Stupid Newbie Black Powder Noise Question #238...

How loud is a 0.86g charge tested in a cup with a centrifuge vial in open air? Will it get the cops called on me? ('Those dang kids and their illegal fireworks!'). Or is it a 'pop' no more bothersome than a lawnmower coughing or popping a paper bag? (I live in-town, but generally have pretty cool neighbors, just not M-80 or gunshot cool).

I want to incrementally test my my AV Bay, new LiPo batts and one of my altimeters (RRC3) using the sim tool from my laptop but the rocket body is not ready for an all-up ground recovery deployment test. First, test with just e-matches, then, on an extended cable, with loaded vials (0.86g Drogue & 0.76g Main) but in open air.

I want to test the vial/cup combo a full strength (I am using a short length of high pressure hose in the cup and need to see how they will work with relatively small loads). I can do a reduced charge load for a functional (if not structural) test, I suppose.

I have a business trip next week and a very full work schedule between now and the first HP fly-in I can make on June 8th, and I need to move forward testing what I can do while waiting on some crucial pieces of hardware, finishing, etc..

a recent test...you'll hear a leaf blower in the background..to mask the sound and smell of the ground test.



Tony

That's not bad. I wonder what an open air shot sounds like though?

Curtis Enlow said:

That's not bad. I wonder what an open air shot sounds like though?

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Well.....a nice tightly packed apogee backup charge can be heard from 4000' on a calm day...and most of my charges are sized somewhere about .7 to 1.5 grams for up to 3" rockets iirc ( depending on payload bay volume of course. But the back-up charge is usually fired into a open tube, in a closed tube its not nearly as loud.

rharshberger said:

Well.....a nice tightly packed apogee backup charge can be heard from 4000' on a calm day...and most of my charges are sized somewhere about .7 to 1.5 grams for up to 3" rockets iirc ( depending on payload bay volume of course. But the back-up charge is usually fired into a open tube, in a closed tube its not nearly as loud.

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Yeah, Rich, I am thinking for a functional test just using a reduced amount, like 0.2g, with no body tubes. Just enough to make sure the e-match is in the powder and sets it off; i don't want to alarm anyone. I'll just have to save the structural test for the full-on recovery deploy test.

They'll all just have to deal with the THWAAAMP! as I shoot my nose cone across the yard, however

Also, Rich, is there a mail list for the upcoming sod blaster fly-in? I'm hoping to make it probably the 8th & 9th, as i am not going to make FITS.

Ground tests normally get the neighbourhood dogs barking nicely...

As long as your match head is in the powder you won’t have any problem igniting the black powder.
For reference, consumer firecrackers have a maximum of 50 milligrams of flash powder. M-80s, which are regulated, sometimes have as much as 3 grams. A charge in a plastic vial with an ematch will sound loud. They are much quieter when used in a ground test with your parachute etc. muting the noise. If you have sensitive neighbors I would alert them first.
I would just do the ground test. You’ll still know whether the powder ignites. Make sure the nosecone is pointed in the right direction.

Don't point the NC at anything you don't want to put a hole in. I have seen wheelie bins be punctured by nosecones when testing.

And make sure the back end of the rocket is secured. That silly Newton and his Third Law of Motion says that if the nose cone is going one way the back end will try to go the other way.

I sort of had both of the above issues when I once did a ground test.



I didn't expect the nose section to end up so close to the neighbor's car. And, I used a motor adapter plugged with a disk of wood to seal the tail end of the rocket. But, I didn't secure it well enough in the rocket. It shot out the back, hitting the curb next to my driveway (just missing hitting our minivan).

The sound wasn't too load. It made a throaty "oomph" sound.

The isn't much of a need to test the ejection charge outside of the rocket. You might just wait until you are ready to do a test with your rocket.

Or, do the test at a club launch ... with permission from the club and a warning to others, of course.

Curtis Enlow said:

Yeah, Rich, I am thinking for a functional test just using a reduced amount, like 0.2g, with no body tubes. Just enough to make sure the e-match is in the powder and sets it off; i don't want to alarm anyone. I'll just have to save the structural test for the full-on recovery deploy test.

