From Outscape Wiki
As of Alpha 3 A planetary assault is an attack to conquer a planet from another player. Also see Raid if you are merely attempting to steal some resources.
To succeed in a Planetary attack of this kind you will need to defeat any defending troops with troops carried by the specialised Assault Troop Carriers built into at least some of the attacking ships
As every planet at least has its Home guard to defend it don't even consider an attack unless you can muster in a single invasion fleet at least 5% of the planets population as troops.
All troops in an invasion attempt currently have to be delivered in one go, which means from a single fleet. At present only Ships from the Frigate tech tree and one or two Corvettes can carry troops. You will have to use the Ship Designer to make up specialised ships for this purpose.
Please note that if the world temperature/hydrosphere is very different to what your species considers normal you may win the battle but immediate start loosing the survivors to the environment. As this is is a possibility consider if your target has free Beron to make Climate Stations or if you will need to immediately do a post conquest building spree just as you would if you had colonised an extreme environment planet.
Once your fleet(s) are ready you can make the attempt.
For an assault to proceed you will have to clear the planets orbit of any and all foreign ships. You can not launch an attack until you control Orbital space.
- Orbital Guns will deliver their damage to the attacking fleet(s) to enter orbit after the last defending ship is destroyed. If a fleet with troops on board survives this. You have a time period while the Orbital guns recharge. See Orbit Defense System for full details on their operation.
- Even if they are recharging one or more Orbit Defense System will destroy a proportion of any troops you send to the planet. This is a flat percentage of the total you send 25%/50%/75% depending on the best Orbital Gun remaining on the planet. Multiple Guns should not combine their defence ratings (But some have a reported that they do - please Bug report if you discover this)
If you discover the defending planet has these guns or an overwhelming number of troops you will need to consider using Orbital Bombers to reduce numbers or stand a chance of destroying one of the Guns.
Select the fleet with troops (or the first one if you have more than one) now click on the planet. A New options will appear alongside "Enter Orbit" or "Colonise" : Assault planet, & steal resources.
When you click on the attack option a pop up will be shown that lists for the first time the total amount of defenders you have to fight. After deducting a percentage for any Orbital gun that you think may be still on the planet the remainder will fight the defenders. Your approximate odds of success will be listed as well but as a generic "Low" "Moderate" or "High" is all that is currently shown.
Once you click invade you may withdraw the troop carrier fleet out of orbit. The invasion will show a count down timer which can be anything from 30 minutes to half a day depending on how your odds were. When the invasion succeeds or fails you will get a message in your notifications.