Near Miss- Please read

[roytyson]

So I had a near-miss that could have resulted in a much different situation. One that could have had many injuries or damage to my body.

First off, I take full responsibility for my lack of understanding of what happened, so "those" post can stay inside your head, I just wanted to share.

I have ground tested nearly 20 rockets in the past 3 years of flying high power. But up tot his point, I have run exclusively Eggtimer stuff and done it all via wifi. Earlier this year I bought a BT60 Mach 1, Star Cruiser with SMT sled. At the time (and probably still currently) the Eggtimer was not an option. So I got a sled with a Perfect Flight Strattologger. I knew I would need to test with a shop vac, so after many hours of reading, I decided I was prepared to do this.

I first tested the drogue. Hooked the shop vac up, and everything was good. Turned it on, when it deadheaded, deployed, Perfect.

I then slide the rocket all back together, prepared for the main. Here I where my mistakes started. I taped over all the vent holes (before I started) in the AV bay except the one for the shop vac hose. What I didn't consider at the time when I slide the av bay and booster back together, I did not align the vent holes. So when I was prepared to test the main, I set everything up and turned on the vac. I let it pull a vacuum for 20 seconds, then turned it off, expecting it to deploy the main. Nothing. I cycled through this 3 times before I concluded something was a miss. After disconnecting the vac hose, I picked up (mistake #2) to turn off the AV switch. When I picked it up, the AV bay slides out of the booster section less than 1/4" (mistake #3). As this happened the nose come was pointed straight up (thankfully) and the main deployed. SCARED THE CRAP OUT OF ME!!!. His happed with the rocket about 18" away from my face (mistake #4).

What I concluded, unless some can assist me in a different thought was, since the holes were miss-aligned on the vac hose, it held vacuum until the AV bay slid out, or at least long enough the vacuum pressure bled off which just happened to be when I picked up the rocket....resulting in the electronics working as designed and deployed.

I was lucky, I see that. I made some safety errors, I also see that.

I just wanted to share to hopefully prevent a potential injury of someone else.

Thanks

 

[Eric]

Thank you for sharing your incident with us. There is always something to learn with this data.

I believe you are correct on your assumption of what went wrong. Those Mach1 couplers and body tubes fit very tight together, and I could see it holding a vacuum for a short while.

I'm glad you came out of it uninjured and learned from your pointed out mistakes.


Side note. Why was the Quantum out of the question for this kit? I use a Quantum and Raven3 in the few Mach1 BT-60 kits I have.

 

[roytyson]

Thank you for sharing your incident with us. There is always something to learn with this data.

I believe you are correct on your assumption of what went wrong. Those Mach1 couplers and body tubes fit very tight together, and I could see it holding a vacuum for a short while.

I'm glad you came out of it uninjured and learned from your pointed out mistakes.


Side note. Why was the Quantum out of the question for this kit? I use a Quantum and Raven3 in the few Mach1 BT-60 kits I have.

At the time, I wanted to try an SMT sled, and Eggtimer boards are all too big for that AV bay. I have another rocket of the same size where I made my own sled and have a Quantum in it.

 

[mbeels]

Thanks for posting, that is an experience others can learn from.

 

[BF Rockets]

If you want to test the firing of the Strato Logger by pulling a vacuum you can do that with just ematches and no charges. If you want to test the strength of your charge sizing, you can perform a second test, and fire the ematch remotely by running the ematch out of the vent hole, and connecting it to an Estes controller with 25 or 50 ft of cord.

 

[Cameron Anderson]

What BF Rockets said...vacuum testing is a very poor analog for flight, but it'll set your charges off absent a test-mode function. Just run the e-match external, remove sources of error (the altimeter and the vacuum and all subsequent issues like alignment) and power the e-match directly to assess ejection charge size.

 

[mbeels]

I think that there is still value in doing an integrated vacuum and deployment test. I like to check for pressure spikes in the recorded data (as altitude dips) which indicate that pressure from the charge is getting into the AV-bay. If that is happening, BP residue is getting into the electronics and can cause corrosion problems down the road.

 

[Cameron Anderson]

I think that there is still value in doing an integrated vacuum and deployment test. I like to check for pressure spikes in the recorded data (as altitude dips) which indicate that pressure from the charge is getting into the AV-bay. If that is happening, BP residue is getting into the electronics and can cause corrosion problems down the road.

