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This question is related to "The Last Jedi", so let's keep preview spoiler free.

The maneuvre that vice admiral Holdo (with the purple hair) uses towards the end of the film seems remarkably effective.

It seems that it would have worked pretty well much earlier. Especially as

Two other ships were just allowed to run out of fuel and be destroyed.

It seems doing it earlier with different assets would have incurred less losses. Yet nobody seemed to consider it. Any in universe reason why?

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    People don’t seem to like spoilers (as per game of thrones) so I’ve hidden any possible chances, we can come back and touch them up later – Edlothiad Dec 14 '17 at 20:34
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    Also philosophically, undeniable suicide missions are not the resistance's way. Every life matters. As Rose ponints out: Don't fight the ones you hate, but save the ones you love. Of course kamikaze happens sometimes, but these are mostly decisions by a single individual in a desparate moment. This is not part of the overall strategy. – MooS Dec 15 '17 at 7:14
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    More pertinently, why was a human required to remain on the ship to essentially pilot it in a straight line at presumably maximum speed? Surely the ship had an autopilot, or at worst a droid could have been used. There's no in-universe reason for her to stay on board, it's purely a plot device required so that she could perform her later destructive action. – Steven Rands Dec 15 '17 at 9:55
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    Maybe they could leave the worst pilot they have to make a noble sacrifice rather than the Grand Mega Admiral? – Chris B. Behrens Dec 15 '17 at 16:01
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    Not using it earlier when it's the last cruiser the resistance has makes sense. What doesn't is when they didn't do it in earlier episodes since hyperspace has also canonically be proven to go through shields. But that would cut episode 6 really short if they just rammed a cruiser in the death star without going to Endor. And it could definitely have worked if they aimed correctly. – meneldal Dec 17 '17 at 22:39

14 Answers 14

4

I know that this is an old question, but I looked through the answers and the comments here and I noticed that no one has yet mentioned any relevant information from the novelization (not even those posted since the novelization was published), which I think provides the most sufficient answer to this question; and since none of the extant answers have been accepted by the user who asked the question, I thought that I would make a contribution. (Given the length that this answer ended up being, I decided to provide a TL;DR version at the end for those who don't have the time for the long version.)

Let me start by providing some background information: I believe that it's worth noting that, during the evacuation, they were in the process of siphoning their reserve fuel and extracting other supplies for their escape, and implementing other important procedures, but this was all interrupted by the arrival of the First Order fleet.

In the novelization, Lieutenant Connix is speaking to protocol droid PZ-4CO, who alerts her of the incoming First Order fleet. Connix then asks the droid what still needs to be done.

PZ-4CO: Approximately thirty percent of the deep fuel reservoir remains to be siphoned... Scuttle procedure for mission-critical computers is incomplete. And maintenance stocks are still being transferred from lower-level stores.

...

Flight Officer Jones: There are still thirty pallets of cannon shells in C bunker.

p.25; Star Wars: The Last Jedi by Jason Fry

It's also noted that the ships that came to evacuate the Resistance base on D'Qar were already low on fuel when they arrived, but the process of siphoning out their reservoirs would take too long to be of any use (PZ-4CO said that it would take approximately 90 minutes to fully complete the evacuation procedures). Connix gave an order to siphon what they could and be airborne in ten minutes.

The fact that they were in a hurry to finish the evacuation was also hinted at in the film (much more briefly) during the opening scene:

Resistance Evacuation Officer: We're not clear yet. There are still 30 pallets of cannon shells in C bunker.

Lieutenant Connix: Forget the munitions, there's no time. Just get everyone on the transports.

[Star Destroyers appear]

Lieutenant Connix: Oh, no.

Which is why later, shortly after leaving hyperspace when they realized that the First Order had somehow followed them, they were too low on fuel to risk making another hyperspace jump, a move which would have exhausted their remaining supply at the time.

The fact that their evacuation procedures were interrupted, and the fact that they were caught off-guard by the sudden reappearance of the First Order fleet, meant that they were ill-prepared for this situation and that their only viable option at the time was to attempt to outrun them for as long as possible at sub-light speeds. In doing this, it was only a matter of time before each of the Resistance ships ran out of fuel, and their best chances for survival was to transfer survivors to the Raddus (which had the most fuel) from the other ships before they ran out.

Assuming that the kamikaze attack was a move that anyone considered early on, it most certainly wasn't an option until the ship making the maneuver was empty of all survivors (other than the pilot), as it would obviously be fatal for everyone on board. And it appeared that the two smaller surviving ships, the Ninka and the Anodyne (the Vigil was destroyed in the battle that came immediately after the First Order coming out of hyperspace to chase the Resistance fleet), ran out of fuel shortly after evacuating, so it was likely never an option for either of them to pull it off. In fact, it's entirely possible that the Ninka and Anodyne were already too low on fuel to even attempt this move by the time they started to evacuate their survivors over to the Raddus.

