the entire premise of soul cannon (from first game) falls apart when you think about
on my first playthrough i always assumed, Taranis shot vanagard once, defeated it, but couldn't finish it off, but creators of the canon regretted using such sinister weapon, because it costed someone's life, probably someone from the crew.
that's why the kids felt uneasy near the chamber, it was someone's grave.
first and foremost canon needs as fuel bio-energy, a living being.
so why they didnt the kids just throw a deer in there? a moosheep from the coop?