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In Star Wars - hyperspace travel has some limitations. For one, you can't get to close to a gravitational body.

We see this in Ep IV - the Falcon must lift off on repulsorlifts and travel at sublight away from Tatooine before entering hyperspace.

I seem to recall something in the novelization about "six planetary radii" when it explained how the Death Star moved using hyperspace and sublight engines.

In the now Legends canon - this gravity limitation was the explanation for the Kessel Run being measure in parsecs (basically, how much of a corner a ship can cut past a cluster of black holes), and even used tactically by the Empire with their Interdictor cruisers.

So, in the new film, how could the Falcon fly through hyperspace to get under the Starkiller Base shields?

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    Some discussion of this on this thread...someone more knowledgeable then me would have to find specific canon references to back this up, but posters on there claim that "going into and out of hyperspace in the atmosphere of a planet happens on multiple occasions in the Clone Wars cartoon", and also that this was dangerous so that ships may have had a safety system normally causing them to drop out of hyperdrive when they get too close to planets, but that it could be disabled. – Hypnosifl Jan 5 '16 at 22:52
  • Having the option of ignoring the safeties on a hyperdrive would render Interdictor cruisers useless. They threw the book out the window. – Mazura Jan 15 '16 at 0:28
  • To add to my comment above, I just watched the episode Jedi Crash, and it does feature a ship whose hyperspace drive is accidentally triggered while it's still in a planetary atmosphere, it jumps to hyperspace with no apparent ill effects. I'll be on the lookout for any episodes showing them dropping from hyperspace directly into a planet's atmosphere. – Hypnosifl Feb 11 '16 at 17:13
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There are actually likely three different gravity well radii that impact hyperspace travel. The first is the true no go zone. You travel through here you die (I.e., the center of a star as referenced by Han in IV).

Then there is likely to be a larger buffer in which the ship will take damage but is not lethal. You can travel here if you know what you are doing and would travel into this part of a gravity well would likely only occur in emergencies.

The third distance is the safe buffer. Normal hyperspace travel would be outside of this radius. This would be what Nav computers and the safety interlocks on the hyperdrive would be set to work with. However if you know what you are doing and have very carefully performed your calculations you can operate between this radius and the damage radius with no ill effects.

For episode VII, the travel to the planet almost certainly was inside the normal safe buffer region and possibly inside the potential damage region. Damaging the ship would have been considered a valid trade off in exchange to getting under the planetary shield.

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    Do you have sources for any of this, or is it speculation? – user45623 Jan 6 '16 at 3:08
  • This is just speculation based on real world analogies. I would have to imagine that there is a safety buffer, especially given that ships in the Star Wars universe are not perfect. It is also reasonable to expect that it is not a white-black line of safe-dead with respect to gravity wells. To me it is reasonable if there is a grey area of increasing damage. – Eric Johnson Jan 6 '16 at 3:12
  • My impression was that Han engaged the safety by hand and let the planet pull him out of hyperspace. The other option is that he eyeballed it while traveling at light speed. – Azor Ahai Feb 20 '16 at 19:59
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It was established in Legends sources (I think the Essential Guide to Vehicles and Vessels was one, but I seem to have lost my copy) that every hyperdrive has a built-in failsafe that cuts it off when too close to a large gravitational body (such as a planet or star). It is supposed to be dangerous and difficult or impossible to override this failsafe, which is why the Interdictor-class Star Destroyers are possible (see http://starwars.wikia.com/wiki/Hyperdrive/Legends )

However, in A New Hope, Han mentions in reference to hyperspace travel, "Without precise calculations we could fly right through a star", suggesting that either these failsafes don't exist in movie canon, or that he has managed to disable the failsafe on the Falcon (not too hard to believe given how heavily he has modified other aspects of the ship).

Alternatively, we see evidence throughout The Force Awakens that technology has advanced in the three decades since ROTJ, so perhaps the failsafes have gotten more precise.

A more difficult question is how Han manages to deactivate the hyperdrive manually (we see him pull the lever!) while traveling faster than the speed of light with such precise timing that he ends up meters from the surface.

  • As for your last question, maybe we could imagine that gravity has a strongly repulsive effect in hyperspace that slows down approaching ships, so by the time they approached the planet their speed was far lower than the speed of light. – Hypnosifl Feb 20 '16 at 14:31
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The gravity well projected by a planet is strong enough to pull ships from hyperspace. ditto for interdictor cruisers. They only way that I can see for han to do this, is to delete the planetary information off the his navigation computer, then plot a course to a point just past the shield layer. which brings up a couple of other issues. One being, the falcon wouldn't be able to withstand that much deceleration in an atmosphere. nevermind, the first point is enough.

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"...One being, the falcon wouldn't be able to withstand that much deceleration in an atmosphere"

As far as my understanding of fictional theoretical hyperspace physics goes, ships do not really "accelerate" or "decelerate" in and out of hyperspace. They simply enter and leave. Hyperspace is a subspace corridor separate from real space where speed and acceleration are relative. Phrases like "make the jump to light speed" confuse the issue a bit. "Light speed", as an actual measured speed, would be woefully inadequate when talking about traversing the monumental distances in the Star Wars Galaxy. Hence, "jumping to light speed" is simply a euphemism Han uses to describe entering hyperspace. From what I understand, the actual speed one is going when entering hyperspace is roughly the speed they will be going when they exit. Enter at a standstill and you will exit at one.

On a further note, The Falcon was a fast ship, not because of the power of its engines, but because of the power of its computers' ability to calculate hyperspace jumps in such a way that trips could be made shorter not only in time but in distance. Calculating their path through space and around celestial bodies in a much more efficient way than lesser ships. This feeds back into the notion of "parsec" being used as a determiner when discussing how fast the Falcon is with Luke. The ship was extremely "fast" at the Kessel run due to its ability to calculate the run with the shortest hyperspace route possible. In Legends, the Kessel run was dangerous and difficult due to the extreme density of stars and black holes in that region of space, making efficient hyperspace route calculations very difficult.

  • No, it had powerful engines - "point 4 past lightspeed" - it could skirt closer to the gravity well because it was fast – HorusKol Aug 16 '16 at 22:19

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