Watching Star Trek I've observed that phasers and photon torpedos are used interchangeably, often seemingly at random. I know that writers probably didn't think/care but I look for explanations in-universe.

The presence of two weapons in single vehicle is usually justified by different targets and uses, say a machine gun for soft targets (infantry) and a main gun for hard ones (other tanks). Otherwise it only increase problems (incompatible ammunition, increased maintenance cost etc.).

So what are the differences between those two?

13 Answers 13


One is energy-based (phasers) and the other is matter-based (torpedoes) with an explosive yield. I remember reading once that it in a confrontational situation, the phasers would typically be used to weaken another ship's shields and then the torpedoes would finish the target off.
Also the phasers were used more to disable ships than to destroy them, as they could target more precisely.

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    Yes. Don't forget the main purpose of the deflector shield, to deflect objects out of the path of the ship while it's traveling. (you wouldn't want a pebble hitting the hull at warp 7, it would go right through the ship) A torpedo would certainly be stopped by the shield if phasers didn't weaken it first. – Jonny Blaze Jan 19 '11 at 20:09
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    @Jonny Blaze: This is only partially true. While wasteful, Torpedoes can be and are used to bring down shields. Presumably by detonating before impacting the shield. The destructive force of the Torpedo is energy too. – DampeS8N Jan 21 '11 at 20:01
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    This was probably the original intent of the authors, but it has likely been weakened by writers who failed to keep it in mind, or had to change it to fit their story. – Jeff Feb 3 '11 at 22:58
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    It should also be noted that phaser are particle beam weapons, and as such the "energy ray" could be considered an object. Though, as shown in many episodes, the nadion particles are not merely particles with high kinetic energy, since they possess a kind of "built in intelligence". It is for example perfectly possible to set a phaser to "evaporate" and have the nadions engulf an object or body, disintegrating it fully without harming the environment as much as leaving a scorch mark (even when destroying a Riker-sized clone inside a tight glass tub). – dm.skt Feb 27 '11 at 16:21
  • Good simple summary of the differences. – PCSgtL Jun 29 '16 at 15:10

According to the Technical Manual phasers are constrained to the speed of light so are of less use in confrontations that are taking place under warp drive. Photon torpedoes have warp capability (though not full warp drives) and so can go faster than light speed and engages ships also doing so.

Also photon torpedoes can be used as mines which phasers can not.

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    To be clear, they can maintain a warp bubble but can't create one. Once they fall out of warp, they can only then reenter it by being fired again. – DampeS8N Jan 21 '11 at 20:02
  • In ST:TMP, the use of phasers to destroy an asteroid in the path of a wormhole created by the Entrerprise's malfunctioning warp drive was ordered, then belayed only because the phasers drew power from the warp core, not because they were constrained to light speed. – KeithS Nov 1 '11 at 15:27

I suspect there is a desire on the part of the writers to have an analogy to pre aircraftcarrier battleship fighting. Phasers are like deck guns, and torpedos, are like their namesake. One has longer range, and is quicker to aim, and the other is slower, but does more damage. Most spacewar stuff, wants to reenact war world two battles, either naval, or bombers versus fighter planes.

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    Roddenberry was a WWII vet, having flown a lot of missions in the Pacific. The episode "Balance of Terror" was firmly based on WWII anti-submarine warfare. – David Thornley Jan 22 '11 at 15:37

Phasers and torpedoes are, as was mentioned, much like deck guns and torpedoes in WWII-era naval warfare. The idea of the Klingon and Romulan warbirds being able to cloak and thus be hidden was a direct analog to the German U-boats.

Tactically speaking, you want as many types of weapons as you can get when you're in a fight. This applies virtually across the board, in all situations. If one weapon doesn't suit the situation, you bring another. It's why police officers don't just have guns, but batons, tasers and pepper spray as well.

