That's because it wasn't an EMP. It was a tactical nuke that was detonated outside the Earth's atmosphere. Detonating a nuke above an area creates a massive EMP that would destroy any electrical equipment with any amount of electricity running through it. And contrary to popular belief, atomic bombs are typically detonated while still several thousand feet in the air. The EMP effect was discovered by the U.S. Army during the Manhattan Project through the atomic bomb tests
In the vacuum of space, a nuke would be far more devastating than on Earth. The explosion produces mass amounts of charged particles that collide with everything in its way, knocking other oppositely charged particles around (i.e. electrons in an atom), and since electrical systems run on electricity, which is nothing but electrons, it fries any electrical systems. Oh and it also kills and maims people with gamma-rays ^_^.
Now as for the explosion destroying the space station, that's something else entirely. since space is a vacuum, there would be no air pressure blast resulting from the explosion like it would on Earth. Instead it would resemble more of a giant firework going off in the sky and no sound or pressure wave, only radiation and heat...lots and lots of heat. And for the people below the blast, well, the blast of charged particles would make a hole in the ozone layer for a few hours. And for the guys in space...well...they die...from massive amounts of radiation...almost instantly. And they'd probably be burned to a crisp from the heat anyway.
Well that was the longest rant I've posted here, but i hope some of you will forgive me for not citing my sources, but i hope years of watching great documentaries on the History channels and the Discovery channels would at least give me a shred of credibility.
Also..i could easily direct you all to some great links to several websites and documentaries that would back my statements up, but alas...this rant took much of my energy out of me and for now adieu.
