On Orbit Thermal Verification for the −80°C Freezer 2003-01-2533
The Minus Eighty degrees Celsius Laboratory Freezer for ISS (MELFI) is a freezer that has been delivered to NASA as Laboratory Support Equipment (LSE) by ESA.
One of the main concerns during the development of MELFI has been first the intrinsic thermal performance of the system, and, second, the thermal performance once on orbit.
From the beginning the differences between the thermal performance on orbit and on ground were estimated through thermal analyses of the sub-systems to predict the behavior on orbit, and specific tests on ground simulating as far as possible a non-convective environment.
The results were used to define the criteria for the performance to be obtained on ground, which would ensure the compliance with requirements on orbit.
The complete verification campaign has demonstrated that the system is capable of giving the performance imposed by the criteria on ground for all mission aspects, including samples cooling down and protection during power-off.
The final acceptance of MELFI requires the demonstration of the thermal performance on orbit. Then, among the tests foreseen for MELFI on orbit commissioning, specific thermal tests will be conducted, which objectives are:
First, to confirm the overall system performance and, as a consequence, to validate the freezer concept for on orbit conditions,
Second, to verify that the samples cooling down rates are as required: a dedicated experiment (the MELFI On Orbit Commissioning Experiment) has been developed for validating the samples cooling down on orbit.
In addition these tests will allow all the hypotheses considered for extrapolating from ground tests the on orbit performance to be consolidated.
This paper presents the logic leading to the demonstration that MELFI is capable of giving the performance for all mission aspects on ground and on orbit.
