Description
The converstion with Krotera didn't go well. As such, your current option is to reach the communication array, and inform the Komato about the Tasen base and occupation.
Walkthrough
Ribbon
Before the two bulkheads, go up. To the left is a large room, which has a small exit on the top-right. Climb it to get the ribbon.
Poster
Requires: 6 Tasen or 4 strength, Tasen Shredder. When you get the shredder, you need to drive it into position. Move right at full speed until it bumps into the bulkhead. Open those two doors using the terminals above, and drive the shredder down the shaft. Power the communication array, and drive the shredder further down.
On the exit floor, you should see a terminal to the left that unlocks the final door. To the left is a cracked wall, which needs to be destroyed by a rocket.
Near the exit, you may see a passage that is too high for you to normally jump. Use the shredder to assist and climb up. If you don't have a rocket launcher, kick one of the Tasen solders down, and convince him to use a rocket for you. Then, climb onto a shredder, drive it down the shaft.
Drive it to the left a full speed, and jump at the last minute. You'll enter the restricted area.
Supercharge
Requires: 4 Strength, 2 Health, or 6 Tasen.
From the starting point, head down the lift and go straight right. Eventually, you should see a glass wall or shield door. Kick the door down, or perform an assisted rocket jump through the glass. Continue right, and jump through the glass window (which should be shattered by the turret.)
Alternatively, approach from the other side by blasting a hole in the wall with a rocket launcher.
At the bottom of the ventilation shaft is a Tasen shredder. Mount it and drive as far as you can to the left. When you reach the end of the line, make a final jump and catch the ledge before said supercharge.
Secrets
You can bypass the bulkhead with sufficient strength. Just kick the shield door above the bulkhead.