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Based on this question: Why did Luke need a targeting computer in the first place?

Proton Torpedoes launched from Luke's X-Wing were able to change direction 'on a dime' 90 degrees to get into Death Star's thermal exhaust shaft.

It seems intuitively obvious that the cause of that was technological (since Luke had nowhere near Force training at the time to be able to cause the turn).

Is there any sort of official Canon explanation for how the torpedoes turned?

E.g., was it some capability of torpedoes' propulsion? Forcefields from an X-Wing? Some interplay between a torpedo and Death Star's technology as TangoOversway's answer to that question alluded to being a possibility? Some other mechanism?

Please note that "programmed to turn in advance by X-Wing's targeting computer" is not an answer, as I'm looking specifically for what the mechanism for ability to execute the turn, NOT why the turn happened when it happened.

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    @OrigamiRobot - Not quite. Even assuming the torpedoes could turn, SOME mechanism for deciding when to turn was needed, and that was likely provided by targeting computer. My question was "HOW", not "why" (thanks for raising this, I have explicitly put "how" in the wording now) – DVK-on-Ahch-To Jan 5 '12 at 0:35
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    If the exhaust port is perpendicular to the surface of the Death Star, why not fly straight towards it instead of along the trench? – Jack B Nimble Jan 5 '12 at 17:18
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    @JackBNimble: Because the Death Star surface is covered in anti-fighter and anti-ship turrets, many near the exhaust port. Any fighter just charging head on would die. The value of the trench is that you can approach at the safest, least gun-covered point on the surface, then have only the few guns along the trench able to hit you on your way to the target. – Tynam Nov 12 '12 at 12:20
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    @KyleJones - Don't think so. The rebels expected the thing to be workable without knowing they have a powerful Jedi wannabe around. Luke used the force to guide his decision making process on how to move and when to fire, NOT to nudge the torpedos for which he was woefully undertrained (see his training with Yoda) – DVK-on-Ahch-To Apr 15 '13 at 18:52
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    Do they turn or do they fall? :) – Django Reinhardt Jan 12 '14 at 14:25

11 Answers 11

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+500

Short answer: They don't really "turn 90 degrees". Or rather, they probably weren't supposed to.

In the fourth draft (the one just prior to filming) of the script, Lucas gives us a hint about how he envisioned the Proton Torpedoes working:

                              DODONNA
                Your approach will not be easy.  You
                must maneuver straight in
                down this shaft, level off in the
                trench and skim the surface to this
                point.  The target is only two meters
                across.  It will take a very precise
                hit at exactly ninety degrees to get
                into the reactor system.  And only a
                direct hit will set up a chain
                reaction.  The shaft is ray shielded,
                so you'll have to use proton torpedoes.

I think by "ninety degrees" that Lucas was probably imagining that the pilot had to be directly above the exhaust port in order for it to drop go all the way down into the reactor. That might make sense when you're writing something, but it's obviously harder to ignore the laws of inertia when someone asks you to animate it. (You may interpret it differently, though.)

The SFX team apparently took this problem and envisioned them more "realistically" as something akin to traditional bombs. You can see this in the movie for yourself in one of Dan O'Bannon's tactical displays:

enter image description here

It clearly shows the idea was that the pilot was supposed to "drop" the torpedoes into the exhaust port, like a real world bomb.

Later in the movie, when Luke actually fires his Proton Torpedoes into the Death Star, we see them shoot straight into the distance, and then "drop" into the exhaust vent. This implies some further input from Luke, but actually he turns off his targeting computer in order to manually decide when to fire his torpedoes into the exhaust port, and there doesn't appear to be any further input from him after that at all. Very confusing.

Indeed, if you slow down the infamous shot in question, you can see that the animator seemed want the torpedoes to appear to be falling... it's the just animation happens too quickly you don't see it. (And the previous shot of them travelling in a straight line, like a laser, doesn't really help.)

