Hi,
Does anybody know anything about how foams are produced and could one be
made from liquid metal in zero gravity vacuum?
I have been thinking about how to capture and use asteroid material.
The capability of spewing out a metal foam sheet or I beam a mile long
could be of greater use than the same amount of material in compressed
form: fewer viberational modes, greater cross-section, restricted
localized damage. Each of the bubbles would be pressurized and would
therefore have more strength then if made from a honeycomb type
laminate. I would think that metal foams would be very rare on earth
because gravity would swamp surface tension affects. In zero gravity
the opposite would be true.

> Hi,
> Does anybody know anything about how foams are produced and could one be
> made from liquid metal in zero gravity vacuum?

> I have been thinking about how to capture and use asteroid material.
> The capability of spewing out a metal foam sheet or I beam a mile long
> could be of greater use than the same amount of material in compressed
> form: fewer viberational modes, greater cross-section, restricted
> localized damage. Each of the bubbles would be pressurized and would
> therefore have more strength then if made from a honeycomb type
> laminate. I would think that metal foams would be very rare on earth
> because gravity would swamp surface tension affects. In zero gravity
> the opposite would be true.

> I have been thinking about how to capture and use asteroid material.
> The capability of spewing out a metal foam sheet or I beam a mile long
> could be of greater use than the same amount of material in compressed
> form: fewer viberational modes, greater cross-section, restricted
> localized damage. Each of the bubbles would be pressurized and would
> therefore have more strength then if made from a honeycomb type
> laminate. I remember being all on fire for 0-G materials processing after having read G. Harry Stine's "The Third Industrial Revolution", and regaling a college physics professor with the amazing qualities of foamed steel. He then asked why not use honeycomb laminate, since it would have many of the same features, but doesn't require a space factory. That totally took me back. But I don't know if he considered pressurization of the bubbles; there may yet be an advantage to the notion. Sincethen I read one article where someone said the problem with many of the people advocating 0-G materials processing (both inside and outside NASA) is that they're experts is space travel, not materials processing. This makes them more attuned to a possible space solution than a possible Earth-based solution which might work equally well and cost much less. Since those early years, I've come to promote other things over 0-G materials processing. I know that even O'Neill (who certainly couldn't be accused of overlooking an advantage to being in space) was fairly dismissive of such then-popular notions as "perfectly round ball bearings" etc.
Regards,

The following recent article on (terrestrially-produced) ceramic foam may
be of interest.

In John. S. lewis' book, 'Mining the Sky', he mentioned the discovery of an
asteroid trapped on one of the Lagrangian points of Mars's orbit. If similar
asteroids were found to be trapped on Earth's orbit, then asteroidal material
could be returned to Earth with virtually zero propellant requirements. They've already discovered one asteroid which follows a very peculiar orbit; one which basically horseshoes back and forth around the L-4 and L-5 points of the Earth-Sun system on something like a 70 year cycle. I remember sending an E-mail off to one of the discovers asking him what the delta-V would be from Earth.I don't recall him responding, but I suspect it wouldn't be as easy to rendezvous with as many other NEO asteroids.

More information on the asteroid (3753 Cruithne) referred to in "They've already discovered one asteroid which follows a very peculiar orbit; one which basically horseshoes back and forth around the L-4 and L-5 points of the Earth-Sun system ... Mike Combs" has a 385 year period and is 3x6 km (and therefore probably 100 billion tons). That is enough mass for lots of different industries, solar power satellites, O'Neill Colonies, trips to Mars, etc. It is some times referred to as Earth's second Moon. More details can be found at http://aries.phys.yorku.ca/~wiegert/3753.html. Sincerely, Jay Huebner

Thanks for the additional info. My memory was way off on the period. Such a lengthy period might make resource retrieval difficult, since I assume there would be only one particularly favorable point in the orbit for a rendezvous attempt. (Maybe 2 if the point of rounding either L point happens to be good. Or is opposition better? From the website, looks like that wouldn't come up for some while, though.)

