Pressurized propellant delivery to rocket engine

Patent Pending The highest specific impulse chemical rockets (liquid-propellant rockets) use liquid fuel propellants. Approximately 170 different liquid propellants have undergone lab testing. This estimate excludes minor changes to a specific propellant such as propellant additives, corrosion inhibitors, or stabilizers. In the U.S. alone at least 25 different propellant combinations have been flown.