I almost skipped the videos embedded in this article, but they are well curated gems. A few tidbits I found amazing:
- 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!)
> the engine ran too hot for electronics, so they designed a hydraulic mechanical computer responsible for regulating various inputs
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.
In the one that I'm familiar with, they put the battery and all electronics in the part of the probe that sticks inside the meat so that the temperature of that part never exceeds ~212F. The part that sticks out and gets really hot is probably just an antenna.
A clever design to be sure, but still a long way from electronics that can survive anything near your typical oven temperature, much less the surface of Venus.
ThermApens go way higher (500+) but they don't have batteries or wireless electronics in the probe. The discussion is regarding wireless temperature probes.
Their lander was destroyed shortly after landing and only sent a few images. If you wanted something that could last it would need to be designed to handle that atmosphere
I remember quite well the day the auctioned off a unique "jet fuel analyzer" that was used to do some of the specialized testing for these exact aircraft.
It was not a benchtop unit, it was a forklift model :\
While europeans tend to celebrate engines/cars designed for the rich, Americans tend to celebrate engines/cars designed for everyone. Accounting for inflation, the car those engines came in (the 1969 Buick GS 400) sold for ~$30k in today's dollars. For comparison a similarly powerful 1969 Aston Martin DBS V8 sold for the equivalent of $126k today.
A handful of the surviving planes are in museums. If you're at all interested in aviation and have the chance to see one, do. There's something special about them that doesn't come across in pictures.
The Seattle museum is really amazing, i went last year. The tour guides at the museum are retired Boeing and military guys, they got a real kick out of my 14 year old's questions and knowledge of cold war era SAM systems (mostly from playin g DCS) haha.
When I visited in 2018, one of the guides was a retired astronaut. I completely failed to have a conversation with him as I was star-struck and barely managed to hold a door open for him without making a fool out of myself.
Big shout out to the Udvar Hazy Center in Chantilly, Virginia which has both an SR-71 and the Discovery Space Shuttle, as well as a bunch of other really interesting aircraft.
While i haven't seen SR-71, i have been to the Beaulieu Motor Museum (pronounced "byoolee" fyi). They have a land speed record hall. Those machines also have a presence. It is as if they are projections from the noosphere into the realm of physical stuff.
I wonder for such abandoned projects with non existent supply chain/know-how/documentation, whether there is any benefit of trying to revive them instead of starting from scratch.
I think we can look to the SLS [1] for the answer there. It was basically NASA's answer to (amongst other things) get to the Moon in a kind-of-new way. For some historical context we first man a man in orbit in early 1962, so that was just barely starting to appreciate the systems involved in space. Kennedy would give his 'To the Moon' speech in late 1962. We'd then land a man on the Moon less than 7 years later.
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.
> 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.
It's certainly true that you can build software if you have the code (well, mostly true. Modern frameworks suffer from quite severe bitrot). But I'm not sure that you can extend it.
Large software projects rely on people understanding them. If everyone who worked on the project is gone, it's very hard for someone to regain the architectural understanding required to extend or refactor things. Without any overlap, there's nobody to answer questions. As long as there's been a continuously overlapping stream of developers, that knowledge is more or less retained - but if all the developers leave, and someone picks up the project again later it's almost impossible for them to make meaningful improvements.
Lunar Landers aren't particularly large. Both the SLS and Falcon Heavy support comparable payload sizes (dimensions). As for mass, the Falcon Heavy supports 64 tons to orbit. They haven't advertised a mass to the Moon, but they have advertised 17 tons to Mars, and it requires a bit more juice than the Moon to get to.
The Lunar Module had a fueled mass of 16 tons. So the Falcon Heavy would be perfectly suitable. And that's without anything fancy like in-orbit refueling, modular designs, etc.
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.
I wouldn't leave out: c) The rot has become so pervasive, in the manner of the late Soviet Union, that the people issuing the orders are completely disconnected from the reality on the ground.
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.
> who have destroyed any possible means of connecting themselves with real information.