So, if this maneuver was ever considered prior to their arrival at Crait, the Raddus was likely the only ship that could pull it off successfully just based on how much fuel they all had. As we saw in the film, despite trying to outrun the First Order for many hours, the Raddus still had enough fuel to make one last jump (and the plan was originally for Holdo to simply lead the First Order away from Crait, rather than attempt to make a counterattack). The film indicates that her kamikaze attack was likely a last-ditch effort that she came up with on the fly shortly after she realized that their escape plan had been compromised. This is confirmed in the novelization:

Aboard the Raddus, a stunned Holdo could only watch as another transport exploded.

...

Holdo choked back a dismayed cry. She had to do something. But what? There was no way the Raddus could defend the transports -- they had moved beyond the protection of its shields.

She looked helplessly at her console, searching for some answer that eluded her. There was nothing.

A light blinked on the interface with the navicomputer.

Holdo called up the interface to dismiss whatever the alert was -- it would only distract her while she tried to think -- then paused.

Someone had entered hyperspace coordinates into the system, calculating a jump that had never been made. The navicomputer was asking if the coordinates should be purged.

It was Dameron, she realized -- he'd rushed to the bridge as part of the plan he'd concocted, the one she'd correctly dismissed as too reckless and desperate to succeed.

Holdo called the coordinates up on her console. The Mon Calamari cruiser had kept traveling along its heading for Crait since the coordinates had been entered into the navicomputer. As a result, the entry point for the hyperspace jump Poe had calculated was now behind the Raddus, on the other side of the First Order fleet.

Holdo stared at her screen, trying to figure out what she had missed and concluded that her wild hope might not be completely unfounded.

p.231-232; Star Wars: The Last Jedi by Jason Fry

Further, the novelization indicates that Holdo could not actually rush the maneuver, and had to pace her moves carefully and time it right in order for it to succeed:

Aboard the Raddus, Holdo hastily rechecked that the heavy cruiser's navicomputer hasn't kicked back the overrides that she'd had to program into it.

...

The First Order flagship began to slide across space ahead of the Raddus... Turbolaser fire continued to lance out from its bow, destroying the Resistance transports seekng safety on Crait.

Holdo reminded herself that there was only one way to help the evacuees -- if she attracted the First Order's attention too early, her desperate gambit would come to nothing. The only thing she could do was wait.

p.247; Star Wars: The Last Jedi by Jason Fry

She got the time that she needed. The First Order officers observing the situation noticed that the Raddus was turning. First Order officer Captain Peavey considered the possibility that she may have been trying to stage a counterattack, but didn't consider the ship to be a threat, as the Raddus's weaponry wasn't strong enough to damage the Supremacy. They quickly realized that she was actually preparing to jump to hyperspace; but, like General Hux, they dismissed it as just a futile attempt to distract them from the escaping transports. They initially decided to let it make the jump to hyperspace, figuring that they could take care of it later (and the Raddus was still far enough away to be out of the effective range of the Supremacy's cannons against its shields). Both the novelization and the film show that Hux and the other officers didn't realize their grave mistake until it was too late.

And here's where arguably the key aspect to Holdo's gambit being successful comes into play: that being the Raddus's experimental shields:

The Raddus' key strength is its advanced deflector shield system that can push the envelope of protective energy far from its hull.

p.10; Star Wars: The Last Jedi: The Visual Dictionary

This is also mentioned in the Incredible Cross-Sections book for The Last Jedi:

Raised Shields: The advanced deflector shields that cocoon the Raddus are an experimental design, capable of sustaining huge amounts of damage before failing. Though the heavy pummeling by the First Order makes structural damage inevitable, most other ships would have been destroyed long before this point.

p.8; Star Wars: The Last Jedi: Incredible Cross Sections

(Lest anyone think that this was a retcon done to explain "plot holes" or to deflect criticism of the film, the Incredible Cross-Sections book and The Visual Dictionary for The Last Jedi were both published on December 15, 2017, the same day as the film's release.)

These shields played a crucial role in how effective and devastating the lightspeed ramming ended up being against the Supremacy.

When the heavy cruiser plowed into the Supremacy's broad flying wing, the force of the impact was at least three orders of magnitude greater than anything the Raddus's inertial dampeners were rated to handle. The protective field they generated failed immediately, but the heavy cruiser's augmented experimental shields remained intact for a moment longer before the unimaginable force of the impact converted the Raddus into a column of plasma that consumed itself.

