Summary of Operational Capabilities

The Kennedy Space Center Gaseous Nitrogen (GN2) Freezer is a passive freezer container (requires no power) designed to hold samples at cryogenic temperatures (-196 degrees C) for between twenty-one and thirty-five days, depending on flight configuration and use scenario. The GN2 Freezer can be used for frozen sample transport to and from orbit and is certified to fly on the International Space Station. The sample area inside the internal tank can hold up to four cylindrical canisters 6 inches long and 3.7 inches in diameter (i.e. Biological Research in Canisters BRIC-60’s) in independently selectable ladles. A fifth identical cylindrical sample container can be placed in the center of the freezer, although such utilization makes it impossible to access any of the four ladles without first removing the fifth cylinder.

The GN2 uses similar technology to the JSC Life Sciences Support Equipment (LSLE) freezer (also known as "JSC cryodewar") flown regularly on the Space Shuttle and previously on the Mir Space Station. The major differences are that (1) the GN2 Freezer can hold samples at cryogenic temperature for a longer period of time; (2) the freezer is stored in a double, rather than single locker; (3) insulation material has been added to the vacuum chamber and (4) more than twice the cold stowage volume is available.

See line drawing of GN2.

Usage

The GN2 has flown on the following payloads:

Mission	Payload (Experiment)
STS-93	BRIC-11 (BRIC-11)
STS-95	BRIC-NASDA (BRIC-PEG/C)
STS-87	CUE (BPAC)
STS-87	CUE (GENEX)
STS-87	CUE (SOYMET)
STS-87	CUE (SOYPAT)
STS-93	PGIM-01 (TAGES)
STS-93	STL-B (BRIC-12)

Many different plant samples have been frozen including plants wrapped in aluminum foil, in agar on petri plates, encased in aluminum canisters, rolled in Nomex fabric and plant tissue in microcentrifuge tubes.

Technical Details

The freezer looks very much like a familiar cryogenic shipper, and in fact the two are very similar. It is designed to meet the need for a low temperature freezer that requires no power and eliminates the risk of spilling cooling material in case of a malfunction. The aluminum outer tank of the freezer houses both a vacuum container and an internal tank containing a hydrophilic fumed silica material which absorbs liquid nitrogen. Once saturated with liquid nitrogen, (a procedure known as ‘charging’ the freezer) the absorbent material releases only gaseous nitrogen into the internal sample containment area of the freezer, eliminating any spill hazards. Liquid nitrogen temperatures are maintained until the last couple of days before the freezer expires. The absorbent material is insulated with a combination foil, molecular sieve and palladium oxide getter. The vacuum container is insulated using foam and provides a thermal barrier between the absorbent material and the outside of the freezer.

The freezer charging process begins approximately 96 hours before launch by filling the freezer with liquid nitrogen. The charging process continues over a period of 48 hours until the absorbent material is completely saturated. The freezer is drained of liquid nitrogen approximately one hour before turnover of the payload for installation. The GN2 Freezer can be stowed in a double locker or equivalent volume in the Orbiter middeck, SPACEHAB, MPLM or EXPRESS Rack.