> I have been thinking about how to capture and use asteroid material.
> The capability of spewing out a metal foam sheet or I beam a mile long
> could be of greater use than the same amount of material in compressed
> form: fewer viberational modes, greater cross-section, restricted
> localized damage. Each of the bubbles would be pressurized and would
> therefore have more strength then if made from a honeycomb type
> laminate. Since then I read one article where someone said the problem with many of the people advocating 0-G materials processing (both inside and outside NASA) is that they're experts is space travel, not materials processing. This makes them more attuned to a possible space solution than a possible Earth-based solution which might work equally well and cost much less. Since those early years, I've come to promote other things over 0-G materials processing. I know that even O'Neill (who certainly couldn't be accused of overlooking an advantage to being in space) was fairly dismissive of such then-popular notions as "perfectly round ball bearings" etc. Interesting, I wasn't even thinking about returning the material to earth. I was trying to figure out how zero gravity materials processing would work for a completely robotic operation for materials used in space. I spent several hours in discussion with a combustion expert who sells combustion systems to a variety of manufactures this weekend and in between stories about EPA stupidity we discussed different manufacturing and processing techniques currently in use. The problem with all of the technologies that we discussed was that while they work great for a LARGE earth based industrial plant they would be very difficult to implement in zero gravity. Very large springs would have to be used instead of gravity for force. I was looking for light weight processing systems since most of the parts would initially have to be lifted from earth. It may be many years before enough work is done in zero gravity to discover anything worth returning to earth.
Mitchell James
http://www.innertransit.org

To pick a nit with "It may be many years before enough work is done in zero gravity to discover anything worth returning to earth.", energy(as from Solar Power Satellites) would be worth it now, and the energy crisis would seem to provide some impetus for advocating it now. Sincerely, Jay Huebner

Interesting, I wasn't even thinking about returning the material to earth. I was trying to figure out how zero gravity materials processing would work for a completely robotic operation for materials used in space. Ah, so you were. I was thinking about the eternal search for the "killer app" which will bring about space industrialization. At one time it was hoped this would be products made in space factories and sold on Earth. In the case of space use, I'm sure we'll capitalize on 0-G processing wherever there's even a slight advantage. In such a situation, certain kinds of 0-G processing might even be less expensive than Earth-based alternatives. In other words, in a pre-existing space factory which was built for other purposes, producing foamed steel might well be less expensive than producing an equivalent honeycomb composite. But here on Earth, not so if one must first begin by building the space factory.
Regards,

Some advantages of space for industrial operations are the lack of an oxidizing atmosphere, cheap vacuum,solar energy and low temperatures in the shade (if the heat flow is not too large). Objects in focused sunlight can reach the surface temperature of the Sun, ~ 6000 K, which will melt anything (everything made so far). So one could vapor deposit iron and it would not rust or burn as in Earth's atmosphere. By vapor depositing from multiple sources of different metals onto plastic (or what-ever) forms (which would later be discarded), one could lay down a platinum or chromium rich layer to be covered (and to cover) iron and finish off with another stainless layer. Try that on Earth. One could weld aluminum by holding two pieces together, heating with focused sunlight to melt and then let cool. Again, something you can only do in an inert (usually helium) atmosphere. Fractional distillation using solar energy and the cold of space would be without energy costs. Sincerely, Jay Huebner

"Huebner, Jay" wrote: Some advantages of space for industrial operations are the lack of an oxidizing atmosphere, cheap vacuum, solar energy and low temperatures in the shade (if the heat flow is not too large). Objects in focused sunlight can reach the surface temperature of the Sun, ~ 6000 K, which will melt anything (everything made so far). So one could vapor deposit iron and it would not rust or burn as in Earth's atmosphere. By vapor depositing from multiple sources of different metals onto plastic (or what-ever) forms (which would later be discarded), one could lay down a platinum or chromium rich layer to be covered (and to cover) iron and finish off with another stainless layer. Try that on Earth. One could weld aluminum by holding two pieces together, heating with focused sunlight to melt and then let cool. Again, something you can only do in an inert (usually helium) atmosphere. Fractional distillation using solar energy and the cold of space would be without energy costs. Sincerely, Jay Huebner
Quite possibly but so high level. I can see all sorts of problems with trying to design a factional distillation system in zero gravity using focused sunlight. The major one being containment before during and after vaporization or liquidfication assuming that continous processing is required. I can think of one batch process that would be very wasteful. One big container with lens in its side that is used to vaporize sample which then deposits in layers on walls as walls cool. (have to heat the container before it can cool.)
Can you tell that I think that we should be designing systems instead of just talking about them?
Mitchell James

Hi all!

