Murphy's Bombing Run

Murphy's Bombing Run is an unmarked and repeatable quest in Fallout 3.

Detailed walkthrough
Murphy is a ghoul scientist, stationed just inside Northwest Seneca Station, who is working on an improved version of the drug Jet, known as Ultrajet. However, he wants the Lone Wanderer's help with finding one of the ingredients: Sugar Bombs.

For every box of Sugar Bombs that the player character brings him, he will offer to pay 15 caps, which can be increased to 30 caps by passing a Speech check. The player character can then purchase 1 Ultrajet from him (around 70 caps each, depends on your Barter skill) for every 8 boxes of Sugar Bombs turned in.

Behind the scenes
The name of this quest appears to be a play on words from the term of the same name. A bombing run is the part of a flight of a bomber aircraft that brings it to the point over a target at which its bombs are released.

Bugs
After speaking to Murphy for the first time, giving him any boxes of Sugar Bombs will result in one not getting paid. Leaving the area and then returning will fix this problem.