I feel bad for Neptune. Only one spacecraft (Voyager 2) has ever been there, and it didn’t stay long.
Neptune is the planet farthest from the Sun, so getting there is an extra special challenge. It’s not only a question of distance. It’s also a question of gravity. Spacecraft require ludicrous amounts of energy to travel that far, given that the Sun’s gravity is constantly trying to pull them back.
But right now (between 2015 and 2019), the planets are aligned to make a trip to Neptune easier. With a gravity assist from Jupiter and another from Saturn, a small spacecraft could build up enough momentum to fling itself toward Neptune, using relatively little fuel in the process.
Like Voyager 2, the Argo spacecraft (as NASA called it) wouldn’t be able to stay long. By the time it reached Neptune, Argo would have built up so much momentum that it wouldn’t be able to slow down enough to enter Neptunian orbit.
But hey, a flyby mission is better than no mission at all. As added bonuses, Argo would also have opportunities to collect data about Jupiter and Saturn while performing its gravity assist maneuvers. Mission planners also designed an orbital trajectory that would allow Argo to get some extreme close-ups of Triton, Neptune’s largest moon. Argo would also be able to visit a Kuiper belt object some time after its primary mission ended.
All of this could be done within the strict spending limits of a New Frontiers-class mission ($1 billion or less). That’s a real bargain, at least for NASA. So why aren’t we doing this?
The Great Recession hit at just the wrong time for Argo. The mission was still in early development when Congress slashed NASA’s budget. And now, even though NASA has some money again, there isn’t enough time to develop and construct a spacecraft before the 2015-2019 launch window closes.
Sorry, Neptune. Better luck next time.
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Today’s post is part of Neptune month for the 2015 Mission to the Solar System. Click here to learn more about this series.