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We do not encourage new hobbyists to start out by making their own propellants, but we do encourage you to find a club and express your interests. And for the most part, the only organization that allows research propellant is Tripoli and you must be level 2 certified. We can’t tell you what to do, but whatever you do, do it safely.
 
Hello @dhuildo
I would stay away from Rcandy if you begin in rocketry. We have 2 Tripoli prefectures in France:
- Tripoli France which is up north
- Tripoli Southern France also known as Rocketry France which launches mainly in the south but members are all over France.
I am myself a member of Rocketry France so if you want to meet up send me a PM
Regards
Boris
 
bdureau said:
Hello @dhuildo
I would stay away from Rcandy if you begin in rocketry. We have 2 Tripoli prefectures in France:
- Tripoli France which is up north
- Tripoli Southern France also known as Rocketry France which launches mainly in the south but members are all over France.
I am myself a member of Rocketry France so if you want to meet up send me a PM
Regards
Boris
Click to expand...
Hello I'm french too, and I would like to create an hybrid rocket, is it an obligation to do sugar rockets as steps ?
 
Antares JS said:
No.
Click to expand...
Ok cool !

I have two questions then, about the project CROSSMOSHPER (name of the rocket we would like to create) :
- Is it possible to use the expander cycle, but instead of turning a turbine we re-direct the heated fluid into the tank in order to increase the pressure and accelerating the liquid ? It would create a kind of close pressurised/expander cycle ?
- In order to increase the ISP and the regression rate of a PLA hybrid rocket I had the following idea : what about puting a 3D printer in a closed box with an atmosphere of 2 bar of dihydrogen. Then we create little bubles into the rocket fuel that will be full fill by dihydrogen. something of this kind.
 
mael said:
Ok cool !

I have two questions then, about the project CROSSMOSHPER (name of the rocket we would like to create) :
- Is it possible to use the expander cycle, but instead of turning a turbine we re-direct the heated fluid into the tank in order to increase the pressure and accelerating the liquid ? It would create a kind of close pressurised/expander cycle ?
- In order to increase the ISP and the regression rate of a PLA hybrid rocket I had the following idea : what about puting a 3D printer in a closed box with an atmosphere of 2 bar of dihydrogen. Then we create little bubles into the rocket fuel that will be full fill by dihydrogen. something of this kind.
Click to expand...

1. What exactly is the point of this? I don't really understand what you're getting at here. You might be better off asking this question in one of the hybrid threads in the propulsion sub-forum. Offhand though, it sounds to me like unnecessary complexity that's going to create more problems than it solves.

2. Sorry, but that is a terrible idea. I guarantee you that having a bunch of little hydrogen bubbles in your fuel grain will cause each bubble to produce a small explosion when it's penetrated that will, at best, cause your motor to sputter and not produce consistent thrust, and at worst, cause the whole motor to fail.

It's also worth noting that while hydrogen does have the highest specific impulse possible of any chemical propellant, that does not mean it is the best fuel to use in any situation.
 
Antares JS said:
1. What exactly is the point of this? I don't really understand what you're getting at here. You might be better off asking this question in one of the hybrid threads in the propulsion sub-forum. Offhand though, it sounds to me like unnecessary complexity that's going to create more problems than it solves.

2. Sorry, but that is a terrible idea. I guarantee you that having a bunch of little hydrogen bubbles in your fuel grain will cause each bubble to produce a small explosion when it's penetrated that will, at best, cause your motor to sputter and not produce consistent thrust, and at worst, cause the whole motor to fail.

It's also worth noting that while hydrogen does have the highest specific impulse possible of any chemical propellant, that does not mean it is the best fuel to use in any situation.
Click to expand...

1- The purpose is to bypass the turbopump which is in my point of view seems to be more complicated to do for student than what I'm talking about. The idea is simplier to do I think (I'm not a professional at all), because you just have a valve programmed with the purpose to inject just enough hot fluid into the tank to have the good pressure.

