Re: Methane threatens to bake humanity like Turkeys in an Oven


"Ian Parker" <ianparker2@xxxxxxxxx> wrote in message
news:1170773437.783266.171750@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On 6 Feb, 08:48, "George Dishman" <geo...@xxxxxxxxxxxxxxxxx> wrote:

I replied to this a few days ago but it seems to
have vanished.

As far as tidal forces are concerned. These are taken care of in your
gravitational calculation. All spacecraft to the outer solar system
have used slingshots.

Spacecraft are small, the plate is immense. Tidal
forces arise because the gravity on one side differs
from that on the other and would tend to pull a thin
structure apart.

We are well used to performing the calculations
needed to traverse complex gravitational fields.

Sure, you can calculate the force easily but you still
have to build something strong enough to withstand
those forces.

I think we are talking slighly at cross purposes. There is the L1
solution which may or may not be rigid and there is the MEO solution
which is definitely NOT rigid.

I have only been discussing the L1 approach which is
of necessity somewhat rigid. It could be a "springy"
*** that can be deformed and return to shape but
it cannot be a simple foil or mesh which is spun.

The earth orbiting solution would a Dyson Swarm but
that is a different topic entirely.

In fact MEO would work rather like the
quadrantal rule for aircraft in VFR. One orbital plane would consist
of rigid structures a few km across and at constant spacing and
different orbital planes would be at different heights (they need
differ by only 100m or so).

No, you need multiple orbital inclinations like this

http://en.wikipedia.org/wiki/Image:Dyson_Swarm.GIF

or all you do is remove a thin line from the Sun. I have
seen a great web site a few years ago where a range of
swarms had been animated but I can't find it now.

My rotation in a year was an estimate of the rough magnitude of tidal
forces on an L1 Now you can have a structure at 55Kg/km^2 in tension
quite easily, ...

No you can't. Here is the lowest areal density material
I know of

http://www.space.com/businesstechnology/technology/carbonsail_000302.html

They have achieved 5 gsm, compared to 80 gsm for typical
office paper. That is 5000 kg/km^2 (5 tonne/km^2) so
55 kg/km^2 is two orders of magnitude less than credible.

but you need a box girder type of structure for
compression. In fact you would have thin wires arranged in a fractal
like structure.

However I would like to point out a few things.

1) This approach has been advocated as an alternative to the VN
approach. With a VN appoach the weight is less important as you are
REPLICATING.

Replication is not relevant, you are making thin panels
which have no capability to reproduce because that extra
function would increase the mass. Besides which, we do not
have self-replicating technology in any form, nor are we
going to have it in the timescales of the possible methane
problem.

2) A rigid strucure is not really needed.

The material above can be folded and will restore its shape
which is what is needed. You cannot use spin for an L1
solution because the *** must stay perpendicular to the
Earth Sun line.

3) I think we have a little bit of confusion about 5km/h. It does not
matter how large a structure is. The important thing is the speed an
object attains in traversing it. If we build a brick wall 5m high at
10m/s^2 (10 = R&R 9.81) we have 10m/s or 18km/h.

Yes, and if your shield passes the Earth edge on it is 600km
"high". If the centre is in freefall, what is the gravity at
the top and bottom? What speed do you attain falling from the
centre to the bottom (the edge nearest the Earth)?

More importantly, with an areal density of 5 tonne/km^2, what
is the tension at the centre?

A tiny fraction of the cost of building smelters and
manufacturing plant to process your asteroid in
orbit. The ISS would be nothing more than a
proof-of-concept prototype for your idea.

The return to the Moon is in fact proposing just that smelters. Ca you
build a smelter that is small?

You can, but at 5 tonne/km^2, a 700km diameter shield
has a mass of nearly 2 million tonne. Unless each
smelter load has a significant mass, the loading and
unloading times become dominant and even a large
number of smelters will be too slow. Before you go
off on a tangent about replication, forget it. Smelters
don't make more smelters, they just extract raw material.

If you are talking about building a
sunshield you can have small pieces (even down to a cm^2) and small
tools. If you are talking about high temperature processes there is a
minimum size required. For low temperature processes you cut the
sizeProbably the best answer within current technological capabilities
is to heat by directing sunlight onto the furnace.

Again, that is all sci-fi wishful thinking, we don't
have low temperature processes for separating rocks
into their constituent element and we aren't going
to have them any time in the next couple of decades.

As I have explained nanotechnology is suspect because we want to build
any CAD/CAM object which is compliant, but it is useful for certain
processes. Clearly the further we can minaturize the basic seed the
lower will be the launch cost. Of corse because of thermal
considerations a high temperature process has an intrinsic size.
Throughout the years the size of electronic components has steadily
gone down,

Yes, but the temperature needed to grow a silicon
crystal hasn't changed.

but we have a long way to go to DNA where a sperm contains
4GB (a DVD).

A far lower sum
would bring capabilities up. You are right though to focus on the low
level of achievment of NASA.

I never mentioned them, you keep ranting on about
them. I'm not interested in your political ravings.

I think it iss fair comment.

