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A while ago, NRO put on-line a bunch of declassified documents [1], including their internal books about the history of satellite reconnaissance. But it was all in one unsorted pile, often scans of barely legible pages. I think this was the original source of some of the documents shown in this article.

Although one could randomly stumble on some interesting anecdote here and there in the NRO archive, overall that collection was not made to be easy to navigate, and one would have to be very patient to sift through it thoroughly. Maybe the situation is better now.

[1] https://www.nro.gov/foia-home/foia-declassified-nro-programs...

A very good 10 MHz ovenized crystal oscillator, Hewlett Packard 10811D, ages by up to a few Hertz per year, and has a mechanical capacitor for trimming the frequency by up to 10 Hz, and an electronic frequency adjustment by 1 Hz using a varactor. I am sure the varactor does not improve jitter, but considering that the full range of adjustment is 0.1 ppm, it also should not add that much jitter, assuming everything is well designed.

So we are talking about a reasonably high stability crystal to begin with, and a very narrow adjustment range. In an atomic clock, the feedback loop uses the electronic frequency adjustment to more or less completely remove the aging. This requires a very tiny and a rather slow acting feedback.

In the atomic clock, the output of the crystal is used as a reference for a microwave sweep generator, which then scans the spectrum of atomic transitions. The absorption peak in a cesium clock is something like a kiloherz wide, but with a good signal to noise ratio and with a lot of averaging, one can measure the position of the peak to a very tiny fraction of its width. Comparing the measured and the expected positions reveals the deviation of the reference frequency from its design value, and that is what generates the tuning feedback for the crystal. I do not know off the top of my head how slow the feedback is exactly -- it is something that one could look up in the Hewlett-Packard service manual, but I am sure it is slow enough to be irrelevant for the cycle-per-cycle jitter.

There are different types of atomic clocks, but in most common types, the output comes from a crystal oscillator, or more generally frequency synthesizer, which is then slaved to some spectral feature in the "physics package". That is to say, the phase noise is as good as that of the crystal in the unit, but the longer term frequency stability is much improved by the slaving.

An exception is an active hydrogen maser, which directly outputs the frequency of atomic transition. It has very good phase noise, but is a rare beast, which is only used where it is absolutely necessary.

The cone of Cherenkov radiation produces arcs of "bright pixels" in the detector.

There are very good illustrations of this if you search for "Super-Kamiokande Cherenkov ring." That's a Japanese neutrino telescope with a bunch of huge photomultipliers lining the walls of a giant underground cistern filled with water. Ice Cube has similar light detectors, probably from the same Japanese manufacturer, that were lowered on strings into wells melted into ice.

It was not just the VCs. There were also influential people in Pentagon who saw the inefficiency of the prime defense contractors, especially after having seen what SpaceX was able to do.

One of the consequences of this was the meteoric rise of the young Will Roper [1], who in a span of a few years went from a theoretical physicist to being in charge of the Air Force procurement program, and then tried to facilitate the access of startups to defense contracts, through AFWERX and "Defense Pitch Days".

Whether this worked or not is debatable, but the itch to change things was there. One example of a startup which was an early beneficiary of this top-down attention is Ursa Major [2], a rocket engine company. Unless one looks at them in the context of these military programs, their existence would seem quite puzzling.

[1] https://www.af.mil/About-Us/Biographies/Display/article/1467...

[2] https://www.youtube.com/watch?v=mE1HZAPPSrE

Indeed. Here is another page about the same thing: https://cwandt.com/products/pocket-fiche

"This project is a collaboration with Miles Segal (Gotham Silicon), whose mission is to make microchip fabrication more broadly accessible. Creating ultra high resolution micron-scale imagery is the very first step in this process."

"Those are clips of Miles in the Columbia University Nano-fabrication Facility where he is developing a workflow to make the technology required to build microchips more accessible."

Another mention of the same: https://x.com/JoinEdgeCity/status/1966180823129878656

"Miles Segal is building an ASIC foundry by repurposing vintage nano-fab gear to deliver custom chips in 24–48 hours."

"During the week he was at @EdgeEsmeralda, he focused on making new connections – leaving with new energy, confidence, and momentum from countless serendipitous convos."

So it seems to be one very young dude passionate about revolutionizing semiconductor processing. Whether there is an actual market for a super fast turnaround at 1 um node, and whether he has the experience and the support to pull this off, is somewhat dubious.

But of course wonderful things do sometimes happen. While he was a student, Sam Zeloof became a legend by building a chip fabrication lab in his garage, using surplus and home-made equipment. Now he has a serious team, working on developing mini-fabs: https://fab2.com/ That looks pretty serious.

