This new “multi-blog” site allows me to write posts for different topics in any order, keeping them all well organized by blog topic. So, don’t be surprised to see articles about other topics sprinkled in with those of my primary “Lost Lord Keeper” research blog.

This is the first article in my “Practical Ingenuity” Blog, and lays out the often misunderstood (and extremely practical) science needed in the challenge facing many citizens of Ukraine this winter: how to be fine spending the night “in a freezer”. This article lays the groundwork for my next article about the “Rocky Mountain Survival Bags” we have built and sent to Ukraine. The strategies implemented by this survival bag makes your existing bedding far more effective. This is something you can improvise yourself with an off-the-shelf “solar tarp”, extreme weather duct tape, and some critical science.

This discussion of applied thermodynamics and aspects of classical quantum theory provides an intuitive understanding of what heat really is, how it moves….and provides critical insights on how to manage it.

The Origins of the Rocky Mountain Survival Bag

For many years, I worked at Lockheed’s Space Systems division. There, I had the opportunity to see what’s inside the thermal blankets that enclosed the spacecraft’s electronic boxes. And I was surprised. There were no thick layers of cloth or foam. Instead, these “blankets” were a rugged outer fabric shell around a number of thin, alternating layers of gold-faced mylar and fish-netting nylon. I was intrigued. Why was this the right solution for managing heat in the extreme hot and cold of space? When I asked about it, the answers I got were helpful, but not fully satisfying. It reinforced that heat in space moves as light because there is no other way for it to cross a void. But there were unexplained disconnects with what I had learned about atomic-level energy transfer in my coursework in university chemistry. Those nagging, unresolved questions found their way to a back burner in my mind, but never went away.

I’m not formally trained in thermodynamics. But my well-loved university cousework in chemistry, physics and optical systems was telling me there was an important insight just out of reach. After more than a decade of running a thought experiment in my head, I came to a rather shocking realization (one that was later confirmed by a colleague with with a PhD in Astrophysics). It is this: something like 95% of all heat transfer is directly or indirectly driven by photons of infrared (IR) light. As you will see, this insight can be imminently useful.

Have you ever noticed that that it feels nearly as hot under some sunshades as it does in the open sun? Or that some coolers keep ice far better than others? Did you know that clear plexiglass will make you invisible to a thermal imaging camera? Or that those same cameras can see through a heavy black plastic contractor bag as though it wasn’t even there? It turns out different materials respond differently to light in different wavelengths. Sometimes dramatically so.

Understanding what I’ve learned about heat and IR light has allowed Mary and I to carry a half-pound solar tarp to the bottom of the Grand Canyon where we sat quite comfortably in temperatures exceeding 100 degrees F. Later, we put these insights to a dramatic test in an attempt to create a compact, lightweight winter storm shelter for our snowshoeing excursions in Colorado’s Rocky Mountains.

Our First Winter Shelter

We designed a test to see if our own body heat could be captured well enough for us to survive sub-freezing conditions in a lightweight emergency shelter we had thought up. Planning a late October excursion, we decided to spend a night in freezing conditions alongside the Arkansas River at 9,000 feet. When we arrived, we wrapped a tissue-thin summer backpacking tent in a fully enclosing single layer of reflective tarps (including one underneath). The shiny side of these tarps faced in to reflect any escaping heat in the form of IR light back on us. We fastened the tent’s rain fly over the tarps to hold them in place, and to keep the wind from disturbing them. But there was no insulation at all, and no other source of heat.

With a nearby hotel to retreat to in case our experiment failed, we settled in for an evening next to the campfire–with a solar tarp behind us to reflect firelight onto our backs (which worked!). But later, as the wind picked up and the evening went from chilly to cold, it was time to retreat to our shelter.

Inside, it was pitch dark (since the tarps blocked all outside light). We settled in to play cards by headlamps wearing light jackets in the pocket of shiny space we had created. Fortunately, the tent’s thin rain fly did a good job of holding the solar tarps in place as the wind picked up.

