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What it was like to fly the baddest airplane (arstechnica.com)
188 points by rbanffy 28 days ago | hide | past | web | favorite | 67 comments

Definitely worth your trip to Dayton Ohio at the National Museum of the Air Force to see this plane in person. It’s on the floor so you can see it up close. I believe the other one at the Air and Space Museum is hung above.

The Air Force Museum is just an all around one of the best aviation museums to go anyway.

Yup. The Air Force Museum is probably one of the best aviation museums anywhere in the world, perhaps second only to the Smithsonian. So many unique, one of a kind aircraft are preserved there.

If you're an aviation geek who likes to linger and read, plan on two days. I went a couple years ago. I got there when they opened and spent the whole day there. I had to blitz through the last hanger because they were closing and I didn't even get to see any of the outdoors exhibits or a movie.

Very true. We went last year, happened to be on the day the Memphis Belle exhibit opened. We have videos of the WWII era planes flying overhead. Then they landed and we took a bus out to the end of the runway/taxiway and could get inside the planes. It was awesome.

In an amazing stroke of luck, one of the VC-25s was doing training that day too. So we have videos of the WWII planes flying by, then pan over to a VC-25 in the same shot. Just an amazing combination to see in the air at the same time.

If you are ever in or near Tucson, AZ, the Pima Air & Space Museum (https://pimaair.org/) has a full-scale X-15 mock-up as well as one of the B-52s used for launching the things. You can coordinate this with a bus tour of the "bone yard" at nearby Davis-Monthan AFB. Note: the bus tour requires advance reservation & security check, I believe.

Just been to Air and Space Museum recently, as it happens. There's a walkway right next to the X-15, so you can actually see it from very up close.

I was just there a few days ago. It really is an amazing museum.

They have a few hangars full of airplanes, space ships, satellites, rockets, fighter jets, drones, etc.

Yea, awesome museum (I visited when I was in Dayton on business a couple years ago), it compares well to Nat'l Air and Space (including Udvar-Hazy in NoVA). I actually enjoyed it more due to it being far less crowded :)

I haven't been there in several years, but Norton Sales[1], an aerospace surplus shop in North Hollywood, used to have a couple X-15 engines for sale[2][3].

1. http://www.nortonsalesinc.com 2. https://www.flickr.com/photos/wallofhair/4595764150/in/photo... 3. http://www.wendingourway.com/space/norton.htm

wow, thanks for sharing. A couple years ago I was curious about where to find surplus, old/retro gauges, panels, etc... a didn't find much. I had the idea to build some retro cockpit-like setup into a tree house for my kids. There's no pricing on their web-page, but this would be a treasure trove for something like that.

"Hey bud, we've got a new airplane for you to fly. Well, it's not really an airplane, its really more like a cockpit strapped to a rocket engine. Actually, it's more like a tiny cabin bolted to a super soaker of chemicals so explosive that we didn't bother to include an igniter.

It has some tiny wings for you to control it but we couldn't include any landing gear so we gave it some flimsy skids instead. We were hoping you would at least find them cute even if they aren't particularly useful.

We included a diaper in your pressure suit that will be helpful if you get scared. You also don't have to worry about taking off, but when you try to land please make sure that you descend at the right angle so that you don't accidentally take a joy ride to Alpha Centauri.

Please be careful with our flying bomb with tiny wings and cute little skids. While it may be just a cockpit strapped to a flamethrower, it still cost $999 million to build, so no dents, please and thank you."

Best regards,

Uncle Sam

fyi the first 20-so flights of the X-15 burned LOX/alcohol, similar to the X-1 or V-2. Later flights burned LOX/ammonia. I'm not sure about the ammonia, but LOX/alcohol is not hypergolic.

The X-15 has always intrigued me, even more so than the SR-71 as a kid, when I found out that it could travel at nearly Mach 7. That is more than twice as fast as a standard .308 bullet muzzle velocity.

Wow, see now that made the speed more graspable for me (hunt with a .308), cheers mate!

> Three decades later, he still misses it like hell

I can’t imagine what it must be like to go to space as a profession, and then need to leave or retire. A bittersweet thing, to be sure.

Would you like to read some moving fiction about it?

_Phases of Gravity_ by Dan Simmons takes it head-on with an astronaut whose days flying are over.

