Dinitrogen Tetroxide - Use As A Rocket Propellant

Use As A Rocket Propellant

Dinitrogen tetroxide is one of the most important rocket propellants ever developed, much like the German-developed hydrogen peroxide–based T-Stoff oxidizer used in their World War II rocket-propelled combat aircraft designs such as the Messerschmitt Me 163 Komet, and by the late 1950s it became the storable oxidizer of choice for rockets in both the USA and USSR. It is a hypergolic propellant often used in combination with a hydrazine-based rocket fuel. One of the earliest uses of this combination was on the Titan rockets used originally as ICBMs and then as launch vehicles for many spacecraft. Used on the U.S. Gemini, Apollo spacecraft and the Space Shuttle, it continues to be used on most geo-stationary satellites, and many deep-space probes. It now seems likely that NASA will continue to use this oxidizer in the next-generation 'crew-vehicles' which will replace the shuttle. It is also the primary oxidizer for Russia's Proton rocket and China's Long March rockets.

When used as a propellant, dinitrogen tetroxide is usually referred to simply as 'Nitrogen Tetroxide' and the abbreviation 'NTO' is extensively used. Additionally, NTO is often used with the addition of a small percentage of nitric oxide, which inhibits stress-corrosion cracking of titanium alloys, and in this form, propellant-grade NTO is referred to as "Mixed Oxides of Nitrogen" or "MON". Most spacecraft now use MON instead of NTO; for example, the Space Shuttle reaction control system uses MON3 (NTO containing 3wt%NO).

On 24 July 1975, NTO poisoning nearly killed the three U.S. astronauts on board the Apollo-Soyuz Test Project during its final descent. This was due to a switch left in the wrong position, which allowed NTO fumes to vent out of the Apollo spacecraft then back in through the cabin air intake from the outside air after the external vents were opened. One crewmember lost consciousness during descent. Upon landing, the crew was hospitalized 14 days for chemical-induced pneumonia and edema.