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The B-52 was designed in a hotel room over one weekend

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Re: The B-52 was designed in a hotel room over one weekend

#171

Post by jabl »

chasil wrote: post #160
jabl wrote: post #153

Earlier quoted context omitted.

Hmm, I'm not familiar enough with jet engines to say whether that is expected or not. 15% doesn't sound like a huge improvement, I agree. But I'll note the F130 is a medium bypass business jet engine producing 'only' around 75kN. 8 of those is about 600kN, which could be achieved with two of those newest generation civilian high bypass turbofans used e.g. in the B787 or A350. I suspect the motivation was to choose a…

So what happens if four newest-generation high-bypass turbofans are installed on a B-52? Is the airframe at risk in doubling the thrust at full throttle?

Doubling the thrust is likely overall a bad idea, for the reasons you mention.

Also looking at other posts in this discussion, it seems the 4-engine option (4x 150kN class size engines to provide about same overall thrust) was discarded because the asymmetrical thrust in case an engine gives out at a critical moment (takeoff, say) would mean that the plane would need a bigger tail in order to have enough rudder authority. Which in turn would mean that the airframe would need strengthening to take the added weight and stress from that bigger rudder. Etc. etc. leading to the cost of the engine replacement program spiraling out of control. So in that sense as close to a 1:1 as possible is the right decision.

Re: The B-52 was designed in a hotel room over one weekend

#172

Post by Someone »

froidpink wrote: post #100
lelandfe wrote: post #92

Earlier quoted context omitted.

This was genuinely an overnight success, though. They got approval on the strength of this design. And the broad strokes design of the aircraft seemingly stayed intact through the subsequent processes. This entire comment chain is bewildering, we're attacking strawmen. Did anyone read this article and leave assuming no further work was done after approval? Was this HN comment chain enlightening to anyone ? Who are we…

It was a strong conceptual design, yes. For my aerospace engineering undergrad we also had to create a conceptual design for a new aircraft. And of course, as university projects go, we basically did it in five days. But I won't tell you how many iterations we would've had to go through until we had an optimum configuration ready to be sent to detail design The headline makes it look like their design was a definite…

That doesn’t look abnormal for the time period. The first B-29 Super Fortress, for example, flew in September 1942, with the design started in 1938 (https://en.wikipedia.org/wiki/Boeing_B-29_Superfortress)

Also, Nazi Germany had a few designs that took way shorter than that to go from idea to first flight. An extreme example is https://en.wikipedia.org/wiki/Heinkel_He_162#Prototypes:

“The He 162 V1 first prototype flew within an astoundingly short period of time: the design was chosen on 25 September 1944 and first flew on 6 December, less than 90 days later”

They did have to cut ‘some’ corners to get there, though. That Wikipedia page mentions that it used a highly acidic glue that would disintegrate the wooden parts it was intended to be fastening, that that caused problems on the first flight and a deadly crash on the second, but that it wasn’t considered important enough to hold up the production schedule for even a day.

Re: The B-52 was designed in a hotel room over one weekend

#173

Post by KennyBlanken »

GuB-42 wrote: post #86
ofrzeta wrote: post #32

Earlier quoted context omitted.

Platonic question: is it still a B-52 then? cf. the Ship of Theseus

At least in civilian aviation, it is a very relevant and practical question, and a major contributor to the Boeing 737-MAX fiasco. There is a thing called "type rating", that is qualification pilots need to have in order to fly a specific type of plane. For example, pilots need a type rating for the Boeing 737 in order to fly a Boeing 737. Manufacturers try to do everything they can not to require another type rating…

> One of the root causes of the B737-MAX crashes is that Boeing tweaked some settings in order to make the B737-MAX behave like the original B737 when it was, in fact, a different plane, and they did it wrong.

This is wildly wrong. The only thing you got right is that the MAX was designed to avoid needing a new type certification.

Boeing radically shifted the Cg to accommodate changing trends in the commercial airline industry which were resulting in Airbus's planes being more competitive. They shifted it well outside what would be considered prudent.

This required flight control software bandaids to keep the plane stable (or perhaps better put, from entering a flight envelope where loss of control would happen), but they then also cheaped out of providing redundancy for some critical sensors... AND cockpit annunciators to alert on failures of the sensors.

Boeing then passed off the Cg shift and additional systems as very minor changes in the filing for their airworthiness certifications, the FAA rubber-stamped everything because they didn't have the staff to review all these certificate filings so they largely trust manufacturers...

...and then making things even worse, Boeing did very little to disclose the additional stability system and sensors to the airline's chief pilots who develop the in-house training. To say they were furious to learn they hadn't been told of the new systems would be an understatement.