However, the Raddus had also accelerated to nearly the speed of light at the point of that catastrophic impact -- and the column of plasma it became was hotter than a sun and intensely magnetized. This plasma was then hurled into hyperspace along a tunnel opened by the null quantum-field generator -- a tunnel that collapsed as quickly as it had been opened.

Both the column of plasma and the hyperspace tunnel were gone in far less than an eyeblink, but that was long enough to rip through the Supremacy's hull from bow to stern, tear a ragged hole in a string of Star Destroyers flying in formation with it, and finally wink out of existence in empty space thousands of kilometers beyond the First Order task force.

p.251-252; Star Wars: The Last Jedi by Jason Fry

TL;DR

Given the desperate situation that they were in, which was already bad from the start and was only getting worse by the minute, it's unlikely that anyone ever considered this move earlier in the events of the film. In fact, I was unable to find any information that indicates that anyone had considered trying this move prior to the moment that Holdo executes it, and that she only came up with it on the fly when it became clear that their escape plan had been compromised; and even if anyone did consider it prior to that point, it simply wasn't an option until any vessel that would have been used for this purpose had at least been evacuated (and even then, it still would have needed enough fuel to execute a hyperspace jump, which the Ninka and Anodyne clearly lacked compared to the Raddus). And ultimately, thanks to its advanced experimental deflector shields, the Raddus was the only ship in the Resistance fleet that could have been used to execute this move and achieve the results that we witnessed on film.

Executing this move earlier simply wasn't an option.

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    Experimental shields did it. Thanks – Jeremy French Feb 21 at 11:59
  • @JeremyFrench You're welcome!! I'm happy to help. – Spar10 Leonidas Feb 22 at 15:30
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From the official Star Wars Databank:

Hyperdrives allow starships to travel faster than the speed of light, crossing space through the alternate dimension of hyperspace. Large objects in normal space cast “mass shadows” in hyperspace, so hyperspace jumps must be precisely calculated to avoid collisions

Apparently, this maneuver works, but only if you are jumping a massive object.

It is hard to tell how massive something has to be for that to work, but we can chalk it up to plot that the lost ships wouldn't have been massive enough.

In terms of war economy it is easy to see why this tactic isn't widely used by a smaller force as well(as is the case with the Resistance). In terms of battle economy, if you keep throwing big, expensive ships like that at your enemy, you might be able to cause more damage than your ship is worth, but that still doesn't mean you will be able to cause more damage than the ship is worth to you. In such a small force, the loss of a cruiser might be devastating, therefore it might only be thought as an strategy in last resort. This is the basis of utility theory in economy.

In regards to war economy that would have made more sense if done much earlier, as instead of losing 3 ships, they would just have lost the bigger one. But that still wouldn't be a guarantee win, since destroying the Supremacy clearly didn't stop the First Order from attacking Crait, and it might have even pushed the First Order into a fiercer attack.

Remember that the First Order only continued this starvation tactic because they believed the rebels had no escape, and maintaining this tactic would be more efficient than losing more fighters on a long range engagement. By poking it's big ship, they would be risking enraging the quiet lion into an attack.

Edit: A lot of people keep pointing out that the "mass shadows" are cast by the massive objects in realspace, not by the one in hyperspace, and that is true. Still, we can take two things from this:

  • First, this proves that collisions can indeed occur in hyperspace, and it is plausible to assume that the Supremacy is big enough for that to happen.

  • Second, we know that an object in hyperspace interacts with the "mass shadow" of an object in realspace, not directly to the object itself.

In my mind this means that when collisions occur, the velocity of impact isn't really as important as the mass of the object, since any damage we are doing here isn't damage "to the actual realspace structures" but more like gravitational damage dealt by our ships mass interacting with this "mass shadow". This would be either by stripping mass shadow away or (as the effect in the movie makes more likely) stripping bits of mass into hyperspace.

This last paragraph is just my theory, and there is no source anywhere that corroborates how a hyperspace collision would happen, as far as we know this is the first time something like this ever took place in canon(thought the bit on mass shadows proves it is possible).

It might seem that I am trying too hard to explain why smaller ships can't do this maneuver, and it is because I am. The size restriction is the only explanation that would afford this tactic not being worth using and therefore it not being established previously.

