Ejection Charge

Hello, I'm a new user to this forum, and I have a question on ejection charges.

I'm building a large 4.5 foot tall rocket with a 4'' inch diameter, that weighs about 2.50 pounds.
This is one of the largest rockets I've built, and the previous ones didn't need ejection charges to pop the nose cone off in flight.
Could someone tell me what I should do, because I never used ejection charges and I feel insecure even thinking about using them, if I have to is there a alternative?

P.S.
The nosecone is also very large, about 20 inches, and weighs a bit,
my parachute is 48'' and has a total area of 10.5 feet

Can we get some more information? Are you using an altimeter to fire the ejection charge? What kind of motor are you using? Where are you located? There may be a club near you that you could get assistance from.

You should be able to get a motor that will pop the top off that thing with no problem but like Zeus says, need more info about the rocket.

The LOC IV and LOC EZI-65 are popular 4" kits that are very similar to yours in size and weight. These 4" kits are designed for motor ejection deployment at apogee and do not need electronics. These kits are supplied with 36" chutes so your 48" chute might be a bit large so expect a longer than average walk for recovery.

I'm guessing you will need between 1.25 and 2.0 grams of BP to pop the chute. Depending on the design of your rocket and the engines you use, you may have to add a small amount of BP in addition to the BP ejection charge supplied with the motor. The instruction sheet supplied with the reload will describe how you do it.

I'm assuming you are launching with a club in Texas so you should be able to find a mentor to assist you. If you are not, you need to be aware that any rocket weighting more than 53 ounces on the pad, or with a motor (or motors) containing more than 125 gram of propellant are FAA class 2 rockets and require a formal FAA waiver, and the flier of a Class 2 rockets, or a Class 1 rocket with an H-impulse motor, needs high power certification from either NAR or TRA to launch at an organized launch.

Bob

I made a update post regarding this, I am in Texas, but not working with a club. My rocket meets all legal standards and does not require a L1 certificate. I can't legally buy black powder in my area though, so I'm going to need some help improvising. I have no electronics in so no to the altimeter, I'm just firing a simple rocket. I purposely got a 48'' chute so I can ensure a safe slow landing. Also I am not building off a kit, but my own design. I am thinking on using a engine with 100-150 n/s impulse too.

I get very uneasy when the first thing a stranger asks me is how to improvise explosive devices. Especially if you are not "working" with a club. Maybe you can show us a picture of your rocket, or other rockets you've built and flown.

If black powder is illegal in your jurisdiction (which part of Texas is this again?), there's nothing this forum can do to help you solve your problem. I encourage you to petition your government for redress of this grievance.

Ari.

Dunavice said:

Hello, I'm a new user to this forum, and I have a question on ejection charges....
This is one of the largest rockets I've built, and the previous ones didn't need ejection charges to pop the nose cone off in flight...

Click to expand...

This really doesn't sound like you have ever flown a "Rocket" with a store bought (Estes) motor.

If you are not flying with a club - you probably should.

I'm pretty sure he means seperate charges from the motor charge.

I'm not doing anything illegal, and I'm not too experienced to enter a club. I appreciate your comments but seriously I don't want to do this whole
thing where I have to fill out a bunch of applications and get a permit to handle BP or something.
This is also my first rocket, but I'm very experienced in R/C aviation, once I put the rocket together I'll show you a picture.

We all had a time where we were newbies, can't we just accept that?

Kind Regards

-Dunavice

I fully expect his next question to be about combining R/C "drones" with home-made explosives and rockets.

I strongly encourage OP to post some evidence of his hobbies, otherwise I'm reporting him as a troll. If the rocket is incomplete, he can post photos of his build in progress. Many members on this forum, including your humble narrator, do build threads. There's no shame in showing one's progress.

Ari.

Dunavice said:

I'm not doing anything illegal, and I'm not too experienced to enter a club. I appreciate your comments but seriously I don't want to do this whole
thing where I have to fill out a bunch of applications and get a permit to handle BP or something.
This is also my first rocket, but I'm very experienced in R/C aviation, once I put the rocket together I'll show you a picture.

We all had a time where we were newbies, can't we just accept that?

Kind Regards

-Dunavice

Click to expand...

Sorry, education and outreach are 2 major purposes for a club. The clubs senior members mentor newbies to become successful. It brings new folks into the hobby and prevents frustration. You don't even have to join many clubs to launch model rockets.

Clubs secure the launch permits, waivers and provide insurance for the landowners. They provide launch equipment for the fliers, and mentoring for newbies. At a launch, all rockets undergo a safety check before each launch which should catch any design flaws a weakness in the construction that would cause a failure.

