The Manta-Ray was mostly an experiment in animal form aesthetic, but ended up being a fair design for a really safe, slow, and stable plane. It runs on electric charge and hydrogen. I didn't get it orbital, and it's not particularly acrobatic, but super stable. It rolls well, but is a pain to pitch back and if not anticipated, will cause problems. Perhaps a multi-atmospheric submersible design could be inspired by this little guy. I wanted to design a plane that looked like a Manta Ray and this was the first round draft. (Name changed because I just found out about the x-44)  

The second attempt at a Manta Ray inspired plane looks good, but is tough to fly. Once flying the plane is extremely stable, but again does not pitch back well at high speed. Still running on electric charge and hydrogen, the best parts of this plane were the look and the name. The Hydray.1 inspired the name for my second novella, and a very different craft. More about that later.