Internal Doors and Hatches

This section describes the necessary design of internal doors in an underwater habitat. Doors separate functional areas or modules of the habitat

Types of Hatch or Door and its Use

  • Internal Hatches for separation of areas with pressure differentials like decompression or cases of emergency (e.g. during uncontrolled ingress of seawater during a hull breach). They should not be too massive or difficult to operate. Because the pressure hatch’s function is critical, operating procedures and hardware should minimize the chance of unsafe operations. Normally, pressure hatch size and controls should be designed to be used by a suited crewmember. Reliability is enhanced if hatch covers open toward the higher-pressure volume, thus making them essentially self-sealing.
  • Emergency Hatches – Emergency hatches are used primarily for escape or rescue. A dedicated emergency hatch should not interfere with normal activities.
  • Internal Doors – Internal doors may be necessary for visual privacy, reduction of light, reduction of noise and fire barriers. The configuration will vary accordingly.

Opening Size and Shape of a Hatch or Doorway

  • Size – Each hatch or doorway must be sized to provide access for the largest crew member. The size of equipment to be carried through a hatch or doorway should be considered. Certain hatches or doorways may require passage of crew members in diving suits.
  • Suited Crew Members – All hatches must be large enough for ingress and egress of a suited crew member. Generally, internal doorways need be used only by non-suited crew members; in some cases, however, it may be necessary to provide opening room for passage of a suited crew member.


  • Suited Operation – All opening and closing mechanisms must be operable by a single pressure-suited crew member.
  • Unlatching – Hatches must require two distinct and sequential operations to unlatch, to prevent inadvertent opening of the hatch.
  • Securing – Hatches should be mechanically secured against sudden springing up when pressure differential has been failed to notice. Securing could be maintained by a simple metal chain mechanism.
  • Operation from Both Sides – Hatches must be capable of being opened, closed, latched, and unlatched from either side.
  • Rapid Operation – Hatches used to isolate interior areas of the habitat must be operable in no more than 60 seconds, including unlatching/opening and closing/latching.
  • Without Tools – Hatches must be operable without the use of tools. Lost or damaged tools will prevent the hatch from being opened or closed, which may cause serious consequences.
  • Pressure Equalization – The ability to manually equalize pressure from either side of each hatch, by a suited crew member, must be provided.
  • Pressure Measurement – The ability to measure pressure difference across the hatch must be provided from either side of each hatch. This allows land base personnel and habitat crew to see if the pressure difference across a hatch is low enough to safely open the hatch.
  • Windows – Pressure hatches must have a window for direct visual observation of the environment on the opposite side of the hatch, to determine conditions or obstructions for safety purposes.
  • Status – The hatch closure and latch position status must be provided from either side of each hatch
  • Open Position – Hatch covers and doors should be able to remain in the open position.
  • Restraints – Restraints must be provided as necessary to counteract body movement when opening or closing a hatch.
  • Operating Force – The forces required to operate hatch covers must be within the strength range of the weakest of the defined crewmember population, for the worst-case pressure differential anticipated.


  • Opened doors or hatch covers must not restrict the flow of traffic.
  • To avoid interference with translation, doorways and hatches should not be placed near a translation path juncture (including corners) and should be at least 1.5 m from a corner.
  • Door and hatch covers should not open into congested translation paths. Rather, they should open into a compartment.
  • Door and hatch openings should be sized for the traffic flow. To be efficient, a high-use doorway may require an opening to accommodate more than one crewmember at the same time.
  • Alternative designs for doors, such as bi-fold doors and pockets, are recommended if regular
  • doors do not comply with adjacent traffic and activities.

To be added:

  • Is there a possibility to install sliding doors that self-seal during water ingress?

Image: Inflated Lunar Habitat, NASA, Public domain, via Wikimedia Commons

This article contains adaptations from the NASA Human Integration Handbook (HIDH), NASA/SP-2010-3407. NASA copyright policy states that “NASA material is not protected by copyright unless noted”. (See NASA copyright policy page or JPL Image Use Policy.)

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