Back in-universe, phasers are the go-to weapon. Phasers are energy-based, meaning as long as you have sufficient power you can continue to fire them. They are very powerful against most unshielded targets, and can be brought to bear from nearly 360 degrees (provided all phaser banks are operating nominally). Lastly, being a beam, they can usually be aimed and fired pretty quickly at a target at almost any renge at which the weapon is effective (even right up close). However, depending on the race's level of technological advancement, phasers often have minimal effect on shields or even ship hulls. They are also limited by the speed of light, so they cannot be used while travelling at warp.

Torpedoes are the Star Trek equivalent to the same weapons in naval combat, or to anti-ship missiles like the Harpoon or Exocet. Get hit with one of these with your shields down and your ship has a big gaping hole in it. The explosion also requires a lot of shield power to repel and can cause damage even with shields up. They also require minimal power to fire, making them the principal weapon of cloaked ships like the Klingon Bird of Prey, and they can be used while the ship is travelling at warp, as they maintain a "warp bubble" generated by the firing ship. However, they are an expendable weapon; it is implied that torpedoes are too complex a machine to replicate, even without their antimatter payload. They are also, for the most-part, non-seeking; they must be given their initial guidance from the firing ship, and if the "sight picture" changes (the ship radically changes course or speed) the torpedo can miss. Torps have a maximum rate of turn and come out of the launcher along the fore-to-aft axis of most ships in the universe (there are a few turreted launchers such as the ones mounted on DS9), meaning their effectiveness in a "broadside" confrontation is reduced. This makes torpedoes a weapon you use in head-on combat when you are pretty confident that you will hit your target, usually meaning relatively close range.


Another good reason to use them differently is that torpedoes can track a target where as a phaser is fired directly. If it misses, it misses. If you recall, one of the movies, a Klingon ship is cloaked but leaking particles (photons was it?) and they modified a torpedo to run the particles down to the source to kill the ship.

  • It was Undiscovered Country. – Maciej Piechotka Feb 23 '11 at 23:12
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    Most torpedoes in the Star Trek universe however are not "seekers"; they work more like unguided torpedoes (from the WWII era), where you can set the "trim" of the torpedo's fins so it follows a curved path to the target. That means you don't have to be pointed right at your target, but it also means that a target rapidly changing course or velocity can cause a torpedo to miss, because it's set to intercept a target traveling on a constant course and speed. – KeithS Nov 1 '11 at 15:31

It is mentioned several times in Voyager that photon torpedoes are irreplaceable. Although fans have counted the number of photon torpedoes fired throughout the entire series and found it to be much higher than the number given explicitly in one of the first episodes, it nonetheless provides an in-universe reason not to want to waste them.

  • In ST:Nemesis the Enterprise exhausts its entire complement in a single (though long) battle. – Chad Levy Nov 1 '11 at 19:08
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    Torpedoes in general are replaceable. Voyager didn't have the facilities to build replacement torpedoes on board. In the episode Dreadnought, they talked about adapting the torpedoes on the super missile to replace what they had used. In the Alpha Quadrant, a Starfleet ship could restock its torpedo compliment anytime. – geewhiz Jan 5 '15 at 1:41
  • To clarify, starships in general, don't construct torpedoes on board-not just Voyager. – geewhiz Jan 5 '15 at 1:47

I know this a technical discussion about different capabilities, but phasers have become progressivly less powerful as the series progressed from Star Trek to Voyager. In the original series, where the plots were written by classic sf writers from the golden age of sf, and as such were dense with new sf concepts, there is some discussion about how vastly powerful they are. I don't know the episode, but it is about two humans who crash landed and were badly damaged and the aliens allow them to be viewed as complete and unbroken.

In that episode, they need to break into the underground fortress (it was the episode with the lift underground); they use a tripod phaser, which is really powerful. They say that it 'should have blown the hill in seconds' even though the telepathic aliens are generating an image in the crew's minds of an unbroken hill at that point.

The point is, Kirk discusses firing the phasers from space, but they're worried (if you read the script) that the phasers are going to really destroy everything, cutting into the planet down to the core, and even destroying it, cutting it in half. Those were super power cutting beams that are vastly powerful, unimaginably fed by antimatter engines.

Contrast that by the time of Voyager. Phasers can't even penetrate shielded hulls or borg. I know I'm harping, but comparatively, if the Enteprise met the Borg, they would slice the cube into bits.

