

3D printed rocket – operational tests - iamwil
http://rocketmoonlighting.blogspot.com/2012_03_01_archive.html

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ChuckMcM
That was interesting. I feel like I've seen an X rated movie that was edited
and pixellated to make it PG-13. Lots of tantalizing bits, not a lot of
narrative, and details hard to ferret out.

The basic notion that you could use metal sintering to create a rocket
combustion chamber that included the cooling jacket is pretty neat. That lets
you run reasonably energetic fuels without having exotic materials (tungsten
for example). I can also see why going too far down that path might lead to
untoward interest by third parties.

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clayrichardson
Suppose someone wanted to take this hobby farther down the path, and start a
rocket company similar to SpaceX. How would one avoid negative attention in
doing so?

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ChuckMcM
Well there is a pretty large amateur rocketry group in the Bay Area [1] that
goes out to the Blackrock desert and launches rockets. Generally such clubs
are great resources for understanding the regulations and if pursuing things
professionally the requisite licensing. I was related a story about how the
Bureau of Alcohol Tobacco and Firearms (BATF) stopped one team from launching
because they had used a solar tracker attached to steerable fins to keep the
rocket on track, the story went that once you had it tracking a heat signature
with steerable fins it went from being a model rocket to a munition. I can't
vouch for accuracy of the story but the teller was someone I respect and is
quite an enthusiast so I give it a good chance of being basically true.

So generally one considers the various elements of creating a rocket propelled
munition and if you got too close to describing how someone could build one, I
would not be surprised in the least if that person was approached by the BATF
or the FBI asking you to limit what you publish. Or approached by people
seeking to build such a device from 'scratch.'

Even doing something as simple as hobby robotics I've had folks email me out
of the blue on how to create a circuit that would let you activate a switch
remotely but was hard to jam. It can conceivably be used for robotics sure, it
can also be used for ill. I generally point people to Horowitz and Hill's Art
of Electronics and tell them its all in there (which it is, but you have learn
it to use it) but perhaps out of a surplus of caution I don't design such
things for folks.

[1] [http://science.kqed.org/quest/video/amateur-rocketeers-
reach...](http://science.kqed.org/quest/video/amateur-rocketeers-reach-for-
the-stars/)

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RobertHoudin
Looks interesting, but could somebody please explain this like I'm 5?

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ChuckMcM
Well it is rocket science. I can strongly recommend any version of "Rocket
Propulsion Elements: And Introduction to the Engineering of Rockets" Knowing
calculus when you read it is helpful but not essential.

That said, rocket engine design is a tradeoff between how much energy you
generate in the combustion chamber and your ability to direct the resulting
hot gas in the direction you want it to go. Highly temperature resistant
materials like ceramics can take a lot of heat, but they don't have a lot of
tensile strength, things like metals which are very tough generally become
weaker the hotter they get. Combined with the fact that combustion chamber
shape determines how the gases will burn, and you find yourself trying to
design something that is very durable, can withstand significant pressure, and
can take a lot of heat. Model rocket engines basically consume themselves as
they burn being their own combustion chamber, but liquid or gaseous fueled
rockets have to deal with the heat. The kicker is that if you don't get enough
energy in the combustion chamber, you can't generate enough thrust to
counteract the force of gravity so you can't even get off the ground.

The Space Shuttle's engines use tubing that runs through the engine 'bells'
that cryogenic liquid runs through prior to being burned as fuel. This keeps
them cool enough to contain the engine burn without melting or losing
structural stability. That isn't something someone can build on a 'whim'.

This guy made something similar using a 3D printing process on metals.
Assuming that the metal's tensile strength is sufficient post printing, this
sidesteps a huge barrier to amateurs making liquid/gaseous fueled engines.

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anovikov
Will be curious to see the whole stage printed :) Of course electronics,
wiring, probably ignitors, electric actuators and some other stuff can't be
printed, but it removes a lot of pain from the process.

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kordless
What part of the rocket is printed? I see a lot of metal there.

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a1k0n
This post here seems to be more informative:
[http://rocketmoonlighting.blogspot.com/2011/03/what-its-
all-...](http://rocketmoonlighting.blogspot.com/2011/03/what-its-all-
about.html)

To save you a trip to Wikipedia, DMLS is Direct metal laser sintering -- 3D
printing with metal.

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fosk
This an example of such a printer:
<http://production3dprinters.com/slm/direct-metal-slm>

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jlgreco
Now we just need a printed turbopump.

