ECS

The Environmental Control System (ECS), or life support, provides conditioned cabin air. Breathable gas composition, temperature control and cabin pressurization are separate functions. An unpressurized vehicle can still provide breathable air: its total cabin pressure follows its surroundings instead of maintaining a separate pressure.

Vehicle pressure arrangements

Each vehicle article lists its own Cabin pressurization and Rated pressure differential in the specifications.

• Unpressurized cabins follow surrounding pressure. Conditioned breathing air does not make a cabin a pressure vessel.
• Pressurized — atmospheric gas intake means the cabin can maintain a pressure difference, but requires sufficient outside atmosphere to replenish gas. Pressurization alone does not provide space capability.
• Pressurized — stored breathing gas means the craft can replenish cabin gas independently of thin outside atmosphere or vacuum.
• An EVA suit is a personal pressure enclosure supplying the wearer’s pressure and breathing environment.

Passenger ARJ modules provide enclosed, pressurized passenger accommodation. Ordinary cargo space is not a substitute for passenger life support. A car carried inside another vehicle follows the surrounding bay environment: the closed bay uses the carrier's cabin pressure, while an open bay exposes it to the outside pressure.

Differential pressure rating

The rating in a vehicle’s specifications is the limit for cabin pressure above the surrounding pressure. For example, 2,400 mbar differential is 240 kPa above the surroundings; it is not a 2,400 mbar absolute cabin-pressure target and is not a rating for pressure in the opposite direction. On craft with the relevant indication, exceeding this rating triggers DIFF PRESS.

Hull and windshield damage can cause pressure failure below the rated limit. An intact vehicle’s failure margin does not increase its operating rating. An unpressurized vehicle has no applicable cabin differential-pressure rating; an unverified rating is marked Not specified.

Surface living and transfers

Living on Vieneo uses conditioned breathing gas near local ambient pressure. At Deois street elevation, approximately 300 m above mean sea level, the reference pressure is about 2527 mbar (2.49 Earth atmospheres absolute). Apartments, garages and surface cars therefore do not normally require a large pressure change simply to move between them and the street. Pressure still varies with elevation; an upper-floor apartment need not have exactly the same pressure as the ground floor.

Pressure compatibility does not make untreated outside air breathable. Vieneo's atmosphere has too little oxygen and contains sulfur dioxide. Habitable air must have the contaminants removed and oxygen controlled by its partial pressure, rather than copying Earth's oxygen percentage at a much higher total pressure.

Automatic cabin control

Pressurized craft automatically adjust their cabin pressure. On the ground, the target is the surrounding pressure. When actually docked at an orbital facility, the surrounding dock environment is one Earth atmosphere, 1013.25 mbar. Merely flying near a station does not mean the vehicle is docked.

In flight, an orbital target selects a one-Earth-atmosphere cabin target. A selected surface waypoint uses its elevation to determine the destination pressure. Without such a waypoint, the controller uses its local approach/above-clouds logic. The pressure target is not a guarantee that the cabin has already reached that pressure.

Powered cabin regulation changes pressure gradually, at up to approximately 0.322 mbar per second. A small difference may equalize directly on the ground or when docked. Space-capable craft can replenish cabin gas from stored supplies; atmospheric-only craft cannot keep increasing cabin pressure when the outside pressure falls below approximately 25 mbar. This distinction matters during high-altitude ascent and suborbital coast as well as in orbit. During descent and re-entry, allow time for cabin pressure to approach the destination environment before transfer.

The pressurization controller is automatic and is separate from Autoflyte. Low airspeed in hover does not by itself remove cabin protection. Watch the cabin and differential-pressure indications where fitted; a normal outside pressure does not prove that the cabin is ready for transfer.

Indications and warnings

Pressures are absolute mbar unless identified as differential pressure. Differential pressure is cabin pressure minus surrounding pressure. It is distinct from the pressure change experienced by a person's ears.

On vehicles equipped with the relevant CAS indications:

• CABIN ALT is a caution below 737 mbar and a warning below about 703.3 mbar. These are cabin-pressure thresholds, not Vieneo terrain-altitude limits.
• DIFF PRESS warns when the cabin-to-surroundings difference exceeds the vehicle's limit. A difference greater than 100 mbar also produces a caution when a pressurized craft is on the ground or a vehicle is docked.
• Hull and windshield condition affect resistance to a pressure failure. Pressurization is not permission to exceed the vehicle's operating limits.

Gradual pressure changes can cause ear popping and temporarily muffled hearing. A rapid, substantial equalization can cause ringing. These effects represent changing pressure, not the steady high pressure of an ordinary Deois residence.

See also

• Living on Vieneo
• Living in Deois
• Bradbury Apartments