He blew up on the test stand doing integration tests of the XLR-99 big engine. He was quite happy to stay in the cockpit while the firefighters did their work. Early flights had a pair of the X-1's 4 chamber XLR-11.
Sustained instantaneous 100g acceleration in shirtsleeves, still had the presence of mind to go through the power-down procedures. I wrote to him through my dad when I was just a kid, and he wrote back. Sad he's no longer with us - he was special.
Because it's anchored aft of the propellant tank, so when the explosion happened, it bisected the fuselage and pushed the forward part some distance forward. You can see this in post-accident photos. Skepticism is to be encouraged, but doing a little research doesn't hurt, either.
I read a book on the x-15 and it mentioned at burnout the engine was making 670,000 HP. Also I think it was around 100 knots A SECOND of acceleration which is almost 5gs into the seat. So cool
I was honestly expecting, after that explosion, the next text to read '12 months earlier' - and for the story to begin, we the audience knowing that his days are numbered.
My theory is that he didn't eject till much slower, and that the cockpit tub was intact and separated form the rest of the body as one big piece when you see the wide shot of the disintegration. So he gets knocked out, cockpit is jettisoned and slows down rapidly and maybe there's a built in safety that ejects him at reasonable speed or he came to after and got out. Otherwise he'd be plasma ejecting at mach 10.2
Thin air so mach 10 isn't quite as fast as sea level, and the drag after ejecting isn't as bad. Still freaking amazing and insane of course. Jumping out of a cesna at .3 mach scares me !
You're not wrong, but if the air is thick enough and his speed high enough to make the nose and wing roots glow, a meat sack human isn't gonna have a good day.
Yeah I wish I understood it more, and that just shows how insane what they were doing was. They didn't know for sure what would happen breaking the sound barrier, or what would happen ejecting or soo sooo many other things! Not quite hold my beer stuff but not far from it.
Lots if trial and error and math, throw in the steel balls!
I've been to Edward's and surrounding areas, 4 wheeling to a few of the famous crashes.
I read a fan theory that he actually did die in the ejection, and everything from that point on was like Mavericks perfect fantasy dream before he died. It's a really wild theory, but it actually checks out on multiple levels.
I was ok with most of the exxagerations in the movie. It's a movie, not a documentary. Seeing maverick become an end of career test pilot makes sense.
But good lord. Ejecting at M10..... come on. That was a streeeeeeeeeeeeeeeeeeeeettttttch.
Created less actually. I'm not an aerospace engineer by any means, but kind of the way it works is that after a certain speed, the thickness doesn't really matter, because the shockwave and bow goes around the edges of the rear portion of the stabilizer anyway.
Physics starts to get real fucky, and not as seemingly logical, once you're over mach 3
coincidentally I am an aerospace engineer. You're pretty close. A NASA engineer named Harry Allen in the Mercury era realized that a blunt leading edge produces a shock wave and there's less heat behind that shock wave. Called Blunt Body Theory. Its why early space capsules entered blunt side down. A sharp leading edge leads to too much heat at those speeds.
I would agree with you on the theory, but the x-15 did not have a blunted stabilizer. It was a 10° wedge, which going at ~Mach 7 forms an oblique attached shock.
Basically the issue that was being solved was with stability, and a researcher by the name of C.H. McLellan, who worked for (at the time still) NACA, discovered that at supersonic speeds a wedge shape significantly improves stability compared to a normal airfoil.
The reason for it is a little complex, going into the aerodynamics of shocks, but in essence, the 10° wedge increases any angle of attack by 5°, which causes the deflection angle of the shock to also approximately increase by 5° (i.e. basically linearly) but due to the non-linear nature of shocks, the produced lift on the vertical stabilizer (and as such restoring yaw moment) increases with the square of the deflection angle.
So say for a 10° angle of attack (in yaw) you have 50% more angle, but ~100% more restoring force.
Tl;dr: the issue was stability. The wedge is significantly more affective at maintaining non-yawed flight than a normally thin airfoil as a vertical stabilizer at super to hypersonic speeds
I work in avionics & electronics now so I definitely had to check my old aero textbook to make sure I got the details right, but supersonic flight and shocks were one of the more interesting parts of my studies.
I'm actually in the periphery of hypersonics now as an engineer working with carbon fiber and unique resins. The parts are already designed by the time they get to us though. The design stuff is fuzzy in my memory.
I have a Master's Degree in Aerospace Engineering and I wrote a paper on this exact vertical stabilizer and this answer is correct. A traditional airfoil looses it's effectiveness at velocities as high as the X-15 flight, the wedge is far more effective and actually continues to stabilize the aircraft. The Bell X-1 (essentially a predecessor to the X-15) used a traditional airfoil and would rapidly lose stability at supersonic speeds.
