More on Alternative ejection charge ideas

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Dec 31, 2002
Reaction score
Along with the building season, the Winter months bring on the testing season as well. This testing season I will hope to find alternative methods for ejection charges that will keep me legal within the eyes of the ATF, without having to get a LEUP.

On another list I am following, there is some discussion on this subject, so I thought I would re-open it here on the Forum.

I have Pyrodex P (pistol), and I will be looking into some smokeless powders as well from local gun shops to see what my options are.

Along with ejection charges, the e-match must be taken into concideration as my favorite oxrals are on the ATF's hit list. On the top of this "to be tested" list of items to try are the forever available Christmas tree light bulbs:

There has been debate about the fragile nature of the filament in a Christmas tree light bulb, but I have found some methods that help protect the filament, and make them very useful. I have not tested these methods yet, that is what I hope to do this Winter.

What might this group suggest for smokeless powders, or other powders that are not on the ATF list, that I might look into testing?

What tests have others here on the Forum tried in order to obtain alternatives to black powder?

where there is a will, there is a way...
BP is tough to beat. maybe some type of co2 cartridge or something. but that would have to be electronically controlled. possibly a servo that nudges the entire packed chute shock cord and NC out of the rocket. but again, it would weigh a lot more than BP. flash powder would probably blow your rocket apart, pyrodex is the safest alternative if you're going for a low explosive ejection. you could try making sugar propellent which is extremely safe, however, in my experience it doesnt deflagrate with much speed. i'd just go with pyrodex, there are so much less restrictions on it than BP and it works fine. just remember not to put too much in. ;)
I've been playing around with Christmas light bulbs quite a bit. After many, many static tests, I've had zero failures. But, I've not done any tests as far as simulating the effects of G forces, and forces from multiple deployment events.

One thing I have found. I've been using an Estes control for my tests. Upon doing continuity tests, there is enough current to light the bulb, although it's very dim. The longer the continuity is held, the brighter the bulb gets, eventually leading to the charge igniting.

My two main areas of concern, are the forces on the element during boost and drogue deployments. And, the bulb staying in it's socket during boost and drogue.
Originally posted by r1dermon
BP is tough to beat. maybe some type of co2 cartridge or something. but that would have to be electronically controlled.

I've been collecting information on doing this. Looks like to experiment with it I'll need to buy and tear apart a CO2 powered gun. Hey, whatever it takes.
BP is tough to beat indeed, but if you can find an alternative, thats great:)
Hot gluing a Christmas tree light bulb (CTLB) into a drinking straw, and then sealing the charge in on the opposite end with a tissue paper plug and hot melt glue again makes for a nice charge, as proven on Richard Nakka's site. Also placing the charge on it's side and securing the charge to the bulkhead that it is firing from should help minimize shock from: lift off g-forces, and drogue chute ejection shocks.

I make reloadable ejection tubes from 1/2" dia. brass tubes. These are mounted into the bulkhead of the avionics bay, and in turn it become a "cannon" if you will. One end is roughed up on the inside, and filled 1" deep with 30 min. epoxy. When this cures, I drill an 1/8" dia. hole down thru the center to allow e-match lead access.

The strength of the brass tubes should allow for confinement of slower burning powders like Pyrodex P...

Pics are worth a thousand words, so I will try to get some pics of my homemade ejection tubes.

BP has been a great and reliable staple for rocketry, and I still have lots of it left in my ammo can. But I will pass my quantities on to the LEUP holders in our club, as soon as I can reliably test a suitable replacement.

Co2 is expensive and bulky. The system currently available still needs a BP charge and e-match to activate.

Spring loaded, or servo activated systems are weak, bulky, or again expensive...with further adavancements these could become very nice systems in the future.

