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 <mailto: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 <mailto:kenbiba@xxxxxx> >
To: arocket <arocket@xxxxxxxxxxxxx <mailto: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
<mailto: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
<mailto: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
<mailto: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
<mailto: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
<mailto: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
<mailto: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
