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In episodes IV: A New Hope and VI: Return of the Jedi we are shown ships landing in Death Star 1 and Death Star 2 landing bays seemingly exposed to the vacuum of space, and yet non-suited Imperial personnel are seen standing on deck (for example in about the 3rd minute of Episode VI). How does this work in-world?

If there are some kind of shields, what happens to them when the ships cross the threshold? Why don't we see de/repressurization?

What, in short, is the deal?

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    There's a nice and prominent blue shimmering at the entrances of the landing bays. If that is no "force field" technobabble-something-something, then what is? – Ghanima Feb 22 '15 at 21:34
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    Undoubtedly a force field that allows solid objects (such as ships) to pass through, while keeping gasses in. – Harry Johnston Feb 23 '15 at 3:40
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    Not sure why the downvote. – Lexible Feb 23 '15 at 18:35
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    It's probably whatever allows sound to propagate thorough space in the Star Wars universe. – Spencer Jun 29 '17 at 17:26
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    @Spencer No, that is the Force. I have my theories. – Darth Vader May 24 '18 at 18:20
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TL;DR: The Star Wars galaxy possesses magnetic shield technology, in which a molecule-thin magnetic field prevents air from passing through it, yet somehow allows larger mass through.


The technology used to protect hangars from open space advances somewhat during the Star Wars saga, so I'll discuss both types of technology that we see on-screen.

Galactic Empire: A dynamic magnetic shield

In the original trilogy, hangar bays (as well as any other areas open to space) are sealed using a magnetic shield. The magnetic shield is an electromagnetic field that prevents gases from passing through it, but not solid material. In most cases, a vessel can pass through the shield without requiring deactivation. This allows hangar operations to continue without interruption.

However, in some cases, such as when a ship has a polarized hull which would interfere with normal shield operation, the hangar must be cleared and the shield deactivated before the vessel can enter the hangar. I don't have it handy at the moment, but this was specifically discussed in one of the EU novels.

The shield itself cannot be seen, so areas protected by a magnetic shield have lights set around the opening to indicate shield activation. On Imperial bases and ships, a bright white light is used to show that the shield is on. Some other versions of the technology use a blue light instead.

Death Star Hangar Bay

Old Republic: A static force field

Note that earlier versions of the shield were an actual shimmering "force field". This earlier version did not require any sort of visual indicator since the shield itself could be plainly seen. The older style of shield, however, had to be disabled before a ship could pass into or out of the hangar bay. This is clearly seen during the Battle of Coruscant in Episode III, during which Anakin must destroy the field generator before he and Obi-Wan can fly into the ship's hangar and begin their rescue of Palpatine.

Droid Ship Hangar Bay

Non-Aligned: A dynamic magnetic shield

In the Legends novel "Planet of Twilight", Leia finds herself secured in a mansion on the planet Nam Chorios. A desolate world, the owner of the mansion - one of the wealthiest men on the planet - apparently uses magnetic shielding to maintain a more humid environment indoors... despite having open windows that let in sunlight. In the passage below, Leia notices this as she walks in from a balcony:

The air was softer indoors, subtly modified to escape the piercing dryness. That meant magnetic shields on the doors and windows - not cheap - and some kind of mist generators in the ceilings.

Since she had just walked through the open doorway from an outside balcony, this seems to prove that magnetic shield technology allows objects of sufficient mass to pass through them, yet somehow prevents air or water molecules from passing through the same opening.

Furthermore, Nam Chorios was considered a backwater world. Nobody on the planet - including the owner of the mansion - had access to modern technology. This would indicate that the magnetic shield technology had been around for quite some time (despite still being expensive).


The technology is mentioned again in the Legends novel "Legacy of the Force: Exile" as Lando watches the Falcon land in a hangar bay:

He watched as the Falcon slowly approached. As frail as she looked, he half expected her to bounce off the atmospheric shields that kept the vacuum of space at bay, but she floated gently in through that negligible barrier.

The novel takes place approx. 40 years after Episode VI, so this idea of a magnetic field barrier that keeps in the atmosphere remains consistent for nearly a century across both movies and novels.