More obliquely a national loss of space capability is taken on by Norman Spinrad in _Russian Spring_.

Both great reads, and sad.

Not the same plane, but this reminded me of the amusing "my planes faster than yours" ground speed check of the Blackbird pilot.


This comes from place of ignorance, so please be kind: why "speed record" is considered Mach 6.2 when ISS ground speed is like Mach 22? There are humans there, they got up to speed and regularly come back. How it is different than going to similar velocities in thin atmospheres over 50km?

> the world record for speed by a piloted, powered aircraft

It literally says it right there. The ISS is not a piloted, powered aircraft. Also it was Mach 6.7, not 6.2.

Incidentally, the speed record for a crewed vehicle was set by Apollo 10 at 11.08 km/s - almost half as fast again as the ISS.

Fictional but germane scene from The Martian:

> [after hearing he has to take the top off of the Mars Ascent Vehicle] I know what they're doing. I know exactly what they're doing. They just keep repeating "go faster than any man in the history of space travel", like that's a good thing. Like it'll distract me from how insane their plan is. Yeah, I get to go faster than any man in the history of space travel, because you're launching me in a convertible. Actually it's worse than that, because I won't even be able to control the thing. And by the way, physicists, when describing things like acceleration do not use the word "fast". So they're only doing that in the hopes that I won't raise any objections to this lunacy, because I like the way "fastest man in the history of space travel" sounds. I do like the way it sounds... I mean, I like it a lot.

To be fair, calling X-15 “piloted, powered aircraft” is a stretch. While it’s piloted and powered, it’s definitely not conventional plane, i.e. aircraft. It’s a rocket that is launched from the carrier plane and has ability to land as (unpowered) glider after (unpowered) ballistic flight. In this sense it’s not different from the space shuttle: launched from the carrier vehicle, uses it’s rocket engine to go up, has orbital flight with ballistic descent, lands as a glider.

Fair record category would be “takes off under own power, sets record, lands by itself with all the equipment”. X-15 definitely doesn’t qualify.

"Aircraft" doesn't make assumptions about the power source. Piston engine, turboprob, turbojet and turbofan aircraft are all called aircraft despite all having different sorts of propulsion. All of those still breath air of course, but we don't hesitate to apply the term to experimental/prototype electric aircraft either. So an aircraft needn't breath air, and therefore having a rocket engine shouldn't be a disqualifier.

"Takes off under it's own power" is a qualification you're not the first in proposing, but it's controversial because it would disqualify many famous aircraft, such as the Bell X-1 and according to some (mostly Brazilians) the Wright Flyer. There is also the matter of carrier-launched aircraft that take off when the carrier is running flat out into the wind, let alone with a catapult; it's easy to say they are not taking off entirely under their own power. You could make a similar argument for rocket-assist JATO configurations, if the plane drops the JATOs after takeoff.

This is exactly my point, records should be apples-to-apples. This particular record should go to Shuttle or similar “aircraft”. In particular Shuttle is hard to distinguish from X-15. Same thing, but more of it.

“Takes off under it’s own power and brings all equipment back” is good limitation - otherwise you can trivially design a system that drops multi-stage booster and lands tiny glider after setting a record.

> was set by Apollo 10 at 11.08 km/s - almost half as fast again as the ISS.

You mean twice as fast as the ISS, don't you?

11 km/s is escape velocity at ground level: no way ISS could stay in orbit going twice that fast!

"again" is the key word. It means 1.5x the speed of the ISS.

I had never met that construction. Thanks a lot!

> It literally says it right there. The ISS is not a piloted, powered aircraft. Also it was Mach 6.7, not 6.2.

But aren't the Soyuz capsules that dock with the ISS piloted and powered ?

I would assume that Soyuz capsules aren't considered aircraft. They don't really fly, per se, they get launched on a rocket and then fall like a rock back to earth.

You could make a stronger argument for the Space Shuttle, which re-enters at about Mach 25, IIRC, and is gliding. But it's not doing so under power.

> Soyuz capsules aren't considered aircraft

While I suspect you're right, Soyuz capsules do use aerodynamic lift to control descent rate and steer to the landing site. In some ways they are very, very (very) inefficient gliders.

I'd expect the definition of a powered aircraft to include the ability to maintain some given flight altitude and speed for some appreciable amount of time.