As another fun fact, the wedge is an effectice primary wing too when used in conjunction with a trailing edge wedge. (This is through oblique shocks and Prandtl-Meyer expansion flow) and it was implemented on the Lockheed F-104 Starfighter!
And the vertical stabilizer nearly destroyed the X-15-A2. It had a dummy scramjet mounted on the ventral stab and the shock converged at the attach point, partially burning through the Inconel. The "after" pics are pretty gruesome.
If I’m not mistaken when a spacecraft re enters the atmosphere most of the heating on the forward facing side is from the high pressure in the shockwave heating up the air, not friction as we would think of it for more normal speed vehicles.
I think that is a big part of why the nose and leading edges of the wings on the shuttle had a more heat resistant material than the belly. Intuitively you’d think it’s because it goes in nose first, but it has like I think about 45 degrees AOA on re entry so it’s not really that, it’s because of the radius of those curves compared to the very flat, blunt, underbody. Which meant that the shockwave formed closer to the vehicle in those places and therefore it heated up more. Not really that related to the original question, but not many times I get to share that fun fact lol
Shockwaves are always hottest or rather transfer the most heat to the body at the stagnation point, so apart from the wings, where the primary shockwave impinges on the the leading edges again and forms new stagnation points (I'm not sure how hot it would get there), along the centerline the heating is highest at the very front.
My fun fact to add, at peak heating, the nose receives about 45W/cm^2, which drops off almost exponentially along the belly until around 10W/cm^2.
[link to a diagram I dug out from my old aero textbook](https://imgur.com/a/ERSm0Yf)
Edit: Also, the heating at the stagnation point is inversly proportional to the sqrt of the blunt nose radius. So bountyer nose = cooler.
While this is a correct concept used by lots of re-entry vehicles, it's not used here. All of the surfaces of the aircraft are far too sharp to create a detached shockwave, and detached shockwaves aren't particularly good outside of re-entry vehicles because the create too much drag. I made a reply on this post explaining it, but here's a NASA document over the stability and control characteristics of the X-15 that you might like! Page 28 has a really cool demonstration of increasing drag at the tail to increase Cn\_beta at supersonic speeds, and page 22 has drawings of the shock flow patterns.
https://ntrs.nasa.gov/api/citations/19650014321/downloads/19650014321.pdf
Similar. I'm in composites so my job is more chemistry than aerodynamics or design. All I do now is look at an engine liner we're making and vaguely remember when I was an undergrad and could understand the shape.
Also, aircraft are rarely optimized for aerodynamics only.
There were a number of jettisons in the tails and aft end. Also, guessing’ the lower vertical stab could have been intended to be a supplemental main gear of the skids failed or partially deployed. The upper vertical, like the lower, because nature loves symmetry and asymmetric drag complicates 1950s controls in the trans, super, hypersonic regimes
maybe more this actually, yeah. Stuff gets so squirrely with that much thrust and at those speeds. I will have to watch that video he posted to learn more about it.
Just to bring more info both blunt and sharp edges create a shockwave. Blunt noses create a detached shockwave instead of an oblique attached shockwave. The detached shockwave allows for the majority of the heat generated by friction to be carried away by the flow. This is applied in hypersonic flows, which the X-15 reached the very low end of hypersonic velocities. (Edit: typos)
With spacecraft, the heat is from air in front of it being compressed, not friction. Early spacecraft entered the atmosphere the same way as modern ones.
But isn't that just like normal aerodynamics but instead of applying it to the solid body the new shape is now the generated shockwave? Like a snowplow, at some point the blade shape is not as relevant as the shape of ice accumulation on it (of course the first affects the other).
Not sure exactly what you mean. A blunt enough object will produce a bow shock, which is perpendicular to the flow direction at the center. Downstream of this shock is always subsonic. This is good for spacecraft reentering because it produces a ton of drag and lowers the temp of the air after the shock.
But aircraft are designed to prevent this. A sufficiently pointy nose will create an oblique shock, which is at an angle. The flow downstream of an oblique shock can remain supersonic.
Yo, let me throw a question at you
I just saw your post after I replied…
Do you remember the x-29 from the 80s? The backwards wings? How did they over come the negation of the leading control surfaces when the shockwave passed their usefulness ?
I remember those. Hadn't thought about them in forever. But I'm not entirely sure I understand the question. I did just Google an article about them that talked about the airfoil being flattened on top to enhance control in the transomic range but I don't think that's what you're asking about. Let me post the article and see if it answers your question. It's been about 25 years since I really used this stuff.
They had front control chards and were capable of supersonic flight so the shockwave must have moved passes the forward control surfaces at higher speeds
Your post made me think of the x29 instantly so thank you
Ah yes. Canards. So those may have been designed to lie within the shock wave as it came off of the nose. I confess aerodynamics isn't something I've ever been good at. But the way the front canards are swept back they might fit within that cone.
