Three longish sf stories of pleasant straightforwardness and good nature. The title story sets the pilot of a supersonic armed--with nukes, of course--reconnaissance jet amid the seat-of-the-pants heroism of a WW I French airfield--where his 89-foot-long VTOL Mach n miracle is suddenly all but useless against the battered biplanes of the Hun. ""The Permanent Implosion"" pits a profit-minded Texas blasting-company engineer against a ""congruency"" which has suddenly united Gunbarrel Hill near Boulder with an interstellar vacuum that is violently sucking out the earth's atmosphere. ""The Brotherhood of Keepers"" puts a race of furry blobs in the process of developing intelligence at the mercy of a pompous SPCA type, a devious experimenter, and a stymied research coordinator. Unobtrusive writing, gracefully suggested characterizations, nicely chosen ideas.