Troy:
Yup. Those numbers just don't seem to match reality. We have used both carbon
composite fins and aluminum. If those temperatures were within a factor of 10,
we should have seen some effect on the composite leading edges.
We have not.
Over a number of flights we have had one composite failure in which whole fin
cans delaminated around maxQ - barely trans Mach but low in atmosphere. We
think not a heating effect but rather surface prep problems in the lamination
process.
K
Ken Biba
Novarum, Inc.
415-577-5496
On Apr 5, 2017, at 6:44 PM, Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx> wrote:
You might be able to BOE the leading surfaces maybe(?) by doing a temperature
conversion of the RMS velocity of the air molecules to gather a ball park
number?
vrms = sqrt(3RT/Mm)
R = molar gas constant = 8.3145
T = Ambient Temperate of the air = 298 Kelvin
Mm = molar mass of the air in kg per mole = ~29 for air
So air molecule vrms = sqrt((3 x 8.3145 x 298) / 29) = ~506 m/s (ie rocket in
ambient temperature in a stationary position)
Rearranging for T at… dunno say Mach 2 which let’s say is 670 m/s so can we
assume the vrms hitting the leading surfaces would be approx. 506+670 = 1176
m/s ?
So now rearranging:
T = (vrms^2 x Mm) / (R x 3) =
(1176^2 x 29) / (8.3145 x 3) = ~1608 deg K
Converting to say deg C = 1608 -273 = 1335 deg C
Which seems a bit high? Dunno?
As has been mentioned, the exposure is only temporary and heat*ing* will be
proportional to air density which is obviously reduced as you increase in
altitude.
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Ken Biba
Sent: Thursday, 6 April 2017 10:34 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: AR Nose Heating (was:. 3D-printed RL-10)
We've tried to do some CFD calculations to get a better idea of heating
effects in the sounding rocket performance domain. A challenging project but
if there is a university team with access to good (and expensive!) tools -
love to collaborate.
As Chuck says, our experience validates other amateur experience. The
heating effects are more modest than rumor suggests. More data of measured
heating effects would be a goodness.
Of course, there ARE ways to make the heating effects worse. Wrong nosecone
shape. Too much attempted acceleration low in atmosphere that directs motor
energy into heating.
K
Ken Biba
Novarum, Inc.
415-577-5496
On Apr 5, 2017, at 5:14 PM, Redacted sender "crogers168" for DMARC
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
You can calculate the radiation equilibrium temperature on the nose cone, and
get a very high surface temperature. But this is analogous to the skin
temperature of an SR-71 in cruise.
Analogy for a sounding rocket type heat exposure like this, is a 750 deg F to
1,000 deg F oven, you stick the rocket in for 20 seconds and then pull it
out. Much lower temperature. Unfortunately much more detailed analysis to
get the time dependent thermal effects on the surface temperature.
As Ken mentioned, many high power rockets have flown to Mach 3, and a little
over, with metal nose tips and composite nose cones.
Example below is the Derek Deville Qu8k Q motor rocket, which used a
fiberglass nose cone with aluminum end plates, and a stainless steel nose
tip. Replacing the fiberglass with aluminum could probably easily stretch
this configuration to Mach 4.
<Qu8k.jpg>
http://ddeville.com/derek/Qu8k.html
Main advantage of Inconel versus a high temperature steel is weight. Note
from the Qu8k rocket that the steel nose tip is only part of the nose cone,
weight savings from Inconel will be minimal. And the extra weight from using
high temperature steel is literally at the best point on the rocket, the nose
tip, moving the CG forward.
Chuck Rogers
-----Original Message-----
From: KEN BIBA <kenbiba@xxxxxx>
To: arocket <arocket@xxxxxxxxxxxxx>
Sent: Wed, Apr 5, 2017 4:43 pm
Subject: [AR] Re: AR Nose Heating (was:. 3D-printed RL-10)
Our experience in flying to the 100k’+ region with peak speeds in the Mach
2.5-3.5 domain suggests heating highly overrated. We are flying largely
composite airframes with modest grade epoxy with composite (fiberglass)
nosecones with an aluminum tip - VK shape.
We have seen no signs of nosecone heating … and the only heat effects on the
airframe we have seen has been on heavy paint on the sustainer body about 3’
back from the nosecone tip .. where it appears the shockwave returns to the
body. It got a bit smeared. Hope to actually, finally fly an instrumented
nosecone this summer to measure nosecone heating.
K
On Apr 5, 2017, at 4:33 PM, Team Icarus SDSU <rocketteamicarus@xxxxxxxxx>
wrote:
This question is also of interest to our projects.
It's a couple years from launch, but Icarus 3 is likely to remain in the
M=3.0-4.0 range for the first 100,000' of its flight; significant heating is
expected. We need to perform more in-depth analysis, but the current plan is
to build the dart section from lathe-turned inconel.
Alex Lewis
On Tue, Apr 4, 2017 at 6:22 PM, 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
