3 ms·

Fastest official is Mach 3.43. I would note that that isn't likely the full story. The US Gov has famously been deceptive about the plane, both overselling or u

Fastest official is Mach 3.43. I would note that that isn't likely the full story. The US Gov has famously been deceptive about the plane, both overselling or underselling its abilities. (Notably, I do not believe that the US Government ever 'officially' admitted to overflying the USSR.) It is very possible that for a short period of time, they sustained over mach 3.5 or 3.6, what affect that would have/had on the airframe and engines is unknown. An interesting story is that once, during the cold war, a Mig-25 was supposedly tracked over Israel at over Mach 3.2 in what is best described as "GTFO" mode. It basically was an attempt to do what the US was doing with the SR-71s. At that speed, the engines are assumed to have been scraped after each flight. One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes, in the right airframe, with a lucky bin of build quality and weather, far beyond that. I would also note that this story buries the lede. The title states mach 3.5 but the pilot implies numbers beyond. I'm not sure how factual it is or if it is dramatized, but the pilot absolutely is who they say they are and wrote a book about it.

ranger207 4y ago
> At that speed, the engines are assumed to have been scraped after each flight. > One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes...far beyond that I would expect the SR-71 to stay at speed longer and for the engines to be capable of higher power (assuming the airframe and intake can handle it). US engines were generally higher quality, while Soviet engines were expected to be replaced very quickly relatively. However, this was a conscious decision on the part of the USSR: instead of making expensive engines with good maintainability in the field, they chose to make cheap engines that were easy to replace. As a result, while a MiG-25 may have only been able to maintain Mach 3 for a few minutes and ruin the engine in the process, they built 1,186 of them, with probably >5,000 Mach 3 capable engines. Not particularly relevant, but always interesting to discuss how different people think
- phkahler 4y ago
  The SR71 engines are the only ones ever designed to run continuously in after burner. Also in ramjet mode, going faster increased the efficiency as the bow shock swept back and into the engine inlets, providing pre-compressed air.

ranger207 4y ago

> At that speed, the engines are assumed to have been scraped after each flight. > One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes...far beyond that I would expect the SR-71 to stay at speed longer and for the engines to be capable of higher power (assuming the airframe and intake can handle it). US engines were generally higher quality, while Soviet engines were expected to be replaced very quickly relatively. However, this was a conscious decision on the part of the USSR: instead of making expensive engines with good maintainability in the field, they chose to make cheap engines that were easy to replace. As a result, while a MiG-25 may have only been able to maintain Mach 3 for a few minutes and ruin the engine in the process, they built 1,186 of them, with probably >5,000 Mach 3 capable engines. Not particularly relevant, but always interesting to discuss how different people think

phkahler 4y ago
The SR71 engines are the only ones ever designed to run continuously in after burner. Also in ramjet mode, going faster increased the efficiency as the bow shock swept back and into the engine inlets, providing pre-compressed air.