Tom Swift and the SubNeptunian Circumnavigation

In book 26 of this new series, Tom Swift is requested to head a consortium of nations in developing and flying a new type of mission into space. He finds himself developing a brand new vessel, one that likely needs to fly into the sky, through space at incredible speeds, and plunge into the thick atmosphere of the only other blue planet in our solar system, Neptune.There are several things going against him starting with all he unknowns about the distant planet and its blue ocean that appears to be mostly liquid methane. How in the world, or out of it, can you get through something that might be absolutely solid once you get under the surface. Then, how to you withstand the pressures from a compacted, nearly frozen liquid that is thousands of kilometers thick?To top things off, one of the nations funding this project insists he bring back several tons of what they believe will be priceless methane diamonds. If he refuses, or if they believe he is holding out on them, there might be political and economic repercussions!