Falcon 54 extreme minimum diameter build

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Given you can't easily dump the eeprom file from your flight off your Telemetrum your best bet is to perform quite a granular analysis of the telem file from your phone. So email yourself the telem file stored on your phone and then replay the flight in AltOS on your computer. I normally only ever deal with TeleGPS from a telemetry perspective but I expect you can "see" the Apogee and Main charge status in the flight replay. Given your issue was with your apogee charge not separating the rocket (?) you should be able to see the charge lose continuity in the replay just past apogee.

Also, to confirm, your apogee charge fired but didn't separate the AV bay/NC from the airframe? And yet you still had NC sep with the main charge while coming in ballistic? That definitely sounds like an apogee charge issue that you can most likely eliminate as altimeter based if you replay the flight. It would also eliminate any suspicion regarding gees causing your apogee charge to lose continuity as I expect if that was an issue it would have occurred during boost.

Finally, maybe next time change the call sign on your TeleMetrum? When you leave the settings as default you're opening yourself up to overlap if someone else is also operating with the same call sign and channel. Years ago we had a guy frantically running up and down the flight line yelling at people who owned TeleMetrums to turn theirs off as he was racked up ready to launch and his base station kept reporting the rocket had landed. Come to find our another club member was leaving in an RV with their TeleMetrum still chirping away post flight. It was quite the funny scene.

Where do I find the file to send myself? I didn't think the phone recorded the data. I have an android.

I just asked those at my club before I set up. The next one I buy I will do that.
 
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Sorry, but from these series of comments, this more and more sounds like pilot error (lack of understanding the electronics). Maybe a few more mild flights with the Altus Metrium hardware/software would help before you build another screamer.
 
Where do I find the file to send myself? I didn't think the phone recorded the data. I have an android.

I just asked those at my club before I set up. The next one I buy I will do that.

The AltusDroid app would have definitely recorded your telemetry output. AltOS does the same when you're on a computer. It's a killer feature imo as when you have a flight mishap the last thing you want to have to do is remember to manually write out your telemetry session. Better to just have it automagically recorded on your chosen ground station. Tip of the hat to Keith and Bdale for that feature. Having any telemetry data from a flight failure is invaluable from a root cause of flight failure analysis perspective.

I use the "Files" app which I believe came with my Pixel 2 to access my internal filesystem on my phone. Here's the steps I took.

1) Tap on the three dot icon on the top right of the app after opening it.
2) Tap "Show internal storage"
3) Now tap on the hamburger icon on the top left of the app.
4) Tap on your phone name (below it should list the free space on your phone)
5) You should now see a listing of folders in the root directory of your phone. Tap the TeleMetrum folder
6) Your telemetry file should be in that folder and its name should start with the date you launched.
7) Select your telem file and share it to yourself via email (assuming your phone has email configured)

You should be able to use almost any file explorer app to do this (eg ES File Explorer) but Files came on my phone so I just use it.
 
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Sorry, but from these series of comments, this more and more sounds like pilot error (lack of understanding the electronics). Maybe a few more mild flights with the Altus Metrium hardware/software would help before you build another screamer.

This was the 9th flight of this Telemetrum, no issues before this, and many other DD flights prior. I am still learning all the details though. I know how to set it up for flight.
 
That coupler extended pretty far into the airframe. I am not sure what others get away with, but as a piston, unless the vent hole was plenty big, and if the charge was not at full power, that much length would create a bit of vacuum which would cause resistance to the separation.


That is a sinking feeling, walking up to a newly built bird sticking in the ground like that.

It would require the outside air to be higher pressure than the air inside the rocket for a vacuum to exist. Considering it was at roughly 32,000 ASL, I doubt that would be the case. The vent hole was 1/16" as there was only 4" of space to actually vent.
 
Air pressure should have been equalizing somewhat from the vent hole, at apogee, that is what it is there for. If there was only 4" of internal cavity, that coupler looks like it inserts into the airframe more than 4", maybe 5"? If you had any sort of tight fit at all, and if the charge was insufficient for whatever reason, which is what I think, then there could easily be a fairly strong vacuum as the coupler tried to eject, if the shear pins were even cut. A piston in a small, long bore will create vacuum as it is pulled out. I think that a different style of ejection charge may have separated your rocket. Of course, too many variables for me to know for sure. I have just been designing a 54mm vehicle, and this is one of the things I have observed. Personally, I would not design with that much overlap in the coupler to airframe. But then, I would not use tip to tip, nor CF plate for an L935 54mm flight, either. I had a flight go very similarly to what yours did. on a 4" rocket. I know why mine did not separate, and it was not the altimeter.