I created this animated GIF, slowing down all 16 frames of the animation, so you can see this for yourself:

enter image description here

So it appears to be a somewhat inconsistent interpretation born out of probably what was only a rough idea in the script to begin with (Lucas was never one for getting bogged down in technical details of his universe), rather than anything deliberately thought out.

Maybe George Lucas could fix this issue in one last "Special Edition"? :) (Just kidding, please don't kill me.)


Expanded Universe Explanation

Of course, that's just one canon. If you're open to letting other authors interpret how Proton Torpedoes work, and are prepared to enter the murky (and often contradictory) "Expanded Universe", then there's more answers waiting for you.

Noting their apparently strange behaviour in the original movie, it seems that most EU authors have imagined Proton Torpedoes to be simple homing missiles with the additional ability of manual remote control.

Here's some samples from the EU novels:

  • X-Wing: Rogue Squadron (1996), Michael A. Stackpole

"Corran switched over to proton torpedo target control."

  • Jedi Trial (2004), David Sherman and Dan Cragg

"Gunnery officer, mark that target for proton torpedo salvo. Deactivate the homing system. Use line-of-sight guidance system. I want these babies dead on."

In the games (X-Wing, Rogue Squadron, etc.), however, they are treated differently yet again: More like standard slow-but-powerful homing missiles, with no manual guidance. In the X-Wing Miniatures board game they are also treated like homing missiles (requiring a player to "lock" on a target before they can be fired). This is more likely born out of the need for gaming mechanics, however.

Despite this general consensus about their behaviour, other EU sources are contradictory. For example, the aforementioned Jedi Trial states that Proton Torpedoes were first used in the "Clones Wars", yet Anakin's big yellow Starfighter at the end of The Phantom Menace is said to be equipped with them. Furthermore, Star Wars: Knights of the Old Republic II, set thousands of years before the events of the movies, makes mention of them as well.

Basically, with the EU you pretty much get to choose your canon, but most of the time they're considered to be homing missiles, with the ability for manual guidance. (With this interpretation, Luke turning off his targeting computer allowed him to manually guide the missiles down the exhaust port.)

  • You can see the 2004 DVD Special Edition version of the torpedo shot (with pink torpedos) here: i.stack.imgur.com/TmKiz.gif I just thought it would be interesting to see if there was a difference... and there was. Slightly. – Django Reinhardt Jan 12 '14 at 15:38
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    +1, there's something satisfying about this answer, definitely works for me – FoxMan2099 Jan 12 '14 at 17:29
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    TIL proton torpedoes are actually cone shaped missles. – Jared Jul 22 '14 at 0:34
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    The "ninety degrees" could refer to the fact the torpedoes turn 90 degrees during their fall. Even in the briefing animation, they're shown taking an approximately 90 degree turn. This leaves them shooting perpendicularly to their original path at launch time (and the direction of the fighter's nose at launch time), which is straight down into the exhaust port since the fighter was flying parallel to the surface. – jpmc26 Aug 20 '14 at 1:04
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    Never knew what they looked like, awesome. – Organic Marble Feb 18 '15 at 13:56
12

Wookipedia states (without attribution) that proton torpedoes have the ability to turn 90 degrees inside of a meter, with an accompanying image of just what you're talking about.

enter image description here

It seems to me that it wasn't merely getting them into the vent that was the trick, it was that the port was an opening to a path to the reactor. So, practically speaking, the pilot needs to get the torpedoes close enough to the vent to prevent them from being countermeasured or otherwise done away with, and then the internal guidance programming would take over.

It's FAR from canon, but in the old X-Wing and Tie Fighter games, proton torpedoes were target seeking weapons with their own guidance systems.

