(n64mon posted while I was replying, but this pretty much answers both posts anyways.)
First in answer to n64's question, the OnFail runs in real-time. However, the problem isn't getting the bomb on the ship but rather getting the text to display if there is a standard "dump cargo landside" aspect to the mission.
It'd be easy enough (both the "land in 2 seconds" part from n64's post and Kruger's suggestion), but then we run into the problem of getting the text to display and getting rid of the bomb on landing. If you make another mission available after the delivery fails, it can only be made to show up on inhabited planets (unless you make one particular mission for every uninhabited planet, which would be crazy). Therefore, if they land on an uninhabited planet they're totally boned because their pilot is saved and they can't dump the cargo. If you make it part of the fail text, it will show right after you get scanned, in which case why not just make it a normal mission failure? If you use a crön or a mission with a time limit of 1 to make it show up after landing, then it will also fire if the player jumps (and the 4-8 seconds before detonation gives ample time for that).
Hey, I have an original idea that meshes perfectly with the Firefly 'verse! Why not just move the player to a system called "Hell"? oh wait...
(further edit)
One thing that I put into the latest update of Anathema was an outfit that, if it wasn't properly maintained, could turn into a nonlethal bomb. However, after it blew, the player would also get an outfit that knocked out their shields and sensors along with putting a noticeable dent in their armor and maneuverability (and maybe fuel capacity). If you want to totally skirt the "now my pilot is screwed forever" problem but still make the explosion not feel like a slap on the wrist, you could do something similar. The ship survives, but suffers some major setbacks and sustains serious damage that can only be removed via a very, very expensive outfit. If you wanted to be really devious, you could make it a delayed explosion to try to get the player to land before it goes off (or even require it). Plus, it makes the risk of the mission slightly less superficial.
This post has been edited by Archon : 21 September 2009 - 02:16 PM