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Void

Member

Registered: 2011-12-29

Posts: 7,082

"Chevron Shielding", borrowed from space habitat , adapted to Mars.

I remembered something from the book I read from the 70's, about the O'Neill cylinder design for windows.  A radiation shield.
A illustration of it can be had in this link:
http://www.quadibloc.com/science/spaint.htm
You can find this diagram in that article with some text related:
https://www.bing.com/images/search?view … ajaxhist=0

Here is some associated text, but there is more to read about it in that link:
In the space colony designs in which an impressive vista of space is provided through large clear windows, it has been noted that radiation shielding could be added by the use of "chevron shielding", in which reflecting V-shaped metal troughs are embedded in the glass so that the light travels along a path like that in a pair of periscopes, and radiation is attenuated because any straight-line path to space must go through the metal.

One difficulty with chevron shielding is that there are so many places where glass must be bonded to metal; this would seem to invite the leakage of air, as well as limitations in structural strength. The alternative of embedding the edges of the metal chevrons only in one side of an expanse of glass creates potential stress points from which fractures may start: the vulnerability of glass, once scratched, is well known. Plastic, made from cometary material, might be considered, but in an early space habitat, quartz is a common material, while hydrocarbons, being more difficult to obtain, would likely be used primarily for biomass; while a layer of flexible plastic a fraction of an inch thick might serve for some purposes, a rigid window of plastic several inches thick, providing structural strength under compression as well as tension would seem unrealistic.

Historically, I have more favored artificial lighting for greenhouses, but I think we might adapt this to Mars, in various ways.
Of course you could have a horizontal window with chevron structure, but I would more think to begin with a vertical array, at least in the first thinking.

Although it would not be impossible to think of directly associating an air pressure retaining glaze, either on the outside or the inside, I for now tend to think of building this structure independent as a sort of an arch-dome somewhat resembling a Quonset hut, but of course a pointed arch, not with a rounded top like a Quonset hut.  Like a Quonset hut, I expect this to be a linear structure, not a circular dome.

To finish the ends I would try a vertical block wall on each end, and then put a berm of regolith against the wall on the outside.  Also on the ends could be entrances, but it may also be possible for the entrances to be in the form of connecting tunnels attaching to the interior from below.

The building materials tried might be various.  Compressed, glued blocks of regolith.  The glue might be a plastic like material, or concrete cement.  The blocks stacked up on each other might also be glued to each other during construction.

If it is desired, light could come in through both chevron sides.  In the case of a side being in shadow, simple reflectors on the ground, perhaps resembling aluminum foil could bounce light into the shadowed side.

And so in this less developed version, it would simply be a shed, and light would enter it relatively unfiltered.  Such a shed might be useful as a robot housing, or for rover protection.

In order to filter the light, then perhaps a reflective coating on the chevrons, and an overlay of some U.V. blocking method.  This perhaps could be liquid glass sprayed on.

Handling Martian dust will be a problem.  There are methods to reduce the attraction of dust to the surfaces.  Also robot dusters could be employed to deal with it.  Or a U.V. tolerant "Glaze" could be used to prohibit entrance of dust to the surfaces.  I favor avoiding the exterior glaze and using other dust handling methods.

Although there could be many methods of installing a air pressure retaining bladder inside of the device, I currently favor, a wire mesh with a bladder of plastic web, transparent or translucent enough to allow photo life to grow.

The lowest air pressure to use might involve having a ice covered pool in the bottom, with the necessary moisture retaining plastic window.
In that case only a few millibars above ambient could be used.  However this method will only be suitable for low temperature aquatic plants, or sub containments (Jars) installed below the ice, and in the water column.

The next case would be a bladder with no ice, needing a somewhat higher pressure, where spray nozzles would spray the interior of the bladder with nutrients, and an "Algae or Cyanobacteria would grow.  I guess their would need to be a "Harvester" robot inside to gently scrape the algae mats off as they accumulated.

A next case would be where you had an open pool, and significantly higher pressure, and would attempt to grow some floating plant such as duck weed.

Other cases of aquiculture could be attempted.  It is the nature of aquiculture, that the body of water will help to buffer the temperature extremes of day and night.

But then deviating from aquiculture to "Moist soil" farming, probably higher pressures needed.  At least 70 mb, but if possible 250-330 mb.

The intentions are that the chevron structure would filter light, buffer thermal variance (Using it's thermal mass), and yet make it possible to perhaps compensate for the lower natural light levels of Mars, and the expected attenuation which will occur with 4 bounces off of chevron reflectance, and passing through the bladder glaze.  I am hoping that the U.V. can be attenuated much more than useful light.  As I said a U.V. protective liquid glass spray is a good place to start.  It may also be possible to coat the bladder's outside with that as well.

