>As a simple example: How can the chances of the probe
malfunctioning be a
>million to one? Do you really believe NASA on this one?
I don't think that the million-to-one estimate refers to a generic
malfunction of the probe. I think that it refers to the specific
malfunction of a course error during a specific time window of the
mission. That estimate, for example, explicitly does *not*
include launch failure, where re-entry friction does not represent
a factor.
A course error during that specific window-of-vulnerability would
represent a malfunction, while only a very small set of possible
course errors would result in a high-speed re-entry. From space,
the earth is a very small target. The velocities involved exceed
earth escape velocity, and so "decaying orbit" considerations
don't enter into the calculations.
I don't know the algorithm or the data used to calculate the
million-to-one estimate. The "roundness" of the number (a million
and not 500,000 or 2 million) leads me to suspect that the
algorithm involved inequalities, and represents a "not to exceed"
value rather than an exact value. When considered from the
perspective of the entire mission profile, it sounds pessimistic,
and not optimistic, to me.
-R
Richard Plourde .. rplourde@andesign.mv.com
"The word is not the thing, the map is not the territory"
http://www.crl.com/~isgs/isgshome.html
http://www.general-semantics.org/