  • Per the quote and comments in my answer, it's not clear that the magnetic field actually holds in the atmosphere and allows ships through unimpeded – The Fallen Feb 23 '15 at 22:20
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They were sealed with a magnetic field:

"Clear Bay 327. We are opening the magnetic field." (An Imperial on board Death Star I, just prior to the MIllenium Falcon landing)

Many also had emergency airlocks and blast doors in case the field failed. One example of this can be seen in The Phantom Menace as Anakin blows up the Droid Control Ship (13:45 in the linked video):

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    The magnetic field can't be what keeps the atmosphere in, or when they opened it they'd have lost their atmosphere. I would assume some kind of force field to maintain the atmosphere plus a magnetic field to keep out unfriendly ships / missiles / energy blasts. – Harry Johnston Feb 23 '15 at 3:41
  • I agree with Harry, the fact they open it makes the suggestion it's also the atmospheric containment field a problem. If you have details that show it's definitely the atmospheric containment field as well, could you provide those? – doppelgreener Feb 23 '15 at 4:59
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    There's no canon mentions of that. Remember, Star Wars' concept of physics is, well, interesting. It's possible that in-universe this "magnetic field" keeps the atmosphere contained and it was an oversight that opening it would cause it to escape. Nothing else was mentioned about it that I could find, so anything else is a mystery – The Fallen Feb 23 '15 at 12:00
  • @Harry Johnston - That's assuming just one. Why can't they have layered, sequential fields, like with a physical air lock? Side question - Is the size of the death star enough to exert gravity on an artificial atmosphere, to any degree? – PoloHoleSet Aug 4 '16 at 20:49
  • @AndrewMattson: an airlock approach typically requires you to pump the atmosphere in and out of the chamber, so the ships would need to stop and wait on the way in and out. I don't think there's any sign of that happening. Also I'd expect there to be a clearly delineated "airlock zone". You might be able to avoid both those problems with sufficient technological sophistication, but I think my suggestion is simpler. – Harry Johnston Aug 4 '16 at 22:10
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Probably similar in concept to what is seen in Star Trek TNG. Although in TOS, the hangar deck was depressurized for shuttle arrivals and departures, in TNG there are trekbabble shields which activate just prior to the exterior doors opening, (there is at least one scene where it is clearly depicted) which are able to maintain a shirtsleeve environment in the bay while shuttles can freely arrive or depart. Mind you, the Star Trek folks probably took the idea from Star Wars - I believe the relevant Star Wars scenes appeared well before TNG premiered.

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    Whilst this makes for a reasonable guess, do you have any evidence this might actually be the case in Star Wars? As you can imagine, we can all make guesses, but a guess doesn't make for a satisfying conclusive answer or we wouldn't need to ask. If the answer is that there are really no details, and an educated guess that they just use (cough cough jargon) shields which use (mumble science stop asking questions mumble) to keep the air in, that could be worthwhile pointing out. It is difficult to prove a negative though, i.e. in this case prove they were never described. – doppelgreener Feb 23 '15 at 5:02
  • This isn't technobabble fantasy - those shields are hard scifi. Plasma windows were invented 20 years ago (albeit at a tiny scale) - magnetic fields trap a layer of plasma, whose pressure keeps gasses from passing through. The only thing fictional about them is the technological ability to make them that big. – pluckedkiwi Feb 24 '15 at 18:18
  • I don't ever recall hearing an in-universe canon explanation of the Enterprise shuttle bay shields, at most only depictions of and references to their purpose - perhaps I should not have said "trekbabble". BTW, TNG ran more than 20 years ago, the mentioned Star Wars films much earlier, certainly predating the invention of plasma windows, so I have my doubts that shuttle bay shields were envisioned with plasma window technology serving as either explanation or inspiration. – Anthony X Feb 25 '15 at 1:44
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This a technology as old as the Old Republic, it was discover during ofr before the Mandalorian war; what I do know is that the heavy Centurion-class battleship was equipped with some. This technology is called a containment field, and it even allow the atmosphere to stay in the ship when small breaches occur...

The ravager ship of Darth Nihilus is a phantom space junk, driven by the sheer will a of a half-dead planet-eater vampire addicted to Force drain. He has his slowly dying crew sustained by that kind of containment field, because the ship is in ruins...

In Republic Commando you can overload some device within the hangar bay to cause the containment field to become dangerous for everything that come near-by.

MagCom field : http://assiste.free.fr/kotor_2/magcon.html

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    The last paragraph just looks like a list of questions. Is it relevant to the answer? Also, since English is the language most of our readers have in common, a translation would be helpful. – Adamant Aug 4 '16 at 17:55

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