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A Side Affect of Planetary Bombardment

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A Side Affect of Planetary Bombardment
Post by Robert_A_Woodward   » Fri Oct 07, 2022 1:21 am

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I was checking the scene in _Shadow of Freedom_ where Terekhov used took out Yucel (and other unworthies) on Mobius with just one kinetic projectile. It hit at .001c (30 kilometers per second). I believe that the scene (as witnessed in _Shadow of Victory_) would be a bit more spectacular than David Weber described. That projectile had to push air out of its way to reach the ground. Air can only move at the local speed of sound. For the local speed of sound to reach .001c, the temperature has to be very high. My BOE calculation suggests about 2.3 million Kelvin (however, this is a linear calculation and at those conditions I suspect a non-linear equation is needed). The air pressure gets a bit extreme as well (over 7000 atmospheres). I haven't tried to calculate the drag since I have to guess at the dimensions of the projectile. Handwaves could project the projectile for that heat, but the surrounding cityscape would probably notice a rather bright flash and a very loud sonic boom.
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Re: A Side Affect of Planetary Bombardment
Post by cthia   » Fri Oct 07, 2022 9:48 am

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Robert_A_Woodward wrote:I was checking the scene in _Shadow of Freedom_ where Terekhov used took out Yucel (and other unworthies) on Mobius with just one kinetic projectile. It hit at .001c (30 kilometers per second). I believe that the scene (as witnessed in _Shadow of Victory_) would be a bit more spectacular than David Weber described. That projectile had to push air out of its way to reach the ground. Air can only move at the local speed of sound. For the local speed of sound to reach .001c, the temperature has to be very high. My BOE calculation suggests about 2.3 million Kelvin (however, this is a linear calculation and at those conditions I suspect a non-linear equation is needed). The air pressure gets a bit extreme as well (over 7000 atmospheres). I haven't tried to calculate the drag since I have to guess at the dimensions of the projectile. Handwaves could project the projectile for that heat, but the surrounding cityscape would probably notice a rather bright flash and a very loud sonic boom.

Interesting topic!


I have often tried to imagine the horrors for some of the survivors who are witnessing the terrible ordeal on planet.

Witnessing the terrifying sounds and quakes, if they are lucky. I thought about it quite a bit during this thread and suggested there would be tree-like sap produced by the enormous temperatures and pressures at the impact site. I wouldn't be surprised if a new element is made.

On that note: I had a friendly disagreement quite some time ago, I think with Jonathan, when I suggested that there might be new elements found elsewhere in the Universe that could enable advanced technology.

Jonathan disagreed.* Essentially he said our galaxy should contain any element of any other galaxy. IOW, there would be nothing new under the "Suns" to find. I think I argued the reality as a possibility that Darius might include elements that could make unbelievable technology possible.


Exhibit A: Nuclear fusion courtesy of the moon.


*Granted that I did not mis-remember the exchange.

Son, your mother says I have to hang you. Personally I don't think this is a capital offense. But if I don't hang you, she's gonna hang me and frankly, I'm not the one in trouble. —cthia's father. Incident in ? Axiom of Common Sense
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Re: A Side Affect of Planetary Bombardment
Post by tlb   » Fri Oct 07, 2022 10:13 am

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cthia wrote:I wouldn't be surprised if a new element is made.

On that note: I had a friendly disagreement quite some time ago, I think with Jonathan, when I suggested that there might be new elements found elsewhere in the Universe that could enable advanced technology.

Jonathan disagreed.* Essentially he said our galaxy should contain any element of any other galaxy. IOW, there would be nothing new under the "Suns" to find. I think I argued the reality as a possibility that Darius might include elements that could make unbelievable technology possible.


Exhibit A: Nuclear fusion courtesy of the moon.

Helium-3 is not a new element, just a relatively rare isotope of Helium. The reason that some heavy isotopes are rare is that they transmute by fission into lighter elements, so any previously unknown heavy element probably has a very short lifetime.
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Re: A Side Affect of Planetary Bombardment
Post by ThinksMarkedly   » Fri Oct 07, 2022 1:51 pm

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Robert_A_Woodward wrote:I was checking the scene in _Shadow of Freedom_ where Terekhov used took out Yucel (and other unworthies) on Mobius with just one kinetic projectile. It hit at .001c (30 kilometers per second). I believe that the scene (as witnessed in _Shadow of Victory_) would be a bit more spectacular than David Weber described. That projectile had to push air out of its way to reach the ground. Air can only move at the local speed of sound. For the local speed of sound to reach .001c, the temperature has to be very high. My BOE calculation suggests about 2.3 million Kelvin (however, this is a linear calculation and at those conditions I suspect a non-linear equation is needed). The air pressure gets a bit extreme as well (over 7000 atmospheres). I haven't tried to calculate the drag since I have to guess at the dimensions of the projectile. Handwaves could project the projectile for that heat, but the surrounding cityscape would probably notice a rather bright flash and a very loud sonic boom.


