generuso

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...

It is all true, but one needs to take into account that because of the different properties of the materials, the critical mass for uranium-235 is intrinsically much greater than that for plutonium-239.

For a bare sphere, it is about 10 kg for plutonium and 50 kg for uranium.

99% of all diamonds by mass are industrial diamonds. But they are so inexpensive that they only account for 3% or the revenue.

The jewelry is the remaining 0.8% by mass, and it is split roughly equally between the natural and synthetic stones by mass, but with about 80% of the revenue going to the natural stones.

Here is a very good video showing how large poly-crystalline industrial diamonds are made in the USA: https://www.youtube.com/watch?v=6o5RprIJmfA

China has their own, slightly different flavor of this machine, the cubic press. These machines are manufactured in thousands and cost about half a million USD each. They are used to produce both industrial and jewelry quality diamonds: https://www.youtube.com/shorts/cED0TjwKUDM https://www.youtube.com/watch?v=5cnEVb7aPfM

The original machine was invented by a guy at General Electric: https://en.wikipedia.org/wiki/Tracy_Hall

I think one can extrapolate further. There will be two things intertwined together:

1. Thought will be liberated from the confines of mortal bodies. 2. Technology will be able to create and modify things on the molecular level, limited only by imagination (and the laws of physics of course).

Spirits will be roaming the cloud, developing in ways unseen before, and interfacing with the "real process" through whatever shapes suit the purpose.

Of course, learning from the treasure of design solution accumulated through the billions of years of biological evolution will be a large step towards this. Extending this heritage will be the next step.

The point is not that silicon is not suitable for extreme cold -- it is, with careful design. But the authors want to use a semiconductor which would operate at much higher temperatures than silicon can. And most of these have a disadvantage that they stop working at low temperatures.

What the authors have developed, is transistors which could work at a very high temperature, but also work at extremely low temperature. That is quite rare.

Exactly. In physics, when people measured things at 4K, there were many examples of active circuits built to measure or amplify things in situ at 4K, and only send the results out, often by the same wire that was used to power the circuit.

It was unintentional, but it is actually kind of true in his case. The guy is a founder and the CTO of two semiconductor companies.

In the "real" DRAM chip, there is a large array of very tiny capacitors, with the switches which allow to connect one row of the array at a time to the readout column wires.

The capacitance of the wires themselves is typically an order of magnitude greater than that of the storage capacitors. So when the memory is read, the wires are first precharged to some standard voltage. Then the desired row of storage capacitors is connected to the wires, and the charges from the storage capacitors spread onto the wires, changing their voltages very slightly. These voltage deviations from the standard value are amplified by the "sense amplifiers". The amplifiers are sort of like flip-flops. Once they start in a state which "tilts" slightly to "zero" or slightly to "one", they go all the way to the full magnitude zeros and ones. This not only amplifies the signal, but also automatically brings the voltages on the wires and the still connected to them capacitors to the full magnitude, thus "refreshing" the data. The row is disconnected, and the next read cycle can start for some other row.

In the video, an array of 4x5 capacitors and the associated with them switches was fabricated. The capacitors in the video are several hundred times larger (12400 fF) than typical capacitors in a 64 Kbit DRAM (about 50 fF). I assume this is done so that in the later episodes the author could implement the readout electronics outside of the chip.

It is not really feasible to fabricate usable integrated circuits at home. There is a huge difference between a one off demonstration of a principle that "sort of works", and perfecting the process to the point that it produces finished parts that can be relied on.

This guy is not exactly a regular person. He is a pretty unique case of a talented semiconductor engineer who has a home lab for side hassles. It is not a low effort thing. He runs the equipment 24/7, scrubs all the surfaces in the lab daily to keep it clean.

Still, with the lab and all of the equipment already at hand, it cost him several weeks of work to produce this demonstration of transistors and capacitors, which kind of work, but are still long ways from a "completely complete" 20 bit DRAM chip.

Unfortunately it is simply too much work for one person to maintain a viable semiconductor fabrication process, even when it is done semi-professionally.

Of course it not easy. He spent $20k on materials and a good amount of elbow grease just to construct this one room. In order to maintain the clean environment the air circulation runs 24/7 and he washes all the surfaces daily using cleanroom wipes. Deionized water system provides water for washing the cleanroom gowns. It is a lot of work just to have a small facility at home for odd jobs.

The furnace is a low cost off-the-shelf Chinese product from Anhui Beq Equipment Technology Co.

Much more impressive are the modifications to the microscope, transforming it into an improvised lithography machine, and the home made plasma etching machine, cobbled together from surplus components.

Of course, the whole thing, starting from the clean room, is extremely impressive -- Intel started their business in a much simpler facility.

Pure hydrogen in a balloon produces a low, loud, very satisfying bang. Completely different from a sound of an air balloon popping. Here is a video from a very good Royal Society of Chemistry demonstration series on various unusual combustion process:

https://www.youtube.com/watch?v=Rwbyl7ywfhk&list=PLLnAFJxOjz...

Hydrogen mixed with air or with oxygen produces an ear piercing supersonic detonation, exceedingly loud and unpleasant. Not recommended for demonstrations.

There are many cases in the news of accidents with sometimes a large number of party balloons filled with hydrogen or other flammable gases.

One of the larger episodes was in 2012 in Armenia, where thousands of balloons exploded during a meeting, injuring 154 people, of which 4 seriously (the video is of poor quality): https://www.youtube.com/watch?v=jWEm2sS7Dw8

A smaller, more recent episode in India: https://www.youtube.com/watch?v=FH5JwHeKnZo

Starlink project began after Musk and Greg Wyler parted their ways. Wyler approached SpaceX in 2014 with a proposal to build OneWeb (then called WorldVu), and initially they worked on the project together. But then they started to accuse each other of doing various underhanded things, and split. After that, Musk decided that he could do a similar and even better system without Wyler, and that's how Starlink was born in 2015.

Heat capacity is irrelevant -- argon and helium have exactly the same heat capacity per liter of gas, which would be the figure of merit in this context.

Heat conductivity, on the other hand, is an order of magnitude higher for helium, compared to argon, because its atoms are moving faster due to their lower mass.

When the gas is used for cooling, heat conductivity is important because it determines the conductivity through the boundary layer near surface, where the velocity of the flow drops to zero at the surface itself, and all the heat transport is through conduction rather than advection.

Sure. Line scan indoor units are extremely affordable, and some cost less that $20, sold as spare parts for robot vacuum cleaners. Outdoor units (with higher ambient light tolerance and longer range) are an order of magnitude more expensive, but also available.

Here is some detailed information about low cost units: https://github.com/kaiaai/awesome-2d-lidars/blob/main/README...

The efficiency of X-ray tubes is proportional to voltage, and is about 1% at 100kV voltage. This is the ballpark for the garden variety Xray machines. But the wavelength of interest for lithography corresponds to the voltage of only about 100V, so the efficiency would be 10 parts per million.

The source in the ASML machine produces something like 300-500W of light. With an Xray tube this would then require an electron beam with 50 MW of power. When focused into a microscopic dot on the target this would not work for any duration of time. Even if it did, the cooling and getting rid of unwanted wavelengths would have been very difficult.

A light bulb does not work because it is not hot enough. I suppose some kind of RF driven plasma could be hot enough, but considering that the source needs to be microscopic in size for focusing reasons, it is not clear how one could focus the RF energy on it without also ruining the hardware.

So, they use a microscopic plasma discharge which is heated by the focused laser. It "only" requires a few hundred kilowatts of electricity to power and cool the source itself.

Neato from San Diego has developed a $30 (indoor, parallax based) LIDAR about 20 years ago, for their vacuum cleaners [1].

Later, improved units based on the same principle became ubiquitous in Chinese robot vacuums [2]. Such LIDARs, and similarly looking more conventional time-of-flight units are sold for anywhere between $20-$200, depending on the details of the design.

[1] https://scholar.google.com/scholar?q=%22A+Low-Cost+Laser+Dis... [2] https://github.com/kaiaai/awesome-2d-lidars/blob/main/README...

You could [1], but it is not very cheap -- the 32GB development board with the FPGA used in the article used to cost about $16K.

[1] https://arxiv.org/abs/2401.03868

LSI Logic and VLSI Systems used to do such things in 1980s -- they produced a quantity of "universal" base chips, and then relatively inexpensively and quickly customized them for different uses and customers, by adding a few interconnect layers on top. Like hardwired FPGAs. Such semi-custom ASICs were much less expensive than full custom designs, and one could order them in relatively small lots.

Taalas of course builds base chips that are already closely tailored for a particular type of models. They aim to generate the final chips with the model weights baked into ROMs in two months after the weights become available. They hope that the hardware will be profitable for at least some customers, even if the model is only good enough for a year. Assuming they do get superior speed and energy efficiency, this may be a good idea.