High altitude recovery

[Crumb fire]

Hello everyone,
I am working on a project that would bring my rocket to an altitude of more than 15k. I wonder if the dual deployment with black powder is still effective at this altitude.
Have you encountered any problems, and what altitude should we think about changing ejection methods.

Comments or questions are welcome
Thanks
Steeve

 

[SpaceManMat]

In that 15k feet or 15km?

I'm planning one to 14k feet and are not concerned. I've only seen people talk about this with flights over 50k feet. Not exactly sure where altitude becomes an issue.

Interested to see other peoples thoughts.

For flights up to at least 75k feet, just using an extended charge well works. It contains the expanding gasses and allows the burn to complete.

 

[mpitfield]

I have not been over 17K but I have been up to it several times with BP and had no issues at all. I posted a similar question when I was getting into DD but the responses varied I did not come away with a consensus. However I am comfortable in the flight envelope you mentioned, and up to 20K from attending other launches.

Beyond doing it myself and seeing it live at a launch there seem to be a lot of flights to 30, 40 , and even 50K using BP. I recall reading something about the effectiveness of BP at altitudes but can't recall the details. C02 has been mentioned for higher launches in some threads, but beyond that, but I am not sure what people are doing for the higher alt flights.

I will be following your thread to see if it gets a consensus.

 

[Zebedee]

Jim Jarvis did some interesting experiments: [video=youtube;2b3_JlbAbKQ]https://www.youtube.com/watch?v=2b3_JlbAbKQ[/video]

I've been to 15K ft and 35K ft.

For 15K just up the charge a little as long as your normal method has a reasonable seal.
For 35K feet I used 1.5" of PVC pipe with an end cap expoied on and the ignitor epoxied into the cap, add BP, fill up with wadding and finally several masking tape layers to seal the open end - worked well.

Jim's pipe method works at 150K ft.

 

[Crumb fire]

In that 15k feet or 15km?
It's 15 000' to 20 000' in reality.

I just watch the Jim's video, and I must say that between 10,000 feet and 45,000 feet, doubt sets.

So for better combustion, I will do a T tube that I will test. " just using an extended charge well works" I will do it that way.
On the other side I would still like to hear the experiences of many people as possible.

I know 15000'-20000' is not the end of the world, but if there are better techniques, I would like to know them before launch.

Thanks to all for your contributions and special thanks to Zebedee and Jim!
Like I said, I'm always open to launches and experiences others have had in the past.

Steeve

 

[JimJarvis50]

I did an article for Rockets Magazine a few years ago on charge testing. It's attached (this is the same article I've posted previously).

Jim

View attachment Article on high altitude deployment charges_May 2013.pdf

 

[jsdemar]

Above 15k MSL, I use BP enclosed in surgical tubing. It gives more time for combustion instead of scattering the BP without sufficient heat transfer.
I've also used several layers of electrical tape over a PVC endcap, but for higher flights I stick with the surgical tubing. McMaster-Carr carriers it.

 

[tfish]

A few weeks ago I got to playing around with various charge holders in my vacuum chamber. Jim is right Latex tubing does not fair well in "testing" situations. But it seems to do well in actual flights. I know it's worked up to 104K. I think the "trick" is, that the more jammed packed full your apogee bay is, the more likely the latex tube charges will work.

I did not plan on going into details here but briefly.... My test chamber is 6" dia and about 42" long with a 1" lexan top plate. I can draw it down to 27.5 mhg (photo). Inside this I place a my simulated rocket. FG tube 3.375 ID 24" long. One end has a removable cap the other end is open. Inside this I have a coupler that simulates the electronics bay. I use 3- 2/56 nylon shear pins to hold it in place. This coupler has fishing weights 76oz to give it some weight. (photo)
The first test I did was with latex and a one gram charge. Only .4 grams was consumed and it moved the coupler moved 4"
Jim's devices are very efficient consuming 100% of the BP. One thing that was very surprising was how energetic they are! In Jim's write up he states that they are VERY ENERGETIC. Which they are!
I wanted to come up with something that still consumed 100% of the BP but was not as energetic. I started playing around with some 5/16" ID clear vinyl tubing. The finished item (photo) seems to accomplish what I was trying to do. 0.5 grams in my test chamber easily sheared the 3 shear pins, pushed the 76oz ebay complete through the simulated airframe and hit the top of my test chamber. This same set up (0.5 grams of BP) ground tested in my latest 3" min dia rocket sailed the nose cone and ebay 4 feet through the air into my moving blanket back stop without damaging anything. Normally I would have used 1.25 - 1.5 grams of BP to do this.
Some notes and (more) rambling....The dog barf is only loosely packed to hold the BP in place and act as a shock absorber of sorts. The match is placed on top of the BP so that the BP is not blown out of the "charge holder" when the match fires. The BP has to pass by the other flaming stuff to exit the charge holder (100% consumed). The electrical tape is only there to hold the ematch and dog barf in place. It does not need to seal in or out in air. All test vacuumed soaked for 3 minutes prior to test.

