Planes you'd never heard of

Dave Rogers said:
Well, really I suppose it's the difference between the nose shapes of the Firefly and the Fulmar really, but the underside of Griffon installations tends to be a lot less sharply curved than a Merlin, as well as it being noticeably longer.

Dave
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The Griffon does appear a bit "fatter", but since Fairy designs were generally not very sleek, I wonder if it would show up on the outside. Just the other day had a look at a Firefly (there's one in a Danish museum), and it looks like a tractor compared to a spitfire. Of course, it was meant for a different purpose, but it still comes over as big and clumsy.

Hans
 
Trebuchet said:
I've a vague recollection of driving through Seattle many years ago and seeing a Sea Dart being hoisted over a fence to the Museum of Flight, then in development and not open yet. It probably wasn't.
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Maybe it was. There was a Sea Dart in Seattle, but it was later moved to Lakeland, FL. "In the last half of the 1960s, YF2Y-1 Sea Dart number 135765 was secured by the Pacific Northwest Aviation Historical Foundation for possible inclusion in the Museum of Flight. This Sea Dart had been at Seattle’s Sand Point Naval Air Station until the museum moved it to the Renton, Washington, airport as seen." BTW Lakeland and Kissimmee are less than 60 miles apart, and that might be the reason why there is some confusion about the location of one of the Sea Darts. Besides Lakeland, there are also Sea Darts in San Diego, CA and Willow Grove, PA.
 
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Does the Lockheed D-21 reconnaisance drone (unmanned, disposable, and originally designed to be launched from the M-21 Blackbird) fit within the OP?
https://en.wikipedia.org/wiki/Lockheed_D-21

Mach >3.3 and operational altitude of 90,000 feet.

Not very successful.

One is in the Museum of Flight in Seattle WA.
 
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Giordano said:
Does the Lockheed D-21 reconnaisance drone (unmanned, disposable, and originally designed to be launched from the M-21 Blackbird) fit within the OP? .
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Yup. :)


MRC_Hans said:
And made obsolete by satellites.

Hans
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I remember (I think) the US having to dig out the old U2s when they realised that you can't just have a satellite stay on station. Has that been solved?
 
3point14 said:
I remember (I think) the US having to dig out the old U2s when they realised that you can't just have a satellite stay on station. Has that been solved?
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That has to be a myth. First of all, you can (geostationary orbit). Also the trick with spy satellites was (and is) to have them in a low, highly declined orbit, so they will sweep as much of the planet as possible, really fast.

However, the problem at the time of the cold war was the quality of pictures. Transmitting bandwidth from satellites was still rather limited, and the resolution of electronic cameras was low, actually deplorably by our present standards. So it was still used to take analog pictures on film, then have the satellite develop them and either drop them back down on Earth or transmit them by a telefax-like slow scanning method.

- So in certain instances, the U2 might still have been preferable. Especially when not over central enemy territory, so the risk of getting shot down was lower.

Hans
 
MRC_Hans said:
That has to be a myth. First of all, you can (geostationary orbit). Also the trick with spy satellites was (and is) to have them in a low, highly declined orbit, so they will sweep as much of the planet as possible, really fast.
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The other reason you want them in a low orbit, rather than geostationary, is because there's an upper limit to the size of the optics you can launch into space. For reconnaissance and espionage, you'll want to those optics to be close up for maximum resolution and detail.
 
3point14 said:
I remember (I think) the US having to dig out the old U2s when they realised that you can't just have a satellite stay on station. Has that been solved?
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What is this? I can't even... Do you seriously believe this?

Do you seriously believe that anyone actually involved in aerial or orbital reconnaissance, at any point in the history of those disciplines, was ever under the impression that planes wouldn't be needed because satellites in LEO could hover?

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I remember (I think) the US ending up keeping U2s in service because sometimes you need a plane and the U2 is often more cost-effective option for aerial reconnaissance than the SR-71.

The SR-71 being a great example of the kind of "peak effectiveness" you get when there's a military need that dismisses cost as a consideration. When it absolutely, positively, has to be photographed right now, in a denied airspace... Use a satellite if you have one coming up. Or use an SR-71. For everything else, there's the U2.

One advantage to aerial reconnaissance is that satellite schedules are known, and peer enemies will schedule their operations to avoid making pretty pictures for the orbital cameras. If they're going to move when the satellites are away, you want to at least be able to get a plane there for coverage while the action is happening.
 
