For Questions That Don't Merit Their Own Thread

[K^2]

1 hour ago, kerbiloid said:

The glass is damaged at 2+ kPa. The same about furniture, siding, and other lightweight elements. Also such low pressure depends on reflections from neighboring buildings, etc, and does not form a plain pattern.
The roofs, drywalls need 10..20 kPa, and we can see where is this range exactly.

The outer most ring on this is 6kPa at 20T. I've highlighted the roads for you. Do you see how it barely extends past the nearest marked road?

Here is corresponding shot from video you just posted. Same roads marked in same colors.

Do you see how there is no intact structure left all the way to the road marked in blue? If this was 20T blast, areas between green and blue lines are way under 10kPa.

Do you see how buildings beyond the blue line are missing glass. Not some of it damaged, that you get at 2kPa threshold, but all of it gone, which is typical for a 5-10kPa range. Except, that range is supposed to end just past the green line.

The numbers you are providing are not matching up with pictures you are providing at this point. I don't know what else I need to do now to make you actually consider that. Do you need me to label every single building on this visual, match it up to a building on the map, get the distance, and label the estimated pressure if this was indeed 20T? Are you seriously incapable of doing this yourself for even just one building? I'll do the work for you if you're just lazy, but I'm not convinced at this point that you aren't just closing your eyes really tight when you're afraid to see something that doesn't match your preconception.

And if you think a WWII bomb can do this, you've been watching too many Hollywood movies. I gave you actual overpressure maps now. The one for 20T isn't even close.

[kerbiloid]

I can see thin lightweight constructions, glasses, abd siding smashed by the shockwave but non-damaged walls, ceilings, and balconies a road farther and just to the right from it, that ensures me that not the shockwave was so strong, but the damaged structures so weak.
 

[K^2]

11 minutes ago, kerbiloid said:

I can see thin lightweight constructions, glasses, abd siding smashed by the shockwave but non-damaged walls, ceilings, and balconies a road farther and just to the right from it, that ensures me that not the shockwave was so strong, but the damaged structures so weak.
 

Yes, but you yourself keep telling me that you need at least 2kPa for that. The outer circle on the map is 6kPa. The one further in is 34kPa. By the time you get to highway, labeled in blue, you can't possibly have 2kPa of pressure to do that damage. Not even close. You are completely contradicting yourself.

And just to add to the pile, here's another estimate based on shock propagation putting explosion at 100T.

https://community.wolfram.com/groups/-/m/t/2051264

[kerbiloid]

2 minutes ago, K^2 said:

The outer circle on the map is 6kPa.

I don't know where did you get this 6 and 34 kPa from.
2..5 kPa is a standard value from reference books.

3 minutes ago, K^2 said:

you yourself keep telling me

I don't "keep telling you". I just posted my estimation and how did I get it. I don't really care how much are you ensured.
Also online services are a poor alternative for dedicated software and maths which I would use if wasn't too lazy.
Actually, all of them are just a simplified version of civil defence algorithms.

[K^2]

6 minutes ago, kerbiloid said:

I just posted my estimation and how did I get it. I don't really care how much are you ensured.

You posted an estimate based on numbers that you guestimated from the picture, which have consequently been shown to be off by a significant margin, because you were too lazy to actually use measuring tools at the time, but once called out on it, refused to make corrections. Instead, you've claimed that WWII chemical bomb could do the same kind of damage, mentioned a bunch of literature you haven't bothered to actually cite, accused people of Beirut of mass insurance fraud, said that several professors in relevant fields aren't qualified to make assessment - basically, anything but look at other data that contradicts your assessment and see where your error could be coming from.

9 minutes ago, kerbiloid said:

Also online services are a poor alternative for dedicated software and maths which I would use if wasn't too lazy.

Of course. You're too lazy to actually do proper analysis, but not lazy enough to continue defending it, despite not going so far as to even verify your own results against other pieces of data. You always have some other resource out there that's telling you you're right, but not actually bothering to cite it. Presumably, again, because you're too lazy. But anything cited to you is wrong, because none of it is from credible enough sources. But you don't cite the ones you trust. Because, lazy. 

I've given you expected destruction maps, showing consistence with hundreds of tons, I've given you estimate of energy from seismic detection, and I've cited several sources using rate of expansion method to estimate the yield, which I've since checked. Absolutely lowest estimate any of these methods gives is 100T.

But of course, none of them can be right, because they disagree with your estimate that you're too lazy to check with proper tools, but of course it has to be right, and all these other methods are garbage. Despite one of these being famously used to estimate yield in Trinity test. But I'm sure that can't be as precise as you guessing the fireball radius from the picture and plugging that into a formula. That can't possibly be wrong.

