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> 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>
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