I remember that alkaline cells had a high power density

So far, non-rechargable batteries have a SIGNIFICANT power density
advantage over any rechargable technology.  It can be a bit tough to find
"amp hour" ratings for primary batteries, but one source I found rates a
typical AA alkalines at about 2.5AH, and a D at 13.5AH.  compared to 2AH
and 9AH for the best (expensive, new, lower voltage) NiMH cells.


    but at $xk a mission I would have thought that other alternatives would
    have been interesting. Either that or the price label of alkaline D
    cells normal humans can buy has the decimal point misplaced by about two
    orders of magnitude to the left.

Of course they don't pay retail prices.  Nor would they pay anything like
"retail price" for other battery technology either.  By the time you're
putting together 1.35 MWH of battery (you said 90,0000 D-cells), I expect
your per-mission price is "up there" regardless of technology.  Using
commercial cells as a base probably got them "battery packs" at a far lower
cost than teh equivilent custom-designed battery, since it's just an
assembly issue, instead of a design PLUS assembly issue...

BillW

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