You are required to use NAR/TRA/CAR certified model rocket motors at any organized launch if you are not high power certified. A model rocket motor by definition is a certified commercial motor that that a total impulse not exceeding 160 Ns (G-impulse), an average thrust not exceeding 80 N, propellant weight not exceeding 125 g (adult), 62.5 g (minor), and does not produce excessive sparks (no sparkies). Only Black Powder and APCP solid rocket motors are allowed.

Your rocket, if you have described it correctly, will have to be launched on a G-impulse motor with a minimum average thrust of ~60 N or higher (up to 80 N) and the apogee will range from approximately 500' to 1000' feet depending on the total impiulse of the motor chosen and the Cd (drag) for the rocket.

You should go to https://www.thrustcurve.org to assist you in the selection of your motor. Another free product you should download is Open Rocket. This is a free open source rocket design/drawing and simulation package. It is more accurate that the simple simulation provided by thrustcurve.

Another advantage of a club, is that may clubs have a motor vendor who stocks the most commonly used motors, or can get them for you. The advantage of the on-field vendor is that you do not have to pay for shipping and a hazmat fee.....and you don't have to maintain a large inventory of motors.....which are not usually sold in hobby stores.

It would really be useful if you posted a drawing of your design.

Bob

Dunavice said:

I'm not doing anything illegal, and I'm not too experienced to enter a club. I appreciate your comments but seriously I don't want to do this whole
thing where I have to fill out a bunch of applications and get a permit to handle BP or something.
This is also my first rocket, but I'm very experienced in R/C aviation, once I put the rocket together I'll show you a picture.

We all had a time where we were newbies, can't we just accept that?

Kind Regards

-Dunavice

Click to expand...

No, we can't just accept that your are a "newbie" without full confirmation that your motives are pure. You must first be fully vetted by the Inquisition. :eyeroll:

Dunavice said:

... I'm not too experienced to enter a club...

-Dunavice

Click to expand...

I really don't know what you are trying to say. Are you saying you don't have enough experience to join a club? That may be true with your experience in R/C clubs but rocket clubs tend to be very helpful in bringing those along in the hobby and typically welcome new members and visitors, at least that's the vibe for the club to which I belong, Tripoli Houston Rocket Club.

Speaking of, we are holding our next launch in Hearne, TX (just north of College Station along Hwy 6) this Saturday so you are welcome to come out and visit. Watching and learning is free. Let me know if you want more info about that.

Greg

Dunavice said:

Hello, I'm a new user to this forum, and I have a question on ejection charges.

I'm building a large 4.5 foot tall rocket with a 4'' inch diameter, that weighs about 2.50 pounds.
This is one of the largest rockets I've built, and the previous ones didn't need ejection charges to pop the nose cone off in flight.
Could someone tell me what I should do, because I never used ejection charges and I feel insecure even thinking about using them, if I have to is there a alternative?

I'm not doing anything illegal, and I'm not too experienced to enter a club. I appreciate your comments but seriously I don't want to do this whole
thing where I have to fill out a bunch of applications and get a permit to handle BP or something.
This is also my first rocket, but I'm very experienced in R/C aviation, once I put the rocket together I'll show you a picture.

We all had a time where we were newbies, can't we just accept that?

Kind Regards

-Dunavice

Click to expand...

Mmmmm.... which is it?


Dave


"Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.” - Einstein

48" long / 4" dia. at 2.5 lbs is probably too big and heavy for just about any motor that you can buy commercially without an HPR certification. Something like this on an Aerotech G80 (the biggest motor you can buy without a cert) is probably only going to go 1000', if that, and the velocity off the launch rail (it's too heavy for a rod, by the way) won't be suitable for anything except dead calm winds.

Sorry for all the un-needed attention, clearly this grew from a question to a flame war.

Replying to iter, I appreciate your time, but I don't even have the materials yet. I said I'm quote, "building" the rocket, as I have not done so yet.
I posted this thread because I am researching on what I need and how I should take out building the rocket, my R/C has nothing to do will rocketry, and I didn't
mean for it to either, it was simply a statement showing that I'm experienced in a form of aerospace. Here are the materials I'm using for the rocket