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MRC_Hans said:
That has to be a myth. First of all, you can (geostationary orbit). Also the trick with spy satellites was (and is) to have them in a low, highly declined orbit, so they will sweep as much of the planet as possible, really fast.

However, the problem at the time of the cold war was the quality of pictures. Transmitting bandwidth from satellites was still rather limited, and the resolution of electronic cameras was low, actually deplorably by our present standards. So it was still used to take analog pictures on film, then have the satellite develop them and either drop them back down on Earth or transmit them by a telefax-like slow scanning method.

- So in certain instances, the U2 might still have been preferable. Especially when not over central enemy territory, so the risk of getting shot down was lower.

Hans
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I have to tell you, I really don't think you're right that satellites make spyplanes/drones obsolete. The U2 is still in service. I'm pretty sure that the US does have global, 24hr satellite coverage and that they like the ability of the U2 to observe a specific area at a specific time which, I believe, cannot always be done by satellite.
 
theprestige said:
What is this? I can't even... Do you seriously believe this?

Do you seriously believe that anyone actually involved in aerial or orbital reconnaissance, at any point in the history of those disciplines, was ever under the impression that planes wouldn't be needed because satellites in LEO could hover?
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No, I was being florid (however, while none of those you list would be unaware of the limitations, I do not have the same confidence that elected officials would grasp the limitations). I do believe, however, that the US authorities, at one point, overestimated the effectiveness of their satellite network and that spyplanes are still an extremely useful thing.

The SR71 was reactivated after it was retired and the U2 is still in service.
 
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Chris_Halkides said:
Maybe it was. There was a Sea Dart in Seattle, but it was later moved to Lakeland, FL. "In the last half of the 1960s, YF2Y-1 Sea Dart number 135765 was secured by the Pacific Northwest Aviation Historical Foundation for possible inclusion in the Museum of Flight. This Sea Dart had been at Seattle’s Sand Point Naval Air Station until the museum moved it to the Renton, Washington, airport as seen." BTW Lakeland and Kissimmee are less than 60 miles apart, and that might be the reason why there is some confusion about the location of one of the Sea Darts. Besides Lakeland, there are also Sea Darts in San Diego, CA and Willow Grove, PA.
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Interesting, thanks for that! I'm not so sure that the picture was actually taken in Renton, due to what appears to be the first prototype 747 in the background. I was of the impression that the Renton airport is too small for 747's. I'll have to dig a bit.

ETA: Boeing did operate some 747's to Renton early on, for refurbishment after the flight test program. One landed a bit short and ripped the landing gear off.
 
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theprestige said:
One advantage to aerial reconnaissance is that satellite schedules are known, and peer enemies will schedule their operations to avoid making pretty pictures for the orbital cameras. If they're going to move when the satellites are away, you want to at least be able to get a plane there for coverage while the action is happening.
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One can, if required, alter a spy satellites orbit at need to get it where you need it to be. Down side of that is the sat's useful life dwindles rapidly every time such a thing might occur, and there is a delay before you get to the intended result.

Altering a sat's orbit is a big decision. You invalidate it's primary mission, wipe years off it's effective lifespan in a jot and have to repeat the exercise again to get it back on mission. Satellites don't carry a whole bunch of RCS fuel in the first place.

Easier to send a plane if it is urgent.
 
3point14 said:
I have to tell you, I really don't think you're right that satellites make spyplanes/drones obsolete. The U2 is still in service. I'm pretty sure that the US does have global, 24hr satellite coverage and that they like the ability of the U2 to observe a specific area at a specific time which, I believe, cannot always be done by satellite.
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Actually it was a specific unmanned supersonic drone we were talking about. The advantage of things like the U2 is to get in in a specific place at a specific time, but at a risk.

Drones are back for that, but an entirely different kind.

Hans
 
Geostationary can only be stationary (relative to a point on the ground) above the equator. You could launch a satellite into a 24-hour circular orbit inclined relative to the equator, but then it would trace out a repeated figure-8 path over the ground going through the crossing point of the 8 above the equator twice per day.

Also, geostationary is about 22,000 miles up, and you don't tend to get very good resolution photos of the ground from that high. Most reconnaissance satellites are in much lower, much faster orbits and pass overhead real fast - so you need a lot of them if you want to get regular updates of what's happening on the ground at one particular location.
 
