- 800°F (and above) was the temperature of their cooling air
- the engine ran too hot for electronics, so they designed a hydraulic mechanical computer responsible for regulating various inputs
- the roar from the two external 400 cubic inch Buick V8 engines originally used to start the aircraft was so irresistible to the hotrod enthusiasts running them that they sometimes neglected to disconnect in time before the starter engines overran RPM limits and "puked their guts out under the airplane" - they had to buy up so much replacement stock as to deplete every single junkyard across the USA of that particular model (so the story goes - probably hyperbole but a fun tale!)
It was not a benchtop unit, it was a forklift model :\
[0] https://www.thesr71blackbird.com/Aircraft/Engines/starting-t...
There was a proposal at one point for NASA to deploy a 21st-century automaton to Venus because the atmosphere is too corrosive for an electronic computer. Supposedly it would have delivered its data to an orbiter using a balloon and then the orbiter transmits the information over radio. I really wish they'd do that, I would love to see what could be done with mechanical computing using modern technologies.
Unfortunately there aren't a whole lot of situations where clockwork logic makes more sense than semiconductors.
NASA asked several former SR-71A staffers to help secret restart - https://news.ycombinator.com/item?id=49890733 - Sept 2026 (401 comments)
https://news.stanford.edu/stories/2016/06/cooperation-u-s-ru...
The balloon issue cannot be addressed by any modern US aircraft, and spending expensive missiles on low cost balloons seems like wasting money and resources.
We'll know soon.
If we're spitballing solutions, balloons are slow, fragile and move in relatively predictable paths. An F-15 could reach the same altitude, and launch it's own balloon with a small solid-fuel booster that also corrects the trajectory. If the interceptor balloon could get within 1-2km of the target balloon, then a cheap kinetic weapon firing HEI projectiles might be enough to destroy it.
https://en.wikipedia.org/wiki/McDonnell_Douglas_F-15_Eagle
That is the lower bound of what modern high-altitude balloons can reach. Back in 2023 multiple balloons were observed much higher than that up to 50,000 feet.
https://en.wikipedia.org/wiki/List_of_high-altitude_object_e...
This is still in the lower spectrum for such balloons. BS 13-08 reached 176,000 feet back in 2013 (there is reason to believe spy balloons would not go that high though).
https://en.wikipedia.org/wiki/High-altitude_balloon
So, you're wrong. There is no US aircraft that can reach them (unless they drop low as they did in 2023). The US likely wants to hit them before they go low.
The SR-71 is uniquely suited for this task, having reached up to 90,000 feet during testing. It was specially made for some kind of hybrid space war possibility (not balloons, but something high up there).
Service ceiling: 65,000 ft (20,000 m)
That's high enough to go 15k feet above the highest ballon mentioned in the second link you provided, which was 50,000 feet.
Also, the SR-71 carried no weapons, only cameras, and re-tooling to support them would be far more expensive than merely shooting a balloon with a missile from the ground (or building an air-to-air missile that can be fired from existing platforms at altitudes like 65k feet).
The SR-71 already flew in the configuration I mentioned. It's the YF-12C (a converted SR-71).
Recovering and converting another sure is more expensive than one missile, but it's a reusable platform.
A ground missile able to reach those balloons is more expensive than a modernized SR-71 sortie. High-altitude, precision missiles are also not allocated for this task. China can launch dozens of balloons for cheap, and spending one multi-million-dollar missile on each is insanity. Even the long range air-to-air ones are too expensive for that.
The SR-71 (as a new YF-12D interceptor) makes more sense. It can take multiple balloons in one flight with cheap shorter range air-to-air missiles (or maybe even cheaper weapons, for a balloon a laser would do), then go home and do that over and over again.
I can't rule out that Issacman does have this mission profile in mind, but it seems contrived. Whatever weapon the SR-71 could carry to-altitude could be be done cheaper, more numerously and probably more quickly too with F-15s. Refurbishing a fleet of SR-71s and a fleet of KC-135Qs would be a lot of work for an extremely limited capability.
It does sound like a lot of work, but that's the part of the puzzle that is not a mystery. Someone is in fact putting one of those back to work, we just don't know why.
That likely concentrated the discussions towards this single idea I presented. However, I'm not actually that committed to it. If you have any other, I would very much would like to hear about it.
This is a NASA/JPL project; there are a limited number of airworthy SR-71s, they are not modernized for combat, and they cannot scramble to intercept. The M-21 variant has a well-documented conversion to a mothership[0] that can ferry payloads externally to-altitude and at high speed. This is incredibly ideal for testing captive ramjet/scramjet technology, since they require Mach 3+ speeds to attain ram pressure through the engine.
Sending the SR-71 into denied or uncontrolled airspace seems like a terrible idea, in 2026. Chinese and Russian naval interceptor missiles could shoot down the plane at it's maximum speed and altitude; it's not going up against 1980s missiles anymore. The risk is absurd, and there's not enough SR-71s to treat them like they're expendable.