Sounds great as a slogan, but there are no details. For comparison, Intel's 1 um process (Fab 3, 80386-era) required about 4 weeks of processing time, and if pushed, the samples could be processed in as little as two weeks. For a long time they were getting about one working die per 4" wafer.

If Isar will get a large scale commitment from the government(s) to launch the OneWeb 2.0 constellation, as the European alternative to US, Chinese and Russian systems, they may well become a major launch provider. And of course they are already working on a much larger reusable rocket.

Although the original OneWeb satellites were assembled in the USA, they were developed in Europe and the components were always sourced predominantly from Europe, Canada, and Africa, with only some parts produced by the European companies in the USA, and even fewer parts sourced from the US companies. It is a very European satellite.

Talking about the role of V2 in the development of rocketry in various countries is more or less relevant to the discussion of Isar, because it was a major milestone, and it did influence all rocketry worldwide, in many different ways.

Rocketry may be much more talked about, but in terms of headcount is was a tiny thing compared to the number of German experts who were "invited" into all Allied countries after the war. Just France and UK had brought in about 3 thousand persons each. If one had said that this did not happen, that would have been an error. But simply not bringing this up at all because it is not very relevant to the discussion of Isar is fine, I think.

Debating who "won" the space race, and who "used" Germans "better" is not something that I want to do.

Incidentally, the early investment for Isar came from Bülent Altan, the Turkish ex-SpaceX guy who was in charge of the guidance system for Falcon-1, Falcon-9 and Dragon.

Most of the US space launch startups have failed. And in Europe it is harder to even try.

There was a confluence of several factors which helped SpaceX to succeed, and not the least of these was the employee number one. For many years, Tom Mueller has been working in his free time on rather large liquid fuel amateur rockets, which he was building in his garage and which he was launching from some amateur rocketry facilities in the desert. In terms of regulation it was a relatively accessible hobby in the US. At the time Musk found him, he was working on the original "BFR" -- a very large liquid fuel amateur rocket. So the deal was to invest serious money into the project and scale the same no nonsense approach to a small orbital launch vehicle. They were in LA, the center of US aerospace manufacturing, so through Tom's professional connections and knowledge of who was who in the industry, they were able to source the necessary materials, components, and to find the key personnel for their company. Significantly, NASA has already spent probably a decade or more trying to get somebody to produce a cheap small launch vehicle. This did not directly affect SpaceX, but it did fund the R&D for example at Barber-Nichols, which enabled them to offer a turbopump for SpaceX engine at a much lower cost than it would have been possible otherwise.

At first, Musk and Co thought that they would be able to develop the rocket for a few million dollars. But even in the US regulatory environment it turned out that doing everything in compliance with regulations raised the costs to well over a hundred million dollars.

So, Tom's hobby + Musk's activism + industrial ecosystem in the area + NASA's prior support of component vendors + being at the right time to snag the International Space Station delivery contract were all important for SpaceX thriving where so many others have failed.

USA got the cream of the crop of the managers of the German missile program, while the USSR got the workers, who actually did the work with their hands and built the parts for the rockets. (One exception was Helmut Gröttrup, the head of the V-2’s guidance and telemetry systems.)

In fact, after the war the USSR has briefly reconstituted the manufacturing of V-2 in Germany, employing thousands of people, before transplanting this entire industry to the USSR. This dramatically lifted the level of Soviet manufacturing and relevant metallurgy.

von Braun's dissertation was on engine design and testing. But when he built the Redstone missile in the USA, he ordered the engine from a US company -- the engine which was already a generation ahead, compared to the imported German engines which the US engineers studied after the war.

Meanwhile, the Soviets have developed even better engines, completely on their own, though with the important parts built using the materials and the equipment brought from Germany.

So it is debatable whether having the German higher-ups and having a greater continuity with German design philosophy was a good thing or a liability.

It is less well known, but France have also imported a significant number of ex-Peenemunde engineers for their program. And their engines developed in a way different from both the American ones and the Soviet ones -- which definitively shows that although internalizing the German know-how was the starting point for everyone, it did not define the path of subsequent development.

Of course, the engines were not the whole story. The Germans took to the USA the advanced prototypes of the inertial guidance systems which were developed for the missiles that were supposed to come after the V-2. And the Soviets got Helmut Gröttrup. This did have its effects in both cases.