https://www.apogeerockets.com/Building_Supplies/Nose_Cones/High_Power_Nose_Cones/PNC_4_x_16-5_98mm
https://www.apogeerockets.com/Building_Supplies/Body_Tubes/High_Power_Tubes/3-9in_LOC_Body_Tube
https://www.apogeerockets.com/Build..._24in/48in_Nylon_Parachute?cPath=42_73_78_80&
https://www.apogeerockets.com/Building_Supplies/Bulkheads/Tube_Bulkheads/Tube_Bulkhead_Disk_98mm
https://www.apogeerockets.com/Build...overy_Equipment/Shock_Cord/Elastic_Shock_Cord
https://www.apogeerockets.com/Build...ent/Disposable_Wadding/Quest_Recovery_Wadding
https://shop.locprecision.com/product.sc?productId=90
https://www.apogeerockets.com/Rocke...otors/1_Grain_Motors/Cesaroni_P38-1G_Imax_G50
https://www.apogeerockets.com/Build...m_Body_Tubes/Centering_Rings_29mm_LOC_to_98mm

And I'm building the fins.

My design image won't upload so email me if your interested at [email protected]
As I said before, once I start actually building on the rocket I'll show you some pictures.
I know I know it's basic, but it will do.

Kind Regards to you and the "trollers" you claim you see

Dunavice

The simple answer to your question is that you don't need a separate ejection charge if you are using over-the-counter motors. Any motor you can buy without certification, including CTI G50, has a built-in deployment charge.

The longer answer is that you're making statements that contradict each other, and your intentions are obscure to me. Your component list is a hodgepodge that is unlikely to result in either stable or safe flight. If safe and stable flight were your goals, you'd be asking questions about safety and stability, but your chief concerns seem to center on avoiding clubs, regulation and paperwork. With that we cannot help you.

Ari.

I'll happily take my hodgepodge and my in-stable flight, thank you.

Ok folks, stop harassing the newbie. He's new to rocketry and attempting to build his first rocket. Giving constructive critical review is fine, but don't be insulting.

Bob Krech, TRF Administrator

Thanks Bob. Bob is right. You need to encourage our new poster.

To answer the initial question, I'd say, depending on parachute compartment size, somewhere around 2 grams ought to do it.

To address other things: There are two organizations for rocketry in the US. These national bodies negotiate with the government agencies (like the BATFE), and get fliers insurance while conducting launch operations in accordance with their safety codes. They are NAR and Tripoli.

At the local level, there are clubs. The club will usually be affiliated with one organization or the other (or both). Joining a club usually requires membership in one of the national bodies (they make it easy, you can sign up on-site [at least for Tripoli, I suspect NAR is the same {someone will correct me if it's not}]), primarily so you're covered under the insurance. Joining a club and going to the launches is, simply, the best way to become a more knowledgeable flier --and builder.

A club launch isn't a race meet. We're all, really, competing against gravity and the wind --and sooner or later, we all lose. It's rocketry: sometimes, they're lost, sometimes, they break, sometimes, well... they blow up. You don't need a specific set of chops to fly. If it works, you'll know. If it doesn't work... there's a whole flight line of troubleshooters there. "Parachute's too small... delay is too short... fins too thin, started fluttering... shear pins shoulda been #4-40... forward closure let go... actually tried to use a Copperhead..." I've heard all of these at the tent line.

I'm just saying: re-think joining and flying with a club, particularly if you're first starting.



Later!

--Coop

the ejection charge requirement is based on volume and pressure. The less volume, the less bp you need. We're looking for around 10 psi. Search for "BP calculators" and "rocketry" and you should find some on the web that will tell you approximately how much bp you need. if its more then 1.3, you gotta augment. if less, then you should be fine

Hope that helps.

I have to say, I've never add to add or remove BP to/from a single-use motor. They are predesigned to work with standard mid-power rockets. But then, I've never scratch-built, either. I stand with others who've said, start small and work your way up. You learn lots and lots from building and launching low power rockets. Time well spent, and fun, too.

Also, it seems that you are making a lot of decisions based on your limited budget. While we all have limits to what we can spend, never, ever do something unsafe just because you can't afford to do it safely. Take time, wait, get the right stuff.

There is nothing more frustrating than watching a rocket you spent weeks building blow up, and realizing that if you had spent more time and more money, it wouldn't have happened.

Good luck!

you know, I'm better with blowing one up (although I hate to loose rockets based on my own stupidity) more then drilling one in ballistic. Too much will generally get it down safely, whereas having one come in hot is a failure to be safe. It's a "darn" versus "oh, ****" thing.


JMHO

Dunavice said:

Sorry for all the un-needed attention, clearly this grew from a question to a flame war.

