Launch of first Delta M, withIntelsat III F-1 | |
| Function | Expendable launch system |
|---|---|
| Country of origin | United States |
| Launch history | |
| Status | Retired |
| Launch sites | Cape Canaveral,LC-17A |
| Total launches | 13 |
| Success(es) | 11 |
| Failure | 2 |
| First flight | 18 September 1968 |
| Last flight | 17 March 1971 |
TheDelta M orThor-Delta M was an Americanexpendable launch system used for thirteenorbital launches between 1968 and 1971. It was a member of theDelta family of rockets.
The Delta M had a three-stage configuration. The first stage was theLong Tank Thor, a stretched version of theThor missile, previously flown on theDelta L. ThreeCastor-2solid rocket boosters were attached to the first stage to increase thrust at lift-off. ADelta E was used as the second stage, and the third stage was aStar-37Dsolid rocket motor. On the final flight, six boosters were flown instead of three, in a configuration known as the Delta M6, or "Super Six."
All thirteen launches were made fromLaunch Complex 17A at theCape Canaveral Air Force Station (CCAFS). The first launch carryingIntelsat III F-1 on 18 September 1968, was a complete failure when the first stage began suffering abnormal pitch gyrations starting at T+20 seconds. The booster maintained a stable attitude until around T+100 seconds when it pitched over and began to break up from structural loads. As the Delta was also headed back towards land,Range Safety Officer sent the destruct signal at T+108 seconds. It was bound for aGeostationary transfer orbit above theAtlantic Ocean and be in operation in time to relay broadcasts of the next month's1968 Summer Olympics inMexico City.[1][2][3]
The fifth launch on 25 July 1969,Intelsat III F-5 suffered a rupture of either the third stage casing or nozzle and ended up in an unusable orbit. Of the thirteen launches, twelve carriedgeosynchronouscommunications satellites. The thirteenth, which was the final flight and the only one in the Delta-M6 configuration, placedExplorer 43 into ahighly elliptical orbit.[4][5]
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