Anything on an RLA-5 would still have to fit inside a 4 meter fairing, trying to cram 70 tons of probe into a 4m fairing that isn't so tall it fucks the aerodynamics would almost require making it out of steel and concrete just to say you're using the mass budget.
A hammer head fairing could get payloads of 6.7m diameter up no problem.
But to really get good use out of 70 tonnes of payload (probably closer to 80 tonnes if we actually built it, since this would be with 1970s improvements) even a hammer head configuration would make it hard to fit anything game changing.
Voyager, with both probes and the transfer bus, was 4 tons in LEO. Even the most morbidly obese hyper-Voyager with a Titan lander and way larger instrument budget that's 10x bigger would still fit on an un-upgraded RLA-3 with a chemical transfer stage. Any upgrades to the RLA or a nuclear transfer stage or whatever push that even higher. I really can't imagine any probe mission that would use an RLA-5, its utility outside a moonshot is limited to maybe a space station core and that's kinda it.
You could build a massive interplanetary probe that left chunks of itself at each stop (landers and orbiters and such) on a grand tour. The issue with that is that any economies of scale of such a thing would be more than offset by the risks of having maybe a decade of space program money all in one basket.
Since most of the money is R&D money and the RLA should have for the time competitive launch costs, it's far better to do multiple probes.
The real thing the RLA-5 would allow is lofting massive Earth Departure Stages that shoved a small probe somewhere real fast. Which is why a nuclear EDS is a competitor for this sort of work.
When we needed to go to the moon, using a RLA-5 for this sort of work would be the way to go, since the Lunar program would pay for the RLA-5, saving the trouble of making a nuclear EDS. But now that the RLA-5 has been cut, we will in future be choosing between a 15 rpt/turn (at best) RLA-5 program or a 5 rpt/turn nuclear engine program.
Which is all quibbling about details while loudly agreeing about the final analysis.
None of the things we could use the RLA-5 for are enough to justify the R&D needed to make the rocket.
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To go back to more serious matters, what's winning the vote?
'Cuz I've been convinced Dygai first and I remain convinced that backing the small farmers and prioritizing the unmanned programs are high priority.
So
@Crazycryodude's Plan Lunar Rationalization.
Regards,
fasquardon