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    I think you’ve misread it, it says large objects in normal space cast “mass shadows” in hyperspace, so jumps have to be calculated for other ships to avoid those shadows (snokes ship being bigger than anything before would make sense) – Edlothiad Dec 16 '17 at 22:35
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    Not sure this argument makes sense. If we're talking about people routinely using this tactic, they wouldn't be using 'big expensive ships' they would be using big, cheap ships. As in, strap sublight + hyperspace engines to an asteroid level of cheap. No need to build hull, life support, weapons or shields. – Scott Dec 18 '17 at 2:41
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    Another thing that might come into play is how counterable such a move could be. The First Order knew that Holdo was firing up Light Speed, but completely ignored her. If they hadn't the Resistance would have still won a few crucial minutes to reach the planet, but the light speed suicide run might have missed. – Edelk Dec 18 '17 at 8:29
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    Wrong answer, large objects that cast mast shadows are planets or stars. Not the ship doing jump itself. Mass shadows are shadows from realspace to hyperspace, not vice versa . And when object is pulled from hyperspace to realspace, it does not travel at light speed . – rs.29 Dec 18 '17 at 17:57
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    What @Edlothiad said. This answer interprets the quote backwards. What it says is that a massive object floating about in normal space will create a "mass shadow" in hyperspace that any ship traveling through hyperspace (regardless of size/mass) must avoid. Which means you need a big target. Precisely how big is unclear, but in the original movies Han mentions that planets can interfere with hyperspace jumps, so anything planet-massed and up is an issue. Probably the real threshold is somewhat less than that, as Snoke's ship, while very large, is likely smaller than a planet. – aroth Dec 19 '17 at 5:45
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Plot hole, somewhat bigger than usual ones ;) Going lightspeed through enemy ships would be perfect tactics e.g. for droids in the Clone Wars. Expendable, programmable pilots that could kamikaze cheap ships into enemy capital vessels.

  Why didn't they do it? It was explicitly stated that ship entering hyperspace does not have physical contact with objects in realspace. Story of Rogue One and some episodes in Rebels and Clone Wars are based exactly on this principle - ship goes into hyperspace very close to obstacle in realspace, but it is never touched. On the other hand, ships in realspace are slow (remember Hammerhead corvette in Rogue One), so ramming tactics are not that successful.

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    Rogue Rouge Small difference in spelling, large difference in meaning. – JRE Dec 16 '17 at 15:49
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    This isn't so much a plot hole as opposed to a retcon. Your final statement is also a rant and does not benefit the answer in anyway. – Edlothiad Dec 16 '17 at 16:10
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    @Edlothiad No, it is not retcon . Retcon is retroactive continuity . There is no continuity here. Rebels didn´t attack Death Star with small ships piloted by droids going lightspeed trough it. And, according to you they could. Nobody in entire history of SW got such bright idea. There is a reason for that. – rs.29 Dec 16 '17 at 17:19
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    @Althis Wrong, page says explicitly " Interdictor-class possessed four spherical gravity well projectors on its sharp-bowed hull. The projectors contained equipment to pull a number of ships out of hyperspace. " Also "One hemispherical projector was more than enough to pull a ship from hyperspace, while the others could be used to block possible hyperspace routes for escape" . – rs.29 Dec 18 '17 at 18:00
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    @Althis And page for interdiction field says "An interdiction field was an artificial gravity well capable of disabling hyperspace maneuvers. Any starship stuck in the middle of an interdiction field became unable to jump into hyperspace. Inversely, such a field could yank a ship out of hyperspace, pulling it out abruptly into normal space." . Therefore, it tah has nothing to do with ship systems, it is simply artificially made gravity field starwars.wikia.com/wiki/Interdiction_field – rs.29 Dec 18 '17 at 18:02
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At the beginning of the evacuation, the plan is to jump to lightspeed. Everyone believed they could not be tracked through lightspeed, so that was the end of it. No one had to sacrifice a big ship (remember how angry they were at Poe for murdering all their bombers).

The First Order then unveils its lightspeed-tracking tech, and re-engages the Resistance. The good guys have to scramble to figure out what to do next, and barely have time to get out of range of the First Order before they're all destroyed. If anyone had jumped to lightspeed in a suicide mission here, they might have destroyed both the First Order and the Resistance; everyone was just too close together, and too disorganized.

After they get out of range, the option to lightspeed-ram the First Order is still off the table, because the First Order shoots them down. The first two abandoned ships only have a matter of seconds after running out of fuel before they go up in flames, it's likely they wouldn't have had time to turn all the way around and engage their hyperdrive. The only reason the cruiser gets a chance to make the jump is because the First Order (was stupid enough to let them?) was preoccupied with shooting down the transport ships.

So, in summary, what the Resistance needed to pull off this maneuver was distance and time. Neither of which they had any to spare for the majority of the film.

Now, as for why no one ever invented hyperspace missiles, that's something I can't answer.

