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.