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https://theaviationgeekclub.com/u-2-vs-sr-71-former-usaf-avionics-technician-explains-why-the-dragon-lady-still-flies-spy-missions-while-the-blackbird-had-been-

https://theaviationgeekclub.com/u-2-vs-sr-71-former-usaf-avionics-technician-explains-why-the-dragon-lady-still-flies-spy-missions-while-the-blackbird-had-been-retired/ https://theaviationgeekclub.com/u-2-vs-sr-71-former-usaf-avi... Why the SR-71 was retired over the U-2 which is still in service today: > For a mission over a target in the Middle East with the planes based in England, [the SR-71] needed to have multiple airliner size aircraft in the air to support it. > It was not capable of taking off with a full load of fuel (or rather, not advisable for many reasons), so in order to take off, there had to be a tanker waiting in the air to top it off once it got airborne. > It would then make a high speed run to the target zone where it would meet up with another tanker before doing its Mach 3 run over the target. It would then need to tank up again once the recon run was done for the trip home, and then there would still be a tanker in the air on standby in case it needed gas before landing or in case it needed to divert for weather or something. > So that’s a minimum of 4 airliner sized support aircraft, including all of their parts, fuel use, and crew, flying out of a minimum of 2 different bases just to make a single SR-71 operational mission happen. > And that’s on top of all the crew, fuel, parts and mechanics just to operate the SR-71. This sounds like dev hell, and yet a viable dependable product. I wonder how many big corps operate the same behind the scenes.

WhatsName 3y ago
As the saying goes NKAWTG - Nobody Kicks Ass Without Tanker Gas
jprd 3y ago
Most of them. It is Excel workbooks all the way down.
Gravityloss 3y ago
There's a term "hangar queen" for aircraft that fly a little and need a lot of maintenance. Sometimes you want extreme performance at any cost. But a lot of the time you want a good enough performance at low cost. The amount of supporting resources and length of maintenance breaks etc affect cost, or the amount of aircraft you need to get in order to be able to do the mission. If you have 20 aircraft but 15 are being maintained, you only have 5 flyable ones, you still had to pay for acquisition of all the 20, and have to pay for the ongoing maintenance for the 15. If you have 10 but only 5 are maintained at any given time, you have the same flying capacity of five aircraft but your total costs are likely going to be much less as you only had to acquire ten aircraft and only have to have maintenance people enough for 5 at a time. This is really hard to explain to a lot of people in the software industry by the way. They say a feature is complete, my job is done. But if it's extremely hard to configure, deploy, monitor, maintain etc then it might turn out to be a net negative. It's the whole iceberg that counts, not the tip.
2OEH8eoCRo0 3y ago
> So that’s a minimum of 4 airliner sized support aircraft, including all of their parts, fuel use, and crew, flying out of a minimum of 2 different bases just to make a single SR-71 operational mission happen. Why can't it be 2 support aircraft? Is the SR-71 mission too long for the tanker to stay in the air? The tankers can also service other aircraft so they aren't necessarily put in the air exclusively for the SR-71. It's still an expensive plane though.
- qbrass 3y ago
  The SR-71 won't be anywhere near the first tanker when it needs fuel again. The fuel itself isn't common to most aircraft, which means the tanker has to carry fuel specifically for it so it.
  - bradknowles 3y ago
    Correct. The SR-71 uses JP-7 fuel, and is the only aircraft in the fleet known to do so. So, the USAF has to have custom KC-135Q tankers just for SR-71s. They can't be used for any other fuel. The thing that made it obvious to me that there was a replacement for the SR-71 was that when they retired the aircraft, they didn't retire any of the tankers. That meant there was now some other unknown aircraft flying that also used JP-7, and it must therefore be the replacement for the SR-71. Note that JP-7 is so hard to light on fire that if you throw a match into a bucket filled with JP-7, the match will get snuffed out. You've got to be a lot hotter than a match to light that stuff.
    - satiric 3y ago
      Your anecdote about JP7 being hard to light in fire is also true for pump gas. The liquid gas is not flammable, only the aerosolized gas is.
      - bradknowles 3y ago
        But if you did the same experiment with 87-93 octane gasoline, you would set the fumes on fire as the match went into the bucket. And those fumes would continue to burn. The same is not true of JP-7.

WhatsName 3y ago

As the saying goes NKAWTG - Nobody Kicks Ass Without Tanker Gas

jprd 3y ago

Most of them. It is Excel workbooks all the way down.

Gravityloss 3y ago

There's a term "hangar queen" for aircraft that fly a little and need a lot of maintenance. Sometimes you want extreme performance at any cost. But a lot of the time you want a good enough performance at low cost. The amount of supporting resources and length of maintenance breaks etc affect cost, or the amount of aircraft you need to get in order to be able to do the mission. If you have 20 aircraft but 15 are being maintained, you only have 5 flyable ones, you still had to pay for acquisition of all the 20, and have to pay for the ongoing maintenance for the 15. If you have 10 but only 5 are maintained at any given time, you have the same flying capacity of five aircraft but your total costs are likely going to be much less as you only had to acquire ten aircraft and only have to have maintenance people enough for 5 at a time. This is really hard to explain to a lot of people in the software industry by the way. They say a feature is complete, my job is done. But if it's extremely hard to configure, deploy, monitor, maintain etc then it might turn out to be a net negative. It's the whole iceberg that counts, not the tip.

2OEH8eoCRo0 3y ago

> So that’s a minimum of 4 airliner sized support aircraft, including all of their parts, fuel use, and crew, flying out of a minimum of 2 different bases just to make a single SR-71 operational mission happen. Why can't it be 2 support aircraft? Is the SR-71 mission too long for the tanker to stay in the air? The tankers can also service other aircraft so they aren't necessarily put in the air exclusively for the SR-71. It's still an expensive plane though.

qbrass 3y ago
The SR-71 won't be anywhere near the first tanker when it needs fuel again. The fuel itself isn't common to most aircraft, which means the tanker has to carry fuel specifically for it so it.
- bradknowles 3y ago
  Correct. The SR-71 uses JP-7 fuel, and is the only aircraft in the fleet known to do so. So, the USAF has to have custom KC-135Q tankers just for SR-71s. They can't be used for any other fuel. The thing that made it obvious to me that there was a replacement for the SR-71 was that when they retired the aircraft, they didn't retire any of the tankers. That meant there was now some other unknown aircraft flying that also used JP-7, and it must therefore be the replacement for the SR-71. Note that JP-7 is so hard to light on fire that if you throw a match into a bucket filled with JP-7, the match will get snuffed out. You've got to be a lot hotter than a match to light that stuff.
  - satiric 3y ago
    Your anecdote about JP7 being hard to light in fire is also true for pump gas. The liquid gas is not flammable, only the aerosolized gas is.
    - bradknowles 3y ago
      But if you did the same experiment with 87-93 octane gasoline, you would set the fumes on fire as the match went into the bucket. And those fumes would continue to burn. The same is not true of JP-7.