Is there any practical application of trinitramide N(NO2)3 in rocket propellants

Question

In 2010 researchers at the Royal Institute of Technology (KTH) in Sweden announced the discovery of new compound, trinitramide N(NO₂)₃, which could revolutionize production of solid rocket propellants. Seems like the new compound is a candidate for ideal rocket oxidizer because it has several key advantages:

• chlorine free, therefore green propellants could be made out of it,

• high oxygen content, 63.15%, among the highest of all known oxidizers. This means efficient combustion,

• high density, 20-30% greater density impulse could be achieved compared to best current formulations,

• High positive enthalpy of formation because compound has 4 single bonded nitrogen atoms. This means additional energy for rocket aside one achieved from combustion.

But since the announcement of discovery, not much was published about further developments. Is there any practical application of this compound, or it remains just a lab curiosity? What prohibits its mainstream application - production difficulties, cost, stability issues, compatibility with binders, high pressure exponent or maybe something else?

Answer 1

Note that the original research from the 90s determined that it should be "stable"--but stable is not a binary state! It's stable enough that they can make it in the lab under carefully controlled conditions. That doesn't make it stable enough to stuff in a rocket, especially since the presence of certain other things make it decidedly unstable.

You call it a solid but it has a melting point of 280K. That alone would make it seem unsuitable for a rocket.

And, as ikrace says, boom starts with N. I've taken a bit of chemistry but I'm no chemist, but even what little I know that molecule looks like danger. N-N bonds are trouble and there are three of them there. I went looking for an MSDS on it and Google produced a hit that looked so strange I dug through it to figure out why it even thought it made sense.

Turns out there's a very similar molecule that's been in use for quite a while. Instead of a single central N the molecule I found has a ring of 3 Ns in the center. The molecule is commonly referred to as RDX. It's a high explosive. (The strange Google hit was for det cord.)

Answer 2

It is unlikely that trinitramide will ever be a practical rocket propellant. Stability issues prevent the large scale synthesis and isolation of TNA making it an unlikely candidate. And synthesis of trinitramie is not remotely green.

Anything that uses nitronium tetrafluoroborate in its synthesis is unlikely to be as environmentally friendly as it might appear. Even if trinitramide itself contains no chlorine, its production requires complex fluorinated compounds and assorted chemical horrors that themselves are not environmentally friendly to produce. https://en.wikipedia.org/wiki/Nitronium_tetrafluoroborate

Some analogs such tri-substitution with (N(NF₂)₂ have a much improved stability and also shows outstanding performance. But as with many other potential rocket propellants time will tell and these are also not environmentally friendly for similar reasons and are also likely to be difficult and expensive to synthesise.

Current trends are towards using LOX and methane as rocket propellants coupled with increasing the reusability of rockets. Both LOX and and methane are very cheap, readily available in large quantities, fairly high performance, do not contain chlorine and burn cleanly to produce carbon dioxide.

This compares very favourably to the chemical cocktail required to make trinitramide and the chain of complex chemical synthesis required to make that cocktail.

https://onlinelibrary.wiley.com/doi/full/10.1002/prep.202000305

Answer 3

Researchers were just able to synthesize it in detectable quantities in 2010. A rocket would require hundreds of tons per launch, and there's no indication that it's feasible to scale production up to such levels. Even if it could be done, it might be expensive enough to actually make propellant cost significant.

However, even if it was inexpensive to produce in large quantities, the fact that it's not stable at ambient temperature makes it a dead end. It's only theoretically useful in solid rockets, as a replacement for ammonium perchlorate, and the resulting propellant mixes will need to be refrigerated or the oxidizer will melt and become unstable. Consider the results of losing refrigeration on a booster containing hundreds of tons of trinitramide intimately mixed with high-energy fuels.

The costs and hazards of handling solid rockets already make them difficult to justify compared to liquid-fueled rockets. Nobody wants a solid rocket motor that will additionally cause an industrial catastrophe if it gets above 6°C at any point in manufacturing, shipping, and integration into the launch vehicle.