As it became cooler inside the shelter, we chatted nervously while climbing into our moderate quality “zip-together” sleeping bags. Zipped together, these form a single, “double wide” sleeping bag and allowing us to to share body heat. Just outside, the wind jostled our shelter. A light snow fell in the night while the temperature dropped to nearly 10 degrees below freezing. But inside, we slept snugly through the night. We had created an emergency 2-person winter shelter that worked. By carrying only three lightweight tarps more than we usually carry, we had an effective emergency shelter that is easily packed and can be set up nearly anywhere.

Thinking about the distress facing the besieged people of Ukrainians this coming winter (given Russia’s cruel attacks on their energy systems), we created the “Rocky Mountain Survival Bag” from one of those same solar tarps. With the help of friends and neighbors, we built 50 of them and shipped them to Ukraine Action–a UK aid group that has agreed to put them in the hands of folks in Ukraine who need them.

The Science Behind the Survival Bag

The challenge can be likened to helping someone with normal bedding survive (and ideally, sleep comfortably) through the night in a commercial freezer. Wintertime temperatures in Ukraine can be expected to frequently fall as cold as -10 degrees F. This is possible, but requires more than a casual understanding of the nature of thermal energy transfer (and how to contain it). In this case, there are three dominant categories of heat transfer:

1) Radiation. Specifically, this is the transfer of energy by photons of light in the near-infrared band (just below our visible light spectrum). This is what we experience as heat in sunlight (or what your chicken nuggets experience while basking under a heat lamp). In this form, heat will cross immense distances of free space at the speed of light unless it strikes something along the way (like the Earth). It turns out that half of all the sun’s total outbound energy is delivered in this band. As you can see in the image below of sunlight that reaches the Earth’s surface, the peak energy happens in the blue part of the visible light spectrum, but more total energy is delivered in the “near” region of the adjacent infrared band.

But its not just the sun radiating IR energy around us. Anything warm (like humans) also radiates part of its captured heat away as infrared light. When you look at those strange “glowing” images from thermal cameras, you are seeing what humans look like as they radiate this light away in the (non-visible) IR spectrum. In this band of light, the human body is a gigantic glow-stick! Good to know.

2) Conduction. This is the energy of those same IR photons temporarily trapped in the bonds between atoms in molecules of matter. Heat in this form spreads through those materials and also passes between materials that are in physical contact. In the world of classical quantum physics, this trapped energy is what makes atoms “vibrate” (or jostle) when matter is heated. And (as previously mentioned) such heated matter (like our bodies) also “re-radiates” part of its heat as new IR photons.

3) Convection. When atoms are vibrating with induced heat energy, the molecules they are part of physically “swell up” somewhat. If all the molecules across a structure are swollen, we can observe the effect at our (macro) level. Running the stuck lid of a jar under hot water causes the lid to swell, making it easier to separate it from the jar. Similarly, a heat-swollen roadway buckles and cracks on harsh sunny days. But since the mass of those swollen molecules has not changed–they are simply less dense.

If such swollen molecules are not part of a rigid physical structure (i.e. if they are part of a fluid, like liquid or gas) these less dense molecules will start physically migrating (rising) upward, away from gravity. As these molecules rise away, they carry their captured heat away with them. This carrying away of heat is thermal energy transfer by “convection”.

In a pot of water being heated from below, cyclical convective currents form as upward streams of hot water molecules rise while downward streams of cooler molecules descend to take their place. Although irrelevant in space, this mode of heat loss is important down here at the bottom of the atmosphere.

Take a Ridealong with Heat Energy in Motion

I created the following images to follow the energy of a single IR photon was it is passed along by these 3 modes. This is nothing less than a short course in classical quantum physics. But no need to buckle up–its not all that hard once you have a good way to think of it. And understanding this will help you understand how the battle of managing heat loss can be won.

