Metal/Radioactive Extractors Made from Something other than Carboard

For the love of all that is good, can we get extractors that don't explode when hit by anything?  It is incredibly easy to take a few bombers and just attack extractors.  They die in one bombing run, so there's no way to kill a bomber before he can get his payload off most of the time.  Especially if you have like ten.  I don't want nigh invincible extractors, just enough health so they can survive a couple of attacks.  That way a drone bay can have time to repair it.