Unique handwritten note by John Young on a Manned Spacecraft Center Astronaut Office routing slip, one page, 5.25 x 8, January 16, 1974. The slip is stapled to a mimeographed memo on the subject of "8 psi EV Suit Development," in part: "It came to our attention that the EV suit development program being conducted by the Crew Systems Division with RTOP funds has been redirected toward a 4 psi capability, rather than 8 psi, as we have understood. As you are aware, this change to 4 psi necessitates a prebreathing requirement and therefore has a significant impact on Shuttle planning. While we want to avoid high cost or high risk development programs, we are not aware of the technical rationale supporting this change, nor have we received a Research Change Notification to the RTOP informing us of a decision to pursue a 4 psi suit for Shuttle." On this page Young underlines a few lines and asks of RTOP: "Whose $ is that?"
On the attached routing slip, Young writes, in full: "Probably—it is so hard to wiggle one's fingers at 8 psi. They don't want to bother. Will we have a non wiggle 8 psi suit so we don't have to pre-breathe? Or will we have an 8 psi suit that wiggles: 'the high cost & high risk development' that can't be avoided?" The slip has further been initialed by seven astronauts: John Young, Alan Shepard, Charlie Duke, Ken Mattingly, Bruce McCandless, Stuart Roosa, and Rusty Schweickart. In fine condition. Accompanied by a full letter of authenticity from Zarelli Space Authentication.
Ultimately, the operating pressure of the Space Shuttle's Extravehicular Mobility Unit (EMU) space suit—introduced in 1981—was 4.3 psi. To perform an EVA from the Shuttle, the cabin pressure was reduced from 14.7 to 10.2 psi for 24 hours, after which an astronaut had to pre-breathe for 45 minutes.
