engines instead, where high pressure ratio nozzles are considered desirable. Other vehicles or companies using pressure-fed engine: OTRAG (rocket) Quad (rocket) of Armadillo Aerospace XCOR EZ-Rocket of XCOR Aerospace Masten Space Systems Aquarius Launch Vehicle NASA's Project Morpheus prototype lander NASA Mighty Eagle mini lunar lander CONAE's Tronador II upper stage Copenhagen Suborbitals' Spica See also Gas-generator cycle Combustion tap-off cycle Expander cycle Staged combustion cycle References External links Rocket power cycles Rocket propulsion Rocket engines Thermodynamics