Editing Rocket engine (section)

===Thrust-to-weight ratio===
{{Main|thrust-to-weight ratio}}
Rockets, of all the jet engines, indeed of essentially all engines, have the highest thrust-to-weight ratio. This is especially true for liquid-fueled rocket engines.

This high performance is due to the small volume of [[pressure vessel]]s that make up the engine—the pumps, pipes and combustion chambers involved. The lack of inlet duct and the use of dense liquid propellant allows the pressurisation system to be small and lightweight, whereas duct engines have to deal with air which has around three orders of magnitude lower density.

{{Engine thrust to weight table}}

Of the liquid fuels used, density is lowest for [[liquid hydrogen]]. Although hydrogen/oxygen burning has the highest [[specific impulse]] of any in-use chemical rocket, hydrogen's very low density (about one-fourteenth that of water) requires larger and heavier turbopumps and pipework, which decreases the engine's thrust-to-weight ratio (for example the RS-25) compared to those that do not use hydrogen (NK-33).