EcoRenovator - Space Suit = Multi-Layer Insulation (MLI)

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- - Space Suit = Multi-Layer Insulation (MLI) (https://ecorenovator.org/forum/showthread.php?t=3812)

Quote:

Originally Posted by Drake (Post 41131)

Not all Pellon is heat fusible. Maybe it is not actually Pellon but looks like it, I use it in my art ceramics work all the time because it has a very smooth surface a stiffness that resists wrinkling and breathes(so it is not a tight woven fabric, more a kind finery felt). No it does not provide any real "loft" just overall "thinness" of bridal vail if that is what is being sought.

OK, the mylar is doing a great job of reflecting heat, it also does a good job of not conducting heat because it is extremely thin.

So, the ideal separation material would be thin, but still provide a space between the layers of mylar, and it would have zero potential for conduction.

I am thinking along the lines of a 'thinsulate-ish' material because it is composed of microfibers, and conduction would be directly proportional to the area of the material, and the area of a single strand of microfiber is extremely small, so many strands of microfiber would conduct less heat than a similar material made up of larger diameter elements.

-AC

Came across this thread while looking to use MLI on mid-altitude balloon flights for battery thermal management for my business. What Exeric cautioned about is indeed the case. At low altitudes (<10,000ft), MLI does a horrible job of insulating due to most of the heat flow being dominated by conduction and convection. A 10-layer MLI was so bad we never even flew it for a mid-altitude (~10,000-60,000ft) as the batteries would already be too cold by that point. In short, 1/2" of XPS worked far better in our test with a temp difference of ~60°C and a surface area of ~10sq in. For high-latitude to space-like environments its a great solution. Unfortunately, as Exeric pointed out, anything other than a vacuum between layers greatly degrades this type of insulation. There is a reason it is often recommended to have ~3/4" air gaps with radiant barriers on houses (since most are build with atmospheres around them) instead of MLI's 20-60mil gaps.

We're toying with the idea of a mixed system where a thinner MLI blanket surrounds the batteries and is housed in an XPS external box, but its not a high priority as it adds weight. This is different than layering the insulation in the gaps which would render MLI useless as a radiative barrier.

Quote:

Originally Posted by Exeric (Post 40232)

insulating materials invariably have a higher emmisivity than a vacuum. So installing insulation between layers is not a solution. It's the touching of molecules to a radiant barrier that conducts (conductivity?) heat away. Of course, some molecules conduct heat better than others, but there isn't any molecules that conduct heat less than no molecules.

Thanks for the feedback.

I don't know if I mentioned it previously in the thread, but I did some informal testing of a 10-layer MLI sample, which used actual bridal veil as a spacer.

I used it as a pot holder... not with temps so high as to melt the mylar or veil material. It was a remarkably effective insulator, especially considering how thin the MLI sample was.

My current thinking is that MLI would make really great thermal window shades, since they are flexible, and are good at turning back radiant energy.

Did you seal the edges of your MLI material?

-AC