Let's assume for a moment that Roskosmos generated an HLV capable of ~20 tons post TLI to a lunar trajectory (4 times the capability of Proton-M today).
I am positing here that Briz-M, under those conditions, might make an excellent lunar landing system. The Briz would require the addition of a crewed cabin, something on the order of a Soyuz orbital module, with a docking system on top.
The concept of operations would be that the Briz would sent towards the Moon, and use its engine to brake into lunar orbit. Some sort of manned vehicle would then rendezvous with the Briz, one or two crew would transfer over, and the Briz would then perform the lunar landing (landing gear would be attached to the APT).
After the end of surface operations, the Briz core would separate from the APT, leaving all equipment not required for the return to Earth attached to the APT. The Briz core would then reach lunar orbit, and rendezvous with the return spacecraft.
The return spacecraft could even be Soyuz, equipped with some extra propulsion, and larger engines.
I don't know if the Briz-M would require a full propellant load for this mission, so it may be the case that some prop could be offloaded to allow more mass in the pressurized section.
Potentially very interesting thread - because there's a finite chance someone might go do it this way, or variations of, someday!
Ending as a lunar lander might be a strange fate for a piece of hardware that started its life as anti-satellite weapon... but it already believes itself an upper stage, so...
I love the idea of expanding the drop-tank into a full-on descent stage! But does the Briz-M engine have the thrust required for lunar braking descent? Apollo LMDE: 45.04 kN; Briz 14D30 engine: 19.62 kN.
Let's assume for a moment that Roskosmos generated an HLV capable of ~20 tons post TLI to a lunar trajectory (4 times the capability of Proton-M today).
No need for an HLV, you could put a lander through TLI mostly dry. The Russians already have the necessary refueling systems. Instead of refueling in LEO as is done today, you would have to refuel in LLO or at L1/L2.
I love the idea of expanding the drop-tank into a full-on descent stage! But does the Briz-M engine have the thrust required for lunar braking descent? Apollo LMDE: 45.04 kN; Briz 14D30 engine: 19.62 kN.
19.62 kN would give a TWR of 1 on the moon for a lander with a mass of 12000 kg (very roughly, if I did my top of my head calculations right). That's some very low thrust to work with for a lander and I doubt it's enough. Is there room for an extra engine of the Briz-M?
I love the idea of expanding the drop-tank into a full-on descent stage! But does the Briz-M engine have the thrust required for lunar braking descent? Apollo LMDE: 45.04 kN; Briz 14D30 engine: 19.62 kN.
19.62 kN would give a TWR of 1 on the moon for a lander with a mass of 12000 kg (very roughly, if I did my top of my head calculations right). That's some very low thrust to work with for a lander and I doubt it's enough. Is there room for an extra engine of the Briz-M?
Actually, since your 12,000 kg represents the mass in orbit, the Briz-M has enough thrust for braking, and as its tanks empty, the T/W gets better.
However, the larger issue is that the engine does not have a throttle, and engineering a throttle into the Briz engine may be problematic. Briz does have some additional small thrusters, but I don't know how useful they would be in this application.
The largest issue is the unreliability of the engine. This probably screams for some sort of backup engine, and once that is invoked, then a clean sheet design might be preferable, or at least a different core (the APT might be useful).