Of our two requirements categories, the guiding intrinsic requirements are probably the easier ones to nail down. They’re also way more varied.
Intrinsic requirements define how the UAV needs to look, to put it simply. These could specify:
- A particular payload to integrate, such as a certain size/weight of gimbal or even a specific model
- A new engine which integrates a relatively experimental technology, such as running on heavy fuel (i.e. jet fuel)
- Certain geometry features for goals like low observability
- Hard points for mounting pods and other carried components
- Container sizes to fit within, whether that’s disassembling to fit on a specific pallet size for transport or folding up to deploy out of a launch tube
Like I said, these vary by a lot. There are many many ways to come at dictating what an aircraft should look like and what it should carry.
It’s also worth mentioning that I’m looking at this from the perspective of the aerodynamics and mechanical engineers. There are often lots of requirements included that dictate the use of distinct communications systems, antennas, and internal architecture choices. I’m probably offending a handful of avionics and electrical engineers by saying the requirements they care the most about aren’t the guiding ones!
What I’m stressing here is the fact that there will only be a handful of requirements that actually weigh in (pun half intended) on the UAV’s configuration to the point that changing them would change the entire design.
As an example, the requirements could specify use of a gimbal that weighs about 15 lbs. To ensure your aircraft remains stable in flight, you would design to a certain center of gravity (CG) range, and play with the internal layout of all components to be sure the physical CG always ends up there.
If you decided you wanted to integrate a 30 lb gimbal on that same aircraft, though? Your physical CG will likely be much further forward than is safe for the aerodynamic configuration you designed. You’d need to either balance the aircraft by adding ballast in the tail (which sucks, because it’s extra weight that does nothing useful) or redesign the wing and tail to accommodate this significantly shifted CG.
Changing a few antennas usually doesn’t have nearly as drastic of ripple effects as this sort of decision. That’s why I don’t necessarily consider requirements placed on those components to be one of the guiding requirements for the entire project.