Replying to iter, I appreciate your time, but I don't even have the materials yet. I said I'm quote, "building" the rocket, as I have not done so yet.
I posted this thread because I am researching on what I need and how I should take out building the rocket, my R/C has nothing to do will rocketry, and I didn't
mean for it to either, it was simply a statement showing that I'm experienced in a form of aerospace. Here are the materials I'm using for the rocket

https://www.apogeerockets.com/Building_Supplies/Nose_Cones/High_Power_Nose_Cones/PNC_4_x_16-5_98mm
https://www.apogeerockets.com/Building_Supplies/Body_Tubes/High_Power_Tubes/3-9in_LOC_Body_Tube
https://www.apogeerockets.com/Build..._24in/48in_Nylon_Parachute?cPath=42_73_78_80&
https://www.apogeerockets.com/Building_Supplies/Bulkheads/Tube_Bulkheads/Tube_Bulkhead_Disk_98mm
https://www.apogeerockets.com/Build...overy_Equipment/Shock_Cord/Elastic_Shock_Cord
https://www.apogeerockets.com/Build...ent/Disposable_Wadding/Quest_Recovery_Wadding
https://shop.locprecision.com/product.sc?productId=90
https://www.apogeerockets.com/Rocke...otors/1_Grain_Motors/Cesaroni_P38-1G_Imax_G50
https://www.apogeerockets.com/Build...m_Body_Tubes/Centering_Rings_29mm_LOC_to_98mm

And I'm building the fins.

My design image won't upload so email me if your interested at [email protected]
As I said before, once I start actually building on the rocket I'll show you some pictures.
I know I know it's basic, but it will do.

Kind Regards to you and the "trollers" you claim you see

Dunavice

Click to expand...

Your rocket design, if built from your parts list, does not appear to work. You are building a midpower/high power rocket and it needs to be constructed differently than an estes rocket.

The Nose Cone is 16.5" long x 4" dia. and will fit on a 34" long x 4" diameter airframe. The NC costs $22 and the AF cost $11.50. The rocket will be 50.5" long x 4" diameter. Each component weighs 10.5 oz so the NC + AF weighs 21 oz. and so far costs $33.50. So far so good.

The 48" parachute may be a little large and weighs about 2+ oz. and costs $20 so the weight so far is ~23+ oz. and cost is $53.50 so far.

The next part is a 4" solid bulkhead that weighs 2- oz. and costs $4. I'm not sure why this part is there as a solid bulkhead is not required for a motor ejection rocket. Anyway the cost is now $57.50 and the weight is up to 25 oz.

The first big issue is your shock cord. It is totally inappropriate for a rocket of the size. Your rocket will weight about 3 pounds after motor burnout and your shock cord should support >=100 G loading = 3# x >=100 G = 300# or more. Tubular nylon or tubular Kevlar is appropriate but does not appear to be available from Apogee. Since is on the low end weight for a HP rocket, I'm guessing without looking that 3/8" to 1/2" tubular product about right for a rocket this large. If you have to use apogee, the 1500# Kevlar https://www.apogeerockets.com/Build...ecovery_Equipment/Shock_Cord/Kevlar_Cord_1500 is what you would purchase. The reason is that a braided product is likely to zipper the rocket and this braid is the thickest available at apogee. Kevlar is not stretchy so you want about 5x the rocket length or ~20'. That would cost about $18 and weigh 1+ oz. so the running cost is $75.50 and the weight is 26+ oz.

You do not use paper recovery wadding in rockets of this diameter. It doesn't work. You either use "dog barf" which is fireproof cellulose building insulation (never use fiberglass as it kill animals that eat it) or a Kevlar parachute protector. A large bag is available from your local home store for ~$10 and a 12" (3 x AF dia.) parachute protector is available from Apogee https://www.apogeerockets.com/Build...able_Wadding/Sunward_12in_Parachute_Protector They cost $10+ and weigh 1- oz. Your running totals are $85.50 and 27 oz.

Now you have to decide what size motor you want to use. You selected a 38 mm motor but selected a 29 mm motor tube. Doesn't work. A 38 mm motor tube is correct as you can still use 29 mm motors with an adapter, but this rocket will only launch safely on big G motors and L1 high power motor so the 38 mm motor tube is the proper selection. https://shop.locprecision.com/product.sc?productId=14&categoryId=19 The cost is $7 and 8" will weigh ~ 1 0z. so your cost so far is $92.50 and weight is up to 28 oz.

Now you need to motor mount bulkheads. https://www.apogeerockets.com/Build...g_Rings/Centering_Rings_38-98?cPath=42_46_240& TA pack of 2 costs ~$8+ and each weigh 1- oz. Cost is up to $101.50 and weight is up to 30 oz.