The whole progression of the series has softened it from a sf series into a script with spaces for sf words. Choose a word.

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    Honestly, they probably realized "Oops, that's ridiculously and unrealistically overpowered. Maybe we should retcon that..." It wouldn't be the first time. – Daniel Bingham Jan 20 '11 at 16:57
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    All that came to my mind with such plot (I haven't watch whole TNG and DS9 and I haven't seen any episode of VOY and ENT) is Cage. – Maciej Piechotka Jan 20 '11 at 19:48
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    @MaciejPiechotka I have seen all of every series, and The Cage / The Menagerie is all that comes to mind. The Cage was the original, unused pilot of TOS, that footage was reused for in The Menagerie, and contains -tons- of inconsistencies with the rest of TOS. – Izkata Nov 29 '11 at 13:39

Photon torpedoes came along late in the first season of Trek. If you remember BALANCE OF TERROR, the phasers were fired using "proximity blasts;" these probably led to the writers coming up with a different sounding weapon that lent believability to the show. The torpedoes seemed harder to hit a target with, but apparently were capable of diabling/destroying another vessel with just a few hits. It also seemed many writers were apparently unaware of the photon torpedoes--in the DOOMSDAY MACHINE, phasers were used exclusively where torpedoes might have proven more effective without having Decker & the Constellation sacrificed. Both weapons had the coolest sound effects audible from the bridge when firing.

  • re "late in the first season" -- specifically, searching chakoteya.net/StarTrek with "photon torpedoes" showed that in terms of production order, "Arena" was the first episode where they were mentioned, used they tried to hit an attacking ship with phasers but the phasers were "Negative against its deflector screen." – Hypnosifl Jun 29 '16 at 15:22

I’m surprised no one has discussed this from a ‘Star Fleet Battles’ perspective. This is the board game/miniatures system designed to handle these very things.

Phasers are ideal as short to medium range weapons (all but the heaviest do no appreciable damage at distance).

  1. They have some of the best accuracy of all weapon systems in universe.

  2. They have a low energy usage so they can keep firing even after the ship and its power sources (engines and batteries) have been significantly damaged.

  3. Their low energy usage and small general size allow for multiple phaser banks to run on a ship.

    a. This gives the potential to have a larger effective firing arc (the Gorn where exceptional at building ships that where deadly from every angle)

    b. and also means that multiple locations must be targeted by the enemy to disable the multiple locations where they are located.

  4. They also have a relatively quick recharge/reload time.
    a. This lets a few phasers to be fired without significantly reducing the Alpha Strike capability.

  5. They can be used defensively.

    a. Phasers are often used as anti missile weapons.

    b. Phasers are ideal for taking out strike craft/shuttle craft/fighters and mines. (Some phaser banks [Phaser G’s if memory serves] where specifically designed for this role)

A well designed and maneuverable ship controlled by a deft captain and crew could let out a continuous fire of Phasers by rotating their ship and corkscrewing around their opponents path while constantly rotating the shields presented their foe.

Photon torpedoes are designed as long range weapons however they use a tone of energy.

  1. They have one of the longest ranges in universe.

  2. They are heavy hitting, dealing significant damage at any range.

  3. They can be modified to fire even longer ranges as a proximity weapon. Decreased damage but it does increase accuracy and range)

  4. They are not vulnerable to the anti missile fire of phasers (nor can they be tractored away from the target).

  5. When they hit they frequently deal damage to multiple systems at once causing ship wide failures.

  6. They serve as an extension to the ship in the numerous ways they can be modified for none combat use.

A well designed and fast ship could stay out of range of the enemy and let out a slow but steady barrage of photon torpedoes. Forcing the enemy ships to flee or be destroyed without dealing any return damage.

The Federation had a philosophy of multipurpose ships. So few ships where set up to focus on either activity, however this set up allowed nearly every ship to have options in any situation.