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    Could you please delete the first half of the answer? I explicitly want canon sources, not Wookiepedia; and there's zero explanation of the mechanism there. On the other hand, games ARE actually canon (just lower level than movie G-canon); so the second half is not a bad answer (though not exactly what I was looking for since it doesn't explicitly explain the mechanism). – DVK-on-Ahch-To Jan 5 '12 at 0:33
  • To be fair though, in the old games even the Advanced Proton Torpedos couldn't turn like that. Now the Advanced Missles, those were pretty awesome. – Xantec Jan 5 '12 at 0:56
  • @DVK The Wookiepedia does refer to an event which must have come from an EU source (a fight between Corran Horn and Erisi Dlarit), it just doesn't state the exact source - so I guess the statement is canon. – HorusKol Jan 5 '12 at 7:25
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    I guess this all depends on your definition of canon. It's always been my impression the Lucas doesn't consider anything outside of the 7 movies and Clone Wars series to be actual canon. – BBlake Jan 5 '12 at 13:12
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    @BBlake - search scifi.SE for "G-canon". There are like 5 or 7 layers of canon in SW Universe. – DVK-on-Ahch-To Jan 5 '12 at 13:30
11

I always assumed that the Torpedoes were 'sucked' in. Although thinking about it, the port is an exhaust port. Perhaps some complex pump system causes a pressure differential after exhausting waste gas.

Unfortunately I don't have any 'evidence' for (or against) this, if anyone does, I'd appreciate an edit to that effect.

Quoting from this answer

The original novel by Lucas states, as an extension to the dialogue heard in the movie, something along the lines of "the shaft would be rendered useless by particle shielding; however, it is completely ray-shielded". This further increases my confidence that the "thermal exhaust" consists primarily of matter and not energy.

So it seems likely that the port was venting matter of some kind that could have created a pressure differential sucking those torpedoes down.

  • 1
    'thermal exhaust port' - it vents waste heat, not necessarily gas. – Jeff Jan 5 '12 at 18:04
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    How do you vent heat into space without venting gas? Unless it radiates it, but then it's a vent.... – AncientSwordRage Jan 5 '12 at 18:06
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    Yes, I always thought they were sucked in after playing Rogue Squadron. (The Proton Torpedoes were dumb missiles that travelled in a straight line) – Starkers May 15 '13 at 22:40
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    If the system is closed, how does my proton torpedo get down into the reactor? :) – Django Reinhardt Jan 12 '14 at 20:23
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    @Pureferret I thought I understood what you're saying... but doesn't that mean the "suction" part only takes place when the system is being closed? – Django Reinhardt Jan 12 '14 at 21:52
5

This was changed from the book version, as the pilots were originally told that they would have to approach the exhaust port at a precise 90 degree angle, precisely fire the torpedoes, then veer away before crashing into the death star itself, both of which are what made it near impossible save for the most skilled pilots, especially while being pursued by Tie Fighters, avoiding turbo laser fire, etc.

Here is the exact quote I copied from another commenter;

You must maneuver straight in down this shaft, level off in the trench, and skim the surface to-this point. The target is only two meters across. It will take a precise hit at exactly ninety degrees to reach the reactor systematization. And only a direct hit will start the complete reaction. "I said the port wasn't particle-shielded. However, it is completely ray-shielded. That means no energy beams. You'll have to use proton torpedoes.

I always assumed that the torpedoes were programmed to turn at 90 degree's and that the real "trick" was the PRECISE moment of firing, which Luke was able to do because of the force and Obi-Wan helping him out. This is why when they showed the targeting computers you saw the two vertical lines closing and the distance counting down to firing time.

I have not come across a specific mention in the books or any other source material I have read as to what the exact MECHANISM is on how or why the torpedoes were able to turn 90 degree's, but they are target lock homing weapons. This I also know to be true from the X-Wing video games. If I have a chance to look through one of the Star Wars Tech manuals I will check it out.

