1. Yes. Not just state actors - Planet Labs (https://www.planet.com/) in San Francisco, for example, is a commercial satellite company that photographs the whole globe once per day and sells that imagery online.
2. Live feed is a bit tricky, and that's where governments have an advantage - they own their own satellites, and can task them to follow a specific target. But you have to know where the target is at the start of the window, they don't have real-time video of the whole planet, and unless you've got a very big fleet you won't always have a satellite overhead when you want to look at your target.
3. Keeping track of the times of satellite passes overhead, hiding stuff underground, putting your aircraft in covered hangars and only moving them at night, putting a roof on your military docks, using upwards-facing camouflage, etc. Same methods that have been used for a hundred years to hide from air surveillance.
Somewhere between weekly and every 3 days, occasionally worse. I do not know the exact resolutions involved but they have "good" and "bad" NVDI images and the "bad" ones are fairly useless for agricultural applications.
To expand on 3: most spy satellites operate in sun synchronous polar orbits. This is so they can cover the entire earth and will have their solar panels lit by the sun. This also has the ramification that they'll always be in the same spot in the sky depending on the time of day. If you know this time, that's when you hide your tanks and don't fly your top secret spyplane
Even if they're not in SSO, satellites are hard to hide. The timetables might be more complicated for a rank and file soldier to use, but you can time your actions to be missed by any specific low-orbiting satellite.
"will have their solar panels lit by the sun" is probably not the primary reason for sun-synchronous orbits (though I guess it is presumably a benefit) - it's more about having a constant source of illumination to enable photography, as well as the ability to photograph the same site with the same shadow angle over time to facilitate comparison.
> 2. Live feed is a bit tricky, and that's where governments have an advantage - they own their own satellites, and can task them to follow a specific target. But you have to know where the target is at the start of the window, they don't have real-time video of the whole planet, and unless you've got a very big fleet you won't always have a satellite overhead when you want to look at your target.
I would really not be surprised to see the NRO go the Planet Labs / Starlink route at some point in the future and put 20 satellites in a dozen orbital planes to provide coverage everywhere at less than 60 degrees latitude 24/7/365. Sure, maybe you need the big KH-11s for the extremely high resolution shots - but 3m resolution isn't exactly trash either.
At 3m resolution a tank is about 3 pixels; a sedan is around 1 pixel. It's very hard to distinguish objects from each other and therefore to track one at that resolution.
I don't think you can get a live feed of a location since the satellites generally aren't geostationary (geostationary orbit is too far away, and are always above the equator). But AFAIK even commercially you can get still photographs of any point on earth within a couple days (i.e. you don't have to be a nation state or have your own satellites)
a live feed to follow something would 99% of the time be implemented from a HALE (high altitude/long endurance) group 4 size UAS. RQ9 or in the same class, with a combination of a high end gimbaled camera system and satellite data uplink.
Geostationary is very very far away and useless for nighttime. Imaging satellites usually have a shorter polar orbit that precesses east to west along with sunshine. https://en.wikipedia.org/wiki/Sun-synchronous_orbit
Satellites fly unpowered and frictionless in the vacuum, with kinetic energy equivalent to speed of Mach 22 at sea level, balancing against Earth’s gravitational pull, along an own 2D ellipse with one focus at the center of the gravity of the Earth.
So you can’t like fly a 3D orbit, fly at same altitude but different angular velocity, or change course without expelling significant amounts of mass. You play by those rules.
If you zoom in on the highways, you can see RGB ghost images of moving vehicles. Is that an artefact of using 3 distinct filtered inputs or something else?
[ps. The frequency shift is definitely reflecting vehicle direction - right side of highway is BGR, the other side is RGB. Delays in the sequence of 3 filtered captures?]
Yes, the different bands are not collected at the same time across the whole scene, so you get ghosting with moving objects. The SkySat sensor [1] is split in two halves: panchromatic and RGBN (where N is near-infrared). It takes lots of captures as the satellite travels that are later aligned and combined into one version.
Looks like it was pretty fortunate to have been in that warehouse versus further back. A pretty good amount of the direct blast radius looks like it was water.
The 800 tons of Ammonium Nitrate that exploded in Tianjin in 2015 left a 100 meter wide crater. In Beirut it was 2750 tons, almost three and a half times as much.
”The reported magnitude is not directly comparable to an earthquake of similar size because the explosion occurred at the surface where seismic waves are not as efficiently generated.”
Should this be interpreted to mean that the blast had more force than a 3.3 earthquake?
The seismic wave it way more devastating to the infrastructure. Leading to collapsing buildings, ripped gas pipes etc.
Explosion like this one move most of the energy into the heat and air displacement.
The immediate area is shattered but the building outside have only windows smashed.
The explosion look terrifyingly massive but the number of victims seams small in comparison.
In large-scale disasters, a low initial casualty count can be quite deceptive. It often means victims simply cannot be reached, identified, or tallied. In amount of explosive material (not necessarily yield), the Beirut blast compares with the Halifax Explosion of 1917, with 1,950 dead in that incident.
Circumstances, construction, and crowd response (the burning Mont-Blanc had attracted a large shoreside crowd) differ. But beware premature assessment.
Halifax Harbor is completely encircled by the cities of Halifax and Dartmouth. The Beirut explosion occurred on the shore so half of the blast's shock wave essentially had no effect.
Watching video, the possibility that Beirut's grain silo absorbed or reflected much of the blast also occurs. The vapour cloud showed a gap immediately above the structure in initial moments.
Also filled with up to 120,000 tonnes of energy-absorbing, high-dispersal mass: the grain itself.
Something like a 20-storey Hesco.
Most regular buildings, and quayside warehouses in particular, are surprisingly lightweight and contain comparatively little material, as the remnants of a demolition will frequently attest.
Beirut 2020 involved 2,750 tonnes of ammonium nitrate, same page.
To my mind these are roughly equivilent amounts of raw explosive agent. Some might even argue persuasively that there is slightly more explosive noted in the second.
As I've already conceeded, blast yield TNT estimates may vary, but by whatever specific measure both the Halifax and Beirut explosions were large.
And, to my initial point: damage and casualty estimates may not be instantly available.
No, that's just distinctly not the case. If you detonate a true high-explosive like TNT, you shouldn't expect to find any left after you set it off. It's well known that operations that used AN pellets in an ANFO mixture will not uncommonly find AN pellets left over, even when they use a proper high-explosive to more thoroughly detonate the charge.
AN tends to deflagrate. It has a positive oxygen balance and therefore is treated as a component in mixtures, which is to say that it is a low-explosive. And just like all other low-explosives, it needs to be confined in order to achieve a proper detonation (i.e. supersonic burn front, which generates a brisant shock front). Alternately, you can supply a shock front from a smaller detonating charge. This hardly means AN is weak, it's very much a workhorse explosive, but some work is required to extract energy from it. This is also why it's safer to work with than most actual high explosives.
Picric acid may not be especially powerful as a military explosive, but its unstable nature has been known for some time. Picric acid achieves a detonation on its own.
What this all means is that if you have an accidental explosion involving picric acid (which is a true high-explosive), you will consume all of it. If you have an accidental explosion involving unmixed AN, it likely won't be fully consumed in a way that contributes to a highly-brisant shock front. If you don't have a brisant shock front, then you more or less have a big fire – scary enough but not an explosion. You get something closer to the fire that destroyed all the crab traps in SF's pier fire, than the Halifax disaster.
>To my mind these are roughly equivilent amounts of raw explosive agent.
Perhaps, but in terms of TNT equivalence picric acid is much more effective at 96% compared to 56% of ammonium nitrate[0] with other estimates being even wider[1] i.e., 1.17x for picric acid to 0.74x for ANFO and 0.42x for ammonium nitrate, and some other figures are placing ammonium nitrate as low as 20% as effective. With the estimates ranging from a low 500 tonnes, ~1.2 kilotonnes for a reasonable estimate up to about a maximum ~2.2 kilotonnes based on 2,750 tonnes of ANFO it's looking like the two explosions aren't that comparable. But I do agree, early estimates of loss of life can be troublesome and both explosions were devastatingly large.
Picric acid was only one component of the Mont Blanc's 2653-tonne loading. It also carried rather a large amount of TNT (200 tons of the stuff, which, surprisingly, has a 1:1 TNT equivalence) and guncotton (10 tons) as explosives, along with benzol (which seems to have been the "detonator"). There was also considerable shock wave reinforcement due to the shape of the harbour bottom and location of the explosion.
thing is ammonia nitrate explosive has longer shock wave that affects building structures much more than high explosives, watched documentary on timothy mcveigh bombing and why it is preferred explosive for purposes of terror.
Watching a video of the blast, you can see a very large shock wave in the air. A large amount of energy was dissipated this way which would not happen in a normal earthquake. I am sure the fraction could be estimated. In fact, in a fluids physics course I had the teacher said Russia was able to estimate the power of one of the first US test nuclear explosions by watching its video.
