Low power, no ejection charge?

The Rocketry Forum

Help Support The Rocketry Forum:

Scott_650

Well-Known Member
Joined
Sep 16, 2015
Messages
903
Reaction score
401
Probably too late for this build, but I was trying to figure out a way that the ejection charge would change the angle of the stabilizers. Possibly by the motor ejecting, or simply moving back, thus allowing a spring loaded lever to move into the empty space.
Do you know any kits that work that way?
The Estes (now a Semroc kit) Gyroc and it’s new upscaled version the Tazz along with the Astron Skydart use a tab to hold the control surfaces neutral during boost then at ejection the tab moves with the motor/power pod to allow the elastic/rubber bands attached to the control surfaces to assume the desired angle for recovery. All the instructions are either on the Estes website or JimZ’s website of instruction scans. I think jrap330’s advice is sound - a Skydart build would be a great way to gain some boost glider experience.
 

Tractionengines

Well-Known Member
TRF Supporter
Joined
Aug 29, 2020
Messages
144
Reaction score
65
Location
Northeast Ohio
you got a weblink to that?
It is in the LONG Aerotech thread at least 2 places were Aerotech said that "experienced users" are allowed to remove the plastic plug and remove or adjust ejection charge, then replace plug; as a manufacturer approved modification on single use motors.
That makes it an approved modification to NAR and Tripoli and does NOT make it a research flight. RSO has final say though at any club launch.
I have it printed out in my range box somewhere...just for reference.
 

jrap330

Retired Engineer, NAR # 76940
TRF Supporter
Joined
Jan 25, 2020
Messages
641
Reaction score
187
Location
NJ
I'd like to think I'm far past the kit stage for standard rockets. I've got about a dozen self designed and built rockets that fly fine. My problem is the recovery.
If I found a kit that did something like I'm trying to do, I think I'd buy it.
Not standard you wan to design a glider.. You have seen numerous post by now where modelers state they have to keep trimming their gliders to get them to glide successfully. Built a few kits get some idea s to steal. Otherwise, you will keep going back to the drawing board. Built the Space shuttle, so many modelers complain how hard it was to get to fly. And use that for creative inspiration.
 

shockie

High Plains Drifter
Joined
Jun 2, 2009
Messages
564
Reaction score
205
Location
My Old Kentucky Home
It is in the LONG Aerotech thread at least 2 places were Aerotech said that "experienced users" are allowed to remove the plastic plug and remove or adjust ejection charge, then replace plug; as a manufacturer approved modification on single use motors.
That makes it an approved modification to NAR and Tripoli and does NOT make it a research flight. RSO has final say though at any club launch.
I have it printed out in my range box somewhere...just for reference.
I found it. "Yes, the larger mid-power motors include 0.7 grams of ejection charge. We have traditionally allowed experienced customers to adjust the ejection charge as needed for their particular rocket."
 

Jay Rairigh

Well-Known Member
Joined
Aug 17, 2019
Messages
92
Reaction score
34
Location
Littleton, Colorado
The Estes Tomcat was a 'jet' style glider with wings that swung out by way of ejection charge and a rubber band. I've heard they are also a pain to get to glide.

I pulled one out of storage last year that I built decades ago and never flew. It will glide, throwing it by hand. Was planning on flying it last year, not caring a bit if it glided away, lol.
 

banjonate

Well-Known Member
Joined
Dec 13, 2014
Messages
58
Reaction score
18
Not if it's an Aerotech composite motor. Aerotech has endorsed the practice of removing ejection charges from their single-use motors, so it's a manufacturer-approved modification and violates no rules.
So, this brings up a question for me (and I have a reason for asking)...

Will a single-use Aerotech composite motor (with the delay charge removed) act like a traditional BP 0-delay booster motor then, and be able to ignite a second-stage BP motor?

Sorry if this is an ignorant question, but I have never heard of doing this before.
 

Neutron95

Well-Known Member
TRF Supporter
Joined
Jan 17, 2010
Messages
329
Reaction score
147
So, this brings up a question for me (and I have a reason for asking)...