Alpha Strike

The alpha strike is the concept of charging all a ships weapons and then waiting until point blank range and unleashing them all at once or in quick succession. For a Federation ship to manage this full charge they often needed to reduce their maximum speed or run the risk of damaging their engines. A well executed Alpha Strike could strip a shield sector by using all phasers, and then unload overloaded photon torpedoes (adjusted to increase damage but decrease accuracy) through that downed shield and destroy or cripple most ships of similar class.

Lead with photon torpedoes to take out almost all shields, and then unleash targeted phasers and you could cripple a ship with precision, cutting out warp drives or weapons, but keeping ship, crew and contents intact.

Power Usage

Everything ever ordered on the show takes energy. A ship does not have the energy to do everything at once. So these must be balanced based upon the tactical situation.

Speed: Faster speed means less power for other systems.

Raising Shields: Done at yellow alert

Reinforce Shields: Often seen in shows, this diverts extra energy to a specific section of the shields. You could sink all your energy into this. It makes that shield facing slightly stronger.

Deep Space Scans/Scanning Enemy Ships: Gets you extra information at the cost of energy.

Charging Weapons: Base charge. (between shields and speed the three biggest power sinks)

Specialty weapons: This is usually overcharging weapons for more range or power.

Charging Transporters: Land troops, extract personnel, or drop mines ect,

Preparing Shuttlecraft: Once launched they run on their own, but it takes energy to get them their.

Charging/Launching Probes: Can be used to scan the enemy or converted to deal extra weapon damage.

Warp Drive: Want to escape/run away? Even though the warp core supplies energy to the ship it still requires a certain amount of energy to get you out too.

Tractor Beam: Usefull in all sorts of military maneuvers.

Electronic Warefare: Used to increase your chance to hit, or to decrease the enemies chance to hit you, if you have the energy.

No ship in universe has the power to do everything at once. I hope this provides a useful guide to the specific tactical uses of both phasers and photon torpedoes.

  • The problem with SFB is that it exists outside of everything Star Trek since TOS. It doesn't take into account anything from any movie or show since, and the two universes have diverged SIGNIFICANTLY. Sure is fun though! (well, I prefer the Starmada or Fed Commander versions). – Jason K Jun 29 '16 at 16:27
  • Historically the verge yes, but the mechanical foundations of the interactions of weapon systems are the same. – PCSgtL Jun 29 '16 at 16:32

Phasers are much more effective against shields than torpedoes are. If against a ship's shields a phaser hit and a torpedo hit do about the same damage, wouldn't you rather use the one you can keep spamming?

In the first Star Trek reboot (2009), during the kobayashi-maru simulation Kirk targeted the enemy ships with torpedoes, knowing that their shields were down because of a hack he put in the program.

The shield absorbs, blocks, and reflects most of the energy and redistributes it across its whole. If any energy gets through then its something the shield normally wouldnt block anyway (eg, certain kinds of radiation, and shots which are modulated to bypass and match the shield's frequency). Any damage the ship takes from a hit to the shields is probably buffeting from the Shield pushing on the Shield Emitters which then transfers some of that energy into the ship superstructure (sorta like blunt force trauma on a ship level).

Against an un-shielded ship, Phasers do decent damage to a ship by themselves but a Torpedo hits so strong it can severely cripple or destroy the ship in one shot. Of course this depends on the size of the ship - A Borg Assimilation Cube is 6000 meters size per side, and it regenerates, but at least it doesn't have shields.

(though it makes me wonder why not just make the Warp Capable Torpedoes hit the borg ship At Warp Speed or something close to C... then the explosive power of it pales in comparison to the kinetic striking power. But oh well).

Torpedoes can also be useful if you're having problems hitting the target, but I think using the torpedoes in this way is unrealistic and was used for theatric performance in the show. The idea of firing a spread of torpedoes would be to get at least one of the torpedoes close enough to the offender so that it gets hit with an energy-shockwave.

But... if it can take more than one shot to blow up a de-shielded ship on a Direct Hit (or even with an internal explosion in some cases) then we aren't exactly talking about NUCLEAR YIELDS here, contrary to what some star trek theorists claim.