See: Special Military Operation. It was always surprising to me that the Russians essentially repeated the same mistakes from the first Chechen war after seemingly learning from them by the early 2000s
Unfortunately you might be out your good money, as the more plausible explanation is that current NASA administrator Jared Isaacman loves restoring & flying old airplanes (see https://en.wikipedia.org/wiki/Draken_International) and who wouldn't love restoring something as iconic as the SR-71?
I feel like passion projects can be worth it. You’d want passion, and to attract people who want to work on cool stuff and do difficult or impossible things just because they’re hard or fun.
Let them do that without taxpayer money! If NASA announced, "We're looking for investors to revive our SR-71: for $10 million you get a sticker with your logo in the cockpit and for $50 million you can have a ride." I'm sure they'd have plenty of takers.
Up until relatively recently, the Saturn V (and the F1 engine) was the most powerful rocket ever made, even though it's almost 60 years old. Now I believe both SLS and Starship are more powerful.
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.
I’m sure it’s been mentioned a few times in the older thread that came up the other day but I can only recommend the book by Ben Rich, Skunk Works, if you want learn more about how this plane came to be.
In the 90s, NASA refurbished and extensively modified a mothballed supersonic Soviet-era Tu-144. The modifications included fitting different (Tupolev) engines. The total cost was $350M. It was used as a flying laboratory.
Guessing this project was also a way to pay Russian engineers while the Soviet Union collapsed with the goal to do "technology transfer" and prevent them from working for NK and the like as a way to make ends meet.
Yep. After the collapse of the USSR, the US Congress and NASA funded the International Space Station program in part to keep Russian rocket scientists gainfully employed. That way they wouldn't be tempted to go work for Iraq / Iran / North Korea / China.
When I see this, I can only think of modern high-altitude balloons. My gut tells me the SR-71 would be an ideal interceptor for that new threat (despite not being an interceptor itself).
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.
The SR-71 was never designed as an interceptor, and would require extensive modifications to carry and employ weapons. Not going to happen. There was an earlier YF-12 interceptor program but it never proceeded beyond the prototype stage.
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.
Current aircraft is not capable of reaching those balloons, read my other commentary. Your link points to a Chinese balloon that dropped way below its operational range.
SR-71 or not, there are already contracts for filling this niche:
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.
> Current aircraft is not capable of reaching those balloons
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.
Yes, certain variants of the SM-3 (RIM-161) have a limited anti-satellite capability. And in general any current Standard missile could potentially be employed against a spy balloon depending on the exact engagement parameters. The problem is that they have limited range and it can be tough to get a launch platform to the right place at the right time to generate an intercept. The Navy surface fleet is already over committed, and ground based launchers have limited mobility. Hence it's more practical to use tactical aircraft like the F-22 or F-15EX for this type of homeland defense mission.
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.
I don't know which weapon would be used. A laser or a machine gun can take out a balloon if you're close enough. Even if missiles are used, closer range air-to-air are cheaper.
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.
You seem to be confused about basic aerodynamics. At those altitudes, attempting to shoot a balloon with a machine gun would be insanity. The high wing loading limits maneuverability so severely that the shooting platform would risk running into target debris.
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.
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.
When regular F-22s were already used to shoot down Chinese spy balloons they employed AIM-9 missiles, which are cheaper than AIM-120. But there's no need to get particularly close: in fact for safety they want to remain well separated from the target and never get on a collision course.
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.
You can't gun kill a balloon floating at 60k feet. That's not going to work. It has to be with an active or semi-active radar homing missile.
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.
Militarily, it's the lowest-flying and the most maneuverable spy satellite with a turning radius comparable to the size of an European mini/microstate. That's it.
Just speaking from a couch, maybe it's a simple 50:50 between the NASA administrator just wanting it flying and Boom Supersonic not doing fantastically. Anduril's mini F-16 drone having its air intake painted out in photos also comes to mind. Lessons learned by NASA from an SR-71 engine project is going to be invaluable for new entrants to supersonic planes and engines.
The only thing it was designed for: recon. It's a spy plane. It has cameras and electronics up the wazoo. You fly it high and fast over a target, collect the info you need, refuel it and change target. Unlike a satellite, you can do that many times per day.
