Just before dawn, “Fearless Felix” will don a custom-made spacesuit and ascend high over the New Mexico desert in a capsule suspended beneath an immense helium balloon, then fall to earth from 120,000 feet. The Austrian adventurer hopes to break an unofficial record Col. Joe Kittinger set with a leap from 102,800 feet in 1960, and expand our understanding of what happens during a free fall from extreme altitude. Such lessons could be valuable as commercial space flight takes off.