Boilerplate pathfinders are handy if they are cheap. It's not just checking
out all of the interfaces, which with digital engineering maybe you can
convince yourself all of the interfaces will fit perfectly. Your ground crew
also gets to practice lifts, etc., and dry run all of your ground procedures.
One thing is clear, you always do pathfinder ground operations. The question
is, do you do it with boilerplate hardware, flight hardware, or a mixture of
both. Even for the exception when it is all flight hardware, there is almost
always a practice stacking, a pathfinder operation, before the actual launch.
For Orion Pad Abort - 1 (PA-1) we had a boilerplate Crew Module, a boilerplate
Separation Ring, and a boilerplate Launch Abort System (LAS). We performed
pathfinder operations with the boilerplates. A great way to dry run your
ground operations procedures. And the boilerplates were cheap.
For Orion Ascent Abort - 2 (AA-2) we didn't have the funding or schedule to
have boilerplates. So our first lifts and stacking (pathfinder operations) we
had an inert Peacekeeper motor (Stage-1), but used the actual flight Abort Test
Booster, flight Separation Ring, and flight Launch Abort System. The fact that
we were doing our first stacking with our actual flight hardware was carried as
a risk. It all worked out fine, and we learned some things from the pathfinder
stacking operations. It helped make the stacking for the launch go smoothly.
Pathfinders can be made on production tooling with production flight materials
to gain experience in that area, or they can be simple steel/metal
boilerplates, which are cheap. Looking at the size of the Blue Origin
hardware, having steel boilerplates with accurate weight, CG, simulated
interfaces, and an accurate outer mold line to allow the engineers to check
interfaces and to allow the ground crew to gain experience handling this very
large hardware in my opinion makes sense. The ground operations crew probably
is probably a little concerned about handling what is some very large hardware,
yet it is aerospace hardware so some care in handling is important. And
steel/metal boilerplates can be done relatively early in the program (well in
this case, "early" being a relative term).
The cheapest option is to just skip pathfinders, and just do your pathfinder
operations and first stacking with your flight hardware.
I'd say in summary pathfinders are useful if you can afford them budget-wise
and schedule-wise, especially cheap (steel/metal boilerplates) pathfinders.
Charles E. (Chuck) Rogers