Don't Debate This, Too

Discussions on mid/high powered model rockets using F powered motors and above.

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OverTheTop
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Re: Don't Debate This, Too

Postby OverTheTop » Mon Sep 24, 2018 1:07 pm

Congratulations Mike! :) :) :) 8)

Great news. I hope it can be recovered without too much hassle.
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Re: Don't Debate This, Too

Postby SpaceManMat » Mon Sep 24, 2018 9:04 pm

Hope you get it back Mike.

I’m a little confused by the report Drew, to drop 38k feet in 2 minutes would indicate no deployment. Also something went wrong going up as it was way too low, but continued transmitting.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Don't Debate This, Too

Postby Passaretti » Mon Oct 01, 2018 5:06 am

We successfully launched at 1:30 PM PT on Friday 21 Sept.

https://youtu.be/Qd7p5JHoY28

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My uncle and I were safely waiting about 3,000 feet away when the rocket was launched and rapidly climbed out of sight into the clear blue sky. Other than a slight angle, which was likely attributed to the pad shifting during motor ignition, the boost looked perfectly straight. I was very relieved to hear nothing but positive sounds during the boost, and a somewhat sporadic but consistent set of tracking signals from the onboard avionics indicated the rocket had survived. The hardest part of this project, keeping my first composite motor case together during a Mach ~4 ascent, was validated quickly and gave me a lot to be grateful for. Finding the rocket turned out to be the hardest part of the trip...

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As it climbed, we tracked the rocket to about 68,000 feet MSL where it was still climbing and was at a range of about 2.3 miles to the East-Northeast. I continued to receive medium-strong signals from the onboard trackers but temporarily lost the GPS data packets. GPS data was required later, when the rocket was descending, at approximately 33,000 feet MSL, at a range of over 5 miles also East-Northeast. Packets came through until the rocket was about 1,500 feet AGL, at a range of over 7.2 miles. The last reported packet was in a very very difficult to access area.

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https://youtu.be/qrOGIW9XnpE
https://youtu.be/WLUBJYEVk9c

The GPS location and time stamps indicated a rapid descent. The entire flight was over in 3-4 minutes, which mean that the rocket fell very very fast, but not fast enough to not receive the last GPS packet about 1,500 feet off the surface. My gut told me that the rocket had come in semi-ballistic, but there were decent arguments to be made for a tangled recovery system. Nonetheless, the only way to find out was to find the rocket, or what was left of it. My biggest concern was not finding anything at all and/or not getting close to the last reported position. Fear of not knowing what happened far outweighed just about any other scenario...

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It took us the following two days and four attempts to finally locate the rocket. The first two attempts, immediately following the launch were direct line of site drives from the launch location but were quickly hindered by massive mounds of playa and deep gullies. On Saturday, we planned an early drive away and around the difficult to access parts. I tried my best with my truck, but received warning lights on Saturday and became concerned about ground clearance and getting stuck miles into the desert without a reliable means to contact anyone.

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The fourth attempt was aided by a local ex-US Marine who drives a Hummer H1 and tows a Polaris General for hunting rockets. With the right tools, you can do anything ... and we drove in a straight 7-mile line ENE from camp, hardly every turning the wheel. It was a tremendously fun, and rewarding ride in the Polaris. We begain a search grid about 9 miles from the launch location, working our way back, but saw nothing until we drove direclty under the last reported position. A few fresh clumps of playa dirt on the surface, zeroed us in on the resting place of the rocket.

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We dug down by hand and found the back of the back of the rocket, in-tact and about 1.5-2ft below the surface. The aluminum tip and about 10 feet of Kevlar shock cord were laying on the surface. We pulled pretty hard on the Kevlar with the shock cord but were unable to get the rocket to budget. Unfortunatley, the Polaris's winch wasn't working and we couldn't pull at a great angle to extract the rocket. In the end, we ran out of time due to our schedules and had to haul ass out of there. I brough the tip with me, which includes the thermocouple logger. I'm hoping to get data off this, although it took a hell of a thump when it hit the ground.

While it sucks to have suffered a ballistic descent, I am very encouraged by the successes we had during this flight. Based on all the information I have right now, I believe drogue parachute became detached sometime after the apogee ejection charges fired and the rocket, which was falling nose down, with the tip/shockcord off to the side, hit the ground. My gut is that it happened when the charges fired and ripped off, or as the rocket fell rapidly and began to hit thicker air and shredded.

