[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: AO40: status

on 1/5/01 7:43 PM, MCGWIER ROBERT at rwmcgwier@home.com wrote:

> Furthermore it is clear that it the increase in
> angular momentum has occurred around the
> Z axis since the spacecraft does not appear
> to have an appreciable wobble.  The only
> place I can see from a quick look for this
> to happen is in the tubes that flow propellant
> around the motor casing.


I have more questions for you.  I thought about just sending this directly,
but thought people might have the same questions.  I'm not calling into
question your knowledge on stuff because it seems to be pretty significant.
But humor my ignorance and my possibly "stupid" questions.

>From looking at the drawings of the space craft we have the following
components in the following bays (only pertinent ones mentioned):

Bay 1:  LIU and propellant flow assembly, BCR, Sensor Electronic Unit
Bay 2:  S-2 Transmitter, L-band RX 2, IHU-2
Bay 3:  S-1 band TX, V and U band RX and TX
Bay 4:  IF matrix
Bay 5:  L-band RX, IHU-1 and BCRs

OK, now if the propellant leaked out of somewhere in the propellant flow
assembly (again - I am assuming that propellant flows in the "Propellant
Flow Assembly") has the leak, then you'd expect items in bay 1 to be heavily
damaged.  However, we do know the BCRs work and the sensors work (most of
them).  Additionally, the VHF transmitter is a long ways from bay 1 and it
would be more likely that any propellant floating between bays would screw
up something in bay 2 or bay 6 first.  The S-2 TX is in bay 2 so that's

Now you aren't saying this is where you suspect the leak.  I'm just thinking
out loud here and am hopefully voicing some thoughts of others too.....

OK, where are the tubes that flow propellant around the motor casing
located?  Are they in the internal part of the spacecraft? In other words
inside the "center panel" shown on the exploded view on page 10 of the
November Journal?  Or are they outside on the engine cone?

If they are internal, then how would a propellant leak inside the craft
cause an increase in rotation of the craft.  It's been a while since
Physics, but I know a rocket motor works on the principle of action and
reaction (Newton's Second Law).  So for a force in a given direction, there
is an equal force in the opposite direction.  OK, but if we are internal to
the craft then the propellant spews out creating a force with an equal and
opposite reaction.  But then that propellant stream impacts the internal
cavity of the space craft and creates another force with an equal and
opposite reaction which pretty much cancels out the force from the
propellant escaping from the tubes.  It is my understanding that in order to
Newton's Second Law to work, the force has to be applied external to the
system otherwise opposing forces cancel each other out.  That's the reason
why you can't pick lift yourself up by your feet even in weightlessness.

So the way I see it, the leak would have to get OUTSIDE the craft and at a
rate and in a direction to increase the spin.  If the leak occurred internal
then one might suspect it might ooze out through various panels of the
craft, but then you wouldn't likely get enough going in one particular
direction to increase the spin.

Now if the propellant leak is by the cone of the motor, that is outside the
craft, we would satisfy the conditions to cause the craft to increase the
rotational speed.  However, here's what we know.  From what you and others
have said, it looks pretty clear that the spacecraft is rotating on its
Z-axis and in the direction that the control team had previously determined
before the motor burn.  What are the odds of having a propellant leak that
is for one a leak which is opposite the direction of the spin (thereby
causing the spin to increase) and second in the same plane as the surface of
the craft top (that is orthogonal to the engine cone itself).  What are the
odds of such a "favorable" leak to occur?  Also, if the leak did occur
around the engine cone, wouldn't we expect to see damage to the antennas?
It does indeed appear that the S-2 and L-band antennas are working just
great.  Also, you'd expect to get attitude and sun sensors damaged.....

Secondly, if the leak did occur on the outside of the space craft, how did
it get inside to potentially damage wiring harnesses, etc?  For one, how
well are the individual spacecraft components sealed?  Two wouldn't any
external propellant leak flow away from the craft?  It would have to
particularly if it is in the amount you suspect that would cause the
rotation to increase.  So in a micro gravity environment, how does a liquid
propellant having a particular force to spin the craft and that is flowing
orthogonal to the Z-axis of the craft, get inside?  And if it did get inside
through where the motor is mounted (center panel) how likely would it be to
make its way through the fuel tank section and then into the electrical
section.  Again, how sealed off is each equipment bay/compartment?

Now perhaps I am just really showing my ignorance in a public forum.  If so,
shame on me, I deserve it.  Perhaps I am missing something right in front of
my nose.  I could very likely be or maybe my logic is flawed.

Anyhow, just my potentially dumb and embarrassing questions that surface in
my mind to try to make sense out of all this.



Jon Ogden
NA9D (ex: KE9NA)



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

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org