Hot answers tagged

90

First of all, it took at least five years even back then, but your observation is absolutely correct. You would need to go back one more decade to find a frontline fighter that was designed within two years. The reasons are: Urgency: Back then, the Cold War arms race forced both sides to continuously improve. Together with the advances in weapons and ...


87

There are quite a few reasons for this- technically speaking, the primary one is that the system complexity has increased tremendously. More systems mean more interfaces, more redundancies, meaning more chances of failure and more troubleshooting. The modern combat aircraft is expected to perform a wide variety of missions, which would've been performed by ...


64

Why did they stop building it? Because they built 32, and that was as many as was needed at the time. 32 spy planes was plenty for the USAF/CIA to use, so building more would have been a waste. By the time those airframes may have needed to be replaced after 30 years or so, the SR-71 had been withdrawn from service and there was no need to build any more. ...


63

The SR-71 Blackbird was equipped with specialized cameras. It would overfly the area of interest and take high-resolution pictures of the ground. Of particular interest is the Technical Objective Camera (TEOC). It could shoot pictures with a 6'' resolution from the operational altitude of the SR-71. This task was not simple as the aircraft would have moved ...


42

The SR-71 had a detachable nose (photo #2), and could change between three different nose cones depending on the mission. I haven't found a lot of information on the three, other than what this site and this site mentions: Training nose with dead weights Radar nose containing a Side Looking Radar. This is probably the bulge you saw on the photos. Photo ...


41

UPDATE: I want to clarify/emphasize a few things in my answer. #1: Ultimately, the core driver of development time is growing complexity. More advanced threats means more advanced systems, which usually means more complexity. Your opponent gets a bigger radar, so you need a bigger one to see him first. You add jammers to shorten his effective radar ...


34

Could SR-71 be shot down today? Theoretically yes. Modern day SAMs like the 40N6 that travel at speeds of Mach 6 can intercept an SR 71 within an operational range of 250 miles upto an altitude of 18 miles. Moreover, the hostile SAM will fire a salvo of missiles(at least 2-3). So the SR 71 will have to jam, drop decoys and out manoeuvre the incoming hostile ...


32

The SR-71 was only capable of Mach 3.3 flight at altitude. You can see the limitations in the pilot's operating handbook(POH) for the aircraft: At higher altitudes the relative speed of sound is lower. If we use this handy NASA calculator in a standard atmosphere the relative speed of sound at 70,000 ft. is 660 MPH making your 2193 MPH equal to Mach 3.321 ...


29

To avoid overheating, the usual trick is to select the right material: The Concorde used a special aluminium alloy, called Hiduminium, which had higher strength at elevated temperatures and allowed the Concorde to cruise at Mach 2.02. Aluminium melts at 660°C. The MiG-25 used stainless steel instead of aluminium to make its top speed of Mach 3.1 possible (...


29

This is the section of the original SR-71 operation manual that describes in detail how the camera works. The plane was equipped with an Optical Bar Camera "The Optical Bar Camera (OBC) is a high resolution panoramic camera with a "folded" ----------- lens system. It provides continuous ------- or --------- coverage along the flight track through an ...


24

It did! You can see a bit of it here or in the reflection here And here it is from the exterior


22

There are forward-facing windows in the SR-71. The image you posted is just of the instrument panel. The windows are better visible in the photo below. This is from a simulator but gives a better idea of what the cockpit looks like when in flight. The windows and cockpit are small due to the high speeds and altitudes that the plane is designed for, making ...


20

According to the performance data in the manual it takes 19.9 minutes to get to 70,600 feet. Refueling time will depend on how much fuel is needed for the mission as well as how long it takes to hook up to the tanker. The manual covers the operations for that but I dont see a flow rate of fuel in there. A lot of that stuff is covered in this podcast.


19

A jet engine compresses air, heats it by mixing it with fuel and burns it, and lets the heated air escape at the end, where it accelerates to more than its initial speed in a convergent-divergent nozzle because the density of the heated gas is lower, thus needing a higher volume at the same pressure. By converting the kinetic energy of the flow into ...


19

The Turn Radius of the SR-71 would depend on its speed. The faster it went the wider its turn radius was. The SR-71 had a minimum turning radius at altitude of about 80 nautical miles (NM) . It was not an airframe limitation but a matter of wing area. At 80,000ft, the air is too thin and the wings too small to allow for much lift to turn with. At a turn ...


