5 ms·

I don't know much about aviation, but I know there's a plane that was faster than the SR-71: The X-15 [1]. I know because my great uncle died flying the X-15 o

I don't know much about aviation, but I know there's a plane that was faster than the SR-71: The X-15 [1]. I know because my great uncle died flying the X-15 on an experimental flight [2], so it's always been an interesting story for my family. [1] https://en.wikipedia.org/wiki/North_American_X-15 https://en.wikipedia.org/wiki/North_American_X-15 [2] https://theaviationgeekclub.com/the-story-of-mike-adams-the-only-pilot-to-lose-his-life-during-the-x-15-flight-test-program/ https://theaviationgeekclub.com/the-story-of-mike-adams-the-...

mr_overalls 8y ago
I find it absolutely incredible that the piloted speed record set by this aircraft - set in October 1967 when William J. Knight flew Mach 6.7 - hasn't been broken in 50+ years.
- rtkwe 8y ago
  It's a mix of things I think. First we haven't had a really big breakthrough in engine technology in a while and second there's no need to risk a person piloting these anymore because computers and remote control tech has gotten good enough.
  - ProAm 8y ago
    Wouldnt the scramjet engines be a pretty big breakthrough?
    - dmoy 8y ago
      Scramjet still needs air though, doesn't it? Thus it has to fly lower, and maybe can't get as fast as a rocket engine. Scramjet planes are faster than other non-rocket planes I would imagine?
      - darkpuma 8y ago
        The SR-71 cruised at Mach 3.2. Scramjets have been demonstrated to do Mach >5, and theoretically might be capable of something between Mach 17 to Mach 25(!!!) Scramjets do need air, although something to consider is that the faster you go, the more air you get. So at high altitudes with very thin air, you can go faster to get more air. In fact you have to go faster (true airspeed) in thin air anyways even if your brought along liquid oxygen for your engine, because as the air thins your stall speed will go up. The whole thing is a complicated system of equations. Engine capabilities and/or critical mach number (for planes designed for subsonic flight, like the U-2) of the airframe set an upper limit on how fast you can go. Air density decreases with altitude, increasing the stall speed (according to true airspeed, not indicated airspeed.) But for a given true airspeed, with increased altitude the temperature of the air drops, consequently dropping the speed of sound, which reduces the mach number. In subsonic planes as altitude goes up the stall speed and critical mach number eventually pass each other, beyond which your plane can no longer fly. The point of that intersection is known as the 'coffin corner'. In planes designed for supersonic flight passing the critical mach number isn't a problem, but eventually you'll reach a point where the drag on the aircraft is so great that the engines simply don't have enough power to overcome it. Increasing altitude reduces drag as the air gets thinner, but that only works for so long. Air speed inside the engines needs to be considered too. The airspeed past the turbine blades needs to be such that you won't get compressor stall. When you discard the turbine requirement, that's where things start to get interesting. A ramjet has no turbines, it compresses the air using the intake geometry. At full speed the SR-71 was actually producing most of it's thrust with a ramjet effect, most of the air going into the engines was not going through the turbines. The difference between a ramjet and a scramjet is that in a ramjet, the air inside the engine becomes subsonic again for the burn, but in a scramjet the air inside the engine remains supersonic. Scramjets could go really fast.