If a torpedo is listed as having a 25 Isoton Yield then im saying thats probably more like 25 Tons of modern High Explosives. Thats like 10 modern day cruise missiles in one hit, and the torpedo itself is a fraction of its size. An admirably strong weapon for a warhead you can probably carry in a suitcase. But its not a briefcase nuke by any measure. Its somewhere in that gray area between conventional explosives and nuclear.

Yes it might use antimatter, but the amount of it is miniscule or even molecular, contained in a number of little magnetic bottles "cells", which it ends up reacting with (1:1 ratio matter decomposition) whenever they get broken. Personally i'd think the amounts involved would be extremely small, for safety reasons, so that the containment modules could be overbuilt to make sure that they dont lose containment or end up with a torpedo that explodes when you accelerate fire it out the torpedo launcher.

In which case the enormously powerful Quantum Torpedoes developed later on are each hitting with a strength comparable to a tactical nuke (300 Isotons = 300 Tons of TNT = abut 1/3 of a Kiloton).

Another reason I say torpedoes don't detonate in the nuclear range is because they've been used on planetary targets a bunch of times and they only cause localized damage, not a huge city-killing blast. If a torpedo can hit somewhere close by and not kill the away team, its most certainly not a nuclear weapon, not even in the kiloton range, much less in the megaton range.

  • Do you have canon references for all of the assertions made here? Thank you! – DVK-on-Ahch-To Apr 28 '14 at 20:56
  • Down vote due to canon reference. The shield dispersal is wrong. It's the weapon system that determines weather a specific facing of the shield is weakened or all of them. Not the shield itself. – PCSgtL Jun 29 '16 at 14:29

As it was noted, Phasers seem to be directed energy weapons. The technical manual gives a very low yield estimate for phasers on Galaxy class starship... but this number doesn't make any sense when contrasted to the photon torpedoes which are supposed to be carrying 1.5 kg of matter and 1.5 kg of antimatter - which would result in a 100% energy conversion of 64 megatons - though these figures were apparently stated for TOS/TMP, not TNG.

But, lets' estimate these figures ARE for TNG... in which case, a maximum output of 1.2 GW for phasers makes no sense since they end up being thousands of times less powerful vs torpedoes. Another estimate indicates that Phasers on the galaxy class (type X) were rated to be in the range of 100 000 TW of maximum fire output - which is approximately 23.9 megatons (every second).

The 100 000 TW for Type X phasers (from Season 1 to Season 3 for example of TNG) makes a lot more sense and leaves room for improvement in firepower output. Phasers can be more versatile as you can modify them on the fly in terms of frequencies and do all kinds of other useful things. Torpedoes can also seemingly be manipulated on the fly and are versatile as tools, but phasers have a larger pool of resources to draw from and aren't limited in quantity like photon torpedoes are.

Also, photon torpedoes make more sense to be more like shaped charges (which might explain away the inconsistencies in how the FX department decided to show them - incidentally, early Seasons of most 24th century shows seemed to display explosive dispersal pattern on planets more consistently with torpedoes compared to some others - hence the FX shouldn't be taken at face value all the time - it has to be contrasted with what seems reasonable in terms of numbers).

Torpedoes might be used for quickly bringing down enemy ships shields and using phasers for more precision/surgical strikes. Though, torpedoes can also be used for those, but I would imagine they run a risk of destroying ships if they hit particularly weak systems).

I would imagine that phaser power outputs were increased as time went on well beyond 100 000 TW though. Torpedoes would also increase in explosive yields, so its possible they managed to pack a lot more matter and anti-matter inside a torpedo for example, and have started switching over to quantum torpedoes due to having on average double the yield of photons... but in terms of energy delivery and precision, they might be much better than photons as well (plus, they might not use anti-matter at all - some sources suggest 0 point energy, but this isn't cannon - there just might be other properties to quantum torpedoes- perhaps more based on uncertainty principle inherent to qunatum mechanics which also yields better results than conventional photon torpedoes?).

It has been mentioned however that a 54 isoton explosion from a modified gravimetric torpedo (which is based on a photon torpedo design) is able to destroy a small planet, and this output was increased to 80 isotons). Voyager's photon torpedoes (which were type VI at the time) were mentioned by the Borg to have an explosive yield of 200 isotons.

