Chris' Punisher 4 L3 build

Man sorry to hear that Chris, this has been a beautiful build. Look forward to the rebuild, your are mechanically awesome, so this is a testament that it can and will happen to anyone.

Glad to hear your positive and the expensive stuff survived

I'm amazed at rocket remains when an anomaly happens. One thinks they have "good" stuff that can take extremes and are rudely awakened when a major glitch occurs. You've found out the utility of GPS recovery in an extreme situation as did
I outlined here: https://www.rocketryforum.com/showt...-Mapping-Program-Update&p=1573624#post1573624
It's really something to dejectedly go out to that last known position and by golly you find something! Looks like all you need is a new nosecone? Um, I'd ditch that RRC2 and go with something else out of personal paranoia if I were you for the
next attempt. I can't recall, did the ebay freefall? If it did, I'd do a test flight in another rocket with the TeleMetrum to make sure it wasn't damaged. If it came down under a chute, perhaps not necessary. Kurt

Kurt,

Yes, the ebay freefell from 11,100' and hit the ground at about 80 mph. I fired up both altimeters and the camera and they all seem to be working. I'll probably try flying them in something fairly low and slow before I trust them in a big bird again.

This pair of altimeters flew to 1200mph last summer, so I'm pretty positive that it was the ebay configuration and not the electronics. I would like to get an accelerometer based altimeter to use as the backup next time.

Chris,
Sorry about your mishap. I saw the J449 shake down flight and that is a beautiful rocket. Thank you for posting your data and findings. It will teach others like myself who have or are working on Punisher 4s. The Telemetrum pressure data is flat starting at 3.5 s which looks like burnout from the velocity data. Then the separation at 6.5 s. The pressure curve started flattening out as the rocket went transonic at 2.25 seconds, so I am wondering if the pro-longed flat pressure fooled the RRC2+ mach inhibit. The simulations I have would put the Punisher 4 at around 3,500' AGL at M1297 burnout, so the pressure data seems low given TCC is only ~200' MSL. It is as if a bow wave sat over the vent holes and held the AV bay pressure constant for over 3 seconds as the rocket continued to rise. Curious to hear what you find. Good luck on the rebuild.

I am extremely curious what would happen on this same flight, only without the camera shroud.

Several times older rocket guys told me to expect problems on my original Punisher, due to the vent holes being so close to the nose slope. I never did, and have never heard of anyone else having any, but maybe the push to four inches, additional thrust, or combination of the two pushes it over the edge.

How close to the nosecone edge are the vents to the altimeter bay? Any kind of edge at the junction?

I ask as I have always considered this a questionable design.

Chris
Sorry to hear about your flight. With that kind of drogue deployment I don't think any chute can take something like that. It held up very well I think. It takes a lot of force to pull that swivel the way it did. I use Kevlar only to the top of the booster than go with tubular nylon. Now you know Kevlar will break. Because of your building skills the rocket lives to fly again.

These were 2" below the NC. There wasn't any step at that point. I sanded the NC and vent band to make sure there was a smooth junction.

One thing I wanted to point out is that the aluminum tie rods and 10-32 screws held up fine to the shock load. The altimeter bay was found basically intact.

There were a good number of Punishers that flew at MMWP last Weekend I don't think anyone is having a problem with vent hole placement.

No problem at all with vent holes.

Chris, did you have a vent drilled into the nosecone?

Did you use shear pins in the booster

Sorry for the bad flight! Like Justin said. Amazing lift off pics!!!!

So sorry to hear about this, Chris! You were a great support in my L journey. I offer my encouragement to you now. Thank you for sharing the details of your flight, so we may all learn from them.

Ari.

I have one 3/32" hole in the nose.

I had one rivet between the booster and the ebay. There were 3 between the ebay and the nose. They take about 80lbs each to shear.

GRIFFIN said:

No problem at all with vent holes.

Chris, did you have a vent drilled into the nosecone?

Did you use shear pins in the booster

Sorry for the bad flight! Like Justin said. Amazing lift off pics!!!!

Click to expand...

Did you somehow close the holes for the wires in the aluminium bulkhead?
Otherwise I think that a movement of internal components relative to the rear part of the rocket at burnout created a pressure increase.
If the camera mount would be the problem the pressure problems should occur when you hit mach, not at burnout.
The bump at 2.25 is the mach transition and the pressure problem starts right after burnout at 3.5.

This area of the rocket shows a negative dynamic pressure. (See the simulations here: https://rocketguy101.jimdo.com/rocket-pictures-7-cfd/)

If the rocket decelerates, the dynamic pressure will increase while the static pressure of the ascending rocket will decrease. It would be an interesting little research project, to find out how big those two effects are in comparison, but for fast rockets with high dynamic pressures, I wouldn't be surprised if this can fool an baro-only altimeter.


Reinhard

The holes for the wires were sealed with tape.

thomas said:

Did you somehow close the holes for the wires in the aluminium bulkhead?
Otherwise I think that a movement of internal components relative to the rear part of the rocket at burnout created a pressure increase.
If the camera mount would be the problem the pressure problems should occur when you hit mach, not at burnout.
The bump at 2.25 is the mach transition and the pressure problem starts right after burnout at 3.5.

Click to expand...

