The idea behind the concept is really two fold. First off it has to do with creating a low-end "attritable" unmanned system that has a single purpose—to launch an AIM-120 air-to-air missile either while still attached to a host aircraft or by being launched from that host aircraft and flying for 20 minutes along a series of waypoints and launching the missile on command from a remote location. If the system is launched from an aircraft or if it fires a missile it would not be reusable. If it can hold and fire more than one AIM-120 missile that is a plus, but not a requirement.
The second and maybe the most important aspect of the program is not about what the system can do as much as how it is designed and produced. The goal is to prove that the increasingly damning super long design, testing, and production cycle of modern flying combat systems can be broken. This would be done by leveraging rapid design, prototyping, and manufacturing processes with an aim of producing 500 of these systems in a single month. Obviously the strategic impact of being able to produce weapon systems or even guided munitions on such an elastic basis would be a huge breakthrough fiscally and logistically, and it would be especially impactful during a time of sustained conflict.
As Flying Missile Rail program manager Lieutenant Colonel Jones says, the concept takes the status quo question of "here's what I want, how fast can I get it?" and changes it to "here's how fast I want it, what can I get?"...
They are more disposable:
You don’t have to build a UCAV to fly 8,000 hours as with manned fighter aircraft, a requirement that adds significantly to an aircraft’s unit and development costs. Instead UCAVs can be designed to last a fraction of that flight time. ...
UCAV design and procurement can rapidly adapt to changing tactical realities:
Since they don’t have to have an 8,000 plus flight hour lifespan that will be spread over many decades, new UCAVs with enhanced design features and better low observable qualities can be bought on a regular basis. ...
They are expendible
UCAVs can be ordered to fly into the most dangerous airspace in the world without the potential loss of aircrew being a factor, which can have huge political ramifications both abroad and at home. This also means commanders can take greater risks with greater potential rewards during conflicts and can more freely strike at the heart of the enemy’s ability to wage war. ...
