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The XB-70 (2019)

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Re: The XB-70 (2019)

#91

Post by anovikov »

runjake wrote: post #4

As someone who once worked on B-52s, I find it amusing how many "successors" it has outlasted. And I know why, because I worked on many of those, too. It has taught me to be skeptical of unproven claims and promises, especially when someone is particularly passionate about them. Also that simplicity is king. Complexity is the enemy. I have great respect for the XB-70. It's the only strategic bomber I haven't worked o…

Well, as i understood it has failed because it could no longer provide the main benefit over B-52 it was initially intended to provide: high-altitude penetration - over it's development time, engagement envelope of SAM systems expanded in altitude and speed so much that even XB-70 could no longer hope to get through. So it wasn't any better than B-52, except much pricier. It could also get to the target faster, but for applications where time of flight was critical, nothing could beat an ICBM anyway. They switched to cruise missiles - to keep B-52s out of harm's way, and low-altitude penetration (B-1B), then when radars became capable of discerning things vs ground reflections too well, they switched to stealth - but Soviet Union fell apart before they knew if it could work or not.

So it's not about any technical failures of XB-70 itself, just that it turned out to be unable to do the job it was planned for.

Wrong?

Re: The XB-70 (2019)

#93

Post by anovikov »

jiggawatts wrote: post #56
runjake wrote: post #4

As someone who once worked on B-52s, I find it amusing how many "successors" it has outlasted. And I know why, because I worked on many of those, too. It has taught me to be skeptical of unproven claims and promises, especially when someone is particularly passionate about them. Also that simplicity is king. Complexity is the enemy. I have great respect for the XB-70. It's the only strategic bomber I haven't worked o…

> Also that simplicity is king. Complexity is the enemy. Which sounds good, but the B-52 planes used eight very old jet engines each that are complex to maintain. Rolls Royce offered to replace these with four modern turbofan engines but were turned down. They finally relented and there’s a new program that will run to the end of the 2030s(!) to replace the eight engines with… eight engines. This doesn’t sound simple…

You can't replace them with 4 engines because those will have to be of bigger diameter and they might scratch the ground of some less than perfect airfields. The engines HAVE to fit into the same nacelles. And they have to provide enough thrust while having same diameter -> this is hard because the goal of replacement is efficiency, and you replace a low-bypass engine for a high-bypass to increase efficiency, which means that hot section must be smaller, and thus able to survive more heat and pressure.

Previous programs of B-52 re-engining indeed, tried to replace 8 engines with 4. It never worked because of diameter/ground clearance issue. They had to wait until progress in aircraft engines allowed for the engine of same diameter to provide the necessary efficiency boost.

By the way, re-engining will vastly reduce air refuelling needs, and further extend airframe life because of lighter takeoff weights, as they won't need to take as much fuel on most missions. And in a pinch, almost any mission will be doable without refuelling at all.

Re: The XB-70 (2019)

#94

Post by lazide »

runjake wrote: post #44
loloquwowndueo wrote: post #29

Earlier quoted context omitted.

What killed the xb-70 was the advent of better air to air missiles that nullified its high-altitude high-speed flight advantage. ICBMs also render other kinds of bombers obsolete and yet b52 and tu-95 are still around.

From what I know, what actually killed the XB-70 was ICBM advancements. The B-52 survived by becoming a low altitude bomber and an excellent, cheap nuclear-capable cruise missile delivery platform that was comparatively cheap to operate at the same level of effectiveness as the B1-B and B-2A for similar roles. Russia more or less mirrored this with the Tu-95.

Eh, the B52 has survived because it is amazing at being a bomb/missle/etc. dumptruck, and doesn’t have anything fancy which is expensive to maintain or particularly brittle.

Even the airframes are mostly still alive 50+ years later, which is mind blowing on aircraft. They have made a new B52 since ‘62 but they keep on trucking.

It isn’t super fast (the B1 is that), or stealthy (B2 or B21), or sexy (B1), or nimble (any of the generations of fighter bombers that have come and gone). It doesn’t fly particularly low. Or particularly high.

But god damn can it carry and drop absolutely massive quantities of whatever type of ordnance you want, pretty much anywhere you want on the globe, and do it over and over and over and over again. 70,000 lbs worth

The 737 is still around for pretty much the same reasons.

Any alternative ends up being less effective at the same tasks, or more niche/expensive.