Given that you need a space-based manufacturing plant
capable of processing millions of tonnes of material
in just a few years, the ISS pales into insignificance.
It is a tiny proof-of-concept demonstrator, and cost
efficiencies on your vastly larger plant would be even
worse. It is unlikely it could survive in low orbit and
probably construction at an Earth moon Lagrange point
or farther away would be essential to avoid tidal force
problems.

....
but then neither could an astronaut.

Yes he could, he could unwind the coil, fix the break
and rewind it. I've done that. The whole point is that
a robot can only do the repairs it was designed for
in advance while a human can improvise. It's not
about inteligence, the difference is dexterity.

In fact the
example you give is a rather poor one because car firms like Ford
ALREADY have a plug into which you can place a probe and a computer
then dianoses the fault.

Yes, and then a humnan has to do the repair, that's
the part you are missing all the time.

No not if we have a flexxible robot.

We don't.

We are not talking here about emotion or any real deep thought
process, ..

Right, we are talking about the ability to do physical
changes to hardware.

Yes.

we are simply talking about analyzable dynamical systems. In
fact a task can be viewd as the solution of equations something that
has been done for yonks.

Solving equations never repaired a toaster.

You have to get inside the toaster. To do this you need to perform a
series of operations. You do not need to solve equations to do them
slowly (a stepping motor can stop between each click. However to do
things with human dexterity you sure do. To repair a toaster quickly
you need to be able to lift the toaster and take it to bits moving
fast. Fast here means not being able to stop in a click but getting
the coodinates of start and destination and plotting a course. This
can be done. Watching gymnastics I recall Cassini - flybys at Venus -
Earth - Venus - Jupiter before going on to Saturn. Clearly it is
possible to work out a complex trajectory.

Sure, we can calculate all sorts of complex stuff, but
a calculation never repaired a toaster, you need the
ability to manipulate material before any of that is
of any use.

No it isn't! Point is that an asembly from pre prepared components can
be viewed as a dynamical task. ....

Point is - there are NO pre-prepared components! All
you have is a few boulders and maybe some ice. It
is getting from that to the parts that is the task. Bolting
the parts together is trivial.

You need a seed which consists of a VN swarm. How big this seed is
depends on a number of things - see above.

You still have your head in the sand. A seed is of
no use whatsoever unless there are pre-processed
raw materials in a form that can be assembled into
a copy of the seed, and they don't exist.

Stanford and Cornell are doing a great job - don't get me wrong.

I agree, but the fact remains that there is a huge gap
between where they are now and what is needed to
manufacture anything using atomic scale methods.

You don't need atomic scale models.

Yes you do. Either that or large plant with multiple
stages to smelt and refine rubble into usable material
followed by a series of piece-part manufacturing
processes and finally assembly. Bacteria and enzymes
and other molecular processes are the only way to
extract minerals at low temperature.

You need macroscopic CAD/CAM. In
my book you are STILL macroscopic even if components are a few microns
across. See above. In fact atomic scale (a DVD on a sperm) is a
DISADVANTAGE. In fact Stanford's work is IKEA/B&Q sized.
My
only criticism is that Andrew Ng to take an eample is also qworking on
linguistics - writing some great papers by all account. However we
would move faster with a TOTALLY DEDICATED effort. I think people like
IKEA and B&Q should sponsor students. If I were a university teacher I
would feel the need to teach a balanced AI course. To be a teacher a
Spanish, just as every teacher is "a teacher of English".

And how would that help anyone smelt alumino-silicate
rock into aluminium scaffolding poles and solar cells?

You have to build a furnace using CAD/CAM.

Nonsense. Do you think the 19th century furnaces used
CAD/CAM? Do you _design_ one with CAD if you want but
it is the "M" part where the problem lies. No amount
of "CA" will help if you don't have a way to manipulate
the matter.

I think a solar furnace is
the solution that makes the least assumttions about technology,
although a genetically engineered organism can do mineral extraction.
In fact (as I think I said in a previous exchange with you) you can
get quite a lot of DNA by carrying on up the Amazon. You can certainly
get copper as a species of horseoe crab has copper based haemoglobin.
What Greek! Haemos is iron. Haemoglobin contains iron!

Exactly, and Haemoglobin contains a _single_atom_
of iron.

The
oder of magnitude of forces at L1 will be > 5km/h. This is not an
enormous force. I talk in terms of speed since the strength required
has the dimensions of speed. I fact it need not be strong at all.

Rubbish, the typical CME has a mass of 10^9 tonne and is
moving at 500 km/s ! Your mass of 0.055 gsm is tissue
paper, fine for a small solar sail but in a non movable
configuration it wouldn't survive even the smallest CME. A
plate of hundreds of km diameter capable of surving a CME
would need to be hundreds of tonnes per km^2 and if 700 km
in diameter (I think you said 10% of the Earth diameter)
would be 35 million tonnes at 100 tonne/km^2 and more
likely to be a billion tones.

Does this matter if you have replication?

We don't.

Smelting that much aluminium out of asteroidal rock
is not going to be done by Sonic the Hedgehog, even
if he can use Javalink.

2, 4 8 etc. Sonics will.

No, no matter how many you have, they remain just
pixels on a screen with no ability to influence
real matter in any way. I think you have been
playing too many computer games and are losing the
distinction between them and real life. An infinite
number of Sonics couldn't band a paper clip.

George



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