Technique: Airbursting Hand Grenades

More grenade thoughts.  This time about cooking them off so they explode somewhere in the air over your target, rather than on the ground near them.

Airbursting Fragmentation Grenades

Typically you throw grenades near someone and it goes off while it's on the ground.  Sometimes, though, that's not a viable option.  Sometimes, it would be ideal if the weapon exploded in mid-air, like a mortar or artillery shell can be made to do.  This makes ground-based cover more or less irrelevant, and makes overhead cover the only real means of protection.

The essence of this is "cooking" the grenade's fuse for a short while before throwing it.  Typically you do this to prevent the enemy from having time to avoid the grenade while it's on the ground, but if you hold it a little longer, it could go off in mid air.

GURPS Basic has rules for airbursts on p.415, and provision for running down a fuse to prevent pitch-back, but doesn't have an explicit mechanic to allow you to combine the two into an air bursting fragmentation grenade.

I'm thinking I could add one.  I'm thinking it would be a penalty to hit at first.  There are some challenges to consider, though:


If you pass the roll, how high above your target does it go off?  That makes a difference for damage resolution.

If you fail the roll, does it go off on the ground after scattering, or in the air?  How high up?  That makes a difference for figuring out targets and damage resolution.

Current Thoughts

You dictate how high above your target you want the thing to detonate.  Default is 1m above where their head was (if standing), so about 3m.

If you are successful on your roll, it detonates there and you resolve as normal against your target (who's cover now counts for less).  A critical success detonates within a meter above them exactly (counts as same hex)!

If you fail the roll by the margin of your airburst technique - that is, by -2 without any points in it - it detonates in the air, at whatever distance it typically resolves to, and at an altitude of twice that if short, half that if long.

If you fail the roll by beyond this margin, it hits the ground and scatters as normal.

That is, a person who would area throw at effective Throwing 14 can Airburst at effective Throwing 12.  If they roll 12 or less, it detonates where desired.  If they roll a 13 or 14 - formerly a success - it will still be in the air and scatter by 1m or 2m and count as being 2m or 4m above the ground.  If they roll 15 or higher, the grenade hits the ground somewhere (as par scatter) and detonates at surface level.

Since scatter distance in lobs are tied to the MoF, our hands are tied a bit - we can't say, for example, a miss by 1 is in the air and a miss by 2 is on the ground, because it will inform distance too regularly.

Distance between something detonating in the air and its target on the ground should be 50% more than the distance between the hex it detonates above and where the target is.  It's a right triangle, because that's simple to solve.  Strictly, it should be like 41%.

Airburst (Average)

Default:  Throwing-2
Prerequisite:  Throwing, cannot exceed Throwing; time-delay fuse grenades only.

You've practiced timing an explosive so that it detonates above a  target rather than on the surface near them.  Declare a hight above your current target you want the grenade to detonate at, and throw using Airburst against your target.  If you succeed, it detonates, and counts as an Airburst (B415).  If you fail by the margin between Throwing and Airburst, the grenade instead scatters and detonates in the air by the distance it would otherwise scatter (B415).  Failure by more than that - i.e. what would have been an ordinary failure anyways - hits the ground and scatters as usual.  Grenades that detonate in the air should be considered to have a distance to ground target equal to 150% of the distance between the hex it detonates over and the target's hex.

Other ideas considered:

• Altitude above target when it detonates:  5-MoS yards above target, minimum 1.
• A miss is a miss, and it always lands on the ground.
• A miss is a miss, and it always detonates in the air somewhere.
• Just a simple -1 or -2 to hit, without any consideration of going off in the air at all - misses are on the ground.

Closing

The general premise is something I feel a player should be able to do.  How I have it written here, however...well, it functions.  Of the myriad other things I thought about, I think this is the best and most playable of them.  Is it the best and most playable possible rule?  Certainly not.  This is just a draft kind of thing, to get it out there for eventual refinement, not something that addresses a rule I think is broken in some way.  GURPSDay is coming up here shortly as well, so I thought I'd toss this on the pile so all of my recent grenade articles are all on the same post.

Thanks for reading!

Cheers!