This is another repeatable fetch quest, but it's not available until you finish the main BoS quest line. This is a repeatable fetch quest that can be obtained by speaking with Scribe Quinlan the first time you enter the Prydwen.
![fallout 4 brotherhood of steel quests fallout 4 brotherhood of steel quests](https://i.ytimg.com/vi/AUUOXHmdBbU/maxresdefault.jpg)
It just earns you caps and the occasional X-111 Compound. This is a repeatable fetch quest that can be obtained by speaking with Scribe Neriah the first time you enter the Prydwen. He's become a Super Mutant due to his research, and Kells wants you to kill him. Often i stay secretly nuetral with all factions as long as i can, like undercover, then i strike. In chapter 2 i choose which path I want to go. I always start railroad BOS and minuteman 1 chapter quests. Is an ex-Institute scientist that helps you infiltrate the Institute. Joining the brotherhood will give you more quests. Those prerequisite quests are after The Molecular Level.
![fallout 4 brotherhood of steel quests fallout 4 brotherhood of steel quests](https://jamestalksgames.files.wordpress.com/2015/11/rubbish.jpg)
The quest begins when the Sole Survivor speaks with Lancer Captain Kells during Liberty Reprimed, after the side quest Duty or Dishonor is completed. It earns you a legendary power armor helmet. I've beaten the BoS quest line plenty of times, and I've done all these quests except for Reactor Coolant. Since you get the retrovirus from inside the Institute's biosciences laboratory it wouldn't be possible to cure him before completing "The Molecular Level". The quest "A Loose End" allows you to convince the Captain to keep Virgil alive as an asset, assuming you've cured him. The "why" is explained here in this spoiler if you want more information (hover to show):
![fallout 4 brotherhood of steel quests fallout 4 brotherhood of steel quests](http://www.fallout4mods.net/wp-content/uploads/2015/11/Improved-BOS-Armour-3.jpg)
You must have also completed the Brotherhood of Steel side quest "Duty or Dishonor." I would suggest doing "The Molecular Level" using The Brotherhood of Steel's scribes to decypher the blueprints and the quests you've mentioned will unlock after that. To start this question you will need to speak with Lancer-Captain Kells aboard the Prydwen. However, the quest "A Loose End" references people and events that don't occur until after "The Molecular Level", and "Getting Technical" follows on from "A Loose End". I haven't completed the Brotherhood of Steel questline yet and like you haven't done more than multiple Quartermastery and Leading By Example quests (which are infinitely generating side quests and not story missions).