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    Spot on. Nobody could turn around due to the constant fire. Note how slowly Holdo's ship executed its turn. – Machavity Dec 15 '17 at 22:49
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    "the First Order was stupid enough to let them?" Yes. General Hux seems to be a pretty terrible tactician. – KSmarts Dec 16 '17 at 3:16
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    This doesn't seem like a good answer, after all, the "they wouldn't have time to turn the ship around" is pointless once you consider that their shields managed to take First Order fire for days and being depleted was never even considered. Turn that thing around, put all the power to side shields, then front shields and ram the damn thing at the speed of light! – Althis Dec 16 '17 at 21:43
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    They were able to take the constant fire because they moved out of "effective range". The First Order only kept up the barrage to force them to keep moving and exhaust their fuel supplies. – Chris Strickland Dec 27 '17 at 2:38
  • You seem to be interpreting "doing it earlier" in OPs question as "earlier in the film", but the more interesting interpretation is, "Why hasn't this maneuver ever been used before?" I think that is what is being asked here, which you admit you can't answer at all. :( – Cory Klein Apr 12 at 23:08
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Only to follow up @rs.29's correct but not elaborate answer, this is a huge plot hole that will be affecting the rest of star wars merchandise.

My start point would be the hyperspace definition from the databank:

Hyperdrives allow starships to travel faster than the speed of light, crossing space through the alternate dimension of hyperspace. Large objects in normal space cast “mass shadows” in hyperspace, so hyperspace jumps must be precisely calculated to avoid collisions

Raddus, named after Admiral Raddus, the hero of battle of Scarif, is an MC85 Star Cruiser. The length is specified as 3,438.37 meters. I could not obtain any mass evidence so hereby I assume the length is directly correlated by weight.

This indeed may be the largest cruiser employed by the resistance, however the resistance did have large cruisers before. MC80s are of 1200 meters and MC75 are of 1,204.44 meters. These are massive ships relative to Millenium Falcon, a small ship that we know to be capable of jumping to the hyperspace. Rebellion indeed had massive ships, yet we do not see ramming at light speed as a strategy used with these ships.

The empire and the separatists used even bigger ships and they did not consider this strategy not once. For example, ramming of Malevolence, a ship even larger than MC85, to Coruscant could have been a perfect strategy. As long as it holds its deflector shields up, it could last enough to jump to the hyperspace as well, as we have seen MC85 jumping to the hyperspace, but it was not considered.

Using the answer by @DVK-on-Ahch-To here, we know that massive objects can pull you of from hyperspace. The best directly in universe example is the blocking of the fleet of Admiral Raddus by Darth Vader while they were trying to retreat after battle of Scarif. If jumping to hyperspace was an allowed maneuver in close proximity to other massive and not aligned cruisers, we would expect MC75 of rebel alliance to ram into Devastator, the flagship of Darth Vader.

Apparently, from Hux's sudden fear when he ordered units to fire on MC85, the fact that jumping to the hyperspace might damage the vessels on its path is well known. Hence, it should not be the first time we witness such a thing, but to the best of my knowledge, there was no similar strategy in the whole Star Wars universe.

We do see an interesting hyperdrive jump in S01E13 of clone wars, where an uncalculated hyperspace jump caused Anakin and Ahsoka to get lost. They detach immediately from the cruiser, however their reason of detachment is not clarified. Being a very small vessel, Anakin's ship should not cast a "mass shadow" stated in the databank. Anakin and Ahsoka getting lost after the uncalculated jump supports the idea that hyperspace jump calculations are mostly done to determine the exit point from the hyperspace.

In short, this move by Vice Admiral Holdo is unprecedented in the Star Wars universe and it would be a plot hole in the upcoming battles.

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    Comments are not for extended discussion; this conversation has been moved to chat. – Null Dec 18 '17 at 12:24
  • Given what happens when "jumping to hyperspace...in close proximity to other massive and not aligned cruisers", it's perfectly obvious why the rebellion didn't do it above Scarif: they didn't want to blow up everything in sight, themselves included. – Martha Dec 19 '17 at 2:36
  • @Martha I strongly disagree. Adm. Raddus gives clear orders to prepare to jump to hyperspace and four seconds later by movie time Vader fleet arrives and prevents the hyperspace jump. There is no indication whatsoever that this was either automated by the hyperdrive generators or a decision change by Adm. Raddus. Even if that is the case, there is no good reason for rebel fleet not to jump to hyperspace after plans are forwarded to Leia. They could have scuttled half of Vader's fleet if this was physically possible. – C.Koca Dec 19 '17 at 3:19
  • @C.Koca: Could have scuttled half of Vader's fleet... and committed mass suicide in the process. – Martha Dec 19 '17 at 4:14
  • @Martha Were there any survivors from Adm. Raddus's ship anyway? So taking away half the Vader's fleet with them seems more profitable. Besides, these are all our conjecture. So far, what we know is their hyperspace jump was interrupted by Vader's fleet, as it should have happened with Holdo's ship. – C.Koca Dec 19 '17 at 4:20
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TL;DR: Holdo hit a one in a million chance of this actually working, by a combination of incredible skill, luck and poor tactics of the first order.