      - NamTaf 8y ago
        Yes, scramjets are faster than other non-rocket planes. They have a lower bounds of approx. Mach 3, but then go up from there. The big challenge is basically making sure that you mix your fuel with the air, combust it fully, and extract the energy before it flies out the back of the engine. Scramjets are the engines capable of this at the highest speeds.
- aristophenes 8y ago
  Maybe because once you start going faster than that there isn't much point staying inside the atmosphere? If you want to count spacecraft that record has been shattered.
  - siffland 8y ago
    It is like the land speed record. As soon as you get over a couple hundred miles per hour you might as well fly. So when you get to mach 6 you might as well be in space....
    - zik 8y ago
      And when you get to about mach 33 you might as well leave orbit.
  - greglindahl 8y ago
    There’s a huge new interest in hypersonic gliders.
- god_bless_texas 8y ago
  How do you know?
- pathikrit 8y ago
  The speed record for a car over a kilometer has not been broken since 1937 [1] [1]: https://en.wikipedia.org/wiki/Mercedes-Benz_W125_Rekordwagen https://en.wikipedia.org/wiki/Mercedes-Benz_W125_Rekordwagen
ceejayoz 8y ago
"Plane" is a bit of a misnomer for the X-15, though. "Rocket with wings" is more accurate.
- keymone 8y ago
  Elon wouldn't approve.
- darkpuma 8y ago
  There are some (mostly Brazilians) who would disqualify the Wright Flyer as the first airplane on the grounds that it took off from a rail. Is the engine breathing air really an essential part of the "airplane" definition? Solar Impulse 2 didn't breath air either, yet wasn't it an airplane too? @DuskStar It's certainly a glider on reentry. Now, most speed records for planes are "in level flight" which would disqualify the shuttle during reentry. But if we ignore that it's interesting that the speed record for manned aircraft is held by a glider, and the speed records for RC aircraft are also held by gliders! https://www.youtube.com/watch?v=MoaWlKC3wIM https://www.youtube.com/watch?v=MoaWlKC3wIM
  - DuskStar 8y ago
    Is the space shuttle a plane?
    - mehrdadn 8y ago
      I feel like a basic requirement for a plane would be that it can maintain its altitude, so no?
    - Anarch157a 8y ago
      The NASA Shuttle, no, the Soviet Buran, yes. As a Brazilian (see previous comments about the Wright Brothers), I consider that an airplane: * Is powered, otherwise, it's a glider; * Can maintain level flight, otherwise, it's just "Falling with style"; * Can take off on it's own, assistance (RATO, catapults) is allowed for short take-offs (like from a carrier); The Shuttle fails in all that in some point of the flight or another, Buran on the other hand, could be fitted with air breathing jet engines that allowed it to do all that.
quintin 8y ago
Man! Hacker News is so interesting with folks like you hanging around.
rurban 8y ago
There is a nice example now in popular culture of the problems of a X-15 in the beginning of the movie "First Man" with Neil Armstrong bouncing off the atmosphere in this rocketship. The other popular case, the only lost ship was also similar to the bad MCAS system in the Boeing 737max, the pilot forgot to turn off the problematic flight control system, and he didn't see the 90 yaw angle because he turned it off, so he raced straight down, and the control SW kept it that way.

