Edouard Lafargue <[email protected]> writes:

>    I understand that once the unit is in Pad mode, it becomes pretty much
> fully autonomous and won't take commands anymore, which I assume is a good
> security feature.

That was, indeed, the primary motivation for being transmit-only in pad
mode and during flight.

> That said, there can be situations where it would be
> useful to revert back to a "safe" or "idle" mode in case launch is
> aborted.

Yep, we agree.  

> Is there any way this can be done on the Telemetrum?

So there are two problems.  I suspect neither is insurmountable, but
Keith and I haven't ever come up with a good solution.

The first is that once in pad mode, the most important task is detecting
launch.  Anything that detracts from that is a problem.  Since we're
using a multi-tasking system, it's entirely possible that we could check
for a ground command from time to time between telemetry bursts without
compromising launch detection.  But since our radios are half duplex,
any time we spend listening for commands is time we can't be sending
telemetry, etc.  And with increasing complexity comes greater risk,
which translates into a need for more testing every time we touch
anything in the firmware to make sure we haven't broken essential
operation. 

The second is that once you've handed control over the LCO, anything that
might cause the airframe to become *not* ready to launch remotely opens
up the possibility of an airframe being launched that would not fly
safely.  There's no way for our boards to know, for example, whether the
launch system has been put in a safe mode and/or the igniter has been
pulled such that it's "safe" to go out of waiting-for-launch state.

We have, therefore, just accepted the fact that once you're in pad mode,
you can't get back to idle using only radio.

If anyone has both strong feelings about this *and* and explicit
suggestion about how to add the feature in a way that mitigates
risk... feel free to let us know!

Bdale

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