They do not like to talk about it too much in public these days, but Rocket Lab had somewhat shady beginnings. Once they moved past the semi-amateur phase, their first real project was weapons development on a DARPA contract. They were working on a paste-like semi-solid fuel for throttleable engines for munitions, and other similar things.

That pushed their main NZ investor away, and they somehow hooked up with the US intelligence community, which facilitated a rather unique series of inter-government arrangements for launching US reconnaissance satellites from NZ. That was probably always the appeal -- to launch over China with very little warning. A cheap, rapidly launchable vehicle was always a dream of the US agencies -- in 2003 this was FALCON program (Force Application and Launch from CONUS) run by DARPA and the Air Force, and today it is the Space Force's "Victus".

So, although the bulk of work was done in NZ, Rocket Lab functioned rather intimately with the US spooks from the very early on, including getting some funding from In-Q-Tel. Then in 2013, for the bulk of investment they just had to become a Delaware Corporation, for all the usual reasons. Very soon they moved engine manufacturing to a facility in California. More recently, with the large rocket (Neutron), their main manufacturing operations are in LA and the launch facility in Wallops. All in all, they are an international outfit.

It is uncontroversial among Dostoyevsky's scholars that his main focus is on Russian mysticism while the stories themselves are merely a setting for presenting author's theology. But that may be flying over the head of a typical Western reader. Even for Russian schoolchildren this requires to be carefully explained.

Dostoyevsky subtly advocates that Western rationalism, materialism, and utopian socialism lead to failure, and only spiritual communion of people bound together by love and Orthodox faith can give hope. This idea of specialness of "messianic Russian soul" and of Orthodoxy is extremely in vogue today in modern Russian ideology. But that is a different subject.

Marc Raibert was a student of Ivan Sutherland. Sutherland had a lot of pull at DARPA. This facilitated the unique prototyping work done at Boston Dynamics to get noticed and supported by DARPA.

But as a flip side of this, Boston Dynamics developed certain idiosyncratic interests in getting the hydraulic valves just right, etc. Their machines required a lot of tender care, (expensive!) and were dangerous to be around.

When Google acquired them, many things were mismatched. Andy Rubin, the VP at Google who advocated for BD, got fired for alleged sexual misconduct. This cast a shadow on the whole plan that he was trying to implement. DARPA finding did not sit well with Google's ethics. They pushed BD to stop getting grants from DARPA.

Expensive and dangerous robots were not an ideal fit for AI experimentation. Google was buying cheap and much safer tabletop robots for that. All in all, there was no good fit, and after spending tons of money on it, Google have gotten rid of them. They did encourage BD to develop a cheaper, safer electric robot, and this became Spot Mini.

Maybe it was a bit too colloquial. I am not sure if this is very important. A formal term would have been "full propellant load." The phrase "fill level" is also used in NASA documents.

The question was whether during this test the stage was loaded with the same amount of fuel as for an actual flight, or only a small fraction of that.

Correction: The first stage of New Glenn carries only about 260 tons of methane. The 1150 tons is the full propellent load, liquid oxygen and liquid methane combined.

The heat from combustion of this amount would be about 3.4 kt, which is roughly the same as the heat in the late fireball of the Trinity test.

The mushroom cloud from the New Glenn explosion was also substantial: https://photos.app.goo.gl/a7uPVjsB5n453SJA7

The problem is that there is no standard meaning for the "full duration" in this context.

Some reports say that this means "running all seven BE-4 engines at full thrust for up to 38 seconds".

In flight the engines fire for 190 seconds.

So what the full duration means, and whether they fill the tanks with just enough fuel for the firing, or with a larger amount to help the clamps to hold the stage down, all this we will probably only find out from the investigation, if the results are ever published.

The TNT is relevant, because the atomic bomb energy output was defined in terms of TNT equivalent. Not the energy of the blast, but the total output. For Trinity this was 20 kt, or 20*4.2 TJ.

This serves as a basis of comparison for this deflagration. If we are considering specifically the appearance of the late fireball, the heat output is the relevant figure of merit.

Assuming about 10-15% of the total bomb energy remained in the heat of the late fireball (with the rest spent on the blast wave, peak thermal radiation and neutron/gamma radiation), the fireball of this rocket deflagration could have exceeded the late fireball from the bomb. But this assumes the tanks were fully filled, which we do not know yet.

You are talking about the energy of the blast. In my comment I was talking about the heat output. From the followup comments it seems I have not made it sufficiently clear.

The energy of the detonation wave in rocket explosions is typically 1-2% of the energy in the fuel, at least that is the ballpark of what people use for estimating the effects of mishaps.