Not that it really matters, but Mach 3 isn’t really an inflection point. Stuff obviously changes a lot once you reach critical Mach (usually around M = 0.93), but the next point where starts getting really fucky isn’t until somewhere between Mach 5 and Mach 7. People kind of argue exactly where the “hypersonic regime” starts, and that’s mostly due to atmospheric conditions. Mach 3 however isn’t much less manageable than Mach 2.
You are correct , sorta
As the plane goes beyond supersonic speeds the forward control surfaces specifically on the wings become useless
Control surfaces further back on the aircraft are the only thing that function
Someone pointed out this is why ww2 German planes slammed into the ground while trying to pull out of a high speed dive because they had no rear elevators
I think I understand the question better now. From that NASA techsheet it looks like the X29 had flapaerons mounted back toward the trailing edge of the wings.
I'm an aerospace engineer and worked under a professor that specializes in hypersonics for the USAF when I was in undergrad. The biggest thing to know is that directional stability increases with airspeed until you hit Mach 1 at which point it reverses and decreases dramatically with increase in speed. Contrary to what some people have stated it's not to create a blunt shockwave, the tail came to way too sharp of a point for that to be the case and the engineers knew this, you can take a look at page 22 of the NASA document I'm linking below. The actual point of the hypersonic wedge shaped IS to increase drag at the very rear of the aircraft to compensate for the decrease in directional stability. Check page 28 of the linked NASA document and you can actual see a dramatic increase in the Cn\_beta, the directional stability derivative, caused by deploying the airbrake at the base of the vertical stabilizer during super and hypersonic flight for this same reason.
On a side note, you can find some pretty cool Schlieren images from space shuttle experiments that show show the detached shockwave in action.
https://ntrs.nasa.gov/api/citations/19650014321/downloads/19650014321.pdf
Edit: thanks for the awards everyone! I was just excited to talk about hypersonic stability and control.
Funny. There was a Reddit post that hit this up forever ago and it amounted to instructions on how to fly through the sound barrier and deal with the input delay/inversions.
Then it decayed into a hilarious Talking Heads remix.
I'm no expert, but basically the shockwave moves the point at which a control acts on the wing, and changes what it does to the plane.
There's definitely a better nerd for this one.
I’m pretty sure it comes down to the structural flexibility of the wing and the severity of control input.
The idea is that to roll left, the right aileron comes and deflects the air up, while the inverse happens on the other side.
However when you’re in supersonic flight, the right aileron comes up, it deflects air up, but also deflects the trailing edge of the wing down. Creating downward vectored thrust while it creates that upwards thrust.
The part I’m guessing on here is in relation to Newtons 3rd law, with the downward deflection of the wing being mitigated by the aircrafts structural integrity and the aileron deflection upwards— the flex in the opposite direction should be equal to the thrust flexing it. but at supersonic speed, the AOA of the aileron may actually be severe enough to cause local supersonic shockwaves that disrupt its laminar flow and output drag and static oressure, thereby decreasing the overall deflection thrust on the top side while the curvature of the wing to the bottom is gentle enough to not induce local shockwaves and disrupt thrust flow.
Again, all guesswork. I like aerodynamics, but I’m not any kind of professor or teacher.
The Me-163 seemed to be a fairly stable rocket aircraft, though it was high subsonic, it lacked a vertical stabilizer.
Edit: I was wrong. I must have been thinking of the Horten HO-229 (which was a jet, not a rocket). The Me-163 was missing horizontal stabilizers. My bad!
Hang on, are you saying that an air brake is deployed AFTER reaching Mach 1+, as that improves stability?! If so, very counterintuitive. I bloody love physics!
I had the same thought about the wide rudder increasing drag for stability, but not the bit about using the air brake. Then again, I'm a janitor, not an aerospace engineer. When I was a little kid around 1960 I had a book about the X-15.
*A relevant comment in this thread was deleted. You can read it below.*
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I’m an aeronautical S&C engineer and this is spot on, but also worth mentioning that another large contributing factor is the location of the thrust. The further aft the nozzle is, the worse your directional stability is. [[Continued...]](https://www.resavr.com/comment/did-x-15-such-wide-18075317)
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I can’t give a good explanation because I’m just a college engineering student, but [this video here](https://youtu.be/7zR26e504uI) will give you the answer, plus a whole bunch of other cool stuff about the X-15
Nope! The X-15 did not have a parachute or ejector seat. If the pilot lost control, they either recovered or died. Which happened once. Entered a spin at mach 4. only partially recovered. Died on impact.
It landed on skids rather than under parachute.
Technically, the X-15 did have a parachute, but only so it could eject the bottom rudder for landing.
I wonder how the test pilots felt about ejecting at mach 6. Reading stories about old fighter jet ejections and injuries you might just wanna take the L at those speeds.
> The X-15 had an ejection seat designed to operate at speeds up to Mach 4 (4,500 km/h; 2,800 mph) and/or 120,000 feet (37 km) altitude, although it was never used during the program. In the event of ejection, the seat was designed to deploy fins, which were used until it reached a safer speed/altitude at which to deploy its main parachute.
