Science Fiction Novel by Larry Niven, Jerry Pournelle, and Michael Flynn.
Set in the near future, environmental activists have brought on a new Ice Age by negating the green house effect. The United States has become a place where technology is feared and despised and science is put down in favor of illiteracy and superstition. The only bastions of high technology left are the orbiting space stations Mir and Freedom. But when two astronauts are shot down out over the glacial ice fields of North Dakota, only a persecuted group of underground Science Fiction fans can save them. Angels Down! Fans to the Rescue!