We also do not know if the tanks were fully filled -- it the past, rocket companies have called 10 second static fire tests a "full duration static fire test." We will probably find out later what it actually was meant to be.

It is not clear what "full duration static fire" means, but if the stage was fully fueled, the fuel tank would have contained 1000 tons of methane. The heat of combustion of methane is 55 MJ/kg. TNT equivalent is defined as 4.2 MJ/kg. In terms of heat output (not blast or other effects) this would have been equivalent to 13 kilotons of TNT.

The first atomic bomb had yield of 20 kt TNT, of which about half was in heat, and the rest in the blast and radiation.

Depending on how full the rocket tank actually was, the fireball from the rocket explosion was in the same ballpark, or possibly even larger in the size and duration of afterglow compared to that from the Trinity nuclear test.

Both SpaceX and NASA use LabView. NASA has a relatively detailed description of the engine test stands at Stannis:

https://scholar.google.com/scholar?q=NASA+Data+Acquisition+S...

https://scholar.google.com/scholar?q=Design+of+Electrical+Sy...

A typical test stand would have maybe a thousand channels of relatively slow data (pressures, temperatures, flow rates, valve states, etc), and maybe up to a few hundred of channels for essentially audio data from vibration sensors. This amounts to sub-gigabit per second data rate overall.

If very high speed video / multiple video cameras are used, this could generate massive data rates, but unless something interesting happens it is not clear how important this data is.

In flight, the telemetry data rate from the entire Falcon-9 used to be measured in megabits per second per stage, plus the video stream. It was not a huge amount of data. Presumably now with Starlink they send a lot more telemetry from Starship, but in flight the engines typically have far, far fewer sensors compared to the ground testing.

Five years ago SpaceX reported that they had 30000 seconds of test firing time on the Raptor, over 567 engine starts. Since them the program accelerated dramatically. Well over one thousand engines had been produced, and on an average day at McGregor test facility the Raptors are fired for about 600 seconds. That would give about a million seconds over five years. That's a lot for any engine development program.

If we look at the venting from the propellant tank (around T+16:15) it looks thick white closer to the vent, becoming more transparent and blue as it expands. That's just sunlight scattering on the particles and density fluctuations in the flow.

A good cold gas thruster produces a lower density, more expanded flow, which looks blue for the same the reason the sky looks blue.

One can compare this to the exhaust from various Falcon-9 engines and thrusters when it is illuminated by the sun on the backdrop of the night sky: https://youtu.be/JRzZl_nq6fk?t=193

The views from Ship's engine bay looked rather ominous -- with the red glow visible in multiple places, and something venting furiously from the broken engine. It was a pleasant surprise that the ship did not explode and not only that, but it even landed exactly on target. Guidance system software engineers have done a very good job!

The booster not completing the return part of the flight was disappointing. They had a similar incident in one of the previous flights, when they tried to maneuver the booster too aggressively immediately after stage separation which caused problems with the fuel supply. If it was something similar this time, it might be solvable by changing just a few details of the maneuver. So, maybe it is not that huge of a deal.

There were many cool things in the webcast, from them showing the catamarans that are deployed at the landing site, to the views form the cameras on-board of the "satellites". The first few minutes after liftoff were just amazing visually.

There is an excellent three part documentary from Sandia National Labs:

"Always/Never: The Quest for Safety, Control, and Survivability." (part 1) https://www.youtube.com/watch?v=DQEB3LJ5psk

They cover both the technology itself and its history, including the incidents you are reading about. These people are the ones who developed the methodology and the technology for nuclear device safety, or at least a significant chunk of it. I think it has recently become much more mathematically heavy, with zero knowledge proofs and other fancy stuff used to talk to the locks in the devices.

Cleve Moler was one of the big names in numerical methods, and participated in creation of canonical FORTRAN libraries for solving linear equations, and matrix algorithms more generally.

To teach this more conveniently to his students, he wrote the original version of MATrixLABoratory to allow interactive exploration of the library functions without having to compile FORTRAN code. The original version was about 2000 lines of code in FORTRAN.

Engineering students loved it so much that he decided to make a company around this product. His buddy expanded and rewrote the interpreter in C, for a PC, and the rest is history:

"In 1983 Jack Little suggested the creation of a commercial product based on MATLAB. I said I thought that was a good idea, but I didn't join him initially. The IBM PC had been introduced only two years earlier and was barely powerful enough to run something like MATLAB, but Little anticipated its evolution. He left his job, bought a Compaq PC clone at Sears, moved into the hills behind Stanford, and, with my encouragement, spent a year and a half creating a new and extended version of MATLAB written in C. A friend, Steve Bangert, joined the project and worked on the new MATLAB in his spare time."

