Along your journey in the Zorica system you'll find upgrades for your ship. Each upgrade is obtainable only once, and is found at a debris spot after a short amount of exploring the appropriate area (the asteroid belt or a specific planet).
The first two upgrades allow you to travel much faster through the system. Without them, you can still visit the whole system, but it would take a ridiculously long time.
The second two upgrades allow you to visit the two more dangerous planets, Morena and Veles, by protecting your ship against the special atmospheric conditions. Without them, you can still visit these planets, but your ship will rapidly disintegrate once you have entered the atmosphere.
Cruise Engine Upgrade Edit
It is the first upgrade you get and it is located on the first asteroid where you start the game.
It allows your ship to travel at cruising speed (third gear) to reach other asteroids.
Diaconium Crystal Edit
It powers your Limnal drive and grants you the ability to travel faster than light, enabling you to reach the planets in mere seconds. It is found on one of the various asteroids in the asteroid belt early in game (usually the third or fourth asteroid visited).
You can only obtain one crystal. To know more on the subject, view Notes From Terranova Research Concerning Diaconium.