[HN Gopher] The XB-70 (2019)
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The XB-70 (2019)
Author : rbanffy
Score : 100 points
Date : 2025-02-25 18:12 UTC (4 hours ago)
(HTM) web link (codex99.com)
(TXT) w3m dump (codex99.com)
| Syonyk wrote:
| That 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 Mach 2, with passengers being served luxury
| food.
|
| > _The Air Force learned that pushing the technological envelope
| resulted in plane that was difficult to build, difficult to
| maintain, difficult to fly, and perhaps even more importantly,
| was incredibly expensive; the program cost nearly 1.5 billion
| dollars, or around 11 million dollars per flight._
|
| And nothing has changed. Pushing the limits is expensive. Always
| has been, always will be.
| mandevil wrote:
| My favorite bit of design from this era went something like
| this: "ooohhh, we need something that can handle high heat. How
| about if we made it radioactive?" and so Mag-Thor was born
| (https://en.wikipedia.org/wiki/Mag-Thor): Magnesium plus
| Thorium. It's creep resistant up to 350C! And it's only mildly
| radioactive! That's not a problem, right?
|
| Actually used on the BOMARC and D-21's ramjet engines- which is
| why you don't originals of their engines on display anywhere.
| dogma1138 wrote:
| Mag-Thor is interesting it actually has rather poor overall
| thermal characteristic compared to most metals since its
| melting point is only circa 650c pretty much the same as
| magnesium but it basically shrugs any heat upto 350-400c
| depending on the alloy so it doesn't changes its dimensions
| or becomes susceptible to mechanical deformation (it's
| basically as hard at 350c at it is at room temp). So it's
| useful but only for very specific applications unlike say
| titanium. And today we have super alloys like inconel which
| can hold back heat creep up to 650c and it's annealing starts
| at almost 900c.
| retrocryptid wrote:
| They tell the most pernicious lies about radiation.
| slow_typist wrote:
| The sheer amount of gas this plane must have carried in order
| to fulfil its mission...
| Syonyk wrote:
| Per Wikipedia, the XB70 carried: 300,000 pounds (140,000 kg)
| / 46,745 US gal (38,923 imp gal; 176,950 L), on a maximum
| takeoff weight of 542,000 lb - so about 55% of takeoff weight
| was fuel.
|
| A 747-8I carries up to 63,034 gallons, or about 400k pounds,
| on a max takeoff weight of 987,000 pounds, or about 42% of
| takeoff weight.
|
| Interestingly, the ranges are about the same. The XB70's
| combat radius (there and back) is 3,725 nm, for a straight
| line range of 7450 nm, the 747-8I's range is 7730 nm.
|
| High altitude supersonic flight is actually fairly
| efficient... if you can handle it.
| nocoiner wrote:
| Was the XB-70 capable of inflight refueling? On a quick
| look, I can't tell if that was the plan, or if it was going
| to be a one-way trip (optimistically landing in Turkey or
| something to refuel, but realistically...).
| Syonyk wrote:
| I don't believe it was capable of it, which is why it was
| so massive. The SR-71, which required inflight refueling
| repeatedly, only held 80k pounds of fuel (about 12k
| gallons). I don't have any good sense of fuel burn vs
| speed either, but in general, jets like to run high and
| fast. The old Lear 23s burned about as much fuel (pounds
| per hour) idling on the ground as they did at cruise, and
| I think the SR-71 (which mostly used the turbojets to
| keep the afterburners lit, at cruise...) fuel economy up
| high was quite good. Apparently the major problem with
| performance was keeping it from overspeeding - left to
| their own devices, the engine (... entire engine
| assembly, however long it was) was running so efficiently
| that they just wanted to _go._
| runjake wrote:
| 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 on or even seen in person, and it holds a
| certain "alternate reality" mystique for me.
| Enginerrrd wrote:
| > 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.
| bdamm wrote:
| True, but also modeling and iteration does lead you to
| unexpected solutions that can in turn solve complex problems
| that you couldn't have imagined could be solved. Landing
| rockets being an easy one, but that kind of iterative
| approach has been put to work in all kinds of fields.
