Fictional planets of the Solar System while yet others are purely fictional and were never intended as serious hypotheses about the structure of the Solar System. Vulcan was a hypothetical planet supposed to revolve around the Sun inside the orbit of Mercury, invoked to explain certain irregularities in Mercury's orbit. The planet was proposed as a hypothesis in 1859, and abandoned not later than 1915. The name "Vulcan" has been used for various other fictional planets, in and out of the Solar System, that do not correspond to the hypothetical planet Vulcan. The planet Vulcan in the "Star Trek" franchise, for instance, is specified as orbiting
Venus Atmospheric Maneuverable Platform of a lenticular shape which would significantly simplify packing, deployment sequence and structural mass, but it would not cruise so efficiently. The vehicle concept was also presented in May 2017 as a proof-of-concept for exploration of other planets and moons of the Solar System with an atmosphere. The 2013 preliminary concept envisions a suite of instruments NASA calls the 'Venus Flagship Design Reference Mission' for a balloon. Its mass is estimated at 20 kg and would require 50 W of electrical power to operate. The notional intuments consist on: There are ongoing discussions about possible NASA participation in Russia's Venera-D