Against the USSR it had become risky because missiles could reach it? And satellites worked great during the cold war. But in a scenario where things got hotter and you wanted regular fresh intel from deep within enemy territory, the SR-71 could be irreplaceable.
AIM-120 range and altitude upgrades have been in the works for many years, and balloon defense is a relatively low priority mission. It will also be supplemented by the new AIM-260 which has greater capabilities. The primary goal of those programs is to achieve greater stand-off range versus near-peer adversary aircraft.
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.
What are you talking about? The "YF-12C" designation was not a combat aircraft. It was a fake designation slapped on a regular SR-71 that NASA used for flight testing in order to hide the secret origins of the program. There was never a real YF-12C.
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).
And possibly too slow to be safe from space weapons from escort satellites protecting balloons, or too slow and clumsy for combat missions of any kind.
The service ceiling of the SR-71 is still well beneath the altitude of a modern balloon. The speed isn't necessary, and it's altitude record has been beaten by other modern jets.
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.
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.
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).
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).
You misread your source: the F-15 can climb 30,000 feet in 60 seconds - the service ceiling is closer to 60,000 feet officially, and 90,000 under ideal conditions:
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.
Per the first link you provided, the F-15 has the following:
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).
Fair correction on the altitude (still in the lower bounds of the balloons, as I mentioned).
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.
China can launch a lot more than a dozen balloons, perhaps thousands if convincing decoy payloads can be made. The A-12 was intended to counter high-value targets in a limited number, not low-value targets en-masse.
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.
F-15s are not stealth. You don't want to risk escalation by sending fighter jets towards someone else's airspace. To me, they don't make sense for this kind of mission.
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.
I'm missing something - why would you be wanting to intercept balloons over someone else's airspace? The 2023 incident was in US (and Canadian) airspace.
Sorry, I should have explained it: you want to intercept a spy balloon before it enters your airspace, not after it has already entered and possibly gathered any information.
Well there's a whole lot of ocean one doesn't need to be stealth to fly over but really, your comments read like endless goal-post shifting from someone who has a preferred solution in mind and is working backwards to justify it. Also the SR-71 was never stealth, only reduced observability. The USSR was very aware of the overflights taking place.
It seems no one else offered any other concrete uses that would justify the efforts that went public regarding the frame reuse.
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.
I don't have access to any privileged information, here. My best bet is that DARPA is lighting a fire under JPL's ass to explore variable-cycle engine technology: https://en.wikipedia.org/wiki/Variable_cycle_engine
The US has tested ramjets before, but mostly in the context of missiles and boost-glide vehicles. The "holy grail" of efficient propulsion would be to taxi/accelerate with a turbofan engine, bypass into a ramjet for Mach 3-to-6ish, and then transition to a liquid-fuel rocket motor for the last Mach 6-10 climb. An engine like that could escape the Earth's atmosphere without sacrificing efficiency at lower altitudes. I realize that "space fighter engine" is also a longshot, but China has ramped up investment in variable-cycle technology quite a bit in the past 2 years. Simply solving the turbofan-to-ramjet transition would be a huge boon for high and fast flight.
Issacman's quotes in that article suggest, to me, that he wants to reboot the SR-72 program (or something similar) with cleansheet propulsion as a feature. The SR-71 could be the engine testbed, and a future airframe could be designed around the requirements of the engine. Just my $0.02 though.
Your amounts are off. that wikipedia page lists the f-15 as having a service ceiling of 65,000 feet. Perhaps irrelevant but a f-15 shot a satellite down once(not relevant because that is more the missiles capabilities than the planes, which is probably the relevant point)
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.
I almost skipped the videos embedded in this article, but they are well curated gems. A few tidbits I found amazing:
- 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!)
For those that want to know more about the Buick engines and their replacement, here's [0] a writeup about it.
[0] https://www.thesr71blackbird.com/Aircraft/Engines/starting-t...
And to hear it in action, https://www.youtube.com/watch?v=JjdyQpEUYzI
> the engine ran too hot for electronics, so they designed a hydraulic mechanical computer responsible for regulating various inputs
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.
