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Old February 13th 17, 07:14 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Default Musk remains on Advisory Council

William Mook wrote:

Consider the Lockheed AH-56 Cheyenne - a compound helicopter configuration that gave the aircraft tremendous range and speed for a helicopter. It was also heavily armed!


It also never entered production for good and sufficient reasons. Do
you have ANY point here other than MookJacking another thread for no
applicable reason? If you do, it certainly isn't obvious.


Specifications (AH-56A)
Data from Jane's Aircraft and WarbirdTech AH-56A
General characteristics

Crew: Two; one pilot, one copilot/gunner (front seat)
Length: 54 ft 8 in (16.66 m)
Rotor diameter: 51 ft 3 in (15.62 m)
Height: 13 ft 8.5 in (4.18 m)
Empty weight: 12,215 lb (5,540 kg)
Loaded weight: 18,300 lb (8,300 kg)
Max. takeoff weight: 25,880 lb (11,740 kg)
Rotor systems: 4 blades on main rotor, 4 blades on tail rotor, 3 blades on pusher propeller
Powerplant: 1 × General Electric T64-GE-16 turboshaft, 3,925 shp (2,930 kW)


Note that the following numbers are largely bull****, since it was
never made to operate properly.


Performance

Maximum speed: 212 knots (244 mph, 393 km/h)
Cruise speed: 195 knots (225 mph, 362 km/h)
Range: 1,063 nmi (1,225 mi, 1,971 km)
Service ceiling: 20,000 ft (6,100 m)
Rate of climb: 3,000 ft/min (15.23 m/s)
Armament

Guns:
1 × nose turret with either an M129 40 mm (1.57 in) grenade launcher or an XM196 7.62×51mm machine gun and
1 × belly turret with an XM140 30 mm (1.18 in) cannon
Hardpoints: 6
Rockets: 2.75 in (70 mm) FFA rockets
Missiles: BGM-71 TOW missiles


See the AH-64 for what actually got built.


There are 10 Cheyennes floating around, and with a 375 unit order cancelled, lots of spare parts and pieces as well.


No, there aren't. There are FOUR (not 10) Cheyennes left in
existence, none in anything close to flyable condition. Three are
static displays and the fourth is in a museum. Nobody keeps spare
parts around for half a century, so there are not "lots of spare parts
and pieces". In point of fact, there probably were no parts for that
"375 unit order" other than a few long lead time items, since that
order was never funded.


Boeing's unmanned Little Bird was brought to flight readiness in a matter of months. It should be possible to do the same with Cheyenne, but with better computing platforms, greater capabilities! Including automatic weapon control! Which could be useful for defence as well as collecting unpaid bills!

Furthermore, the GE T-64 turboshaft engine the powers the Cheyenne, has already been modified to operate with hydrogen fuel!


Perhaps THE SAME could be done if there was any reason to do so,
although the AH-56 had serious handling problems even with a man in
the cockpit. I love how you assume all the extra work (which
essentially amounts to an all new helicopter with the exception of the
basic airframe) just happens by magic.


https://www.netl.doe.gov/publication...y/Anderson.pdf

For anyone familiar with the Breguet Range Equation you know using a fuel with 141.8 MJ/kg specific energy to replace the 42.6 MJ/kg jet fuel, increases payload and/or range, with the hardpoints on the Cheyenne its easy to see a zero boil off cryogenic tank could easily be added to the system, and range could be increased to 6,000 km and more - with the same payload as now. Getting rid of the more expensive missile systems, and maintaining an automatic cannon, still makes this a formidable unmanned drone for exotic delivery missions!


And of course you've included the difference in fuel density between
kerosene and LH2 into your calculations, along with increased weight
and drag from the magical zero-boil-off tank?

And what's the point of all this, again?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn