There are 2 (aero)dynamic issues I would be focusing on for high performance
flight that can get you:
(1) the forward shift in CP which Chuck has suggested a good design allowance
for. This is counterintuitive to aircraft designers as the CP will generally
shift backwards for typical high performance aircraft within the supersonic
regime, but is generally true for rockets of typical sounding rocket geometry.
(2) the aerodynamic forces trying to pull the rocket apart. This will depend on
the design of your rocket and how aggressive the acceleration profile ie. going
fast enough (velocity) quick enough (time, in particular air density). This
issue will spring up on you at (or just after) burnout if it does catch you. It
will depend on how draggy your lower section is compared to the upper section
but also internal pressure – ie. if you only bleed your internal pressure out
the side (A) there might not be enough time for your internal volume to bleed
enough pressure for burnout and (B) the external pressure on the base will be
lower than the ambient static pressure. Again, this will be most apparent for
aggressive acceleration profiles.
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Plugger Lockett
Sent: Monday, 15 November 2021 5:51 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Dynamic stability in supersonic rockets
Hello aRocket,
I've been having some conversations with people in the high power rocketry
community as of late regarding minimum diameter rockets encountering issues
with stability during boost when they reach the Mach 3-4 range. The
conventional wisdom in these conversations is that the failures are related to
a lack of dynamic stability. Of course unlike static stability, there's not an
easily passed on guideline for ensuring dynamic stability of a given vehicle.
So I was wondering if anyone here is willing to chime in and shed some light on
how to improve the dynamic stability of a rocket that will see Mach 3+ during
boost?
Any advice is appreciated and thank you for your time.
Kind regards,
Drew Hamilton