Don’t we have some better high temp electronics now? I have a Bluetooth meat thermometer that works up to like 600F.
In the one that I'm familiar with, they put the battery and all electronics in the part of the probe that sticks inside the meat so that the temperature of that part never exceeds ~212F. The part that sticks out and gets really hot is probably just an antenna.
A clever design to be sure, but still a long way from electronics that can survive anything near your typical oven temperature, much less the surface of Venus.
Indeed. As a corollary of this design, trying to use the tip of such a thermometer to gauge frying oil temperature will kill it pretty much instantly.
I use a Thermopen almost daily to check fry temperatures. I don't go above 400º F however.
ThermApens go way higher (500+) but they don't have batteries or wireless electronics in the probe. The discussion is regarding wireless temperature probes.
what I’m getting from this is that we need to send our space probe to venus encapsulated inside a steak :)
We do! https://arstechnica.com/science/2017/02/venus-computer-chip/
there are photos from the surface of Venus from the Soviet Union's landings. They are online.
Their lander was destroyed shortly after landing and only sent a few images. If you wanted something that could last it would need to be designed to handle that atmosphere
I remember quite well the day the auctioned off a unique "jet fuel analyzer" that was used to do some of the specialized testing for these exact aircraft.
It was not a benchtop unit, it was a forklift model :\
400 cubic inches for 401 horsepower each. Pushrods, two valves a cylinder.
This is nothing to celebrate.
While europeans tend to celebrate engines/cars designed for the rich, Americans tend to celebrate engines/cars designed for everyone. Accounting for inflation, the car those engines came in (the 1969 Buick GS 400) sold for ~$30k in today's dollars. For comparison a similarly powerful 1969 Aston Martin DBS V8 sold for the equivalent of $126k today.
If gas prices in the US were like the rest of the world, only rich people could afford to drive a car with a 400 cubic inch engine.
Back then, one horsepower per cubic inch was a worthwhile benchmark, something automakers bragged about.
US automakers, sure.
A handful of the surviving planes are in museums. If you're at all interested in aviation and have the chance to see one, do. There's something special about them that doesn't come across in pictures.
I'd second that. I saw the surviving M-21 in Seattle. The highlight of the visit. If you get the chance, well worth your time
The Seattle museum is really amazing, i went last year. The tour guides at the museum are retired Boeing and military guys, they got a real kick out of my 14 year old's questions and knowledge of cold war era SAM systems (mostly from playin g DCS) haha.
When I visited in 2018, one of the guides was a retired astronaut. I completely failed to have a conversation with him as I was star-struck and barely managed to hold a door open for him without making a fool out of myself.
I second the fact that the M21 is awesome though.
Big shout out to the Udvar Hazy Center in Chantilly, Virginia which has both an SR-71 and the Discovery Space Shuttle, as well as a bunch of other really interesting aircraft.
While i haven't seen SR-71, i have been to the Beaulieu Motor Museum (pronounced "byoolee" fyi). They have a land speed record hall. Those machines also have a presence. It is as if they are projections from the noosphere into the realm of physical stuff.
Also a Porsche 917. Incredible collection.
The Pima Air and Space museum in Tucson Arizona is incredible and has a SR-71. Highly recommend.
I wonder for such abandoned projects with non existent supply chain/know-how/documentation, whether there is any benefit of trying to revive them instead of starting from scratch.
I think we can look to the SLS [1] for the answer there. It was basically NASA's answer to (amongst other things) get to the Moon in a kind-of-new way. For some historical context we first man a man in orbit in early 1962, so that was just barely starting to appreciate the systems involved in space. Kennedy would give his 'To the Moon' speech in late 1962. We'd then land a man on the Moon less than 7 years later.
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.
[1] - https://en.wikipedia.org/wiki/Space_Launch_System
> 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.
It's certainly true that you can build software if you have the code (well, mostly true. Modern frameworks suffer from quite severe bitrot). But I'm not sure that you can extend it.
