[X] My Assistant

[PhilHorzempa]

My purpose in starting this new thread is to review what we know
about the demise of the Mars Observer. As most know, the Coffey
review board concluded that vapor migration in the propellant
lines led to explosive mixing whenthe system was pressurized.
However, several other possible scenarios for the mishap were
possible, and in my opinion, perhaps, more likely than vapor migration.

My 'favorite' alternate model for MO's end concerns the pyro valves on
the Mars Observer. As I recall, they were similar to ones on Landsat 6.
I have not been able to find a final report for the demise of Landsat 6 on
the Internet. However, if my memory is correct, it was concluded that
the pyros in the Landsat 6 attitude control system ruptured the propellant
lines during the launch process. The Landsat 6 was launched on a Titan 2
and depended on an SRM for the final kick to orbit.

Landsat 6's ACS was to control attitude during the solid rocket burn.
However, the rupture in the prop lines caused all prop to bleed away.
Therefore, the satellite tumbled during the SRM burn, causing it to fall
short of orbital velocity.

I think that something similar may have happened to the Mars Observer.


Another Phil

[dvandorn]

Ah, but Bob -- suppose you had *two* cats? You gonna call them Cat 1 and Cat 2?

At least when JPL was flying Lunar Orbiters, they only had one in space at a time... and in fact, they *would* have had a hard time with more than one going at once, since they all used the same radio frequencies and command sets. Speaking to LO2 would cause a problem if LO1 was still intact, "awake" and listening. Both would have responded to the same commands.

They had the same problems with the Surveyors, and as I recall, they were actually considering postponing some Surveyor flights, waiting for one of the predecessors already on the Moon to finally die.

Also, I think that the first series of craft to do something can easily be named after the function it's supposed to perform -- like Lunar Orbiter. Try naming a spacecraft series Lunar Orbiter today, and there would be a flurry of issues. Or, try naming each of the craft orbiting Mars now "Mars Orbiter" -- it would get awfully confusing, awfully quickly...

-the other Doug