To reach the prison, you first need to leave the mines, and head straight forward. Exit to the surface by the door in front.
Destroy all five perimeter turrets. The first one is in front of the exit, three are located scattered along the front area, and one is behind the tower.
Enter the bunker. One of the robots will try raising the alarm by entering the control room above the entrance; this will generate a few hostile robots that will attack.
Collect the G-1 security card, and head down into the acid area. The acid will damage the ship on contact, and will instantly kill you if you bump into a corner containing acid.
Proceed through the tunnels and enter the complex by the lower pipe.
Entering the prison
In the room containing two pipes, look for a door. Enter it, collect the R-1 security keycard, and proceed through the next door. The graing to the left can be destroyed for a secret guided missiles, rapid fire and invulnerability.
To pass through the minimum security checkpoint, use the G-1 security card. A simple mnemonic is to remember that the first letter of the wall color matches the letter of the security card (similar to how Descent and Descent 2 used security doors). Using the wrong card will produce hostile robots.
In the minimum security area, head to the left and collect the Y-1 security card. Return to the front of the ring, and pass through the Medium security checkpoint with the pass.
In medium security, you can optionally work on destroying the data backups by shooting 8 data backup nodes in each of the 2 side rooms.
The gate to maximum security is to the right.
As you enter maximum security, shoot the switch on the floor below to open some forcefields. You can also destroy the mainframe to completely erase the prison records.
Find Dr. Sweitzer within maximum security; the guide bot can bring you there. He is found in a cell with a strobing light, and is usually found by turning left from the entrance to maximum security.
Head into the aintainence shaft and go to the bottom to reach a chemical lab. Shoot the left switch to create a chemical canister, and shoot the right switch when it is over the acid vat. This will cause an evacuation. Find Dr. Sweitzer again in the minimum security area; he can be found by turning right from the maintenance shaft.
Return to medium security checkpoint, and head up into the hangar. Reach the top of the tower, and shoot the switch to turn off the forcefield and complete the mission.