Hey guys,
Has anyone considered using something like the SPA protocols ?
( Satellite Plugnplay Architecture - AIAA S-133.
Sometimes confused with Spacewire PnP Arch which seems to be the
European version)
It's an open standard, of course the current 2013 paper is about $1k.
The 2011 (201X) Draft Copies are available for free.
Basically, each component (IMU, Radio, RCS, etc) has a small processor
on board that 'knows itself' with its capabilities and calibrations.
While many use ARMs and stuff, there were some examples of AVRs.
The networking architectures include I2C, and seem to be extensible.
I'm not sure if I like the DB-15 and DB-25 connector standard, but
they also seem to be changeable.
That's about the total of my understanding, but the idea of slapping
stuff together and having the code work out the details seems nice.
Comments ?
-Gar.
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Subject: [AR] Re: Flight Computer
From: Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
Date: Fri, 25 Dec 2015 00:11:34 -0600
Ken,
Interesting data - that's the kind of information I was looking for.
Thanks for sharing it.
-Bob
On 12/24/2015 06:08 PM, KEN BIBA wrote:
A bit of experimental data.
The 17 years of the ARLISS (A Rocket Launch for International Student
Satellites - www.arliss.org <http://www.arliss.org>) program has some
interesting data to contribute to this discussion. This is the first
and oldest CanSat competition - begun by Professor Bob Twiggs (CubeSat
co-inventor) and continued by AeroPac in partnership with Unisec
Global (unisec-global.org <http://unisec-global.org>). Each year we
fly about 50 flights of 15 kg airframes with 1 kg university student
payloads to about 3k meters on M motors ⦠where the payloads are
deployed at apogee for autonomous return ⦠each payload is an
autonomous robot. Most land to crawl home across the Black Rock
playa floor, but some fly in various ways. Each payload has a
rather complex DIY electronics payload as well as the flight avionics
⦠subject to boost acceleration of up to 8 Gs plus deployment shock
(from either black powder or CO2). We now have about 800 flights on
M motors with this flight profile during the program - on a fleet of
very similar airframes, on essentially the same motor - the Aerotech
M1419.
In 2013, we decided to investigate more deeply about the flight
dynamics of our student payloads and designed a custom flight recorder
with 3x accelerometer + 3x gyro with a recording rate of ~1.3 kHz to
examine these dynamics. A team of our members, led by Bob Feretich,
designed and implemented the custom datalogger and post processing
software (http://www.rafresearch.com/rocketdatalogger/index.html) to
implement this data collection and analysis. A portion of the
database of these flights from 2014 can be found here
(http://www.rafresearch.com/arlissdatalogger/flightdata/ARLISS2014/index.xml)
including spectral analysis of the experienced by the payloads during
boost and deployment.
One of the surprising results of the analysis is that while there are
some very large magnitude shocks (up to 50g! - particularly from black
powder deployment) - there is little correlation with payload
electronics failure. Remember these are student payloads ⦠so build
quality is highly ⦠variable. We speculate that while the absolute
magnitude of the shock can be high, the duration is very short ⦠so
the total energy in the shock is modest.
We think this will correlate well to the shock profile for ARLISS
Extreme suborbital flights as well. We will fly one of these
recorders this coming season to confirm - but the motors and
deployment methods are not dissimilar.
A paper describing an overview of this recorder can be found here
(https://www.dropbox.com/s/1kpkt3dg6038pbx/ARLISS%20Data%20Logger%20Project%20Part1.pdf?dl=0).
Bob Feretich has these recorders for sale as well.
Here is an overview of the ARLISS program.
https://www.dropbox.com/s/5f6sl7dsr5lrdl8/Sport%20Rocketry%20ARLISS%201.2014.pdf?dl=0
A copy of Dnepr user manual is enclosed ⦠this has some standards for
testing payloads on a big solid to LEO - note pages 54-58 for specs on
typical payload acceleration and deployment shock..
https://www.dropbox.com/s/ncnk03oly4eodxu/Dnepr_User_Guide.pdf?dl=0.
To my eye, the boost acceleration magnitude and the deployment shocks
are not dissimilar between Dnepr and ARLISS and perhaps might be
extrapolated to other solid fueled systems.
We see very few flight avionics failures (three out of 800 flights -
and we ascribe those to pilot error) and most of the student failures
seem to be from connector failure on landing shock.
Ken
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