I used to use Cadweld to make field connections on in-ground copper ground arrays. Cadweld is essentially thermite and powdered copper that produces a flow of molten copper when ignited. You place the copper cables, large copper cables, you want to connect into a carbon mold, load the Cadweld and ignite. When it works it produces a solid cast copper connection that is mechanically and electrically strong, and largely immune to corrosion. A thing of beauty.

If it goes wrong, the most common fault being the presence of moisture that flashes to steam when the molten copper hits it, it explodes with liquid copper and bits of carbon block as shrapnel. Explosions vary from a petulant 'pop', to people potentially getting seriously hurt 50' away. Cadwelding connections in the rain can be quite a thrilling game. If the Cadwelding doesn't bite you there are fair odds that the torches you use to dry the cables and molds are out to get you.

Good times.

I guess you could carry a couple of Cadweld charges for fire starting but even the small ones are about two ounces and you have to ignite the charges. We used spark ignitors, same spark guns used by welders to ignite their torch, or electrical ignitors, essentially the same system used by model racketeers. Total weight for two or three tries would weigh considerably more than a couple of Bics, a full match safe, and a ferro rod or three ... combined.

Military issue thermite or white phosphorus grenades would work, and have been used, but the National Parks Service generally frowns on their use. That, and they exclusively single-use items that weigh close to two pounds each. A butane lighter gives you many more fires per pound, but with far less fun.