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

From:

Florin Mingireanu

Subject:

Date:

Tue, 14 Feb 2012 09:51:59 +0200

I was refering to Mach as the sound speed at ground level.

So it can be done without expensive systems- at least from what they say on their website.

Florin

On Tue, Feb 14, 2012 at 9:42 AM, Hector Garcia de Marina <address@hidden> wrote:

Hi Florin,

just for clarifying. For measuring Mach, you will need a FADS system (pressure sensors) and get around the problems about Temperature and Density of the atmosphere (speed of sound). Actually, for control purposes, the variable is usually the dynamic pressure (from FADS system).

GPS does not measure Mach (and of course Mach is not a velocity, it is an adimensional number xD).

About employing MEMS sensors for an inertial navigation in a rocket (may I ask what rocket is?) where the environment is hostile (heavy acoustic vibrations, heavy mechanical vibrations, etc). I do not know the current available devices, but I guess that you will need more than simple MEMS low-cost sensors for a decent navigation.

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. But it seems that you need an expensive GPS module.

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
>
>
>
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