Former SR-71 engineer talks NASA's Blackbird revival program
twz.com136 points by rkagerer 6 days ago
136 points by rkagerer 6 days ago
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...
> 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 :)
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.
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.
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.
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.
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.
---
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.
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.
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. :)
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.
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.
> 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.