The Sarmat is a direct response to the development of the American “missile defence shield” based both on ships and on land (mainly in Poland and Romania). Its entire design is aimed at defeating the American interception capability and thus restoring Russia to parity in nuclear deterrence. This weapon is one of the six new nuclear weapons with which the Kremlin plans to modernise the nuclear arsenal. It is also important to understand that the danger of this weapon lies not only in the launcher (RS-28) but also in its payload, namely the Avangard (hypersonic glide vehicle) as we will see below. Together, the two provide Russia with FOBS capabilities.
In order to understand why the weapon is groundbreaking, I need to refresh you on the concept of ballistics and other physics concepts that you probably studied in high school.
As the name suggests, an Inter-Continental Ballistic Missile follows a ballistic trajectory. Ballistics is an easy concept to understand, it’s in our everyday lives. When you throw a snowball, the trajectory of the projectile is ballistic or parabolic, i.e. it goes up, hits a ceiling and comes down. In essence, an ICBM is the same, except that the “arc” it makes is much larger, with the ceiling of the arc being around 1200km. Mankind has never before had such long-range weapons, but this range is not unlimited, as it has to follow this trajectory unless the object is left in orbit, which is limited by nuclear treaties.
It should be noted that all modern missiles make use of MIRVs (Multiple Independently targetable Reentry Vehicle). In the same way that a SpaceX rocket carries many Starlink satellites at once, a single nuclear missile carries several bombs.
The Fractional Orbital Bombardment System (FOBS) is essentially an orbital aircraft, a hybrid between a satellite and an aircraft. Like everything else in this world, each weapon offers some disadvantages and some advantages. The main disadvantage of FOBSs compared to traditional ICBMs is that they cannot carry such heavy payloads, and they are also somewhat less accurate, but this is an issue that is now largely solved with respect to the FOBS technology that the Soviet Union experimented with.
The main advantage is that by performing an orbital “flight” at about 150km above the earth, it allows it to have an essentially total range over the earth. In this way, Russia does not have to deliver its weapons via the shortest route ( where NATO’s radars and interceptors are). Instead, it can choose to deliver its weapons from the opposite side. For practical purposes, this means that Russia can attack the US not by flying over the North Pole or the northern area of the Earth in general, but through the South Pole. This poses a problem for detection and especially interception. Not only that, but Avangard warheads can glide at high speeds, making it even more difficult to predict their path. Predicting a ballistic trajectory is very easy, we only have to look at how the Israeli Iron Dome is able to predict the routes of missiles launched at Israel and intercept them effectively.
As I said before orbital weapons are prohibited by the 1967 OST treaty, however there is a small technicality that makes these weapons legal (there is no consensus on this, but at least there is some legal protection) “violation would need to entail space-based nuclear weapons, not ground-based systems that temporarily placed prohibited weapons into orbit, Taunton Paine 1967”.
The missile itself (RS-28) also has a number of other measures to make it more difficult to detect, such as A short boost phase, which shortens the interval when it can be tracked by satellites with infrared sensors, such as the U.S. Space-Based Infrared System, as well as a number of other unspecified countermeasures.
The missile silos will also feature the “Mozyr” active protection system, designed to deny potential adversary’s first strike advantage by discharging a cloud of metal arrows or balls kinetically destroying incoming bombs, cruise missiles and ICBM warheads at altitudes of up to 6 km.
Testing of the PDU-99 (ПДУ-99) main engine was successfully completed in August 2016. And on 20 April the first firing of the full rocket was made, expected to enter active service by the end of 2022. The Avangard warheads have been in production since 2018. By the end of the year, the Satan II will enter active service, one of the six new strategic weapons Putin promised Russia (and the World).