WI/PC: B-71 Blackbird

So, I was skimming the internet today, and learned that, apparently, the SR-71 was originally going to be the B-71, a high-speed penetration bomber.

I freely admit I don't know much about aircraft, but this strikes me as just immensely cool. Is there any way for this to happen? And would it actually be effective as a bomber?
 
It would be highly, highly implausible (note that even the YF-12 got farther off the ground- pardon the pun), but I could easily see perhaps two or three examples existing (YB-71) for a testing phase in much the same way as the YF-12s.

The armament would be highly limited- perhaps two to four weapons, probably missiles that would need to be specifically designed for the plane, so cost effectiveness would be incredibly low compared to the workhorse B-52s, B-58s, B-47s, and the planned B-70s, which could carry much heavier loads (and in the case of the B-70, at nearly the same speed). A B-71 would be very much a one-shot weapon- fire, go home, reload- that I doubt the USAF would commit to it when the already had the B-52s with long standoff ranges, the B-58s, FB-111s, and plans for B-70s with high speeds and much larger payloads- and on the other side, large numbers of ICBMs.

A B-71 would be somewhere between a bomber trying to be an ICBM and an ICBM trying to act like a bomber.

So sure, it's possible SAC would buy it- they had a practically unlimited budget at that point- but it's just not likely.

That said, if they did buy it, it probably wouldn't be used outside of World War Three. It's far too costly to use the thing for, say, the Gulf War- it costs a lot of money to fly the bloody things, and they don't carry much weight- a B-52 can put many times more weaponry on targets, dollar for dollar.

The YF-12 was a good idea- a very high-speed interceptor makes sense. The SR-71 was a good idea- a high-speed photorecon plane makes sense. The B-71 isn't a great idea- a high-speed bomber that only carries a couple of bombs doesn't make much sense when you've got ICBMs and plans for B-70s (which are high-speed bombers that carry quite a few bombs).
 
I think it would make a good `silver bullet` style of aircraft, a bit like the F117 and B2 have been in recent decades. They could go downtown on the first day of the war to stike at the highest value targets with specialised weaponry.
 
I recall from somewhere (can't remember where though) that the thing would only have carried maybe 4,000 lb, or 6,000 lb overload, so we're not looking at a big loadout.
 
The YF-12 was a good idea- a very high-speed interceptor makes sense. The SR-71 was a good idea- a high-speed photorecon plane makes sense. The B-71 isn't a great idea- a high-speed bomber that only carries a couple of bombs doesn't make much sense when you've got ICBMs and plans for B-70s (which are high-speed bombers that carry quite a few bombs).

Gotcha. That makes sense. Thanks!
 

CalBear

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So, I was skimming the internet today, and learned that, apparently, the SR-71 was originally going to be the B-71, a high-speed penetration bomber.

I freely admit I don't know much about aircraft, but this strikes me as just immensely cool. Is there any way for this to happen? And would it actually be effective as a bomber?


Actually, it wasn't, it was a purpose built Intel platform. There were plans to adapt the SR-71 (aka A-12, YF-71) to carry nuclear weapons. Several aircraft received the modification.
 
Skybolt, or something like it, is the easiest to imagine weapon for strike SR-71/A-12. The aircraft would do a zoom climb to Mach 3 at around 100,000 ft over Canada and deploy the weapon (without ever facing Soviet air defenses). Without air drag and with maximum rocket efficiency, the ICBM would have much better performance than a B-52-launched Skybolt, allowing for a large (or possibly MIRVed) warhead. Add in aerial refueling for loiter, and it's like a aerial, hard to hunt SLBM.

I could imagine SAC funding such a concept (if nothing else to satisfy the bomber lobby), but I agree it's a WWIII-only weapon.

Also, the B-70 would actually be better for this concept...
 
Kelly Johnson proposed it, actually with two different weapon configurations: the first had a six-round rotary launcher for SRAM missiles (under development at the time), while the second had four bays for individual weapons, two along each side of the aircraft, for B-43 gravity bombs (1 MT yield). SAC was interested in it as a low-cost alternative to the B-70, but the B-71 was another MacNamara casualty, however.
 
This basically a "can it carry bombs" question for a plane that isn't really suited for anything other than a reconnaissance role. The costs of modifying an already expensive plane would be astronomical, not to mention the maintenance costs. and besides, the B-1 Lancer and B-2 Spirit provide a much better bomber than a bomb-capable blackbird.
 
There is a cool non-nuclear option...how fast could a "dumb" bomb hit coming out at mach 3? Add the kinetic energy to the blast...and that could cause an impact. (There is the problem of guidance and having a bomb that can handle the speed...)
 
There is a cool non-nuclear option...how fast could a "dumb" bomb hit coming out at mach 3? Add the kinetic energy to the blast...and that could cause an impact. (There is the problem of guidance and having a bomb that can handle the speed...)

Top speed of the Blackbird is Mach 3.3, or a shade less than one kilometer per second. That's a ninth of a rick, meaning that it will add about 11% of the mass of the bomb in TNT equivalent. So it doesn't make much difference in energy terms.

It might make a difference for penetrating weapons like bunker-busters, either conventional or nuclear. I'm not sure how much it would help, though.
 
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There is a cool non-nuclear option...how fast could a "dumb" bomb hit coming out at mach 3? Add the kinetic energy to the blast...and that could cause an impact. (There is the problem of guidance and having a bomb that can handle the speed...)

This is more or less what I was thinking, a few hundred lumps of metal can be just as destructive, if not more, than an actualw arhead if they're going fast enough.
 
There is a cool non-nuclear option...how fast could a "dumb" bomb hit coming out at mach 3? Add the kinetic energy to the blast...and that could cause an impact. (There is the problem of guidance and having a bomb that can handle the speed...)
Given drag, I'd expect not much more than Mach 3--just an off-the-cuff guess that gravity gains offset drag losses. This means the speed would add about 0.5 MJ/kg. For TNT, this would add 12% to its effective energy density according to this Wikipedia table.
 
Ben Rich mentions that the speed built up by a mach 3.3 - 90,000ft drop projectile would approach hypersonic. My question is why would you bother when much cheaper planes can deliver the ordnance with explosives.

In my mind the spectacular performance would make a Blackbird a silver bullet plane, taking on the jobs other planes can`t in order to open the way for them as follow-on.
 
This is more or less what I was thinking, a few hundred lumps of metal can be just as destructive, if not more, than an actual warhead if they're going fast enough.
Yes, they can. The tipping point is darn close to 3 km/s, or about Mach 8.8 (at sea level conditions).
 
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