Oh, you can bet that any linear equations you have do not apply. I would even venture to say we don't have the proper equations for this.

From the point of view of someone on the ground, the KEW strike would not look like a meteor falling. It would look like a ray coming straight down. At 30 km/s, it goes through the entire troposphere in under a second; on Earth, it would go through both the stratosphere and troposphere in under 2 seconds. To a distant observer, it probably moves faster than lightning, is much longer (coming from a much higher altitude), and is completely straight. I have no clue whether it would look thinner than lightning or not, and whether the thunder produced by its passage would be louder than lightning's or not.

A 5 kg round impacting the ground at 30 km/s would have a kinetic energy of 2250 MJ. If we divide the speed by 100 to get 300 m/s (just under the speed of sound on Earth), a suitable terminal velocity for a missile, you'd need a round 10⁴ heavier to get the same energy: 50 tonnes. That would produce a lot of quaking. Moreover, the 5 kg round, assuming similar density, would have a 10⁴ smaller volume and probably a 10^(8/3) smaller cross-section (about 0.2% of the area), so the KEW would also penetrate much further into the soil and crust. My complete guess here is that this would make the quake smaller than a 50-tonne round, because it dissipates a lot of energy while going deeper.
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Re: A Side Affect of Planetary Bombardment
Post by ThinksMarkedly   » Fri Oct 07, 2022 2:04 pm

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tlb wrote:Helium-3 is not a new element, just a relatively rare isotope of Helium. The reason that some heavy isotopes are rare is that they transmute by fission into lighter elements, so any previously unknown heavy element probably has a very short lifetime.


It's also rare on Earth, because Helium is a noble gas and won't bind to anything else, unlike Hydrogen. Both Helium and molecular Hydrogen routinely escape the gravity well of Earth and fly off into space. Wikipedia says that ³He is 7.2x more abundant in the solar system as a whole than what is found on Earth. The Moon has more He-3 than Earth because, having no atmosphere, it gets replenished from the solar wind, so its surface is in a sort of equilibrium state with the relative abundance in the solar wind. On Earth, both ³He and ⁴He will fly off into space, with the lighter element doing so more easily; plus, as Wikipedia says, we actually replenish ⁴He in the crust due to alpha decay of heavy fissionable elements.

So yes, the Moon is our first source of ³He for when we have working fusion reactors because it's the nearest. But once we have proper space industry, we can extract it from other sources -- let's build some cloudscoops!
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Re: A Side Affect of Planetary Bombardment
Post by tlb   » Fri Oct 07, 2022 2:37 pm

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ThinksMarkedly wrote:It's also rare on Earth, because Helium is a noble gas and won't bind to anything else, unlike Hydrogen. Both Helium and molecular Hydrogen routinely escape the gravity well of Earth and fly off into space. Wikipedia says that ³He is 7.2x more abundant in the solar system as a whole than what is found on Earth. The Moon has more He-3 than Earth because, having no atmosphere, it gets replenished from the solar wind, so its surface is in a sort of equilibrium state with the relative abundance in the solar wind. On Earth, both ³He and ⁴He will fly off into space, with the lighter element doing so more easily; plus, as Wikipedia says, we actually replenish ⁴He in the crust due to alpha decay of heavy fissionable elements.

To be clear, it is rare compared to He-4 everywhere; in the local interstellar cloud the ratio of the two isotopes is reported as 1.6 x 10-4. There are other Helium isotopes (He-2 and He-5 through He-10) which are much rarer, because they are all highly unstable.
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Re: A Side Affect of Planetary Bombardment
Post by ThinksMarkedly   » Fri Oct 07, 2022 2:38 pm

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cthia wrote:On that note: I had a friendly disagreement quite some time ago, I think with Jonathan, when I suggested that there might be new elements found elsewhere in the Universe that could enable advanced technology.