2- Ok it's just I tried to do the stoechiométric equation and thought it was a good idea. I thought that by making a looooot of liiiiiiitle buble we would be able to bring constantly the same amount of hydrogen.
 
mael said:
1- The purpose is to bypass the turbopump which is in my point of view seems to be more complicated to do for student than what I'm talking about. The idea is simplier to do I think (I'm not a professional at all), because you just have a valve programmed with the purpose to inject just enough hot fluid into the tank to have the good pressure.
Click to expand...

1. I'm not an expert on hybrids, but I'm 99% sure the liquid oxidizer can just be pressure fed and require no pumping mechanism in the first place. Again, I would suggest asking in one of the hybrid threads in the Propulsion sub-forum, or starting your own thread with your questions. There are a few people around who know a lot more about hybrids than me and could probably help you get your injector figured out.
 
Hello mael and welcome,

In theory, hydrogen bubbles in a hybrid fuel grain would increase specific impulse. In practice it will not be possible to embed enough hydrogen to make a measurable increase. Consider, for example, a fuel grain 10 cm in diameter and 1 m long. Of course there must be some solid fuel between the bubbles, but even if it was all hydrogen (no solids at all) at 2 atmospheres pressure, that would correspond to approximately 0.7 grams of hydrogen. If the fuel grain was half hydrogen and half solid fuel by volume, you would have just 0.35 grams of hydrogen in the fuel grain.

Hydrogen bubbles would probably increase the regression rate, but it would be extremely difficult to get consistent results from one fuel grain to the next. The number and size of bubbles would have to be the same each time in order to get the same burn rate.

Sorry to burst your bubble (no pun intended :)), but it is often the case that ideas in science sound great until the calculations are performed...

Best regards,
Terry
 
prfesser said:
Hello mael and welcome,

In theory, hydrogen bubbles in a hybrid fuel grain would increase specific impulse. In practice it will not be possible to embed enough hydrogen to make a measurable increase. Consider, for example, a fuel grain 10 cm in diameter and 1 m long. Of course there must be some solid fuel between the bubbles, but even if it was all hydrogen (no solids at all) at 2 atmospheres pressure, that would correspond to approximately 0.7 grams of hydrogen. If the fuel grain was half hydrogen and half solid fuel by volume, you would have just 0.35 grams of hydrogen in the fuel grain.

Hydrogen bubbles would probably increase the regression rate, but it would be extremely difficult to get consistent results from one fuel grain to the next. The number and size of bubbles would have to be the same each time in order to get the same burn rate.

Sorry to burst your bubble (no pun intended :)), but it is often the case that ideas in science sound great until the calculations are performed...

Best regards,
Terry
Click to expand...
Hey thanks for your answer, really !

It's why in my message I'm talking about a higher pressure than 1 atm. So I was thinking about it : C³H⁴O² + 7O + H² --> 3CO² + 3H²O (this must be false too).

Then with some calculations maybe also false I found that : 3,6kg of PLA, 5,2kg of Lox, 100g of Hydrogen.

So I was thinking that by introducing hydrogen with a high pressure in bubles all among the helicoidal fuel printed we would be able to create a flying PLA rocket lol.
 
One other thing to consider is that 3d printed pla is generally porous...
 
Yes, much of it will leak out as soon as the closed print box is depressurized.
 
Except if inside the closed box there is metal walls that we put around the fuel once it's printed ?

This is a not an idea I worked on to be honest, because I just imagined it in case of if the pressure was to highfor the buble's wall.
 
ps sorry for my english tell me if you want me to explain again !
 
Antares JS said:
1. I'm not an expert on hybrids, but I'm 99% sure the liquid oxidizer can just be pressure fed and require no pumping mechanism in the first place. Again, I would suggest asking in one of the hybrid threads in the Propulsion sub-forum, or starting your own thread with your questions. There are a few people around who know a lot more about hybrids than me and could probably help you get your injector figured out.
Click to expand...
A real thank for your time !
 
I think your English is fine.