They’re basically the alligators or horseshoe crabs of the airplane world. Or the M2 heavy machine gun. Or the Cessna 182 or Robinson R22 of the GA world.

Re: The XB-70 (2019)

#95

Post by rmnwski »

runjake wrote: post #46
rmnwski wrote: post #37

Earlier quoted context omitted.

I always wondered why the B-52 didn’t get replaced by converted airliners (787 has quite similar dimensions I believe). Would be much cheaper to run and could do practically the same thing, no?

They look the same to a layman, but they are very different airframes, with a different wing sweep and different load capabilities, among many, many other differences.

of course the b-52 is a completely different airframe. Just wondering what the reasons are you wouldn't be able to convert airliners to be used in that role. It's been done for fire bombing!

Re: The XB-70 (2019)

#96

Post by Animats »

runjake wrote: post #4

As someone who once worked on B-52s, I find it amusing how many "successors" it has outlasted. And I know why, because I worked on many of those, too. It has taught me to be skeptical of unproven claims and promises, especially when someone is particularly passionate about them. Also that simplicity is king. Complexity is the enemy. I have great respect for the XB-70. It's the only strategic bomber I haven't worked o…

A good look at the XB-70. No narration, just highly detailed pictures.[1]

The XB-70 looks like nothing that came before, and nothing after it looks like the XB-70. Six engines side by side in the tail. It looks like a 1950s concept for a spaceplane. It was apparently a good aircraft, but expensive and didn't fit any military need of the time.

(The need for high-altitude supersonic bombers declined once surface to air missiles got good enough to hit them.)

[1] https://www.youtube.com/watch?v=9GhYBVM7UHQ

Re: The XB-70 (2019)

#97

Post by rbanffy »

Zeetah wrote: post #48
Enginerrrd wrote: post #7

Earlier quoted context omitted.

> Also that simplicity is king. Complexity is the enemy. As someone that has managed engineering teams for large projects, I 100% agree. One of the issues with computers IMO is that it has made bad engineering easier. Back when you had to check everything with a slide-rule, you had a real appreciation for the skill and engineering prowess and experience to make things absolutely dead simple.

One of my favorite things is in the watch world, every mechanism besides showing time is called complication. When one talks about a feature, or an item as a complication, just the act of doing that forces one to be more deliberate. https://en.wikipedia.org/wiki/Complication_(horology)

I like to say that whatever the complexity is, it is in the nature of the problem itself and isn’t something that’s open for us to design. Only when we design a solution we risk introducing complication.

Of course, we can always choose to solve the least complex problem.

Re: The XB-70 (2019)

#99

Post by varjag »

ethbr1 wrote: post #88
psunavy03 wrote: post #64

Earlier quoted context omitted.

> ICBMs also render other kinds of bombers obsolete and yet b52 and tu-95 are still around. This has been proven utterly false since the 1960s, because a) you can't recall an ICBM after firing it, b) you can't retarget an ICBM after firing it, and c) there's no reliable way to tell nuke warheads from conventional ones, meaning every one you launch has to be assumed to have a nuclear payload, with all the world-ending…

We also live in a world where Russia launches conventionally armed IRBMs against their neighbor. https://en.m.wikipedia.org/wiki/Oreshnik_(missile)#First_ope...

It was not conventionally armed. It had dummy training warheads, conventional payloads for it are not even being developed. There are hardly any targets for which lobbing high explosive with an ICBM is cost effective.

Re: The XB-70 (2019)

#100

Post by TheOtherHobbes »

nradov wrote: post #74
FpUser wrote: post #67

Earlier quoted context omitted.

>"If the US is going to maintain a credible deterrent against China then something has to change. Either defense spending has to go up or we have to drastically scale back activities in other areas. And no, cheap AI drone swarms won't replace the capabilities of something like a B-21." Assuming the US would actually need B21 capability in a war with China. Those will be probably blown up from the sky very fast. Besid…

Nah. Everything we know about the B-21 indicates that it's probably pretty survivable against the Chinese air defense system. Especially for stand-off strikes near the Taiwan Strait where it wouldn't have to overfly radar stations. The design was literally optimized for exactly that purpose. Ironically the B-21 is probably safest in the air. The greatest kinetic threat is on the ground because forward air bases gener…

The greatest kinetic threat is from drone swarm attacks, which can be delivered to the vicinity of an airbase from a handful of anonymous-looking trucks or vans.

One or two grenade-strength shrapnel devices are enough to make a $700m dollar special project useless.

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