XIT of satisfactory cloud samples during an in-cloud flight time of about one hour between H+2 and H+6 hours after burst, IE stated in this letter that we required at least six samples on the assumption that each such aircraft would furnish one sample "22 He also discussed the eight B-57B aircraft under procurement, It would not operate at an altitude of 60,000 feet, and could only under the most exceptional conditions, and then only for a few minutes, reach 54,000 feet. However, Dr. Grave's letter gave Air Force Special Weapons Center officials a strong argument for B-57D aircraft instead of the "B® models they had been waiting fors here was an airplane which promised satisfactory performance, But getting the B-57D aircraft approved as a cloud sampling aircraft required as much time and as much paperwork and persuasion as the original B-57, Following the letter to Major General Stranathan, Harold F, Plank of Los Alamos Scientific Laboratory wrote his co-worker, Dr. R..W. Spence, "Since, so far as SWC can now determine, this replacement would involve the procurement of eight additional aircraft at additional expense to the government over the presently planned aircraft inventory, Los Alamos Scientific Laboratory cannot lend its support at this time to any action which the Special Weapons Center may take to plan for the proposed replacenent,®And he added: ", , . it might be desirable for us to decide at this time to establish a requirement with Special Weapons Center for two or three B-57D aircraft on a loan basis to be used if a large yield _weapon test does take place after REDWING, such a requirement would enable Special Weapons Center to explore with Aircraft Allocations the possibility 2h7 AFWL/HO SWEH-2-003), & e Up?