Re: accelerations
Thu, 11 Jan 1996 02:22:12 -0500

Bart de Pontieu wrote:

>Dr. Hermann Boehnhardt even
>wrote an article about fuel leaks in (I think) Astrophysics and Space Science
>in the seventies, using data from Jean Meeus and Horst Koehnke (all in the
>PPAS now), and assuming a leaky valve. One of his results was (I think) that
>the acceleration is caused mainly by the effects of the mass loss on the
>moments of inertia. Another result was that better time coverage was needed
>to check for the effects of external torques. So, it is quite important to
>have daily coverage of these accelerations if we want to improve on models.

>Certain Soviet rockets do suffer from corrosion. I remember reading some-
>where (Spaceflight ?) that there were several cases of fragmentation ascribed 
>to corrosive fuel (or oxydizer?) eating its way through pipes, which then 
>comes into contact with oxydizer with an explosion as a result. I will have 
>to look up where I read this. Maybe Jim Varney can shed some light on this, 
>since he has access to this professional article about fragmentation. In any 
>case, viewed the above, my guess would be that corrosion can be a reason for
>certain accelerations. Just a guess ;-)

Interesting... with the corrosion model, sooner or later there
ought to be an outgassing torque which would apply a moment counter to the
direction of rotation.  I assume this because I think of corrosion as 
randomly appearing at different points around the R/B and releasing pro-
pellant.  Has a sudden deceleration of rotation ever been observed?

With the leaky valve model, I would think once it leaks and gets the R/B tumbling
that subsequent leaks would apply torques in the same direction and would
cause the accelerations we all observe.

Regarding the loss of mass/change in moment of inertia model, that makes sense
for a very slow outgassing and a gradual acceleration.  But it wouldn't explain
a delta in semi-major axis/mean motion.

Regarding the "History of Satellite Fragmentations," I'm still working on it...
it's taking longer than I hoped due to time constraints.  

I checked the document and, interestingly, it is the Soviet *payloads* which 
cause the lion's share of fragmentations, not the R/B's.  SL-3's are mentioned 
as spawning debris due to corrosion and environmental damage.  An SL-14 (1978-100D) fragmented into 42 (trackable) pieces in 1988.  The SL-8 of 1991-09J spawned 70 
pieces of debris, but the author noted that this was the first SL-8 to fragment 
in 25 years and 370 missions.

I would be careful to read too much into this -- maybe what we are seeing is a
tendency for Soviet R/B's to leak, but not explode and fragment.

Good Passes,

Jim Varney          |  121^ 23' 54" W,  38^ 27' 28" N   |     Sacramento, CA
Civil Engineer      |            Elev. 20 ft.           |