Above, 5 atoms of water are shown in a molecule of water “at rest”. As is commonly known, the atomic form of water is H20–one hydrogen atom (shown in red) bound with two atoms of oxygen (shown in white). Imagine this molecule as part of a cell in your skin on a sunny day. Notice that the atoms of water are bound to other atoms of water by blue dashed lines. These represent the molecular bonds (think flexible electrostatic “bungee cords”) that hold the larger “clusters” of water molecules together.

Figure (1) shows the arrival of that all-important photon of IR light. One thing to keep in mind is that in quantum physics, the energy of such a reaction is constant. One incoming “cup” of IR energy in will ultimately result in the same quantum (i.e. specific “quantity”) “cup” of energy released.

As a minor aside, higher energy photons (especially of UV light) can actually be absorbed directly by an atom itself, boosting electrons from lower-energy orbits up to higher energy orbits around the atom. UV photons of even greater energy can actually cause the breakdown of the bonds between atoms in a molecule. Such molecular breakdown is what is happening at the atomic level when we observe materials falling apart after long exposure in direct sunlight. Lower energy IR photons cannot change the physical state of atoms–they can only cause “vibrations” within them–or eventually cause the breaking up clumps of such molecules (as when water boils).

In figure (2), the photon has just been absorbed by our clump of water molecules. This newly absorbed energy is now “kinetic” and starts gently knocking things around. The molecules of water are physically jostled or twisted by the change in energy of the molecular bonds holding them together. But because this jostling is electromagnetic (like trying to push similar poles of two magnets together), there is no friction–no energy is lost in this jostling. The bond holding this bit of energy acts like a tiny battery, storing it for a moment before it finds somewhere nearby to slip off to. When it does, that movement of heat energy across the structure of adjacent molecules is called heat transfer by “conduction”.

But this migration of energy across a molecule can only take place if there are nearby bonds available that can accept that exact quantum “cup” of energy. The randomly jumping energy goes where it can…tending to flow from heat congested areas to cooler areas where there are more energy “vacancies”. This quantum opportunity for absorbing energy is true of the initial arrival of the IR photon as well. If there is “no room in the inn” (as the photon arrives), it will simply pass through without being absorbed.

By the way, water holds heat very well because it is dense (i.e. has many atoms in a small space) and has many available bond “vacancies” suitable for accepting quantum “cups” of IR-level energy.

As mentioned previously, conduction tends to spread heat energy from warmer parts of a material to cooler parts of it. So, in relation to a person’s warm body in a cold room, this means conduction will always tend to move heat away from you as it attempts to heat the cold room around you. This is not helpful if you are trying to stay warm.

This brings us to a key insight: the goal of insulation is to impede this outward (conductive) heat flow as much as possible. In a thick blanket, this is done by trapping heat as much as possible in tiny pockets of immobilized air within the fabric structure. The heat will still try to move, but it takes more time to conduct through the fabric, and the heat that winds up captured in immobilized bits of air can’t easily convect away. The thicker the insulation, the longer heat takes to make its way through. This delay heats the near side of the blanket and allows the body the time it needs to replenish any lost heat.

Figure (4) is where things really get fun! All the while our quantum of heat energy is making its way across molecules, there is a probability that it will at any moment be released away as a new photon of IR light.

The next critical insight is that the direction of this new IR photon is random–it is completely independent of which direction our initial photon arrived from. Unlike conduction’s steady march outward, this new photon could fly away from its host molecule in any direction.

Think about the implication of that for a moment. In means that any radiated photons from within your blanket are as likely to move heat towards you as they are to move it away from you. Even better, if you have surrounded that blanket with a reflective surface, any photons with an outbound trajectory will be largely reflected back towards you. If that didn’t give you an “aha!” moment, you may want to go back and read these two paragraphs again.

While we are in the neighborhood, lets pay a quick visit to the topic of boiling water. As you continue to apply energy to the water, the quantums of energy being captured by a given molecule begins to fill up all the vacancies at “the inn”. Ultimately, the the kinetic jostling of the atoms becomes so intense it exceeds the strength of the bonds holding the molecules together. Atoms of water begin breaking free of the liquid’s molecular structure, becoming highly energetic free molecules of water vapor. Down at the bottom of your kettle, these free molecules of water vapor coalesce into bubbles that rise (by convection, of course) to the top of the water. Here, those bubbles pop–releasing the water vapor we know as “steam” into the room.

