What is the maximum space program possible with only medium-lift rockets?

So e of pi's Dawn of the Dragon TL got me thinking about the maximum possible space program possible when limited to launches of 25 tonnes to LEO or less (or to put it another way, what could the US or the Soviets do if their largest rockets were the Titan IV and the Proton).

How far could NASA, say, get if they had decided against developing any sort of heavy lift capacity and focused instead on EOR, modular space stations, gemini style capsules, mini shuttles and orbital LOX depots?

What I've managed to find on the subject of orbital LOX depots (as well as orbital N2O4/Aerozine depots and Ker-LOX depots) seems to indicate that the economics of such depots should be more favorable than the economics of HLLVs and offer similar capabilities for getting missions to Luna or Mars. I've also read that fuel transfer in microgravity poses problems.

fasquardon
 
So e of pi's Dawn of the Dragon TL got me thinking about the maximum possible space program possible when limited to launches of 25 tonnes to LEO or less (or to put it another way, what could the US or the Soviets do if their largest rockets were the Titan IV and the Proton).
25 tons? What do you think the Chinese are, made of money? It's limited to 12 tons or less. :)

I've also read that fuel transfer in microgravity poses problems.
That depends a lot on the propellant type. Non-cryogenic transfer is a lot easier since they don't form gas layers--trasnfer of hypergols has been in common use between Progress and various stations since about the 70s. It's a bit trickier with cryogenic propellants, but there's a lot of settling options available. For instance, Goff et. al. note that only about 10^-4 G is necessary, which can be provided by rotating a depot around its axis. Propellant settling is a solvable problem that's often exaggerated.
 
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why not instead of strap on boosters, just double or triple the main bodies? Triple Titan 2's?
 
why not instead of strap on boosters, just double or triple the main bodies? Triple Titan 2's?

Now I am imagining a double-main stage Proton!

I suspect achieving such a thing would be a difficult engineering problem due to the need to coordinate burn times, keep the noise from shaking the rocket apart etc.

fasquardon
 
With 25 tons to orbit, you can do a lot

Space station like Almaz/TKS or Mir size modular space station.
or launch man capsule on lunar fly by and return to earth like Zond
even land manned spacecraft on moon, with Earth orbit rendezvous were fuel tanks are assembly together with Space craft and launch to moon.
or send Almaz size space station on interplanetary fly by mission

if you manage reuse of first stage (like SpaceX Falcon 9) it even reduce the launch cost enormous, because you will launch allot of those for that.
 
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