| colechristensen wrote:
| One of the sources of this, which is now over, was the
| exponential increase in computing power. You could add
| complexity and your code would always run faster anyway, one
| of the popular benchmarks saw worse results on average than
| last year which never happened before. There are a lot of
| reasons for it some more speculative than others, and clearly
| computers will get faster in the future. But still.
|
| No longer can software engineers arbitrarily add bloat and
| just get away with it.
|
| https://www.tomsguide.com/computing/cpus/new-benchmark-
| shows...
| Zeetah wrote:
| 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)
| Syonyk wrote:
| > _...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.
| rqtwteye wrote:
| "Also that simplicity is king. Complexity is the enemy."
|
| That's what worries me about a lot of the shiny, super high
| tech, super expensive weapons systems of the US. These are fine
| against an overmatched enemy when you can fly back to a safe
| place for doing the necessary maintenance. This may change when
| there is a war against a capable enemy that can strike closer
| to home. The US has always had the advantage that the homeland
| was safe but that may change in the future. And once you lose a
| B-2 bomber it's very hard to replace.
| nradov wrote:
| It's literally impossible to replace a B-2 bomber: the
| production line was shut down years ago and much of the
| supply chain no longer exists. Existing B-2's (there are only
| 19 still in service) will be gradually replaced by new B-21
| Raiders.
|
| One of the long standing problems with US defense procurement
| is that they build a batch of something, then cut off all
| orders and dismantle the production line in order to free up
| funds to develop a successor model. This is tremendously
| risky because it leaves a gap of many years when it's
| impossible to replace attrition losses. 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.
| gedy wrote:
| I agree with you, but the issue afaik is that B-52 was more
| flexible whereas the B-70 was basically single purpose and
| basically obsoleted by ICBMs.
|
| B-52s were able to pivot to new roles so have stayed around.
|
| I'm humbled for us laughing at the one guy assigned to B-52
| maintenance role when was in USAF training over 30 years ago
| "That old thing? Ha!". Who would have guessed..
| runjake wrote:
| _> I 'm humbled for us laughing at the one guy assigned to
| B-52 maintenance role when was in USAF training over 30 years
| ago "That old thing? Ha!"._
|
| That guy may have been me. I was pretty bummed, but quickly
| learned about its awesomeness (avionics-wise, anyway).
| gedy wrote:
| Ha, at Lowry in 1993?
| runjake wrote:
| Yep, up until January 1993 or so.
|
| "SRAM Howell" ring a bell?
| gedy wrote:
| Ah I got there 1/93 so may have missed. I remember going
| to "fundies", getting called "pinger", etc. Good times.
| runjake wrote:
| Nobody can understand our fear of washing out and moving
| to the other side of the dorm to become a food handler
| and serving your former avionics classmates breakfast.
| This happened a lot while I was there.
| gedy wrote:
| Lol, I forgot all about that - though there were some
| cute chicks over there. I remember chatting with one
| about her upcoming French Toast test :-)
| chiph wrote:
| You may find this amusing then. I was at Travis for a day
| (from McClellan) and I had time to stop by their museum.
| They had a G model on display and there was an older
| gentleman with a child looking at it. "What kind of plane
| is this, grandpa?" "I'm not sure - I think it's a cargo
| plane"
|
| I had a really tough time resisting the urge to tell them
| the "cargo" came out the bottom.
| loloquwowndueo wrote:
| 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.
| runjake wrote:
| 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.
| psunavy03 wrote:
| > 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 consequences
| that entails.
|
| The Air Force resurrected this zombie idea (conventional
| ICBMs) in the 2000s and called it Prompt Global Strike,
| only to can it for the obvious reasons.
| kjs3 wrote:
| Not to make this thread about the B-52, the thing has been
| operational long enough for 3 generations from one family to
| fly it: https://www.dailymail.co.uk/news/article-2430802/David-
| Welsh...
| rmnwski wrote:
| 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?
| retrocryptid wrote:
| not really.
| runjake wrote:
| 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.
| aerostable_slug wrote:
| There was thought given to using 747s as cruise missile
| carrier aircraft.