Will a single-use Aerotech composite motor (with the delay charge removed) act like a traditional BP 0-delay booster motor then, and be able to ignite a second-stage BP motor?

Sorry if this is an ignorant question, but I have never heard of doing this before.
On the single use Aerotech motors you can remove the ejection charge, not the delay. The delay grain is ignited at the same time as the rest of the motor, and is necessary to keep the hot gasses from at least partially venting out the hole for the ejection charge.
 

Nytrunner

Pop lugs, not drugs
TRF Supporter
Joined
Oct 15, 2016
Messages
7,835
Reaction score
3,503
Location
Huntsville AL
So, this brings up a question for me (and I have a reason for asking)...

Will a single-use Aerotech composite motor (with the delay charge removed) act like a traditional BP 0-delay booster motor then, and be able to ignite a second-stage BP motor?

Sorry if this is an ignorant question, but I have never heard of doing this before.
Short answer, composite motors can't be used like BP staging motors (0 delay)

A composite motor has a core all thw way through the motor, and the burning delay element contains the motor pressure. About the shortest delay you have is 4-6 seconds depending on how big the motor is
 
Last edited:

Bruce

Well-Known Member
Joined
Feb 21, 2019
Messages
240
Reaction score
37
Has anyone direct staged a black powder sustainer from a composite booster?

It seems like a 4-6 second delay might be acceptable with a suitably high thrust booster...
 

dpower

Well-Known Member
Joined
Jan 18, 2009
Messages
1,359
Reaction score
141
AMW carries D11-P motors, they were a bulk special order from Estes a couple years ago. I need to order some, just about out!
 

shockie

High Plains Drifter
Joined
Jun 2, 2009
Messages
564
Reaction score
205
Location
My Old Kentucky Home
Has anyone direct staged a black powder sustainer from a composite booster?

It seems like a 4-6 second delay might be acceptable with a suitably high thrust booster...
Yes Jay Calvert did it back about 15 or so years ago. He wrote up a NARAM-46 R&D report which was published in Sport Rocketry magazine.

He used a pyrogen that was ignited by the ejection charge of the lower stage composite motor and also had some pyrogen in the nozzle of the 2nd stage BP motor.
Imagine a straw that runs from the ejection charge up into the throat of the BP engine,with the straw contains a pyrogen of your choice. Preferably something that burns fast.

For example in the pyrotechnic world, they moisture BP granulate and they use this paste to coat a cotton cord. This is called black match.. Then if its in a small diameter tube,it's called quick match,as it being enclosed makes it burn even faster. You might be able to get the same effect with green safety fuse enclosed in a small diameter paper tube that you can roll yourself.

See https://cannonfuse.com/pyrotechic-information.html. for how to


I would ground test before launching a rocket to verify it works first. And record in slo-mo so you can clearly see what's happening or not.
 

SharkWhisperer

Well-Known Member
Joined
Jan 27, 2021
Messages
269
Reaction score
156
Yes Jay Calvert did it back about 15 or so years ago. He wrote up a NARAM-46 R&D report which was published in Sport Rocketry magazine.

He used a pyrogen that was ignited by the ejection charge of the lower stage composite motor and also had some pyrogen in the nozzle of the 2nd stage BP motor.
Imagine a straw that runs from the ejection charge up into the throat of the BP engine,with the straw contains a pyrogen of your choice. Preferably something that burns fast.

For example in the pyrotechnic world, they moisture BP granulate and they use this paste to coat a cotton cord. This is called black match.. Then if its in a small diameter tube,it's called quick match,as it being enclosed makes it burn even faster. You might be able to get the same effect with green safety fuse enclosed in a small diameter paper tube that you can roll yourself.

