SIGNIFICANT EVENTS - FUTURE FLIGHT PROGRAM
02/18/00
Low Temperature Microgravity Physics Facility Experiments Chosen
Science Concept Reviews (SCRs) were held this week for three candidate experiments for the
second mission M2 of the Low Temperature Microgravity Physics Facility (LTMPF), which is
scheduled to launch in August 2005. The SCR requires the investigator team to show the
value of the science to be obtained in their experiment, to demonstrate the need for the
microgravity environment to accomplish the science objectives, and to present a preliminary
version of the Science Requirements Document for their experiment. A panel composed mostly
of peer scientists, but also containing engineers familiar with flight requirements, selected
the Boundary Effects on the Superfluid Transition (BEST) experiment and the Superconducting
Microwave Oscillator (SUMO) experiment to proceed to the Requirements Definition Review.
SUMO, proposed by Principal Investigator John Lipa of Stanford, intends to use the LTMPF
on ISS to place two superconducting cavity-stabilized oscillators in orbit with a second
type of clock (located elsewhere on ISS) to test several aspects of the Equivalence Principle
of General Relativity. If SUMO can be flown concurrently with a laser-cooled atomic clock
such as those presently being developed for flight experiments in our program, both the SUMO
science goals and the LCAP clock experiment goals would be enhanced. Improvements in reducing
the uncertainty in several relativistic effects are estimated to range from factors of 26 to
2500 in the stand-alone mode (no LCAP clock experiment on ISS), and from 50 to 240,000 if
flown simultaneously with a LCAP clock.
The BEST experiment team of Principal Investigator Guenter Ahlers of the University of
California at Santa Barbara will fly three samples of liquid helium on ISS to conduct a
comprehensive set of studies of critical thermal transport of 4He confined in planar and
cylindrical geometries. By flying an unconfined bulk sample of liquid helium, a sample
confined in cylinders of 50-microns diameter, and a sample confined in planar channels
having 50-micron gaps, the experiment will be able to observe the transitions from bulk
(3-dimensional) behavior to both 1-dimensional heat flow and 2-dimensional heat flow as
the liquid helium is brought closer to the critical temperature. The experiment will
thereby be able to test the universal scaling functions that describe finite-size effects
for the different dimensionalities.
The science and engineering panel unanimously endorsed the importance of the science of
all three M2 experiments and encouraged the Experiments Along Coexistence near
Tricriticality (EXACT) team (Principal Investigator Melora Larson of JPL) to continue
their work to develop a microgravity experiment.
