- Shields deflect all damage (except potentially for shield-bypassing weapons) until they are depleted. They have a (very aggressive) recharge rate, which draws (at the moment) 5 Energy/pulse from your pool of energy and pulse four times per second (thus taking 20 Energy/second and recharging RechargeRate * 4 shield points per second). Different ships have different maximum shielding, so the only thing you'll get from swapping out your shield is a faster recharge rate and possibly more protection against energy or projectile arms. Once shields are depleted, damage goes directly to your hull. The hull cannot be recharged or repaired in flight; you must dock and have it fixed at market prices. Docking instantly recharges your shield, free of charge.
- Power Supplies recharge the energy in your ship. Different activities consume different amounts of energy; right now the only activity consuming energy is recharging your shield (energy weapons fire off their own batteries). However, in the future energy will be used by the ECM Attack software as well as the warp engine. They recharge at a variable rate, so upgrading your power supply will increase the speed at which your energy supply recharges. All ships have 100 Energy, so upgrading a ship won't give you more energy to waste. Since the energy system is so important, the player is not allowed to leave a docked station without one installed. It is refilled free of charge when docking.
One of the nice things about these relatively simple types of items is that they are passive; you do not have to be actively involved in their upkeep. This way, a player who is bad at multitasking can simply buy better passive equipment so he is not destroyed while flying around and calculating his phat trade haul.