It is possible to do something sort of like this in a space capsule returning to Earth, where you muck up your entry vector and come in at too shallow an angle. You can then (depending on the circumstances) bounce off the atmosphere, and gain altitude briefly. And then you probably come back in the atmosphere on too steep an angle, and die due to g-load or overheating.

Yes, but they're outside the atmosphere and therefore don't have a Mach number.

A Soyuz capsule that never enters the atmosphere would have a very upset crew.

Soyuz can be manually piloted, but are normally automated (Progress can not be piloted and is essentially the same thing after all). They're also not aircrafts.

I don't get how you missed "There are humans there, they got up to speed and regularly come back"

> Also it was Mach 6.7, not 6.2.

Hahah, when compared to Mach 22, is that pedantry relevant?

I think the differentiator is "powered flight". The ISS relies on momentum and gravitational pull to sustain that speed. Similar with the Apollo 13 CM which reached something like 36,000 MPH on the return leg, giving the astronauts on board the moniker as the fastest that humans have ever travelled in a man made vessel - not considered a speed record per se because it wasn't using an internal power source to propel (to a major extent).

The X-15 still had to deal with the other aspects of atmospheric flight like weight (carrying its own fuel source), drag and heating due to friction etc.

ISS does not relies on anything to sustain its speed, this is not how speed works.

But again, I wrote rather short comment, and part of it was:

> There are humans there, they got up to speed and regularly come back

To put it in other words, to get to ISS, crew has to accelerate to it's speed, and to get back, to lose it.

In-atmosphere flight is completely different, and the line is normally considered to be somewhere between 70 and 100km.

Re-entry is faster, but not powered. Other vehicles (missiles etc) achieve high speeds but are unmanned.

Also, mach number is dependent on altitude if I remember correctly.

The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric temperature generally decreases with increasing altitude between sea level and 11,000 meters (36,089 ft), the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to −56.5 °C (−69.7 °F) at 11,000 meters (36,089 ft) altitude, with a corresponding speed of sound (Mach 1) of 295.0 meters per second (967.8 ft/s), 86.7% of the sea level value. [0]

[0] https://en.wikipedia.org/wiki/Mach_number

Does that mean that when you're flying an X15 you lose 6.2/22 = 28% of your bodyweight to the Coriolis force? That's pretty neat.

I think that, of the so-called inertial or ficticious forces, you are thinking of the centrifugal rather than the coriolis force [1].

On any of the ballistic / into space flights, you would experience weightlessness between the engine cutoff and the point where atmospheric forces became noticable -- this is what the space tourism companies are aiming for.

I do not know if any flights were conducted at a constant altitude, but note that the centrifugal force goes by the square of the angular velocity.

Also, Mach numbers depend on atmospheric temperature and therefore indirectly on altitude. Strictly speaking, a Mach number for the ISS is meaningless, and even if we are being lax, the figure of Mach 22 is not directly comparable to the X-15 record Mach number. The comparison must be made between speeds, which are, approximately, 17,000 mph for the ISS and 4,500 mph for the X-15 record.

If we disregard the relatively small difference in the radius (from the center of the earth), then my BOE calculation suggests that the reduction in weight is about 7%.

Note, however, that while the motor is running, its acceleration is the biggest contribution to weight (reaching up to 4g as the fuel weight goes down.) Once it is cut off, then our assumption of level (i.e. non-ballistic) flight assumes that the airplane is capable of generating lift equal to its weight, which implies sufficient atmospheric density for the small wings to generate that lift. This, in turn, seems to imply enough density to produce a non-trivial deceleration due to drag, which also contributes to weight. Therefore, I doubt that there is any phase of the flight where the centrifugal reduction of weight is the dominant effect.

[1] https://en.wikipedia.org/wiki/Fictitious_force

> Does that mean that when you're flying an X15 you lose 6.2/22 = 28% of your bodyweight to the Coriolis force?

I think you mean centrifugal force. Unfortunately, no, you don't feel quite that much less weight, because centrifugal force goes like the square of the velocity, so the ratio is the square of 6.2/22, or about 0.08, i.e., only 8%.

There is a Coriolis force here too; it's just much smaller than the centrifugal force.

