Pressure is the force exerted by a gaseous or fluid environment. Atmospheric pressure is specifically the pressure exerted by atmospheric gases (air), usually on a planet or in an artificial environment such as a spaceship.
Measurements
Atmosphere
An atmosphere (atm) is the average air pressure on Earth at sea-level. One (Earth) atmosphere is defined as 101,325 Pascals (Pa), 1.01325 bars (bar), or 14.6959 psi.
The Federation typically measures the atmospheric pressure of planets they encounter in atmospheres, thereby relating them to "Earth-normal".
Pascal
- For other uses, see Pascal (disambiguation).
A pascal (Pa), named after Earth scientist Blaise Pascal, is equal to one Newton per square meter. Atmospheric pressure is commonly measured in kiloPascals (kPa).
Bar
A bar is equal to 100,000 Pa, making it almost equal to 1 atm. Starfleet space suits measure oxygen pressure in millibars (mbar). (VOY: "Day of Honor")
- Millibars are used by meteorologists who find it easier to refer to atmospheric pressures without using decimals.
psi
A psi (pound per square inch), or more accurately, pound-force per square inch, is a unit of pressure based on Earths Imperial units system. At one psi a force of one pound-force is applied to an area of one square inch.
The normal Earth atmospheric pressure is 14.7 psi, which means that a column of air one square inch in area rising from the Earth's surface (at sea level) to space weighs 14.7 pounds.
Comparative list of pressures
- ( 464 atm, 470 bar, 47 MPa, 6.8×103 psi ) – Harry Kim counted 47 Megapascals on his way to engineering. (VOY: "Twisted")
- ( 4.93 atm, 5000 mbar, 500 kPa, 72.5 psi ) – Capped deuterium well heads are under 5,000 millibars of pressure. (ENT: "Marauders")
- ( 1.02 atm, 1033 mbar, 103.3 kPa, 14.9 psi ) – The internal pressure aboard a Borg cube is two kilopascals above what would be normal on a Federation starship. (Star Trek: First Contact)
- ( 1 atm, 1013 mbar, 101.3 kPa, 14.7 psi ) – The atmospheric pressure of the habitats aboard the Nyrian biosphere vessel, encountered by USS Voyager in 2373, were kept at 1 atm. (VOY: "Displaced")
- ( 0.89 atm, 900 mbar, 90 kPa, 13.1 psi ) – The pressure encountered from the leading edge of shockwaves encountered by the USS Voyager following the explosion of a supernova were over 90 kilopascals—over 30% higher than predicted. (VOY: "The Q and the Grey")
- ( 0.790 atm, 800 mbar, 80 kPa, 11.6 psi ) – The atmosphere at the surface of an unnamed planet, which was home to a species of rock creatures, was recored at 800 millibars. (TAS: "Mudd's Passion")
- ( 0.75 atm, 758 mbar, 75.8 kPa, 11 psi ) – After the USS Constellation was attacked by the Doomsday machine, the atmospheric pressure on the ship was measured at 11 pounds per square inch. (TOS: "The Doomsday Machine")
- ( 0.691 atm, 700 mbar, 70 kPa, 10.2 psi ) – While traveling to orbit in an mag-lev carriage, Neelix noted that while at an altitude of 800 meters, the carriage was traveling at a velocity thirty kilometers per hour and the internal atmospheric pressure was at 700 millibars. (VOY: "Rise")
- ( 0.21 atm, 210 mbar, 21 kPa, 3.0 psi )
( 0.25 atm, 250 mbar, 25 kPa, 3.6 psi )
– Warp core pressure aboard Starfleet ships are measured in kilopascals. Upon being pulled into the Delta Quadrant, the USS Voyager's warp core pressure was down to 21 kilopascals. Upon unlocking the magnetic interlocks, they were able to increase it to a stable rate of 25 kilopascals. (VOY: "Caretaker")
- ( 0.113 atm, 114 mbar, 11.4 kPa, 1.7 psi )
( 0.092 atm, 93 mbar, 9.3 kPa, 1.3 psi )
– The computer warned Tom Paris that his space suit was leaking, informing him that the oxygen level was dropping from 114 millibars to 93 millibars before B'Elanna Torres connected to his suit to share her oxygen. (VOY: "Day of Honor")
- ( 0.103 atm, 104 mbar, 10.4 kPa, 1.5 psi )
( 0.086 atm, 87 mbar, 8.7 kPa, 1.3 psi )
( 0.070 atm, 71 mbar, 7.1 kPa, 1.0 psi )
– While Paris and Torres shared their oxygen, the level dropped from 104 millibars, to 87 millibars, and finally to 71 millibars, before they were rescued by USS Voyager. (VOY: "Day of Honor")