The MAX crashes would have been substantially less likely if the pilots had benefitted from their airline's chief pilots knowing of the safety systems and having training on how to handle failurs, as well as warning annunciators for sensor failures....but Boeing wanted to save a thousand bucks or so per plane - or more likely, wanted to avoid drawing attention to the situation and having people ask "why is a critical flight control system dependent upon a single sensor?", which is likely why they also did little to inform airlines of the new systems, train the chief pilots on it, etc.

Re: The B-52 was designed in a hotel room over one weekend

#174

Post by Animats »

mannykannot wrote: post #21
segfaultbuserr wrote: post #8

The B-52 design proposal was done in a hotel room over one weekend, the actual engineering took at least 3 years, including "670 days in the wind tunnel". That is not to say the weekend hotel proposal was not an impressive accomplishment in itself, it was. But there's a difference between laying out a software architecture and writing code. https://en.wikipedia.org/wiki/Boeing_B-52_Stratofortress#Des... > On Thursday…

I feel it is fair to say that in many ways, the "architecture" of the B-52 was pioneered in Boeing's B-47 (first flight 17 December 1947 - seven months before these meetings.) This was a truly innovative aircraft, unlike many other contemporary designs (from Boeing as well as other manufacturers) which resembled their piston-engined precursors. The initial Boeing proposals for the B-52 look like throwbacks to that ap…

Yes. The B-47 was sort of a scaled-up jet-fighter. Look at the cockpit layout.[1] It outperformed some fighters of the era. The original B-52 proposal looks like a modified B-36. The B-36 was the first intercontinental bomber, with "6 turning and 4 burning" - 6 props running on piston engines, plus four jets. That early B-52 proposal looks like something based on the B-36.[2] A bigger B-36 would probably have worked, but it would have been a dead end.

Both the B-36 and the B-47 were difficult aircraft to fly and maintain. The B-36, with all those piston engines, was a headache. Too much powerplant to maintain, and underpowered by jet standards. The B-47 needed a rocket assisted takeoff booster to get off the ground with a reasonable amount of runway, and operated too close to the "coffin corner", with cruising speed and altitude too close to stall. Over 2000 were built, over 200 crashed, and none remain flyable. With the B-52, the USAF got an intercontinental bomber that flew well, could be maintained, and had enough power to get itself off the ground without rocket boosters.

Its successors were less useful in actual conflicts. Too short ranged, too expensive, less bomb load, etc.

[1] https://www.youtube.com/watch?v=iV1hVLGLZ-w

[2] https://www.youtube.com/watch?v=l1-urTRxeEM

Re: The B-52 was designed in a hotel room over one weekend

#175

Post by yread »

jabl wrote: post #153
yread wrote: post #123

Earlier quoted context omitted.

It's interesting that even though the bypass ratio changed from 1.4 to 4.2 (so it's quite a different engine, lot quieter for sure) the fuel consumption only went down 15% (22g/kN.s to 18.6g/kN.s)

Hmm, I'm not familiar enough with jet engines to say whether that is expected or not. 15% doesn't sound like a huge improvement, I agree. But I'll note the F130 is a medium bypass business jet engine producing 'only' around 75kN. 8 of those is about 600kN, which could be achieved with two of those newest generation civilian high bypass turbofans used e.g. in the B787 or A350. I suspect the motivation was to choose a…

These engines are also way larger diameter => redesign nacelles => higher drag and moment => engine mounts + wings ...

Also this family of engines (F130/BR700) has insane reliability - something like one unplanned engine removal per 100,000 hours. Some have reached 1 million hours

Re: The B-52 was designed in a hotel room over one weekend

#176

Post by Animats »

themadturk wrote: post #163
Tangurena2 wrote: post #136

Earlier quoted context omitted.

Coincidentally, I was watching a YouTube video last night about the YB-60. This was a version of the B-36 with the same jet engines as the B-52. And the aircraft lost in a competition with the B-52 because the Boeing jet was just plain better than the Convair jet. Boeing did a very good job. I don't think there have been (or will be) another aircraft that lasted this long in service. There are prettier aircraft (in m…

No, the B-52 is a paragon of beauty (no sarcasm there...it's always been my favorite aircraft). And the C-130 is right around the same age, not to mention still (I believe) being manufactured.

So is the UH-1, the Huey helicopter. Over 16,000 made, and many still flying.

Re: The B-52 was designed in a hotel room over one weekend

#177

Post by paganel »

p_l wrote: post #87
paganel wrote: post #65

Earlier quoted context omitted.

