Isopropyl nitrate (IPN, 2-propyl nitrate) is a colorless liquid monopropellant. It is used as a diesel cetane improver. IPN is a low-sensitivity explosive, with a detonation velocity of approximately 5400 m/s. Isopropyl nitrate is extremely flammable and burns with a practically invisible flame. This presents unique hazards in its handling. The flame is significantly less luminous than hydrogen or methanol flame and is only visible due to the turbulent hot air it generates. It has also been used as a fuel for power supply and actuation in guided weapons, notably in the British Royal Navy.