User blog comment:101stranger/Ah, the wonderful world of UNSC infantry weapons/@comment-663564-20100405203327

Newtonian physics. They're a pain when in orbit. Just going faster doesn't necessarily mean you get to your target faster. Modern rockets, the fastest known human vehicles, can take several weeks to reach the ISS, and speeding up doesn't help.

In fact, any form of orbital mechanics is just a pain in the ass.