Playing catchup here... I can't prove it, but my suspicion is that
amateurs could get most of the benefit here at a fraction of the cost.
If your electronics can't stand being bolted in the bed of a pickup
truck for three fast miles down a dirt road, and/or operated in a black
metal box alternately left in the desert sun and under the outlet of an
AC, then chances are good it'll have reliability problems under field
conditions or in flight.
Wholly scientific, no. But then adding some sort of decent-bandwidth
vibration/shock sensor - a small weight suspended on three axes with
strain gauges on each axis? - is there such a thing off-the-shelf? -
plus a thermocouple would let you make it much more so. Run the same
instruments on a flight or two so you have an idea what the actual
requirement is, then go from there.
On 12/21/2015 9:37 PM, Pierce Nichols wrote:
If you want to really torment your electronics, vibe + fast thermal
cycle will rapidly find every mistake you made... that costs a bit more
than $2500/day, tho.
-p
On Mon, Dec 21, 2015 at 8:11 PM, Jonathan Goff <jongoff@xxxxxxxxx
<mailto:jongoff@xxxxxxxxx>> wrote:
Ben,
Random vibe is probably something matters more when you're dealing
with larger rockets and more aggressive mass ratios. It's also a
good way to check for workmanship quality.
As the cost of failure goes up, the relative cost of some
thoughtfully applied environmental testing starts seeming more and
more reasonable. We just did some random vibe for a project (just a
survey not a Qual test), and discovered a lot of useful info.
Aerospace vibe testing facilities for modest sized stuff have run
around $2500 per day, with non-aerospace facilities down closer to
$1500. I wouldn't write off its utility when used judiciously.
Jon
On Dec 21, 2015 8:27 PM, "Ben Brockert" <wikkit@xxxxxxxxx
<mailto:wikkit@xxxxxxxxx>> wrote:
Professional shaker tables are still just big speaker cores. I
visited the one they use to test hardware in the mobile launch
platforms at KSC, and it's 'just' a 480kW amp and a fat coil of
wire. You can build a surprisingly realistic approximation with
a subwoofer, amplifier, and sine wave generator.
If NASA was cool they'd build a speaker cone for their rig and
recreate that scene from Back to the Future.
Things that flew without going through random vibe testing: all
of Armadillo and Masten's rockets. Though perhaps Armadillo
could have found that their GPS was sensitive to vibration if it
had been tested before flight.
On Monday, December 21, 2015, Robert Watzlavick
<rocket@xxxxxxxxxxxxxx <mailto:rocket@xxxxxxxxxxxxxx>> wrote:
That's weird - I would think any reasonable PCB would stand
up to vibration the same as any other. However, I have a
BBB and just looking at it, I would suspect the power and/or
USB connections as potential failure points. In a previous
life, we had to delete the planned vibration specs for a
product the USB connector failed vibration tests. Good to
know though - thanks for the tip.
I was trying to figure out the best way to check out my
flight computer setup for vibration. I don't have access to
a shaker table so I thought I would strap it to my truck
bumper and drive it around for a while. A few miles over
our pothole-laden roads should be a pretty good test, at
least for random excitation.
-Bob
On 12/21/2015 04:25 PM, doug knight wrote:
Not robust. Mount was good but jostling around the device
had it run intermittently. Worked well on benchtop but not
repeatable at launch site. And did not work at all in
launches. Scraped and went to arduino and problems
disappeared. This was a couple years ago also. Of course
Arduinos have other limitations so
Doug Knight.
On Dec 21, 2015 3:25 PM, "Robert Watzlavick"
<rocket@xxxxxxxxxxxxxx> wrote:
What kind of problems did you run into? I considered
the BeagleBone Black with FreeRTOS but ended up going
with the Netburner MOD54415.
Monroe - I glanced over the OSAL stuff a while back
and it looked very sophisticated but I don't think
it's a turnkey system. I think it's more a set of
middleware building blocks (messaging stack, file
system, etc.). If you have the time to invest in it,
it would be interesting to see how useful it turns out
to be.
-Bob
On 12/21/2015 01:13 PM, doug knight wrote:
Monroe
I did not haveagood experience with beaglebones
and hobby high power rockets. They did not seem
very robustly all. Of course YMMV.
Doug Knight