Split the work across four spacecraft

Lavochkin identifies two M-73 configurations: Mars 4 and 5 were intended as orbiters, while Mars 6 and 7 carried probes for descent from flyby trajectories. Four launches in July and August 1973 divided the work that a learner might otherwise assume every spacecraft could do. The flyby carriers were not simply additional planned Mars satellites.

Perminov explains that the departure and arrival conditions complicated retaining the earlier Mars 3 combined architecture within the available performance. Splitting the tasks was an engineering response, but it created dependencies: a delivered lander still needed a viable data path, and an intended relay had to be available when needed. Counting spacecraft alone does not describe the system.

Mars 4 failed to enter orbit but returned flyby observations. Mars 5 reached orbit and returned images during a short operating period. Mars 6 returned information during atmospheric descent but no successful surface mission followed; the Mars 7 probe missed the planet. These outcomes should not be flattened into either four complete successes or four identical failures.

In an original report, use one row for the planned role and another for the achieved operation. A spacecraft intended as an orbiter may become an unplanned flyby observer. A descent measurement is atmospheric evidence even when the intended surface experiment fails. The scientific claim must follow the actual observing location and instrument record.

Separate the planned role from the achieved result

Perminov’s account describes concern about a transistor manufacturing change and failures found during preparation. He relates the decision to launch despite reliability concerns to the available schedule. This is an attributed engineering history, not a reason to assign every individual failure in the series to one component without supporting evidence.

In an original reliability exercise, two otherwise independent boxes contain the same defective component batch. Adding the second box can help against some isolated failures, but it may not protect against that shared defect. A review should investigate common materials, manufacturing processes and software as well as count the backup units. Redundancy is a design strategy whose benefit depends on the failure assumptions.