Water Dumps

One of the spectacular effects that can sometimes be witnessed during a shuttle mission is that of a water dump. Throughout the flight electrical power on board the orbiter is provided by fuel cells. These combine hydrogen and oxygen in a reaction that yields electricity; one useful by-product is water (in fact the reaction is not unlike the electrolysis of water but in reverse). Of course, the water can then be consumed by the astronauts in the course of their daily activities. This spent water and any excess from the original reaction is disposed of by simply venting the liquid to the vacuum of space. In doing so the water rapidly cools condensing into a cloud of ice crystals. Under suitable lighting angles and conditions this has been seen as an almost cometary tail extending from the orbiter.

During the STS-73 mission of October 1995 daily water dumps coincided with passes over the southern US states and a number of observations were made including this one by Cal Deal at 0626 EDT, 26 October:

[Shuttle 'Headlights'] [Shuttle 'Tail']
Cal sketched out his own impression of the phenomenon reproduced above in the first image. The second image pictures the second event he described (these images Cal Deal).

The fact that this was a microgravity mission may have contributed to the spectacle - the persistence of the cloud and its proximity to the orbiter arising from the lack of maneuvers. He also described the following morning pass:


Gordon Garradd took the following photograph during the STS-85 mission in August 1997. Gordon is located in Loomberah, Australia at 151.0E/ 31.3S at 845 M (ASL).

water dump
Photo Gordon Garradd

Craig Cholar, a subscriber of SeeSat-L, posted a notice dated Aug 15, 1997, informing the List of the next scheduled water dump for STS-85. He provided estimated times for the water dumps that periodically occur during a mission.


Jeff Poplin and others on SeeSat-L on Dec 25, 1999 posted reports of observation of a water dump during the STS-103 mission.


Paul Maley, who is an experienced satellite observer, has produced an excellent web site on satellite observing.

Paul took a video of STS-103 over the Houston, Texas area on December 25, 1999 on the shuttle's 2nd orbit since releasing Hubble just NE of Australia earlier. Below is a frame taken from that video with the shuttle and the ice crystal coma on the left and Hubble following closely behind (but at a slightly higher altitude). The other objects below are stars.

water dump
(Photo Paul Maley)

Search on "waste water dump" at NASA.


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