ChrisAttebery said:

One thing I wanted to point out is that the aluminum tie rods and 10-32 screws held up fine to the shock load. The altimeter bay was found basically intact.

Click to expand...

You did a good job verifying the integrity of those load paths. Still amazing the forces that that drogue put on the hardware. Software and Kevlar appear to be the weak links.
I'm hoping you have a viable video from your onboard camera.

I'm still trying to understand what components arced so wide across the sky after the early charge fired. It would seem the booster would no longer be stable without the mass in front... unless it decelerated in a backwards orientation with the blown out drogue providing drag stability. I definitely saw a wide smoking arc from my perspective.. perhaps what looked like and arc to me was the booster/drogue deceleration and fall with a smoldering motor. Did you find the chunk of the motor nozzle that was missing, as in proof it broke on impact?

ChrisAttebery said:

The Telemetrum data shows that about 6.5 seconds into the flight there was a pressure spike in the altimeter bay and the RRC2+ fired it's Drogue charge. At that point the rocket was traveling at ~670 mph.

The altimeters both appear to have survived the plummet from 11,400'.


View attachment 291782

Click to expand...

Chris,
Hope you don't mind a few questions...
In your altimeter plot, does the end of the plot correspond to "on the ground"? I see speed near 0, but don't understand why pressure seems significantly low at 77kpa... but the line is flat at the end. I would expect 101Kpa on the ground, yes? I'm trying to interpret what I saw (and remember) with the data plotted. Perhaps you've zoomed into the "event" area of the full data set, given the short amount of time plotted?
Thanks.

Subscribed for knowledge

Thanks Ari. I'll be back at it soon enough. If I wasn't so busy this week I'd probably already have started on the rebuild.

iter said:

So sorry to hear about this, Chris! You were a great support in my L journey. I offer my encouragement to you now. Thank you for sharing the details of your flight, so we may all learn from them.

Ari.

Click to expand...

I'm sure that the booster continued to travel upward for a while trailing what was left of the drogue. I'm sure that's what caused it to spiral as it went up.

I did not find the chunk of nozzle. I didn't even look for it. I got 3-4 affirmations that the ground bounce probably broke it so I wasn't worried about it.

kevinkal said:

You did a good job verifying the integrity of those load paths. Still amazing the forces that that drogue put on the hardware. Software and Kevlar appear to be the weak links.
I'm hoping you have a viable video from your onboard camera.

I'm still trying to understand what components arced so wide across the sky after the early charge fired. It would seem the booster would no longer be stable without the mass in front... unless it decelerated in a backwards orientation with the blown out drogue providing drag stability. I definitely saw a wide smoking arc from my perspective.. perhaps what looked like and arc to me was the booster/drogue deceleration and fall with a smoldering motor. Did you find the chunk of the motor nozzle that was missing, as in proof it broke on impact?

Click to expand...

That plot was only a small portion of the data immediately surrounding the event. The full plot was about 1.5-2 minutes long.

kevinkal said:

Chris,
Hope you don't mind a few questions...
In your altimeter plot, does the end of the plot correspond to "on the ground"? I see speed near 0, but don't understand why pressure seems significantly low at 77kpa... but the line is flat at the end. I would expect 101Kpa on the ground, yes? I'm trying to interpret what I saw (and remember) with the data plotted. Perhaps you've zoomed into the "event" area of the full data set, given the short amount of time plotted?
Thanks.

Click to expand...

Thanks Chris.

I've been thinking about rebuilding this project this week. I have a couple new goals in mind:

1. Reduce the amount of ballast in the nose cone. (53oz)
2. Make the use of the camera optional.
3. Mount the camera in a completely separate bay *sealed* from the altimeters.
4. Separate the camera bay away from the altimeter bay by at least 12".

I'll move the altimeters back to my original altimeter bay. Below that I'll add another 18" section of body tube. Below that I'll add the existing camera bay.



The sims show that the overall weight and apogee are almost identical to the original version. All I need is a new nose cone, and an 18" section of 4" tubing. I'll make a 4" bulkhead to seal the altimeter bay from the camera bay and a new shroud for the camera. It shouldn't be more than a few hours work to get it back into flying condition.

ChrisAttebery said:

3. Mount the camera in a completely separate bay *sealed* from the altimeters.
4. Separate the camera bay away from the altimeter bay by at least 12".

Click to expand...

Are you thinking the camera electrically interfered with the altimeter, or is there some other motivation there?

No, I think the camera shroud caused a barometric disturbance that triggered the RRC2. Both Altus Metrum and Missile Works said that the barometric pressure curve was unlike anything they've ever seen.

ChrisAttebery said:

No, I think the camera shroud caused a barometric disturbance that triggered the RRC2. Both Altus Metrum and Missile Works said that the barometric pressure curve was unlike anything they've ever seen.

Click to expand...

Have you compared your data to the previous flight that also had the shroud?

Yes, but the previous flight only reached 360 mph.

What kind of camera shroud was it? And I'm assuming it must've been in line with a vent hole? Forgive me if this has already been asked or stated...

The camera bay work starts on post 101.

noffie79 said:

What kind of camera shroud was it? And I'm assuming it must've been in line with a vent hole? Forgive me if this has already been asked or stated...

Click to expand...