How could the Death Star II fire through its shield?

Question

In the Battle of Endor, the unfinished Death Star II was firing its superlaser at the Rebel capital ships while the ground team was still trying to disable the Death Star's shield. Which means the shield was still operational.

In multiple films (e.g. The Emptire Strikes Back, Rogue One), we've seen that both energy and projectile weapons are generally stopped by shields. In Rogue One, we've also been told that

a shield works both ways, i.e. that it's impossible to get out through a shield as well as impossible to get in.

That leaves me wondering: how was the Death Star able to fire through its shield while still being protected by it? Is there an in-universe explanation?

Answer 1

The implication, at least according to the Death Star Owner's Technical Manual, is that the superlaser is sufficient powerful as to penetrate the shield, allowing a majority of the energy to pass through unhindered.

Built on the forest moon's surface, the SLD-26 planetary shield generator consisted of a dish network, an underground generator, and an above-ground shield projector complex that spanned an area of 70km (43 miles) in diameter. The planetary shield generator projected an energy screen that completely enveloped the orbital Death Star II, and could be easily defended bv anti-infantry and anti-vehicle turrets. The only weapon capable of penetrating the energy screen was a superlaser.

The shield presumably then regenerates after the trailing edge of the blast has crossed the shield barrier.

Answer 2

According to the Wookieepedia article on Shields,

Some shields were one-way shields that only allowed a person to come in through the shield, but prevented passage back out through the shield

Also, the majority of ships in Star Wars have shields which are up in combat, but they obviously fire through them to attack enemies.

It makes sense for the Death Star II to have shields which were only one way, so they could be both defensive and offensive at the same time, while the shield over Scarif would make sense to be both ways, as they would want to control the flow of ships and lasers both in and out (no unauthorized entries or exits).

Answer 3

There are a few references in Legends to the idea that very large-scale shields (like planetary shields) operate in "sectors" or "zones" that can be selectively turned off or overloaded. For instance, during the Yuuzhan Vong invasion of Coruscant, several shield sectors on the far side of the planet from the Vong fleet are lowered so refugee ships can escape; later on the shields are noted as failing in sections under heavy bombardment. (This is similar to the idea of "double front" shields and the like seen in the movies, but more granular.)

It seems plausible that just part of the Death Star's shield could be lowered during the firing sequence to let the beam out, then raised afterwards. A ship would have to be extremely lucky to pass through the shield in that brief moment without being vaporized by the beam, so for all practical purposes the shield is still up.