And, the Russians/Soviets have long had a requirement for ICBMs with truly massive throw weight, going back to the SS-9. Their warheads/RVs tend to be a bit heavier than equivalent American warheads, but they’ve also kept very large yield weapons in use longer than anyone else (which weigh much more than lower yield devices). They have 5-7 ton RVs with yields on the order of 20-25MT that are beyond the weight capabilities of their solid rocket industry, so they stick with the hypergolic liquids they know so well.

So, while no one knows for certain, the Russians probably continue to use large storable hypergolic liquid engines on their ICBMs and SLBMs because the down-sides in terms of response time are marginal, and the up-sides for them are quite substantial. Plus, it’s a technology they’ve obviously mastered, so why change, especially when they seem to have difficulties with solid motors?

Trident Missile Test Fails
Sky News, Feb. 2024
https://youtu.be/g7qj5iwKMBU
2:26

https://www.nasa.gov/image-article/vanguard-rocket-test/

As someone noted yes if you intend to first strike the fueling requirement is less of an issue. But also as noted these are likely hypergolic fueled so can sit active for long periods. The main issue is the maintenance of these beasts. It is complicated and exacting, not like traditional soviet/Russian weaponry that was as simple as possible and will stand up under limited/poor maintenance.

Honestly I can’t imagine why once you have the Topol/Topol-M solid fueled weapon why you’d ever want to go back to liquid/hypergolic fuels for strategic weapons. It’s range is sufficient at 6800 NM (less than LGM-30 Minuteman III at 8700 NM but better than the Minuteman I/II). It can carry a 1 megaton warhead so throw weight seems enough, CEP is 200 M. Looks like this is a boondoggle to keep some sector of the military industrial complex happy/busy that NEVER happens in the US :-) .

Nukes require regular maintenance. They can’t just be stored in a bunker for years on end or sit on top of an IRBM, ICBM, or SLBM without regular maintenance. There’s a list of testing and maintenance that has to be done regularly in order to make sure the warhead goes ‘BOOM’ rather ‘fizzle’ if/when the time comes.

Sarmat was made from the start to also take satellite payloads like our Titan II modifications.

Sarmat has a solid kicker charge that pushes it up and out. SLBMs had ampulized hypergolics and the second stage nozzle immersed in the propellant tank of the first–staging by cutting the missile in half via primacord or something.

It took until the end of the Cold War to get a Minuteman/Midgetman equivalent in TOPOL-M which is their START smallsats launcher.

The Sarmat seems to be a Russified version of the most recent (more than three decades back) model upgrade of the Ukrainian-built R-36 with a good press agent. A number of the original R-36s were used as satellite launchers under the name Dnepr for a time. Many of the original R-36s are, in theory at least, still in service. How much they can actually be counted upon in a pinch is one of those 64 billion ruble questions to which even the Russians probably have no solid answer.

Russian maintenance of other portions of its strategic nuclear arsenal since the end of the USSR has not been impressive. The Dnepr had about a 5% failure rate in satellite launcher service. Any still-deployed R-36s are likely far iffier than that.

Much of the erstwhile Soviet fleet of ballistic missile submarines, for example, is now gone – and their missiles with them – and only a handful of replacements of questionable capability have been completed in the post-Soviet era. The Russian land-based ICBM force is probably similarly diminished and hollow – perhaps fewer than 100 servicable missiles remain after decades of cannibalizing some to keep the rest going. But I doubt we have any better an idea of just how much that is so than do the Russians. We’re good at finding out things the Russians know, but no intelligence apparat can get answers to questions even one’s enemies don’t know.

Even with time to do some working up – and the Russians have had over 2-1/2 years since invading Ukraine – I don’t think the Russians any longer have enough suitably reliable ICBMs to hazard kicking off a nuclear exchange – especially not with the entirety of NATO.

Just saying.