Why is there a difference in the speed of explosions caused by the Death Star?

Question

In A New Hope, when Alderaan is blown up by the Death Star, the destruction is instant and very explosive.

Similarly, in The Force Awakens,

when Starkiller Base fired on and destroyed Hosnian Prime (as well as a handful of smaller planets in the Hosnian system), the result was spectacularly explosive, even more so than the destruction of Alderaan.

Now, go back in time to Rogue One.

In it, both Jedha and Scarif are destroyed by the Death Star. However, both explosions are drawn out and less instantaneous. In fact, the destruction of Jedha is so “slow” that Jyn, Cassian, and the other main characters even have time to narrowly escape its destruction.

I might have missed it in the movie, but is there a reason in Rogue One why

Jedha and Scarif’s explosions were more drawn out?

Answer 1

It wasn’t at full power

The Death Star was not being used at full power. It only blew up a portion of the moon’s surface, not the entire moon.

“Target Jedha City,” he snapped. “Prepare single reactor ignition.”

Krennic concealed his resentment, calmed himself with the sounds of his breath and the tidal rush of the station reactor. This wasn’t how he’d imagined the culmination of twenty years’ work—a diminished attack, a grand moff’s power play—but it was the reality he contended with.

_{Rogue One: A Star Wars Story}

Similarly with Scarif:

Tarkin looked to the viewscreen and to Scarif: an ocean-drenched sphere of islands rich with rare metals, useful as a construction outpost and research incubator away from the Senate’s prying eyes. But Tarkin would not miss it. Over the years, too many officers had treated it as a place for unofficial retirement; a tropical paradise where they could neglect their duty in comfort. The loss of the Citadel and the planetary shield would be a pity—but no more than that.

“Single reactor ignition,” Tarkin said. “You may fire when ready.”

_{Rogue One: A Star Wars Story}

Perhaps Tarkin wanted to save the demonstration of the station’s true power for when he was in control of the station, and when he could properly impress the Emperor.

Answer 2

In each case, the firing of the weapon was performed "single reactor", presumably a much less energetic blast than how Alderaan was taken out, using the whole enchilada.

Answer 3

Perhaps the explosions of the planets are simply sped up for the purpose of the viewers. I don't believe that this is true in cannon, but it certainly is true in reality that the speed at which chunks of destroyed planet would have to be moving to escape its gravity well is slow enough that the audience would have to sit through endless hours of planet destruction if they wanted to see it in real time.

Maybe the planets actually do explode at escape velocity and we just see it sped up?

Answer 4

The DS was powered by hypermatter, which is a ridiculously powerful energy source. I cannot remember the source, but I have read that most of Alderaan was blown into hyperspace due to the immense blast, thereby explaining, in theory, the appearance of the explosion and near-impossible speed of the planetary debris. It's a bunch of far-out and hypothetical explanation, but fun to theorize on.

There was only one reactor used (out of ten total reactors) to destroy Jedda City. Wookieepedia explains that the blast was still so powerful that it peeled back part of moon's crust. Use of all ten reactors would take a full 24 hours to recharge the superlaser (DS1...vs a few minutes for a full charge in DS2).