See https://cannonfuse.com/pyrotechic-information.html. for how to


I would ground test before launching a rocket to verify it works first. And record in slo-mo so you can clearly see what's happening or not.
For passing fire to ignite a second stage, plain old green safety (Visco) fuse is not ideal for fire transfer between motors, and will definitely not work the way you suggested in terms of speeding up burn rate like quickmatch. If you enclose it in a straw or paper wrapper like blackmatch is used to make quickmatch, it won't burn any faster. Blackmatch works because 1) the flame front of the burning BP is contained and able to jump forward, and 2) BP deflagration/burn rate increases with increased pressure caused by containment. But any decent blackmatch can be turned into quickmatch easily. Best to make your powder from hot homemade BP because commercial stuff (Goex, Old Ensfield, Aerotech ejection charge granules, etc) even the finer stuff (4Fg) is granular and contains dextrin as a binder and is graphite coated. In BP for blackmatch, you add dextrin powder to give the dried match some stiffness and to consolidate your BP into the cotton (no plastics/polymers) fibers after wetting string and drying it, but in commercially made BP granules the dextrin is already wetted and dried, hence polymerized. You can't "unpolymerize" it. So it's just slow rather inert extra fuel. If you opt to make blackmatch, you really need to physically mush the BP slurry into the string for awhile--if a cut section has a white center, or even greyish, you made crummy blackmatch. It typically takes several days to dry, even under ideal conditions--new fireworkers learn this pretty quickly.

Easier is to use is perchlorate-based commercially available fast fuse. Typically silver in color, and legally available from the site you listed above (and many others), it burns at near-quickmatch speeds, well, definitely less than a second per foot (versus 3-5 seconds/inch for green visco and about the same for most decent blackmatch, and up to 100 feet/second for quickmatch. I've used a short section of this to fuse two BP motors. Trick is keeping it in place so it doesn't whip around inside the body tube like a burning snake. Anchored on the booster with a reinforced glob of nitrocellulose lacquer (5% in acetone) that acts almost epoxylike but flammable (coating and base on some igniters), and also anchored in the receiving motor's nozzle with NC lacquer (with some loose BP dropped in the nozzle before inserting fuse). I get consistently reliable fire transfer in Estes boosters or homemade LPR and MPRs boosters using handmade motors and this fire transfer method. Works with stock Estes BP motors, too, including those with ejection charges, as long as you have good contact (etch a little hole in the bentonite clay endcap for some pressure relief and fire passage, or remove ejection charge entirely. Yes, I'm aware that this is against NAR regs, making it a research project. So is making your own BP and BP motors. But you can do so legally so long as you follow the BATFE Orange Book regulations (and local restrictions) to the letter. Though most motors I use for finned rockets are D/E specs with short cores, I can make an F-G moderate impulse motor for about $2 in materials, that'll easily lift 2+ pounds depending on the coring tools used (and BP oxidizer/fuel ratio). Super high impulse motors are possible, too (longer core, hotter BP), but those risk ripping off your fins or turning weak tubes into accordians, and are best used for fireworking, not finned rocketry.

Approach could likely work to transfer fire when using composite-fuel engines as boosters/receivers if you souped up your receiver motor ignition fuse's NC lacquer/pyrogen a little bit to guarantee proper ignition.

Edited for clarity and spelling...
 
Last edited:

shockie

High Plains Drifter
Joined
Jun 2, 2009
Messages
564
Reaction score
205
Location
My Old Kentucky Home
For passing fire to ignite a second stage, plain old green safety (Visco) fuse is not ideal for fire transfer between motors, and will definitely not work the way you suggested in terms of speeding up burn rate like quickmatch. If you enclose it in a straw or paper wrapper like blackmatch is used to make quickmatch, it won't burn any faster. Blackmatch works because 1) the flame front of the burning BP is contained and able to jump forward, and 2) BP deflagration/burn rate increases with increased pressure caused by containment. But any decent blackmatch can be turned into quickmatch easily. Best to make your powder from hot homemade BP because commercial stuff (Goex, Old Ensfield, Aerotech ejection charge granules, etc) even the finer stuff (4Fg) is granular and contains dextrin as a binder and is graphite coated. In BP for blackmatch, you add dextrin powder to give the dried match some stiffness and to consolidate your BP into the cotton (no plastics/polymers) fibers after wetting string and drying it, but in commercially made BP granules the dextrin is already wetted and dried, hence polymerized. You can't "unpolymerize" it. So it's just slow rather inert extra fuel. If you opt to make blackmatch, you really need to physically mush the BP slurry into the string for awhile--if a cut section has a white center, or even greyish, you made crummy blackmatch. It typically takes several days to dry, even under ideal conditions--new fireworkers learn this pretty quickly.

