Aboard the Galaxy-class USS Enterprise-D, the nacelle tube included a small control room, which was found on deck 25, at the rear of the nacelle, near the plasma injectors. The control room was accessible in nominal conditions by Jefferies tube only and was comprised of two levels, with isolation doors providing access to the interior of the nacelle itself. The isolation doors could be opened with the protection of a one-way force field. The doors, however, could only remain open for ninety seconds to prevent force field degradation and the release of drive plasma.