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Propellant fluid dynamics at zero-g



I ran across an article today in New Scientist from 27-May-2000 which may be of
interest to the folks doing the post-mortem on the 400-N motor burn events.
Titled "Slosh, rattle and roll," it described how the "slosh" of liquids at
zero-g is poorly understood, leading to large spacecraft maneuver errors as
recently as two years ago when the JPL Near Earth Asteroid Rendevous satellite
badly missed a target in a course correction burn. The motor apparently was
starved of oxidizer at some point during the maneuver, due to "slosh;" the burn
thus terminating prematurely and with an unpredicted tumbling motion which
caused LOS for 27 hours. They minimized the effect of slosh in later burns by
making the burn durations small. "Slosh" can cause oxidizer/fuel starvation, or
excess (boom), at the site of combustion. If the propellant is a large fraction
of the spacecraft weight, it can cause unpredicted dynamics after the burn due
to the momentum of the liquid bouncing around.

This doesn't at first glance explain the 24 hour delay between the burn and the
AO-40 LOS. However, the subject of the article may merit some attention - I
havent heard it mentioned previously. And I definitely don't want to
second-guess or start a long thread of speculation.

This particular New Scientist article isn't available online, but the article
gives a URL for one of the more recent attempts at modeling what happens at
zero-g:

http://www.math.rug.nl/~veldman/cfd-gallery.html

steve rector - nu7b - AMSAT #31750
--
mailto:stefano@amug.org
home page:
http://www.fastq.com/~stefano/




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