The Thor DSV-2U or Thor LV-2F Star-37XE Star-37S-ISS was an American

expendable launch system An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are destroyed during reentry or impact with Earth, or discarded in space. ELVs typically consist of s ...

used to launch five DMSP

weather satellite A weather satellite or meteorological satellite is a type of Earth observation satellite that is primarily used to monitor the weather and climate of the Earth. Satellites are mainly of two types: polar orbiting (covering the entire Earth asyn ...

s between 1976 and 1980. It was a member of the

Thor Thor (from ) is a prominent list of thunder gods, god in Germanic paganism. In Norse mythology, he is a hammer-wielding æsir, god associated with lightning, thunder, storms, sacred trees and groves in Germanic paganism and mythology, sacred g ...

family of rockets, and a derivative of the Thor DSV-2. The first stage was a

missile in the DM-19 configuration. A Star-37XE was used as the second stage, and the third stage was a Star-37S-ISS. Thor boosters used an erector system to hoist them up to the pad. While common on Soviet launch vehicles, this method was unusual in the US space program.

Launches

Thor DSV-2U was launched five times between 1976 and 1980 from Space Launch Complex 10W at the

Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg S ...

. All launches carried DMSP 5D-1 satellites The final launch (Thor 304) occurred on July 14, 1980 and was a failure.

Thor 304 failure

Thor 304 had been erected on the pad a few weeks before launch, and during this step, a connecting pin in the erector broke and sent the rocket falling back down to ground level. Launch crews examined the Thor for damage, but could not find any outward indication of it. The booster passed routine preflight systems checks and liftoff took place at 6:22 PM PST on July 14, 1980. Shortly after liftoff, the Thor's telemetry system failed, but weather conditions and visibility were excellent, and the booster could be tracked visually for over two minutes. Telemetry from the DMSP satellite indicated that it was operating properly. SECO took place on time, as did the second stage burn. Third stage burn began, and then after about four seconds, all telemetry abruptly ceased. The initial assumption was that the third stage exploded, and initial

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press releases about the launch stated such. However, radar tracking showed that the third stage motor continued operating as it drove the DMSP into the Pacific Ocean. The investigation board concluded that connectors in the electrical interface between the second and third stage had been jolted loose by the erector mishap several weeks earlier. After second stage burnout, staging failed to take place due to the misaligned connectors, and the third stage motor thus fired with the spent second stage still attached to it. The force from the third stage motor burning managed to tear the second stage free, but in doing so, it ripped out wiring in the base of the third stage, which shorted out the guidance computer and caused it to direct the stage and spacecraft down into the ocean. Much like the DMSP failure in 1976, the incident was attributed to poor program management.

References

Thor (rocket family) {{rocket-stub