[X] My Assistant

[Guest_Myran_*]

Seeing descriptions and even images of old projects that never did get underway, my memory was stimulated into remember 'The grand tour' plans.

Back in the 1960 the proposal was to fly no less than 4 spacecrafts, each with atmospheric probes for the four gas giants and one even with a flyby of Pluto after swinging past Jupiter and Uranus.

The proposal for this project did fare the same way as many other ambitious plans, that of limited funding but it was skillfuly advocated and eventually ended up with the dual Voyagers (which btw originally only was planned for flyby's of Jupiter and Saturn).

Regardless, if anyone remember some tidbits or even sits on more specific information I would be happy to have my memory refreshed. Thank you in advance!

[dvandorn]

Exactly -- each mission does, indeed, build upon what we learned from the last one. Without the Pioneers, we might not have designed the Voyagers to properly withstand the radiation environments at Jupiter and Saturn. Without the Voyagers, we wouldn't have had nearly as good an idea of which instruments would give us the best scientific return from Cassini. (For example, had we not done the Titan flyby during Voyager 1, we might not have included RADAR on Cassini.)

My memory of the whole Grand Tour concept is that, sometime in 1968 or 1969, I saw a proposed plan for two Grand Tour spacecraft that would require Saturn V boosters. They would take advantage of the late-70s launch windows to send both spacecraft to each of the outer planets in turn, with entry probes for the gas giants and, IIRC, a Titan hard-lander.

When NASA decided to shut down the Saturn V production line in late 1969, the people at JPL proposing the Grand Tour mission took it rather poorly, insisting it was total madness to pass up an opportunity like this. They made some enemies at other NASA centers with their vehemence. For a while, no plans for late-70's outer Solar System exploration were allowed to have the words "Grand Tour" in them -- it got that bad.

Pioneers 10 and 11 were already in the pipeline, and a follow-on mission, consisting of similar Jupiter/Saturn flybys *only*, was being developed that later became the twin Voyagers. But during the process of designing the Voyager missions, the Grand Tour aspects were played WAY down. It was as if the JPL teams were told that bringing up Grand Tour was a good way to kill the Jupiter/Saturn flybys. But, at the same time, they designed both spacecraft with enough power and maneuvering gas to handle the full Grand Tour -- with a little bit of luck.

So, at least the way I remember it, we got almost all of our Grand Tour mission by selling it as *only* a set of Jupiter/Saturn probes, and sneakily adding the Uranus and Neptuine encounters only after the spacecraft were in flight. Even though the Grand Tour was implicitly designed-for during spacecraft and mission development, it was simply not discussed in detail for fear that those who thought they had "killed that Grand Tour nonsense" wouldn't notice until it was too late...

-the other Doug