Rockt Launcher Only Kills Humanoid With A Direct Hit?

I wanted to make a rocket launcher that can kill humanoids without destroying joints. I followed a tutorial on wiki. This is the part of the rocket script that I changed while the other parts are irrelevant. But, I can only kill the humanoid when I shoot a direct hit into them. If I shoot around their bodies, it doesn't effect them, which it should!

function blow(hit)
	Hit = hit
	plr = game.Players:GetPlayerFromCharacter(hit.Parent)
	if hit.Parent.Name ~= ("Door1") and hit.Parent.Name ~= ("Soldier") and hit.Parent.Name ~= ("Door") and hit.Parent.Name ~= ("Governor") and hit.Parent.Name ~= ("Emperor") and not plr then
	swoosh:stop()
	explosion = Instance.new("Explosion")
	explosion.Position = shaft.Position
	explosion.DestroyJointRadiusPercent = 0
elseif plr.TeamColor ~= script.Parent.Parent.Parent.TeamColor then
	swoosh:stop()
	explosion = Instance.new("Explosion")
	explosion.Position = shaft.Position
	explosion.DestroyJointRadiusPercent = 0
	end


	-- find instigator tag
	local creator = script.Parent:findFirstChild("creator")
		explosion.Hit:connect(function(hitPart, partDistance)  onPlayerBlownUp(hitPart, partDistance, creator)
		 if creator ~= nil and not plr and hit.Parent.Name ~= ("Soldier") then
		local maxDamage = 1000
		 local humanoid = hitPart.Parent and hitPart.Parent:FindFirstChild("Humanoid")
	   local plr = game.Players:GetPlayerFromCharacter(hitPart.Parent)
	if humanoid and humanoid.Parent.Name ~= ("Soldier") and not plr then
	       local distance_factor = partDistance / explosion.BlastRadius    -- get the distance as a value between 0 and 1
	    distance_factor = 1 - distance_factor -- flip the amount so that lower == closer == more damage
	        humanoid:TakeDamage(maxDamage*distance_factor)                -- 0: no damage; 1: max damage
	    end
	end
end)

All help appreciated.

Use blastradius.