In fact, right up until the eve of Columbia's 22 October liftoff, NASA would continue to defend its decisions - many of which, to be fair, had been made long before the Challenger disaster - to launch such a small cargo. The questioning did not just relate to the presence of LAGEOS-2, either, for the Shuttle also carried the first United States Microgravity Payload (USMP-1). Not to be confused with the large Spacelab flown on Columbia's previous mission, this, too, was a small cargo which some critics argued should have been flown alongside a 'major' payload, or not at all.
Did the presence of what were essentially two secondary payloads require an entire mission, they asked, with all the risks involved, not to mention the enormous pricetag, which ran into several hundred million dollars? NASA's reply was that its commitment to ASI to launch LAGEOS-2 had been signed before Challenger, and the agency intended to honour it. Questions over the worthiness of USMP-1 to fly on Columbia as a primary payload were best answered by Al Diaz, NASA's deputy associate administrator for space science, who rhetorically asked journalists, ''How do you determine how much Nobel Prize science is worth?''
Diaz was referring in particular to one of USMP-1's three investigations: the Lambda Point Experiment (LPE), which sought to test a complicated theory of the thermal conductivity of liquid helium which had won mathematician Kenneth Wilson the Nobel Prize in 1982. It predicted that, under the right pressure and conditions, liquid helium would conduct heat a thousand times more efficiently than copper, but it could not be realistically tested on Earth because of gravitational interference. Wilson's theory was considered to have wide-ranging applications from studies of hurricane dynamics to superconductivity.
When activated, the LPE examined liquid helium as it changed, through a transitional phase known as its 'lambda point', from a 'normal' fluid into a substance called a 'superfluid'. In this latter phase, the helium moves freely through small pores that block other liquids and conducts heat far more efficiently than copper. The LPE investigation cooled a liquid helium sample far below its minus 268 Celsius lambda point and then, during a series of two-hour, computer-controlled experiment runs, its temperature was slowly raised and measured with an accuracy of less than a billionth of a degree throughout the transitional phase.
''To visualise how precise that is,'' said LPE designer Reuben Ruiz of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, ''think of the distance between Los Angeles to New York City as one degree. On that scale, one billionth of a degree would be about the thickness of a human hair!'' Joining the LPE investigation on the USMP-1 payload were two other experiments: the Materials for the Study of Interesting Phenomena of Solidification on Earth and in Orbit (a French-language acronym which spelt 'MEPHISTO') and the Space Acceleration Measurement System (SAMS).
The former was a cooperative US/French project to study the behaviour of metals and semiconductors as they solidified to help determine the effects of gravity on the point at which the liquid met the solid (its so-called 'solid/liquid interface'). It was
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