Disabling bitlocker with PowerShell is as easy as you might not believe.
You must first unlock the drive
Unlock-BitLocker -MountPoint D:
Then you can do some object juggling to select the one you want fast using tab completion.
Something to consider, we know you can do this in the GUI, however the GUI i s point and click, where in the city of PowerShell you can use combo moves by combining cmdlets and saving on processing power, battery life and not sacrificing performance.
PowerShell City 