Easier is to use is perchlorate-based commercially available fast fuse. Typically silver in color, and legally available from the site you listed above (and many others), it burns at near-quickmatch speeds, well, definitely less than a second per foot (versus 3-5 seconds/inch for green visco and about the same for most decent blackmatch, and up to 100 feet/second for quickmatch. I've used a short section of this to fuse two BP motors. Trick is keeping it in place so it doesn't whip around inside the body tube like a burning snake. Anchored on the booster with a reinforced glob of nitrocellulose lacquer (5% in acetone) that acts almost epoxylike but flammable (coating and base on some igniters), and also anchored in the receiving motor's nozzle with NC lacquer (with some loose BP dropped in the nozzle before inserting fuse). I get consistently reliable fire transfer in Estes boosters or homemade LPR and MPRs boosters using handmade motors and this fire transfer method. Works with stock Estes BP motors, too, including those with ejection charges, as long as you have good contact (etch a little hole in the bentonite clay endcap for some pressure relief and fire passage, or remove ejection charge entirely. Yes, I'm aware that this is against NAR regs, making it a research project. So is making your own BP and BP motors. But you can do so legally so long as you follow the BATFE Orange Book regulations (and local restrictions) to the letter. Though most motors I use for finned rockets are D/E specs with short cores, I can make an F-G moderate impulse motor for about $2 in materials, that'll easily lift 2+ pounds depending on the coring tools used (and BP oxidizer/fuel ratio). Super high impulse motors are possible, too (longer core, hotter BP), but those risk ripping off your fins or turning weak tubes into accordians, and are best used for fireworking, not finned rocketry.

Approach could likely work to transfer fire when using composite-fuel engines as boosters/receivers if you souped up your receiver motor ignition fuse's NC lacquer/pyrogen a little bit to guarantee proper ignition.

Edited for clarity and spelling...
you mean this:

 

SharkWhisperer

Well-Known Member
Joined
Jan 27, 2021
Messages
269
Reaction score
156
you mean this:

Yes, that is standard fast fuse/quick fuse that is sold to consumers on multiple websites. It is not true quickmatch (need an ATF user license to purchase that). Each batch varies somewhat in exact burn rate, but burn speed range is usually shown on a sticker on the package. It's fast enough that precise speed in a short section for fire transfer between motors probably won't be an issue, but if timing needs to be precise, then you need to test it yourself. Cut off a few inches from the end before cutting additional quantities to measure and use--the ends sometimes get crushed in the cutting machine or dump powder in transit and are not always uniform burning. In small quantities, usual current pricing is a ridiculous $5 for a 20-foot roll (plus shipping), but for fire transfer in boosted rockets, that might last you quite awhile.

Sites like those also have various tubes for sale, both convoluted and spiral, but the thicknesses and weights are often much greater than you'd use in a typical LPR/MPR. But if you poke around at the specs, you might find some useful items that are a fraction of the price as standard motor mount/body tube/coupler tubes from rocketry shops. Might need to do some cutting or sanding to get them just right, though. Can never have too large an assortment of tubes!

