New Russian heavy ICBM - Sarmatian

Sarmat intercontinental ballistic missile. Cosmodrome Plesetsk

Roscosmos plans to start shipping Sarmat missiles to armed forces in fall - company CEO

https://tass.com/science/1440741

During launch an ICBM is at its most vulnerable because normally it is a long slow climb with an enormous fireball behind it making spotting it from space or aircraft from several thousands of kms away quite easy with most IR devices.

Sarmat has improved engines that burn faster and get the missile through this vulnerable launch phase as quickly as possible making attacks during this phase rather more difficult, or less likely to be effective.

HIgher energy faster burning fuels and more powerful first stage engine.

These missiles are multi stage with each stage requiring less power because it is lifting less.

Less power is not a bad thing because it often effectively means longer burn time and can lead to much longer range.

Think of it like a road trip in a car... ideally you are on an open flat plain with a nice firm dry surface where you can accelerate rapidly.

Say your car operates most efficiently at 140km/h, that would suggest that starting your car and rapidly accelerating through the gears to get to 140km/h as quickly as possible and then effectively idling along at 140km/h in your top gear is the most efficient way to burn your fuel... driving straight and not slowing down for anything.

Previously I have suggested that flying slow would be a good method of extending range like the version of Club that has a turbojet cruise missile with a rocket supersonic terminal stage... each stage compliments the other... the subsonic turbojet stage gives subsonic efficient fuel use so you can get perhaps 1,500km worth of flight range with the turbojet flying at medium altitude at maybe 600km/h... it could fly 850km/h easily but at 600km/h it might fly an extra 500km further than at full throttle all the way. Then near the target the missile drops down low where it is hard to spot and fires its rocket which accelerates it to mach 3.

I had previously suggested replacing the rocket section with a scramjet section, where the missile travels at subsonic (ramjets work at most forward speeds even if they are most efficient at their rated speeds)... but now I realise getting to high speed fast is actually more sensible unless the weapon is horribly under powered and is all fuel.

Accelerating to high speed and high altitude early in the trip means higher average speed and less fuel burn to maintain that speed.

With a rocket you can change the power levels of each stage but that effects its performance, so you need to have good reasons to do so.

In the case of the car, to get an efficient cruise speed of 140km/h you might have a 250hp engine and perhaps a 6 speed gearbox, and those gears oriented to speed rather than cross country use.

If you wanted to travel at 300km per hour then you need a much more powerful engine, which will the gear and transmission requirements and also the size of the vehicle and how much fuel needs to be carried.

To lift off faster it does not need to be lighter.... even if it is... more powerful rocket motor with more energetic rocket fuel and a more efficient way of burning that fuel might be enough to get the required speed improvements.

The claim it can be launched via the north or south pole is a little odd... if you look at a globe, a sphere and you draw a line between any two points on that sphere you can continue that line around the sphere to return to the point you started at. If the two points are 10 metres apart then obviously the direct route is going to be 10 metres long, but you can also approach the target by going in the opposite direction and travel the entire surface of the earth minus 10m and hit the target.

That is what they mean by north and south pole directions... if the target is 5,000km away you can launch this rocket directly at the target... to hit it, or you can launch it in the opposite direction and it will still hit it but coming from the opposite direction... an unexpected direction where no defences are currently set up to spot an incoming attack except SSBNs...

Obviously this is massively complicated by the fact that the earth is spinning so your flight to 5,000km wont be a straight line but will appear to be a curve when drawn in real time on the surface of the planet... and the same for the launch in the other direction.