I’ve not read too much on the Soviet space program, but whenever I read about Buran (a wonderful accomplishment per se) my thought process goes something like this: “The Soviets must have seen the Americans working on the shuttle thing -> the Soviets must have thought that that shuttle thing was great mostly on account of the Americans working on it -> the Soviets built a shuttle system for themselves -> the Soviets…

Buran system was very, very different from US' STS, and honestly multiple groups combined under one umbrella to get what they wanted in Buran project. Some bits of Buran were a "me too" (the visual look of the orbiter, for political reasons), but Soviet space program has combined multiple previous tracks that existed independent of what Americans were doing. Among various tracks that combined together, there was 1. S…

Thanks a lot for the detailed response, that cleared up things for me.

Re: The B-52 was designed in a hotel room over one weekend

#178

Post by p_l »

justsomehnguy wrote: post #168
p_l wrote: post #67

Earlier quoted context omitted.

I didn't miss the /s, but I feared others might think different ;) From what I've read, the decisions to make Buran look externally like STS orbiter was a political one, and the engineers at MiG OKB weren't happy about it - they have been working on a bunch of space planes for some time, including the infamous suborbital fighter. However the similarity was found to have political benefits in the weird opposite of kre…

I checked the Wiki article on it, just to be sure. I just don't understand how it could look any way different (at least significantly), this is a classical case of the function dictating the form.

Essentially, the Buran orbiter had different function, and thus different forces on its form.

US' STS shape was ultimately dictated by its cross range requirements combined with cargo capacity. Explicit case of function leading to specific form.

Buran didn't require the same huge cargo capacity in the orbiter, because Soviets had already tested and verified self-assembly of space station in orbit from multiple launched modules (technology that they would later employ in ISS). For huge capacity it had Energia, which once proven could be also launched on Polar orbits (the specific requirements from USAF for STS involved heavy cargo on polar orbits from Vandenberg).

This meant that Buran orbiter had wider design space to explore, and previous experiments in crewed reusable spacecraft were centered around lifting body shape, to extent much higher than STS was. However, the command to make it look like US STS came pretty early in the project, in addition to general lack of documents, so we don't really know how they would go.

Re: The B-52 was designed in a hotel room over one weekend

#179

Post by p_l »

aerostable_slug wrote: post #145
p_l wrote: post #39

Earlier quoted context omitted.

Buran was made to look like Shuttle (despite opposition of engineers on the project), but was completely local design.

How does one separate the outer mold line of the spacecraft from its performance? Isn't Buran's appearance driven by similar requirements vs. aesthetics? What else would it have looked like — if you want lots of crossrange capability, you're not going to get something that looked like Faget's designs, would you?

Buran had different design requirements (once you discard the political), because unlike STS the orbiter wasn't sole launcher of the system - Energia took care of shipping heavy cargo to whatever orbit you wanted. So they had different set of constraints including size & prospective contents of the cargo bay.

They have also flirted with the idea of just putting two jet engines into orbiter for extra cross range, which was probably not an option on STS given the huge dead weight of engines

Re: The B-52 was designed in a hotel room over one weekend

#180

Post by GuB-42 »

KennyBlanken wrote: post #173
GuB-42 wrote: post #86

Earlier quoted context omitted.

At least in civilian aviation, it is a very relevant and practical question, and a major contributor to the Boeing 737-MAX fiasco. There is a thing called "type rating", that is qualification pilots need to have in order to fly a specific type of plane. For example, pilots need a type rating for the Boeing 737 in order to fly a Boeing 737. Manufacturers try to do everything they can not to require another type rating…

> One of the root causes of the B737-MAX crashes is that Boeing tweaked some settings in order to make the B737-MAX behave like the original B737 when it was, in fact, a different plane, and they did it wrong. This is wildly wrong. The only thing you got right is that the MAX was designed to avoid needing a new type certification. Boeing radically shifted the Cg to accommodate changing trends in the commercial airlin…

I generally agree with you, except for the fact that it was more of an aerodynamic issue than a center of gravity issue: the large body of the engine produced lift at higher angles of attack, making the nose go up and worsening the problem. The fact the engine was more powerful also contributed to that problem: the higher thrust produced more upwards torque.

And I am not saying that the software bandaid and the goal of avoiding a new type certification is a bad thing. In fact, it is done all the time with no ill effect.

What I am saying is that they did it wrong, and that's the real problem. Your explanation on what they did wrong is, I think, entirely correct.

My hypothesis is that if they didn't care about keeping the same type rating, they probably could have skipped the bandaid and trained pilots to just keep out of that dangerous configuration, just like pilots are trained to recognize, avoid and recover from stalls. It didn't look like an unmanageable problem for pilots, more like something they needed to be aware of and train for.

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