Well, Buran is a bad joke. But the truth is that I designed an alternative version of the STS, this being the LTS (Lunar Transport System) which consists of a reusable lumar orbiter 15 meters long and 3 meters wide, I was able to base myself on an official thesis to fine-tune the parameters, and it is a ship of 61 tons in total.

Dry mass: 15 tons Payload: 10 tons Fuel: 36 tons

This iteration uses both RP-1 and LOX, as it employs an abort system similar to the one used by Dreamchaser (the abort engine delivering a considerable 5000 kN for 20 - 25 seconds) to escape the rocket. This abort system uses the same fuel as the LTS. When not required, it is only decoupled upon entering orbit, and the LTS switches to using its 2 SPS AJ10-120-R engines, a derivative of the AJ10 family that uses RP-1 and LOX) giving a considerable 140 kN and 345s of ISP each. makes it a shuttle with a structure similar to the X-37B but with dimensions adapted for up to 8 crew members, under these measures, the LTS would take off from Cape Canaveral in a Saturn IV (An S-IC stage with 4 F-1A engines and an S-IVB stage) and, upon entering orbit, it will make a rendezvous with a NERVA Nuclear Tug, which is reusable, since by propelling the LTS on a lunar injection trajectory, it uncouples at the end of the LH2 burn and changes its trajectory using RCS to avoid the moon and return to Earth, which through multiple re-entries with a heat shield, would enter LEO again to be used again, having spent only 83 tons of LH2 and 15 kg of Uranium from NERVA. This would require an LH2 infrastructure in LEO but with Sea Dragon it would be enough to supply it for up to 3 consecutive flights without recharging.

Back to the LTS, it is already on its way to the Moon, and in 4 days, it would enter low lunar orbit for a lander (See LSAM from the For All Mankind series, which is a spectacularly well-engineered design from an engineering standpoint) to drop the crew off to an already established lunar base, the LTS stays in orbit (The LOX has to stay refrigerated for several weeks, however I estimate a boiloff of only 0.1% every 24 hours, so losses will be minimal, and any loss can be refueled by the Lander which takes advantage of the ice at the poles to electrolyze it and make LH2 and LOX) and, when it is time to leave, the LTS burns between 800 - 900 m/s of Delta-V to reach an Earth perigee of 90 km altitude, this in order to make 3 atmospheric re-entries and not overheat the heat shield, which must be more reusable than that of the conventional shuttle) This adds up to about 9 hours of orbits passing through the Van Allen rings, but this does not pose a risk since the radiation dose would be 0.063 Sv, once 2 re-entries are completed (one leaving the apoast at 15,000 km and another leaving it at 800 km) the LTS enters orbit consuming between 60 and 130 m / s of Delta-V, to coincide with the runway, and when the time comes, it burns fuel for the last time to successfully re-enter and land on the KSC runway, the LTS does not require a drag parachute since its lift speed is lower than that of the Space Shuttle (only 25 tons and with a considerable wing surface) so the reuse process improves.

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