Richard Feynman handwritten document, written in 1986 by Feynman during the investigation into the Space Shuttle Challenger disaster. Feynman titles the document ''Back to the joint'', making numerous notes referencing the o-ring joints that failed during the launch. In addition to drawing several diagrams of the joints, Feynman writes in part, ''1 joint .17'' erosion over 1.6'' & secondary showed erosion 3.1''...How are models made?...larger O-rings-higher pressure seal...'' On the back he writes in part, ''Report Aug 1985 / Model Calc. / Model tests / Did they test seals under cold & stress...'' This last question is the very heart of the disaster, as the O-rings showed themselves to fail at very cold temperatures. At the top of the first page, Feynman writes several names next to machine parts, with ''Mike Weeks'' next to ''O-RINGS''. Weeks was deputy associate administrator (technical) for space flight at NASA, who deeply regretted he didn't stop the launch. Single page measures 8.375'' x 10.875''. Near fine condition. From the estate of Richard Feynman.