Recovery system calculate (black powder grams)

[Burak]

Hello Ladies and Gentlemens. I am new for rocket science and this forum site.
I have a problem. I cant calculate black powder grams. Can you help to me?

My designed rocket;
** 16 cm diameter
** 25 kg weight (with engine) -(19 kg without engine)
** Firtst body height 158 cm
** First body's weight 13 kg (with engine)
** That recovery system work 600 meters height

My problems;

My problems;
1) I found a formule but i don't know if it is true. (P.V = m.RT) I didn't find to Pressure. Which one necessary for me?
Pressure is F / A ==> (m.g) / (π.r ^ '2) "That m (weight) is all weight or just first body weight ??"
2) Which height (cm) should i choose cylinder length. (48cm or all first body 158cm).
3) I found calculete sites but i didn't find enough P (pressure-psi). Which value is enough for me?

 

[Burak]

I found 1.5 Grams black powder for this rocket. But i am not sure 1.5 grams looking not enough.

 

[Nytrunner]

This calculator has been very useful. You will have to convert the diameter and length of your internal area into inches.

Determine how much pressure you need to generate to ensure deployment, and convert that to PSI

https://www.rockethead.net/black_powder_calculator.htm

 

[Burak]

This calculator has been very useful. You will have to convert the diameter and length of your internal area into inches.

Determine how much pressure you need to generate to ensure deployment, and convert that to PSI

https://www.rockethead.net/black_powder_calculator.htm

Firstly thank you for answering. I'm sorry there ara same questions still. (I gave my rocket informations on first text)

**(What is the length of the parachute section in inches ?) My height is 48 cm or all first body 158 cm?
**(How many PSI of pressure do you need ?)
1 Psi = 6894.75 Pa and
Pa= kg/(m.s^2) "my question is my kg is 19 kg or else?" and "m.s^2 is 9.81?''

if this calculate true. I found 0.0002364115 psi

 

[rcktnut]

You use the size of payload section = 48cm. 7psi (upper end) = 1.8 grams bp. Using 1.75 grams for your first ground test should be good. Adjust from there.

 

[Burak]

You use the size of payload section = 48cm. 7psi (upper end) = 1.8 grams bp. Using 1.75 grams for your first ground test should be good. Adjust from there.

Thank you so much! Can i learn to solution? How did u find 7 psi. This been a big problem for me. And if you share, i want to learn to solve.

 

[tim cubbedge]

There are a few calculators out there that will give you ball park starting loads.
https://hararocketry.org/hara/resources/how-to-size-ejection-charge/
https://www.rimworld.com/nassarocketry/tools/chargecalc/index.html
https://www.rockethead.net/black_powder_calculator.htm

 

[Burak]

There are a few calculators out there that will give you ball park starting loads.
https://hararocketry.org/hara/resources/how-to-size-ejection-charge/
https://www.rimworld.com/nassarocketry/tools/chargecalc/index.html
https://www.rockethead.net/black_powder_calculator.htm

I checked all of them. I searched before. I calculated from Pascal(pa) and ı converted to Psi. But ı dont know what is problem. I want learn to calculate.

 

[rcktnut]

Good to want to learn the calculations, but I only know the easy way. Just enter dia. of your payload bay(6.25) in inches and it gives you the psi range. I used this calculator:https://www.rockethead.net/black_powder_calculator.htm I always use the high end calcs and add a little more for the first ground test. In most cases I ended up adding more yet after ground testing to achieve the desired results. Your first figure in post # 2 is good, but .25 g more will not hurt.

 

[hartlch]

Thank you so much! Can i learn to solution? How did u find 7 psi. This been a big problem for me. And if you share, i want to learn to solve.

You need to estimate how much force you want to apply to force the nosecone out. You said your diameter is 16cm = 6.3inches, so the area of the base of the nosecone is: Area=pi * radius^2 = 3.14 * (3.15)^2 = 31.2 in^2. So 31.2 in^2 * 7 psi = 218 pounds of force on the nosecone.

I hope that helps explain the question you had about where the psi values come from in the online calculators.

Chuck

 

[Burak]

You need to estimate how much force you want to apply to force the nosecone out. You said your diameter is 16cm = 6.3inches, so the area of the base of the nosecone is: Area=pi * radius^2 = 3.14 * (3.15)^2 = 31.2 in^2. So 31.2 in^2 * 7 psi = 218 pounds of force on the nosecone.

I hope that helps explain the question you had about where the psi values come from in the online calculators.

Chuck

Yess! Thank u