Enrico Fermi was able to do perform a similar estimate, based on the distance traveled by pieces of paper he dropped from his hand during the blast - https://en.wikipedia.org/wiki/Fermi_problem
An explosion only generates compression waves, which are longitudinal waves, like sound, where the particle motion is along the direction of motion (and back again). For earthquakes, these are known as P-waves, or primary waves, because they travel the fastest and arrive at distant locations first.
Explosions do not generate transverse side-to-side motions, which are caused by shear forces. For earthquakes, these are known as S-waves, or secondary waves, because they travel slower and arrive at distant locations later. The S-waves usually cause more damage to buildings in an earthquake, because they last longer and induce a shaking or swaying motion.
If this involved 2700 tons of ammonium nitrate, does that mean it was the equivalent to 2700 tons of TNT? A 2.7 kiloton bomb? That would put it at the smaller end of nuclear weapon yields, but not at the bottom.
> If this involved 2700 tons of ammonium nitrate, does that mean it was the equivalent to 2700 tons of TNT?
No, because ammonium nitrate isn't equivalent to TNT. Various sources give the REF of Ammonium Nitrate as 0.42, so at most it should, by itself, be equivalent to 1134 tons of TNT, but the actual explosion could be less because of inefficient ignition, or more if it set off something else that added to the explosion.
ANFO is only ~3/4 as powerful as TNT per kilogram and this was just amonium nitrate, not much fuel for it to combust (hence the nice brown smoke). Additionally, "pile of junk in a warehouse" is second only to "pile of junk not in a building" when it comes to having the least efficient yield for a given amount of explosives. Doubtful this is over a kiloton.
It's really hard to make big efficient explosions by accident.
Furthermore, this wasn't ANFO, just ammonium nitrate. So, no fuel--only oxidizer. Some analysis has suggested that the efficiency of a detonation here would only be .15. Furthermore, probably a low-order detonation (only part of the material detonating). Even actual ANFO typically needs an intermediate booster explosive to achieve a good high-order detonation. For example, instead of just having a detonator on its own a blaster might add a PETN booster charge to make sure the ANFO all detonates. Without that you typically see pellets of undetonated ANFO scattering around the explosion. Hell, even with a booster you still tend to see ANFO pellets lying around the blast area.
All that is to say, this was probably closer to 200 tons of TNT, very roughly speaking.
Ammonium ion is the fuel when pure ammonium nitrate explodes.
Adding fuel oil increases the power for a couple reasons - 1) fuel oil adds additional fuel 2) ammonium nitrate absorbs water from the atmosphere and makes it much less sensitive. The fuel oil “waterproofs” the ammonium nitrate.
According to Wikipedia the Texas City disaster had just over 2000 tonnes of ammonium nitrate explode (as opposed to 2700 in Beirut) which they claim to be “one of history's largest non-nuclear explosions”.
Was there some other factor that caused the Texas City to have a bigger blast?
If I'm reading it right, the Texas City disaster had 2300 tons on the Grandcamp, and 961 tons on a nearby ship, the High Flyer. That second ship exploded later in the day. There was also a chemical plant that was caught in the blast and a warehouse with fertilizer.
I’m assuming that USGS picks up lots of ground movement, for example, large blasts from mining operations. They must filter those out based on characteristics? Do companies give advance warning?
Just curious because those instruments must pick up a lot of things that aren’t earthquakes.
Yes, lots of explosions and other events are filtered out. It's pretty easy to classify large explosions vs. earthquakes both by the depth (earthquakes are rarely so shallow; even a big earthquake that breaks the surface will have most of its energy released 5-15 km below the surface) and by the polarity of the first seismic waves (P-waves) that reach the instruments. In an explosion, all of the waves radiating out will have the 'first motion' being a push outward, away from the source towards the instrument.
However, tectonic earthquakes are rapid sliding movements of the crust along a fault that is a quasi-planar surface. This leads to patterns in the seismic waves, where half of them, two quadrants, show a compressional push away from the source and the other two quadrants have the first motion as tensile, or a pull towards the source. By looking at the geographic locations of the seismic instruments and seeing which show a pull and which show a push, seismologists fit planes separating the quadrants which correspond to the azimuth and inclination of the fault that caused the earthquake.
(edit: deleted ascii art which did not render correctly.
Interestingly, the orientation of the fault and the quadrants of push and pull reflect the directions of the stress field in the crust caused by plate tectonic motions, as well as secondary sources of stress such as gravitational loading of the crust from high topography, or the expansion and contraction of magma chambers under volcanoes. In the 60s through the 80s, geophysicists used this information to put together the first models of the rates and directions of different tectonic plates, but we now mostly use GPS for this.
