Han has a perfectly Solo solution to breaching Starkiller Base’s planetary defense shield. The shield is only capable of keeping out objects traveling at less than light speed, so the answer is obvious: Hit the atmosphere at light speed. Makes perfect sense.
"Sure, okay... Why not?"
There’s no science to STAR WARS, so I’m not going to worry about what would happen to an object hitting a planetary atmosphere at light speed. This is a whole other planet in a whole other galaxy anyway. In fact, I kinda like Han’s casual moments of impossible badass. He blasted out of his own freighter at light speed with a rathtar stuck to the windshield, and if anyone is capable of pulling off the exact calculations and precision timing required to do this, it would be Han Solo and Chewbacca. It’s also such a crazy one-in-a-million thing to do that it perfectly explains why they don’t just have all the Resistance fighters do it too.
Once in atmosphere, they stay low to the surface to avoid sensor detection, eventually landing in a hidden location and making their way to the shield generator on foot.
It is at this point that Finn reveals that, while he did work in this area of the base, his job was sanitation. This provides him no training or insight regarding the deactivation of the shields. He only led everyone to believe this was true so that he could get to the base and rescue Rey. This seems like a grievous deception, since they probably would have cooked up a quickie spot of pseudo-science to figure out how to deactivate the shields if they hadn’t just taken the word of a stranger that he would do it for them.
"It's pretty simple, guys. We just de-polarize the oscillation neutrinos
and take the whole thing down with a concentrated tachyon burst..."
In Finn’s defense on this one, though, while everyone assured him they would work out how to rescue Rey, they were all standing there planning the best way to blow her up with no talk of an extraction strategy of any kind. If Finn had not tricked them into turning his part of the mission into a rescue, there would have been no way the Resistance could have rescued Rey even if they had wanted to.
Finn’s confession is an interesting dilemma for Han. Up until the point he saw Leia, he was trying to pretend to have no interest in the conflict between the Resistance and the First Order. After the destruction of the New Republic’s headquarters and having to face Leia, Han instantly resumes the role of hero, volunteering for a suicide mission to save the galaxy. As if this were not pressure enough, Leia also tasks him with saving their son from the Dark Side of the Force if he gets the chance.
"If you're going to Starkiller Base anyway, would it kill you to go visit your son while you're there?"
But this admission from Finn jeopardizes all of that. Not only will their failure be disastrous for the Resistance pilots, but it will also mean that Han has failed Leia. The desperation in his voice when he says “the galaxy is counting on us” echoes this sentiment. If they can’t take the shields down, everything will be lost even if they do somehow manage to locate Rey. Finn’s disregard for the larger conflict – which mirrors Han’s own – now threatens Han’s renewed effort to become the man Leia wants him to be and, more importantly, the man he wants to be.
But in pure STAR WARS fashion, they don’t let this obstacle deter them from their goal. If Finn doesn’t know how to take the shield down, then they’ll just have to figure it out. This is the sort of unsinkable can-do attitude that makes it such a classic and accessible story.
"Look, Big Deal, I don't care what the movie was about
when it started. This is what it's about now."
Finn comes up with an acceptable alternative. Once inside the bunker, Chewie captures Captain Phasma and they force her to lower the shields. Phasma warns them that their plan is suicide and that her troopers will certainly kill them all. But she lowers the shields anyway, even though you’d think a true believer to the cause would rather die than help them. Maybe Phasma is not quite as loyal to the First Order as she appears, but it’s possible she has the same fatal arrogance that doomed the Empire: She might just believe that nothing they do will allow them to cause any harm to Starkiller Base. In her mind, this may be a temporary setback that can be easily corrected once her troopers dispatch them.
But we won’t know Phasma’s true intentions any time soon. Once she lowers the shields they unceremoniously dump her down a trash chute. Seeing as how trash compactors have a distinctly fatal component, as Han is well aware, this doesn’t seem like they honor their end of the agreement very well (which was at least implied that they would spare her if she helped them).
My favorite part of this sequence is just a little throwaway kind of moment. When they enter the bunker, Han immediately throws off his heavy coat in a burst of impractical bravado. On the way out, as Han rushes off to save the day, Chewbacca dutifully picks up the coat and hands it to him like a mother cautioning a child against the cold. This little moment exemplifies both the individual characters of Han and Chewie as well as the bond they share.