I like sealing the charge side e-match hole of my bulkeads with hot glue and gorilla tape on the inside.

 

[Bat-mite]

Glad you are okay! FWIW, I always test my altimeters in a jar with LEDs, and do my ground testing with an Estes controller from 30 feet away. The vacuum method seems prone to things like you experienced.

 

[rharshberger]

+1, I use Christmas tree bulbs ( incandescent minis), and a Foodsaver marinating container, its easy to simulate 30k feet, and see if both channels fire/light up. For the charge testing its wires through static ports and the charges in their charge holders, Estes PS launch controller from 30' away.
Definitely glad you are okay, it was defintely a close one.

Glad you are okay! FWIW, I always test my altimeters in a jar with LEDs, and do my ground testing with an Estes controller from 30 feet away. The vacuum method seems prone to things like you experienced.

 

[aerostadt]

I like testing electronic ignition with a light bulb in place of an ignitor/e-match. I got the light bulb from Radio Shack years ago. I can bench test again and again, until I feel good about what is happening.

 

[Zeus-cat]

I'm glad you weren't hurt. Thanks for sharing as it is a good reminder that bad things can happen very quickly when using this kind of stuff.

When I test using live charges I wear safety glasses. I have never used a vacuum as I prefer not to be standing next to a rocket knowing charges will go off. Like Bat-mite and rharshberger I wire up the charges and stand clear when firing them.

 

[swatkat]

Glad you are OK. I'm in agreement as well on the failure mode. Quark and quantum both fit in the BT-60 sleds from SMT, just need to swap out the center/flat mounting plate for the one appropriate. I have one with a quark and one with a quantum for my speed demon BT-60

 

[cwbullet]

Good you are ok.

It happens. I have significant hearing loss on the left due to something similar. I now point it away from my head and using heating protection.

 

[David Schwantz]

Hi Roy, glad all ok. You said that you misalignned the vent holes. Are your vent holes not in a switch band? I have also run no switch band on mine,, but I always have alignment pins and sockets for the parts to go back together as desired. This avoids any misalignment problems.

 

[roytyson]

Hi Roy, glad all ok. You said that you misalignned the vent holes. Are your vent holes not in a switch band? I have also run no switch band on mine,, but I always have alignment pins and sockets for the parts to go back together as desired. This avoids any misalignment problems.

I originally set it up for two shear pins. But decided to back that down to one. I was using that hole. And yes. No switch band.

 

[Nick@JET]

Thank you for posting, honestly I would not have thought of that either. It’s big of you to post this as we all learn, gladly you where not hurt.

I also now test under vacuum with Ematch only - then separately the eject charges on a switch.

 

[David Schwantz]

When I run no switch band I put the pull pin right at the joint of the 2 sections. That way charges are still dead until on the pad.

 

[OverTheTop]

Thanks for sharing. Glad you are only rattled and not damaged.

FWIW I always treat a rocket with charges the same as I would treat a loaded gun. I only point it where it will not do damage, in case of inadvertent triggering. Have only had one go off unintentionally so far. It was on the pad and blew the NC off when the telemetry keyed up, as I was walking away. Internal EMC problem . Scrub. Fix. Fly another day.

 

[mrwalsh85]

Hi Roy, glad all ok. You said that you misalignned the vent holes. Are your vent holes not in a switch band? I have also run no switch band on mine,, but I always have alignment pins and sockets for the parts to go back together as desired. This avoids any misalignment problems.

Anytime I drill an array for screws, I always offset one screw by 1/8" too high or too low. This way I know which one yields me the proper alignment. Goes for assembling an av bay to a recovery bay, and also goes for shear pins. I would rather do that than hunt for the one screw hole that is off by just a CH, resulting in me trying all possible hole combinations five times over before something fits, finally.

 

[OverTheTop]

If you are looking for a way to align everything, I used a pin, either steel or carbon fiber at the interface point between the sections. It gets glued into the section with the coupler and greatly assists in getting everything aligned. Just mate both halves, including screws, then drill the hole and glue into the larger section.



This is a 1/8" steel pin in my 8.25" Nike Smoke.

I use the CF rod for smaller rockets.

 

[Nytrunner]

One of the methods my school team came up with a few years back (to satisfy the utter paranoia of Univ safety org...) was to ductape the unplugged vacuum mouth to the vent hole you're using, switch on the vacuum (still unplugged) and then retreat to the end of the vacuum power cord and make the power connection there. All out tests went off without incident, but we were 30 ft away regardless.