This has not been flown yet! Ground test before trying....

Tony

 

[rocket_troy]

In that 15k feet or 15km?
It's 15 000' to 20 000' in reality.

I just watch the Jim's video, and I must say that between 10,000 feet and 45,000 feet, doubt sets.

So for better combustion, I will do a T tube that I will test. " just using an extended charge well works" I will do it that way.
On the other side I would still like to hear the experiences of many people as possible.

I know 15000'-20000' is not the end of the world, but if there are better techniques, I would like to know them before launch.

Thanks to all for your contributions and special thanks to Zebedee and Jim!
Like I said, I'm always open to launches and experiences others have had in the past.

Steeve

For a bit of history: the problem 1st became apparent in WWI. British Pilots were forced to fly at higher altitudes to a reduce their increasing vulnerability from ground attack. The shift from 15,000ft to 20,000ft translated to a significant increase in erratic timing in the BP based shell time fuzes. Upon subsequent ground testing in a vacuum chamber, it was discovered that many of the fuzes simply went out when exposed to such barometric conditions. Later, even a change in formulation didn't completely eradicate the issue and the eventual fix was to switch to mechanical timers which were subsequently replaced by proximity fuzes.

 

[ksaves2]

With the T charge how is it secured in the rocket? Kurt

 

[jsdemar]

I did an article for Rockets Magazine a few years ago on charge testing. It's attached (this is the same article I've posted previously).

Jim

Just read the article. It's unclear how you determined what percent of the powder combusted.

I use 1/8" wall tubing with two ematch about 1/3 the way into each end. The ends are double ziptied as tight as possible. Then I wrap the tubing with duct tape. It would be interesting to see how this compares to the way you prepared the surgical tubing charges in your test.

I'm helping a club member to work on a smokeless powder ejection charge idea. It's similar to your pipe design. I machined small closures for 5/8" aluminum tubing. More about after the tests are completed. But, it looks like it would also work with BP at high altitude based on your 'cannon' design.

 

[JimJarvis50]

With the T charge how is it secured in the rocket? Kurt

The T charge device can just be attached to the harness close to the eye nut. Tape or zip ties or whatever. As I recall, I only used the T-charge once or twice before converting to a "one-sided" charge approach, as shown in the pic. The one-sided charges have quite a kick. I refer to the method as deployment by shotgun. So, the tubes have to be attached to a very sturdy base.

What Tony is working on is a much lighter container with perhaps a bit less kick. The idea would be to use it much like a surgical tube charge, i.e., loose in the air frame. If it works, which means not splitting the vinyl tube, then it would be an easier way to implement the concept. I have a few months before I have to build my replacement electronics bay (for the one I lost at BlackRock last fall), so I'm waiting on his results.

Jim

 

[JimJarvis50]

Just read the article. It's unclear how you determined what percent of the powder combusted.

I use 1/8" wall tubing with two ematch about 1/3 the way into each end. The ends are double ziptied as tight as possible. Then I wrap the tubing with duct tape. It would be interesting to see how this compares to the way you prepared the surgical tubing charges in your test.

I'm helping a club member to work on a smokeless powder ejection charge idea. It's similar to your pipe design. I machined small closures for 5/8" aluminum tubing. More about after the tests are completed. But, it looks like it would also work with BP at high altitude based on your 'cannon' design.

Stretching my memory here ....

I ran a calculation to determine how much residual material should be present after the powder burns. I came up with about half of the original weight, but I never actually recovered that much in the T-charge tests (where I know everything burned). So, I think I just adjusted the baseline to where what was typically recovered in a T-charge test represented 100% burned, and then just prorated between that and the starting weight.

Wrapping the tubing with duct tape would help. My only objection to the approach would just be reproducibility. With the T-charge approach, everything always burns. It will work the same on the ground as at 150K feet, so there is no guesswork.

Jim

 

[bobkrech]

There is no altitude limit for BP charges as long as they are confined until all the powder grains are consumed.

NASA has used hermetic seal BP canisters with a blowout diaphragm for decades to generate high pressure gas activation systems, and the CD3 CO2 system used a sealed BP charge in a piston to activate the CO2 valve....... With more BP and a burst disk, you can eliminate the heavy and bulky CO2 tank........

Jim's tee manifold system is another way to confine the BP until all particles have gasified.....

It simply a matter of mechanical design of the confinement system....