As much as propellant talk can get you really far into the weeds, there is much more to learn about rocketry, and that learning is far more accessible, in the realm of airframe design. That’s why Scaled Composites claimed the Ansari X Prize in 2004 with famed aeronautical engineer Burt Rutan in charge of developing the airframe (spaceframe?) and the propulsion system development falling to the lowest bidder. The other entries focused on novel propulsion technology and for the most part they STILL haven’t gotten off the ground.

I imagine that it was pretty embarrassing for those competitors to have Estes sport scale models of their spacecraft running on black powder end-burners get higher than the real things.
 
smstachwick said:
I think your English is fine.

As much as propellant talk can get you really far into the weeds, there is much more to learn about rocketry, and that learning is far more accessible, in the realm of airframe design. That’s why Scaled Composites claimed the Ansari X Prize in 2004 with famed aeronautical engineer Burt Rutan in charge of developing the airframe (spaceframe?) and the propulsion system development falling to the lowest bidder. The other entries focused on novel propulsion technology and for the most part they STILL haven’t gotten off the ground.

I imagine that it was pretty embarrassing for those competitors to have Estes sport scale models of their spacecraft running on black powder end-burners get higher than the real things.
Click to expand...
Sorry I don't see what is your point there ?
 
mael said:
Hey thanks for your answer, really !

It's why in my message I'm talking about a higher pressure than 1 atm. So I was thinking about it : C³H⁴O² + 7O + H² --> 3CO² + 3H²O (this must be false too).

Then with some calculations maybe also false I found that : 3,6kg of PLA, 5,2kg of Lox, 100g of Hydrogen.

So I was thinking that by introducing hydrogen with a high pressure in bubles all among the helicoidal fuel printed we would be able to create a flying PLA rocket lol.
Click to expand...
There is no way that 100 g of hydrogen could be contained in 3.6 kg of PLA or any other plastic. Also, the higher the pressure of the hydrogen, the faster it will diffuse out of the PLA.

The first US space booster to use liquid hydrogen was the second stage (Centaur) of the Atlas-Centaur rocket. NASA had to develop new welding techniques for it...because the small size of the hydrogen molecule caused it to leak rapidly through cracks even smaller than 0.001 mm. And gases diffuse roughly 1000 times faster than liquids.

How long do you think it will take for gaseous hydrogen to diffuse out of bubbles in a porous plastic? I will hazard a guess: much less than one second; probably closer to a millisecond.

I taught college and university chemistry for 42 years. One thing I tried to teach students who wanted to do research: do as much of the calculation and theoretical work as possible before starting work in the laboratory. Lab work is long and laborious. A few hours of calculations will save (literally) months of practical lab work.

Regards,
TWM
 
prfesser said:
There is no way that 100 g of hydrogen could be contained in 3.6 kg of PLA or any other plastic. Also, the higher the pressure of the hydrogen, the faster it will diffuse out of the PLA.

The first US space booster to use liquid hydrogen was the second stage (Centaur) of the Atlas-Centaur rocket. NASA had to develop new welding techniques for it...because the small size of the hydrogen molecule caused it to leak rapidly through cracks even smaller than 0.001 mm. And gases diffuse roughly 1000 times faster than liquids.

How long do you think it will take for gaseous hydrogen to diffuse out of bubbles in a porous plastic? I will hazard a guess: much less than one second; probably closer to a millisecond.

I taught college and university chemistry for 42 years. One thing I tried to teach students who wanted to do research: do as much of the calculation and theoretical work as possible before starting work in the laboratory. Lab work is long and laborious. A few hours of calculations will save (literally) months of practical lab work.

Regards,
TWM
Click to expand...
Thanks a lot for your answer !

Now you say it it seems prety obvious haha
 
The two simplest methods I'm aware of for increasing blowdown pressure would be dissolving a gassier oxidizer ( e.g. 5% GOX in NOS ) and wrapping the tank with a heater of some kind.

But, if I may offer some advice -- just go fly! There's no substitute for time spent on the range drawing experience from other rocketeers.
 

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