  • as in programmed to turn after say 100m ? thats the theory i was thinking , but surely the targeting computer would be able to work out the exact point when to fire and notify you ? – howler Jan 13 '14 at 12:26
  • Yea, something like that. I'm sure the computer could have figured out the exact time.. but the real question would be whether or not a human could react with the same precision and push the button at that Precise moment. If there is only a 1/5th of a second margin for error, then probably no one save for someone with Jedi skills and force powers could do that, hence the reason why Luke was probably the only one that could do it. – JediWitness Jan 13 '14 at 20:46
  • Upvote - The Legends EU establishes proton torpedoes as programmable in the Thrawn Trilogy, Rogue Squadron books, and well throughout the NJO. – Mark Dec 16 '15 at 15:53
2

Perhaps it had something to do with the positive charge on the Proton Torpedo (thus "Proton" Torpedo) acting with the magnetic field of the exhaust port. The walls could be positively charged while the Death Star core could have a strong negative charge, resulting in the positively charged matter in the Proton Torpedo to be drawn to the exhaust port but repelled from the shaft.

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    Welcome to the site. Can you provide any references to back up what appears to be a conjecture ? – Stan Nov 1 '13 at 19:53
  • This is speculation, not canon as requested, but interesting. In the old Marvel Comics version of Star Wars I think you would have been rewarded a No-Prize. – Meat Trademark Nov 1 '13 at 19:53
  • It looks like your answer is quite anecdotal, do you have any more information to add? Here added references to the points you make would help back up your answer :) – AncientSwordRage Jan 12 '14 at 15:17
2

Well I will give an answer just based on I haven't seen this answer appear on this page yet, at least not as I interpreted the question. First of all the battle to destroy the Death Star (is this actually the second Death Star?) takes place in outer space. Unless the Death Star has an artificial atmosphere, which was not alluded to in the movies, that would mean that the trajectory of the proton torpedoes in question at least until entering the thermal vent shaft would take place in a vacuum.

I found a .pdf of a second edition of the Star Wars Sourcebook by West End Games, which states that in their section on armaments,

"Proton Torpedoes...Unlike heavier space bombardments used by turbolasers mounted in immense Star Destroyers, these weapons are effective against ray and energy shielded targets...Proton torpedoes carry a proton-scattering energy warhead."

Because these warheads I think from this quote are implied to have mass, the only way according to physics to be able to turn these warheads, even if they had an internal steering device, would need to be acted on by a force... i.e. a little rocket booster would have to be turned on mid-flight to correct the direction of the warhead (objects in space will continue to move in a straight line unless acted on by a force (Newton's first law)). According to the graphic that @Django Reinhardt created I don't see those adjustment boosters, at least they're not obvious.

So that's my first point. My second point is that again I am assuming that these proton torpedo warheads have significant weight and my follow up on that would be that the Death Star, due to it's significant size may be exerting a considerable force of gravity, similar to our moon does on our Earth. Therefore, especially given the close distance of Luke's ship it may just be a simple problem of a heavy object falling into a field of gravity, similar to a plane that is moving forward with a velocity v and drops a package, the package then continues moving forward with a velocity v, and falls to Earth because it is pulled by the force of the Earth's gravity downward. It therefore falls in a sort of an arc downward, which may have been what the original plan for the proton torpedoes' flight.

  • Not sure if you're right, but it's a pretty good theory! +1 – DVK-on-Ahch-To Jan 15 '14 at 2:21
  • The Death Star is too light to have significant gravity. It is the size of a small moon, and more or less hollow. People walk inside due to artificial gravity of some kind, because the floors are flat instead of curved. – Oldcat Jul 21 '14 at 23:33
0

A strong magnetic field (from the ray shielding?) oriented from left to right across the surface of the exhaust port would cause actual protons to curve in the direction the torpedoes did. This could also work if the proton-scattering warhead was carrying a number of positively ionized heavy nuclei (the heavier the nuclei and the more ionized they were, the stronger the centripetal force), but I'm not sure how stable that would be. If the fighters approached down the trench from the other direction, though, the torpedoes would've curved up (oops). That being said, it may be that the ordinance was heat-seeking and simply homed in on the heat signature of the main reactor.

