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The Dawn Star and Chihiro

This fascinating series is a combination of historical seafaring, swashbuckling adventure, and high technological science-fiction. Join us in a discussion!
Re: The Dawn Star and Chihiro
Post by evilauthor   » Thu Aug 09, 2018 1:04 am

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Louis R wrote:A methane-breather, of course, would probably think we're insanely picky ;)


Assuming of course that the methane breather wasn't from a biosphere as metal rich as ours is and thus has to be just as picky. But of course that means their biosphere is from one of the younger generation stars just like Earth.
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Re: The Dawn Star and Chihiro
Post by isaac_newton   » Thu Aug 09, 2018 5:24 am

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Louis R wrote:1. Those sorts of numbers are actually typical of Himself's style of space opera [I may have had some influence on the public discussion of the 'siphon effect' of Honorverse impeller drives when I and others posted calculations showing that each of 8th Fleet's ships would have had to fuse its entire mass in hydrogen to make the approach to Barnett on internal power. Probably not, of course, since he knows what we're like and would have realised the ammunition he was handing us with that description], which is one reason authors bury them in the bushes: avoids the accusations of implausibility from people who figure that if we can do it, it can't be done. You have to remember that _both_ sides have those power levels to play with, though, so it comes out pretty even in the end.

2. Not planetary-formation theory per se: while the very first stars to form in a galaxy would not have had any planets, because there wasn't yet anything to make them from - and do indeed seem to have formed by slightly different mechanisms for the same reason, it's thought that later generations formed in essentially the same way that we see in operation today. And planets appear to fall out the bottom of the blender almost automatically. However, the oldest of them have very low metallicities as a rule, which means that there wouldn't have been very _much_ material to make planets from and the planets that did form would be [this is my speculation, BTW] tiny and/or ice balls, rather like very large comets. The stars of the galactic halo are precisely those old, low-Z stars, meaning that the ones still shining are small very-late K or M dwarves with planets that are either warm and _very_ dry or dimly-lit and cold. Neither condition is as exclusive of life as some have assumed, but any life is going to be built around biochemistries that aren't as dependent on atoms heavier than iron - or between neon and iron, for that matter - as ours is. We won't be looking to settle, or even hide, out there because from our point of view there are _no_ resources to exploit. A methane-breather, of course, would probably think we're insanely picky ;)




yet more cogent explanations - thanks :-)

I guess that our planet hunters have not yet 'reached out' as far as the halo in their searches - I'm assuming that they are working from the nearest stars out...

On the energy levels - I guess it was more a gut feeling that the descriptions in OAR especially of the early days just didn't seem to tie up with the energy levels for planet moving - sort of like comparing the start of the Lensman series with the stuff at the end - if Himself will pardon the comparison!! :lol:
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Re: The Dawn Star and Chihiro
Post by isaac_newton   » Thu Aug 09, 2018 4:44 pm

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On the sibject of detecting faint objects I was just listening to a BBC science prog, so hope I got the details right!

They were talking about the New Horizon probe, whose last task is going 'near' a Kuiper Belt object nicknamed Ultima Thule.

This object is apparently about 30km in diameter and is at around 46AU [382light min] distant.

It has a magnitude of around 27! They think that it has a reflectivity of about 10%.

One thing that fascinated me was a throwaway line saying that this equated to about 144 photons falling on the Hubble telescope [not sure over what period].


that sort of puts some perspective on the problem involved in detecting a stealth ship in such an orbit - these far out orbits might be much better than hiding in a near asteroid type path.

BTW what sort of size do we think that the fleet ships would be?
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Re: The Dawn Star and Chihiro
Post by Kael Posavatz   » Thu Aug 09, 2018 4:50 pm

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isaac_newton wrote:
that sort of puts some perspective on the problem involved in detecting a stealth ship in such an orbit - these far out orbits might be much better than hiding in a near asteroid type path.


Except if the thing you are hiding is supposed to be a tech-booster, it is easier to build a vehicle capable of generating a zero/zero intercept with an object in a floating rockpile that is nearby compared to a rockpile that is way the hell and gone. And by the time your (space) refugees are looking for the tech-booster, you want to get it into their hands as quickly as possible so that they can start preparing themselves for the very existential threat out there.
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Re: The Dawn Star and Chihiro
Post by isaac_newton   » Fri Aug 10, 2018 4:00 am

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Kael Posavatz wrote:
isaac_newton wrote:
that sort of puts some perspective on the problem involved in detecting a stealth ship in such an orbit - these far out orbits might be much better than hiding in a near asteroid type path.


