Re: [Paparazzi-devel] question about paparazzi on sounding rocket

[Bernard Davison]

Yep standard civilian GPSs have been flown. They lose position of course at 
launch but do acquire solution after the main parachute opens.

Also the MEMS accelerometers have been flown and data logged.

The major problem we've always faced is knowing what went wrong when things 
don't work and the thing is buried 5m underground and the rocket has turned 
itself into metal confetti. 
We've worked out what we believe  Will be a survivable data storage module. 
Hopefully to be tested in the next year or so.

At the moment were breaking the Lisa/L board up into smaller components and 
designing them to be rugged. I.e. positive locking connectors isolation on some 
switches and comms. Etc.
We're also breaking the board into discrete task based "nodes" that can 
communicate via redundant CAN bus connectors. So in the future it would be 
possible to have a failure tolerant system. I.e. if you have a failure of a 
transceiver node, IMU node, flight computer node, CAN bus. Then it could use 
another node on the network.
Of course that would need the appropriate software to be written for that kind 
of control.

Cheers,
Bernie. 

Sent from my iPad mini.

On 14/02/2012, at 10:46 PM, Chris Gough <address@hidden> wrote:

> Wow Bernard.
> 
> Do you use civilian GPSs in those rockets? MEMS IMUs?
> 
> Chris Gough
> 
> On Tue, Feb 14, 2012 at 10:34 PM, Bernard Davison
> <address@hidden> wrote:
>> Hi Florin,
>> 
>> Sorry I haven't had chance to read this whole thread yet... But I will do.
>> 
>> There is a currently active development effort to improve the hardware for
>> use in sounding rockets.
>> The rockets that I work with pull >70Gs and can get up to Mach 4.
>> 
>> I'll read the rest of this thread and get back to you with more details.
>> You might also like to join in on the skype conversation.
>> 
>> Cheers,
>> Bernie.
>> 
>> 
>> On 14/02/2012, at 10:25 PM, Florin Mingireanu wrote:
>> 
>> It works well.
>> Here are some photos obtained on a high altitude balloon mission that I
>> directed:
>>  
>> http://www.stiintasitehnica.com/imagini-i-mai-uimitoare-delta-dunarii-i-marea-neagra-vazute-din-stratosfera_803.html
>> 
>> We used the altitude branch of the problem... :-)
>> 
>> 
>> 
>> On Tue, Feb 14, 2012 at 1:21 PM, Chris Gough <address@hidden>
>> wrote:
>>> 
>>> 
>>> I believed that for an accurate and fast estimation, the GPS system
>>> required ASIC/FPGAs "expensive" propietary architectures, more than one
>>> receptor along the fuselage (allowing for measuring Euler angles), etc.
>>> 
>>> 
>>> I don't know much about that. I thought they used fancy ASIC/FPGA stuff in
>>> satellites so they could fix them over the wire when the chips got holes
>>> punched through them by very fast dust.
>>> 
>>> I believe carrier-phase correction (in dgps) is more much harder at speeds
>>> greater than 1/2 a wavelength per message duration. By Shannon-Nyquist,
>>> there's not enough information to disambiguate the direction of the phase
>>> error, so you have to mix in more information from somewhere. Maybe that's
>>> what fancy dual antenna systems are doing.
>>> 
>>> One off-topic question, is the hardware is not a limit, why some GPS
>>> modules are limited to about 20km of altitude? is this done deliberated? and
>>> this is not an actual limitation in firmware/hardware? I can not see why the
>>> system could work at 13km of altitude and not at 20km, the atmosphere layer
>>> is the same, the signal/line of sight should be better, etc.
>>> 
>>> 
>>> Section 11, part (c)
>>> 
>>> Global Positioning System (GPS) or similar satellite receivers; (1)
>>> Capable of providing navigation information under the following operational
>>> conditions; (i) At speeds in excess of 515 m/sec (1,000 nautical
>>> miles/hour); and (ii) At altitudes in excess of 18 km (60,000 feet)
>>> 
>>> Note the "and"; logically I guess that means one or the other is ok, just
>>> not both. I don't know how that works out in practice.
>>> 
>>> Chris Gough
>>> 
>>> 
>>> 
>>> On Tue, Feb 14, 2012 at 11:29 AM, Chris Gough
>>> <address@hidden> wrote:
>>>> 
>>>> 
>>>> About GPS measuring Ground Speed and ECEF Position at high velocity, I
>>>> really do not know about how the accuracy is affected, Doppler effect, etc.
>>>> 
>>>> 
>>>> It's not physics, it's firmware. Limits are result of treaties.
>>>> 
>>>> Http://armscontrol.org/documents/mtcr
>>>> 
>>>> See section 11.
>>>> 
>>>> But it seems that you need an expensive GPS module.
>>>> 
>>>> 
>>>> The firmware/hardware isn't more expensive, only the paperwork. You have
>>>> to prove you won't pass it on, among other things.
>>>> 
>>>> Chris Gough
>>>> 
>>>> Héctor.
>>>> 
>>>> 
>>>> 
>>>> On Tue, Feb 14, 2012 at 2:34 AM, Chris Gough
>>>> <address@hidden> wrote:
>>>>> 
>>>>>> Does the paparazzi code accomodate velocities as large as Mach 2- Mach
>>>>>> 3?
>>>>> 
>>>>> I don't know, sorry (don't see why not though, try it in
>>>>> simulation...). Maybe someone else can comment on that.
>>>>> 
>>>>> Do I understand you correctly:
>>>>>  * the rocket will go directly where you aimed it, it's not actively
>>>>> "navigated'
>>>>>  * the autopilot is not responsible for maintaining vertical attitude
>>>>>  * your instruments require a constant orientation (roll in the
>>>>> rocket's frame of reference) during the preiod between boost and apex.
>>>>>  * your experiments require position and attitude logging during the
>>>>> same flight phase.
>>>>> 
>>>>> Chris Gough
>>>>> 
>>>>> 
>>>>>> Best regards,
>>>>>> Florin Mingireanu
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> _______________________________________________
>>>>>> Paparazzi-devel mailing list
>>>>>> address@hidden
>>>>>> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> .
>>>>> 
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>>>> 
>>>> 
>>>> 
>>>> 
>>>> --
>>>> Héctor
>>>> 
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>>> 
>>> 
>>> 
>>> --
>>> Héctor
>>> 
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>> 
>> 
>> 
>> --
>> Florin Mingireanu
>> Romanian Space Agency
>> Str. Mendeleev 21-25, et. 5, sector 1, 010362 Bucuresti, ROMANIA
>> office tel. +40-21-316.87.22; +40-21-316.87.23;
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