I'm replaying the first Metal Gear game via the Metal Gear Solid HD Collection on the PS Vita, and have now reached Metal Gear itself.
Unfortunately, I messed up and went to challenge that tank with only 13 plastic explosives instead of 16. Without enough explosives, I can't beat the boss, and I can't go back either, as the door behind me is shut and doesn't open at all.
Also, when I die, I'm back at the beginning of the fight, so there's no way I can return to fetch more explosives.
What can I do? Is reloading a save file from before I even reached Building 3 really the only option I have left?