TTIUWP
Posted on 04/28/2007 9:51:02 AM PDT by BenLurkin
A modified 747 airliner designed to carry an infrared telescope took its first flight Thursday, one of several checkout flights planned before it makes its way to a new home at NASA Dryden Flight Research Center at Edwards Air Force Base.
The Stratospheric Observatory for Infrared Astronomy, or SOFIA, consists of a 2½-meter in diameter infrared telescope mounted inside the 747 airliner, chosen for its ability to house the 45,000-pound telescope.
The long-range airliner is capable of remaining airborne for six hours at altitudes higher than 41,000 feet, above much of the atmospheric water vapor.
SOFIA will be used to study the universe in the infrared spectrum, as well as to develop observational techniques, instruments and for educational purposes.
Thursday's flight took place in Waco, Texas, where the airliner has undergone extensive modifications by L-3 Communications Integrated Systems. Dryden research pilot Gordon Fullerton commanded the flight crew.
The airliner is outfitted with 16-foot-high clamshell doors in the rear of the fuselage, which will open in flight to allow the telescope access to the sky.
The door is in two parts, a rigid upper portion that opens to expose the cavity, and a flexible lower portion attached to the telescope that moves up and down with the instrument.
The cavity itself is a cylindrical hole in the side of the aircraft, the largest ever intentionally cut into a working aircraft.
A bulkhead was installed forward of the cavity, in order to pressurize the rest of the aircraft cabin in flight. The telescope bay is unpressurized as it will be open to the outside when in use.
"Now we are into a body of work to try to finish development of the aircraft, to try to expand the working envelope," said John Carter, project manager for the platform at Dryden.
(Excerpt) Read more at avpress.com ...
TTIUWP
Thanks!
My impression is that a flying aircraft vibrates, and a telescope better not vibrate if one wants to get sharp pictures, especially at longer exposures. Now, their IR telescope is heavy, and vibrationally isolating it from the body of the aircraft would be non-trivial.
Oh come on! A 747SP can cruise from LAX to SYD at up to 51,000 feet. That's a lot longer than six hours.
Where somebody will immediately assume it's transporting 50 tons of Cocaine the first time they see it in the air.
Guess that's why I'm not a NASA scientist....
This is the current version of the Kuiper. I was around it a lot when I worked for NASA. Flying observatories have been around for quite a while.
“Now, their IR telescope is heavy, and vibrationally isolating it from the body of the aircraft would be non-trivial.”
Heavy is better for vibrational damping.
It’s possible that the weight of its payload is such that they have to limit the amount of fuel they can carry. It would be a trade off. The laws of physics don’t care what the load is, just how much there is of it.
Not with a twenty-foot hole in it...
Tell it to aerial photographers who use gyroscopic stabilization rig in which the camera with its lens are mounted. The bigger the camera/lens, the bigger, more unwieldy, and heavier the stabilizing rig is.
I doubt it has anywhere near the normal load of a fully loaded 747SP. An SP had about the passenger capacity and range of a 777-200ER, so it could carry about 300 passengers. The open observatory door must cause a considerable amount of drag.
“The bigger the camera/lens, the bigger, more unwieldy, and heavier the stabilizing rig is.”
Obviously the weight of the dampening mechanism goes up, the question is in what proportion. Actually, both our answers are wrong. The vibration will be a function of how close the combined suspended mass-spring-damper system excitory frequency is to the input frequency. The input frequency in this case is dependent on the mass of the airplane, the spring constants of the airframe and suporting air, the dampening air friction and the vibrational energy inputs from the engines and air pressure and wind velocity fluctuations.
I think the easiest way to figure that out is to just stick a mass on a support and fly it for real.
If the supported thing is to remain stationary when the base vibrates with acceleration a, then the force acting on the supported body [to be dampened out] is F=ma, per Newton- directly proportional to the mass [of telescope]. Thus the size of dissipating system [within the same technology] is more or less proportional to the supported mass, mounting harness [with its mass] could be considered as a part of the supported body. For the several sizes of gyroscopic stabilization rigs it seems to bear out. The trouble with them was not so much their weight [747 would be able to handle it] as the general clumsiness and spatial requirements.
That was the best purchase they ever made IMO.
I wish them good luck and safe flying!
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