
NASA Moves Closer to Building a 3-D Printed Rocket Engine - espeed
http://www.nasa.gov/centers/marshall/news/news/releases/2015/piece-by-piece-nasa-team-moves-closer-to-building-a-3-d-printed-rocket-engine.html
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Animats
This makes sense for rocket engines, which are mostly rigid objects with a lot
of internal plumbing. 3D printing is good at objects with complex internal
voids. The rigid parts can be made up as one piece, rather than welding or
bolting a large number of parts together. The surface finish of the plumbing
usually isn't critical, so there's no need for finish machining. It's the
right tool for the job.

Here's Space-X's 3D printed engine.[1] Watch the video of the test firing. The
engine is being throttled up and down, at higher and higher rates. Those guys
like aggressive control strategies, as seen with the Falcon booster landing,
and an engine which can keep up helps.

[1] [http://www.spaceflightinsider.com/organizations/space-
explor...](http://www.spaceflightinsider.com/organizations/space-exploration-
technologies/spacexs-superdraco-engine/)

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afshin
SpaceX has been 3-D printing injectors with a titanium printer for a few
years. I wonder how much information is shared.

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krasin
SpaceX also prints its SuperDraco engines ([1]) using Inconel superalloy ([2])
powder, which is even harder to process with a mill than titanium.

1\.
[https://en.wikipedia.org/wiki/SuperDraco#Manufacturing](https://en.wikipedia.org/wiki/SuperDraco#Manufacturing)

2\.
[https://en.wikipedia.org/wiki/Inconel](https://en.wikipedia.org/wiki/Inconel)

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burger_moon
I hadn't heard that iconel was worse to machine than titanium, but machining
titanium was a much bigger pain in the ass. You have to be very careful about
your metal chips when machining titanium because they can ignite.

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krasin
According to the machinability ratings [1], Inconel 700 is rated at 0.09 (less
is harder) and Inconel 702 at 0.11, while most of the Titanium alloys are
above 0.15. There's a single Titanium alloy family (MST) in the table that is
just as hard to machine as Inconel 700.

So, you're technically correct: generally, they are on the same scale. And
your argument about ignitability is certainly true.

1\. [http://www.quakerchem.com/wp-
content/uploads/pdf/skill_build...](http://www.quakerchem.com/wp-
content/uploads/pdf/skill_builders/no10_machinability_ratings.pdf)

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bcook
I really wish that we could replace the phrase "3-D printing" with "additive
manufacturing" when referring to metals and/or serious, low-tolerance
manufacturing.

"3-D printing" should be used when referring to hobbyists making semi-useless,
plastic trinkets. No disrespect to plastics or hobbyists, it's just that the
phrase lost some dignity when it became a over-generalizing buzzword.

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jacquesm
There is a whole range of machines that can be classed as 3D printers, from a
simple reprap like setup all the way to SLS and DMP printers. Yes, they're all
'additive', but additive manufacturing is a concept that is a lot wider than
3D printing. For instance metal vapor deposition is also additive
manufacturing and definitely not 3D printing.

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jeffwass
One nitpick - metal vapour deposition, when done in-situ through a moveable
shadow mask, certainly is 3D printing. One can dynamically "draw" out
structures having controlled variable-height profiles inside the vacuum
chamber during the evaporation process by altering the position (and thus
speed) of the moving shadow mask.

This method is quite different from the "ordinary" metallic vapour deposition
process you're referring to that uses a simple fixed-position mask, usually
photoresist that is baked right onto the silicon wafer.

Eg, here is my research paper from 8 yrs ago demonstrating nanoscale-level
dynamic stencil deposition using a nanopore in a suspended silicon nitride
membrane shadow mask. We controlled the mask's position using a piezo actuator
inside the deposition chamber during the evaporation process to 3D print
nanowires and other nanostructures with programmable height profiles. Eg, we
created nanoramps, and nanowires with one or more "valleys" to simulate
quantum wells or metallic grains.
[http://scitation.aip.org/content/aip/journal/rsi/79/7/10.106...](http://scitation.aip.org/content/aip/journal/rsi/79/7/10.1063/1.2960573)
Arxiv link :
[http://arxiv.org/pdf/0802.1848.pdf](http://arxiv.org/pdf/0802.1848.pdf)

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jacquesm
That's very neat, and yes, you're right, when doing it with a movable shadow
mask it is 3D printing. Totally missed that option when I gave the examples.

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nether
Rocket Lab is 3D printing most of their engines:
[http://fortune.com/2015/04/17/rocket-lab-satellites-
space/](http://fortune.com/2015/04/17/rocket-lab-satellites-space/)

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sandworm101
So which 'parts' are actually printed? I cannot believe that the turbopump
blades could possibly be printed additively as they would lack proper crystal
structure.

Piping can be printed, but given the stresses at attachment points, I cannot
see that printing pipes would save many man-hours.

The turbopump casings could certainly be printed, but not in "one piece".
Someone needs them open to insert the bearings and blades. So two pieces at
best ... exactly as if they had been milled rather than built additively.

So what's left? The combustion chamber and bell might do well. They have some
internal voids/plumbing that probably suits such printing. But the stresses?

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gjmulhol
One cool part about this is that once they prove that current engine designs
can be replicated using additive manufacturing, then totally new engine
designs, different from anything possible with traditional manufacturing
techniques, can be developed. It would likely mean higher thrust per unit fuel
and generally more efficient systems.

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sandworm101
Higher thrust per unit fuel isn't limited by manufacturing technique. Per-unit
cost isn't really a limiting factor for rocket engine development. These
things cost tens of millions of dollars and they push things worth perhaps a
billion. Governments have been throwing billions, defence billions, at the
technology for over a half-century.

The physics of ISP is well-understood and current engines are near what is
physically possible, regardless of who/what builds the engines. 3d printing
could certainly make engines more affordable and/or lighter, but it isn't
going to allow an engine to be any more fuel efficient.

Anyone who builds an engine with significantly increased ISP using standard
fuels (ie without going nuclear) will probably win a few nobel prizes. 3d
printing is about improved manufacturing, not new physics.

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maaku
Hasn't SpaceX been doing this for a few years?

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nickff
Yes, they have.[1]

[1] [http://www.spacex.com/press/2014/05/27/spacex-completes-
qual...](http://www.spacex.com/press/2014/05/27/spacex-completes-
qualification-testing-superdraco-thruster)

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paulsutter
This is bigger news for asteroid mining than it is for Mars (why return the
ingredients to earth when you can 3D print end products at the source). But
kudos to Elon for getting the world talking about Mars again.

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serge2k
Kudos to our holy savior.

Can we rename Christmas to Christmusk and change the date to the 21st?