Consider a plane flying at ground level along the equator at groundspeed velocity v in the direction of the Earth's rotation. In the Earth's (rotating) reference frame there is a centrifugal acceleration based on the Earth's angular velocity and a Coriolis acceleration given by -2 W x v, where W is the Earth's angular velocity and v is the plane's velocity. This ends up pointing straight up in this configuration.

So in the plane's reference frame there is a straight-up centrifugal acceleration, given by (W + v/R)^2 * R = W^2 * R + 2W x v + v^2/R which is balanced by the aerodynamic and gravitational forces on the plane (which in this frame is non-accelerating), while in the Earth's reference frame there is a straight-up centrifugal acceleration given by W^2 * R and a straight-up Coriolis acceleration of 2W x v, and the plane is accelerating radially down at v^2/R due to gravity and lift combined.

Now to put numbers to this, the speed record for an X15 is about 2000 m/s, R is 6.4 * 10^6 m, and W is 1 revolution per 24 hours, or 1/86400 s^1. So the three force components look like this, if I am doing my numbers right:

  W^2 * R is .00086 m/s^2

  2W x v is 0.04 m/s^2

  v^2/R is 0.63 m/s^2.
So the v^2/R "centrifugal force due to the plane's motion" term is by far the biggest contributor here.

> There is a Coriolis force here too; it's just much smaller than the centrifugal force.

Yes, agreed.

It really depends on how you turn. Like, if you would go high enough to have close to none air pressure, and stop accelerating, you would feel about 0% of your body weight, being in free fall, same as ISS. You don't have to go orbital speed to be in free fall. You have to have that speed only not to fall while free falling :)

That depends on your orientation.

The X-15 was awsome, and "bad" is being used in the informal North American sense that means "good" or "excellent".

If you want some planes that live up to the other sense of "bad", here is an amusing article about several planes you might enjoy [1].

[1] https://www.cracked.com/article_18839_7-planes-perfectly-des...

Was fun making X-15 model rocket kits as a kid

Okay, the X-15 was pretty great, but speed alone doesn't make it "the baddest airplane the world has ever known". When I read the title, I immediately, unhesitatingly assumed it would be this: https://en.wikipedia.org/wiki/Gee_Bee_Model_R.

Yeah, calling the X-15 the most badass plane ever is a bit silly. If it counts, then why isn't the Space Shuttle "the most badass plane"? It went faster & higher, after all.

Anyway, I'd assumed it was going to be the SR-71, but yours looks awesome & I enjoyed the article either way!

Thanks for that link, that Gee Bee is definitely badass.

From the article:

> “I honestly can say I was so terribly focused on flying those profiles as closely as possible that I didn’t really have time to look out the window and see how pretty it was,”

Joe Engle, describing the X-15

> And, remarkably, it also went on to fly into space more than a dozen times.

Only twice, according to the standard everyone else uses. Saying the X-15 has been to space a dozen times is like weighing yourself in kilograms to make the number smaller. Certainly helps the ego of those Air Force pilots, and Blue Origin, though!

didn't see this in the article but I recall an x-15 story I read as a kid. seems after a landing the plane was being inspected and engineers noticed a burn hole that took out part of a real stabilizer and all the way through the airframe and fuel tank. Fortunately, the fuel tank was already empty when it happened.

the story may just be X-15 folklore but my child self was impressed haha

This was on flight 188. Shockwaves from a scramjet mockup impinged on the ventral stabilizer and local heating caused a burn through.

I'm in awe of the balls that those guys had in that era--to strap one of those beasts to their ass. How surreal that.

An example of a reusable rocket vehicle. Some versions had throwaway extra propellant tanks.

That road was not really taken until now potentially with SpaceX. (The Space Shuttle had design / political issues that made it operationally very expensive.)

The s/baddest/worst experience ever?

No, in this case "bad" is a synonym of "rad".

Made me want to read the “right stuff”

Or watch First Man which opens with Neil Armstrong having an interesting flight in the X-15.

There's also an old movie called "X-15" which I enjoyed a lot as a kid.

As a young kid here in the UK I had a Ladybird book with a picture of an X-15 - almost 50 years later I can still remember my fascination with that machine.

99% Certain it was this one:


Now I have to find one!

It’s one of the greatest spaceflight books I’ve read. It’s movie still holds up very well even today.

This is hilarious

Guinness World Records recognized NASA's X-43A scramjet with a new world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7,000 mph.


The concept of both piloted and powered seems to be really elusive.

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