A number of space telescopes including SIRTF are using superfluid helium as a coolant for the detector.   The dynamic properties of wave motion in superfluid helium in microgravity had never been observed.  Superfluid helium has the property of having no viscosity, and therefore damping of superfluid helium in a zero gravity state is small.  The SIRTF project was concerned that the sloshing of the SF helium coolant would disturb the pointing accuracy of the telescope on orbit.  Therefore an experiment was designed to record on video the motion of the superfluid in microgravity.  

A float package, seen below, was adapted from existing components, with a window in both side of both the external and internal tanks, such that  the moving fluid could be illuminated from one side and the motion captured on video from the other

Aside from the usual constraints of time, technical challenge, and cost, placing a dewar and pressure vessel aboard an aircraft required careful handling during flight safety reviews.  Other concerns were cryogen life, package weight,  capture safety, ease of operation, and data integrity.

The vessel was made leak tight against superfluid helium, and the package obtained the first videos obtained of superfluid helium, in a free state, in microgravity.  Superfluid data was obtained from the engineering test flight on through the run, and no additional flights were required.

The Superfluid Slosh Package "floating" in the DC-7

About this photo:  The image above shows the
superfluid helium dewar, probe and vacuum pump
assembly in free float, handled by two NASA Lewis
airmen during a typical data taking run.  Following
a series of "float" runs, the package is docked in
a heavy rest raining fixture during aircraft take-off
and landing.


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