Ooh a titanium fire - that would be really cool to see. I wonder if it's possible to make titanium thermite as easily as aluminum thermite?
Designing exotic thermites is a literal direct application of the elementary reaction thermodynamics that you learn in basic chemistry classes. Bootstrapping ignition is a bit more involved and often multi-stage.
How can chemical interactions be "exotic"? Or did they mean "exothermic" or "exciting" or "esoteric"? Is "exotic" a technical term, or did the chemicals simply come from a distant foreign country, and how does that affect their physical properties?
https://www.quora.com/What-are-exotic-compounds-in-chemistry
Is there such a thing as non-baryonic titanium?
https://en.wikipedia.org/wiki/Exotic_matter
>Hypothetical particles and states of matter that have "exotic" physical properties that would violate known laws of physics, such as a particle having a negative mass.
I can understand why you'd want to fill a rocket with exotic matter of negative mass: to make it lighter! ;)
Webster's 1913 for "exotic" includes: extraneous. Same source for "extraneous" includes: without or beyond a thing; not essential or intrinsic; foreign.
First, it can mean observed chemistry that is seen neither in nature nor the lab under ordinary conditions. In other words, it is theoretically possible but the required conditions are so atypical that the expected probability of it occurring unintentionally are very small. I'm guessing this is the case that applies here.
Second, "exotic" can mean engineered chemistry that is far outside the standard industrial spectrum, typically because there is a unique application with very special requirements. Industrial chemistry is all about price performance of the chemistry not absolute performance, but some use cases are more performance sensitive than price sensitive so people will design bespoke and unusual ("exotic") chemistry for the purpose. It is a curve. Everyone uses the cheapest chemistry that still does the job adequately.
More simply, its politely described as "exotic" if you go to a conference and talk about it and people are jealous of your gear / skills / budget / risk taking.
An electronics analogy is a dude who can't solder at all thinks thru-hole soldering is exotic skills and equipment. A dude good at thru-hole thinks SMD is exotic. A dude with good SMD ability thinks owning your own bare die wire-bonder is exotic. A dude with great wire-bond ability thinks working at a foundry and designing custom monolithic microwave chips is exotic. I have no idea what a custom microwave chip designer would think is exotic, probably some Area 51 stuff involving UFOs, realistically maybe working as a physical chemist or as an experimental semiconductor physicist. Those guys probably think super colliders and warp drives and fusion reactors are exotic, I donno.
In fairness, way back when I was playing thermites I just bought the required materials. Metal oxides in particular tend to be boring chemicals and arguably the more malleable half of that equation. Of course, this was in the 1990s when you could legally buy military explosives with a driver's license and cash...
Yeah, it didn't click with me immediately. I saw "titanium fire" but my brain substituted "magnesium fire".
The idea that titanium can catch on fire in a similar way, is…concerning.
… and of course there's a small-scale YouTube video: https://www.youtube.com/watch?v=cH76ObzYIxc
Ditto.
It's rather surprising that any metals at all can withstand the remarkably unhappy oxidizers used in modern rocket fuels! Probably the metal part in contact is an oxide layer that's easily abraded by big chunks of crap.
Thermite made from aluminum and iron can start with a child's firework sparkler, so it is pretty easy to make and use.
Titanium, while not a noble metal, is more resistant to heat and corrosion than aluminum and is just generally less reactive. You might call it "less un-noble" than aluminum. I expect that you'd have a much harder time getting thermite started using titanium. Just look at how much it took to get the titanium fire going on the Crew Dragon- a chunk of NTO had to slam into a valve at really high speed.
Edit: Since you piqued my curiosity, I decided to see if it had been done before. It has: http://developing-your-web-presence.blogspot.com/2008/10/on-... You replace iron oxide with titanium oxide (since titanium pieces oxidize only on a thin outer layer I expect you would need a very fine mesh), and keep the aluminum. This seems to need a little work but it has been done.
Sparklers (i.e. the fireworks) sometimes use titanium to make the sparks, but the primary thing you are igniting is a conventional oxidizer salt (nitrates) and an organic binder. Basically weak rocket fuel with some particles of flammable metal in it to throw off sparks. This is not a thermite reaction. The surface areas of the metals have a huge impact on practical flammability, hence why fine powders are easy to ignite. Iron is also quite flammable as a fine powder but I don't expect my skillet to spontaneously combust on my stove.
Typical thermite bootstraps are three stage for the simple reason that chemistry that is easy to ignite usually does not generate enough thermal power to bootstrap a thermite reaction. A sparkler has a composition that is very similar to a primary stage, a mixture of oxidizer and organics plus a bit of metal for better thermal power (or sparkles, in the case of a sparkler). This is used to ignite the booster stage, which does deliver sufficient thermal power to bootstrap a thermite reaction but is difficult to ignite directly because it is essentially inert anywhere close to room temperature. Boosters are typically direct metal oxidation reactions e.g. aluminum and sulfur.
Useful thermite also tends to be fairly coarse mesh size, which makes it more difficult to ignite. You can trigger a thermite reaction with a fine mesh thermite mixture but that will mostly just give you sunburn and blind you for a day -- typically you want a controlled burn.