Jonathan disagreed.* Essentially he said our galaxy should contain any element of any other galaxy. IOW, there would be nothing new under the "Suns" to find. I think I argued the reality as a possibility that Darius might include elements that could make unbelievable technology possible.


In a Sci-Fi setting, it's possible that the author invents new, stable elements with unknown properties. Star Trek has done that: during Enterprise era (the 2150s), Earth science only knew of 92 naturally-occurring elements (and that's not even entirely accurate today), but in a discussion with another species, the other mentioned hundreds of elements. By the TNG era, more than 240 natural elements were known. They've never explained what those elements are though.

It could be that they are simply heavier elements, with more protons in the nucleus. There's a hypothesis that there's an "island of stability" higher than Z=120, though nothing has ever been found there and the number keeps shifting. I'd also expect that both supernovae and neutron star collisions/mergers, which are the most energetic events in the cosmos, would have created them and therefore they should be seen in the spectra of supernovae remnants. No such has been found.

The other possibility is that it's something else other than adding more protons to the nucleus. You can divide that into using either different hadrons, different leptons, or something else entirely. The case for different leptons actually makes sense, if a stable muon or tauon could be produced. The chemical properties of elements don't come from the protons or the nucleus, but from the electrons, which just happen to exist in equal quantity as the protons so the element is electrically neutral. If you replaced the light-weight electrons with muons, those muons would be much closer to the nucleus, thus allowing for much more compact materials. But I don't think you'd want to replace electronics in general with muonics, because those muons would also move much more slowly, so your circuits wouldn't be as fast. Using muons for storage or memory might make sense, though.

You could replace protons and neutrons in the nucleus with heavier hadrons, containing the other generations of quarks. I have little clue what properties this exotic matter would have (and no, it would not have negative mass), because as I said above, the chemical properties come from the interactions of the outer electronic shell. But maybe simply having heavier nucleus is itself a property: warship armour. They may also be better as heat sinks (think stealth).

The nucleus itself may be replaced, for example with a meson. A meson/muon "atom" could be an interesting idea. There are also tetraquarks, pentaquarks, etc.

And then of course, Sci-Fi authors can invent a whole other slew of particles and properties. Star Trek has chronitons, dekyons, tetryons, and verterons. They can also invent new properties for existing particles, like for neutrinos. It's possible some quantum effects could manifest themselves in macroscopic scale, like Helium-4 being a boson.


All this said, this is not the way that RFC has made the Honorverse. The one major departure from known physics that the HV got was gravitics, which gave us hyperspace, gravity waves, tractor/pusher beams, impellers and wedges, Warshawskis and Warshawski sails, countergrav, gravity plates and artificial gravity, FTL communication over interplanetary distances, and even TWTSNBN. The wormholes are sort of an after-thought to gravitics, and partially explained by them. The rest of the HV technology appears to be within known science, be it molycircs, genetics, fusion reactors, nanites, or mind compulsion. Sure, extrapolations from known science, but they're reasonably explained by what we know.

Another very-David aspect is that he likes to give us hidden clues before they become relevant. We'd seen missile pods way back in SVW, before pods of MDMs became the front-line weapon during Operation Buttercup, half a dozen books later; Theisman appeared in HotQ but was barely a cameo until he killed OSJ. Don't forget the Hofschulte Incident, which went unexplained for a long time before we connected the dots to the MAlign.

So we can be reasonably certain that Darius having a naturally-occurring "particle of the week" is not what we'll be seeing in the remaining books.
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Re: A Side Affect of Planetary Bombardment
Post by ThinksMarkedly   » Fri Oct 07, 2022 2:54 pm

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tlb wrote:To be clear, it is rare compared to He-4 everywhere; in the local interstellar cloud the ratio of the two isotopes is reported as 1.6 x 10-4. There are other Helium isotopes (He-2 and He-5 through He-10) which are much rarer, because they are all highly unstable.


Sure, but even 1:10000 may not be such a bad deal, not when Helium is 23% of the (known, baryonic) mass of the Universe. In a group of 100,000 atoms in the universe, 90,000 will be Hydrogen, 10,000 Helium and one of those will be ³He. That's pretty good considering that everything else in the Universe is the rounding error. (Wikipedia gives the ratio at about 90.9%, 8.9% for H/He in the solar system, leaving 1322 ppm for everything else)
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Re: A Side Affect of Planetary Bombardment
Post by tlb   » Fri Oct 07, 2022 5:20 pm

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ThinksMarkedly wrote:And then of course, Sci-Fi authors can invent a whole other slew of particles and properties. Star Trek has chronitons, dekyons, tetryons, and verterons. They can also invent new properties for existing particles, like for neutrinos. It's possible some quantum effects could manifest themselves in macroscopic scale, like Helium-4 being a boson.

