This take me back to 2005/7. I helped build a filament winder to make some main spars for a wing. This was before arduino's and raspberry pi's. Had to make a hardwired control circuit controlling pneumatics. Working with resin and carbon fibre isn't easy. We made mandrels from aluminium, glass tubes and finally thin sheets of foam rolled into tubes. Keep on doing what you are doing - you'll learn a lot along the way.
Well done guys! The hardest part of engineering is never falling in love with a design. Well done on the COPV, looks great! Looking forwards to seeing how it performs. Best of luck!
Best material we have found for composites mandrels is UHMWPE or even HDPE would do. You can machine precise sizes for the inner surface and then freeze out the mandrel (it has higher thermal contraction than pvc)
Also carbon fibre sleeve is good as a thinner alternative for filament winding (tho can be more expensive) we have been experimenting with producing 60bar pressure vessels using it and so far has held well to over 75bar at 1.5mm wall thickness (tho we expect that is close to the limit)
@@robinbiskupic2639 This is actually one of the options we are considering for the fairings between the CC and the tank on the next rocket. However, this doesn't work for making a type 4 tank.
I'm at 6:03 and my first thought is rather than drilling holes through the carbon fiber, secure the endcaps independently of the CF. Whether tensile supports external to the CF tube between the endcaps, or making the endcaps part of the CF tank.
Hello Astra... I hope you read this, I wish I was part of the team to warn you about the cf winding because I was pulling my hair when I saw the holes in the carbon fiber. I want to thank you for showing how to cast a bronze nozzle because I have never seen/ hear of that before, but now the possibility for cheap regenerative cooling is within reach for model rocketry. As for the CF chamber winding, I suggest and please let me know if you disagree that you place rods in the location of the bolts in the mandrel that you are using for winding. You should wrap normally around these 3 rows rods and the fibers will find their way around them. Do NOT drill through fibers ever again because you are committing a great composite sin. After you finish the normal winding, I recommend concentrating on the ends and pass the fibers in between the rods (future bolt holes) to reinforce that region. After everything, you can cut or remove the rods and bolt the aluminum piece and I can guarantee that you will have absolutely near impossible to tear winding because it will be working in tension. As for the nitrous, you have used in the end an aluminum tank and wound cf over it (correct). You should have bought a plug and play car racing nitrous tank that is aluminum and already done to operate at 900psi-1400psi easily and safely. You are not using Lox nor pressurizing to 300bar, so a Cf is not necessary and an off the shelf aluminum or even Cf nitrous bottle would have been cheaper or the same cost. Please let me know if you disagree with any point or have any thoughts, keep up the good work. Cheers
Thank you for your super detailed comment. One of the best parts of putting a lot of our information onto to this platform is the feedback that we get. If it can also be useful to others sometimes, that is also great! For the chamber winding, I completely agree with you. Drilling holes in CFRP structures is not a very good move. To make it work, we had to use a 0.7mm thick Stainless Steel liner underneath the CFRP lay-up. We were toying around with your idea of winding around the holes last year, but we were struggling just to find the right methods for our design and never got around to trying it. Maybe we will take a crack at it this year now that we are not starting from 0. For the tank, we actually wound over a steel tank. We know that our method was very mass inefficient, but we were mainly concerned with figuring our how to wind with carbon fiber. To make the tank for the rocket that will go to space will require a 250mm x 5 meter tank. This is certainly not something you can get in aluminum off the shelf. Furthermore, we need to be able to meet a 3x SF to fly our rocket in Europe. Safety standards are very high here so CFRP is not so bad when you are required to hit 180 bar. If we were flying in the US we probably would never have bothered with CFRP. Again, thanks for the comment. I hope you continue to enjoy our channel. There is lots more interesting excitement to come this year!
This is the same problem with the Titan submersible, not enough axial strength in the carbon fibre layup. Lot's of hoop strength, but not enough axial, plus all those stress concentrations and holes aren't helping. If you build the tank with bell ends you keep the axial strength at the ends
Perhaps if the form was made out of a product that could be dissolved with a solvent like expanding foam coated with a release agent, you could make the ends of the tank and the walls in one winding. Then you're only dealing with one material interface at the valve. Winding the carbon fiber around a ribbed tube that the valve could be threaded on might work.
Could you solder/braze the thin sheet metal instead of welding or using a polymer on it? Need to look at electrochemical potential differences to avoid galvanic reactions.