Large software projects rely on people understanding them. If everyone who worked on the project is gone, it's very hard for someone to regain the architectural understanding required to extend or refactor things. Without any overlap, there's nobody to answer questions. As long as there's been a continuously overlapping stream of developers, that knowledge is more or less retained - but if all the developers leave, and someone picks up the project again later it's almost impossible for them to make meaningful improvements.
AI probably changes this completely.
" 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"
I don't think they can make do with reduced capacity by splitting a lunar lander between 2 Falcon Heavy launches and assembling it in space.
Lunar Landers aren't particularly large. Both the SLS and Falcon Heavy support comparable payload sizes (dimensions). As for mass, the Falcon Heavy supports 64 tons to orbit. They haven't advertised a mass to the Moon, but they have advertised 17 tons to Mars, and it requires a bit more juice than the Moon to get to.
The Lunar Module had a fueled mass of 16 tons. So the Falcon Heavy would be perfectly suitable. And that's without anything fancy like in-orbit refueling, modular designs, etc.
I would bet good money it's one of two things:
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.
I wouldn't leave out: c) The rot has become so pervasive, in the manner of the late Soviet Union, that the people issuing the orders are completely disconnected from the reality on the ground.
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.
> who have destroyed any possible means of connecting themselves with real information.
See: Special Military Operation. It was always surprising to me that the Russians essentially repeated the same mistakes from the first Chechen war after seemingly learning from them by the early 2000s
Unfortunately you might be out your good money, as the more plausible explanation is that current NASA administrator Jared Isaacman loves restoring & flying old airplanes (see https://en.wikipedia.org/wiki/Draken_International) and who wouldn't love restoring something as iconic as the SR-71?
What a waste of extremely limited resources at NASA, then.
The administrator just wants to fly it around? Seriously?
What a joke.
I feel like passion projects can be worth it. You’d want passion, and to attract people who want to work on cool stuff and do difficult or impossible things just because they’re hard or fun.
Let them do that without taxpayer money! If NASA announced, "We're looking for investors to revive our SR-71: for $10 million you get a sticker with your logo in the cockpit and for $50 million you can have a ride." I'm sure they'd have plenty of takers.
> attract people who want to work on cool stuff and do difficult or impossible things just because they’re hard or fun
Then make them work on fixing the healthcare. NASA is using its budget to keep 25 MiG-21 ariplanes fly worthy? It doesn't make any sense.
NASA isn't keeping 25 MIG-21 flying, Draken is, as a contractor providing dissimilar aircraft training to the US military (and other nations).
As a joke (d), Isaacman wanted to confirm whether the first “A” still stood for “aeronautics”.
Up until relatively recently, the Saturn V (and the F1 engine) was the most powerful rocket ever made, even though it's almost 60 years old. Now I believe both SLS and Starship are more powerful.
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...
Recent and related:
NASA asked several former SR-71A staffers to help secret restart - https://news.ycombinator.com/item?id=49890733 - Sept 2026 (401 comments)
I’m sure it’s been mentioned a few times in the older thread that came up the other day but I can only recommend the book by Ben Rich, Skunk Works, if you want learn more about how this plane came to be.
In the 90s, NASA refurbished and extensively modified a mothballed supersonic Soviet-era Tu-144. The modifications included fitting different (Tupolev) engines. The total cost was $350M. It was used as a flying laboratory.
Guessing this project was also a way to pay Russian engineers while the Soviet Union collapsed with the goal to do "technology transfer" and prevent them from working for NK and the like as a way to make ends meet.
Yep. After the collapse of the USSR, the US Congress and NASA funded the International Space Station program in part to keep Russian rocket scientists gainfully employed. That way they wouldn't be tempted to go work for Iraq / Iran / North Korea / China.
The US also employed Soviet nuclear scientists for similar reasons.
https://news.stanford.edu/stories/2016/06/cooperation-u-s-ru...
Neither the SR-71 nor F-14 will fly again without significant funding, and not for any economically-viable use.
The SR-71 won't because there's no JP-7 supplier, no flyable KC-135T, and no parts.