USGS eventually learn of rock quarries, mines and other things that cause regular earth movements and they tune them out of their reporting. A rock quarry near me used to generated 3.4's a few times a week. I do not know if there is regular correspondence or schedules relayed however.
I'm pretty sure blasting requires some permits. In a sane world I'd imagine blasting permits get automatically funneled into a "booms will be here" list at least at state levels. But then we don't necessarily live in a same world.
I'm not from usa, but EU. Here, mining operations, quarries, etc. get "booms will be here" licences, with limits (when (usually only daytime), where (quarry/mine limits and how strong the 'booms' are). So for those (rutine, standard blasts), our enviromental (earthquake) agencies don't get the data for each blast (they eg. get data, that company XYZ is allowed to do blasts up to ABC power (KJ or whatever) in location DEF, from 1. jan 2020 to 31. dec 2020 when they have to renew their licence).
Source: friend works as an explosives expert at a quarry
That level of permitting at least let's environmental agencies get data after the fact. If they can get the place and time range of blasts they can filter that out of their measurements. It's probably some poor intern's job. Go through a stack of permits and mark measurements likely covered by the permitted blasting.
Heh. I once wanted to dynamite my car. (It was a heap, and, you know, explosions are cool when you're young, and why not?)
I didn't need any permit. I needed: 1) to prove that I was not a felon, so that it was legal for me to have access to the explosives, 2) permission from the landowner, and 3) to inform the fire department in advance (that was exactly the "booms will be here" list).
Note that this was pre-9/11. Current rules are likely more restrictive.
> Mixing binary components together constitutes manufacturing explosives. Persons manufacturing explosives for their own personal, non-business use only (e.g., personal target practice) are not required to have a Federal explosives license or permit.
You might need to find a more remote location than a suburban backyard, however, as local authorities may have some objections too.
I don't know the rules today, but at least in some parts of the US where explosives are used liberally no permits were required at all. You definitely didn't need to inform the government. This likely varies with locale. A considerable amount of explosive in the US is purchased by private individuals for all manner of purpose and use isn't on a formal schedule.
Before 9/11, this was literally a cash and carry business in many States. You could back up a truck and fill it with explosives as long as you had a placard for your truck and a non-sparking liner. It simply isn't practical to track usage in many cases, even today.
They do require paperwork, a lot of it. One of the youtube channels I enjoy watching use every kind of demo material under the sun and they often talk about the paperwork required.
That is insane... Makes you wonder why on earth people think its a good idea to have weapons that can cause 100s of times the damage then this horrible event.
Once one person has one, they can tell everyone else what to do unless other people have them, too.
Until we find a way to alter that incentive structure, mutually-assured destruction remains one of our best-available options for tenuous stability and peace.
On the latter subject, I offer the advice of Gandalf:
Gandalf: "You cannot offer me this Ring!"
Frodo: "I'm giving it to you!"
Gandalf: "Don't tempt me Frodo! I dare not take it. Not even to keep it safe. Understand Frodo, I would use this Ring from a desire to do good. But through me, it would wield a power too great and terrible to imagine."
I was always under the impression that the one ring—a weapon so powerful it will corrupt and destroy everything good in Middle Earth—was an obvious allegory for the Bomb.
The point of the fellowship was not to study the ring, make their own, and keep the peace in Middle Earth with a mutual assured destruction. Instead they had the fellowship take the ring back to Mordor where it would be destroyed.
Tolken does not seem to share your belief that: “mutually-assured destruction remains one of our best-available options for tenuous stability and peace”.
EDIT: And neither does the United Nations. I encourage you to read the Treaty on the prohibition of nuclear weapons (and subsequently ask your government to sign it if they haven’t already) and see why the presence of nuclear weapons among our nation states is a terrifying and dangerous endeavor.
Agree. But some people will see lack of weapons as weakness to exploit. It's easier and higher ROI for 1 to arm, while rest disarm, than for all to remain disarmed, so it will happen. Making the current undesirable state where we have this fantasy of nuclear slugfest, paradoxically more stable.
But yeah, in a sense it's like we're storing AN in a warehouse beside a city. Seemingly stable, but bad if not. Unless we're not storing AN, but just sawdust. But who knows really?
an even more stable situation would be to have every country convinced they have a mutually assured destruction but then for there to be some higher power that can prevent that. so we don't start a war because we believe mad is true but even if we do there's a fallback. but who knows?
