2.) Build a pressurized assembly bay attached to the LEO station.

This is our first opportunity to test out vacuuum vapor deposition.
I foresee an inflated spherical mylar balloon with prefabricated
airlocks and connecting tunnels already installed.

The workers now work to perfect the technology by covering the
sphere with a uniform layer of metal.

This bay will be used for the future assembly of orbital transfer
vehicles, other complicated structures, for storage of components
that can't be exposed to vacuum, and for a real fun place to zoom
around in without a spacesuit :)

I think that this bay will be necessary because of the difficulty in
working in a spacesuit.

Furthermore, this can serve as an early platform for testing
procedures in fabrication that will be faced in the Space
Manufacturing Facility in the future.

TangoMan

> 2.) Build a pressurized assembly bay attached to the LEO station.

> This is our first opportunity to test out vacuuum vapor deposition.
> I foresee an inflated spherical mylar balloon with prefabricated
> airlocks and connecting tunnels already installed.
Alternatively they may be attached as soon as the first half millimeter of metal has been deposited. They may have a sort of collar attached to them, and this will permit them the easier to be welded together with the hull as the VVD proceeds.
How do you imagine the VVD equipment? An elongated bulb with a hole in one end, metal dust or fragments deposited inside, the bulb spins to keep the unboiled metal inside as well as to be evenly heated by the parabolic mirror? In order to be able to move it more freely, we use both a primary and a secondary mirror, so that the bulb needs not be in the focal point of the primary mirror?

> The workers now work to perfect the technology by covering the
> sphere with a uniform layer of metal.
If it becomes fairly easy to extract pure metal, whether dense ones like nickel-iron or light ones like alu, we may want to build the colony hulls of pure metal. Perhaps building the pressure hull turns out to be the easiest part of the task, and so, people in the High Frontier may have more spacious surroundings than we imagine today.
As for the assembly bay (or dry dock) of the initial LEO station, there is one easy source of metal, if we use ELVs.

Jon L. Beck.

--- In ssi_list@... "Raven"
>
> > 2.) Build a pressurized assembly bay attached to the LEO station.
>
> > This is our first opportunity to test out vacuuum vapor
deposition.
> > I foresee an inflated spherical mylar balloon with prefabricated
> > airlocks and connecting tunnels already installed.
> Alternatively they may be attached as soon as the first half
millimeter of metal has been deposited. They may have a sort of
collar attached to them, and this will permit them the easier to be
welded together with the hull as the VVD proceeds.
> How do you imagine the VVD equipment? An elongated bulb with a
hole in one end, metal dust or fragments deposited inside, the bulb
spins to keep the unboiled metal inside as well as to be evenly
heated by the parabolic mirror? In order to be able to move it more
freely, we use both a primary and a secondary mirror, so that the
bulb needs not be in the focal point of the primary mirror?

Can you eleaborate on your vision? I ned some more detail to
visualize it more accurately.

>
> > The workers now work to perfect the technology by covering the
> > sphere with a uniform layer of metal.
> If it becomes fairly easy to extract pure metal, whether dense
ones like nickel-iron or light ones like alu, we may want to build
the colony hulls of pure metal. Perhaps building the pressure hull
turns out to be the easiest part of the task, and so, people in the
High Frontier may have more spacious surroundings than we imagine
today.
> As for the assembly bay (or dry dock) of the initial LEO
station, there is one easy source of metal, if we use ELVs.
>
> Jon L. Beck.

I considered ELV dismemeberment as a source of metal but was unsure
about the equipment needed to break them down into usuable chunks,
dust, etc. So I've opted to just bring the metal to orbit via
shuttle launch and have it in forms of bricks of solid or alloyed
material.

Can you elaborate on what machinery you envision being used for the
ELV breakdown? Would you put the launch and assembly of this
machinery at at earlier stage? How many launches would it take to
assemble? How long would it take to break down a ELV so that we
could use it for VVD of the assembly bay?

TangoMan

> > How do you imagine the VVD equipment? An elongated bulb with a
> > hole in one end, metal dust or fragments deposited inside, the bulb
> > spins to keep the unboiled metal inside as well as to be evenly
> > heated by the parabolic mirror? In order to be able to move it more
> > freely, we use both a primary and a secondary mirror, so that the
> > bulb needs not be in the focal point of the primary mirror?

