This, if anything, understates how weird the XB-70 was; in particular it skims right over https://en.wikipedia.org/wiki/Zip_fuel
The XB-70 (2019)
101–110 of 137 posts
Re: The XB-70 (2019)
#102That era of aviation was nuts. I wish I was around for it. Men with slide rules working out the limits of material science, aerodynamics, and everything else, all at once. Because it wasn't enough to just push one limit, you had to push half a dozen others to get things to that first limit. And the rate of advance was just staggering. The XB70 flew in late 1964. Concorde was doing revenue flights in 1976, cruising at…
The sheer amount of gas this plane must have carried in order to fulfil its mission…
And not just any gas: https://en.wikipedia.org/wiki/Zip_fuel
Re: The XB-70 (2019)
#103Earlier quoted context omitted.
> 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 m…
In a peer war it's pretty damn dubious whether a B-52 with four modern engines will be more survivable than a B-52 with 8 antiques. Either way the most they'll be able to do is launch standoff munitions from a distance they hope will keep them safe, and if it doesn't then they're dead anyway. In a scenario short of that, we're just quibbling over the degree of waste American voters will put up with (it's the military, so the answer is a lot.)
Re: The XB-70 (2019)
#104Earlier quoted context omitted.
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 m…
In a peer war it's pretty damn dubious whether a B-52 with four modern engines will be more survivable than a B-52 with 8 antiques. Either way the most they'll be able to do is launch standoff munitions from a distance they hope will keep them safe, and if it doesn't then they're dead anyway. In a scenario short of that, we're just quibbling over the degree of waste American voters will put up with (it's the military…
That's pretty much irrelevant. Engine replacement is about increasing range and/or reducing tanker requirement/airframe wear, and reduction of maintenance costs because existing engines are ancient and their maintenance costs are high. One of the reasons this program has been postponed for so long was retirement of C-141 that left USAF with plenty of still good TF-33s. But now these are starting to run out too.
Re: The XB-70 (2019)
#105Earlier quoted context omitted.
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.
> There are hardly any targets for which lobbing high explosive with an ICBM is cost effective.
Unless your neighbor has effective air defenses and you want to make a political point...
Re: The XB-70 (2019)
#106Earlier 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…
I think any war with China would be predominantly economic and cyber. I don’t think it’s viable for either party to perform a mainland strikes and I don’t think it would become nuclear, but who knows. If things escalate during the current POTUS’s term, I think it will come down to meetings and deal-makings, because that is POTUS’s passion and preferred way. I think any war with Russia would be, well is, economic and…
> because that is POTUS’s passion and preferred way.
Just like he surrendered Ukraine to Russia. An amazing deal for everyone involved, except Ukraine.
Re: The XB-70 (2019)
#107This, if anything, understates how weird the XB-70 was; in particular it skims right over https://en.wikipedia.org/wiki/Zip_fuel
Dissatisfied with the progress, though, just weeks later the Pentagon canceled the HEF-3-powered J93 engine program and limited the Valkyrie program to the use of JP-4 fuel only. Testimony by USAF scientists before Congressional committees revealed that the technical hurdles and the operating cost of using HEF-3 as a jet fuel were prohibitive given the defense budget of the day.
Re: The XB-70 (2019)
#108As 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…
> ...especially when someone is particularly passionate about them. The engineer-type brain is very much prone to "... in order to prove we can, " as opposed to "Because we should. Or because this is useful. Or because this even does the job claimed." Across a range of fields. A/B testing "engagement hacks" falls into this category, as far as I'm concerned. It was certainly successful at the stated goals.
When the project started a Mach 3 strategic bomber that out of the reach of surface to air missiles, and that could hit multiple targets on its way, was a huge advantage. It was obsoleted by ICBMs and better antiaircraft weapons, but it was still a hugely successful development program. It just didn’t provide a useful plane, but helped develop all the parts for future ones.
Re: The XB-70 (2019)
#109As 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…
KISS should always be #1 engineering principle, in any engineering. In software one I can speak a bit, the unnecessary complexities always bite back. Maybe not the creator of them, but given company always. Or as one quite bright guy said - 'this should be as simple as possible, but not simpler'.
But its borderline boring, nothing shiny, nothing to sell new subscriptions or trainings for, nothing to get promotions for, things that just keep running (TM) slip out of focus. Look at how brilliant engineers handle boredom and routine - usually very, very badly. Its not what 'hackers' want to do, despite thats exactly what all normal companies want to get. Unprofessional for sure, but when most of potential and otherwise brilliant employees have issues with this, they tend to get some slack.
Re: The XB-70 (2019)
#110Earlier quoted context omitted.
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.
The B52 was never a low altitude bomber, you're thinking of the B1A, which was to be a high altitude, super sonic bomber but SAM missile tech advanced faster than the development of the bomber could happen, and it was canned, before being resurrected as a subsonic, low altitude bomber (the B1B). The XB-70 couldn't make that switch because it was a ridiculous design (for starters). The B52 role was to have wings (and…
> We're going to be caught with our pants down with B52s as the stains on our underwear.
Meanwhile: their entire imported food and oil supply has been easily blockaded by ancient, conventional systems.