Rocket Engine Igniter

[Enthalpy]

Hello everyone and everybody!

Some rocket engines inject a small amount of a third propellant that ignites by contact with one main propellant. For instance the RD-170 and heirs start with the liquid oxygen and some triethylaluminium followed by the "kerosene".

The RD-170 had little choice. Much liquid oxygen immediately quenches the many flames in its gas generator, demanding as many ignition sources, easier with the hypergolic pair. But triethylaluminium ignites upon air contact, as probably do all compounds igniting with liquid oxygen. That's badly dangerous near 500t of fuel and oxygen.

I propose here to add two hypergolic propellants for engines whose design fits. Not igniting with liquid oxygen, each can be less dangerous. Coupled positive displacement pumps and optionally an electric motor can dose them. Or optionally, if the main fuel is more reactive, like an amine, one extra oxidizer may suffice.

I still prefer the Diesel hot plug and the preheated propellants I described there
nasaspaceflight on 01/13/2012, 01/22/2012 and around
and also H₂O₂ over a catalyst then mixed with any fuel
scienceforums
hypergols are just one option more.

========== Oxidizer

N₂O₄ is a rocket standard, it ignites quickly most amines and more fuels, but is badly toxic.

Fuming HNO₃ ignites quickly most amines and more fuels. Slight dilution improves its unhealthy fumes. Each 10% water lose only 200K from the >3000K flame, so the ignition delay decides.

H₂O₂ ignites most functionalized fuels, and even "kerosene" with a delay. 70% concentration doesn't detonate without fuel and still provides a 2700K flame, perfect if ignition is fast.

========== Fuel

The solids here can be dissolved in other fuels.

Unsaturated hydrocarbons ignite in peroxide, but rather slowly. COT is highly unsaturated.

Alcohols ignite, not so quickly, and polyols are viscous.

Tertiary amines ignite quickly with N₂O₄, HNO₃ and hopefully with H₂O₂. Few examples, a chemist would propose many more:

• Tetramethyldiaminobutane is a known example, nearly as swift as MMH. Fp=+46°C isn't perfect, and tetramethyldiaminohexane is toxic.
• Pmdeta should ignite as quickly, it has nice physical properties, and is an advantageous main fuel too. Its isomer might result from glycerine and dimethylamine.
• Tetramethylguanidine brings Fp=+60°C, mp<-30°C, 1.4mPa*s.
• TDAE already reacts slowly with air. Fp=+53°C but reportedly very flammable.
• Hexamine and TMTA are amine-rich, tris- and tetrakis(dimethylamino)methane too.

Hydrazines ignite swiftly with N₂O₄ but many are very toxic: hydrazine, MMH, UDMH... Exceptions exist:

• Luminol reacts at room temperature with oxidizers.
• Pimagedine. Diaminoguanidine? Their methylated variants?
• More ?

Imines?

Marc Schaefer, aka Enthalpy