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MRC_Hans said:
That has to be a myth. First of all, you can (geostationary orbit).
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No. Satellites in geostationary orbit cannot be used for optical surveillance. They are 36,000 km away from the earths' surface.

The angular size of an object at a distance is calculated by the formula

d / D x 206265 = R

where
d is the actual size of an object in meters
D distance to that object in meters
R is the resulting angular size in arc-seconds

So a 1m object at a distance of 36,000 km is

1/36,000,000 x 206265 = 0.0057 arc-seconds

To put that into perspective, the Hubble Space Telescope (which is equipped with a 2.4m mirror) has a resolution of 0.1 arc-seconds (I have posted the formula and calculations at the bottom of the post)

Hubble is 17.5 times too small to resolve a 1m object from geostationary distance. If it were possible to use Hubble at geostationary distance, its best resolution would show objects smaller than 18m as a single pixel! To put it another way, for a geostationary optical surveillance satellite to resolve a 1m object at ground level, its optical element (mirror or lens) would have to be 42 metres in diameter!!

MRC_Hans said:
Also the trick with spy satellites was (and is) to have them in a low, highly declined orbit, so they will sweep as much of the planet as possible, really fast.
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Unfortunately the downside is that satellites have to follow orbits, and those orbits are precise, predictable, and cannot be kept secret. This means that the countries you are spying on know precisely when those satellites will be over the installation you are trying to photograph right down to the hours, minutes and seconds, so they can act accordingly. This is what Lockheed Skunk Works at Area 51 knew when they were developing the SR-71/YF-12A (then known as OXCART) while the Soviets were spying on them. They knew not to have the prototypes and testing models outside at certain times of the day. (Even so, they still boobed in a rather amusing way https://news.nationalgeographic.com...ecret-hid-craft-base-declassified-a-12-plane/) *scroll down to "Shadows of Area 51"

MRC_Hans said:
However, the problem at the time of the cold war was the quality of pictures. Transmitting bandwidth from satellites was still rather limited, and the resolution of electronic cameras was low, actually deplorably by our present standards. So it was still used to take analog pictures on film, then have the satellite develop them and either drop them back down on Earth or transmit them by a telefax-like slow scanning method.

- So in certain instances, the U2 might still have been preferable. Especially when not over central enemy territory, so the risk of getting shot down was lower.
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It doesn't matter how advanced digital imagery gets, the Laws of Physics has limits, and one of those limits is the wavelength of visible light - it requires "X" amount of optical element diameter to get "Y" amount of resolution and there is no way around it.



* * * * * *

Formula and calculation
The theoretical resolution of a telescope is calculated using the formula

R = 11.6 / D

where R is the the angular size of the object in arc-seconds and D is the diameter of the mirror in centimetres. The HST mirror is 2.4 meters (240 cm), so we can calculate that its theoretical resolution is 11.6 / 240 = 0.05 arc-seconds. (For comparison, the diameter of the moon as viewed from the Earth is half a degree, about 1800 arc-seconds

There is a slight problem with this however. Due to factors involving interference patterns and the wavelength range of visible light, the smallest resolvable object is about twice the theoretical resolution. This is given using something called Nyquist's Theorem; you can read about it here.

http://en.wikipedia.org/wiki/Optical_resolution#Sensor_resolution_.28spatial.29

So effectively, the HST's resolution is about 0.1 of an arc-second.
​
 
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U-2 never got decommissioned & then resurrected. At least into the 1990s, they had been in continuous use since their start, including for some other countries.

SR-71 did get temporarily brought back once. I have the idea stuck in my head that it was for one of the wars in Iraq, but that might be because I know the same thing happened with battleships at that time and the memory leaked over.

It might seem like the simplest solution for surveillance from above would be to just have enough satellites up there that when one gets too far from the subject another gets close enough. A dozen, for example, would be enough to put them only 30° apart from each other, which would put any point on Earth in line of site to 5-6 of them at all times. A low orbit might mean each one zips by in under an hour, but the job can just be handed off to the next one in line. I long presumed that that must be the way it is these days, although not during most of the life spans of U-2 & SR-71. But it turns out that the number and orbits of satellites that we've actually launched haven't been arranged that way. Given that there are lots & lots of other satellites for civilian functions (or both, like GPS) up there, this can't be because better military coverage would cost too much, so I wonder why...
 
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