A thin, heat-reflective sheet (aka “space” blanket) is a popular outdoors emergency item, having a number of uses. See adventure.howstuffworks.com/survival/gear/space-blanket and gotimegear.com/blogs/survival-gear/do-cheap-emergency-blankets-work.
If I’m bivy camping – that is, I’m clothed, inside a bag liner, inside a sleeping bag, on top of a sleeping pad, and inside a bivy sack – what then is the optimum location for a shiny survival blanket, for the purpose of keeping me the warmest? Assume two possible sizing situations:
- A narrow, or single-width, sheet that I can lie over or under (not both).
- A wide, or double-width, sheet that I can fold over so I can lie inside.
Ideally, you have tested, or know of tests involving, multiple orientations.
← 9 Bivy sack → _____________________ / \ ← 8 Sleep bag → | x x x x x x x x x | | x x | ← 7 Bag liner → | x _________ x | | x ( ) x | ← 6 | x ( Clothed ) x | | x ( Body ) x | | x ( ) x | ← 5 Bag liner → | x (_______) x | | x x | ← 4 Sleep bag → | x x x x x x x x x | | | ← 3 Sleep pad → | ===================== | | | ← 2 Bivy sack → \_____________________/ ← 1 The ground ~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you understand the above schematic cross-section, then you can see that
- sizing situation one has nine possible orientations, numbered 1 through 9, and
- sizing situation two has five possible orientations: 1-9, 2-8, 3-8, 4-7, 5-6