Old School said:
Four crits against power shuts down the ship, and a slow ship can lose its M drive with less, but multiple critical hits at -2 DM short range is quite an accomplishment. Probably only useful to shut down ships that sre already overmatched anyway.
Four crits to either power plant or fuel would shut the ship down. PP can be protected by both bulkheads and emergency power, while fuel can only be protected by bulkheads (much more expensively for a jump ship).
PP crits can be repaired, fuel tanks can also be repaired, but replacing the lost fuel is not so trivial.
Totally it's probably better to go for the tanks.
Achieving crits with good naval gunners with reasonable augmentation and computer support is not all that difficult. Let's say that a few superfighters have made it into dogfighting range; they easily win the dogfight with superior numbers and acceleration.
The first few attacks (with dodge):
Attack: +6[gunner] +5[FireCtrl] +1[aid gunner] +1[sub-command] +2[dogfight] -2[called shot] -3[Evade] -6[dodge] = +4: hit on 4+,
crit on 10+ (17%).
After the target runs out of dodges:
Attack: +6[gunner] +5[FireCtrl] +1[aid gunner] +1[sub-command] +2[dogfight] -2[called shot] -3[Evade] = +10. Autohit,
crit on 4+ (92%).
Damage: 2DD: average 70 - 15 armour = 55, enough to crit a ship with 5500 Hull, about 12500 Dt. Low rolls will not achieve enough damage, let's call it 67% chance of doing enough damage.
So, if the target dodges 6 times the
first six attacks gives 6 × 0.17 × 0.67 ≈ average 0.7 crits.
After that the attacks crit 92% × 67% ≈ 61%, so we need
another 3.3 crits or 3.3/0.61 ≈
5.4 attacks to achieve an average of 4 crits.
Totally 12 attacks will usually achieve the needed 4 crits.
We will have done about 6 × 0.92 × 55 + 6 × 55 ≈ 633 damage, a little over 10% of the damage needed to destroy the target.
We needed about 15 super-fighters (with some losses) à 400 Dt = 6000 Dt to cripple a 10000 Dt ship in a single dogfighting round. If we give it some time about 5 super-fighters would probably be enough.