Is 1/16" diameter too small for a vent hole for such a small volume of air that has to quickly expand by more than 100%? In my own design, I started slightly smaller than 1/8" diameter, but was uncomfortable with how much resistance the piston effect gave the nosecone, and the velocity of the air going in and out of the hole when the coupler was going in and out. And the space in the airframe in mine is about 7", so the 'cushion' is even greater than with yours. It is now enlarged to 9/32", and I am more comfortable with that. I think smaller spaces may sometimes need a larger vent, not smaller. When I saw the pic you posted of your completed rocket laid out on the deck, I wondered if it would be problematic because of how far the coupler went into the airframe. I was thinking about those relationships in my own design at that exact time, which is where my questioning of that came from.
 
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What's your method?

.125" G12, meticulous prep, Fillets using carefully weighed Aeropoxy ES6209 with some colloidal silica and milled CF tow that has been extensively mixed into the 'Part A' prior to adding hardener, then placed in a vacuum chamber for 5 minutes to remove air bubbles prior to using. At a .5" radius. ( I noticed that the vacuum reduces air bubbles in the epoxy by quite a bit)

Mine has not flown yet, so I have not seen that it did not shred. I looked around a lot at flights that survived, and how they were constructed. Sims on my (similar) rocket show that the time above mach 1.5 is around 5 seconds. Above mach 2, less than half of that. Above mach 1, only about 12 seconds.
 
Just as an aside, I built a CF 54mm Mongoose stock, using the fins (CF plate) and epoxy that came with the kit. Nothing else. Flew it on an L935 to 23,500', hit about Mach 2.4. Other than bubbling the paint on the fins, it held together just fine. In my experience, long as the fin design is rational for a plus Mach flight and they are properly aligned, they shouldn't need a lot of reinforcement. I built a second version that is shorter but with the same methods that I'll fly again at BALLS this year, also on the L935.

I don't have any exceptional building skills or use exotic techniques. So far I've never shredded a rocket, even at Mach 2+ on several flights. I think as long as it's a proven fin shape and is the right material (strength), extreme construction techniques do not seem to be needed.

...<snipped for brevity>....If you had any sort of tight fit at all, and if the charge was insufficient for whatever reason, which is what I think, then there could easily be a fairly strong vacuum as the coupler tried to eject, if the shear pins were even cut...<snipped>...
I have to completely disagree with your assessment. If the ejection charge goes off, it will create positive pressure in the compartment. The idea that you could then create a vacuum as the two separated seems to defy the law of physics. Where did the gas created by the charge go? If the charge was strong enough to break the shear pins that can only be done by generating a large enough volume of gas to create enough force to do so. There might not have been enough energy to overcome the friction of a tight fit, but certainly not because it created a vacuum. Expanding gas and a vacuum seem to be incompatible.


Tony
 
I have to completely disagree with your assessment. If the ejection charge goes off, it will create positive pressure in the compartment. The idea that you could then create a vacuum as the two separated seems to defy the law of physics. Where did the gas created by the charge go? If the charge was strong enough to break the shear pins that can only be done by generating a large enough volume of gas to create enough force to do so. There might not have been enough energy to overcome the friction of a tight fit, but certainly not because it created a vacuum. Expanding gas and a vacuum seem to be incompatible.


Tony

My concern was if the charge is insufficient for some reason, as I mentioned in my comment. In ground testing, I have seen shear pins torn, but incomplete separation. If the charge is sufficient, of course the expansion of gasses will pop the nosecone right off, just like a bullet from a barrel. A possible reason for insufficient expansion in a charge might be a type of charge that had difficulty at altitude. It sounds like that could have been the case. The charge would have been the fault, not necessarily the 'vacuum theory' I put out. I just saw that as adding to the risk of no separation in a case of problems with the ejection charges. And yes, friction is part of all that, too. My main point was that I think the coupler went too far into the airframe. No? I do not know where it is, but there is a point where too much coupler depth into the airframe is going to start causing an increasing risk of no separation. I like 'enough', and not more.
 
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Just as an aside, I built a CF 54mm Mongoose stock, using the fins (CF plate) and epoxy that came with the kit. Nothing else. Flew it on an L935 to 23,500', hit about Mach 2.4. Other than bubbling the paint on the fins, it held together just fine. In my experience, long as the fin design is rational for a plus Mach flight and they are properly aligned, they shouldn't need a lot of reinforcement. I built a second version that is shorter but with the same methods that I'll fly again at BALLS this year, also on the L935.

I don't have any exceptional building skills or use exotic techniques. So far I've never shredded a rocket, even at Mach 2+ on several flights. I think as long as it's a proven fin shape and is the right material (strength), extreme construction techniques do not seem to be needed.

I have to completely disagree with your assessment. If the ejection charge goes off, it will create positive pressure in the compartment. The idea that you could then create a vacuum as the two separated seems to defy the law of physics. Where did the gas created by the charge go? If the charge was strong enough to break the shear pins that can only be done by generating a large enough volume of gas to create enough force to do so. There might not have been enough energy to overcome the friction of a tight fit, but certainly not because it created a vacuum. Expanding gas and a vacuum seem to be incompatible.