As far as I have understood the movies, the following rules seem to govern hyperspace travel in Star Wars:

  1. Ships in Star Wars never fly with a relevant fraction of light speed, sub-light travel seems to be quite slow.

  2. Going to hyperspace is a shift to the hyperspace dimension, where ships still travel with normal speed, but hyperspace routes can connect two points in real space with a short cut. So a ship flying through hyper space arrives faster than light travelling the normal path through real space.

  3. Ships coming out of hyperspace travel with normal sublight speed and just appear into realspace.

  4. Big objects like asteroid or big parts of capital ships can easily break through normal Star Destroyer shields and inflict devastating damage.

  5. Big objects cast mass shadows into hyperspace, which are very dangerous for hyperspace traveling ships, so they drop out of hyperspace when the scanners detect an unexpected mass shadow.

My interpretation of the depicted events:

Holdos jump into hyperspace crossed the mass shadow of Snokes giant ship and she disabled the safety system, which would have dropped her out of hyperspace before colliding with the mass shadow. - The collision with the mass shadow ripped her ship apart and these parts dropped out of hyperspace (because the hyperdrive of course failed when her ship was destroyed). The parts of her ship collided with the fleet of the first order with considerable speed, since they were still flying with maximum speed towards holdos ship.

Some parts dropped out of hyperspace inside of shields, some shields may not have been fully powered up and some parts may have been highly explosive (generator, engine, weapon systems...) or simply big enough to create massive damage on impact.

Overall the attack may have only been so effective, because the first order ships flew too close together and were caught by surprise, didn't have their shields fully operational and no interdictor at hand. And there also seems to be a lot of luck and intuition involved, so that the ship wasn't ripped apart too early or thrown off course.

So maybe there is only a 1% chance to even find a hyperspace route and get the timing perfectly right, so ones ship exactly drops out of hyperspace where the target is. If one doesn't get this right all the scattered parts will just appear behind the enemy or randomly fly in the wrong direction. And even if one hits the timing and course perfectly right one has to be lucky to hit sensitive/lowly shielded parts of the enemy, or hit the one in a million chance of an explosive part of the suicide ship appearing inside of a shield

  • Even if this is the case, I strap a hyperspace engine to an bunch of asteroids, turn off the safeties, jump. Even if you talk about deflector shields, I get enough asteroids and enough kinetic energy, I'm going to beat the shields. – ifly6 Jun 9 '18 at 3:59
  • @ifly you are right, you would still have to be good on direction and timing to score a good hit. AND in Canon a hyperdrive is the vastly most expensive part of a ship, furthermore one with the power and reach to carry several asteroids, so it would not be cheap. Plus you would have to hit your enemy, before they just shoot your vessel down, so you need time to bring it into position and a score of tie fighters could vaporize it with a single hit – Falco Jun 9 '18 at 9:21
  • Or a turbo laser could probably splatter an asteroid when reading a hyperdrive signature on it, before the computations for the jump would be complete. – Falco Jun 9 '18 at 9:23
4

New thought: the Supremacy ships also jumped to lightspeed, and the collision happened in hyperspace

Borrowing a little bit from @McIntyre's line of logic, this is clearly the first time that 1) ships have been trackable through lightspeed and 2) this kind of collision occurs. It's rather intuitive that the two are related somehow.

What I propose, with zero evidence for, is that the Supremacy ships were automatically tracking the Raddus. No need for captains here, but you do need a very rapid response as soon as the Raddus jumps - perfect for the ship's computers to handle. As soon as the new tracking software detects that the ship has gone FTL, it takes the Supremacy ships FTL as well.

Thus, the collision itself happens in hyperspace, not in regular space. This resolves the "hyperspace doesn't collide with real space" problem, as well as demonstrating why this tactic wasn't used on the Death Star or similar: those targets weren't in hyperspace, so they couldn't have been attacked in this way. This also explains the rather odd and trippy lighting of the scene. Rather than being a special effects kind of choice, it's simply how a collision in hyperspace should look. You can also see that all nearby planets and stars are no longer visible behind the Supremacy ships- exactly what we'd expect to see if the camera was in hyperspace, but not moving.

The looks of horror on the Supremacy leader's faces were caused by the realization that the tracking program would result in exactly this kind of response. They realized too late that they were going to jump into hyperspace at the same time the Raddus blasted through it.

