Ammonia borane

This blog has an interest in the CHON dynamic from planet to planet. Here we'll take another peek at oxidising pure hydrogen from low-carbon planets. I know, carbon ain't exactly scarce out in the Belt but - still. Maybe the carbon is locked up below a surface of ice.

To remind: as Elon has told us, chemical rocketry is about combining two chemicals. He divides propellant on one side (with hydrogen) and an oxidant on the other. Like paraffin/nytrox. Or ASCENT and - whatever.

The dark horse that just trotted up to chemists' attention is boron. I'd thought boron was mostly good for soaking neutrons and, maybe, fueling a fusion-engine. Now the chemists are into it: they'd use it for rockets. Meet ammonia borane, NH₃BH₃ but we'll call it AB. As you can see a lot of hydrogen is in there.

They're playing up how ammonia borane is "green" mainly since its spew has no CO₂. To that - whatever. More importantly AB is nontoxic, and so is its oxide which is just rusted boron. There exist nontoxic salts as might boast the same, but they lack the thrust. Also AB stores better than hydrogen, which stores cryogenic. Also ammonia borane isn't flammable at room temperature.

And there is the problem. The whole point of chemical rockets is to burn sh!t up.

Ammonia borane, I am told, has been around for awhile. The reason they didn't take this seriously as a propellant is because it burns best with a catalyst. Now: what do you do with the catalyst on board once it is used? Dump a load of platinum into the Gulf Of Mexico? Seems an expensive waste, even for a space-programme.

The breakthrough is an oxidiser that doesn't need a catalyst or if you like IS the catalyst.

Still, since it's all about blowing stuff up: the metastable-nucleus still looks like the cleanest bet.