Justin wrote: Would it be possible to do what Jay suggests if not in zero gravity,
perhaps in low gravity (i.e. the Moon)? Perhaps that would remove your
major issue with his ideas. That is the crux of the problem. If production has to be in a gravity well or a centrifuge well, energy must be used to get the material in and out of the well. There are also size restrictions on material transport whether that is the throat size of a mass driver or the elevator size for a centrifuge. In the High Frontier as well as other lunar / asteroid resource utilization scenarios, there is always a sentence that states that the bulk material is used to create fabulous things in zero gravity. Now NASA has never been interested in actual manufacturing in space. The few experiments that have been performed have been done by ESA. There is much more information on mass drivers than on the system that would actually use the output of a mass driver. I consider not being able to show several realistic designs for a zero gravity material processing system a major problem for any lunar / asteroid resource utilization scheme.
Mitchell James
http://www.innertransit.org (Homebase for web based collaborative engineering)

>
> > Would it be possible to do what Jay suggests if not in zero gravity,
> > perhaps in low gravity (i.e. the Moon)? Perhaps that would remove
> > your
> > major issue with his ideas.
>
> That is the crux of the problem. If production has to be in a gravity
> well or a centrifuge well, energy must be used to get the material in
> and out of the well.

>>>That makes sense, although it seems like the energy to escape the gravity
well of the Moon might still be worthwhile when compared to the energy
required to escape the Earth's gravity well, plus you still gain the
benefit of Jay's atmosphere-less manufacturing ability. I'd have to see
numbers.>>>

A new trend in suspension bridge design is called "cable-stayed".
Cable-stayed designs differ from more traditional, single-cable designs
(visualize the Golden Gate bridge with its meter-wide cable as an example
of a traditional design) in that multiple cables hold up the roadbed, each
cable attached to the mooring tower. One of the advantages of the
cable-stayed design is that, when cables eventually corrode, each one can
be independently replaced. With the traditional design bridges such as
the Golden Gate, the main cable will eventually corrode, and at that point,
it will be extremely difficult to fix the bridge. (Metal under stress
corrodes more quickly than metal not under stress, a phenomenon called
stress corrosion cracking.)

That is the crux of the problem. If production has to be in a gravity well or a centrifuge well, energy must be used to get the material in and out of the well. Perhaps, but I don't think the energy requirements of the latter can even begin to compare to those for the former. There are also size restrictions on material transport whether that is the throat size of a mass driver or the elevator size for a centrifuge. The diameter of the mass driver is sized to make its emplacement a realistic, near-term possibility. And it's important to remember that there's a continuous flow of materials (well, maybe for 2 weeks out of every four). It's a pretty narrow pipeline, granted, but you might be surprised how many tons you could get through it over the course of five years or so. I'm sure there will be many bottlenecks, but I just can't see the elevator size of the centrifuge as being a major one. In later studies, emphasis was placed on systems that could replicate themselves, so we would be talking about a greater number of elevators in a greater number of centrifuges as time went on. In the High Frontier as well as other lunar / asteroid resource utilization scenarios, there is always a sentence that states that the bulk material is used to create fabulous things in zero gravity. Now NASA has never been interested in actual manufacturing in space. The few experiments that have been performed have been done by ESA. There is much more information on mass drivers than on the system that would actually use the output of a mass driver. I consider not being able to show several realistic designs for a zero gravity material processing system a major problem for any lunar / asteroid resource utilization scheme.
That's a good point.