> Can you eleaborate on your vision? I ned some more detail to
> visualize it more accurately.
I imagine something somewhat similar to a Bessemer bulb. That's the one in which raw iron (which is much too high in carbon to be steel) is molten, and air is bubbled through the molten iron to burn off the carbon, thus making steel in bulk quantities. The Bessemer bulb is a container with an opening in the top and air inlets in the bottom. When the molten iron is low enough in carbon, the bulb is tipped to pour the steel. The burning of the carbon provides the heat to keep the process going once the iron has been molten.
I imagine a VVD bulb somewhat like that. An egg-shaped container of a material with a rather higher melting point than the metal it will vapourize. The hole is in the narrow end. The bulb is caused to rotate around its long axis - the axis of rotation passes through the hole - so that the metal dust or ingots inside do not float out of the hole in microgravity, and so that it is heated evenly. The heat is provided by a parabolic mirror, or more than one, concentrating sunlight.
But having only one mirror, the primary concentrating one, will force the VVD bulb to remain in the focal point of that mirror, which will make the set-up clumsy if you want to illuminate a portion of a large object with the vapour beam. Now think of the various types of reflector telescopes that we have. Newton's first one had one secondary mirror to reflect the image away from the axis of the parabolic mirror, so that the astronomer wouldn't have to stick his head in front of it. Another configuration is, IIRC, the Coud set-up, which has *two* secondary mirrors. The light from the object the astronomer is looking at is reflected from the primary mirror to a secondary, and then on to a third mirror, and *thence* onto the actual instruments such as cameras. This set-up has the advantage that the instruments, which may be heavy, need not move as the telescope tracks the observed target.
A similar set-up may be used with the VVD job. The primary mirror, via the secondary ones, illuminates the VVD bulb until it is hot enough that the metal inside melts; in vacuum, this implies that it also is vapourized. The metal vapour is let out through the opening. The vapour beam is not a very narrow one, so the bulb needs to be fairly close to the object being worked on. The sun is not a point source of light, so the light path from the primary mirror to the bulb must also be fairly short. The vapour beam is caused to illuminate the portion of the hull that is to be thickened.
For a large hull, several of these bulbs and attendant mirrors may be used simultaneously, illuminating several portions of the hull. Just turning up the heat may cause the vapour deposited to be so hot that many of the metal atoms fail to stick to the hull, and escape instead. But of course for a small test job, a single VVD bulb and attendant mirror array must suffice.

> I considered ELV dismemeberment as a source of metal but was unsure
> about the equipment needed to break them down into usuable chunks,
> dust, etc. So I've opted to just bring the metal to orbit via
> shuttle launch and have it in forms of bricks of solid or alloyed
> material.
But breaking up an ELV upper stage will provide us with gratis metal. In terms of launch costs, this would give us a hull for almost free, if it is kept small enough that the metal in the upper stages suffices.

> Can you elaborate on what machinery you envision being used for the
> ELV breakdown? Would you put the launch and assembly of this
> machinery at at earlier stage? How many launches would it take to
> assemble? How long would it take to break down a ELV so that we
> could use it for VVD of the assembly bay?
I cannot elaborate very well. I do know, with experience from my own power tools, that cutting up thin sheets of metal is fairly easy on the ground. Presumably you could saw an ELV hull up in a fairly short time, extracting metal sheets of sizes similar to, say, A4 or A3 sheets of paper. These could be crumpled up and put inside the bulb. If the upper stage burns hypergolic propellant, it needs to be well ventilated through tanks and ducts first, of course, since these propellants tend to be less than savoury for the human organism ---
One thing I imagine is that we may launch something similar to a MIR core module, and then build a four or eight meter diameter sphere in the way that you described in your initial post. Add it to the core module, and you have a space hotel, which may cover at least some of your costs. Add perhaps a narrow drum that spins inside the sphere, so slowly that you may simply float onto it in microgravity, and attach yourself to it. It provides a miniscule gravity, enough to take a shower, eat food that isn't all thick gravy with lumps in it, drink from a glass, use a toilet, put small items on a table and not constantly herd them like wide-awake kittens whose eyes have opened, such things.
One weakness of the VVD method is that it doesn't seem to easily enable well.defined edges, such as if you want to build two dry dock halves that may be clamped together and be airtight. So I suppose a wholly closed module (except for the connection tunnels and windows, protected from the metal vapour beam by screens during construction) is best to begin with. Then we can build the more challenging dry dock, if the first attempt didn't prove too hard. The dry dock may be a cylinder, with one end cap detachable: a large hull with a small door is easier to build than a large hull with a large door.
But probably mr. Radley will tell us that the concept has no chance, since the national space agencies of the west will fight against it nail and tooth. :-)

Jon L. Beck.

> 2.) Build a pressurized assembly bay attached to the LEO station.

Yes. Makes sense to me.

> This is our first opportunity to test out vacuuum vapor
> deposition.

I would hope that we'd've tried it out on a smaller scale before
using it for a vital (and big) component. But I see that you also
mention...

> I foresee an inflated spherical mylar balloon with prefabricated
> airlocks and connecting tunnels already installed.

Yes.

> The workers now work to perfect the technology by covering the
> sphere with a uniform layer of metal.

Another possibility is to pipe a gas (maybe even excess oxygen) into
a blob of molten metel or glass. Like glassblowing. I wonder if
this will be better for some structures, and VVD for others. And
perhaps the "ziscos" (or whatever you would call a zero-G disco)
attached to the hotels have allowed us to get some practice in.

> This bay will be used for the future assembly of orbital transfer
> vehicles, other complicated structures, for storage of components
> that can't be exposed to vacuum, and for a real fun place to zoom
> around in without a spacesuit :)

heh heh...

Which is why the hotels will have them. But we might one that is
larger than what they have built, and which need to open up to allow
the "undocking" of fairly large components.

> I think that this bay will be necessary because of the difficulty
> in working in a spacesuit.

I suspect that you are right. Of course, spacesuits (and methods of
working in them) can be improved, but perhaps only so far, thus
something like this drydock may well be needed.

> Furthermore, this can serve as an early platform for testing
> procedures in fabrication that will be faced in the Space
> Manufacturing Facility in the future.

Yes. Our drydock may be a bigger, more versatile version of the
ones used to build the hotels and such.

> TangoMan

Xenophile (humming _If I Was A Rich Man_)