Ejection charge

[AfterBurners]

I never thought of this until I read a thread somewhere, but here's my question.

I'm going to been using MADCOW's 4" Patriot for my L2. The nose weight comes in at about 33oz and according to ROCKSIM the ejection at Apogee is perfect. 0.00 MPH at velocity.

Would the ejection charge from a J500-10 be enough to separate the nose cone and payload from the rest of the rocket?

I never built any rocket with this much nose weight and just wanted to make sure.

Thanks guys, I know it sounds like a stupid question.

 

[jcamhale]

I would use this ejection charge calculator to see how much BP it says you'll need, then compare that with the what the reload comes with. The Aerotech loads come with around 1.4 grams IIRC. Don't worry about the nose weight. I used the same size charges in my L3 rocket after adding about 9lbs to the nose.

 

[crossfire]

2 grams of BP in the Patriot will work out fine. I am very surprised you need over 2lbs in the nose. I fly mine all the time with no nose weight and it always fly straight.

 

[AfterBurners]

2 grams of BP in the Patriot will work out fine. I am very surprised you need over 2lbs in the nose. I fly mine all the time with no nose weight and it always fly straight.

Gary - I know kinda scary, but according to RS and the CP and CG are right where they should based on a fully loaded rocket. I also balanced the rocket on the back of a chair and it's on the numbers.

 

[AfterBurners]

I'll post the RS file and you can look at it. I never built the rocket and I was just following the instructions where the CP and CG should be at

 

[kcobbva]

First, only stupid question is that not asked. Have you ground tested this with the charge to ensure it separates as you desire? I always start with the BP calculators, but there times I only get a thump sound and the rocket sits there. At that point I'm SO GLAD I ground tested. Up the BP until I get the separation I want and feel much better going into the field....especially for a certification flight. Just my 2cents.

 

[AfterBurners]

First, only stupid question is that not asked. Have you ground tested this with the charge to ensure it separates as you desire? I always start with the BP calculators, but there times I only get a thump sound and the rocket sits there. At that point I'm SO GLAD I ground tested. Up the BP until I get the separation I want and feel much better going into the field....especially for a certification flight. Just my 2cents.

No I haven't ground tested, but I will when I'm ready. Thanks again

 

[crossfire]

Like they say the numbers don't lie. It just seems adding 1/3 of rockets weight is a lot.

 

[rharshberger]

The Patriot may qualify as a "short and fat" rocket and need the RocSim work around using a phantom cone to get an accurate sim which could reduce the nose weight considerably.

 

[AfterBurners]

Here's the file as promised. For those f you who have RS your feed back is appreciated.

View attachment patriot.rkt

 

[AfterBurners]

The Patriot may qualify as a "short and fat" rocket and need the RocSim work around using a phantom cone to get an accurate sim which could reduce the nose weight considerably.

A "Phantom" cone that's just swell. I already have the rocket built and why haven't I heard of a "Phantom" cone before. Maybe this L2 is going to be a press and pray flight??

 

[T-Rex]

The phantom cone is said to be used on short and fat rockets, ones with a length to diameter of less than 10:1. The MCR Patriot is 52.5" tall, or 13:1.
I am at work and don't have the correct ork file (that matches my build) with me, but I also added a brick into the nose of mine as well. I have yet to get brave enough to fly it, something just doesn't seem right.

Using the file that I have available, without nose weight & using the AT J500G-10, OR says negative .306 calibers of stability. Adding 15oz of nose weight yields +1.06 calibers. 33oz yields 2.2 calibers, but it shows a 12sec delay should be used.....
Course, I don't have all the particulars of the OP's. (OOOPS, yes I do, see below)
Afterburners: Yes, it will fly, just maybe not fly as high or as fast maybe it could have. (not that the difference between 3900 feet and 4600 feet is visible from the ground)

YMMV

OOOOPS.......Just saw your rkt file. Open Rocket still shows 12.7 seconds delay. Using the 10sec delay, deployment speed is 88.8ft/sec

 

[AfterBurners]

The phantom cone is said to be used on short and fat rockets, ones with a length to diameter of less than 10:1. The MCR Patriot is 52.5" tall, or 13:1.
I am at work and don't have the correct ork file (that matches my build) with me, but I also added a brick into the nose of mine as well. I have yet to get brave enough to fly it, something just doesn't seem right.

Using the file that I have available, without nose weight & using the AT J500G-10, OR says negative .306 calibers of stability. Adding 15oz of nose weight yields +1.06 calibers. 33oz yields 2.2 calibers, but it shows a 12sec delay should be used.....
Course, I don't have all the particulars of the OP's. (OOOPS, yes I do, see below)
Afterburners: Yes, it will fly, just maybe not fly as high or as fast maybe it could have. (not that the difference between 3900 feet and 4600 feet is visible from the ground)

YMMV

OOOOPS.......Just saw your rkt file. Open Rocket still shows 12.7 seconds delay. Using the 10sec delay, deployment speed is 88.8ft/sec

Looks like I'm just gonna have to pull the trigger and let it rip off the pad! I think it will be OK Hmmm should I paint it? :confused2::lol::lol::lol: