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.
It isn't this simple for liquid oxygen and methane mixtures, and there's a great deal of disagreement between industry and regulators over what the right percentage of TNT equivalence is. Naturally, industry thinks the percentage is low, and regulators are skeptical, so there's a government-run test campaign going on as we speak to collect data for proper modeling.
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.
Counting frames on YouTube, I get about 0.3s for the blast front to reach the top of the 600ft towers. That gives an estimate of around 600 tons TNT so definitely nowhere near all the fuel exploding.
Sedov-Taylor-Rayleigh blast equation, though this video isn't high enough frame rate to more than ballpark it I think. Tower is ~180m high, so 0.2 sec would be a bit over 1 kiloton instead? But definitely not remotely 13 kt. Still serious of course, when SpaceX suffered launch complex damage during some of its incidents it took a solid 6-12 months to fix.
Everyone can be glad though that no hypergolics are involved at least!
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.
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.
I think the point is that that phrasing has been used by rocket companies to mean a whole range of different amounts of fuel load, it's not very precise wording in practice.
From the industry: I would expect to hear "mission duty cycle" in that case. "Full duration" doesn't have a consistent meaning (a fact which is sometimes used to the marketing team's advantage).
Flight computer tells engine to go. Full go, launch sequence. Engine goes. To me, anything but that isn’t a full-duration anything.
If clamped down, it’s a full-duration static fire. If clamps release, it goes to space. Basically, if the engine can’t tell (apart from atmosphere, which is a big apart) it isn’t going to space, it’s a FDSF. It’s a whole-engine show. If you’re running parts through a full duty cycle, that can be done in a lab (or on a stand).
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.
I think it's amazing they can basically hold a rocket down and let it launch like that without things exploding or shearing apart from the forces. Are those the same bolts as the exploding ones they would use for a normal launch?
(on that note it's also amazing that these exploding bolts are so reliable, I can imagine even a single one not releasing would cause... Issues)
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.
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.
> SpaceX Rocket Development and Test Facility, McGregor, Texas
> SpaceX calls the facility the most advanced and active rocket engine test facility in the world, and said that by 2024, over 7,000 tests had been conducted at the facility since it opened, with seven engine test fires on a typical day. Despite its low-profile compared to the company's other facilities, is a critical part of SpaceX's operations, and company president and COO Gwynne Shotwell maintains her primary office in McGregor.
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.
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.
Yeah, the new raptors and engine bay redesign for version 3 of ship seem a lot more robust than version 2, very impressed that the ship finished its mission so well.
Scott Manley goes into quite a bit of detail on analyzing superheavy’s failed boostback, it’s a good watch:
TL;DR - seems like the hot staging kicked the booster out in the wrong direction, and the ship’s plume impacted one of the grid fins, which would’ve given it quite a big kick. The sloshing just from that could easily have caused the observed issues.
Well it was supposed to be a moon landing, but SpaceX didn't get their stuff developed. Artemis II flew by the moon btw, I think that's more impressive than SpaceX crashing a bunch of suborbital flights into the ocean while behind schedule.
My comment was about the video coverage. Artemis II's coverage for the launch was especially lame. The solitary gopro on the side of the capsule had some cool footage but was just a single camera.
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."
A true giant. His algorithm for Pythagorean addition, which computes sqrt(a^2 + b^2) without taking square roots, is a wonderful gem.
Fun anecdote about early Matlab. In the '80s, while in high school, I "acquired" the source code of an early version of matlab, similar to the one that you linked. An email from Cleve Moler in 1990 asked people not to distribute the code, so I didn't give it to anybody. In the late '90s I visited Cleve Moler at his Mathworks office, and he proudly showed the early Matlab running on DOS, remarking that he only had that binary but had lost the source code. So I gave it to him.
MATLAB competed in the same space with a piece of software called GAUSS. Both had their initial commercial release in 1984. MATLAB eventually went on to dominate most areas, but I had to deal with the pain of writing my dissertation in GAUSS, which continues to be heavily used in specific areas today.
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.
I think some people miss the Nolan film’s central irony:
By the conclusion, the joke about the “near zero” physical possibility of the end of the world has transmuted in Oppenheimer’s mind into certainty that Trinity ignited social forces leading to the same doom.
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.
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.
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.
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.
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