Project Rho A word of caution concerning this incredible website--it is addictive! This website has been around for a number of years and it has amassed a huge following among those who have been lucky enough to have found it. The site goes into excruciating detail concerning almost every aspect of space flight, battle in space, and the dynamics and physics involved in constructing and operating spaceships. Very highly recommended.
Insultingly Stupid Movie Physics Hollywood very rarely gets anything right when it comes to physics. Unfortunately, because people have been exposed to Hollywood physics over and over for years, they tend to expect that what they see on the screen is how things work in the real world. This website clears up a lot of misconceptions. Please read it (and feel free to laugh out loud as you do so) and then use this new information when you write your novel.
WolframAlpha I ran across this website some time ago while trying to find a way to perform a calculation I didn't know how to. This is an interesting website where you type in almost any question you want to have answered and the AI behind the site tries to figure out how to answer your question. It might not work for you, but it's fun to play around with.