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Per Gunter's Space Page for Viking-DS (VDS):

Viking-DS or VDS (Viking Dynamic Simulator) was a vehicle evaluation payload, which was to represent the dynamic properties of the Viking spacecraft.

It was to be launched to a near-GEO orbit during the maiden flight of the Titan-3E Centaur-D1T launch vehicle, without being deployed from the Centaur stage. The only purpose was to determine the flight loads to which the real Viking probes would be subjected. On top of the VDS the SPHINX satellite was mounted to be deployed into a GTO orbit.

Due to failure of the Centaur stage to ignite, the payloads did not achieve orbit.

Question: It seemed like a good idea at the time, why was this important test ultimately skipped and no second attempt made?

Viking-DS (VDS)

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When you are testing a brand new rocket, particularly in that era, you didn't put a valuable payload on top. Typically mass simulators were used. There actually was a primary mission, as is indicated in your quote, but the mission was successful enough to more or less demonstrate the rocket would work.

It was never launched because they got more than enough data from it. The roughest part of a rocket launch is usually the first bit, the failure was so late (T+742) that effectively the entire mission had been complete for a mass simulator.

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  • $\begingroup$ Was the SPHINX satellite chopped liver? $\endgroup$ Jan 29 at 4:49
  • $\begingroup$ My quote says "The only purpose was to determine the flight loads to which the real Viking probes would be subjected." Was that objective satisfied? This particular payload's purpose was not to "more or less demonstrate the rocket would work" which it didn't either it seems, but that's beside the point. $\endgroup$
    – uhoh
    Jan 29 at 4:58
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    $\begingroup$ It's hard to know without original data, but I think it is very safe to say that with 742 seconds of flight that objective was satisfied sufficiently. For comparison, the recent SLS test, which was trying to fire about 8 minutes, would have been considered successful with only 250 seconds. $\endgroup$
    – PearsonArtPhoto
    Jan 29 at 12:26
  • $\begingroup$ Yes that sounds reasonable; do you think you can add that back into your answer? I think it really helps. $\endgroup$
    – uhoh
    Jan 29 at 22:32
  • $\begingroup$ Not sure what you want me to add that isn't in the last sentence, but... $\endgroup$
    – PearsonArtPhoto
    Jan 30 at 1:10

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