It is recommended that you use a 1010 rail as a launch guide so you need 2 railbuttons. https://www.apogeerockets.com/Build...l_Buttons/Rail_Buttons/1_Rail_Button_Standard Cos is $3 and don't worry about the weight. The cost is now $104.50 and the weight is 30 oz.

Now you need fins. The minimum thickness is 1/8" thick 5-ply aircraft plywood. https://shop.locprecision.com/product.sc?productId=279&categoryId=33 costs $5 per 6"x12"x 1/8" thick sheet. You will need 3-4 depending on number and method of attachment. Nominally you fins will have a 5"-6" span, a 6" length at the airframe and a 4" length at the tip. Each fin will weigh ~2+ oz. minimum so your cost is up to ~$120 and your weight is up to 37 oz. - 39 oz.

You need to add a motor retention system and a shock cord retention system. This will cost between $5 - $10 depending how you it and increase the weight 1 oz. to 4 oz. so the rocket is going to cost $125+ and the weight will be between 38 oz. to 43 oz. before painting.

Now you need to purchase the reload and the motor casing. From Apogee a 1G reload is $25 https://www.apogeerockets.com/Rocke...its/38mm_Motors/1-Grain_Motors?page=1&sort=4a and you will pay a ~$28 hazmat fee in addition to shipping costs, and you will need a Pro38 motor casing and DAT tool. You can buy a 1G casing and DAT from apogee for ~$45 if you buy them separately, however the better value is to purchase a Pro38 starter set https://www.apogeerockets.com/Rocke...gs/Cesaroni_38mm_Reloadable_Motor_Starter_Set for $114. This set include a 3G and 6G casing, 2 spacers and a DAT tool so that you can purchase any 1G thru 6G Pro38 reload and use it.

If you are under 18, the only Pro38 motor motor you can legally launch by yourself is the Pro38 1G G46 classic. If that is the case, you probably want to select Pro29 hardware and a LOC 38mm to 29mm adapter for ~$5.

The real problem with your choices are that the assembled motor will weight between 7oz. to 9 oz. so you're very close to the 52.9 oz. Class 1 rocket weight limit that both requires a waiver and high power certification. If you paint the rocket, you can be over the limit.

This is what you need. You can do better in price and weight if you purchase a 4" kit rather than scratch build, and if you have no desire to join NAR or TRA, I strongly suggest a 3" kit that is less expensive and will give you many more 29 mm motor options without bumping up the weight into a high power rocket.

Bob

And how does Bob know all that ... ? Experience!

Dunavice, welcome to rocketry! It's a great hobby, a lot of fun, and the rocketry community is generally very helpful and supportive. But, not to be discouraging, it does seem like you are diving right into the deep end without first learning to swim. And some of your questions seem to indicate that there are important things about rocketry that you don't know about, and you probably don't know you don't know. That's not meant to be condescending. It's to help you understand why people might be reluctant to answer a one-off question that seems to indicate larger problems about your overall design and plan.

Most rocketeers start off with kits instead of scratch building a mid-power to high-power rocket on their first try, and that is a really good idea! I'd strongly encourage you to get a kit, which will come with everything you need and will have a design that will be proven. It doesn't have to be a small balsa wood kit --- you could start with MPR if you want. But you should probably get your feet wet with a proven design, and then you'll start to understand the kinds of questions you'll need to be asking to do the projects you want to do. There's no reason you can't be scratch building MPR rockets soon, but it would be best to build a kit first.

Here is a great kit that is about the same size as the one you want to scratch build:https://www.hobbylinc.com/htm/aro/aro89021.htm

I have that rocket, and I love it! One of my all-time favorites! It is big and flies great. It is also pretty easy to build. You can find it for less than $70, and you can fly it on single-use Aerotech G motors and not have to get straight into reloadable motor systems right away.

I also have an Estes Leviathan, which I really like too. That's a 3" diameter kit. Easy to build, under $40, flies great! It can use Single-use Aerotech Econojet F motors, which will save you money, or G motors as well. This site sells the whole line of Estes Pro Series II kits, and they are all pretty nice affordable kits: https://www.acsupplyco.com/estes/pro_series.htm

This is just a tiny sampling of suggestions for great, affordable, fun MPR kits you could use to get your feet wet.

These kits can all be built stock and work great. But there are also modifications you can do, and if you are interested in scratch building, then maybe you be interested in doing some of the modifications. There are numerous threads about mods to these kits.

Getting back to your original ejection charge question, any of these kits will work fine with the standard ejection charge that comes with the motors used to fly them. No need for additional BP. Another good reason to go with a proven design.