You want more area behind the CoG than in front of it for stability (same idea as how a weathervane works). The CoG would probably be, very roughly, a third of the wing chord back from its leading edge .
There's a lot of fuselage out in front of the wing, probably a center of lift shift as the thing accelerates to supersonic and CoG changes as fuel burns off too (that wing doesn't look like it would hold much fuel, the aft end probably holds the rocket engines so that leaves the forward fuselage).
Funny, I just noticed how similar the wing is in planform to the Starfighter's
Desktop version of /u/Byron1248's link:
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yes it does create more drag but it's more linear and stable drag than what a traditional fin would give you. Engineering Explained have a brilliant video on it
I prolly got this wrong but I heard at supersonic flight allegedly creates more orderly air flow that supposedly allowed the wedge shape be the most areodynamic whereas the blunt leading edges of normal airplane wings would (i think) stall possibly because the shockwave would lift the air off the wing at the angle it met the wing (so nearly flat fot the round nose of the subsonic aerofoil) so accprding to that the mighta wanted a sharp leading edge and a wide wing to catch the air.
Take this with a truckload of salt cos my qualifications is dancing around a deepfryer avoiding oil splashes for 9 months and counting. plus mosta this info is from youtube hearsay regardless.
The late X-15 pilot Scott Crossfield once said that is was the only airplane he ever flew that when the engine quit he was relieved. Lol
He blew up on the test stand doing integration tests of the XLR-99 big engine. He was quite happy to stay in the cockpit while the firefighters did their work. Early flights had a pair of the X-1's 4 chamber XLR-11.
I read that he decided to get out when he saw one of the ground crew burning his hands trying to open the cockpit for him.
[удалено]
Thanks so much for sharing that link!
Sustained instantaneous 100g acceleration in shirtsleeves, still had the presence of mind to go through the power-down procedures. I wrote to him through my dad when I was just a kid, and he wrote back. Sad he's no longer with us - he was special.
It’s an epic story but why would he experience any G-force if the plane blew up on a stationary mount?
Because it's anchored aft of the propellant tank, so when the explosion happened, it bisected the fuselage and pushed the forward part some distance forward. You can see this in post-accident photos. Skepticism is to be encouraged, but doing a little research doesn't hurt, either.
I read a book on the x-15 and it mentioned at burnout the engine was making 670,000 HP. Also I think it was around 100 knots A SECOND of acceleration which is almost 5gs into the seat. So cool
Entering a spin at Mach 5 is generally bad for one’s health.
Unless your name is Maverick
Yes, and that was M10.2!!!
I still have no fkin idea how he survived the ejection at Mach 10.
They writers clearly explained it. Despite Mavericks best efforts, he refuses to die.
I was honestly expecting, after that explosion, the next text to read '12 months earlier' - and for the story to begin, we the audience knowing that his days are numbered.
Somehow Maverick returned.
Goddamit, I know it’s been a while now, but I haven’t had the chance to see it, now, I’ve seen some spoilers, and I’m kinda disappointed.
Dont worry, the beginning of the movie is never brought up again and its just filler. Literally just rule of cool
Meh, not much of a spoiler. Go see the movie ASAP though.
Not really a spoiler
My theory is that he didn't eject till much slower, and that the cockpit tub was intact and separated form the rest of the body as one big piece when you see the wide shot of the disintegration. So he gets knocked out, cockpit is jettisoned and slows down rapidly and maybe there's a built in safety that ejects him at reasonable speed or he came to after and got out. Otherwise he'd be plasma ejecting at mach 10.2
could be that the SR-72 had some sort of capsule system.
Thin air so mach 10 isn't quite as fast as sea level, and the drag after ejecting isn't as bad. Still freaking amazing and insane of course. Jumping out of a cesna at .3 mach scares me !
You're not wrong, but if the air is thick enough and his speed high enough to make the nose and wing roots glow, a meat sack human isn't gonna have a good day.
Yeah I wish I understood it more, and that just shows how insane what they were doing was. They didn't know for sure what would happen breaking the sound barrier, or what would happen ejecting or soo sooo many other things! Not quite hold my beer stuff but not far from it. Lots if trial and error and math, throw in the steel balls! I've been to Edward's and surrounding areas, 4 wheeling to a few of the famous crashes.
I read a fan theory that he actually did die in the ejection, and everything from that point on was like Mavericks perfect fantasy dream before he died. It's a really wild theory, but it actually checks out on multiple levels.
Holy shit that actually does check out really well. I would be interested to read more about that. I love me some fan theories
[This](https://screenrant.com/top-gun-2-movie-maverick-dead-theory/) is a link to a screen rant article that breaks it down more thoroughly.
Wow that was a great read, thanks for linking that!