User guide for the original version of MATLAB: https://blogs.mathworks.com/cleve/2018/02/05/the-historic-ma...

The source code of the very early (1982?) FORTRAN version of MATLAB: https://github.com/johnsonjh/matlab

The origins of the first PC version: https://blogs.mathworks.com/cleve/2018/03/09/matlab-history-...

They struggled with many things, often time the minutiae of accomplishing something conceptually rather simple. For example, making an explosive with a significantly slower detonation velocity turned out to be very tricky. The concept was simple -- just add some barium nitrate to the TNT. But if you just did that, the mixture stopped flowing nicely, and it still was either not slow enough, or refused to explode at all. Extreme technological nuances were required just to prepare a mixture of two simple ingredients before satisfactory results were obtained. This one thing was its own research project.

Accurately casting explosive in odd shapes, without different ingredients separating, and without producing voids when the melt solidified, required developing a whole new technology with careful gradients of temperature in the molds.

They tried lots of different commercial and handmade detonators to find which ones would work most consistently. That took an awful lot of time.

The electronics itself was probably least difficult -- a microsecond was already a very long time for the electronic circuits even in 1945. One could use an off the shelf oscilloscope to see if the detonators worked simultaneously or not. Incidentally, 2/3 of the cables in the famous picture of the "Gadget" are not the detonators, but the simultaneity sensors -- reporting the difference between the earliest and the latest detonation fronts.

Everything was tested extremely extensively. Tremendous resources were spent on testing and test equipment. All in all somewhere between 20000 and 40000 explosive tests were performed at Los Alamos during the project.

It is not often emphasized how much of the work was done in the explosives laboratory in Pittsburgh before passing it on to Los Alamos. They have developed the slow explosive. They also reproduced from the earlier British work and further developed and tested the concept of the lenses, together with many other more advanced things which did not find an immediate application in the bomb. The director of the laboratory, George Kistyakowsky, took over the explosives work at Los Alamos, once the implosion became the main focus of the project.

There are different versions of the story. In one of them, somebody asked the question whether the atmosphere could ignite, and that was very quickly answered in the negative, but then Oppenheimer mentioned it to the people in Washington, and after that the question recurred periodically because the higher ups got unduly alarmed.

And then of course there are versions making it into a much more dramatic story.

When they were working on the fusion bomb (and Edward Teller was working on fusion full time already during the Manhattan project), it took some years to establish that even the "easy" to fuse deuterium cannot be set of by simply blowing up a fission bomb. The reaction simply did not propagate for any reasonable dimensions of the system. For any other material the energy balance would have been orders of magnitude short of what was required for a propagating fusion burn.

Plutonium was compressed about two-fold by volume.

There is a story about it. When they first brainstormed the ways to make the bomb, even before Los Alamos, in 1942, one of the several ideas was to use explosives to throw smaller pieces of material together, to make the super-critical mass. This was dismissed as too imprecise, but it was still listed in the April 1943 as one of the possibilities in the Los Alamos Primer, which was the orientation booklet for the scientists joining the project.

One of the scientists, Seth Neddermeyer, fell in love the the idea and talked the bosses into letting him try it. He consulted with the explosives experts in Pittsburgh and started some crude preliminary experiments.

When von Neumann was told about these experiments in October 1943, he immediately pointed out what when the pieces of metal slam together at a high velocity in the center, this creates extremely high pressures. Teller then remembered that at such pressures, iron in the Earth's core becomes slightly compressed. They instantly realized that compression makes the exponent in the chain reaction greater, and that this is a new way to make the bomb. They explained the idea to Oppenheimer, and he pivoted the project to the new method.

This did not work. The material did not assemble into a neat ball, but was just making a mess. But Robert Christy, the guy who was making the calculations for this, realized in September 1944 that the slamming of the pieces together at high velocity was not strictly essential, and that a solid ball of metal could also be compressed by an inward going shock, although not as efficiently. Because this was guaranteed to work, this was chosen as the design for the "Gadget".

Ironically, Seth Neddermeyer, who was instrumental for this to happen, has never accepted that the metal could compress.

April 1943 Robert Serber "Los Alamos Primer" https://upload.wikimedia.org/wikipedia/commons/9/9c/Los_Alam...

Interview with Robert Christy where he recalls the invention of the solid core https://www.youtube.com/watch?v=Ez45QEMI5CA&list=PLVV0r6CmEs...