Candy propellant ejection???:confused: Will definetly set fire to eveything in the system including the airframe, before it will eject. r1dermon is right, in that it does not burn fast enough...but it will make for a nice smoke trail at drogue ejection for visual tracking...
Johnny, where bouts on Nakka's site is the light bulb technique at? I've been searching, but, man, there's a great deal of info on his site!
i have gutted out a paintball gun to try and tweak it, but it will only go so far. the valve needs to be bigger to let more air through. and one shot in stock form would'nt blow a nose cone off of a 3" or larger diameter least, im guessing it wouldnt. plus, it would weigh a lot more than a gram of BP.
There is mention of work going on of a group developing a spring loaded airframe that seperates after a pin is pulled free by a servo. So many parts dependant on one another leaves some room for error, but it was mentioned that this group is making great progress.

Also mentioned and worth looking into, are those little .5" diameter Pyrodex pellets. The idea of stacking these on an e-match and igniting them for ejection has thought merrit, but really has not been tested.

I mention these ideas, and these are actually being concidered for deployment at higher altitudes where BP ejection charges are all but useless. The above mentioned ideas are ideas that will produce ejection beyond 20,000 feet plus altitudes. If these would work for high altitudes, they may make great Legal replacements for general rocketry use.

A Co2 system would require that a rocket be built around the ejection system. I like building my rockets around the power plant (i.e. the Motor) The bigger the rocket, the bigger the motor, the heavier the rocket, the bigger the motor...sometimes the bigger motor is a good thing, but not if it is needed to just to loft the same project off the ground because the ejection system is so bulky...

So with that said, parameters might need to be set for alternative ejection projects:

Low cost / all though Pyrodex and some other generic powders are more expensive than BP, this is what your new low cost ejection experiment will be based from.

Effeciency / Must have the same effeciency as BP, because we know how BP works, so your design would need to work the same.

Should be able to retro fit all or most of your fleet. Keeping in mind, that most reloadable motors will come with their own BP charges and should NOT be replaced with any of the generic powders...

...which leads us to the next parameter, these are for altimeter ejection only! As long as motor mfg's will still ship reloads with BP charges, then use them. I know that some reloads come without, and it would be assumed that you are using altimeter deployment in these instances. A well designed alternative would be well placed here.

Listening in on the same forum talking about high altitude deployments, I have picked up on another generic powder I would like to get and test, it is called Triple 7.

Man I Love Winter projects, I'll be popping nose cones all winter long...:D and reporting back of course!
I haven't seen it mentioned here, but this has been done by Rouse-Tech. Altitude Tests/TABLE_CONTNETS.htm

RCS Offering the Rouse-Tech Line of CD3 Deployment Devices
RCS is pleased to announce that it is now an authorized dealer for the Rouse-Tech line of CD3 Rocket Recovery Deployment Devices. The Rouse-Tech system uses a small sealed black powder charge and piston to puncture a CO2 cylinder, thereby releasing a large volume of cool gas to deploy a parachute or other recovery device. The system is especially effective when used in rockets reaching altitudes in excess of 20,000 feet. At those altitudes and beyond, black powder and other pyrotechnic charges have demonstrated a tendency to burn erratically or "snuff out" due to the low ambient pressure. The Rouse-Tech device is designed to function reliably in a vacuum. Several different sizes are available for use in a wide variety of rocket vehicles. The Rouse-Tech system was recently used in John Rockdale's record setting 2-stage 'M'-class flight to 44,958 feet at the Black Rock Desert near Gerlach, Nevada

The down side (to me) is that it still relies on BP to make it happen. He's not really trying to get away from it, just to be more reliable at higher altitudes. IIRC there are multiple sizes available.
The down side (to me) is that it still relies on BP to make it happen. He's not really trying to get away from it, just to be more reliable at higher altitudes. IIRC there are multiple sizes available.

Correct, the downside is that the system does still depend on BP and ematch for election and recovery. These systems are great for high altitudes where BP is useless in a thinner atmosphere.

Welcome to the forum lotekrockets!