They'll all just have to deal with the THWAAAMP! as I shoot my nose cone across the yard, however

Also, Rich, is there a mail list for the upcoming sod blaster fly-in? I'm hoping to make it probably the 8th & 9th, as i am not going to make FITS.

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We post to the Northwest Rocketry list, TRF, TRA and NAR Facebook, we also have a TCR members email list that we send out things on occasionally. The clubs webpage has the latest launch statuses usually. We try and make final decisions for Go/NoGo no later than the Thursday before the launch. Really hoping for good weather for June Swoosh.

A buddy and I went to a small public park in a residential neighbourhood to do this, in plain sight of houses nearby. A few kids came by, attracted by the 5-foot rocket, and asked if we were going to launch it. Basic explanations and a couple of "POPS" (or "THWAAAMP!'s", I don't remember) made for great educational entertainment. They sure had a great story to tell their parents!

jadebox said:

I sort of had both of the above issues when I once did a ground test.....

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So that is your neighbors car the nose cone is aiming for....

Thanks, everyone, I now have a much better idea of what to expect.

I agree, other than an LED or e-match functional test I might as well wait until I can do an all-up test on the entire deploy before using powder.

I do have a question regarding the drogue ejection. I will have dual redundancy (RRC3 w/1-sec drogue delay & RRC2-Mini as the primary) but also the usual last-gasp motor charge. Do you use a protector at the bottom of the tube above the MMT just in case the motor ejection charge is, for whatever reason, the deploying charge?

Also, with regards to drilling the delay charge, do you have a rule of thumb as to how long you set it for after your prime (or back-up) drogue delay goes off? I know sims are not always accurate, and it's unlikely that dual redundancy won't deploy a drogue at (or near) apogee, but you don't want the motor deploying it on a ballistic descent, either.

How do you guys typically play this?

thanks!

C

Curtis Enlow said:

Thanks, everyone, I now have a much better idea of what to expect.

I agree, other than an LED or e-match functional test I might as well wait until I can do an all-up test on the entire deploy before using powder.

I do have a question regarding the drogue ejection. I will have dual redundancy (RRC3 w/1-sec drogue delay & RRC2-Mini as the primary) but also the usual last-gasp motor charge. Do you use a protector at the bottom of the tube above the MMT just in case the motor ejection charge is, for whatever reason, the deploying charge?

Also, with regards to drilling the delay charge, do you have a rule of thumb as to how long you set it for after your prime (or back-up) drogue delay goes off? I know sims are not always accurate, and it's unlikely that dual redundancy won't deploy a drogue at (or near) apogee, but you don't want the motor deploying it on a ballistic descent, either.

How do you guys typically play this?

thanks!

C

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No sense in testing if you're not testing the whole system with all the rig in place. Word to the wise: Make a roll of cloth from an old t-shirt the same size and shape as your best fold job on your recovery gear, wrap it in duct tape, and USE THAT instead of your actual parachute. No sense in risking damaging it in testing. If your testing pulls the burrito wrap out into the air stream with authority, without over extension and snap back, you'll be fine.

Your nomex/wrap should be large enough to fully burrito wrap the parachute and whatever recovery harness that you need protected in the drogue section if using motor back up. TN harnesses in the drogue position I usually cover top and bottom with a nomex sleeve, with the bulk in the bundle, since the drogue is so tiny by comparison. I mostly use kevlar these days, but I make those longer to compensate for no give and size charges accordingly. Dog barf, a handful or two top and bottom, will usually provide enough of a buffer to not even leave scorch marks on the nomex.

As for motor back up to the back up altimeter, it's usually back up +1, so you get Apogee, electronic back up at +1, and motor back up at +2. Anything more than +2 and you're looking at deploying at significant speed (which is still preferable to not deploying or during ballistic flight). Remember, the delay is nominally +/-10% anyway, which is why your simulation (or experience) is CRITICAL to knowing what delay to actually drill to.

Curtis Enlow said:

Do you use a protector at the bottom of the tube above the MMT just in case the motor ejection charge is, for whatever reason, the deploying charge?

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My chutes get wrapped inside the Nomex burrito style, so no need for two of them.

Curtis Enlow said:

Also, with regards to drilling the delay charge, do you have a rule of thumb as to how long you set it for after your prime (or back-up) drogue delay goes off?

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Motor back-up gets apogee + 2.

