Yes, I’ve also seen it more than once or twice. As you say, the really bizarre
part of it is that the rocket often proceeds on the *nominated* trajectory.
Intuitively (if it was a stability issue) you’d expect it to continue on the
deviated path upon straightening up.
The only explanation I can think of is wind shear ie. the top of the rocket
hits it 1st which tips the pointy end downwind, then the fins hit it, which
obviously corrects things; although you’d probably expect an overcorrection?
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Rick Maschek ("rickmaschek")
Sent: Thursday, 21 October 2021 1:37 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Test Launch
I have no idea 'why' but every year at 'HPR' events, I'll see a few solid
propellant rockets leave the rail straight and fast and about 50 to 100 feet
above the launch rail take a quick change in direction and then again proceed
in a straight line nominal flight. I'll try to find some videos of this
phenomenon.
Rick
From: William Claybaugh < <mailto:wclaybaugh2@xxxxxxxxx> wclaybaugh2@xxxxxxxxx>
Date: Wed, 20 Oct 2021 15:04:27 -0600
Subject: [AR] Re: Test Launch
Looking at two videos I see the turn starting around 100-120 feet (based on
the known 24 foot length of the launch tower). I counted 14 frames to
complete the turn. Given the trajectory, this implies the video was shot at
60 frames/second and the turn took place in 0.25 seconds. (At Mach 0.38....)
The vehicle is flying straight and true up to the start of the turn, which
makes a stuck belly band questionable: why didn't it turn as soon as it
left the launcher if a belly band was adding drag to one side? Conversely,
why did it stop turning if not because a stuck belly band coming off?
Similarly, if the sudden turn was due to an internal failure leading to an
off-axis mass asymmetry, why did it straighten out and fly true on the new
heading?
And then there is the telemetry LOS occurring at about the same altitude as
the turn and the subsequent finding that the antenna had snapped off at the
base. For now, I am tentatively assuming that was an effect of the sudden
very sharp turn but I'm open to other suggestions.
All thoughts are welcome....
Bill