Regarding an earlier comment about grinding down some 3Fg BP for ejection charges, well, that website (and others) also sell reasonably priced plastic-encased round screens of multiple mesh sizes that will allow you to quickly separate your powders into 3Fg, 4Fg...Meal D if it's that critical to you for setting up precise ejection charges. For my ejection purposes, 3Fg (grain size 0.29-0.84 mm) and 4Fg (0.15-0.42 mm) overlap a little in size range and are pretty similar in performance in smallish quantities. The 4Fg burns a tad bit faster, but they produce the same gas volume per gram (not volume), but both are plenty fast to pop a rocket recovery system. You might actually prefer the 3Fg for LPR/MPR purposes since it'll take a fraction of a second longer to burn and build pressure--slightly less rapid pressure buildup stressing your body tube but slightly larger granules that burn bigger holes if they are allowed to touch any flame-sensitive components (plastic/nylon chutes) if they're not adequately protected. BP mesh/mm sizes are tabulated at: https://www.skylighter.com/blogs/fireworks-information/black-powder-grades-sizes-mesh . Be sure you don't confuse firearm/sporting goods store-grade Fg sizing with blasting FA sizing, or it could do bad things to your rocket. Oh, and that mesh sizing link provided above--I have never bought anything from that company in my life, and never will--they are easily 50-200% more expensive, for everything they sell, than every single one of its competitors.

Also. Gotta be careful with Visco fuse coat coloring as an accurate speed indicator. Typically, fast fuse is grey. However, I've come across fast fuse that was dark green in a big box store in PA, and it looks exactly like slow-burning visco. This can get you in trouble if you mix up fast vs slow green fuse; especially if you were expecting slow and instead you got fast. Yipes. Mine is labeled plainly and kept separate so I never risk confusing them.

Safety first, PPE always. Eyes and hands are nice to have around.


Edited to add pricing information.
 
Last edited:

shockie

High Plains Drifter
Joined
Jun 2, 2009
Messages
564
Reaction score
205
Location
My Old Kentucky Home
Yes, that is standard fast fuse/quick fuse that is sold to consumers on multiple websites. It is not true quickmatch (need an ATF user license to purchase that). Each batch varies somewhat in exact burn rate, but burn speed range is usually shown on a sticker on the package. It's fast enough that precise speed in a short section for fire transfer between motors probably won't be an issue, but if timing needs to be precise, then you need to test it yourself. Cut off a few inches from the end before cutting additional quantities to measure and use--the ends sometimes get crushed in the cutting machine or dump powder in transit and are not always uniform burning. In small quantities, usual current pricing is a ridiculous $5 for a 20-foot roll (plus shipping), but for fire transfer in boosted rockets, that might last you quite awhile.

Sites like those also have various tubes for sale, both convoluted and spiral, but the thicknesses and weights are often much greater than you'd use in a typical LPR/MPR. But if you poke around at the specs, you might find some useful items that are a fraction of the price as standard motor mount/body tube/coupler tubes from rocketry shops. Might need to do some cutting or sanding to get them just right, though. Can never have too large an assortment of tubes!

Regarding an earlier comment about grinding down some 3Fg BP for ejection charges, well, that website (and others) also sell reasonably priced plastic-encased round screens of multiple mesh sizes that will allow you to quickly separate your powders into 3Fg, 4Fg...Meal D if it's that critical to you for setting up precise ejection charges. For my ejection purposes, 3Fg (grain size 0.29-0.84 mm) and 4Fg (0.15-0.42 mm) overlap a little in size range and are pretty similar in performance in smallish quantities. The 4Fg burns a tad bit faster, but they produce the same gas volume per gram (not volume), but both are plenty fast to pop a rocket recovery system. You might actually prefer the 3Fg for LPR/MPR purposes since it'll take a fraction of a second longer to burn and build pressure--slightly less rapid pressure buildup stressing your body tube but slightly larger granules that burn bigger holes if they are allowed to touch any flame-sensitive components (plastic/nylon chutes) if they're not adequately protected. BP mesh/mm sizes are tabulated at: https://www.skylighter.com/blogs/fireworks-information/black-powder-grades-sizes-mesh . Be sure you don't confuse firearm/sporting goods store-grade Fg sizing with blasting FA sizing, or it could do bad things to your rocket. Oh, and that mesh sizing link provided above--I have never bought anything from that company in my life, and never will--they are easily 50-200% more expensive, for everything they sell, than every single one of its competitors.

Also. Gotta be careful with Visco fuse coat coloring as an accurate speed indicator. Typically, fast fuse is grey. However, I've come across fast fuse that was dark green in a big box store in PA, and it looks exactly like slow-burning visco. This can get you in trouble if you mix up fast vs slow green fuse; especially if you were expecting slow and instead you got fast. Yipes. Mine is labeled plainly and kept separate so I never risk confusing them.