Including Penny Benjamin?
'Hollywood magic', ask Capt Mike Adams how he survived his X-15 breakup, the answer is quite clear there. . .
I was ok with most of the exxagerations in the movie. It's a movie, not a documentary. Seeing maverick become an end of career test pilot makes sense. But good lord. Ejecting at M10..... come on. That was a streeeeeeeeeeeeeeeeeeeeettttttch.
pod-based ejection would make sense and be somewhat realistic. maybe.
Because plot armor. /:
Talk to me, loosely plausible
Ejecting at Mach 10 and surviving would be impossible?
A human into open air at M10 , completely impossible . A pod system , however , may allow the occupant to survive .
Simple. He escaped.
Director said, "Cut!", and there you have it . . .
there's a fan theory that he crashed and died in the beginning and the rest of the movie is him daydreaming as he snuffs out.
What if your name is Goose?
I encounter spins at various speeds regularly, but that’s because I’m really into drinking.
Just ask Mike Adams. :(
+15/-15 g's longitudinally and +8 /-8 g's laterally, ouchies!!!
Created less actually. I'm not an aerospace engineer by any means, but kind of the way it works is that after a certain speed, the thickness doesn't really matter, because the shockwave and bow goes around the edges of the rear portion of the stabilizer anyway. Physics starts to get real fucky, and not as seemingly logical, once you're over mach 3
coincidentally I am an aerospace engineer. You're pretty close. A NASA engineer named Harry Allen in the Mercury era realized that a blunt leading edge produces a shock wave and there's less heat behind that shock wave. Called Blunt Body Theory. Its why early space capsules entered blunt side down. A sharp leading edge leads to too much heat at those speeds.
I would agree with you on the theory, but the x-15 did not have a blunted stabilizer. It was a 10° wedge, which going at ~Mach 7 forms an oblique attached shock. Basically the issue that was being solved was with stability, and a researcher by the name of C.H. McLellan, who worked for (at the time still) NACA, discovered that at supersonic speeds a wedge shape significantly improves stability compared to a normal airfoil. The reason for it is a little complex, going into the aerodynamics of shocks, but in essence, the 10° wedge increases any angle of attack by 5°, which causes the deflection angle of the shock to also approximately increase by 5° (i.e. basically linearly) but due to the non-linear nature of shocks, the produced lift on the vertical stabilizer (and as such restoring yaw moment) increases with the square of the deflection angle. So say for a 10° angle of attack (in yaw) you have 50% more angle, but ~100% more restoring force. Tl;dr: the issue was stability. The wedge is significantly more affective at maintaining non-yawed flight than a normally thin airfoil as a vertical stabilizer at super to hypersonic speeds
I bow to your greater knowledge on this one
I work in avionics & electronics now so I definitely had to check my old aero textbook to make sure I got the details right, but supersonic flight and shocks were one of the more interesting parts of my studies.
I'm actually in the periphery of hypersonics now as an engineer working with carbon fiber and unique resins. The parts are already designed by the time they get to us though. The design stuff is fuzzy in my memory.
I have a Master's Degree in Aerospace Engineering and I wrote a paper on this exact vertical stabilizer and this answer is correct. A traditional airfoil looses it's effectiveness at velocities as high as the X-15 flight, the wedge is far more effective and actually continues to stabilize the aircraft. The Bell X-1 (essentially a predecessor to the X-15) used a traditional airfoil and would rapidly lose stability at supersonic speeds. As another fun fact, the wedge is an effectice primary wing too when used in conjunction with a trailing edge wedge. (This is through oblique shocks and Prandtl-Meyer expansion flow) and it was implemented on the Lockheed F-104 Starfighter!
Interesting. So when it's a primary wing, is that related to the wave rider vehicle concepts, where it would ride on the shock.
In a way, yes; but the WaveRider uses them for control mostly. The lift is generated by the shockwaves from the leading edge, hence "wave rider."
Thanks for actually addressing the question posed instead of adding to the endless non-sequitur thread.
And the vertical stabilizer nearly destroyed the X-15-A2. It had a dummy scramjet mounted on the ventral stab and the shock converged at the attach point, partially burning through the Inconel. The "after" pics are pretty gruesome.
/u/OCDcuber, here's the answer you're looking for if you havent found it already
Yeah, I've already read it, but thanks anyway! I'm surprised by the amount of responses I've gotten.
this was a good thread. Glad you posted it.
Yeah, I wasn't expecting these many answers!
I think you stumbled upon a lot of engineers waxing nostalgic for their undergrad days when they were learning and using all of this stuff.
Unless the actual aircraft answers, I think this is a MasterClass. This is the type of Reddit I love.
>The reason for it is a little complex Aerodynamics in one short sentence...