Dust control will be important, as it may coat the surfaces and reflect U.V. light in.

I am hoping that will good attenuation of U.V. light, common types of plastic film which do not tolerate U.V. very well can be used.

Other radiation concerns:

The chevron will reduce radiation in the interior just by bulk mass.  But perhaps magnetic fields can be created around the device to help with that.  It is suggested for spacecraft, so why not on the surface of Mars.  This would make these places more habitable for humans.

That is all I have for now.

Done

Last edited by Void (2019-05-12 09:18:50)

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Done.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 28,838

Re: "Chevron Shielding", borrowed from space habitat , adapted to Mars.

Chevron is a pattern of interlacing V shaped interlocking. Such as building with bricks in this case made of lead.
https://marshield.com/lead-bricks/?cn-reloaded=1
Radiation shielding is a great necessity in medical offices where X-rays are taken and other nuclear medicine is regularly practiced.
https://www.roystonlead.com/products-ca … on-bricks/
The chevron can also be built into a concrete block as well for shielding both neutron and gamma radiation in a variety of environments.
http://marshield.com/wp-content/uploads … ncrete.pdf

I will read your post tomorrow on a better computer if I have time

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 28,838

Re: "Chevron Shielding", borrowed from space habitat , adapted to Mars.

On the first link it is an under ground chamber that is using a light tunnel, reflection system to direct the light towards the habitat area at the bottom. Tunnel reflective walls make it possible to get the light down the tunnel to the habitat. The habitat area at the bottom is further magnetically isolated in the walls for any other forms of radiation that might persist. It appears that the top is a layer of ground supported above a glass area or protective dome just under that to make it possible to shield the habitat from direct radiation exposure. Not shown would be the support collumns for this roof.

I would think that the deep location at the end of the tunnel would be sufficient to take care of the radiation that would penetrate the ground making the secondary magneticv bottle over kill but test an measurements are needed to say for sure that its not needed in the habitats design.

The design is straight forward in that what you need must get into place once the chamber is created and sealed. Sort of like building a ship in a bottle.

The disk shape is more of a space rotating station in design with self support via the greenhouse recieving reflected light. Its this one that is using lead glass in a chevron pattern to keep the radiation exposure low.

Void

Member

Registered: 2011-12-29

Posts: 7,082

Re: "Chevron Shielding", borrowed from space habitat , adapted to Mars.

SpaceNut.  Thank You sincerely.  You should be blessed for your work.  I only included the link as I do not intend to use other peoples chevron diagrams without giving attribution.  You looked it though, and found so much that I like.  I am probably ADD, even though I was never diagnosed for it.  If something interests me I will be much more likely to give it attention.  So now I am more entertained.

If you and the members will consider a review of what I now say, then I will be pleased.  I think that for Mars, rather than a overhead shielding wall, a vertical one might do.  And onto that mount your mirror with manipulating motors.  And for the light shaft, make it at a diagonal angle.  This way, indeed very much of the GCR will be blocked, by the wall and the walls of the light tunnel.  And the wall will be a fixing point for the mirror Heliostat(s).   I believe that many plants will do just fine with 10% of Earth sunshine.  But it should be possible to do better than that.

So if in the northern mid latitudes of Mars, the wall to the North of the tunnel.  And of course if in the southern mid latitudes the wall to the south of the tunnel.

I agree that with the Martian atmosphere, and these structural impediments for radiation, it may not need magnetic shielding.

It would actually be very nice to have a little greenhouse courtyard at the bottom of the light tunnel, and then other rooms for living space can be behind a wall which would serve as further shielding.  Windows then in your kitchen, bedroom(s), living room, ect.  perhaps a window facing the garden for each room.  Yes the window might let a bit of harmful radiation in, but I bet it will be very minor in quantity.

The chevrons if used, could go in various places.  For instance in addition to the use you have mentioned, perhaps you would have shutter chevron doors on the windows I previously mentioned.  To let light in, and also provide privacy when desired.  Otherwise open the doors on the windows to allow a view of the garden.  And the chevrons on the windows as well could provide additional radiation protection.

Do you think I am approximately true to the reality of this type of thing(s)?

…..

I have to thank you for your persistence again, as I now am aware of this:
https://en.wikipedia.org/wiki/Dandridge … Cole#Books

A book "Islands in Space: The Challenge of the Planetoids, (1964 with Donald W. Cox)".  I borrowed it from a library when I was perhaps about in my low teens.  Someone had scribbled "Planetoid Quackery" on it.  So many space haters.

Still I read it.  And of course later O'Neill's work.

So, I guess I have been into space for that long.

Done.

Last edited by Void (2019-05-13 18:29:47)

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Done.