You can fit active and passive modules to your ship.
Active modules will use capacitor as a resource when they are turned ON and stop using capacitor when they are turned OFF.
Default they are not used so not using capacitor when you undock a station, you have to click on their icon and they start cycle with ligh-green effect.
When you fly your ship, you see a big circle in the mid-bottom of your screen.
The outer white ring shows the shield, armor, structure hitpoints.
The inner yellow ring divided into very small brick-sectors are your capacitor.
When you use some of your active moduls, they drain your capacitor and when you turn them off, they stop draining capacitor and it starts growing back.
Some active moduls use more capacitor, some active moduls use less.
If you deplete all your capacitor, your active moduls stop working. It is not good. Their is an audio warning effect when you reach very low capacitor level.
What does it mean the capacitor will deplete in a certain amount of time?
It means that if you use ALL active moduls at once, they will drain your capacitor empty in that time shown red in your ship fitting window’s top-right corner.
In my example above my ship is not “cap stable” which means 5 salvager + 1 microwarpdrive could deplete my capacitor fast. How can I avoid it?
I don’t use all of them at once.
I usually use 3-4 salvager, rarely 5 together without microwarpdrive, or i use the microwarpdrive alone to move fast and while i move fast i don’t salvage.
As you can see on the pic I use all 5 salvager at once, it drains the capacitor slowly. But i don’t use the fast speed microwarpdrive because i don’t have a reason for that.
So this example shows that the red number in your ship fitting window is a theoretical time, what is the maximum time you can use all active moduls together the same time. But you don’t have to use them all together.
This way you can play around your capacitor, turning on moduls when you need them and lowering-increasing your capacitor level during the process, keeping your ship and its moduls working with just enough capacitor.
How can you increase your ship’s capacitor level?
You have skills that increase your ship’s resources or lower the resource usage of moduls. Capacitor, power grid etc. Check engineering skills. The basic skills are good to level up because all ships use capacitor and the others so they are always useful skills.
There are moduls that can increase the capacitor level or increase the recharge rate (increasing faster back to its maximum).
There are moduls that can drain capacitor from enemy ships and some enemy ships can drain your capacitor too (especially in PVP, not in low level npc fights). So if your ship is not cap stable, in PVP it can be a weak point enemy players can capitalize. They drain your capacitor and your ship can not fight back because there is no capacitor for laser guns or shield boosters etc.
There are also some rigs and implants and booster drugs that can improve your capacitor levels and recharge rates. I recommend checking rigs first. Implants and booster drugs are very expensive and you can play around with cheap moduls, rigs or simply level up your skills to reach a cap stable ship before you’ll need that extra 3-5 % capacitor level to maximize something with implants or booster drugs.
If your ship has more capacitor than all active moduls can use the same time, it is called “cap stable” and it is shown in the ship fitting window’s top-right corner with a green “Stable” text.
About your mission:
Don’t be affraid to do a mission with a not cap stable ship. If you need to use a microwarpdrive for 30 seconds to do a mission fast and your ship’s cap depletes in 3 minutes, than you have much more cap than needed for that mission. (For example to fly through an explosive gas cloud. Turn the microwarpdrive on when you reach the cloud and turn it off when you exit it. etc.)
Good luck for the mission.