Bob

 

[Crumb fire]

Your tests clearly show the importance of burning all the black powder. I begin to understand why some ejections are not complete at apogee. I even have some bad memories of empty black powder cups (burned) that finished ballistic. It also reminds me that my cups were not very long. I think that even at a low altitude, better containment makes recovery as effective as at ground tests

What about longer tubes with a solid end cap and lateral holes? That would be less “ENERGETIC” no? I have 1/2" piping that I can drill & tap the end so I can add or remove a set screw inside to stop the energy and exit the gases through the side slots rather than the top. My only concern is whether the wadding will come out easily. Maybe I will test with slots rather than round holes. Ground tests...

Here’s a picture of my first try, without the end cap. Next one will have room for a set screw.


I even had a bad idea... installing an eye bolt instead of a set screw. But I prefer to leave mechanical strength to each component.

What do you think?

 

[blackjack2564]

Nic's charge cannons went to 66,000ft. in his O-3400 record flight.



All this was contained in a 7-1 V-K cone.

 

[dixontj93060]

...It also reminds me that my cups were not very long. I think that even at a low altitude, better containment makes recovery as effective as at ground tests

What about longer tubes with a solid end cap and lateral holes?

I think if you contain it too much you will have a bomb on your hands.

Saying that, from what I have read (studied) in Jim J.'s reports and his flight records, the canister geometry is a big factor. Similar to a gun barrel, L>>W makes a huge difference in achieving complete burn as the gas expands.

 

[John Beans]

Not to sidetrack, but my plan is to make this electronic in the future.
That is to say, electronic separation at apogee. Let's eliminate the explosions entirely.

 

[ksaves2]

Not to sidetrack, but my plan is to make this electronic in the future.
That is to say, electronic separation at apogee. Let's eliminate the explosions entirely.

That will be interesting to have enough electro-mechanical energy to cause separation although I suppose if there is a very free moving fit between two sections that are locked, the mechanical force to separate might not be that high.
Get 'em reliably unlocked and it might just take a little push as opposed to being "blasted".

It certainly would not be as high with friction fitting or shearpin usage that would require greater force to overcome. Kurt

 

[dixontj93060]

That will be interesting to have enough electro-mechanical energy to cause separation although I suppose if there is a very free moving fit between two sections that are locked, the mechanical force to separate might not be that high.
Get 'em reliably unlocked and it might just take a little push as opposed to being "blasted".

It certainly would not be as high with friction fitting or shearpin usage that would require greater force to overcome. Kurt

Yeah the pin/plunger part is easy, the trick is getting the canopy sufficiently and consistently out into the airstream.

 

[jsdemar]

Not to sidetrack, but my plan is to make this electronic in the future.
That is to say, electronic separation at apogee. Let's eliminate the explosions entirely.

Start your own thread?

 

[rocket_troy]

Start your own thread?

Some of us have been flying with zero pyros for over 5 years
https://www.propulsionlabs.com.au/Pyroless_Release/

 

[profmason]

Following up with this thread, we did two days of ejection charge tests in a 2 ft long 1.5" clear PVC vacuum chamber(Designed to model the apogee section of our dart) pumped down to -25inHg (about 50000ft equivalent) We tested 3 formats of charges all with 1.25g of powder ignited by an ematch: 1. Our traditional rubber glove finger with duct tape (used for hundreds of <10kft flights) 2. Vinyl tubing per Tonys photo above but substituting glass fiber for dog barf. 3. Aluminum charge cannons. The following two videos show the results.
View attachment video-1618083543.mp4
Test 1: System test (1g black powder in vinyl tube per Tony design.
Test 2: Rubber Glove
Test 3: Rubber Glove
Test 4: 2.5inch 1/2" vinyl tube
Test 5: 3inch 1/2" vinyl tube

Audio also helps with hearing the differences between ejection charges. For the last 3, pressure vs time data was recorded and for all cases the samples were weighed before and after.








Second day of testing. Test were performed with a zoom camera and using remote ignition.

View attachment video-1618089332.mp4

Test 1: 2.5inch 1/2" vinyl tube
Test 2: 2 inch 3/4" diameter aluminum tube
Test 3: 3inch 7/16 vinyl tube
Test 4: 4inch 3/8 vinyl tube
Test 5: 4inch 3/8" diameter Al tube.

Efforts were made to make the volume of the tube close to the same (clearly the fat aluminum tube is larger)







Summary results: The 4" long 3/8" diameter Al tube exhibits substantially more pressure and integrated pressure then the other tubes. Vinyl tubes work better(Give more integrated pressure) then rubber gloves. long thin tubes work better then short fat tubes. This seems to be consistent with the findings of others. Additional testing of the 3/8" Al tube is required.

 

[JimJarvis50]

Summary results: The 4" long 3/8" diameter Al tube exhibits substantially more pressure and integrated pressure then the other tubes.

Yep. I call it deployment by shotgun. Did you quantify the unburned powder?

Jim