[kerbiloid]

First of all, I'm too lazy to read every wall of text you have written about me.

But I appreciate your fascination, so feel free to continue.

Edited August 5, 2020 by kerbiloid

[K^2]

Here's another video taken from the other side of the highway, camera located just 650m or so from explosion clearly showing a building 550m away from explosion getting its side panels and roof stripped by the shock wave before camera is thrown by the shock as well.

 

[DDE]

https://www.twitter.com/roscosmos/status/1291023063404994560/

That's a big crater.

[kerbiloid]

As we can see, the building (btw, it's a silos) reflected the shockwave, so the buildings behind it are untouched, while in the opposite direction the radius doubled.

So, one should use the perpendicular distance.

***

An irony. The fire was probably caused by welding the doors and windows to protect the arrested nitrates.
If they were stolen, there would be nothing to explode.

[Gargamel]

Apparently guys, this question does, in fact, merit it's own thread.  

Let's all slide the conversation about the big boom over to this thread:

 

[ARS]

Is it possible for binary, trinary (or even higher) black hole system to exist (assuming all black holes are equal)?

[DDE]

17 minutes ago, ARS said:

Is it possible for binary, trinary (or even higher) black hole system to exist (assuming all black holes are equal)?

Both black holes being equal will not save you from losing kinetic energy to gravity waves, leading to a gradual spiralling-in and eventually a merger.

But such a system, if somehow concocted, can be stable over significant timespans. As any other configuration, it will be basically a nested series of barycenters (e.g. object C will orbit the AB barycenter).

[kerbiloid]

https://translate.google.com/translate?hl=ru&sl=ru&tl=en&u=https://ru.wikipedia.org/wiki/Галактический_центр

Quote

In 2016, Japanese astrophysicists reported the discovery of a second giant black hole in the Galactic Center. This black hole is located 200 light years from the center of the Milky Way. The observed astronomical object with a cloud occupies an area of space with a diameter of 0.3 light years, and its mass is 100 thousand solar masses. The nature of this object has not yet been precisely established - it is a black hole or another object ^[5] .

In 2018, based on observational data from the Chandra X-ray Space Laboratory in the Galactic Center, 12 low-mass X-ray binaries were discovered, one of whose components with a high probability may be stellar mass black holes. Perhaps, at a distance of 1 parsec from a supermassive black hole, which is associated with the compact radio source Sagittarius A *, there can be 10-20 thousand black holes ^{[6] [7]} .

 

[K^2]

7 hours ago, ARS said:

Is it possible for binary, trinary (or even higher) black hole system to exist (assuming all black holes are equal)?

Stellar mass black holes aren't that different from stars until you get close to them. So as long as they orbit each other far enough apart, you can absolutely have a system of multiple black holes that's going to be stable. The arrangement that would work for 3 black holes is something like Alpha Centauri, with A, B being pretty close together, but still far enough apart to not generate significant gravity waves, and C being really far out from the two, so that it basically just orbits barycenter, and is barely attached to the system.

The problem is with formation. Star turning into a black hole is a rather violent event. Consider a binary star system. The heavier of the two is going to burn through its fuel sooner and go nova first, which is a prerequisite for the remnant to collapse to a black hole. So the second star in the system has to tank a nova before it even has a chance for its own evolution to lead it to a black hole. Given that the two stars have to be pretty far apart to begin with, I'm reasonably sure the second star will survive a nova, but it will have much of its outer atmosphere stripped. That makes it way more likely to end up a white dwarf than a black hole.

There's probably a mass point where you can have two stars that are massive enough and far enough apart, that even after the first one goes nova and collapses, the second one has enough matter left to turn into a black hole after its evolution is complete. But because these are going to be rare giants to begin with, having a binary system of two such giants is probably going to be exceptionally rare.

Another possibility is capture. Normally, a black hole captures something when another object passes a little too close, and loses energy to gravity waves. From there on, that second object spirals in eventually, because it's periapsis is too low. If it was a planet or a star, it will fall apart and become an accretion disk. If it was a neutron star or another black hole, it will form a short-lived binary that will eventually create another ping for LIGO to detect. However, there is another mechanism for capture which we see often with asteroids. If one of the two black holes that we want to end up orbiting each other starts out with stellar mass companion, that companion can be fed to the other black hole, for the net orbital energy and momentum to work out for a stable binary system. The companion could be a white dwarf remnant of a former binary, which had its atmosphere stripped by the nova when black hole formed, or it can be a more conventional capture, like a neutron star in high elliptic orbit. Either way, we know these kinds of systems to exist and not be all that uncommon, so it's just a matter of encountering another black hole at just the right distance at just the right time in rotational period. Again, exceptionally rare sort of thing overall, but as vast as the universe is, and as frequent as black hole collisions we're detecting are, I'm comfortable saying these systems probably exist out there.

With all of the above said, a ternary system of black holes sounds pretty incredible. I'm pretty sure the third one would have to be a capture, and binaries are way better at capturing things into a stable orbit, but just the odds of something drifting past at just the right distance and speed and getting captured rather than consumed, while also not disrupting the inner binary... Bottom line, physics says yes, statistics makes a sour face. And I don't have nearly the background to actually give you numbers on this one in terms of how common/uncommon such a thing would be.

[Gargamel]

Alright, this is for yous that like crunching rocket equation numbers.   SWdennis recently made a video using BDarmory and only Gatling rotary cannons to launch a vessel to orbit.

I know the A-10 feels a noticeable pushback from the cannon when it fires, so is there some arrangement of cannons that could possibly get a mercury-esque sized capsule to orbit and back?  Not using them for landing, we can use a standard re-entry and parachute package for that. 

Spoiler

 

 

EDIT: Of course this would be a Kessler Syndrome Machine, but let's ignore that for the moment

Edited August 9, 2020 by Gargamel

[DDE]

52 minutes ago, Gargamel said:

I know the A-10 feels a noticeable pushback from the cannon when it fires, so is there some arrangement of cannons that could possibly get a mercury-esque sized capsule to orbit and back?

They have an ISP of 103, and a TWR of 16.

Using this calculator, I was able to achieve orbit with 1000 kg in seven stages, for a launch mass of 14558 t.

The calculator does not factor in thrust, though!

Edited August 9, 2020 by DDE

[wumpus]

Per Randal Monroe (of course.  His comics got me into KSP).  https://what-if.xkcd.com/21/

A GAU-8 Avenger has a thrust of "nearly 5 tons [US] (44kN)".  You'd need at least 3000 guns to launch, which would weigh an additional ~1250 tons of mass (so expect an additional hundred tons of mass to lift the additional guns...).

His link mainly deals with building a jetpack with Kalashnikov rifles, but also deals with more "high thrust" armament towards the end.

[ARS]

What's the form factor that's more suited for stealth aircraft? Is it the highly jagged, angular form with no smooth curves or smooth curves blending the surface seamlessly with no angular sides? Because if we compare F-117 Nighthawk with B-2 Spirit, both are stealth aircraft, yet their body design seems follow different philosophy (highly angular shape vs smooth blending body respectively)

[K^2]

7 hours ago, Gargamel said:

I know the A-10 feels a noticeable pushback from the cannon when it fires, so is there some arrangement of cannons that could possibly get a mercury-esque sized capsule to orbit and back?

The problem is you're diluting I_SP. Even ignoring the casing and heavy barrel, if you take a cartridge and remove the bullet, you'll be getting much, much better I_SP. So it's actually way more feasible to come up with a gun-type rocket that makes it to orbit firing blanks.

Using GAU-8 as an example, the rounds leave the barrel at just over 1,000m/s (incendiary), which is already kind of low if you're trying to build a space capable rocket, but this doesn't translate to I_SP directly. But it gets worse. The mass of the projectile is around 400 grams. Mass of the round of ammunition together with casing and gun powder is 690 grams. Which means the I_SP is actually just under 60s. That is absolutely pitiful.

According to Wikipedia, Mercury-Atlas 9 capsule was 1,400kg. Even if we completely ignore firing mechanisms and barrels, at 60s I_SP it would take 6.9 million tons of propellant to give you 9km/s of delta-V, which is about as small as you can get away with for orbital launch. Converting back to GAU-8 ammunition, that's over 9 billion rounds. Needless to say, once we start adding back the mass of the guns necessary to lift the capsule off the ground, we hit an exponential runaway that will lead to numbers that don't make any physical sense anymore. There are simply no materials that are light and strong enough at the same time to even attempt an orbital insertion at such a low I_SP.

If you are to simply remove the projectile from the round and make casing out of very thin plastic, you can get into neighborhood of something like 200s+ for I_SP, comparable to solid state boosters. As we all know, it's not the most efficient way to launch a rocket, but entirely achievable. Whether you can still do that using shortened gun barrels and with the GAU-8s or another gun's firing mechanism is a different question. Rockets are very good at burning through an absurd amount of fuel really fast. It looks like on paper it might be just doable. Wikipedia quotes GAU-8 average recoil at maximum fire rate at 10,000 pounds of force, while the weight of the gun is only 620 pounds. On paper, that's TWR of 16. Firing blanks with a barrel converted into nozzle, this can actually go up to above 20. That's not amazing for a rocket, but actually not terrible. So now the question is, can you build ammo store that's light enough to feed the guns you're using for thrust? I can't think of any strict lower limit that you couldn't surpass by having a bit more staging, so in theory, it sounds like it ought to be doable in principle. So long as the guns can survive the fire rate.

