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
<mailto: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
<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fhawtakshun.blogspot.com%2F2017%2F01%2Flucerne-dry-lake-november-2016-l1500-is.html&data=02%7C01%7C%7C9eaf0f7cf6124a195c7908d70f0d11a7%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636994421126047991&sdata=gpolkN4HKFL%2B3qOmAWYlxo8iD4qAD2QTluaHg6Z0c2M%3D&reserved=0>
Thanks,
Jason
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