[Nowadays, I just use an estes E-launch controller with the 30' leads and an ematch for deployment testing.]

 

[RocketDestroyer]

I disagree with your conclusion. The misaligned holes are why the charges didn't fire. You weren't able to remove air from the bay with the vacuum. I think what may have fired the charges was when the AV bay slid out of the booster part way. How well sealed are the ends of your AV Bay?

" When I picked it up, the AV bay slides out of the booster section less than 1/4" (mistake #3). "

My rule... Once the rocket is armed, whether on the ground for testing or on the rod, don't move it. Disarm it first.

 

[Steve Shannon]

" When I picked it up, the AV bay slides out of the booster section less than 1/4" (mistake #3). "

My rule... Once the rocket is armed, whether on the ground for testing or on the rod, don't move it. Disarm it first.

That’s correct. That’s really the intent of the NFPA rule requiring disarming before lowering.

 

[roytyson]

That’s correct. That’s really the intent of the NFPA rule requiring disarming before lowering.

I agree with both post on this topic. My intent was to disarm. The SMT sleds for this rocket has a screw that you screw in to arm and unscrew to disarm. the screw I needed was pointing straight down. Looking back I should have configured the vac so the screw was up. Being lazy, picked the rocket up to disarm. I had a screwdriver in hand, just didn't make it that far.

 

[Steve Shannon]

I commend you for sharing this cautionary tale.
For ground testing I just light the ematch using my launch system. There’s very little to be learned and as you realized (to your credit!) additional risk to attempt a full on test like you did. I’ve never tested an altimeter. If I had one I was concerned about I would test it separately with LEDs rather than charges.

 

[cerving]

What BF Rockets said...vacuum testing is a very poor analog for flight, but it'll set your charges off absent a test-mode function. Just run the e-match external, remove sources of error (the altimeter and the vacuum and all subsequent issues like alignment) and power the e-match directly to assess ejection charge size.

I'll probably take some flak for this, but I personally think vacuum testing is better than a "test flight" function, since it's actually using the baro sensor as it was intended to be used. Canned test flights just test the flight logic, which in itself is a good thing, but they don't test the sensor.

I'm a big fan of remote ejection charge testing, which is why we built this function into the Eggtimer Quantum, Proton, and TRS. Ditto for remote arming, especially for airstarts.

 

[DavidMcCann]

What BF Rockets said...vacuum testing is a very poor analog for flight, but it'll set your charges off absent a test-mode function. Just run the e-match external, remove sources of error (the altimeter and the vacuum and all subsequent issues like alignment) and power the e-match directly to assess ejection charge size.

This is also how I've done it if I ever had a concern about an altimeter. I've never had one fail so i've honestly stopped testing them. All I do now are charge tests on rockets.

I think that there is still value in doing an integrated vacuum and deployment test. I like to check for pressure spikes in the recorded data (as altitude dips) which indicate that pressure from the charge is getting into the AV-bay. If that is happening, BP residue is getting into the electronics and can cause corrosion problems down the road.

the safety risk of testing in this manner outweighs the dubious benefit of seeing if you have an av -bay leak.

 

[Cameron Anderson]

I'll probably take some flak for this, but I personally think vacuum testing is better than a "test flight" function, since it's actually using the baro sensor as it was intended to be used. Canned test flights just test the flight logic, which in itself is a good thing, but they don't test the sensor.

I'm a big fan of remote ejection charge testing, which is why we built this function into the Eggtimer Quantum, Proton, and TRS. Ditto for remote arming, especially for airstarts.

I misspoke somewhat - vacuum testing to ensure altimeter function and seperate testing for charges. I actually vacuum tested a second-hand eggtimer quark yesterday that my friend bought - it was built by someone else and never flown. It was a full-up charge test too since his av bay was sealed and independent charge testing was unfeasible.

I agree there is a place for vacuum testing (when I do it, I use e-matches not LEDs to directly replicate the electric loading), but I prefer to seperate my altimeter function testing from my ejection charge validation.

 

[Flyfalcons]

the safety risk of testing in this manner outweighs the dubious benefit of seeing if you have an av -bay leak.

A properly done vacuum test carries no more risk than arming a rocket on the pad.