Pounds per square inch
A pounds per square inch (or psi) was a measurement unit of pressure, which was equal to the force of 1 pound applied to an area of 1 square inch.

After the  was attacked by the planet killer, the  on the ship was measured at 11 pounds per square inch. () 

The Class F shuttlecraft  had 15 pounds psi [sic] of fuel left when it lifted off from Taurus II, which was just enough to make one orbit. ()

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Measurements