18

The limiting factor for subsonic aircraft, including the U-2, is well explained here. For supersonic aircraft this answer simply says the limit is "a combination of wing loading and maximum speed". If you look at the flight envelope of the SR-71 below, it becomes clear that more altitude can be best bought with more speed. SR-71 flight envelope (picture ...


16

In the age of computerized design, drafting, testing and milling, we can develop products faster than ever before. It's definitely not technology slowing down development. When we develop a plane for the future, whether it's for the Air Force or commercial aviation, we tend to focus on planning, and developing plans for the future. When Boeing and Airbus ...


15

Generally, a compressor cannot work efficiently at supersonic speed due to the shockwaves, the role of the inlet cone and diffuser is to slow the air below Mach 1. There is a similar need for a ramjet, so that the combustion can occur within the engine and produce thrust. The cone position and diffuser geometry are adjusted according to the airspeed. The ...


15

This is just an additional point, but a bit more than a comment. In the late 60s there was still a cohort of design/test personnel whose skills and attitudes were formed during WWII and the early stages of the cold war. On the test side, the likes of Chuck Yeager and John Stapp were still active. Their careers were built on taking personal risks of a ...


14

Because the requirements were different. When U-2 was developed, the requirement was for an aircraft which would fly high at 70,000' due to the (mistaken) belief that the Soviets would be able to detect and engage aircraft only below that altitudes. Once the U-2 entered service however, it became obvious that they could detect U-2 (they complained about the ...


13

The 'triangle' wing design that you refer to is pretty common. It is called the delta wing design and is used in a number of high speed aircraft, for example, the North American XB70 Valkyrie. In fact, the SR 71 wing planform is also a delta, if one removes the engines. One of the reasons is that the wings of the aircrafts are kept inside the Mach cone ...


13

Please use the equations of this answer. The numbers might be different, but the physics are the same. EDIT: Thanks to D_S for providing the link to the manual. When flown with the maximum allowable load factor of 1.5 g at 80.000 ft (48° bank), the turn radius at Mach 3.2 (equivalent to v = 953.3 m/s in 80.000 ft) will be 83.5 km. To be more precise, you ...


13

For several reasons: First off, the SR-71 was a plane which was never intended. An earlier Blackbird incarnation, the single seat A-12 had been in service for several years with the CIA under the codename Oxcart. When the veil of secrecy was lifted and the USAF discovered it, the Air Force demanded to be responsible for strategic aerial reconnaissance. ...


12

Both the MiG-25 and MiG-31 designs had engines that would overheat and be damaged an anything past Mach 2.83, so both planes were limited by this. Typical speeds were closer to Mach 2.5 to extend the life of the planes. The highest aerodynamic heating occurs at the leading edges. It's possible that the MiG designs used titanium in these areas but opted for ...


11

Is it possible to use refrigeration technology to cool down the aircraft's skin so it can reach much higher speeds? Fundamentally: no. Refrigeration technology moves heat energy around, it doesn't get rid of it. Your fridge moves heat from inside to the outside. To get rid of it, you have two means, broadly speaking: Heat up some mass and throw it away ...


10

I'm reasonably certain the speed limit (so to speak) on the SR-71 wasn't to prevent its skin from melting. The hottest the skin got during flight was less than 600 C. That's definitely hot--but it's a long ways short of the melting temperature of titanium (1668 C). Early supersonic aircraft often had control problems, because the leading edge of the air ...


9

I'd like to answer with a focus on the SR-71, since I happen to have a book that gives details on its design. Ben Rich was the lead of the propulsion and thermodynamics group for the SR-71, and Kelly Johnson's successor as head of the Skunkworks for later programs. In the "Faster Than a Speeding Bullet" chapter of his memoir Skunkworks (pg 203 in the first ...


8

Like every military aircraft built over the years, the aircraft evolve. So to address the aircraft's history and all variants, let's refer to it as the Blackbird. The Blackbird started out as the A-12 procured for the CIA. Fifteen of these were built with one being a 2-seat trainer. Two of the 15 were modified into M-21 aircraft prior to delivery. The M-...


7

Actually, the task of the diffusor was to create thrust. Sounds strange? Then read on! At supersonic speed the spike ahead of the inlet will create a cascade of ever-steeper shocks in order to slow down and compress the air. Inside, the cross section narrows down further until the flow is decelerated to below Mach 1 in a final, straight shock. This is the ...


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