Wow very good job 👏. Can't wait to see it fly .i have question Can't we use normal oxidizer like kno3 and sugar. And what was the source of the wax thanks
Well, you could use Potassium Nitrate and sugar as the propellants, but that would be a solid rocket. This comes with some challenges (especially safety and political in the EU). Basically, it is very difficult to get the authorization to use Potassium Nitrate in Germany. So, we opted to build and fly a hybrid rocket with Nitrous Oxide as the oxidizer and paraffin wax for the fuel. We also get a lot more specific impulse out of this combination, so that is nice too. The way just came from amazon - just regular candle wax. Nothing fancy! I recommend you check out some of our propulsion videos on the topic.
First, glad i found you here, i was wondering where the rocket projects are in Europe / Germany. My only critique point is, many problems could be resolved before they happend with proper planning, i think that's a key point where you need to work on. I am a bit sad that it is a student and not civil project, don't get me wrong, that's cool and all, but for a non student tinkerer its hard to get through the german bureaucracy to make a project like this happen. but hey, i will buy some shirts to support you. Besides that, i wish you all the best on your endeavors and much love from Hannover.
Thanks for the support! Is is much appreciated. There are many student teams throughout Europe that are working on high powered rocketry. I would invite you to check out EuRoC where many of these groups meet and fly rockets every October in Portugal. With respect to planning, yes this is definitely a weak point in our group right now. At the start of the project, we simply lacked the experience to make good engineering decisions and that made the planning a bit of a nightmare. But, we are hoping the experience we gained will give us the skills to plan a much better rocket for next year!
Pretty sure this is similar to the issue that Armadillo Aerosace ran into working on their tanks. Have you looked through their old posts/reached out to Carmack?
Would some type of epoxy or rtv glue work, you should read Parker oring handbook btw, a good oring seal is definitely possible with those tolerances and the Parker handbook gives you design figures that work repeatedly
Nope, you need safety factors man. No one will let you launch anything if your safety factor is 1. 3mm Aluminum 6082 at 250 dia is 1.0 safety factor. You need at least 2.0 to launch at EUROC.
A liquid engine operating at the same chamber pressure as KARMA (33 bar) would require a very similar feed pressure for the tanks (yes, for liquid engines you need 3 tanks not one). If we had more resources, we would switch to liquid. But always good to question all parts of the design.
Didn't SpaceX blow up a falcon9 by trapping oxidizer in the layers of some copv nitrogen tanks during fuel loading process? When the coov was pressurized the oxidizer was pinched and created a heat source that created a big badda boom. Good thing your unlined cf tank failed or it might have exploded the first time you filled it up with oxidizer if the inside of the cf had any layer gaps.
I'm genuinely surprised that you guys are making all these tests on such a big part....why dont you start on a ~50mm tube to get the techniques right, then bump it up to 250mm ??
Good question... Probably would be smarter. However, keep in mind that there are things about winding big that don't translate well from winding small.
@@shere_kan8329 1 - Fiber slippage. 2 - Max and min achievable angles. 3 - Effects of fiber tensioning. 4 - Effects of resin working time. 5 - surface finish quality.
There is a simple soltution to your problem 1.) don't use a pressure fed rocket engine 2.) exploit phase transition like from solid to gas ---- all two come with their own challenges again --- I guess making nitrous oxide boil would count as a novel approach --- something between 182 and 184 K and you use let's say a battery as a heat source or better something more chemical
I am not sure I follow the idea... If you want to have pressure in the combustion chamber (which is necessary for thrust), you need higher pressure feeding into that. The two options for creating that higher pressure are pressure fed (which we do here) or pump fed (which would be more complicated and expensive). Maybe you are thinking of an Autogenous pressure fed system, but this is still pressure fed and you need higher pressure than combustion in the tank to get this to work.
@@ASTRABremen I did not say that it is simpler than pressure fed. Maybe worth mentioning are some kind of closing valves so the oxidizer doesn't return to the tank. As far as I know "phase transition" counts as a novel approach. I do not have the figures in my head but at least it should allow lowering the pressure requirements as the pressure is not required for storage anymore.
@@ASTRABremen Sorry for the unclear answer last time. The idea was building up the pressure by triggering a transition from let's say liquid to gas. Imagine a steam engine with water just a bit below the boiling point. It costs little energy to create steam and now think of doing the same with very cold N2O. Okay, it's pressure fed but you can store more with less pressure and probably can use a light standard tank.
Proud to be a part of this journey! Was extremely happy after the tank worked successfully (spoiler alert)
This take me back to 2005/7. I helped build a filament winder to make some main spars for a wing. This was before arduino's and raspberry pi's. Had to make a hardwired control circuit controlling pneumatics. Working with resin and carbon fibre isn't easy. We made mandrels from aluminium, glass tubes and finally thin sheets of foam rolled into tubes. Keep on doing what you are doing - you'll learn a lot along the way.
Well done guys! The hardest part of engineering is never falling in love with a design.
Well done on the COPV, looks great! Looking forwards to seeing how it performs. Best of luck!