No Top Gun movie series then. :)
I think Ken Shirriff, CuriousMarc and friends need a new project to step it up now they have their Apollo systems all running like new. :)
Ha ha, that would be a fun project. We might need a bigger basement, though :-)
This is probably one of the coolest planes and it's SOP is to leak fuel until it gets going enough that the heat seals it's seams due to expansion
Particularly toxic boron-enriched fuel at that, to sustain those same high temperatures.
https://en.wikipedia.org/wiki/JP-7
The engine cores alone expand 6” when they heat up.
Half expecting this Administration to crash and destroy the remaining inventory.
When I see this, I can only think of modern high-altitude balloons. My gut tells me the SR-71 would be an ideal interceptor for that new threat (despite not being an interceptor itself).
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.
The SR-71 was never designed as an interceptor, and would require extensive modifications to carry and employ weapons. Not going to happen. There was an earlier YF-12 interceptor program but it never proceeded beyond the prototype stage.
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...
Current aircraft is not capable of reaching those balloons, read my other commentary. Your link points to a Chinese balloon that dropped way below its operational range.
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.
https://en.wikipedia.org/wiki/Lockheed_YF-12
> Current aircraft is not capable of reaching those balloons
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.
Yes, certain variants of the SM-3 (RIM-161) have a limited anti-satellite capability. And in general any current Standard missile could potentially be employed against a spy balloon depending on the exact engagement parameters. The problem is that they have limited range and it can be tough to get a launch platform to the right place at the right time to generate an intercept. The Navy surface fleet is already over committed, and ground based launchers have limited mobility. Hence it's more practical to use tactical aircraft like the F-22 or F-15EX for this type of homeland defense mission.
Well, it's not reusable. You're wasting a resource destined for hypersonic deterrence on some sheets of mylar that float around.
I mean, you can do that, but it would be a tremendous embarrassment.
> Well, it's not reusable
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.
Perhaps the issue is not money, but production capacity? Those take some time to build, and you don't want to deplete your stockpile on spy balloons.
missiles shot from fighter jets aren't reusable either, and ships that fire those missiles are as reusable as jets
I don't know which weapon would be used. A laser or a machine gun can take out a balloon if you're close enough. Even if missiles are used, closer range air-to-air are cheaper.
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.
You seem to be confused about basic aerodynamics. At those altitudes, attempting to shoot a balloon with a machine gun would be insanity. The high wing loading limits maneuverability so severely that the shooting platform would risk running into target debris.
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.
The conversation goes as follows:
- 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.
When regular F-22s were already used to shoot down Chinese spy balloons they employed AIM-9 missiles, which are cheaper than AIM-120. But there's no need to get particularly close: in fact for safety they want to remain well separated from the target and never get on a collision course.
But in general all of your comments here have been deeply uninformed about how this stuff actually works.
I appreciate the heads up.
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.
You can't gun kill a balloon floating at 60k feet. That's not going to work. It has to be with an active or semi-active radar homing missile.
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.
Makes sense. You seem to know a lot of stuff! What do you believe the SR-71 frame is going to be used for?
Militarily, it's the lowest-flying and the most maneuverable spy satellite with a turning radius comparable to the size of an European mini/microstate. That's it.
Just speaking from a couch, maybe it's a simple 50:50 between the NASA administrator just wanting it flying and Boom Supersonic not doing fantastically. Anduril's mini F-16 drone having its air intake painted out in photos also comes to mind. Lessons learned by NASA from an SR-71 engine project is going to be invaluable for new entrants to supersonic planes and engines.
The only thing it was designed for: recon. It's a spy plane. It has cameras and electronics up the wazoo. You fly it high and fast over a target, collect the info you need, refuel it and change target. Unlike a satellite, you can do that many times per day.
Against the USSR it had become risky because missiles could reach it? And satellites worked great during the cold war. But in a scenario where things got hotter and you wanted regular fresh intel from deep within enemy territory, the SR-71 could be irreplaceable.
AIM-120 range and altitude upgrades have been in the works for many years, and balloon defense is a relatively low priority mission. It will also be supplemented by the new AIM-260 which has greater capabilities. The primary goal of those programs is to achieve greater stand-off range versus near-peer adversary aircraft.
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.