  • But why was the Supremacy still there? – Möoz May 8 '18 at 3:40
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    @Möoz Presumably, when the hyperspace drive is destroyed, the ships drop back out of hyperspace. Perhaps not instananeously, but any time delay is significant when we're looking at FTL speeds – Dubukay May 8 '18 at 3:50
  • Creative, but the lines "Sir, the Resistance cruiser's preparing to jump to lightspeed."/ "It's empty. They're just trying to pull our attention away. Pathetic. Keep your fire on the transports." indicates they had no worry of being pulled away from firing on the transports if Holdo jumped. – Jacob C. Feb 8 at 10:16
3

Without reconning, I think that this a major plot problem ... I almost jumped out of my seat when it happened. The FTL projectile thing has been left out of a lot of classic sci-fi (including Lucas' universe) because it so completely alters the nature of war. Some other answers discuss the size of the space ship and the shadow it casts in realspace, but I would remind readers that any object approaching the speed of light in realspace is approaching infinite mass (or more if FTL?), so the size of the ship doesn't really matter any more.

m = m0/((1 - v2/c2))1/2

So ... even if the spaceship/projectile is fractionally in realspace and fractionally in hyperspace at the initial instant of the jump to lightspeed, a fraction of a near-infinite mass is ... also near infinite.

I think that authors will need to develop an in-universe "fix" to this problem before the next movie ... like the gravity-well weapon or something else to keep light-speed objects from being used as projectiles. Of course, there will be the separate problem of slowing down something with literally infinite kinetic energy with a technology with presumably finite energy, but maybe that can be addressed also.

  • Yes, exactly. If this works, and hyperdrives can be installed on small ships as we see (on fighters and small freighters) then missile-like ships with just a bunch of rock or metal, a hyperdrive and a droid pilot would be the bane of big ships, able to do devastating damage for a minuscule fraction of the cost/resources/life. – Dronz Mar 29 '18 at 18:06
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Ok well in regards to using hyperspace as a weapon it’s not usable however there are two points were it could be used. Both entering and exiting hyperspace. At both point the ship hasn’t entered or has left hyperspace and is still at a significant fraction of the Speed of light. At this speed the results would be devastating. That said as to why it isn’t used as a tactic? Well space is a very big place and this type of tactic would be a crap shoot in fact it you would be more likely than not to miss your target. Further the rebel alliance and the Resitance are working with limit resources and are desperate but not suicidal. Even throwing junky ships at them would be resource prohibitive.

  • So the most likely result should have been that the admiral missed and just jumped her way someplace random, but only by complete blind luck it worked this time? So really it was a really dumb idea that by all rights should have failed but happened to work, and the drama and alarm around it was inappropriate? And if this can work, given the massive damage done when it does, why not make many robotic suicide missile-ships? – Dronz Mar 29 '18 at 18:09
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I'm thinking that this may be the first case in Star Wars canon where a ship accelerated to lightspeed without entering hyperspace.

It's possible that one of these things occurred:

  1. Snoke's ship was massive enough on it's own that it functioned as an Interdictor, casting a mass shadow large enough to prevent ships from entering hyperspace.
  2. Snoke's ship actually had an interdictor device on board and was actively using it.
  3. Holdo intentionally programmed her jump to avoid going to hyperspace until after she passed Snoke's ship, and was simply accelerating to lightspeed, but had not quite achieved it at the time of collision (.99C)

Thus, we had an actual physical collision of two massive objects, one of which was travelling at a significant portion of C.

I don't have mass figures, but judging by the size of Snoke's ship and the assumed speed of the Raddus, I'd guess that the destruction we saw on screen was significantly less than what normal physics would expect. I would theorize that Holdo did some math wizardry in her calculations to hold the kinetic energy of the collision down to a level where she didn't destroy every object in the entire star system, including the planet.

  • 1
    All those who think this answer is unrealistic, please read this: what-if.xkcd.com/1 – vsz Dec 22 '17 at 18:36
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    1/2) Actually, the events of the movie aren't consistent with a relativistic event. Use this calculator [stardestroyer.net/Resources/Calculators/NuclearExplosions.html] to estimate the yield needed to engulf Snoke's ship (~40gtns), then use this calculator [unitconversion.org/energy/joules-to-gigatons-conversion.html] to convert to joules (1.7e20), and this calculator [hyperphysics.phy-astr.gsu.edu/hbase/Relativ/releng.html] to determine the speed needed for the Raddus (~6e10 kg) to generate that force (.00025c or 270000 kph). – Chris Strickland Dec 29 '17 at 5:41
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    2/2) That's very fast, but not any appreciable fraction of c, and what we see instead is a very localized straight-line damage, not an engulfing blast. I am going to guess that what we're seeing is a hyperspace wake effect, in which portions of the Supremacy are stripped away into hyperspace along with Raddus. This theory also allows for Holdo and the Raddus to have survived. – Chris Strickland Dec 29 '17 at 5:44
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    3/2) Also, I'm estimating the mass of the Supremacy at 1.6e14 kg, which would give it a gravitation about 14 millionths of Earth's. I'm not sure if that's large enough to pull a ship out of hyperspace, but I bet not. The Supremacy is about 3000x larger than Raddus. – Chris Strickland Dec 29 '17 at 5:48
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Perhaps it was caused by an interaction with the hyperspace tracking device, which works in an unspecified, unique manner.