+1 on all up ground test

Great tips, thanks, guys! I especially like the t-shirt suggestion, Tom.

I've heard of rubber banding the last couple Z-coils to ease the shock, but i am wondering if tying the Z-coils with a light guaranteed-to-break thread might be better than tape for holding it all together until deployment?

Also, should I completely block the MMT, assuming the ejection charges will still be intact and thus the motor sealed for pyro tests? the answer seems obvious, but at this point I am crossing all my T's!

#2 - I prefer the little rubber hair bands.

#3 - Yes, block; otherwise all your pressure escapes through the MMT and no deployment occurs.

Curtis Enlow said:

Great tips, thanks, guys! I especially like the t-shirt suggestion, Tom.

I've heard of rubber banding the last couple Z-coils to ease the shock, but i am wondering if tying the Z-coils with a light guaranteed-to-break thread might be better than tape for holding it all together until deployment?

Also, should I completely block the MMT, assuming the ejection charges will still be intact and thus the motor sealed for pyro tests? the answer seems obvious, but at this point I am crossing all my T's!

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I use blue masking tape on my z-folds and have yet to have an issue.

Just invite the neighbors over. Tell them what is happening, over adult beverages, after the tests of course, (because you are always safe), and let them push the buttons.

It makes for better neighbors!

Handeman said:

Just invite the neighbors over. Tell them what is happening, over adult beverages, after the tests of course, (because you are always safe), and let them push the buttons.

It makes for better neighbors!

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Ha! That's pretty much exactly what they'd do! I do have some good neighbors; they keep an eye on the place while I'm gone and they're well-armed

Handeman said:

Just invite the neighbors over. Tell them what is happening, over adult beverages, after the tests of course, (because you are always safe), and let them push the buttons.

It makes for better neighbors!

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Yeah, most people are really cool with things once they understand what is going on. It's the surprises you may want to avoid.

Here is my L3 ground tests for deployment. In my side yard. No neighbors were informed or harmed...
Main chute deploy.
6 grams ffffg black powder.

4 grams drogue test.

rharshberger said:

I use blue masking tape on my z-folds and have yet to have an issue.

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I warned my neighbors, but they didn't hear anything. I've got a little bit different neighborhood than most -- 10 acres out in the desert. It encourages "eccentric" pursuits. My closest neighbor shoots off his homemade cannon from time to time, along with some tracer rounds in his old BAR. Given that, I'm the quiet and shy one.

+1 on the blue masking tape. I like to roll the harness into “pucks” just smaller than the airframe ID. That way you stack up the pucks and it takes very little space.

Euclid said:

A buddy and I went to a small public park in a residential neighbourhood to do this, in plain sight of houses nearby. A few kids came by, attracted by the 5-foot rocket, and asked if we were going to launch it. Basic explanations and a couple of "POPS" (or "THWAAAMP!'s", I don't remember) made for great educational entertainment. They sure had a great story to tell their parents!

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My ground tests usually attract the neighborhood kids too. They love it when the "Rocket Guy" is testing deployment charges.

Here was my all-up test today with incremental charge increases:

Bill Hanson said:

I warned my neighbors, but they didn't hear anything. I've got a little bit different neighborhood than most -- 10 acres out in the desert. It encourages "eccentric" pursuits. My closest neighbor shoots off his homemade cannon from time to time, along with some tracer rounds in his old BAR. Given that, I'm the quiet and shy one.

+1 on the blue masking tape. I like to roll the harness into “pucks” just smaller than the airframe ID. That way you stack up the pucks and it takes very little space.

View attachment 384449

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Cool, glad to see someone else using pucks. You'll want to roll all of them like the one on the right. I have had some bind in ground tests when rolled like the rest of them in your photo.

jahall4 said:

Cool, glad to see someone else using pucks. You'll want to roll all of them like the one on the right. I have had some bind in ground tests when rolled like the rest of them in your photo.
View attachment 384854 View attachment 384855

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Good to know! Thanks for sharing your experience

Curtis Enlow said:

Here was my all-up test today with incremental charge increases:

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I liked the increment background noise response

First test.....one dog barking

Second test.......two dogs barking

Third test...... three dogs barking

Last test......dogs barking and then we hear a siren.......