with the Borg, Klingons in the Federation, etc.
Credits
Many screen caps from TrekCore and from Cygnus-X1.net.