That makes sense, although it seems like the energy to escape the gravity
well of the Moon might still be worthwhile when compared to the energy
required to escape the Earth's gravity well, A fact which means that when we require raw material in HEO, the moon would be a better source for it than the Earth. But this isn't the same as saying that the moon's gravity is so negligible that we might consider doing some manufacturing on the moon because we need some gravity, and the cost of going into and coming out of the moon's gravity well is inconsequential. But if you wanted to avoid gravity wells entirely, would rotational
artifical gravity suffice? Or is that just the stuff of science fiction? Not at all. There's absolutely no reason to think that centrifugal force wouldn't be useful for making materials settle or separate, and every reason to expect that it will be OK for humans (above a certain scale), and will prevent the health problems we see with prolonged exposure to 0-G. O'Neill warned us about our tendency toward planetary chauvinism. I think our tendency to feel that the moon must be better than free space for some industrial operations is yet another example.

>>>The diameter of the mass driver is sized to make its emplacement a
realistic, near-term possibility. And it's important to remember that
there's a continuous flow of materials (well, maybe for 2 weeks out of every
four). It's a pretty narrow pipeline, granted, but you might be surprised
how many tons you could get through it over the course of five years or so.>>>

Can anyone give a rough estimate of the mass of a lunar mass driver? I presume
that SSI must have conducted a great many studies, but I have found it extremely
difficult locating any mass estimates.

Can anyone give a rough estimate of the mass of a lunar mass driver? I presume
that SSI must have conducted a great many studies, but I have found it extremely
difficult locating any mass estimates. I started to citehttp://lifesci3.arc.nasa.gov/SpaceSettlement/75SummerStudy/Design.htmlas a source, but I see that this study assumes a 30 G acceleration of the payload. Working models later achieved 1,800 Gs, and a mass driver operating at this level of acceleration would be much shorter and hence weigh less. Seems like I heard someone say that the components for the mass driver itself could fit into a single Shuttle payload, but that its PV panel power supply would be several times this.

>Can anyone give a rough estimate of the mass of a lunar mass driver?
I presume
>that SSI must have conducted a great many studies, but I have found
it extremely
>difficult locating any mass estimates.
>
> Tony

> There's absolutely no reason to think that centrifugal force
> wouldn't be useful for making materials settle or separate, and every reason
> to expect that it will be OK for humans (above a certain scale), and will
> prevent the health problems we see with prolonged exposure to 0-G.

>
> >Can anyone give a rough estimate of the mass of a lunar mass driver?
> I presume
>
> [...]
> Electrical component total mass 53 tons

>
> >Can anyone give a rough estimate of the mass of a lunar mass driver?
> I presume
>
> [...]
> Electrical component total mass 53 tons
When I last looked at it the worst problem seemed to be for the
energy storage component - capacitors being a common choice,
but to store that much energy for quick release you need a lot of them...
Is that what this "electrical component" mass consisted of here?
Arthur Yes, most of it is capacitors from what I remember reading of the paper. The power switching circuit including capacitors is about all there is anyway. The rest of it is switching controls and sensors.
Mitch

The following recent article on (terrestrially-produced) ceramic foam may
be of interest.
http://www.sciencedaily.com/releases/2001/05/010518082028.htm
When I was looking through the patent listing on metal foam using a chemical reaction to cause gas bubbles to be formed on heating was one of the older known methods. I ignored that type of method because the reactions seemed to use rather esoteric compounds that would require a full chemical industry to create i.e. a lot of chemicals being shipped from Earth to the factory. I am looking for methods that only require a few light weight tools to be shipped from Earth.
Mitchell James
mejames@...
http://www.InnerTransit.org (homebase for collaborative engineering)
http://www.InnerTransit.net (email distribution for distributed multilevel organizations)

>
> > The following recent article on (terrestrially-produced) ceramic
> > foam may
> > be of interest.
> >
> > http://www.sciencedaily.com/releases/2001/05/010518082028.htm
> >
> When I was looking through the patent listing on metal foam using a
> chemical reaction to cause gas bubbles to be formed on heating was one
> of the older known methods. I ignored that type of method because the
> reactions seemed to use rather esoteric compounds that would require a
> full chemical industry to create i.e. a lot of chemicals being shipped
> from Earth to the factory. I am looking for methods that only require
> a few light weight tools to be shipped from Earth.
>