Editing Liquid-propellant rocket (section)

== Pressurization ==
Liquid propellants are often pumped into the combustion chamber with a lightweight centrifugal [[turbopump]]. Recently, some aerospace companies have used electric pumps with batteries. In simpler, small engines, an inert gas stored in a tank at a high pressure is sometimes used instead of pumps to force propellants into the combustion chamber. These engines may have a higher mass ratio, but are usually more reliable, and are therefore used widely in satellites for orbit maintenance.<ref name="Sutton">{{cite book|last=Sutton|first=George P.|title=Rocket Propulsion Elements, 3rd edition|year=1963|publisher=John Wiley & Sons|location=New York|pages=25, 186, 187}}</ref>