|
| Each 747 CMCA would have carried dozens of AGM-86 nuclear-
| armed cruise missiles on rotary launchers that shuffled
| around the plane's cargo bay on rails (the missiles would be
| ejected one at a time from a small door near the rear of the
| fuselage).
| mrguyorama wrote:
| Which was an interesting idea, but it eventually evolved
| into a much much better one:
|
| https://en.wikipedia.org/wiki/Rapid_Dragon_(missile_system)
| lizknope wrote:
| I was watching a documentary about 20 years ago and they said
| "It may not be your father's air force but it may be your
| father's air plane."
| jiggawatts wrote:
| > 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, or cheap.
|
| I keep pointing out to people that if a real world war broke
| out, every country with a commercial wide body fleet will
| immediately convert them to bombers. Far cheaper, far simpler
| to maintain, and with much faster turnaround times / lower
| maintenance hours per flight hour.
| nradov wrote:
| It's always disappointing to see such uninformed and yet
| overconfident comments on HN. Replacing the eight small B-52
| engines with four larger ones was considered and rejected
| years ago because it would have forced much more extensive
| modifications to the airframe and other systems.
|
| https://www.twz.com/6825/engine-falls-off-b-52-during-a-
| trai...
|
| And it's extremely difficult to convert civilian airliners
| into bombers. The pressure hulls aren't designed around bomb
| bays and they lack external hard points. Even though the P-8
| is based on the 737 the design had to be extensively modified
| to accommodate weapons through a major program lasting years.
| The resulting aircraft are new production, not modifications
| of airliners.
| hi_hi wrote:
| I am in awe of anyone who worked on bringing forth such
| projects into the world. In the mean time, in my little corner
| of the world, a team of people are struggling to conjure up a
| relatively "simple" website.
| zppln wrote:
| > Also that simplicity is king. Complexity is the enemy.
|
| I don't know anything about B-52s, but I work on a project
| where we are essentially replacing a 40 year old weapon system
| with a new one. The new one should of course do the same
| things, preferably better, and do additional new things. The
| old system started out simple, but has since had most of its
| internals swapped both hardware and software wise a number of
| times. We have full access to all the documentation of the old
| system, but let's say there has been periods throughout these
| 40 years where this aspect hasn't exactly been top priority.
|
| It doesn't come as a surprise to me that projects like JSF end
| up a complete clusterfuck. Everyone tends to underestimate the
| complexity of the system they operate/produce after a while
| because most of it is always there and just works.
| CoastalCoder wrote:
| They have one at the Air Force museum in Dayton.
|
| I _highly_ recommend visiting it for anyone interested in this
| stuff. It 's an amazing museum, and it's totally free!
| ge96 wrote:
| A beautiful plane, shame those 6 engines in line is unreal to
| see.
|
| Similar vibe would be the B1-lancer for engine although in 2s
| bediger4000 wrote:
| The Wings Over the Rockies museum on the east side of Denver CO
| has a B-1A (!!!) on display. Landing gear is really tall, you
| can walk under the wings to see the engines.
| ge96 wrote:
| I watched a really cool walk around video of it on YT
|
| It's crazy it can carry as much payload as a B-52 if I recall
| right
| ben7799 wrote:
| I have a love/hate relationship with this plane.
|
| In 2014 I got to visit the AF Museum in Dayton, OH. With all the
| exceptional exhibits there it is completely obvious the XB-70 is
| THE crown jewel in that museum.
|
| And it snowed while we were visiting and they shut down the
| hangar with the XB-70 because it required a shuttle ride.
|
| So now I still have on my bucket list to see it.
| yabones wrote:
| Go back, it's so worth it. I stood under those six massive
| turbojets and looked up in absolute awe. It's a miracle that
| they didn't cut it up for scrap and left a really fabulous
| museum piece when the project ended.
| pinewurst wrote:
| Because we're not the British or Canadians who felt they had
| to make their military R&D decisions irreversible by
| destroying all the evidence (e.g. TSR2, Avro Arrow, etc).
| dangermouse wrote:
| In fact there is a TSR-2 at the Imperial War Museum
| Duxford.
| pinewurst wrote:
| It was a violation of orders as all airframes were
| explicitly ordered to be destroyed and burned.
