[Vehicles] How big should a self-destruct be?

[DataPacRat]

"The Osterhagen Key is to be used if the suffering of the human race is so great, so without hope, that this becomes the final option."

A particular space-borne cybershell has around 100 hp (and around DR 50 of armour, which won't really affect a self-destruct charge). It also has four computers, each with component armour of DR 100 (and maybe 1 hp each). If things get bad enough that the AI doesn't want any trace of itself left, it needs to be able to reduce not just the whole cybershell, but all four of those computers to -10 hp. IIRC, DR is squared against explosives, so a self-destruct charge would need to have a near-certainty of doing 10,010 points of damage.

According to Vehicles, 100 micrograms of antimatter should do around 0.00125 kilotons of boomage, or 15d*2000 damage, an average of 105,000 points. (10 micrograms would only do an average of 10,500, which is even odds of not being enough.) And at TL10, a storage bay, with -20 bonus to safety rolls, holding that much AM, plus that much AM, is 0.42 lbs, 0.0042 cf, and $5.20. (Not counting the minor detail that it's around LC0, if not LC-1.)

One concern is long-term reliability; the AI doesn't want that AM to be let loose unless it's absolutely sure it wants to self-destruct. So I'm leery of including more than one AM charge, such as one inside each computer-casing, as that multiplies the chances that any one might have something go wrong. Just how safe is that -20? Vp186 says an AM fuel bay will blow up on a 16 or less if damaged; but it doesn't say that's a skill roll, so I'm not sure if the usual "always crit on extremest roll regardless of modifiers" principle applies. If the roll is reduced to effectively "never", then I could significantly reduce the size of the charge(s), and avoid the AI having to deal with uncomfortable problem of deciding whether collateral damage nearby is worth keeping itself out of hostile hands. (Plus, it's much easier to get permission & licensing for boomage that barely escapes the cybershell's armor, compared to boomage that can level a city block or three.)


(I haven't yet decided whether or not to steal a bit of technobabble from Schlock Mercenary: "fullerened antimatter", with antiprotons (or heavier anti-atoms) stored inside carbon-buckyballs. I'm open to other suggestions for "effectively permanently stable, but explodable on demand" AM storage.)