Safety first, PPE always. Eyes and hands are nice to have around.


Edited to add pricing information.
I was going to say, ....or screen it, but I wasn't 100% sure that was ok.
 

SharkWhisperer

Well-Known Member
Joined
Jan 27, 2021
Messages
269
Reaction score
156
There's really zero risk in screen-sizing BP granules unless you have a lit smoke hanging out of your mouth when doing so... It's pretty stable stuff, though it does have a low ignition temperature.

I typically use screen-size +10-20 (all goes through a 10-mesh screen; none through a 20 mesh screen) for ejection charges. And my BP is definitely hotter than commercial firearm BP, which uses mediocre charcoal (wood hard to standardize, as is charcoal manufacture), has binders (dextrin and maybe others that slow burn rate), other additives/stabilizers (shelf-life; untreated should be indefinite if stored properly), and graphite coating of rounded granules (round=harder ignition--no jutting edges to catch flame; graphite burns like kaka as a fuel though pure carbon, but adds a glossy sheen and helps keep granules separated). Commercial BP is about uniformity for use in BP firearms, not being the hottest/fastest, but those parameters become more important if you want a BP motor to act more like a composite APC fuel (which are also simple).

In short, my ejection charges are usually somewhere between 3Fg and 4Fg, closer to 3, with no additives (no need for dextrin for such applications in motor-making--leave it loose except for an endcap/paper cap depending on design), or preservatives (NC smokeless and relatives for firearm cartidges will go bad without additives (like diphenylamine) over many, many years. BP will not if stored properly.

Muzzleloader Joe can keep up to 50 lbs of commercial BP stored wherever they want--above their oven for all ATF cares. Legal (maybe your local firemarshal would disagree). But take exceptional caution if you decide to make your own BP--the rules change dramatically. And once you've "altered" your legal BP, for example by grinding it to a different mesh...all bets are off and you are now under ATF jurisdiction regarding "manufacture" regulations. If you decide to explore new topics, please educate yourselves on the nuances and potential implications. Few rocketeers are going to get either User or Manufacturer explosives licenses (not difficult if you have a clean record and enough land not to potentially harm neighbors, and have your storage magazine inspected), but all can manufacture/use (within local legalities) small pyro devices for personal use so long as they are neither stored over a day or transported on public roads (this is what puts the crunch on evaluating your own stuff).

Ok, seems this is a sensitive topic that may be discouraged from expansion. I love finned MPRs operating on Estes (high-priced) E-F motors, and I love finned LPRs/MPRs flying on hand-rammed homemade hot willow-BP motors (legal, but not NAR-approved). Rockets are the best!!!
 

Bruce

Well-Known Member
Joined
Feb 21, 2019
Messages
240
Reaction score
37
In short, my ejection charges are usually somewhere between 3Fg and 4Fg, closer to 3, with no additives (no need for dextrin for such applications in motor-making--leave it loose except for an endcap/paper cap depending on design)
What is the reason to leave the BP for the ejection charge loose? I always thought that confining it a little was a good thing?
 