| lizknope wrote:
| I went in 2010. Took the bus onto the air base to the
| experimental plane hangar. We only had 1 hour. I could have
| easily spent 3 hours there.
|
| I mainly wanted to see the YF-23 but here's a pic I took with a
| fisheye lens of the back of the YF-23 with the XB-70 above. I
| think they have since moved the planes to a different hangar.
|
| https://imgur.com/a/yf-23-xb-70-above-GFZDaYy
| JKCalhoun wrote:
| Always good to have a reason to return.
|
| (I tell my family that on every stop on our road trips &
| vacations.)
| wanderingmoose wrote:
| I have a love/hate relationship as well, mostly because I grew
| up within bicycling distance and spent way too much time at the
| museum.
|
| The XB-70 used to be parked outside right in front of the main
| entrance. The cool thing is they also have the X-3, which seems
| like the same design family so you can see the test article
| then the attempt at a usable aircraft.
|
| It was also the location of one of the most bonkers thing I've
| ever seen which was when they relocated an SR-71 to the museum
| and landed it on this very short old runway at the site. That
| thing was so big and so fast and that runway even at the time
| seemed so short. Here's a vid. I saw it from the road off the
| end of the threshold and it looked like it was going to hit the
| fence on the landing pass.
|
| https://www.youtube.com/watch?v=Ib1EXdIam44
| retrocryptid wrote:
| we lived in rona hills for about 4 years. not biking
| distance, but close enough to visit frequently. and as a
| youngster they let me conduct the AF orchestra there at the
| AF 25th anniversary. Very good memories.
| jghn wrote:
| The only time I went to the AF Museum was in the early 80s
| while in grade school. I still remember that thing. It was the
| coolest thing I'd ever seen. I was completely floored.
| agloe_dreams wrote:
| The AF Museum is probably the best air museum in the world. Of
| course, you have the Smithsonian in DC, but the size limits and
| general audience they expect really tones it down. You end up
| with a couple insane exhibits (Command Module, X-15, Wright
| flyer) but they all feel out of context. I actually preferred
| the annex with the Shuttle more.
|
| The AF museum is our modern history and society shown through
| the lens of the air and is insane in size.
| ferguess_k wrote:
| The Cold War era was the dream of engineers of all participant
| countries, I figured. Are we close to another one? Just wanna
| make sure it doesn't turn into a hot one.
| retrocryptid wrote:
| yup, there was just so much money flowing around. it was like
| the dot com era for aeronautical engineers and machinists.
| tqi wrote:
| "got a job with the Flight Propulsion Division of General
| Electric in Evendale (just outside of Cincinnati), initially
| working night shift in the Controls and Accessories department...
| the engine required the efforts of hundreds of engineers to
| design everything from a new turbofan and compressor, to new
| fire-suppression systems, to a special high-temperature fuel.
| Exactly what part my dad worked on is unclear; I always thought
| it was an oil pan, but my older brother was sure it was an oil
| pump."
|
| This small detail peaked my curiosity - did GE have white collar
| workers on the night shift? If so, that is super interesting to
| me.
| Aloha wrote:
| Yes, there is often manufacturing engineers on duty 24/7 and of
| course, line management.
| sgt101 wrote:
| Does anyone know why they went for six engines rather than four
| bigger ones? Was there a specific reason for that config?
| retrocryptid wrote:
| I remember seeing this beast at the Air Force 25th anniversary in
| '72 at wright pat. Pretty sure the one I saw didn't ever fly
| again.
| agloe_dreams wrote:
| The one you saw was the only one left after the insane accident
| that destroyed the other. It is still on display in Dayton.
| ellisd wrote:
| The ejection capsule design for the XB-70 is some next level
| engineering. Your seat would move backward into a capsule before
| ejection to survive the cruising altitudes of 70k feet / Mach 3.
|
| https://www.generalstaff.org/CDA/Air/B-70/XB-70_Escape_Syste...
| low_tech_love wrote:
| "...Eisenhower, the newly-elected president, was working on
| something a little bigger: a national security policy to counter
| the growing Soviet military threat in Europe."
|
| The good old days.
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