This does make sense however, but SF would rarely if ever use these capabilities to actively destroy planets outright. Even the Romulans and the Cardassians when they formed an alliance and attacked Dominion supposed homeworld... the first barrage managed to destroy 30% of planetary crust in seconds (incidentally, the Enterprise-D was able to inflict similar planetary damage on its own), but this might have been more in line with seizing potential resources a planet might have after 'beheading' the Dominion of its 'leaders'. Even the Cardassians and Romulans might not be as 'reckless' to the point where they might want to simply destroy a whole planet. As violent as they might have been, neither were stupid. One could gleam valuable info from a planet of an opposing power or seize some interesting resources... or a number of different things.


My own thinking is that phasers require a lot of power but they have unlimited "ammo" so long as power is available. Torpedoes are limited in number but require little power to launch.

I also see torpedoes taking out a shield and then phasers being the threat that forces surrender.

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    Here at SFF.se, we prefer non-opinion based answers based on canon. Please edit this to give examples or proofs of what you are talking about. – CHEESE Aug 18 '16 at 19:43

The original series episode "a taste of Armageddon" shed some light on another difference between photon torpedoes vs phasers ,Photon torpedos can be fired when the deflector screens are totally up while phasers cannot be . As engineer Scott mentions that he is unable to fire his fully activated phaser banks due to the fact that the screens are up which protect them from the planetary disruptor banks that are being fired at the enterprise. He says in response to a question for Mccoy about possible offensive action almost verbatim Tha he could "still fire a half dozen photon torpedoes..." downon Aminiar. Because they are holding Captain Kirk and the rest of the boarding party hostage to try to force the enterprise crew to either be destroyed via a shot from the planet or tricked into transporting down the entire crew onto a Ainiar to be destroyed. "The taste of Armageddon," where two planets fight a war virtually -via computers and then the deaths recorded randomly in the area are assigned to people and those people have to enter a disintegration machine and basically kill themselves. It's actually one of the cooler episodes in the series in my opinion. I would put that episode up probably with my top 10-15 favorite episodes. Although, there are definitely a lot of great ones to pick through. Then The episode also brings up another question…there's the whole idea of disruptors( both handheld weapons like handheld phasers and planetary disruptor weapons strong enough to destroy the enterprise if it did not have it screens up. A random red shirt says something to the effect of " Sir, our screens weren't up we'd be totally disrupted!" Lol we now have the question of phasers vs disruptors. I'm using the iPad speech to text so I apologize in advance for any errors in grammar, words out of context, or spelling.

  • Welcome to the site Jeff Pierce. This answer is rather chatty, perhaps it would help if you had a quick peak at the tour. We do things a little differently here, we aren't really a forum or bulletin board. We're a Q&A site, it's just what we do. So it's important to make sure you answer the question and provide as many references as you can. Your own opinion of various episodes - whilst perfectly valid - is the kind of thing you really wanna trade out for quotes and references on this particular site. We take our sci-fi pretty seriously here, you see :p – Au101 Nov 26 '16 at 1:21
  • Well I could've definitely made the post shorter. I Edited to correct a few typos from my speech to text. However, I believe I added a direct quote that shows a distinct difference between phasers and photon torpedoes. I did include a quote directly from the episode a taste of Armageddon that says photon torpedoes can be fired while deflector shields are up. phasers cannot be fired and in that same to situation. It's clearly mentioned in the episode. I will leave out information about how it is one of my favorite episodes for example. If it's strictly information that needs posted. – Jeff Pierce Nov 26 '16 at 1:48
  • Thanks, I don't really know much about Star Trek so I won't comment further, but this definitely seems much more like the right kind of tone for this site. It can be hard to get the hang of Stackexchange, which is a bit different in the way it works. That's why they get us older members to take a quick look at new members' posts and see if we can't help them out :) Still, it's important to avoid chit chat. Think more serious Q&A, or encyclopaedia, that kind of thing - and less internet forum :) – Au101 Nov 26 '16 at 2:01

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