Status: Operational 1967. First Launch: 1967-09-15. Last Launch: 1972-05-25. Number: 24 . Gross mass: 3,000 kg (6,600 lb).
Ground swath was 16 km x 217 km. Also carried a DISIC (Dual Improved Stellar Index) camera, with a focal length of 91 cm, a ground resolution of 30 m, and frame coverage of 260 km x 260 km.
Credit: Manufacturer Image
KH-4B. The launch vehicle had a very cold boattail due to a hose discovered to be leaking away warming air to the boattail. The boattail was colder than usual, below freezing. Based on earlier tests of the Thor for just that condition, as relayed by Ed Dierdorf, Thor chief engineer at the time, the temp low was of no concern.
The only problem was that those tests were made with a Thor that carried a Rocketdyne engine lubricated with "lube oil". The Thor being launched used a fuel additive, "Orinite" (like STP "super snot"). The technician that pumped the Orinite into its cannister later stated, "It wasn't for lack of orinite. I put it in just like the procedure said, and I could feel when it was full (with the hand pump). To make sure, I gave it another slug."
That "other slug" cracked the output valve that was only supposed to be cracked by turbopump output pressure. When it cracked the output valve a bit of the "honey" squirted down the tube toward engine bearing jets. This line had a low spot in it by design. The Orinite settled there. When it was chilled by the low temp air at lox loading, the Orinite formed a plug.
Unaware of this chain of circumstances, Launch Director Philip Payne made the decision to launch. The rocket (carrying Agena D and payload) flew for 18 seconds, then wiped out its gears, causing the turbine to overspeed and shed its vanes. These punctured various parts in the boattail like machine gun bullets. With loss of power, the rocket fell not far from the launch pad into Bear Creek canyon.
The final cause was therefore found to be loss of engine lubrication at startup.