There has been some speculation about this outside this thread though:
https://theaviationist.com/2026/09/23/nasa-chief-teases-myst...
I don't know how credible those reports are, but Jared Isaacman's comments do suggest more than just a testbed. Do you have any comment on that?
https://theaviationgeekclub.com/how-the-f-15-streak-eagle-br...
By "same altitude" I was referring to the SR-71. I do not know what the payload capacity was for either aircraft in the 90,000ft testing conditions, but for interception missions there are more important metrics.
Unit mix up?
The f-16 however, does have a surprisingly low ceiling, there are fighter pilot memes about it. https://www.youtube.com/watch?v=koEQp8ImlnI?t=643 something about having small wings, get above 30,000 feet and it's not happy.
High-altitude balloons are hardly a new threat. They have been used for decades, although some recent Chinese models are more capable than before. Regular tactical aircraft already in the US inventory are perfectly capable of shooting them down.
https://www.af.mil/News/Article-Display/Article/3288579/f-22...
SR-71 or not, there are already contracts for filling this niche:
https://www.war.gov/News/Contracts/Contract/Article/4613098/... (search for "swamp gas").
If money is flowing to counter/develop high-altitude balloons and declared as urgent, it's likely it's flowing in more than one vein.
The frame modifications you mentioned are already specified and tested, part of the YF-12 programme. It can easily carry air-to-air missiles instead of reconnaissance equipment, and the frame has flown with that configuration.
The YF-12 prototypes looked superficially similar to the SR-71 but had substantially different airframes. There is simply no place in an SR-71 to mount the necessary weapons, sensors, and avionics without completely rebuilding the entire aircraft. That would be a stupid waste of resources when existing platforms can already accomplish the mission well enough.
You might be confusing the YF-12 with the A-12, which is related but a significantly different airframe.
I won't engage in discussing whether balloons are high priority or not. Let the 2023 events and the funding towards those areas speak for themselves.
You might be confusing the fake YF-12C with the real YF-12A. Both designs were derived from the original A-12 and look superficially similar but are internally quite different. There is no practical way to modify an SR-71 to carry and employ weapons. I mean it would be like trying to convert an F/A-18F into an F/A-18G: not technically impossible but so complex and expensive as to be utterly pointless. If the SR-71 ever actually flies again it will be used for nothing more than aerodynamic tests.
> Ultimately, 935 became the workhorse of the program, with 146 flights between 11 December 1969 and 7 November 1979. The second YF-12A, 936, made 62 flights. It was lost in a non-fatal crash on 24 June 1971. It was replaced by the so-called YF-12C (SR-71A 61-7951, modified with YF-12A inlets and engines and a bogus tail number 06937).
Is a missile a form of aircraft? Because there's variants of the Standard Missile which can hit a low earth orbit satellite, with the right timing, fired from effectively zero velocity and at sea level from a frigate.
I mean, you can do that, but it would be a tremendous embarrassment.
No it's not. And it's indeed very costly. But on the grand scale of things of what the US DoD spends per day as a fully loaded lifetime cost to operate a single SSN, SSBN or aircraft carrier, it's a drop in the bucket. They spend absurd amounts of funds on all sorts of things.
Also, approaching the balloon in stealth with a plane that has its own radar system is considerably less paraphernalia than ships chasing balloons.
I could be wrong about how the SR-71 will be used, but I'm very sure using expensive missiles designed for much more advanced threats to take out balloons is insanity.
As of today it's not possible to mount a laser on a tactical aircraft (or SR-71) capable of destroying a balloon. There isn't enough space or power available. Perhaps that will change soon but for now it remains science fiction.
- Reusable/non-reusable
- Cost/range
The machine gun and laser are illustrative examples. I offered a cheaper short range missile as an option too, if those two bother you.
At some point, I believed you got carried away by specific details about aerodynamics and laser payload (you are probably right!), but are ultimately irrelevant for the progression of the conversation: if you are closer, you can use a cheaper weapon.
It's normal to get carried away (I do it all the time), and I'm fine with having my comments broken down and dissected. However, there are aspects of what I said that weren't answered, so they still stand.
But in general all of your comments here have been deeply uninformed about how this stuff actually works.
This is a low stakes brainstorming conversation, I presented my ideas as hypotheticals and shared my sources.
Honestly, I was hoping someone more knowledgeable would share any better insight on what the recently work on the SR-71 frame would be used for in practice. That hasn't happened so far, but that's fine.
"Your guess is bad because using the SR-71 for _____ in missions such as ______ would make more sense" would be stellar brainstorming about this beloved fan favorite.
The loadout will be like an F-15 with just one or two AIM-7 type missiles of appropriate generation and maybe the center tank. You configure and fly the plane to the altitude as usual, then when instructed, push the throttle all the way forward, do a shallow dive, then pull up to the precise absurd angle as you were briefed and keep it there. The number on the right go crazy and the number on the left goes down slightly less faster. At some point, you will see an angled rectangle with a dot in the center, itself in the center of a large circle on the HUD, and it says SHOOT, so you pull the trigger. You here the thunk of missile leaving, then nothing happens for 30 seconds, and the radio says target radar contact lost as expected, you do a 180 roll into a shallow dive and go home.
