I think he is imagining detonating all the explosives at once, like a gun, the bullet being the payload you want to put into orbit - like in the Jules Vernes bo

I think he is imagining detonating all the explosives at once, like a gun, the bullet being the payload you want to put into orbit - like in the Jules Vernes books - instead of progressively consuming a fuel like kerosene (which itself has, from wikipedia, an energy density of about 10 kcal/g), leaving more and more mass behind as you ascend. The gun idea seems to be, instinctively, very inefficient because of the need to fight the air density in the lower atmosphere all in one shot. I may be wrong there - mostly imagining what may be wrong with the approach (beyond reducing a live payload to a pink mist) based on kerbal experience :-p