SharkWhisperer

Well-Known Member
Joined
Jan 27, 2021
Messages
269
Reaction score
156
It is a good thing to keep it under pressure, especially for large volumes.
You're not going to get significant confinement with a small charge under a clay or especially paper cap (or plastic cap on composites, with generally loose granules). Not compacting the BP, and smaller grains, allows faster fire transfer than pressed pucks/grains. Estes compacts the ejection charge so it can then compact a retaining clay endcap on their motors for storage/transport--a matter of safety and convenience not necessity. I do the same with ejection charges that are built into handmade BP motors, for convenience not neccessity. In a pinch, however, you will get the same ejection effect by simply gluing in a cardstock disk over loose BP. The compressed clay doesn't really provide all that much extra confinement vs a glued-in disk. Aerotech single-use composites just have a plastic cap over the ejection end, over loose granules you can pour out. When the ejection charge burns, it creates pressure in all directions, so long as the forward pressure is sufficient to eject your recovery gear, you're good. At the same time, there's also a burst backwards out of the nozzle and pressure on side walls. Compacting BP is not the same as confining BP. Two unrelated animals. Finer grains burn fastest, and much faster than BP pucked/pressed to max density of 1.7-1.8 g/cc in fuel grains. Compressed grains can burn at reproducibly predictable rates, necessary to prevent CATOs in rocket motors, but not necessarily the fastest (why we dumb down our BP burn rates with more charcoal/oxidizer in core-burners vs end-burners). Cannon-grade BP needs a slow pressure build up and a lot of powder and the grains are often almost 5 mm in diameter (that's approaching 1/4"!!), huge. Blasting BP grains are even larger--up to 1/3". Early marine cannons used powder grains almost an inch in diameter. And not compacted. If you placed the same mass of 4Fg in a cannon as its specified larger-grain powder, you'll have an excessive pressure spike (but the exact same gas volume generation--just faster) that could burst the barrel. Also the case in muzzleloaders--pyrodex grains as a BP replacement are in grains as a matter of convenience--they also sell it in granules). And different burn rates are why non-compacted (but definitely confined) muzzleloader BP is different grain sizes for pistols vs rifles.

Ejection is about properly regulated gas generation to do the work--not a low-explosive shockwave (deflagration actually, not detonation). Better confinement will indeed increase deflagration rate and shockwave speed, but that's not what we're after. Too much and you blow tubes apart and maybe rip shoot lines. Also, there's negligible difference between the confining capacity of a clay endcap vs a glued in cardboard using endcap as far as the small amount of ejection charge BP is concerned.

Please note that I am referring specifically to LPR and MPR applications only, not HPR.

Edited to correct misspelling... "pore" vs "pour", and a few other clarifications :=)
 
Last edited:

SharkWhisperer

Well-Known Member
Joined
Jan 27, 2021
Messages
269
Reaction score
156
Has anyone direct staged a black powder sustainer from a composite booster?

It seems like a 4-6 second delay might be acceptable with a suitably high thrust booster...
You can easily modify the fire-transfer approach using fuse that I outlined in a previous post, to give any delay desired. The same places that sell fast fuse (for immediate fire transfer--a fraction of a second burn rate/foot) and super slow green safety fuse (maybe 30 seconds/foot) also sell a large selection of fuses with different burn rates in between these two. One commonly used example is about halfway between the two called "Perfect fuse", which burns around 15 seconds/foot. It's usually purple, but take care with using fuse color as a definitive identifying marker--always test a new roll of fuse yourself. There are several others, mostly on the faster end of Perfect fuse. Many options. So, depending on the distance between motors in your design, you can tailor your fuse selection pretty well to give whatever delay is desired. Another advantage of using slower (but not slow) fuse is that it doesn't whip around quite as much inside body tubes like quick fuse will do. While it's easier to control that way, any fuse you use needs to be anchored to ignition and recipient sites, to absolutely guarantee predictable fire transfer. My buddy forgot this once on an Estes Patriot that he'd modded to be a two stager (just combined two kits), with fire transfer using fast fuse. Well, it wasn't anchored into the recipient nozzle and whipped itself right out of the nozzle during it's burn. Lawndart. First motor (1/2" ID x 5" length endburner using homemade BP) took the modded (and much heavier with booster and weight of two 5" motors and reinforced mounts) to slightly over 700 feet (altimeter confirmed) before failure to ignite the second motor. An Estes C-motor might've pushed that overweight rocket to 400 feet. Maybe. The stock configuration is only slated to hit 600 feet on a C motor. If you are trying novel approaches like this for using composites to boost or receive, strongly suggest doing ground tests to make sure you've got the technical kinks worked out and properly timed, and successful, fire transfer. Nobody likes rockets coming down around them in ballistic mode. It's really not that technically challenging if you follow appropriate safety protocols, as you should always be doing anyways.
 
Last edited:
Top