NW054 1/144 Delta M6
The Thor missile program was initiated in December 1954, when
USAF headquarters issued requirement for a tactical missile
intended to travel a distance of between 1 150 and 2 300 miles.
Thor was undertaken as a high-risk program having the goal of
achieving flight within the shortest possible time. The Thor had
its first complete launch pad test in January 1957 and a
full-range flight test in September 1957.
In 1959, the newly formed NASA asked Douglas to create a civilian launch vehicle based on Thor Able. The new rocket was presenting the fourth configuration for the Thor, so it was named Delta - the military code for the fourth letter of the alphabet. The Delta M (introduced in 1968) represented siginificant leap in Delta evolution. With its Long Tank Thor first stage it hardly resembled the original Thor. The long, untapered tanks siginificantly increased propellant capacity. It retained the 2nd stage of Delta E, but it used the TE 364-4 3rd stage, developed from the Surveyor Moon lander's retro-motor.
On March 13, 1971 Delta M6 (562/D83) succesfullly launched the Explorer 43 satellite. Explorer 43 was one of last IMP (Interplanetary Monitoring Platform) program satellites. IMP satellites were designed to observe and measure cosmic radiation, magnetic fields and solar wind in interplanetary space and discovered a region of high-energy radiation beyond the Van Allen Belt.