Tony

Exactly! The hot gasses do not disappear and the length of the coupler would create a comparatively tiny vacuum. When I tested it with 1 gram it shot off with a lot of energy, so I added .2 grams more for a safety margin.

I want to make the fins thinner to reduce drag for the L record, so I need to do the lamination to hold the fins on.
 
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Why not the L2050? That is where your record is.

I tried that, the extra mass of propellant, casing and body tube, as well as the extra drag from the length makes it only sim to about 31,000 feet with 0.09" thick fins, before I removed the tailcone closure from the design. I get 36,000 with the L935.
 
I wonder why your sim is so different than mine. I just sold that motor hardware yesterday, decided that I did not want to build it, but I think it should sim well over 40k. My sims show 46k and M2.7. And that was with .125" fins.
 
After watching the flight replay from the data sent to my phone, the apogee charge did loose continuity. I think this means the charge did go off, it just didn't separate the air frame. The only way for that charge to not have separated the airframe would have been for not all the BP to go off, or the coupler could have bound up inside the airframe, though I doubt that.
 
I wonder why your sim is so different than mine. I just sold that motor hardware yesterday, decided that I did not want to build it, but I think it should sim well over 40k. My sims show 46k and M2.7. And that was with .125" fins.

Huh... odd. What is the mass of the rocket?
 
After watching the flight replay from the data sent to my phone, the apogee charge did loose continuity. I think this means the charge did go off, it just didn't separate the air frame. The only way for that charge to not have separated the airframe would have been for not all the BP to go off, or the coupler could have bound up inside the airframe, though I doubt that.

When you did your ground tests did you take into account "BP's high altitude issues? IIRC you're in Colorado? 4000' launch site elevation? 27000+' flight puts you in the "is it gonna work zone.
Describe your apogee's ejection charges.

Tony
 
Sorry to hear about your impact with the ground, At least you got to see the results up close and personal. It's amazing what that much force can do to rocket parts. I still have the 9volt from my 1st altimeter lawn dart. Good luck on your next attempt. You've got a lot of help here going in the right direction.

I wonder why your sim is so different than mine. I just sold that motor hardware yesterday, decided that I did not want to build it, but I think it should sim well over 40k. My sims show 46k and M2.7. And that was with .125" fins.

Sorry to see you sell that Chris. I see it sold in record time. ;-)
A customer flew a sub MD with the L-2050, machined the case down .020" where the CF fin can was laid up so as not to increase the airframe OD more than 2.127". No idea on the fin thickness, just that they were 4 really small fins and it was flown out of a tower. TeleGPS altitude was 39,126 and max speed around M3.05.

If the L-2050 is too long and fast, there's always the 3,707Ns L-1040 Loki Red. ;-)
 
Not quite, the raw ripstop wont work very well, it needs to be coated with something like a silicone waterproofing. That being said I have tried other materials and while they will work they are nowhere near as good or easy to use as purpose made peel ply, perforated peel ply or release film. In a pinch other things might work, but best results are gained from the proper material.
Straight from Aeropoxy FAQ: A number of types of peel ply materials are commercially available. These include, Teflon coated fiberglass fabric, fiberglass fabric coated with other release agents, as well as coated and uncoated nylon fabrics. Some AEROPOXY users have had good results with very tight weave Dacron fabric purchased from sewing centers and retail fabric shops.
 
Sorry to hear about your impact with the ground, At least you got to see the results up close and personal. It's amazing what that much force can do to rocket parts. I still have the 9volt from my 1st altimeter lawn dart. Good luck on your next attempt. You've got a lot of help here going in the right direction.



Sorry to see you sell that Chris. I see it sold in record time. ;-)
A customer flew a sub MD with the L-2050, machined the case down .020" where the CF fin can was laid up so as not to increase the airframe OD more than 2.127". No idea on the fin thickness, just that they were 4 really small fins and it was flown out of a tower. TeleGPS altitude was 39,126 and max speed around M3.05.

If the L-2050 is too long and fast, there's always the 3,707Ns L-1040 Loki Red. ;-)

Okay, now I am getting really good sims from these. 47k from the L2050. I think the motors are starting to get more out of my price range though. for 47k I would also have to change to a CO2 ejection system and have to fly out of BALLS or at Argonia KS. I paid about the same for my M2550 for my L3 as that motor costs. I definitely want to do this project, though with college and how much I am making now I do not think that is really possible. I have everything I need for my L3, but I would need to spend a good $1000+ more to make another one of these with changing over to the L2050. The L935 has increased to $236 and the case and closure are $150 and I need to buy a new TeleMetrum which is $300 and a Raven $155. I have another 34" fiberglass tube and a bunch of the fins cut that I can use.

Then again, I can put together a project proposal for funding to my school to see if I can attempt this 47k flight. I have demonstrated the ability to build something to fly at mach 2.36 and survive, at least not yet recovering, but I know what to do differently. Maybe they will pay to let me fly to mach 3.35 and 47k. If I can get funding I will definitely document that on the forum, if not this will have to wait a bit.
 
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