0

This merely seems to be a question of converting horizontal inertia to vertical movement. Proton torpedoes have been seen in illustration to have a gyroscopic guidance system. Guided ordnance in space would have the same mechanics of a simple shuttle as far as maneuvering is concerned. Timing the Rotation of the torpedo and then the subsequent main thruster firing along with pitch correction to compensate for the forward inertial movement would require an extensive knowledge of the behavior of the particular projectile (perimeter trim thrusters, lag time if these particular torpedoes are preset to home after "dropping"). Wait... Use the force, Luke.

0

According to the Star Wars: Blueprints - Rebel Edition factbook, The Proton Torpedo consists of four primary components; A Propellant Cylinder, an Energy Envelope Projector, an Ignition Charge and a Homing Sensor (along with the Explosive Payload, obviously).

Since we can disregard the Payload, the Ignition Charge and the Homing Sensor as being the means by which the torpedo can turn, it stands to reason that it's either the Propellant Cylinder or the Energy Envelope Projector that allow tight maneuvering.

The Essential Guide to Weapons and Technology describes the Energy Envelope as a...

"Protective energy envelope to prevent accidental detonation caused by collisions with debris or near misses by laser cannon blasts"

... which leaves only the propellant tube (vectored thrust?) as the means by which the torpedo can execute turns, guided by the homing sensor.

enter image description here

enter image description here

-1

They seem to follow more of a parabolic arch. The screen time is so short, the eye creates the illusion of a sharp turn. Lacking a guidance system, it stands to reason that the torpedoes had a preprogrammed trajectory already established. And the display on the targeting computer seems to reinforce this as more of an optimal firing range rather than a target to lock on. Given the high speed of the fighters, it seems even the computers couldn't postulate the ideal firing time correctly. Seems to me, when Luke opened himself to the Force, it not only told him where to shoot, but when.

-1

Let's simplify things since this question relates to an aspect of a movie that's about 40 years old and the great, and admittedly genius, George Lucas was neither a physicist nor overly concerned with the technical accuracy of his plot elements or special effects. With a couple of minor and unimportant exceptions such as The Force, Star Wars and its space vehicles featured two basic weapon types: energy weapons (from handheld blasters to those bigger weapons mounted on star destroyers, tie fighters, x-wing fighters, etc.) and the proton torpedoes that are the subject of this question. Energy weapons are, by nature, line-of-sight weapons; the energy released travels in a straight line and is uneffected by things like gravity (unless you want to bring black holes into the discussion) or friction (besides being dispersed by refraction in an atmosphere or dust cloud in space). Energy weapons can also be defeated by using "shields" (we'll assume magnetic or something of that sort). The torpedo, on the other hand, is a device similar to a guided missile; it has its own propulsion system and at least some ability to change course (even 90 degrees) once locked on to its target. In WWII, submarines fired unguided torpedoes, which made them function like line-of-sight weapons even though they were self-propelled. Modern torpedoes are guided, much like surface-to-air or air-to-air missiles. We have guided weapons that home in on their targets using various technologies, separately or in combination: radar, sonar, laser, optical, lidar (sort of radar via laser), magnetic, heat, vibration, microwave, and probably some so secret we should take cyanide before mentioning them. I think Lucas envisioned something similar for space combat: energy weapons that can’t turn once fired but are limited only by available power (power sources aren't really addressed in Star Wars) and torpedoes, which are physical devices that can turn (even 90 degrees) after they're fired, but as physical devices, your vehicle could only carry a finite number of them (like maybe two on an x-wing).

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    You might want to consider breaking this lump of text up into paragraphs to improve its readability. – Valorum Apr 8 '16 at 23:40

protected by Valorum Apr 8 '16 at 23:38

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