Since I will be working on a BP replacement this winter, it would be interesting to know if a replacement could be found for the BP and ematch in this system? At $234.00 for a full kit, it is still a little pricey for a direct replacement ejection source.
I have to agree with you. I see it fills that niche for high altitude, but some folks want to divorce BP entirely. I keep trying to work up something in my head, but the problem is if you use a spring fired pin to puncture a CO2 cartridge by pulling a solenoid, there would be a good deal of tension on the solenoid that would prevent you from being able to energize it. An electro-mechanical engineer might be able to come up with something. It would need to be simple, fewer parts means fewer chances of failure. Not the sort of venture I imagine many businesses would be insterested, not a lot of potential customers.
There's no need to reinvent the wheel, it just needs to be repackaged.

The military has been using pyrotechnic charges for 60 years at high altitudes and they work just fine. The trick, and it's no secret, is that the charges have to be in a sealed container at sea level pressure to get a good ignition of the BP. I advised the FIT JAMSTAR team on high altitude recovery methods. The did a lot of ground tests and proved that their implementations worked. The details can be found at the following webpages.

You can't use a standard drogue chute at high altitudes because the air density is to low to inflate it quickly and the shrould lines are likely to wrap around the rocket. This problem is solved by using a square cone parachute or ballute witha single shroud line that will inflate at high altitudes. Each day hundred of dropsondes are lifted by weather baloons to 100 Kft and released uisng square cone parachutes. Dropsonde RD93 datasheet.pdf

A sealed BP container is simplier, cheaper, lighter in weight, and more reliable than any of the other methods for high altitude deployments. There's no need to use a pressurized gas deployment system.

Bob Krech
im just taking an educated guess here bob, that if BP is in a pressurized container which is surrounded by a lower pressure atmosphere, then that container has to be AIR tight. with an AIR tight container filled with BP contained inside another structure(a body tube) wouldnt the shock of that presurized container rupturing rip the other container(the body tube) apart due to the initial expansion of gas? when BP is allowed to pressurize its container, it can explode with a lot more shock than it could uncontained. stronger bulding materials might be a solution to that problem, or a loose fit nose cone, but wouldnt the air inside the BT expand due to the lack of pressure and pop that NC off the top of the BT as it pressurizes due to the decrease in pressure?
The short answer is no. If you do it correctly, nothing happens to the rocket.

First. BP does not explode. It burns.

Second. The burn rate of BP is pressure dependent. More heat can be transfered to unburnt BP particles at high pressure than low pressure. In a vacuum very little heat is transfered, and most particles don't even light.

Third. Burning BP generates hot gases. As long as all the particles are burnt, a given weight of BP generates the same amount of gas independent of the combustion pressure, and thus will generate the same pressure rise in the body tube indendent of internal or external pressure.

Four. I'm not talking about making a grenade where the case stays together until the internal pressure peaks and then fragments. I'm basically making a burst diaphragm that fails at a few atmospheres pressure. A lot of people use centrifuge tubes as BP containers. 2 layers of electrical tape will hold the air in the tube at altitude and basically melt/burst when the BP burns. Once a grain is lit, it will burn. The trick is to get all the grains lit before the pressure drops.

You can even use the test tube method shown at Aerocon. Use an e-match or christmas tree light bulb filament, BP, a foam sponge as a compression element and drill several holes on the test tube. Use two wraps of scotch tape to cover the holes and keep the air in. The BP will burn, melt/ break the tape and you pressurize the rocket without any pieces blowing holes in the side of the rocket.

Bob Krech

Good work with the Jamstar projects, and the work with creating ejection in higher altitudes. BP for sure is a hard component to try to replace reliably.

I have obtained some small plastic containers like those that Pratt Hobbies is marketing. These housed mil-spec contacts for some Amphenol connectors we use here at work. They are about the same size as Doug's, but do not come to a point. They have attached / hinged lids too.

My soldering is feeble at best, but this winter Iwould like to try a variety of methods of creating my own liscense free ejection system, that will be reliable up to and including 10,000 ft.


I tried linking to the Perfect flite pdf file, but I do not think my dial-up liked it very much. I will try to access it from work tomorrow.