I'm doing the Engineering Starbase mission that requires 40 Heavy Phaser Satellite Turrets. What a great idea that was! /* sarcasm */
You need the Heavy Phaser Turret Prototype plans, which you may or may not get when doing the DOff espionage mission in the Cardassian space sector. Then you need Duderon Particles, which you may or may not pick up from random missions. Then you need Contraband, which you may or may not get as a DOff assignment award. Then you can buy some other things (astrometric probe, self-sealing stem bolts, shield generators).
Then, you want to have the exact right DOffs to put everything together (Energy Weapons Officer, Technician, and Research Lab Scientist). Then you talk to your shipboard engineer to get the DOff assignment and wait 1.5 hours.
Then, you fail! Actually, I had a 72% chance of success, but rolled snake-eyes.
I've got enough to try again, but now my engineer won't give me the mission again; it's greyed out. Does this mean that on top of all the hassles listed above, they also stuck a cooldown timer on this thing? That seems unneccesarily onerous.
This mission is like a scavenger hunt, where the grand prize is a rotten egg.
I use my KDF Character to get those. Go sector to sector and do the Purchase heavy Phaser Turrets mission. Longer timer, but I dont need the plans the contraband or anything else just EC for it, I get between 10 and 30 at a time doing it.
Invest in explosives experts (no stubborn) and just grind the abandoned mine field and assist demolition assignments for engineering cxp. Also some repeatable colony assignments. Your success rates will be better and the payoff for resources invested is too.