High-Tech/Ultra-Tech Ultra Quickie: Have a seat while I blow you off your feet.

Blast Resistant Seating

Blast effects from mines, IED (Improvised Explosive Device, i.e. home made boom-booms) and near hits from artillery rounds have been found to have a much greater effect the people inside a vehicle even if the blast fails to penetrate the vehicles armor then GURPS assumes. 

Well, they're having a blast.

This is largely because advancements in blast protection has lead to situations where a vehicle survives where it would of been blown to scrap in the past leading to the crew being killed anyways. So now we're finding that even if the blast can be mitigated enough to prevent complete destruction of the vehicles, the shock waves can still be transmitted through the hull into the spine of the poor crew doing nasty, nasty, neurological damage. 

So if you're ok with some extra crunch and want more gritty realism, use the following rule:

 

Blast Damage Through Armor

If a blast fails to penetrate a vehicles DR, use the rules for HESH rounds found on GURPS High-Tech pg. 170 but change the cutting damage to crushing. If using the Lasting and Permanent Injury rules from GURPS Martial Arts pg. 138 (and if you're going gritty you should be heh!) use the Skull Wounds Table. 

So there you go, another way for you, the GM, to make your party dead, dead, dead!

...

Oh right... wait... *slaps forehead* We're trying NOT to kill our PC's.... what was a I thinking?! 

Thankfully after they figured out that concussive blast were turning our troops brains into scrambled eggs they quickly figured things out. If you isolate the chairs they're sitting on from the hull by putting them on a shock absorber style damping system you can can reduce the G forces being exerted on the crew member by a factor greater then 10, turning an impulse that would crush internal organs and slam your brain into the top of your skull into something that might break some ribs and bruise you badly instead. Still sucks buuuut given the alternative I know which I would choose. 

Soooo, you might be wondering, how good are these things? Take a good look at the photo below.

This Styker flipped over and rolled several times after it got hit and an IED. Despite the level of damage you see, no one was killed or even severely injured. So pretty damn good it seems. 

Mobius Protective Systems Advanced Protection System

So as a counter to the Blast Damage through Armor rules, might want to equip your combat vehicles with some of these things. So here's the rules.

Blast Resistant Seating

Blast Resistant Seat (TL 8). These seats isolate the person sitting in them from the frame of the vehicle they are in and uses shock absorber like dampeners to help dissipate the energy from shock waves and impacts. Provides DR 15 vs collision damage (see Whiplash and Collisions Basic, pg. 432) and shocks damage from none penetrating blast damage. Increase DR to 20 at TL 9, 30 at TL 10, and TL 50 at TL 11+. $1,500, 44 lbs. 

If you are adding the seats to an already stated vehicle such as a TL 8 Humvee (GURPS High-Tech pg. 242) or a TL 9 Wheeled ATV (GURPS Ultra-Tech pg. 225), add +24 lbs and +$1,300 per seat to the vehicles states. This will come out it's normal payload limits.