There was a serious flaw with this design, which I believe lead to the core of the issues I experienced. Because I was only separating the tip, and ejecting the recovery system from the very end of the rocket, the rest of the rocket was still inherently stable and wanted to nose down during descent. I anticipated this and used a slightly larger drogue, but I did not anticipate the drogue become detached. If anyone's interested, I can explain why I went this route, but it's safe to say, I need to seriously rethink it and likely go back to a more conventional separation method.

I still have another N5800 ... :) DDT3 here we come!

and check out those battle scars!
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Re: Don't Debate This, Too

Postby SpaceManMat » Mon Oct 01, 2018 10:24 am

Well I guess that answers some questions, it’s annoying that some much goes right but one issue and not so good an outcome. Any chance someone at black rock will dig it out for you? I’m thinking there’s still plenty to glean from it even if the electronics are dead, especially examining the motor case.

BTW, where / how was the drouge attached? If it was shreded I would expect to see the lines still attached. Weakest point is usually where the lines attach to the chute, attachemnet point is usually the strongest due to all the lines being combined.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Don't Debate This, Too

Postby drew » Mon Oct 01, 2018 2:43 pm

dat tip. Image Image
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Re: Don't Debate This, Too

Postby Passaretti » Tue Oct 09, 2018 7:14 am

SpaceManMat wrote:Well I guess that answers some questions, it’s annoying that some much goes right but one issue and not so good an outcome.


Annoying, yes, but I'm genuinely happy about the overall results. The fact that the rocket survived the ascent gives me more confidence in my designs and doing it with my first (let alone composite) motor case is another advancement I'm happy about. Having thought through it and looked at the evidence, I think there were at least two single points of failure that could have been avoided. More on this later in the post ...

Any chance someone at black rock will dig it out for you? I’m thinking there’s still plenty to glean from it even if the electronics are dead, especially examining the motor case.


Agreed. There is a ton that could be gleaned from just seeing the what's left of the rocket. I'm going to dig it out myself, next year, right after I recover DDT3 :) Judging by the tip, the Mach scars on the airframe must be really cool!!


BTW, where / how was the drouge attached? If it was shreded I would expect to see the lines still attached. Weakest point is usually where the lines attach to the chute, attachemnet point is usually the strongest due to all the lines being combined.


The drogue was attached to a swivel, and then a Rocketman recovery blanket, using one of it's welded D-rings which are sewn on. There is one on either side the recovery blanket. The other D-ring was attached to a clasp, as was the Kevlar shock cord; the clasp was attached to the NC tip U-Bolt.

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I thought the Kevlar sewing on the blanket was solid based on the way it was stitched and my experience with RM's products. But this may have been a poor assumption. The D-ring that was attached to the clasp, was all that remained. See below. The only way this could happen is if the sewing or the blanket material itself completely failed.

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So yea, there were avoidable single points of failure in the way I attached the drogue. Either of the D-rings could have been ripped off, one clearly did. The drogue/swivel should have been attached directly with its own clasp or quick-link to the NC tip U-bolt as should have the shock cord. I did not attach it this way because it was extremely hard to get the drogue to pack into the airframe, and leave room for the NC tip shoulder to fit. I don't have

Here is one of the test packings I did earlier on which was a lot harder to get to fit into the rocket.
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The ejection cannons take up a fair bit of room which makes it difficult to fit the drogue. The actual packing for the flight was even tighter that what is pictured here.
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Here is what the rest of the recovery system looked light the night before the launch, before it was inserted into the rocket.
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I can't say for sure, but I believe the drogue became detached from the NC tip not long after separation event. I'm now considering that it never made it out of the rocket at all. The D-ring may have been ripped off, leaving the drogue behind int he rocket when the tip separated. There could have been a considerable amount of force on the drogue attachment points when the primary apogee event (80-second timer) fired. The drogue/blanket burrito would have required at least a few lbs of force to pull it out, the ejection cannons were basically butted up against the circumference of NC tip shoulder. The shock of the sudden yank of the NC tip coming out may have been too much.

