Houkago, Bokura wa Uchuu ni Madou - Ch. 12

[nyarlathotep885]

they're not actually 3d printing the fuel are they? they're 3d printing a mold to cast the fuel in?

 

[TaqPCR]

Not study in STEM, just a lowly nerd/geek, but I assume solid fuel?



I reckon its about surface area? Koch Snowflake would give you tons of that. Whether or not its the best shape for that is even wayyyy beyond me as someone who isn't not in STEM field but we probably can chalk it up to they have researched it already that this is the optimal setup for them? Best girl mentioned she wanted to increase thrust last chapter too. But the shape wasn't the reason their engine blew up. That issue was addressed and this shape is new implementation. Maybe it'll be the next flaw in their design?

Frankly this is waaaaaay too large as a starting channel for a rocket engine, they're giving up like half of their fuel. And having it be that large with the initial fractal shape is gonna mean it burns super quickly right at the start.

Even if you want super high initial thrust that then goes way down there's better options that don't sacrifice as much fuel volume, like having a * sign where each arm branches into a y shape gives you huge starting surface area but doesn't sacrifice as much fuel volume.

But they're also making a hybrid engine so they can tweak things by adjusting the oxidizer flow rate so...

 

[Takuma_Aki]

they're not actually 3d printing the fuel are they? they're 3d printing a mold to cast the fuel in?

From how I read it, yes, they're printing the fuel. ABS plastic can be used as rocket fuel.

Ref.

 

[Manquess]

About the shape of the fuel, i'm not too deep into this but i would assume they want high initial thrust to not have to tweak the rocket itself as much depending on the wind conditions at land, but looking at their altitude goal of 10km, i don't see the point tbh.

I would like to see how much air resistance would harm the flight over other fuel shapes, it is probably fine with an hybrid engine since they can regulate the flow rate, there's not much more to say without doing homemade rockets and researching these things yourself though...

 

[MagicHour]

I have a Creality CR-10 v2 and I feel her pain. That finicky bitch.

Ender 3 for me. Endless tinkering just to get it to successfully print. Replaced it with Flashforge AD5M and haven't looked back.

 

[Threacon]

What do you mean 3D prient FUEL?

search integza on youtube

but i think he uses a different type of 3d printer

 

[TaqPCR]

What do you mean 3D prient FUEL?

It's a hybrid rocket with solid fuel and liquid oxidizer. So for the fuel all you need is something that burns unlike normal solid fuel that needs to mix both the fuel and oxidizer together.

In this case the fuel is ABS plastic that you then flow your oxidizer through (O2, H2O2, N2O, N2O4, etc.). You can mix things like graphite or powdered aluminum into the ABS to increase performance but it's not necessary.

One of the advantages is actually the ability to easily print novel geometries (though I have some concerns about their specific one.

 

[asdfgh1111]

Ender 3 for me. Endless tinkering just to get it to successfully print. Replaced it with Flashforge AD5M and haven't looked back.

The first printer I had was an Ender 3 pro, that I managed to get for $99. It did pretty well once you got everything dialed in but doing all that as always a pain in the ass. The CR-10 is pretty much the same but bigger. I needed the room but I don't i would have gone for it if I hadn't gotten such a good deal on it (only $180). Though, I kept forgetting with Creality, what you save in money you pay in time. I wish I could afford something nicer.

 

[hentako]

Worth getting into trouble for

 

[GOAT_of.the_Uchiha]

Its a thing that happens when you swipe left on Mangadex. It happens on phone version, I dunno if you can trigger it on computer.

Thanks for the info. However, I was, in fact, using this site on a laptop when I got that jumpscare.

 

[Bumpf]

Not study in STEM, just a lowly nerd/geek, but I assume solid fuel?



I reckon its about surface area? Koch Snowflake would give you tons of that. Whether or not its the best shape for that is even wayyyy beyond me as someone who isn't not in STEM field but we probably can chalk it up to they have researched it already that this is the optimal setup for them? Best girl mentioned she wanted to increase thrust last chapter too. But the shape wasn't the reason their engine blew up. That issue was addressed and this shape is new implementation. Maybe it'll be the next flaw in their design?

@Taq
I couldn't find anything on the Koch snowflake specifically but I've found a "dendrite" shape that is in some diagrams. Here are some links of stuff I have found to be related:

https://space.stackexchange.com/que...n-thrust-curves-of-different-grain-geometries

https://www.researchgate.net/public...nback_Simulation_Tool_for_Solid_Rocket_Motors

And looking into it, this REALLY reminds me of https://en.m.wikipedia.org/wiki/Curve-shortening_flow !!! A relative of curve-shortening flow (Ricci flow) was actually used by Grigori Perelman to prove the Poincare Conjecture a hundred years after it was originally posed

 

[Ramenbol]

that last panel 💀

 

[Ramenbol]

@Taq
I couldn't find anything on the Koch snowflake specifically but I've found a "dendrite" shape that is in some diagrams. Here are some links of stuff I have found to be related:

https://space.stackexchange.com/que...n-thrust-curves-of-different-grain-geometries

https://www.researchgate.net/public...nback_Simulation_Tool_for_Solid_Rocket_Motors

And looking into it, this REALLY reminds me of https://en.m.wikipedia.org/wiki/Curve-shortening_flow !!! A relative of curve-shortening flow (Ricci flow) was actually used by Grigori Perelman to prove the Poincare Conjecture a hundred years after it was originally posed

I CAN SEE HIM I'M NOT SCRIZOPHRENIC AM I?

 

[NicholasKai]

It's cool that they're 3d printing rocket fuel but just so anyone knows you really shouldn't be sitting that close to it while it's going. 3D printing, at the end of the day, involves melting plastic and creating fumes that would be unwise to breathe. It won't kill you instantly, but it's just not a great idea. ABS is actually especially notorious for these fumes and both for the sake of your health and optimal print quality it should be done in an enclosed printer in a well-ventilated area. Stay safe kids!

 

[hdr22]

As people guessed in earlier chapters they are indeed doing the Utah State strat of printing ABS fuel grains. They should probably get an enclosure for their printer though. You can do far more interesting things with printed fuel grains.

 

[Bumpf]

I CAN SEE HIM I'M NOT SCRIZOPHRENIC AM I?