1

The Rebel's plan was to sneak away to their hidden base. It failed because their small transport ships were spotted and the First Order began firing on them.

Up until that point the larger ships were being used to fool the First Order into thinking that they were about to destroy the remaining rebels. The Rebels were also hoping for assistance from their allies as another means of escape.

Given that the light-speed ramming attack didn't stop the First Order's pursuit anyway (it just temporarily halted their attack) it just didn't make sense to do it.

Additionally, when the First Order saw what was being planned they began pounding the ram ship with every available weapon. While not explicitly stated that ship would have required very good shielding to survive long enough, and it's not clear if the other ships had it.

1

(Reasoning-based, not in-universe canon based)

In exercising their own unprecedented tactic to create a never-before-seen, unique situation, the First Order opened themselves up to another.

It all comes down to the hyperspace tracking and the First Order's tactics due to it (which you could put down to hubris). Without it:

  1. hyperspace escape is possible (no need for Holdo Manoeuvre);
  2. if interdicted, no jump possible anyway (no chance of Holdo Manoeuvre);
  3. the approaching force with weapons superiority would not take a slow and patient 'wait until they're out of fuel' approach, (no chance of Holdo Manoeuvre)

3 is the most important. The overconfidence and complacency in letting the prey bleed and weaken is exactly what left the First Order vulnerable to the Holdo Manoeuvre. They could have:

  • held back and waited until fuel was gone, then pounced;
  • relaunched smaller faster craft to take out the Resistance's engines
  • called in reinforcements further along the Resistance's trajectory
  • jumped away and jumped back;
  • jumped away, waited for the Resistance to jump, tracked them again and hit them hard upon jumping to them.

They did none of these things, instead choosing to patiently toy with them, because of their overconfidence in their newly available tactic.

So how does this explain why the Holdo Manoeuvre was never used before?

This situation never happened before. There was never any reason to consider this tactic. Keep in mind, that despite centuries of hyperspace travel, the First Order's hyperspace tracking technology had apparently never been used, or been known to. It's a brand new tactical challenge.

This whole conundrum is only going for 18 hours. We've got people who are very accustomed to the concept of hyperspace travel and the normal limitations of it. In the face of a brand new, game-changing technology, people simply aren't likely to think up a brand new way of doing things straight away. It's going to take time or necessity to come up with something like the Holdo Manoeuvre (which is what happened, and to be fair, it was pretty quick).

Also, keep in mind that Hux appeared to realise what was happening at the last minute. This was a unique situation. The Holdo Manoeuvre, once famous, is unlikely to ever be quite so effective again.

Note: You may ask, why hadn't it been used before in a different situation? For example, to destroy the original Death Star, why not aim a Mon Calamari cruiser and go to hyperspace? Well for a start it's risky. Holdo had nothing to lose, and her manoeuvre wasn't essential for the plan (which was simply to make the First Order think the cruiser was still crewed, creep up on it and destroy it). If it had failed, the original plan would still be fulfilled. If the Holdo Manoeuvre were tried on the Death Star or similar target, and failed, they'd have played their hand and be doomed.

TL;DR

It was a response to a new tactic, and those take time. Really, under 18 hours is pretty good.

  • i would also add that the fleet being out of sb-space fuel was a critical factor. In a normal engagement, there would be no need for such a risky maneuver when a normal ramming would likely achieve the same result. Thanks to the situation, there simply would not have been enough fuel left to first cancel out the forward momentum and then accelerate to ramming speed. The only way to get from point A to point B would be a risky hyperspace jump. – pbuchheit Jan 15 at 16:09
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I agree the physics are a big plot hole.

However in the battle there are some strategic points:

  1. Keep in mind the goal was to get unarmed transports to Crait.
  2. The original plan was the First Order would keep following the flag ship while the transports would land in secret.
  3. As the transports were taking damage Holdo had to improvise quickly. Presumably this manoeuvre is extremely hard to aim.
  4. They couldn't just use all their ships earlier as it would leave the transports unconcealed and without protection.
  5. The New Order could at any point move in and annihilate the Resistance fleet. So using only the abandoned ships in such attacks would have caused them to fight before Crait was close enough.

protected by Edlothiad Dec 19 '17 at 18:32

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