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Re: ArcJet Update



Dear All,

I should add a few points to Stacey's excellent summary.
 
> 4.  Where did it go?
>      ----------------
> We don't have all the answers, and hence we have not yet posted a full
> report.  

There are a few things to remember...

We've got the ATOS (Arcjet Thruster on Oscar Satellite) for free 
and we designed/build the power supply for it in return.

We haven't yet posted a full report, because those who build and
designed the ATOS should have a chance to review all the fact we
could provide and probably make an official conclusion out of it.
It's their business, not ours..
They are currently looking in every possible direction, doing
a failure tree analysis and it would be unfair to post something
based on speculation, which is than published everywhere..

We only know that everything was done on our side to make it a
success.  

We were lucky to get the perigee raised enough, so that we don't
have to worry about the low perigee. Yes, we were told that it
is safe, but who knows... now we can feel *much* better.  We were 
also told that AO-13's orbit would be safe before we burned all 
the fuel..

What did the users missed?  Nothing...  There would not have been
enough ammonia for a significant change in inclination. Perhaps we
could have made 10-20° in inclination change, but than we would
periodically have bad coverage due to the precessing orbit, with
the apogee being over the wrong hemisphere (from either point of view)
for some time...  Instead we could have reduced the apogee height
making it a 16h orbit, but this also makes not such a big deal at
the low inclination and the pathloss also does not really get much
better..  so what?

Indeed, it is very disappointing that we could not demonstrate the
Arcjet burning "hot". On the other hand, ATOS has never flown before
and it is highly experimental and rocket science. At least we learned
that this type of TFMC (mass flow controller) is not flight worthy..
Something which could not have simulated on ground..

To be honest, we were not even sure if the Arcjet motor was still
there..  You all heard the speculations that the bottom plate was
blown away.. Obviously at least the motor was still there at the
right position and mounting angle... ;)

> 7. What's going to break next?
>     ---------------------------

No risk, no fun?

If everything would be so easy, than there would be no role
for AMSAT in space anymore...

There is no other way in trying..  but be assured that everything
and every possible failure mode was discussed in detail, before
any decision is made.  We don't use crystal balls. In fact, we were 
told that the failure mode of the TFMC is, that it gets shut and not 
open wide...

We will have enough time to check-out the momentum wheels.
And to be honest again, I would be surprised if they all work OK after
the possible destruction in the inner core of the spacecraft.
But we have no other choice, we must try! Also risk is predictable.
If everything goes well, we will proof test the 3-axis control
for a *long* time before we will deploy the solar panels (if et all).


> 8. And finally
>     -----------
>  We can withstand your critical scrutiny!   ...if
> we can't we need a new hobby.

Otherwise I wouldn't be here anymore, since I spent most of my life for
it since AO-10.


73s Peter DB2OS
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