
Ramming the planet at 0.1c with the PNS Saladin (850,000 tons) gives the impact of Chicxulub, which happened to be strong enough to cause a global extinction event, and leave a crater over 100 miles in diameter, while hitting at 0.4c gives an impact measured at 6*10^24 Joules.
At these levels of energy, hiding is pointless. Any impact will kill everything within a very large area around it, and if allowed a few missile hits, the planet would be toast. Given this, there probably is no need for shelters, as either you win, or your planet dies.....

cthia wrote:I remember that discussion Vince.
It still seems that proper protocol would be to seek shelter. It isn't like any navy can guarantee any outcome. What if the attackers would have blown right by the defenders? Or any other mess of Murphy madness?
And certainly, now that the MAlign has introduced such stealthy ships, surely underground shelters should be the norm, if they aren't already.