The useful takeaway of this last bit is that (except for some limited cases, like a pressure cooker) water cannot be heated to a temperature beyond its boiling point. Apply all the heat you like, the water (that hasn’t boiled away yet) remains at 212 degrees F. From a safety perspective, although you can still be burned by water at a boil, the burns from a material that can be heated well beyond this temperature (like iron) could be far worse. We will get back to this later, when we discuss adding heat sources to your bedding.

Now, Let’s Take It Up a Level

Now that we understand what heat really is and how it is dissipated, lets talk about how to keep a sleeping human comfortable while spending the night in a commercial freezer. The next figure shows heat dissipation into a cold room for a human with exposed skin.

Some body heat is lost as radiated IR photons, while more is conducted into the molecules of air next to the skin. Although air is technically a good insulator, these newly heated molecules next to the skin begin a “conveyor belt” of convection. Warm air molecules rise, and are constantly replaced by new cold molecules of air from the room. If a breeze is present, this process happens on fast-forward (as all air molecules near the skin are swept away to be replaced by new cold air molecules).

In this case, essentially all heat lost from the skin is truly lost, and the person’s body will rapidly expend all the heat it can generate in an ultimately fatal attempt to heat the room.

The first improvement is to place the human in comfortable nightwear, covering much of their skin with a thin bit of fabric. This is more effective than you might expect, given the flimsiness of the material. But that flimsy material does create a thin, loosely trapped layer of air next to the skin (this is the same thing a layer of fur does for animals). To the extent this air cannot easily convect away, the heated air’s ability to accept more energy is limited, and it will even return part of its energy back to the human. So, our human can now sleep comfortably in a cool room. In a freezer though, our human will only survive a bit longer.

The next improvement is an obvious one: give the human a blanket to wrap up in. This makes a significant difference. As you can see in the image below, we have now created alternating layers of air and fabric between bare skin and the cold room. In fact ,the blanket itself behaves as a thick zone of trapped air amidst the forest of threads in its fabric. As we discussed, these tiny, trapped pockets of air are a good insulator, slowing down conduction and preventing convection from carrying away heat except that which has made its way to the outer layer of the blanket. Also, the forest of fibers is much more likely to intercept any outbound IR photons escaping from the layers below.

The situation for our human is now much improved. With an effective blanket, they are now able to sleep comfortably in a “chilly” room, and can even survive the night in a moderately cold one.

Adding a second blanket also makes a big improvement. Although there are some other challenges to overcome, adding enough blankets would eventually allow our human to survive the night in a freezer. However, note that a temperature gradient is forming across these layers–getting colder as we move outward through the layers from the skin towards the open room. This means that successive blankets don’t have quite as much impact as the ones below.

Here’s where the survival bag comes in. As you can see in the image below, this bag does two important things: First, it is able to reflect about 80% of the escaping IR photons that reach it, sending them back into play in the layers below. Second, it provides another air layer and isolates all the air within the bag from the cold room.

To the extent this bag is closed off from the room, convection of warm air seeping out from the layers below will be blocked. There will still be convection within the bag, but this will only result in skightly warmer air accumulating in the upper part of the bag and radiating part of its heat down on the layers below.

In the end, conduction will still carry some heat from warm air molecules through the material of the survival bag and into the room. Also, as much as 20% of the IR photons reaching the inner surface of the bag will make their way into the room (better reflective materials can reduce this as low as 10%). But the bottom line is that much of the human’s body heat will remain trapped in the layers within the bag.

Down to temperatures moderately far below freezing, this limited level of heat loss can be sustained. Humans are biological heaters after all. But as temperatures fall further, it will be necessary to introduce additional heat sources within the bag for the human to remain comfortable (more on this later).

In the next article, we will discuss how to use the Rocky Mountain Survival Bag effectively, and some strategies for handling more extreme environments.