Except if the thing you are hiding is supposed to be a tech-booster, it is easier to build a vehicle capable of generating a zero/zero intercept with an object in a floating rockpile that is nearby compared to a rockpile that is way the hell and gone. And by the time your (space) refugees are looking for the tech-booster, you want to get it into their hands as quickly as possible so that they can start preparing themselves for the very existential threat out there.


unless there is a 'come home' now signal that could be sent from Safehold :-)
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Re: The Dawn Star and Chihiro
Post by Randomiser   » Fri Aug 10, 2018 10:00 am

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RFC has, absolutely definitively, said that, "The Hamilcar is gone." :twisted: :twisted:
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Re: The Dawn Star and Chihiro
Post by evilauthor   » Fri Aug 10, 2018 11:39 am

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Randomiser wrote:RFC has, absolutely definitively, said that, "The Hamilcar is gone." :twisted: :twisted:


Of course, "gone" at bottom just means "not present", not "can never come back".
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Re: The Dawn Star and Chihiro
Post by Kael Posavatz   » Fri Aug 10, 2018 2:50 pm

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evilauthor wrote:
Randomiser wrote:RFC has, absolutely definitively, said that, "The Hamilcar is gone." :twisted: :twisted:


Of course, "gone" at bottom just means "not present", not "can never come back".


The Hamilcar is gone. But we already know that at least one of the Pei's had gone off-script once (or a hundred-something times, depending on how you count). Has there been a definitive statement that there isn't a, um...third string on that bow somewhere?

I ask, because if Nimue&cave are essentially a backup, offsite, super-secret-just-in-case-someone-rips-up-the-OpPlan stand-in for the Alexandria Enclave, does it maybe-sorta-kinda follow that there might possibly be a similar backup for Hamilcar? :D
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Re: The Dawn Star and Chihiro
Post by evilauthor   » Fri Aug 10, 2018 3:46 pm

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Kael Posavatz wrote:The Hamilcar is gone. But we already know that at least one of the Pei's had gone off-script once (or a hundred-something times, depending on how you count). Has there been a definitive statement that there isn't a, um...third string on that bow somewhere?


From what I can tell, EVERYONE in the Command Crew went "off script" one way or another.
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Re: The Dawn Star and Chihiro
Post by Louis R   » Fri Aug 10, 2018 4:04 pm

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It's more fun than that, really: the thin disk is embedded in the thick disk is embedded in the halo. So there are quite a few nearby stars from both systems - the three are distinguished primarily by dynamical properties,although once you start sorting them the other differences really do stand out. So there are a few stars that _could_ be disk, from their orbits, that are classed as 'probable halo objects' due to age and metallicity and what-have-you.

However, you're right. If you look at the Kepler field, for example, you'll see that it's just above the galactic disk where it catches a large thin-disk sample but relatively faint objects aren't lost against the essentially unresolvable mass of stars. There will still be plenty of stars from the other groups in the field, though, so they are being sampled already.

BTW, if I were trying to hide from the Gbaba, I'd want to be as close to the galactic plane as possible on a line between them and the bulge - it doesn't matter how good your sensor tech is, if there are 17,000 stars per pixel in the line of sight you are _not_ going to see the one that's a bit off. Of course, it's a safe bet that the Gbaba know that too, so it's just as well that the bulge is big and figuring out _which_ line is very much a guessing game.

isaac_newton wrote:
Louis R wrote:1. Those sorts of numbers are actually typical of Himself's style of space opera [I may have had some influence on the public discussion of the 'siphon effect' of Honorverse impeller drives when I and others posted calculations showing that each of 8th Fleet's ships would have had to fuse its entire mass in hydrogen to make the approach to Barnett on internal power. Probably not, of course, since he knows what we're like and would have realised the ammunition he was handing us with that description], which is one reason authors bury them in the bushes: avoids the accusations of implausibility from people who figure that if we can do it, it can't be done. You have to remember that _both_ sides have those power levels to play with, though, so it comes out pretty even in the end.

2. Not planetary-formation theory per se: while the very first stars to form in a galaxy would not have had any planets, because there wasn't yet anything to make them from - and do indeed seem to have formed by slightly different mechanisms for the same reason, it's thought that later generations formed in essentially the same way that we see in operation today. And planets appear to fall out the bottom of the blender almost automatically. However, the oldest of them have very low metallicities as a rule, which means that there wouldn't have been very _much_ material to make planets from and the planets that did form would be [this is my speculation, BTW] tiny and/or ice balls, rather like very large comets. The stars of the galactic halo are precisely those old, low-Z stars, meaning that the ones still shining are small very-late K or M dwarves with planets that are either warm and _very_ dry or dimly-lit and cold. Neither condition is as exclusive of life as some have assumed, but any life is going to be built around biochemistries that aren't as dependent on atoms heavier than iron - or between neon and iron, for that matter - as ours is. We won't be looking to settle, or even hide, out there because from our point of view there are _no_ resources to exploit. A methane-breather, of course, would probably think we're insanely picky ;)




yet more cogent explanations - thanks :-)

I guess that our planet hunters have not yet 'reached out' as far as the halo in their searches - I'm assuming that they are working from the nearest stars out...

On the energy levels - I guess it was more a gut feeling that the descriptions in OAR especially of the early days just didn't seem to tie up with the energy levels for planet moving - sort of like comparing the start of the Lensman series with the stuff at the end - if Himself will pardon the comparison!! :lol:
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