High Altitude Operations notes
As reported previously, after the Leuven conference [May
2011]]we had a group meeting at Moritz's office & discussed the challenges
of "perpetual" high altitude operation, particularly large arrays. Moritz
presented the basic calculations that predict strict limitations on
maximum altitude. Tether weight & wind drag accumulate with altitude &
especially when wind slacks one must come down or waste large amounts of
power to "reverse pump". Lets review means that ease the constraints.
Kites can be put all along a tether (a train) to mitigate increasing
weight & drag with altitude. With multiple tethers, some can be leaned
into the wind & develop some lift. A tether & kite sequence is
progressively tapered, with larger sections lower. The maximum altitude
state represents potential energy "in the bank" & AWECS aloft can be
driven for while by sink, promoting high capacity factor. In dying wind
the heaviest components can be run down promptly on halyards to greatly
reduce sink rate & reverse-pumping demand. A remnant structure of aerostat
lift can "reserve" a presence in the sky during calm. In rising wind the
sequence reverses & added power raises everything nicely. Moritz also
explained his intuition that a kite system deployment sequence be
naturally reversible to recover from a fault or adapt to any dynamic need.
One does not want unrecoverable conditions such as, say, a failed
ballistic launch might represent.
CoolIP ~Dave Santos June 3, 2011 M3664
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