I mean, that's how I as an armchair flightsim pilot think it'll go, but I'm sure this wouldn't be way off. Attempting the same with a gun installed on a Blackbird? That's just waste of everything from time of everyone involved to your own life.
I second the fact that the M21 is awesome though.
a) Some clearly preposterous order that originated with the demented commander in chief, and they're just going through the motions. Same concept as ordering steam catapults put back on aircraft carriers.
or
b) Intentional misdirect/bait to send various groups of people off in a wrong direction as cover for something else entirely.
This differs from 'a' in that the decision is not humoring the momentary whim of a mad dictator, but an a deliberate decision by a group of professionals (at least in theory), who have destroyed any possible means of connecting themselves with real information.
So this led to the obvious question: why didn't we just recreate the F1 engine and the Saturn V? It turns out there were lots of reasons:
1. Materials science has changed. You can't necessarily make the same materials you made back then. And substituting them might have consequences on certification and testing that would make it much more expensive than a simple recreation;
2. We didn't necessarily know how to. Surprising as it sounds, the Saturn V program was pretty rushed. The engines and rockets were essentially handcrafted. Lots of things were documented but not necessarily everything. Even if it was, has that documentation been lost?
3. Loss of expertise. There's probably hardly anybody left who made those engines. Any complicated production line relies on reinforcing and building expertise through training and repetition. You'd have to build that from scratch. This is a common problem with any major weapons program. As soon as you stop making a particular weapon, it's almost impossible to restart it very quickly;
4. We don't necessarily have all the machining and secondary processes that existed then;
5. Advances in technology mean we can do better things now. For example, we can 3D print parts that we had no way of making them previously. It simply wasn't possible. This has come up in commercial aviation where modern aircraft (eg 787/A350) and their respective engines make heavy use of 3D printed parts, something the 747 could never have possibly have done;
6. Even if you can make all a complete system, what's your production capacity? The capacity for Saturn V rockets was quite low and because it was essentially bespoke, it couldn't be scaled. One of the impressive things about the Falcon 9 system is just how many of those rockets SpaceX could produce, even before extensive reuse of first-stage boosters. Capacity is something that almost has to be built in from scratch and it impacts everything. For example, a bunch of weapon systems have been depleted by the Iran War (eg Patriot interceptors, Tomahawks). You can't just turn a knob to ramp up production meaningfully. And where you can, it's incredibly expensive.
This is also a big part of China's current manufacturing advantage. There's an awful lot of standardization and regional specialization. You need a part? The factory that makes it is probably down the road. So certain things get made in Shenzhen because everything you need is also made in Shenzhen. This also means you can react very quickly, something a factory in the US could never do because it lacks that ecosystem.
They discovered all sorts of weird things when they made the original Blackbird. For example, titanium is so hard that they had to use special tools to machine parts like the panels. Well, in doing so they discovered that using cadmium in some tools to make them operate at higher temperatures and against harder materials would "poison" the titanium fatally.
So if you built a new hypersonic airframe now, would you use titanium? Do we have better alloys? We've had a lot of advances in single-crystal manufacturing for metals that have, for example, made jet engines incredibly reliable. And this btw is something China has had massive difficulties reproducing, at least for now. And they've spent decades trying.
As a simple example of this, there was a guy who went out of his way to make an electric toaster from scratch [1]. This is a relatively simple device but it shows how many inputs there are, which each have production lines (eg steel, aluminum and/or plastic). Now imagine what goes into a military plane that needs to fly at Mach 3-4.
[1]: https://www.ted.com/talks/thomas_thwaites_how_i_built_a_toas...
The SLS started in 2011. 15 years later, it finally managed a manned flyby. The entire program has generally been an endless series of errors and mishaps, and the Moon flyby probably should never have happened, but was greenlit for political/managerial reasons - highly reminiscent of Columbia and Challenger, but with a better outcome owing purely to good fortune.
Not only has it been an endless series of mishaps over an increasingly absurd timeframe, but the program has already been obsoleted by the Falcon Heavy, to say nothing of the ongoing development of Starship. It has a lift capacity of about 50% more than the Falcon Heavy, but one SLS launch costs as much as 40 Falcon Heavy launches, so it's existence just doesn't make any sense, at least not as a space launch system.
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It seems likely that NASA would have been much better advised to have simply revived the Space Shuttle or perhaps even further back rather than trying to do something from scratch, simply because when you do it from scratch you end up trying to iterate on top of something that you no longer necessarily have the expertise or human knowledge of how to create.
I think where intuition fails a lot of us (myself included) is that in the software world if you have the code/documentation for something then building it is trivial. But in the hardware world, even if you have all the instructions and knowledge, actually applying that know how to create a working project is still very far away, through certainly nowhere near as far away as if you have started from scratch.
The SR-71 won't because there's no JP-7 supplier, no flyable KC-135T, and no parts.