Luna 25 lander mission, Russian lander following on from the Soviet-era lunar program Options

[Phil Stooke]

I am starting a new thread for this mission which should fly this year.

Phil

[kenny]

And the Soviet moon landings had a lot more than 1 failure, and a lot more than 5 attempts (if that is what "trials" means).

[rlorenz]

And the Soviet moon landings had a lot more than 1 failure, and a lot more than 5 attempts (if that is what "trials" means).

You're quite right. The supplement notes
Data in this section are drawn from a variety of sources, principally Wilson (1987), Ball et al. (2006) and
Harland and Lorenz (2006) together with contemporary internet sources (Wikipedia entries for Soyuz,
Falcon 9, Luna Program, Cromwell's Rule, downloaded November 2018). Various judgements are made
regarding the accounting of specific examples which could lead to small adjustments in estimated
probabilities. The principal message, that probabilities of success are not (and are sometimes far from)
unity, is robust to the subjective component of these assessments
.....
.....
The Soviet lunar exploration program featured 2 successful semi‐hard landings (Luna‐9 and ‐13), two
successful landers with Lunokhod rovers (Luna‐17 and ‐21) and one rover that failed to depart Earth.
This set of 4 successful landers yields PL~0.83, although adding sample return landers to the set brings
this probability rather lower. Soviet Mars landing attempts Mars‐2, ‐3, ‐6 and ‐7 yielded only 20
seconds of transmission from the surface from Mars‐3 – depending whether that is considered a success
or not, we have 0.17<PL<0.33, although factors contributing to this particularly dismaying performance
were known at the time (e.g. Perminov, 1999).


I forget why I excluded the sample return landers. Note that missions lost on launch would have been rolled up
into the launch success number (i.e. PL is conditional on getting delivered to a landing trajectory, although I
forget why I included Lunokhod-0....) Anyway, I maintain the remark above, that the overall conclusion (that
loss probability on landing attempts is ten to tens of per cent, and not just a few per cent as the Challenger-like
risk assessments always seem to say) is robust...