So with blanks, it might be feasible to build something like this using modified rounds, modified ammo feed, and modified barrels. With actual military rounds, absolutely no way.

7 hours ago, DDE said:

They have an ISP of 103, and a TWR of 16.

You aren't taking into account that the round in the store is much heavier than the bullet that gets fired, which hurts the I_SP. See analysis in second paragraph above.

[StrandedonEarth]

18 minutes ago, ARS said:

What's the form factor that's more suited for stealth aircraft? Is it the highly jagged, angular form with no smooth curves or smooth curves blending the surface seamlessly with no angular sides? Because if we compare F-117 Nighthawk with B-2 Spirit, both are stealth aircraft, yet their body design seems follow different philosophy (highly angular shape vs smooth blending body respectively)

I believe the B2 just uses a radar absorbent paint/covering, while the F-117 also uses straight lines to reflect the radar waves away from the receiver.

Come to think of it, the side of the B2 facing the ground is flat, also reflecting radar away

Not sure how the B2 fares against airborne radar

[kerbiloid]

The gun propulsion should face the fact that a gun can't shoot long.

Unless it's a stationary Maxim machine-gun with external water cooling.

***

F-117 (and F-19) was in the CGA display epoch, B-2 (1988) appeared together with VGA (1987).

The better is computer game graphics, the smoother are the stealth planes.

This makes to think, what is the primary goal of the stealth planes manufacturing: to have the planes, or to sell the games.

Edited August 10, 2020 by kerbiloid

[SOXBLOX]

Hmm. So, since these are planes, they need to be aerodynamic. But stealth puts certain demands on the shape of the plane, right? Actually, not so much. It places constraints on the shape which is visible to radar. The F-35 uses an aerodynamic moldline made primarily of composites, which are transparent to radar. The radar sees the stealth shaping underneath. The stealth shaping is angular, to break up the signal, and the composite is coated in radar-absorbent paint to further reduce returns.

So optimum stealth shaping seems to be angular, with very little exposed metal. The flying wing is also inherently stealthy, as it eliminates vertical surfaces.

[K^2]

1 hour ago, ARS said:

What's the form factor that's more suited for stealth aircraft? Is it the highly jagged, angular form with no smooth curves or smooth curves blending the surface seamlessly with no angular sides? Because if we compare F-117 Nighthawk with B-2 Spirit, both are stealth aircraft, yet their body design seems follow different philosophy (highly angular shape vs smooth blending body respectively)

Curves are generally bad for radar cross-section, but B2 is a long range bomber, so some compromises have been made for aerodynamics. Nonetheless, the shape does attempt to collocate most of the curves in a few tight patches, and there are other considerations. Lack of sharp inner angles making anything like 90°, with exception of trailing edge of the wing that doesn't make much difference, and the way the inlets and exhaust are covered, which is a big part of signature on conventional aircraft. So it's definitely more than just special paint that makes B2 a stealth bomber.

[DDE]

1 hour ago, ARS said:

What's the form factor that's more suited for stealth aircraft? Is it the highly jagged, angular form with no smooth curves or smooth curves blending the surface seamlessly with no angular sides? Because if we compare F-117 Nighthawk with B-2 Spirit, both are stealth aircraft, yet their body design seems follow different philosophy (highly angular shape vs smooth blending body respectively)

It's essentially single-hulled submarine vs double-hulled, but with radar waves instead of water. The exterior is permeable but aerodynamic, while the interior is shaped however you need it to be.

Spoiler

 

Most descriptions indicate there's an F-117-style faceted internal hull under all the layers of radar-absorbent materials and electromagnetic shielding of the B-2. F-22 et al seem to be just not as stealthy, with strategic elimination of the more reflective aspects like compressor blades being visible from the front. Stealth very much seems to be a Paretto affair, where 20% of the parts do 80% of reflections - nobody calls the various Su-27 upgrades stealth aircraft, yet Pentagon specifications for target drones indicate their signatures have been reduced tenfold relative to 'vanilla'.

[kerbiloid]

The F-35 composition, in turn, makes to ask.
If all you need to get a normal fine stealth, is to put plastic spoilers on the ugly angular F-117, why did they make us suffering in Microprose F-117 trying to not fall down on this flying grotesque, rather than make a normal plane from the very beginning and let Microprose make a notmal aircraft game...