The tower kicked on lift-off, which resulted in a ~5ish degree launch angle and a slightly higher than anticipated lateral velocity. However, at the estimated apogee altitude, the effect of air resistance should have been negligible, even with a few second late deployment.

My initial hunch was that the drogue separated during descent when the rocket hit the thicker air, which I think is still a plausible scenario. However, there is no way of knowing more ...until I dig up the rocket.

So now on to the fun part of what I've learned over the past week or so ... 2nd post to follow shortly
Mike Passaretti, TRA 5369

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Re: Don't Debate This, Too

Postby Passaretti » Tue Oct 09, 2018 7:43 am

Back in 2013 at BALLS, when I was going to attempt a repeat flight of DDT1, I purchased and installed a thermocouple logger to record the aluminum tip temperature during flight. Unfortunately, that flight got scrubbed due to issues with my backup tracking system and impending weather.

I was so busy getting this build ready this year, that I didn't consider installing it until the very final days before I had to hit the road. Long story short, it made the flight and I was able to recover the data, despite the NC tip hitting the ground very very hard. Though the primary goal was to extract temperature data to inform future high Mach designs; in light of the anomalies I experienced, the timing of the data that was returned is far more interesting at this stage.

Here is what the original product looked like before I modified it for DDT2
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And halfway through modifying it to fit in the Al tip.
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And finally what it looked like before it was installed
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And what it looked like installed
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And what it looked like post-flight after some surgery to remove it. Note the battery connector has disintegrated and is no longer connected.
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And what it looks like sitting on my desk right now
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Here is the raw data, with a timeline, included above. The top chart shows all of the recorded data points, at the full vertical scale. The bottom chart has a shorter vertical scale.

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The temperature readings show an underlying and reasonable set of values that seem to measure ambient temperatures. However, there are several anomalous and unexplainable spikes i.e. noise. Setting all those aside, for now, the timing of the 1Hz readings are very interesting and may help us to piece together what happened.

Throughout the data, the anomalous temperature readings seem to correlate to vibration or electrical noise from handling of the rocket throughout the morning and into the afternoon before the rocket was launched. I have several photos from the day who's timestamping can help verify what was happening.

Once the rocket was in the tower the readings were steady and appear to again measure ambient temperature. The following readings, around the time of ignition, get very interesting. There is an anomalous spike, which may be motor ignition, followed by 80 seconds of clean data then another anomalous spike which should be Pyro D. Several 10s of seconds later the log stops abruptly which may be explained by the battery connector exploding on ground impact which I found clear evidence of.

Here is just the data from when the rocket as in the tower. The top chart uses the full vertical scale; the bottom a shorter scale to see the ambient readings better

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What this may mean is that we know exactly when the rocket took off, had an event and hit the ground. The data indicates a flight time of approx. 191 seconds. This is consistent with my initial estimate from the flight video time stamp and the timing of the last APRS packet, 180-240 seconds. Working backward from 191 seconds and the 2 sets of anomalous readings during the course of the flight provides key data points that may be used to describe the trajectory and also potentially verify what the flight computers were doing.

IF, the spikes are in fact launch and Pyro D firing and the end of the data is ground hit, there is decent evidence that supports the rocket went at least 90kft AGL. This is because Pyro D, the primary apogee event, was designed to fire at T+80 seconds ONLY IF the rocket exceeded 90kft first.

I've run multiple OR simulations varying launch angle, surface roughness of the rocket, and average winds while trying to achieve the flight time as indicated by the logger data and the actual lateral distance traveled by the rocket. The goal is to estimate the actual altitude. So far all things indicate it likely went to around 100kft or better, but I have more work to do...
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Re: Don't Debate This, Too

Postby Scoop1261 » Tue Oct 09, 2018 9:21 am

Awesomely cool stuff.......and to think that this all started over about two dozen Corona's in a rocket room in the backyard of a house in Western Australia! :D
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Re: Don't Debate This, Too

Postby Passaretti » Wed Oct 10, 2018 6:25 am

Scoop1261 wrote:Awesomely cool stuff.......and to think that this all started over about two dozen Corona's in a rocket room in the backyard of a house in Western Australia! :D


That's just not true ... There were wayyyyy more Corona's drank than two dozen! :D
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Re: Don't Debate This, Too

Postby SpaceManMat » Fri Oct 12, 2018 7:57 pm

Far too cool 8)
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing


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