Why have some space exploration breakthroughs not been retried for the last 50 years?

Question

The last successful probe to land on Venus was Venera 10, 1975. There was also Venera 11 & 12 shortly after, but both experienced camera failures or multiple instrument failures. Why haven't we attempted either of these since, especially with the latter being two partial failures. Why use our greatly improved technology over the last 50 years to send another probe to the surface of venus with better protection and better instruments to collect more thorough and precise data?

Answer 1

The "why do we as mankind do..." type of questions are hard to answer as there is no single body who decides what "we" do, nor are there single reasons why a space mission is selected to be built and flown by the major scientific institutions or not.

However, NASA, ESA, JAXA etc, they all have to justify their spendings to the funding governments and in essence to the population of their countries. The return is in scientific output and in public attention being given to the results. The possibilities of a mission in these two fields have to be weighed against the risks associated with the mission, thus the likelyhood to be successful and how much you need to spend to get the promised or desired type of results.

In regards to risk, missions to Venus surface are tricky as the conditions are extremely inhospitable: you need probes which operate FAR beyond the usual thermal environments under extremely corrosive conditions in a high-pressure environment:

• surface temperatures of 700K or above are beyond what usual electronics are designed to operate at, and they simply fail. So either you need an even much more elaborate thermal system than you need anyway for any space mission. And as you cannot get rid of the heat entirely on the surface (you don't have any side pointing to cold space), thus you do have intrinsically a very limited lifetime for any surface module.
• The need to design for high pressures (90bar, thus about 90 times that on Earth) requires for extremely stable mechanical design. A stable mechanical design means you need to carry more weight for the same effect as in environments where mechanical loads are less strong
• The need to design the probe for an extremely corrosive environment of the Venus atmosphere (clouds of sulfuric acid in 30...60km height, sulfuric acid occasionally below) means that you might not be able to use many of the usual solutions as they simply would corrode and fail quickly.

So, yes, a new mission to Venus, especially with operation on the surface, definitely would be interesting. However the technical challenges are extreme, and the technology might be much less tested for these kind of environments than all other bodies in the solar system, including the Sun itself (there you have cold space on the backside to manage your thermal equilibrium). Thus the low-hanging fruits are picked first. Missions to Venus' orbit which obtained detailed radar images, investigated composition and dynamics of her atmosphere and magnetosphere have been conducted at a similar level of detail as other planets or bodies with the orbiter missions of Magellan in 1989 or Venus Express in 2005 and numerous fly-bys by other missions. Their number is smaller indeed as no follow-up landing missions was planned or deemed likely.

NASA has an outlook on planned space missions. It lists for 2031 the launch of Veritas (NASA) and Envision (ESA) missions for Venus orbit. And for 2029 there is the launch of the Davinci mission with a descent probe into the atmosphere.