Dafydd Neal Dyar (dafydd@dyarstraights.com)
Thu, 29 Mar 2001 17:26:03 -0800


On Wed, 28 Mar 2001 12:59:54 -0800 (PST), Chien Ting Chien (Dr. Core) wrote:

> Correct me if I am wrong (I am losing memory in my advanced age :) Didn't
> we calculated that the colony drop (using sensible mass of the
> colony cylinder) should be only about 60-600 megatons?

We did indeed, but that doesn't change the established figures or their
relationship to the observed effects. Even if we discount the impact force, we
should accept the size of the crater as a given instead of taking calipers to
every map or illustration.

> There are several things that I am pretty sure you are wrong here.
>
> 1. Massive impact may or may not be more likely (compared to nuclear
> blast) to vaporize and plasmarize rocks. But vaporized rocks and plasma
> are definitely more likely to cause climate change. Most of the
> simulation models focus on submicron particles, which are formed from
> vaporized rocks and plasma. Particles larger than 1 micron clear out of
> the atmosphere fairly quickly due to gravity and rain. See the second
> link in my previous post about this.

No argument here. I was merely observing that there's a lot more to consider
here than displaced mass. The degree of reduction -- particulate, gas,
plasma -- will have an effect on distribution that we can't predict or even
determine without knowing the exact conditions at impact. Some of the material
will be blown back up into orbit, some will circle the globe and fall right back
into the crater -- it's the amount of each that's important and we have know
way, other than statistical methods, to make even an educated guess.

Again, my point was that you can't just measure the crater and say "That's how
much stuff we have in the atmosphere!"

> 2. Nuclear blast and asteroid impact(*) are not hot enough to cause rocks
> (Si, O, Ca, K, P, N, Fe, Cu etc) to split or fuse atomically.
> Plasmarization is as far as you get. Nuclear blasts make rocks
> radioactive by neutron (and sometimes proton) bombardment, which is a
> nasty thing for living creatures. But neutron bombardment doesn't affect
> climate directly. I doubt asteroid impact can make anything radioactive.
>
> (*) I am 99% sure that even an impact big enough to break Earth into a
> million pieces is not hot enough to split or fuse the atoms making up
> rocks. You can do the lightest and heaviest elements (H, He, U, Pu etc)
> but not the middle elements.

I was thinking as much of the colony's constituent elements, and those of Sydney
and the surrounding ocean, as of the rocks. I was also think of the point of
impact, not a general extension to the mass as a whole. At the point of impact,
assuming the full 60,000 megaton yield, submolecular amounts of the various
lighter and heavier elements would, in my estimation, become sufficiently
energetic to fission and fuse. (I distinctly remember specifying "lighter" and
"heavier" and I was thinking as heavy as Nitrogen -- H, He, Li, Be, B, C, N --
on the light end and as light as Radon -- Rn, Fr, Ra, Ac, Th, Pa, U -- on the
heavy end, but I'd be willing to scale back to, say, Boron and Radium as the
delimiters.)

And I may have used the word "radiation" unadvisedly. I was thinking of thermal
and electromagnetic radiation -- heat, light, electrical energy, magnetic
flux -- not nuclear radiation. That said, there would be minute amounts of
gamma, x-ray, neutron and neutrino emission from any fission or fusion, although
you'd be hard put to detect it after the fact.

> 3. If any bits of matter is converted into pure energy, then by Einstein's
> famous E = mc^2 equation, it would make the climate change even more
> disastrous. Putting any extra energy into the mix could only kick up even
> more dust into the air, and as I said, vaporized rocks are bad bad bad.

Excuse me, but nuclear fission occurs all around us all the time and we hardly
notice it -- it's called atomic disintegration. I think we already went over
the per-atom yield of helium^3 and deuterium fusion, which isn't such a much on
the submolecular scale I had in mind. Yes, a gram of matter converted entirely
to energy all at once would be devastating, but that's not what I envisioned
here. which was merely a modest rise in the overall temperature and energy.

Again, my point was that you can't just look at the volume of material and come
up with a global effect. There's a lot of stuff going on here, a lot of
heterogeneous mass that doesn't equate to anything we've ever seen before.

Hence my suggestion to look at processes, such as volcanic eruption, that we
have seen and measured directly rather than theoretical processes based on a few
isolated tests.

> Well nuclear blast is a bad example because it's too concentrated and too
> hot (I think), seismic and volcanic events are also bad example because
> they are too distributed and too cold. Best example is of course asteroid
> impact. The only difference between asteroids and colony/space station is
> that colony cylinders and space stations are mostly hollow.

