Dave, thanks for the feedback. My comments were fairly speculative but glad to
see someone else is thinking in the same general direction. While I'm by no
means an expert on GrCop-84 I have heard it is being tested in a research
environment on Arcam (EBM) machines, which sounds similar to SLM and was mainly
what I based my comments on. I've been looking at it too as an alternative to
Inconel. I don't think it's quite ready for general use yet but my suspicion is
within the next year or so it will be an additional material option.
One issue with EBM processes (and I'd assume SLM as well) is they are not as
good at internal geometry. The article mentioned the part takes under a month
to print (that is an excessively long time) but I'm wondering if they slow the
layering process down a bit to better deal with the thermal issues with melted
powder.
On Wed, Apr 5, 2017 at 2:42 AM, Dave Klingler<davek@xxxxxxxxxxxxxxxx> wrote:
Reading the article again, it does specifically state that they are
substituting “copper alloy” in a “new chamber design”, so I should have reread
it and answered my own question. :)
That’s actually pretty cool. The new RL-10, when it arrives, might have
significantly higher chamber pressures.
I agree that the most likely copper alloy is Glenn Research’s GrCop-84, and I’d
conjecture that they may be using selective laser melting to consolidate the
raw GRCop-84 powder, rather than creating a solid and then re-powdering it to
create feedstock for the SLM machine. If I’m correct then that’s rather
elegant.
A while back I made a half-hearted effort to find GrCop-84 for an engine
project I’ve been fiddling with. Back then I was unable to find any and
decided to content myself for now with more mundane materials. I feared that
the price, when or if I tracked GrCop-84 down, might be something well beyond
what I could afford. But GrCop-84 might be a whole lot cheaper as a powder
than as a billet. Using pre-consolidated powder as SLM stock might actually
cut the cost quite a bit, again, if that’s what they’re doing, which might
bring it down into amateur territory.
Dave Klingler
On Apr 4, 2017, at 7:43 PM, Graham Sortino (Redacted sender "gnsortino" for
DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
I was looking at this article today as well and had a few observations...
According to the Rocketdyne website the RL10C-1 is a pretty large ~25k lbf
engine. It has a length of 86" and a nozzle width of 57". It is an upper stage
engine but judging by the picture I'm guessing the version they tested more of
a sea level nozzle. Even if the engine doesn't have a full sized nozzle that is
pretty impressive that they printed such a large engine.
They mention using copper alloys and select laster melting (SLM). Note- this
is different then DMLS. I'm not as familiar with SLM but I did a quick google
and it lists a company called SLM Solutions. It sounds like SLM is similar to
the EBM process that Arcam uses. Also, I'm just guessing that the alloy they
are printing is in GrCop-84, which is sort of like a high strength / high
thermal conductivity copper alloy.
On Tuesday, April 4, 2017, 5:23:39 PM EDT, William Claybaugh
<wclaybaugh2@xxxxxxxxx> wrote:Do (AR) nose tips see the kind of heating that
would require inconel or the like?
I've wondered if USC/RPL's titanium nose tips are justified for a Mach 5
mission w/ a very short heat pulse....
To be clear, I have not done my own analysis, I'm asking two questions.
Bill
On Tue, Apr 4, 2017 at 7:01 PM Ben Brockert <wikkit@xxxxxxxxx> wrote:
I visited Atlantic Precision a couple years ago, one of the few shops in the US
with multiple EOS DMLS machines, and they were actively printing parts for the
RL-10 even back then. Printing the chamber is big and flashy, but there's a lot
of utility in cranking out highly detailed inco or haynes parts.
For any part with moderate complexity of the nickel alloys it's now cheaper to
print and lightly post-machine than to machine from solid material, even at
small production quantities.
That is of relevance to AR because a one-off printed and sanded nickel alloy
nose tip for a higher performance hobby rocket should quite affordable,
especially if you shop around and make it clear that you're not in a rush for
the part.
On Tuesday, April 4, 2017, Dave Klingler <davek@xxxxxxxxxxxxxxxx> wrote:
Ehhhh…one can always ask. Sometimes people like to talk about where they’re
headed. :)
Dave
On Apr 4, 2017, at 1:17 PM, William Claybaugh <wclaybaugh2@xxxxxxxxx> wrote:
Dave:
Anyone privy to such information is likely subject to a non-disclosure
agreement....
Bill
On Tue, Apr 4, 2017 at 12:24 PM Dave Klingler <davek@xxxxxxxxxxxxxxxx> wrote:
I just saw an article over at parabolicarc about AJR's first 3d-printed thrust
chamber firing. I’m trying to decide whether, from what I’ve read, they’re
substituting copper for stainless in a few spots.
I think design changes are probably unlikely this early, but at the very least
the new manufacturing process opens up the way for different materials and more
elaborate cooling passages that wouldn’t be possible using the old tube
benders. Is anyone on this list privy to what sort of plans AJR has for higher
chamber pressures or other improvements to the RL-10? What’s the schedule for
doing complete engine certification?
Dave Klingler
