Richard,
Thanks for that, and i look forward to seeing what you find. The rail buttons
were new, never been launched, and i had made a point to install them so that
they rotate freely. Before the launch, i was able to easily rotate the button
around the screw.
Sent from my iPhone
On Jul 24, 2019, at 11:01 AM, R Dierking <applerocketry@xxxxxxxxxxx> wrote:
On Jul 22, 2019, at 7:19 PM, Jason Muckenthaler (Redacted sender "jmuck78"
for DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
Unistrut: I probably used the wrong term, I was attempting to refer to a
launch rail (that ROC may or may not have) that has a truss structure with a
rail attached. Yes, the M-impulse was launched on the back row.
The rocket did slide nicely on the rail when we loaded it; the 46 lbs weight
is launch weight with the ~ 10 lb motor (36 lb dry weight).
The shock cord might have been able to damage one of the rail buttons, but I
think it’s unlikely the shock cord managed to damage both rail buttons in
the same way. The main chute did deploy at apogee inadvertently because the
shear pins were too small, so there wasn’t much opportunity for the shock
cord to get tangled up during a free fall.
There is also a small, but noticeable “waggle” visible in the launch video
that could be due to the thrust vector misaligning with the rail direction.
The rocket also seems to have a high spin after the initial waggle
stabilizes.
Here’s the launch video:
https://www.youtube.com/watch?v=K_RToX5yihc ;
On Jul 22, 2019, at 6:59 PM, R Dierking <applerocketry@xxxxxxxxxxx> wrote:
What’s the unistrut rails? The M-impulse went off the back row I’m assuming
and unless the Super Uber was there (and I don’t think it was), there is
only one kind of pad on the back row.
Doesn’t look like drag damage to me. Most of the available rail buttons are
pretty tough and would just plow through the surface of the lakebed. Did
the rocket slide on the rail nicely when it was installed? 46 lbs is a
heavy rocket even for a M. Could the shock cord have caused the damage
during deployment?
Richard
On Jul 22, 2019, at 6:28 PM, Jason Muckenthaler (Redacted sender "jmuck78"
for DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
After retrieving the LOC Hawk on Saturday, I noticed that both rail buttons
had been damaged with very little damage to area immediately surrounding
the rail button locations. My initial, knee-jerk reaction was that the
rail button damage was just another consequence of the rocket being carried
across the lakebed, but on further reflection, I wonder if the damage was
actually caused during the launch. The wind was blowing at a healthy pace
(while still less than the 20 mph limit) and the rocket has quite a large
fin area. The large fin area coupled with a potential torque due to the
nozzle exhaust hitting the blast deflector at an angle, may have been
enough to shear the outer edges of the rail buttons off before the rocket
cleared the tower.
I have attached pictures of the two rail button locations, and there is a
clear lack of road rash in the vicinity. The other possibility is that
the rail buttons impacted something during its trip along the lakebed, but
if that were the case, I would have expected the rail button screws to show
some deflection or some other impact damage - but there is no such visible
damage to the rail button screws.
I am also now curious if I should have used one of the larger unistrut
rails instead of the 1515 rail tripod. I don’t know where the cutoff for
using the 1515 tripod launcher is versus the unistrut rail (and I should
have asked prior to the launch, but it didn’t occur to me until I saw that
rail buttons). Does anyone else have any similar experience with broken
rail buttons like this, or does this look more like damage from wind
carrying the rocket across the lakebed, and I’m just not recognizing it?
Some Data: The Lift off weight was about 46 lbs with the M1297. Velocity
off the rail (according to OR) was about 40 mph.
Greg Smith has a nice video of this torque on his blog from 2016 here:
http://hawtakshun.blogspot.com/2017/01/lucerne-dry-lake-november-2016-l1500-is.html
Thanks,
Jason
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