I just found out that there are actually a bunch of alien tech in the game. However, do I have to play in higher difficulties to unlock every alien teach? Or can I just replay it on Normal/Hard over and over? (Also, what makes Hard harder than Normal?) I ask this because, although I love the game, the idea of beating it in HardcORE mode frightens me (I'm not much of a hardcore gamer myself).
You can continue playing the game through on any level to collect the Alien Tech. As the game gets harder the enemies get tougher (more health/shields), aim better, and do more damage with their shots. Generally people can handle hard once they play through on Normal. Enjoy!