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Aviation Week -- April 23, 2001:
Proteus Completes
Pacific, Polar Mission
MICHAEL A. DORNHEIM/LOS ANGELES
Scaled Composites' Proteus high-altitude aircraft
has completed a five-week government science mission throughout
the Pacific Rim, capped by atmospheric measurements taken
over the North Pole at 48,000 ft.
For some missions, Proteus may serve as an
alternative to NASA's ER-2 research aircraft, which are
converted Lockheed U-2 reconnaissance aircraft. The trip
demonstrated the reliability and cost of the one-of-a-kind
Proteus over an extended period and a range of conditions.
Scientists are pleased with the flexibility
of dealing with Scaled Composites' operation. They can be
adjusting instruments almost until engine start and make
mission changes quickly, something that is not possible
with the elaborate procedures of the ER-2s, flown by pilots
in cumbersome
pressure suits.
Proteus was carrying a large belly pod containing
two atmospheric sounding instruments--NAST-I, which uses
infrared interferometry, and NAST-M, which measures microwave
emissions ( AW&ST Nov. 20, 2000, p. 34). These may be
used in next-generation Earth observation satellites, and
NASA's Langley Research Center was funding the flights to
support this effort. The payload
weighed about 1,300 lb., and the total pod weight was around
1,700 lb., said Michael W. Melvill, Scaled vice president
and general manager.
The aircraft took off from Scaled's Mojave,
Calif., base on Feb. 19 and flew to Honolulu, Majuro Island
in the Marshall Islands, Guam, Kadena AB on Okinawa, Yokota
AB near Tokyo, Eielson AFB, Alaska, and returned to Mojave
on Mar. 26. It made an 11.6-hr. flight on Mar. 23 from Eielson
AFB to the North Pole, the longest of the journey.
Total flight time was 123 hr. with no significant
problems, and the aircraft was always within a day of its
planned schedule. The flight started six weeks after contract
approval. The active Scaled crew was two pilots and two
ground crewmen, and the mission was tracked at Mojave via
Inmarsat satellite telephone voice and data link, which
worked below 78 deg. Lat. The mission operated under a $680,000-fixed-price
contract, good for up to 160 hr., or an average of $4,250/hr.
This covered all expenses, including airfare and hotel bills
for ground support. Estimated from NASA budget figures,
the basic cost for an ER-2 is about $20,000/hr., or five
times higher.
Proteus has a fore and aft wing configuration
and is powered by two Williams-Rolls FJ44-2A turbofan engines
modified to operate at up to 65,000 ft. It set a sustained
altitude record of 61,919 ft. for its weight class in October,
with the instrument pod removed. Pilots Melville and Michael
T.
Alsbury have enough confidence in the composite structure
and pressurization systems that they wear flight suits instead
of pressure suits in the room-temperature cockpit. Though
designed for 10 psi., it is operated at 7 psi., which requires
supplemental oxygen at higher altitudes.
In the tropics, ceiling can be limited by
very cold temperatures instead of performance, Melville
said. The tropopause there is higher than at the upper latitudes,
so the temperature continues to lapse down to lower levels.
Cold temperatures, e.g. -125F, let nitrogen pressure leak
past landing gear seals
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