Since we've never actually seen an asteroid strike, it's still largely
theoretical. The last such event was the Tunguska explosion on 30 June 1908,
which wasn't even identified as an impact event until sixty years after the
fact. They're still arguing over what it was, comet or meteoroid, much less how
big it may have been, so we still don't know the parameters.

Oh, and here's a thought. Colony cylinders are mostly air surrounded by a thin
shell of titanium reinforced concrete with a layer of soil around it, but
they're also home to who knows how many Minovsky-Ionescu compact fusion
reactors, charged solar cells, fuel cell driven electrical motors and other
volatiles too numerous to mention. What does that do to your comparison with a
dead piece of rock, nickel iron or hydrocarbon?

> In fact, historically the nuclear winter scenario was proposed from the
> hypothesized asteroid impact that caused mass extinction that killed a
> huge number of plant and animal species, including the dinosaurs. As I
> understand it, the asteroid impact => dinosaurs extinction scenario was
> 90% confirmed but still debated amongst some scientists, but asteroid
> impacts causing multiple episodes of climate changes and mass extinctions
> is pretty much accepted by everyone.

Still, the only such impact we've ever witnessed and measured with any degree of
accuracy was the Shoemaker Levy 9 hitting the atmosphere of Jupiter. It's still
all theory and no hard objective data.

> Where the hell did you get the orbital data??? I suppose you can find
> some info from freeze-framing 0083, but you obviously got more data from
> other sources.

The colony drop orbits are well documented in the various backgrounders that
have appeared in the Japanese language Gundam books.

And I may have misspoken about the direction of the Operation Stardust drop -- I
assumed that it was traveling north from the POV of General Kowen and his
escorts as it passed overhead at Jaburu, but we don't know what direction they
were facing and it could just as easily have been going the other way. That's
what I get for relying on my memory of the scene instead of looking it up.

According to the diagram in MS WARS: Mobile Suit Gundam 0083 (1991, Kodansha,
ISBN4-06-103284-4), the trajectory of Island Ease in 0083 is almost exactly the
same as Island Iffish in 0079. After passing over Jaburu, the colony went
three-quarters of the way around the world, dropping on North America on its way
to South America.

All I can say is that it must've been deflected into a near-polar orbit on that
last pass, as a Great Circle from central Brazil to the American heartland is
only inclined about 12 from a pole-to-pole orbit.

> Anyway I still argue that (1) colony drops shouldn't make such a big
> Sydney crater, (2) if a crater as big as Sydney were made, then you can't
> avoid a drastic change in Earth's climate and the ecosphere.

I agree with both points and, in fact, all of the original Gundam backgrounders
cited "drastic climatic changes" subsequent to Operation British. They just
never went into specifics as to what those changes were and we saw precious
little evidence of it other than some cratering across North America, which is
accounted for by the three pieces of Island Iffish that hit there. Yes, there
are deserts, but they're the same deserts that are already there in AD 1979.
There are also idyllic tropical paradises and no one but no one complains about
the miserable weather.

> PS: since you are the expert, can you enlighten us about the colony's mass
> compared to Mir? Also only 27 out of 100+ ton of Mir reached sea level,
> do you expect a higher ratio with a colony? The answer is obviously yes,
> but how much?

Mir only massed 137 tonnes (153.44 tons), of which only an estimated 20 tonnes
(22.4 tons) made it all the way down to the Pacific, where it was scattered over
a 1,500 km (932 mile) stretch between New Zealand and Chile, although the bulk
of it came down within the 125 km target zone at 44.2 S by 150.4 W. It
started from an altitude of 216.8 km (134.7 miles) with an orbital velocity of
about 27,360 kph (17,000 mph = Mach 23), but was slowed by a number of
controlled burns and began its fall from an altitude of only 100 km (62 miles)
and a speed of only about 15,000 kph (9,320 mph = Mach 12.5).

By comparison, just the docking port/industrial block of a colony cylinder is a
cubic kilometer of titanium reinforced concrete, massing in the megaton range,
entering the atmosphere at something akin to Mir's velocity before the slowed it
down.

"Whether the pitcher hits the rock or the rock hits the pitcher, it's going to
be bad for the pitcher" --Sancho Panza, Don Quixote de la Mancha (Miguel de
Cervantes Saavedra, 1614; as translated by John Ormsby, 1885)

> PPS: [OT] I just like to counterbalance a bit the negative press given to
> the Mir drop. The Russians did an excellent job controlling the drop. I
> am not so sure NASA could have done as well. Imagine if NASA mix up
> metric and imperial again...

We'll find out in a decade of so when they're done with the ISS, eh?

-Z-

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