Sesame street's Count:
"One launcher? Two-launcher!"
George William Herbert
Sent from my iPhone
On Jan 5, 2016, at 11:23 AM, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
On 1/5/2016 11:48 AM, George Herbert wrote:
It's only slightly larger than the 610 gal drop tanks (2,300 liter)...
George William Herbert
Sent from my iPhone
..which always seem to get carried on the F-15 wing pylons in pairs. (Or at
any rate, in every photo I found in a two-minute google images scan. ;-)
(And, these days, which almost never get dropped. I'd guess they cost too
much to be treated as routinely disposable.)
Assuming there's an aerodynamic-asymmetry problem behind this practice, then
carrying an ALASA on one wing pylon plus a counter-balance on the other might
require dropping the counter-balance at the same time as the ALASA. Messy.
Heh. Or just launch ALASA's only in pairs...
Henry V
On Jan 5, 2016, at 5:38 AM, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
On 1/4/2016 5:42 PM, George Herbert wrote:
On Jan 2, 2016, at 6:49 AM, John Schilling
<John.Schilling@xxxxxxxxxxxxxx <mailto:John.Schilling@xxxxxxxxxxxxxx>>
wrote:
On 12/30/2015, Henry Spencer wrote:
My understanding -- not that I was following ALASA closely -- is that
that was the original plan, but they eventually decided that dropping
the tank gained them so little that there was no point. Mitch
Burnside Clapp (who is/was the ALASA project manager), at last
spring's Space Access, described it as "the only launcher whose stage
count changed after PDR". They decided to leave the engines where
they were, partly because volume constraints under the F-15E made it
difficult to move them -- the payload volume tapers toward the rear,
and the engines can't be too close together because ALASA uses
differential throttling for control.
In any case, ALASA is grounded and probably dead. Two consecutive
safety tests of their N2O/acetylene mixed monoprop [aieee!! aieee
cubed!!] went KABOOM KABOOM a month or so ago, and that kind of
spoiled the enthusiasm for it; see
<http://spacenews.com/darpa-airborne-launcher-effort-falters>.
Mitch's comment on the monoprop last spring was "there are reasons
why this is not entirely insane", but apparently it was insane enough...
You understand correctly on the engine location. That's the only place
you can put engines big enough for ALASA and not either block the
landing gear doors or have the nozzles turn into divots on the runway
when the F-15E rotates for takeoff.
Ok.
I am officially bugged by something.
F-15 inboard heavy wing stations 2, 8 have the same rated load (3,500 lb
officially but have carried 5,250 lb GBU-28) as the centerline station.
Why all this to makee fit under centerline again?...?
Yes, you have additional ballast weight on the other side and a bit more
drag, but not that much...
George William Herbert
No answers, just speculation:
Those wing stations are a fair distance off the centerline. Given the size
of the ALASA vehicle (24 feet long, ~2+ feet in diameter, much lower
density & more surface area than the usual ordnance) there could be aero
issues with carrying it on one side under a wing, in addition to the mass
balance issues. Assuming these off-center loads could be safely balanced
at all, the performance hit of balancing both aero and mass loads may have
been enough to unduly reduce max available pullup for the release.
Then too, I make the volume of the thing to be very roughly 3 cubic meters,
which assuming overall package density of ~1, means it might be somewhat
overweight even for that demonstrated 5,280 lbs capacity you mention.
Could the center station structure have more margin than the wing stations?
There's also the possibility that they're piggybacking off aero work
already done for a steep climbing release off the center station for the
ASM-135 ASAT tests way back when, rather than spending the extra money to
qualify such a release off one of the wing stations.
Henry V