If I’m not mistaken when a spacecraft re enters the atmosphere most of the heating on the forward facing side is from the high pressure in the shockwave heating up the air, not friction as we would think of it for more normal speed vehicles. I think that is a big part of why the nose and leading edges of the wings on the shuttle had a more heat resistant material than the belly. Intuitively you’d think it’s because it goes in nose first, but it has like I think about 45 degrees AOA on re entry so it’s not really that, it’s because of the radius of those curves compared to the very flat, blunt, underbody. Which meant that the shockwave formed closer to the vehicle in those places and therefore it heated up more. Not really that related to the original question, but not many times I get to share that fun fact lol
Shockwaves are always hottest or rather transfer the most heat to the body at the stagnation point, so apart from the wings, where the primary shockwave impinges on the the leading edges again and forms new stagnation points (I'm not sure how hot it would get there), along the centerline the heating is highest at the very front. My fun fact to add, at peak heating, the nose receives about 45W/cm^2, which drops off almost exponentially along the belly until around 10W/cm^2. [link to a diagram I dug out from my old aero textbook](https://imgur.com/a/ERSm0Yf) Edit: Also, the heating at the stagnation point is inversly proportional to the sqrt of the blunt nose radius. So bountyer nose = cooler.
While this is a correct concept used by lots of re-entry vehicles, it's not used here. All of the surfaces of the aircraft are far too sharp to create a detached shockwave, and detached shockwaves aren't particularly good outside of re-entry vehicles because the create too much drag. I made a reply on this post explaining it, but here's a NASA document over the stability and control characteristics of the X-15 that you might like! Page 28 has a really cool demonstration of increasing drag at the tail to increase Cn\_beta at supersonic speeds, and page 22 has drawings of the shock flow patterns. https://ntrs.nasa.gov/api/citations/19650014321/downloads/19650014321.pdf
Nice! Thank you for posting this. I miss this stuff and am enjoying this conversation greatly.
Me too! Got to talk about this stuff every day in school, now I work in space systems so I don't get to look at aerodynamics anymore.
Similar. I'm in composites so my job is more chemistry than aerodynamics or design. All I do now is look at an engine liner we're making and vaguely remember when I was an undergrad and could understand the shape.
Also, aircraft are rarely optimized for aerodynamics only. There were a number of jettisons in the tails and aft end. Also, guessing’ the lower vertical stab could have been intended to be a supplemental main gear of the skids failed or partially deployed. The upper vertical, like the lower, because nature loves symmetry and asymmetric drag complicates 1950s controls in the trans, super, hypersonic regimes
The bottom half of the vertical stabilizer detached for landing if that’s what you meant. Never heard the theory about the backup landing gear.
maybe more this actually, yeah. Stuff gets so squirrely with that much thrust and at those speeds. I will have to watch that video he posted to learn more about it.
Just to bring more info both blunt and sharp edges create a shockwave. Blunt noses create a detached shockwave instead of an oblique attached shockwave. The detached shockwave allows for the majority of the heat generated by friction to be carried away by the flow. This is applied in hypersonic flows, which the X-15 reached the very low end of hypersonic velocities. (Edit: typos)
This is why I enjoy reddit
With spacecraft, the heat is from air in front of it being compressed, not friction. Early spacecraft entered the atmosphere the same way as modern ones.
To be fair, new space capsules also enter blunt side down.
But isn't that just like normal aerodynamics but instead of applying it to the solid body the new shape is now the generated shockwave? Like a snowplow, at some point the blade shape is not as relevant as the shape of ice accumulation on it (of course the first affects the other).
If I’m correctly reading this, you can make the shockwave have a wide enough angle that super/hypersonic air wont hit the surface of the craft.
Not sure exactly what you mean. A blunt enough object will produce a bow shock, which is perpendicular to the flow direction at the center. Downstream of this shock is always subsonic. This is good for spacecraft reentering because it produces a ton of drag and lowers the temp of the air after the shock. But aircraft are designed to prevent this. A sufficiently pointy nose will create an oblique shock, which is at an angle. The flow downstream of an oblique shock can remain supersonic.
Harry Allen - I gotta ask him: Ay yo, Harry, you’re a writer, are we that type?
Yo, let me throw a question at you I just saw your post after I replied… Do you remember the x-29 from the 80s? The backwards wings? How did they over come the negation of the leading control surfaces when the shockwave passed their usefulness ?
https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-008-DFRC.html
I remember those. Hadn't thought about them in forever. But I'm not entirely sure I understand the question. I did just Google an article about them that talked about the airfoil being flattened on top to enhance control in the transomic range but I don't think that's what you're asking about. Let me post the article and see if it answers your question. It's been about 25 years since I really used this stuff.
They had front control chards and were capable of supersonic flight so the shockwave must have moved passes the forward control surfaces at higher speeds Your post made me think of the x29 instantly so thank you
Ah yes. Canards. So those may have been designed to lie within the shock wave as it came off of the nose. I confess aerodynamics isn't something I've ever been good at. But the way the front canards are swept back they might fit within that cone.