Interesting video thanks
Best material we have found for composites mandrels is UHMWPE or even HDPE would do. You can machine precise sizes for the inner surface and then freeze out the mandrel (it has higher thermal contraction than pvc)
Thanks for the tip. We might try that as an alternative in the future.
Also carbon fibre sleeve is good as a thinner alternative for filament winding (tho can be more expensive) we have been experimenting with producing 60bar pressure vessels using it and so far has held well to over 75bar at 1.5mm wall thickness (tho we expect that is close to the limit)
@@robinbiskupic2639 This is actually one of the options we are considering for the fairings between the CC and the tank on the next rocket. However, this doesn't work for making a type 4 tank.
I'm at 6:03 and my first thought is rather than drilling holes through the carbon fiber, secure the endcaps independently of the CF. Whether tensile supports external to the CF tube between the endcaps, or making the endcaps part of the CF tank.
I think after bolting ,dip entire bolts in resin ,could help ?
It will make layers of epoxy , and stress is evenly distributed
Hello Astra... I hope you read this,
I wish I was part of the team to warn you about the cf winding because I was pulling my hair when I saw the holes in the carbon fiber.
I want to thank you for showing how to cast a bronze nozzle because I have never seen/ hear of that before, but now the possibility for cheap regenerative cooling is within reach for model rocketry.
As for the CF chamber winding, I suggest and please let me know if you disagree that you place rods in the location of the bolts in the mandrel that you are using for winding. You should wrap normally around these 3 rows rods and the fibers will find their way around them. Do NOT drill through fibers ever again because you are committing a great composite sin. After you finish the normal winding, I recommend concentrating on the ends and pass the fibers in between the rods (future bolt holes) to reinforce that region.
After everything, you can cut or remove the rods and bolt the aluminum piece and I can guarantee that you will have absolutely near impossible to tear winding because it will be working in tension.
As for the nitrous, you have used in the end an aluminum tank and wound cf over it (correct). You should have bought a plug and play car racing nitrous tank that is aluminum and already done to operate at 900psi-1400psi easily and safely. You are not using Lox nor pressurizing to 300bar, so a Cf is not necessary and an off the shelf aluminum or even Cf nitrous bottle would have been cheaper or the same cost.
Please let me know if you disagree with any point or have any thoughts, keep up the good work.
Cheers
Thank you for your super detailed comment. One of the best parts of putting a lot of our information onto to this platform is the feedback that we get. If it can also be useful to others sometimes, that is also great!
For the chamber winding, I completely agree with you. Drilling holes in CFRP structures is not a very good move. To make it work, we had to use a 0.7mm thick Stainless Steel liner underneath the CFRP lay-up. We were toying around with your idea of winding around the holes last year, but we were struggling just to find the right methods for our design and never got around to trying it. Maybe we will take a crack at it this year now that we are not starting from 0.
For the tank, we actually wound over a steel tank. We know that our method was very mass inefficient, but we were mainly concerned with figuring our how to wind with carbon fiber. To make the tank for the rocket that will go to space will require a 250mm x 5 meter tank. This is certainly not something you can get in aluminum off the shelf. Furthermore, we need to be able to meet a 3x SF to fly our rocket in Europe. Safety standards are very high here so CFRP is not so bad when you are required to hit 180 bar. If we were flying in the US we probably would never have bothered with CFRP.
Again, thanks for the comment. I hope you continue to enjoy our channel. There is lots more interesting excitement to come this year!
This is the same problem with the Titan submersible, not enough axial strength in the carbon fibre layup. Lot's of hoop strength, but not enough axial, plus all those stress concentrations and holes aren't helping. If you build the tank with bell ends you keep the axial strength at the ends
Perhaps if the form was made out of a product that could be dissolved with a solvent like expanding foam coated with a release agent, you could make the ends of the tank and the walls in one winding. Then you're only dealing with one material interface at the valve. Winding the carbon fiber around a ribbed tube that the valve could be threaded on might work.
9:23 remember when I told you about electro-plating --- you could have used it to strengthen your ends
Y'all need to look into Cold spin mandrel forming. Looking around the shop your in I see 90% of the equipment needed in place already.
Could you solder/braze the thin sheet metal instead of welding or using a polymer on it? Need to look at electrochemical potential differences to avoid galvanic reactions.
maybe... we would have to experiment a bit. The solder would need to be compatible with Nitrous Oxide as well.
