Operation CASTLE's sampling program resulted in the decision to ask for B-57 jet bombers as permanent sampling vehicles, Following the operation, General Estes recommended that the B-57 aircraft be used on all future sampling missions, He believed the aircraft would require a removable bomb bay fuel tank for additional range, reserve oil capability to take care of the rate of use of oil, "featherweighting" to increase the maximum altitude, and, finally, devices for collecting particulate and gas gamples. Nine B-57B aircraft could replace fifteen F-8) aircraft, two B-36H samplers and one RB-36H sampler control aircraft, In addition, the nine B-S7 aircraft could bring back’ better samples than could all these aircraft and would, of course, be mich less expensive to operate, "Each aircraft would have a ‘sampler director! aboard thus eliminating the need for a control aircraft." When more powerful engines were available, the B-57 aircraft would meet ", , . all future requirements in both continental and overseas tests in an effective, economical manner without the loan of aircraft from other USAF agencies," General Estes *39 concluded, + . Central coordination of the efforts of the sampling aircraft is still necessary and a control plane has continued to be used with B-57 operations with a seientific director in the back seat. A B-57 is used, however, and can sample last as a back up in case of aborts. An exception to this took place during one of the ROVER sampling operations when the entire sampling runs were easily observed from the control trailer in the forward area, This was done because of the attempt to employ KDB-l drones and control them from the ground, On this occasion the B-57 operations proceeded smoothly from the ground control, but this was a highly special case, 117 lene SWEH-2-003), io"