The heavier ones used to have grommets and can be used as a roof over you. Even the lighter ones can be used as a tarp if you have string and some styrofoam peanuts to push into the tarp before tying the string around them. A space blanket can be a reflector for a fire, but I think of a fire as a nicety rather than something I'd stake my life on building in the wet. In the end all the uses of space blankets fail in a wind, so up against a tree with the sb as a sort of umbrella is the only fairly trustworthy use to me. My rain gear does 99% of what I need then.You cant use a space blanket as a tarp.
Emergencies tend to be more likely with some combination of dark and storm. If I were concerned about where I might be, a one pound sleeping bag, a bivy bag for use over it with a foam pad for use under it, and a real tarp and stakes look like cheap insurance at less than 3 pounds.
Think about the idea of going to sleep on a place like Ruckel Ridge, where you might roll. Those are the sorts of places in the Gorge that might cause the problems that keep you out. You might want to be able to tie in, if you take gear that would let you sleep, or even have your back against a tree for 12 hours.
