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AO-40 Orbital Changes - answers please?



I just re-read the following on the Amsat-DL website and decided that
there's a couple of things here that need explaining and I request that the
appropriate people put up explanations.

on 6/29/01 3:50 PM, Peter Guelzow at peter.guelzow@arcormail.de wrote:

> The perigee height raised from 280 km before the outgassing to 851 km
> after, while the apogee height is unchanged.
> 
> The good news is indeed, that AO-40 is now in a safe and stable orbit!

This is the first point.  I thought that AO-40 WAS in a safe and stable
orbit.  According to the information posted on the DL site several months
ago, Stacey Mills and James Miller calculated that AO-40's orbit would be
safe and stable for years.  Yes there would be quite a bit of oscillation in
the perigee but it was safe.

Is this now incorrect?  And if that information was wrong, how are we to
guarantee that we are really currently safe and stable?

> 
> The bad news is, that probably all our 53 kg of ammonia is gone.
> 
> Since orbit #302 the ammonia stopped flowing and the pressure indicators
> in the telemetry show no more pressure in the motor and in the ammonia
> tanks, while the perigee is much higher than anticipated.

So how did this happen?  Is there some software bug that left the vapor
flowing constantly?

Below is from the DL site posted 6/18:

> 6) If we want to raise perigee by 200 km, we could thrust for 4 hours around
> apogee for 20 orbits and get there.
> 
> 7) We would consume 8 kg of our 53 kg NH3 in the process.
> 
> 8) We can theoretically outgas for 8 hours around apogee with the mass flow
> regulator set to 95% and raise perigee about 200 km in 10 orbits.

OK, the original Perigee height was around 280 km.  The goal was to raise it
200 km which would be about 480 km.  This was expected to take 8 kg of
ammonia.

Now we ended up with a height of 851 km.  How?  Were the mathematical
calculations performed that far off?

Instead the orbit was raised by nearly 600 km or 3 times the originally
desired amount!  How did this happen?

Yet this still does not explain why all 53 kg of ammonia are gone.  If 200
km takes 8 kg, one would expect then that 600 km would take 24 kg of
ammonia.  We should still have half our ammonia left.

So far there have been no answers to these at least from what I have seen.
It's great that we now have a more stable orbit.  I say more stable because
AO-13's orbit was originally thought to be stable, and we were originally
told that the previous orbit of AO-40 was stable.  However, we now have no
more maneuvering capability left with the bird.  Gone, done, kaput.  For
what purpose and for what reason?

I've been very supportive of the command team throughout the whole AO-40
ordeal, but I just find it very difficult to defend or justify the repeated
problems and disasters that have occurred in the propulsion system arena.
First it was a plug in the main engine that should have been removed that
wasn't.  Now it's an arc jet that mysteriously lost all its gas.

Are we spending so much money to really fly this much by the seat of our
pants?

I know I am being very critical here and some will say that I shouldn't
judge since I'm not in the position of the control team.  I agree that I
hardly know the first thing about orbital mechanics.  However, the people
that are in charge are supposed to be the experts.  That's why they are
there and I am not.  Is the expertise that lacking?

73,

Jon
NA9D


-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Member:  ARRL, AMSAT, DXCC, NRA

http://www.qsl.net/ke9na

"A life lived in fear is a life half lived."

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