All this said, this is not the way that RFC has made the Honorverse. The one major departure from known physics that the HV got was gravitics, which gave us hyperspace, gravity waves, tractor/pusher beams, impellers and wedges, Warshawskis and Warshawski sails, countergrav, gravity plates and artificial gravity, FTL communication over interplanetary distances, and even TWTSNBN. The wormholes are sort of an after-thought to gravitics, and partially explained by them. The rest of the HV technology appears to be within known science, be it molycircs, genetics, fusion reactors, nanites, or mind compulsion. Sure, extrapolations from known science, but they're reasonably explained by what we know.

Thanks for the interesting discussion of exotic elements. The thing is, if they were energetically possible in our universe (not just feasible), then they would have been seen. Presumably at whatever condition could create such things, they simply do not last long enough to be seen - even more unstable than He-2, which has a half-life almost too short to accurately measure.
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Re: A Side Affect of Planetary Bombardment
Post by ThinksMarkedly   » Fri Oct 07, 2022 7:24 pm

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tlb wrote:Thanks for the interesting discussion of exotic elements. The thing is, if they were energetically possible in our universe (not just feasible), then they would have been seen. Presumably at whatever condition could create such things, they simply do not last long enough to be seen - even more unstable than He-2, which has a half-life almost too short to accurately measure.


Right. Even at a modest creation in a supernova and a not-too-short half-life, we would have seen them. That's one of the reasons the SNEWS exist: so we can point our telescopes to supernovae while they're still very early, possibly having not occurred yet.


I forgot to mention anti-matter and thus positronic circuits. AFAWK, positronic circuits would be no different than electronic ones, as electrons and positrons have exactly the same mass, aside from the direction of the current. And, of course, the fact that you have to keep those positrons away from electrons. Though there has to be a specific property that makes matter different from anti-matter for us to be here, so maybe that could be exploited, whatever it is.

Anti-matter would be a good energy storage device, if you have a safe way of handling it. In the Praxis / Dead Empire's Fall series, Walter Jon Williams has the warships' main fuel be anti-hydrogen suspended in a crystal lattice, but he doesn't describe just how that is done. Antiprotons and positrons alone would be easier because they are not electrically neutral; anti-hydrogen is.

You could also have black holes or other collapsed matter as material. Neutronium is often discussed in Sci-Fi as armour material, but our science doesn't know how to produce it. Neutrons are stable... mostly, in the nucleus. Outside of it, they decay to protons. Black holes can be created with just a stupendous amount of energy, like a Kugelblitz and Black Holes are very good matter-energy converters, the best we know of short of matter/anti-matter annihilation. If you account for the (in)efficiency of creating anti-matter, black holes are probably more efficient. And lots of Sci-Fi have used artificial black holes / singularities as FTL or regular, reactionless engines. But we have never seen neutronium (though maybe it's part of what makes dark matter!) nor have we seen black holes with sub-stellar mass. Plus, the HV does not need another reactionless engine principle nor a power source.

And of course, there's dark matter (and dark energy). We know our Galaxy has a lot of dark matter, we just don't know what it is. It's possible there are clumps of it in some systems, enough that scientists living there could make reasonable use of it. If I were to make a leap of faith, I'd say that dark matter causes grav waves in the HV. But dark matter wasn't popularly known back in the early 90s when RFC started the HV.

Add to this list magnetic monopoles.

Then you can also have materials with negative mass, however that is accomplished. That's a topic for the Gordian Division forum. I actually need to post a question about this, from a passage in The Janus File about falling up.

Speaking of, in case people have missed: The Janus File came out this Tuesday. And WJW's third book in the second trilogy of the Praxis, Imperium Restored dropped late last month. If you enjoy Military Sci-Fi with politics (and if you're here, you do or at least are not adverse to it), you'll enjoy WJW too. Though be warned, he has far more politics than David has in the HV. He actually detailed a financial / economic crisis in the beginning of the second trilogy!
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