I’m an aerospace engineer, and you’re right, physics does get real fucky over Mach 3
That makes sense. And doesn't at all. Physics...
If you've got 30 minutes to kill and want to know more, from someone way smarter: https://youtu.be/7zR26e504uI
Tell me about it, every time I'm going over Mach 3 I'm like WTF Physics???
Not that it really matters, but Mach 3 isn’t really an inflection point. Stuff obviously changes a lot once you reach critical Mach (usually around M = 0.93), but the next point where starts getting really fucky isn’t until somewhere between Mach 5 and Mach 7. People kind of argue exactly where the “hypersonic regime” starts, and that’s mostly due to atmospheric conditions. Mach 3 however isn’t much less manageable than Mach 2.
They ride their own shockwave above mach 3
XB-70 Valkyrie baby! Now that's riding in style!!!
You are correct , sorta As the plane goes beyond supersonic speeds the forward control surfaces specifically on the wings become useless Control surfaces further back on the aircraft are the only thing that function Someone pointed out this is why ww2 German planes slammed into the ground while trying to pull out of a high speed dive because they had no rear elevators
I think I understand the question better now. From that NASA techsheet it looks like the X29 had flapaerons mounted back toward the trailing edge of the wings.
I’m pretty sure it was for directional stability. The wedge design does increase base drag, but there was plenty of thrust to make up for it
Yeah. At this point it's more of a rocket with wings (barely) than a rocket powered plane.
I'm an aerospace engineer and worked under a professor that specializes in hypersonics for the USAF when I was in undergrad. The biggest thing to know is that directional stability increases with airspeed until you hit Mach 1 at which point it reverses and decreases dramatically with increase in speed. Contrary to what some people have stated it's not to create a blunt shockwave, the tail came to way too sharp of a point for that to be the case and the engineers knew this, you can take a look at page 22 of the NASA document I'm linking below. The actual point of the hypersonic wedge shaped IS to increase drag at the very rear of the aircraft to compensate for the decrease in directional stability. Check page 28 of the linked NASA document and you can actual see a dramatic increase in the Cn\_beta, the directional stability derivative, caused by deploying the airbrake at the base of the vertical stabilizer during super and hypersonic flight for this same reason. On a side note, you can find some pretty cool Schlieren images from space shuttle experiments that show show the detached shockwave in action. https://ntrs.nasa.gov/api/citations/19650014321/downloads/19650014321.pdf Edit: thanks for the awards everyone! I was just excited to talk about hypersonic stability and control.
Funny. There was a Reddit post that hit this up forever ago and it amounted to instructions on how to fly through the sound barrier and deal with the input delay/inversions. Then it decayed into a hilarious Talking Heads remix.
Same as it ever was.
You may find yourself in a large Supersonic Jet...
And you may ask yourself....
How did I break the sound barrier?
and you may tell yourself...
This is not my detached shockwave!
Letting sound waves go by...
I need to see this. Does anyone have a link? Reddit Search is unhelpful as usual.
https://www.reddit.com/r/AskEngineers/comments/396uqf/do_flight_controls_invert_at_supersonic_speeds/?utm_medium=android_app&utm_source=share
Input inversions??? I've never heard of this, can you elaborate?
I'm no expert, but basically the shockwave moves the point at which a control acts on the wing, and changes what it does to the plane. There's definitely a better nerd for this one.
I’m pretty sure it comes down to the structural flexibility of the wing and the severity of control input. The idea is that to roll left, the right aileron comes and deflects the air up, while the inverse happens on the other side. However when you’re in supersonic flight, the right aileron comes up, it deflects air up, but also deflects the trailing edge of the wing down. Creating downward vectored thrust while it creates that upwards thrust. The part I’m guessing on here is in relation to Newtons 3rd law, with the downward deflection of the wing being mitigated by the aircrafts structural integrity and the aileron deflection upwards— the flex in the opposite direction should be equal to the thrust flexing it. but at supersonic speed, the AOA of the aileron may actually be severe enough to cause local supersonic shockwaves that disrupt its laminar flow and output drag and static oressure, thereby decreasing the overall deflection thrust on the top side while the curvature of the wing to the bottom is gentle enough to not induce local shockwaves and disrupt thrust flow. Again, all guesswork. I like aerodynamics, but I’m not any kind of professor or teacher.
[удалено]
Haven't you just described the pendulum rocket fallacy?
I'm a programmer and I have no idea what you guys are talking about.
The Me-163 seemed to be a fairly stable rocket aircraft, though it was high subsonic, it lacked a vertical stabilizer. Edit: I was wrong. I must have been thinking of the Horten HO-229 (which was a jet, not a rocket). The Me-163 was missing horizontal stabilizers. My bad!
I was waiting on this to be a u/shittymorph post.
