In 1964 Nasa developed a thin ( @ .20 Micron) plastic sheeting coated with powdered aluminum. We don't know if it was the same team that developed the Magnesium bar. The first use was in space suits with @ 27 layers.The material will reflect 80-90% ( depending on the source) of radiant body heat. Remember, these suits had external heating units in a closed and regulated environment. The 'Space Blanket' entered the civilian market as a lightwieght emergency item in an open and very unregulated environment called Mother Nature. It's that very compactness and wieght that make it an attractive option. But is it a blanket? A 6 point Hudson's Bay blanket is THICK. It has lots of air pockets ( loft)in all that wool to hold warm air.A single unit of space 'blanket' has none. Coupled with the fragile, almost single use material, space blankets are more properly space sheets. They make a good outer barrier to ward off wind and rain, or would if designed as an enclosed unit ( what Blizzard bags and a few others have done.)They have found some favour as PART of improvised shelters to improve campfire efficiency. The danger lies in their promotion as a convenient placebo. A person not interested in personal safety is going to think this handy, $3 item in the glove compartment is a Hudson's Bay Blanket. There's a anecdote about a cowboy caught in a Blizzard in the 1880s with only his thin 'fish' rain slicker for protection. He barely rode back to his ranch. His bunkmates asked him if the fish helped any? " If I had two of the blankety-blank things on I would have freezed to death." Is there a valid role and place for this material? We will try to find out with testing.