Interesting video thanks 👍
Glad you enjoyed it
Wow very good job 👏. Can't wait to see it fly .i have question Can't we use normal oxidizer like kno3 and sugar. And what was the source of the wax thanks
Well, you could use Potassium Nitrate and sugar as the propellants, but that would be a solid rocket. This comes with some challenges (especially safety and political in the EU). Basically, it is very difficult to get the authorization to use Potassium Nitrate in Germany. So, we opted to build and fly a hybrid rocket with Nitrous Oxide as the oxidizer and paraffin wax for the fuel. We also get a lot more specific impulse out of this combination, so that is nice too. The way just came from amazon - just regular candle wax. Nothing fancy! I recommend you check out some of our propulsion videos on the topic.
First, glad i found you here, i was wondering where the rocket projects are in Europe / Germany.
My only critique point is, many problems could be resolved before they happend with proper planning, i think that's a key point where you need to work on.
I am a bit sad that it is a student and not civil project, don't get me wrong, that's cool and all, but for a non student tinkerer its hard to get through the german bureaucracy to make a project like this happen. but hey, i will buy some shirts to support you.
Besides that, i wish you all the best on your endeavors and much love from Hannover.
Thanks for the support! Is is much appreciated. There are many student teams throughout Europe that are working on high powered rocketry. I would invite you to check out EuRoC where many of these groups meet and fly rockets every October in Portugal. With respect to planning, yes this is definitely a weak point in our group right now. At the start of the project, we simply lacked the experience to make good engineering decisions and that made the planning a bit of a nightmare. But, we are hoping the experience we gained will give us the skills to plan a much better rocket for next year!
Pretty sure this is similar to the issue that Armadillo Aerosace ran into working on their tanks. Have you looked through their old posts/reached out to Carmack?
What about fiberglass pipe🤔
if they're using steel reinforced carbon fiber is for a reason, I think glass fiber wouldn't withstand the forces
@@juanmontes8905 nah i dont think so
Would some type of epoxy or rtv glue work, you should read Parker oring handbook btw, a good oring seal is definitely possible with those tolerances and the Parker handbook gives you design figures that work repeatedly
Also if you go the epoxy route be careful of mold release because it might work too well and stop the epoxy from bonding
Melted metal casting is really helping astra a lot
For those diameters, 3-4 mm of aluminium tube 6082 would have done.
Nope, you need safety factors man. No one will let you launch anything if your safety factor is 1. 3mm Aluminum 6082 at 250 dia is 1.0 safety factor. You need at least 2.0 to launch at EUROC.
But... why? Why not a pressure fed liquid engine, which requires lower pressures?
A liquid engine operating at the same chamber pressure as KARMA (33 bar) would require a very similar feed pressure for the tanks (yes, for liquid engines you need 3 tanks not one). If we had more resources, we would switch to liquid. But always good to question all parts of the design.
Didn't SpaceX blow up a falcon9 by trapping oxidizer in the layers of some copv nitrogen tanks during fuel loading process? When the coov was pressurized the oxidizer was pinched and created a heat source that created a big badda boom. Good thing your unlined cf tank failed or it might have exploded the first time you filled it up with oxidizer if the inside of the cf had any layer gaps.
I'm genuinely surprised that you guys are making all these tests on such a big part....why dont you start on a ~50mm tube to get the techniques right, then bump it up to 250mm ??
Good question... Probably would be smarter. However, keep in mind that there are things about winding big that don't translate well from winding small.
@@ASTRABremen such as ?
@@shere_kan8329 1 - Fiber slippage. 2 - Max and min achievable angles. 3 - Effects of fiber tensioning. 4 - Effects of resin working time. 5 - surface finish quality.
There is a simple soltution to your problem 1.) don't use a pressure fed rocket engine 2.) exploit phase transition like from solid to gas ---- all two come with their own challenges again --- I guess making nitrous oxide boil would count as a novel approach --- something between 182 and 184 K and you use let's say a battery as a heat source or better something more chemical
I am not sure I follow the idea... If you want to have pressure in the combustion chamber (which is necessary for thrust), you need higher pressure feeding into that. The two options for creating that higher pressure are pressure fed (which we do here) or pump fed (which would be more complicated and expensive). Maybe you are thinking of an Autogenous pressure fed system, but this is still pressure fed and you need higher pressure than combustion in the tank to get this to work.
@@ASTRABremen I did not say that it is simpler than pressure fed. Maybe worth mentioning are some kind of closing valves so the oxidizer doesn't return to the tank. As far as I know "phase transition" counts as a novel approach. I do not have the figures in my head but at least it should allow lowering the pressure requirements as the pressure is not required for storage anymore.
@@ASTRABremen Sorry for the unclear answer last time. The idea was building up the pressure by triggering a transition from let's say liquid to gas. Imagine a steam engine with water just a bit below the boiling point. It costs little energy to create steam and now think of doing the same with very cold N2O. Okay, it's pressure fed but you can store more with less pressure and probably can use a light standard tank.
people why?! so much waste of everything...