I havent been able to do much research for this project google seems to hate this computer, my plans are to take a 1in diameter steel pipe about 2 ft long, filling the pipe with thermite sounds like a good plan, but my questions are, after is eal the thermite into the pipe, what would be the best method of igniting it, planning on fucking up an old car of mine, f this device was placed under the gas tank, what type of results should i expect, a full out explosion of just an insanely hot fire, if there were to be an explosion, any expected blast radius?

First fire mix of either chlorate/sugar, permanganate/ethylene glycol (caution - spontaneous ignition), or a sparkler, or an electric hot match.

What results could you expect? Some molten iron and slag.

Blast radius? Two feet.