Using an Atlas V 551 launch vehicle, a ballistic/chemical option with a reduced payload and favorable trajectory performance assumptions was estimated at the lowest cost. More expensive options utilized SEP and a similar launch vehicle or a chemical propulsion system using a Delta IV Heavy.
Additional challenges identified included the availability of an Advanced Stirling Radioisotope Generator (ASRG) and the plutonium-238 to fuel it.
Because of the complex and challenging nature of this mission, a more detailed characterization study is needed before moving forward with the Mercury lander concept. Both SEP and ballistic trajectory approaches and concepts should be further explored with a more detailed mission design and concept definition in order to determine the preferred mission implementation approach. Currently each approach has benefits and risks that could not be fully characterized at this level of study.
VENUS MOBILE EXPLORER
The Venus Mobile Explorer mission concept study was performed by NASA’s Goddard Space Flight Center.
The purpose of this RMA study was to determine whether a Venus mission with surface or near-surface mobility and realistic operational lifetime could achieve meaningful surface science at two or more independent locations separated by several kilometers. Of particular interest was a metallic bellows concept for aerial mobility.
• Determine the origin and evolution of Venus’s atmosphere, and determine the rates of exchange of key chemical species between the surface and atmosphere.
• Characterize fundamental geologic units in terms of major rock-forming elements, minerals in which those elements are sited, and isotopes.
• Characterize geomorphology and relative stratigraphy of major surface units.
This mission’s space segments consist of a probe and a flyby carrier spacecraft that is also used as a communications relay. The probe consists of two top-level elements: the entry and descent element, which includes the aeroshell and parachute systems; and the lander. The lander has two major systems—one being the gondola that carries the science instruments and subsystems inside a thermally protected pressure vessel and the other one being the bellows aerial mobility system, including the bellows and the inflation subsystems. Two 20-day launch windows were considered, in 2021 and 2023, with an initial flyby and a second Venus encounter approximately 112 days later.
Significant development risks with respect to this mission include bellows concept development; safe landing assurance; test facilities for large test articles to simulate Venus’s high temperature, high pressure, and chemical environment; critical events timing; and Raman/laser-induced breakdown spectrometer development. Operation risks include bellows mobility, safe landing, and aeroshell operations. Uncertainty exists in the technology development cost owing to the relative immaturity of some of the essential technologies.