[FPSPACE] Burnt Frost starts to melt.. .! NOT!

[Jim Oberg]

my comments to Butt's article:


Perhaps there is less to these apparent contradictions than meets the eye. 
For the first shuttle missions I served on the 'Propulsion Officer' team 
overseeing the auxiliary engines and their support plumbing, and I recall 
that even at launch the tanks had a significant 'empty space' filled with 
pressurization gas. It was this ullage volume that provided the 'push' to 
transfer liquid propellant into the lines leading to the engines, and this 
ullage volume is clearly seen in the drawing of the tank on the first page 
of the linked NASA document. As a result of such mass asymmetry, the USA-193 
tank would have settled with the forward end - exposed to highest 
temperatures - coated inside with cold hydrazine, in frozen or slush form, a 
very efficient heat sink. Secondly, although Dr. Butt interprets the term 
"node" to mean "layer of tank skin", my own experience is that it refers to 
mechanical concentrations such as attach points or pass-throughs. This is 
consistent with the classic definition of the word, "A knob, knot, 
protuberance, or swelling," but not with Dr. Butt's usage. Hence his 
conclusion that the tank skin very nearly burned through reflects, in my 
view, an inadequate understanding of the word.



More seriously flawed is his contention that the tank nearly melted because 
the outside temperature rose higher than the melting point of the tank 
material. This is a problem in fundamental thermodynamics. The fate of the 
exposed material in question is not dependent on the exterior temperature 
but on the amount of heat that exterior can transfer into it. If the 
exterior heat is very high but is also materially very tenuous (as in the 
near-vacuum conditions of 100 kilometers up), the amount of HEATING it 
induces in the skin may be minor, especially if the skin is in contact with 
a very cold mass behind it - as in this case. As to how cold that mass would 
have become in space (the number that was mysteriously "dictated" to the 
NASA team, the experts competent to calculate it would be those with full 
knowledge of the satellite's mechanical structure and flight profile - its 
owners, operating at a classification level higher than needed by the NASA 
analysts (we know that derelict satellites even in near-Earth orbit fall 
well below 0º C, from experience).



>From my own spaceflight operations experience and familiarity with actual 
atmospheric entries and fallen object recoveries, I find the analysis that 
shows a tank with cold hydrazine is very likely to survive to ground impact 
to be eminently plausible.  While Dr. Butt argues that the opposite is 
"certainly" true, it seems that this is the conclusion that he has always 
wanted to reach from the beginning, as shown in his earlier writings on the 
subject, and is independent of competent engineering analysis.