What are you talking about? The YF-12C was a converted SR-71. It flew exactly as I'm describing. All of this has already been done before.
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.
What are you talking about? The "YF-12C" designation was not a combat aircraft. It was a fake designation slapped on a regular SR-71 that NASA used for flight testing in order to hide the secret origins of the program. There was never a real YF-12C.
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.
https://www.nasa.gov/image-article/yf-12a-yf-12c-flight-form...
> 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).
Right, the YF-12C was a fake designation for one SR-71 and not capable of carrying or employing any weapons.
What about U-2?
https://www.theguardian.com/world/2023/feb/22/pentagon-pilot...
Not fun enough.
And possibly too slow to be safe from space weapons from escort satellites protecting balloons, or too slow and clumsy for combat missions of any kind.
The service ceiling of the SR-71 is still well beneath the altitude of a modern balloon. The speed isn't necessary, and it's altitude record has been beaten by other modern jets.
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.
The F-15 can climb 30,000 feet.
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).
You misread your source: the F-15 can climb 30,000 feet in 60 seconds - the service ceiling is closer to 60,000 feet officially, and 90,000 under ideal conditions:
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.
Per the first link you provided, the F-15 has the following:
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).
Fair correction on the altitude (still in the lower bounds of the balloons, as I mentioned).
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.
China can launch a lot more than a dozen balloons, perhaps thousands if convincing decoy payloads can be made. The A-12 was intended to counter high-value targets in a limited number, not low-value targets en-masse.
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.
F-15s are not stealth. You don't want to risk escalation by sending fighter jets towards someone else's airspace. To me, they don't make sense for this kind of mission.
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.
I'm missing something - why would you be wanting to intercept balloons over someone else's airspace? The 2023 incident was in US (and Canadian) airspace.
Sorry, I should have explained it: you want to intercept a spy balloon before it enters your airspace, not after it has already entered and possibly gathered any information.
Well there's a whole lot of ocean one doesn't need to be stealth to fly over but really, your comments read like endless goal-post shifting from someone who has a preferred solution in mind and is working backwards to justify it. Also the SR-71 was never stealth, only reduced observability. The USSR was very aware of the overflights taking place.
It seems no one else offered any other concrete uses that would justify the efforts that went public regarding the frame reuse.
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.
It's boring, but "aerial hypersonic testbed" is almost certainly NASA's intention, just like they did in the 1990s: https://en.wikipedia.org/wiki/Linear_Aerospike_SR-71_Experim...
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.
[0] https://en.wikipedia.org/wiki/Lockheed_D-21
Thanks, that is a little bit more elaborate than the information on the interview and actually makes sense.
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?
I don't have access to any privileged information, here. My best bet is that DARPA is lighting a fire under JPL's ass to explore variable-cycle engine technology: https://en.wikipedia.org/wiki/Variable_cycle_engine
The US has tested ramjets before, but mostly in the context of missiles and boost-glide vehicles. The "holy grail" of efficient propulsion would be to taxi/accelerate with a turbofan engine, bypass into a ramjet for Mach 3-to-6ish, and then transition to a liquid-fuel rocket motor for the last Mach 6-10 climb. An engine like that could escape the Earth's atmosphere without sacrificing efficiency at lower altitudes. I realize that "space fighter engine" is also a longshot, but China has ramped up investment in variable-cycle technology quite a bit in the past 2 years. Simply solving the turbofan-to-ramjet transition would be a huge boon for high and fast flight.
Issacman's quotes in that article suggest, to me, that he wants to reboot the SR-72 program (or something similar) with cleansheet propulsion as a feature. The SR-71 could be the engine testbed, and a future airframe could be designed around the requirements of the engine. Just my $0.02 though.
Don't worry about being precise, this is an informal speculation thread with low stakes. I don't expect anyone (especially me) to nail it.
Thanks for the insights!
Your amounts are off. that wikipedia page lists the f-15 as having a service ceiling of 65,000 feet. Perhaps irrelevant but a f-15 shot a satellite down once(not relevant because that is more the missiles capabilities than the planes, which is probably the relevant point)
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.
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