mr_overalls 8y ago

I find it absolutely incredible that the piloted speed record set by this aircraft - set in October 1967 when William J. Knight flew Mach 6.7 - hasn't been broken in 50+ years.

rtkwe 8y ago
It's a mix of things I think. First we haven't had a really big breakthrough in engine technology in a while and second there's no need to risk a person piloting these anymore because computers and remote control tech has gotten good enough.
- ProAm 8y ago
  Wouldnt the scramjet engines be a pretty big breakthrough?
  - dmoy 8y ago
    Scramjet still needs air though, doesn't it? Thus it has to fly lower, and maybe can't get as fast as a rocket engine. Scramjet planes are faster than other non-rocket planes I would imagine?
    - darkpuma 8y ago
      The SR-71 cruised at Mach 3.2. Scramjets have been demonstrated to do Mach >5, and theoretically might be capable of something between Mach 17 to Mach 25(!!!) Scramjets do need air, although something to consider is that the faster you go, the more air you get. So at high altitudes with very thin air, you can go faster to get more air. In fact you have to go faster (true airspeed) in thin air anyways even if your brought along liquid oxygen for your engine, because as the air thins your stall speed will go up. The whole thing is a complicated system of equations. Engine capabilities and/or critical mach number (for planes designed for subsonic flight, like the U-2) of the airframe set an upper limit on how fast you can go. Air density decreases with altitude, increasing the stall speed (according to true airspeed, not indicated airspeed.) But for a given true airspeed, with increased altitude the temperature of the air drops, consequently dropping the speed of sound, which reduces the mach number. In subsonic planes as altitude goes up the stall speed and critical mach number eventually pass each other, beyond which your plane can no longer fly. The point of that intersection is known as the 'coffin corner'. In planes designed for supersonic flight passing the critical mach number isn't a problem, but eventually you'll reach a point where the drag on the aircraft is so great that the engines simply don't have enough power to overcome it. Increasing altitude reduces drag as the air gets thinner, but that only works for so long. Air speed inside the engines needs to be considered too. The airspeed past the turbine blades needs to be such that you won't get compressor stall. When you discard the turbine requirement, that's where things start to get interesting. A ramjet has no turbines, it compresses the air using the intake geometry. At full speed the SR-71 was actually producing most of it's thrust with a ramjet effect, most of the air going into the engines was not going through the turbines. The difference between a ramjet and a scramjet is that in a ramjet, the air inside the engine becomes subsonic again for the burn, but in a scramjet the air inside the engine remains supersonic. Scramjets could go really fast.
    - NamTaf 8y ago
      Yes, scramjets are faster than other non-rocket planes. They have a lower bounds of approx. Mach 3, but then go up from there. The big challenge is basically making sure that you mix your fuel with the air, combust it fully, and extract the energy before it flies out the back of the engine. Scramjets are the engines capable of this at the highest speeds.
aristophenes 8y ago
Maybe because once you start going faster than that there isn't much point staying inside the atmosphere? If you want to count spacecraft that record has been shattered.
- siffland 8y ago
  It is like the land speed record. As soon as you get over a couple hundred miles per hour you might as well fly. So when you get to mach 6 you might as well be in space....
  - zik 8y ago
    And when you get to about mach 33 you might as well leave orbit.
- greglindahl 8y ago
  There’s a huge new interest in hypersonic gliders.
god_bless_texas 8y ago
How do you know?
pathikrit 8y ago
The speed record for a car over a kilometer has not been broken since 1937 [1] [1]: https://en.wikipedia.org/wiki/Mercedes-Benz_W125_Rekordwagen https://en.wikipedia.org/wiki/Mercedes-Benz_W125_Rekordwagen

ceejayoz 8y ago

"Plane" is a bit of a misnomer for the X-15, though. "Rocket with wings" is more accurate.

keymone 8y ago
Elon wouldn't approve.
darkpuma 8y ago
There are some (mostly Brazilians) who would disqualify the Wright Flyer as the first airplane on the grounds that it took off from a rail. Is the engine breathing air really an essential part of the "airplane" definition? Solar Impulse 2 didn't breath air either, yet wasn't it an airplane too? @DuskStar It's certainly a glider on reentry. Now, most speed records for planes are "in level flight" which would disqualify the shuttle during reentry. But if we ignore that it's interesting that the speed record for manned aircraft is held by a glider, and the speed records for RC aircraft are also held by gliders! https://www.youtube.com/watch?v=MoaWlKC3wIM https://www.youtube.com/watch?v=MoaWlKC3wIM
- DuskStar 8y ago
  Is the space shuttle a plane?
  - mehrdadn 8y ago
    I feel like a basic requirement for a plane would be that it can maintain its altitude, so no?
  - Anarch157a 8y ago
    The NASA Shuttle, no, the Soviet Buran, yes. As a Brazilian (see previous comments about the Wright Brothers), I consider that an airplane: * Is powered, otherwise, it's a glider; * Can maintain level flight, otherwise, it's just "Falling with style"; * Can take off on it's own, assistance (RATO, catapults) is allowed for short take-offs (like from a carrier); The Shuttle fails in all that in some point of the flight or another, Buran on the other hand, could be fitted with air breathing jet engines that allowed it to do all that.

quintin 8y ago

Man! Hacker News is so interesting with folks like you hanging around.

rurban 8y ago

There is a nice example now in popular culture of the problems of a X-15 in the beginning of the movie "First Man" with Neil Armstrong bouncing off the atmosphere in this rocketship. The other popular case, the only lost ship was also similar to the bad MCAS system in the Boeing 737max, the pilot forgot to turn off the problematic flight control system, and he didn't see the 90 yaw angle because he turned it off, so he raced straight down, and the control SW kept it that way.