LetMePickThat wrote: Mon Aug 08, 2022 12:27 pm
As for the subject of BMD not using the burn-coast model, I think that it is a reasonable assumption for short range and exoatmospheric systems, because those will either intercept very shortly after ECO (53T6) or fly for a significant portion of their flight outside of meaningful atmosphere. For dual-use rounds (e.g PAC-2, 48N6, Aster 30, David's Sling...), the boost-coast would IMHO provide better results. The 40N6 should definitely use the boost-coast model as well, since it isn't meant primarily for BMD. I also doubt that the solid fuel budget on the missile would allow for continuous thrust all the way to max range.
Thanks! This is actually quite useful feedback.
As a bit of a background. When we originally put together the boost-coast model, we tested it with (among other things) ABM engagements. And the results, in terms of kinematic intercept capability (and thus practical coverage area etc.) plainly didn't make sense. ABM-optimized SAMs simply didn't have the ability to meaningfully protect any area if they were subject to the same boost-coast limitations as AAW-optimized missiles.
If OTOH these missiles retained the legacy "powered all the way" abstraction, the results were pretty close to public-domain info on coverage, intercept ranges & altitudes etc.
This prompted us to further research public sources on BMD systems, discuss with relevant SMEs, compare with known test firings etc. Most evidence suggested that BMD-optimized missiles are generally designed for longer burns than AAW-oriented weapons, in order to make meaningful intercepts possible. This is reflected in their overall design, which is geared for speed at the expense of maneuverability (a typical incoming BM/RV does not maneuver significantly).
Your suggestion is interesting, and it overlaps with a number of tweaks we have in mind to better reflect the compromises of dual-use systems. The latter have to be considered quite carefully as they represent a sizable fraction of modern high-end SAM systems (everything from 40N6 to PAC-3 to 9M82xx etc. etc.). However there are other more immediate dev priorities so this will have to wait.
Then, there's also the question of multi-stage systems and how those could fit in either the continuous-power or the boost-coast model...
We handle those in the BC model, in fact, by granting them much higher "average speed to intercept point"; this leads to longer calculated burn times. It works very well for multi-pulse systems like the AIM-120D (and also other long-burn systems like Meteor). For staged missiles I guess an additional tweak could be an improved post-burnout weight fraction (for the drag & gravity calculations).
