In an ideal case, where space surrounding the launch shaft is not a limiting factor the TBM can be launched in "long mode", whereby the TBM is launched along with it's backup gantry. This is benefitial as it means that the full assembly of supporting equipment is available to the TBM during the launch, improving speed, safety and reliability.

In many cases there is not enough space to launch the TBM with its backup gantry, in this case the contractor will typically launch the TBM in short mode (and may often mine an SCL launch chamber for the TBM depending on ground conditions), once the TBM has advanced far enough, the TBM advance is halted and the backup gantry is connected.

The minimum size of a circular shaft for launching a TBM in short mode is given as follows.