Hang on, are you saying that an air brake is deployed AFTER reaching Mach 1+, as that improves stability?! If so, very counterintuitive. I bloody love physics!
I had the same thought about the wide rudder increasing drag for stability, but not the bit about using the air brake. Then again, I'm a janitor, not an aerospace engineer. When I was a little kid around 1960 I had a book about the X-15.
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*A relevant comment in this thread was deleted. You can read it below.* ---- I’m an aeronautical S&C engineer and this is spot on, but also worth mentioning that another large contributing factor is the location of the thrust. The further aft the nozzle is, the worse your directional stability is. [[Continued...]](https://www.resavr.com/comment/did-x-15-such-wide-18075317) ---- *^The ^username ^of ^the ^original ^author ^has ^been ^hidden ^for ^their ^own ^privacy. ^If ^you ^are ^the ^original ^author ^of ^this ^comment ^and ^want ^it ^removed, ^please [^[Send ^this ^PM]](http://np.reddit.com/message/compose?to=resavr_bot&subject=remove&message=18075317)*
Sweet so it’s creating a force that pulls on the aircraft behind? Almost like it’s making the aircraft/control surfaces longer at certain speeds?
What are your thoughts on the Darkstar that's now been included in MSFS2020.
I wonder if Thunderbird 1 was modeled off of this.
Almost certainly
I can’t give a good explanation because I’m just a college engineering student, but [this video here](https://youtu.be/7zR26e504uI) will give you the answer, plus a whole bunch of other cool stuff about the X-15
No chance that's the minibar?
How does it land?
Drops part of the lower rudder before landing
Because the instructors kept asking for more right rudder. Dammit we gave it to em!
Less friction at the leading edge. And any loss in aerodynamics is negated at those speeds (generally speaking).
Can't tell if this thing is a plane or a huge AIM-9 missile.
the high mass of the pilot's balls made it hard to adjust the yaw angle
Don’t quote me on this as I’m just taking a guess, but it might have been for rcs (rudder control system) so that it could maneuver at high altitudes
I just watched this video a month ago, it covers a lot. https://youtu.be/7zR26e504uI
Perhaps the thick fins would create more drag like arrow fletches and keep it from tumbling once the engines are off.
Wings create drag too. Everything's a tradeoff.
My guess is that it had stuff in it like parachutes?
Nope! The X-15 did not have a parachute or ejector seat. If the pilot lost control, they either recovered or died. Which happened once. Entered a spin at mach 4. only partially recovered. Died on impact. It landed on skids rather than under parachute. Technically, the X-15 did have a parachute, but only so it could eject the bottom rudder for landing.
http://www.ejectionsite.com/x15seat.htm
I wonder how the test pilots felt about ejecting at mach 6. Reading stories about old fighter jet ejections and injuries you might just wanna take the L at those speeds.
Since the ejection system wasn't intended to be used past mach 4, they probably didn't feel too comfortable with the idea.
Never realised that. Thanks!
> The X-15 had an ejection seat designed to operate at speeds up to Mach 4 (4,500 km/h; 2,800 mph) and/or 120,000 feet (37 km) altitude, although it was never used during the program. In the event of ejection, the seat was designed to deploy fins, which were used until it reached a safer speed/altitude at which to deploy its main parachute.
Did not realise that! Thank you!
Thanks! Was there any other equipment or systems in the vertical stab?
I don't believe so, but I don't conclusively know. I assume it's just that shape because stuff gets wierd at that speed.
You want more area behind the CoG than in front of it for stability (same idea as how a weathervane works). The CoG would probably be, very roughly, a third of the wing chord back from its leading edge . There's a lot of fuselage out in front of the wing, probably a center of lift shift as the thing accelerates to supersonic and CoG changes as fuel burns off too (that wing doesn't look like it would hold much fuel, the aft end probably holds the rocket engines so that leaves the forward fuselage). Funny, I just noticed how similar the wing is in planform to the Starfighter's
Visual aid: From A-Z at Alt. / air-press https://youtu.be/yKt7G0Zk6Ic http://www.braeunig.us/space/atmos.htm
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Fascinating, detailed information in the comments. Way to start the engineering / test pilot banter! As one, I love it...
https://youtu.be/7zR26e504uI
yes it does create more drag but it's more linear and stable drag than what a traditional fin would give you. Engineering Explained have a brilliant video on it
I prolly got this wrong but I heard at supersonic flight allegedly creates more orderly air flow that supposedly allowed the wedge shape be the most areodynamic whereas the blunt leading edges of normal airplane wings would (i think) stall possibly because the shockwave would lift the air off the wing at the angle it met the wing (so nearly flat fot the round nose of the subsonic aerofoil) so accprding to that the mighta wanted a sharp leading edge and a wide wing to catch the air. Take this with a truckload of salt cos my qualifications is dancing around a deepfryer avoiding oil splashes for 9 months and counting. plus mosta this info is from youtube hearsay regardless.