More details are emerging about Russia’s new RS-28 Sarmat intercontinental ballistic missile.

According to Russian media, the weapon is being developed to replace the massive but ageing 210-ton R-36M2 Veovoda (SS-18 Satan) missile which has a throw weight of roughly 8.8-tons.

However, most Western experts believe that the weapon is more likely a replacement for the smaller 106-ton UR-100N —also known as the SS-19 Stiletto. In fact, there are conflicting reports about the size of the RS-28, which has been given the NATO designation SS-X-30 Satan 2.

According to state-run RIA Novosti, the Sarmat weighs slightly less than 110-tons and has a throw weight of about 5-tons. It is being specifically designed to defeat any potential American missile defense system that might be developed to counter Russia’s strategic nuclear deterrent. It is also being designed to withstand a first strike—being able to absorb seven nuclear warheads compared to the two hits its takes to destroy an American Minuteman III silo.

“The launch silos of the new missiles will be physically protected as much as possible - to completely destroy one launcher, it will take at least seven nuclear strikes of high accuracy,” the RIA report states.

The missile—if the RIA report is correct—will carry the same number of warheads—or more—as the much larger SS-18 and far more than the six warheads on the SS-19. However, that being said, there have been conflicting reports as to how large the RS-28 is. While some reports suggest that the weapon will be roughly 110-tons, others have suggested that the new missile will be larger than even the SS-18, which is the largest ICBM ever built.

“The range of Sarmat will exceed 11 thousand kilometers, the missile will be able to carry 10 to 15 warheads of up to 750 kilotons each,” the RIA report reads.

“The warheads will fly to their targets at hypersonic speeds under individual guidance programs. It will not be easy to intercept the multiple independent reentry vehicles: depending on the situation, they will be able to maneuver like winged or hypersonic missiles.”

American experts believe that the RS-28 is more likely to be an SS-19 replacement than an SS-18 replacement. The weapon, in their view, is most likely closer to the 110-ton range.

“The concept of the Sarmat as an SS-18 (Voevoda) follow-on has always been mostly PR. The Russians have long been fairly proud about the Voevoda as the heaviest ICBM in the world, which NATO code-named Satan,” Olga Oliker, director of the Russia and Eurasia program at the Center for Strategic and International Studies (CSIS) told The National Interest.

“The Voevoda is going away, but if you’re proud of something, you don’t just give it up, you build something even better. Hence the sales job on the Sarmat as the Voevoda's replacement. That was reflected in all the stories promising a ten-ton throw-weight (the Sarmat’s is 8.8 tons). In fact, however, the Sarmat looks more like the SS-19, which is also going away. Both the Sarmat and SS-19 weigh about 100 tons (as opposed to the Voevoda’s 200 tons) and specialists have speculated that the throw-weight on the Sarmat would also be similar to the SS-19s 4.4 tons. This story certainly takes us closer to that, though we’ll have to wait and see what actually gets deployed.”

Michael Kofman, a research scientist specializing in Russian military affairs at the Center for Naval Analyses, agreed with Oliker’s assessment.

“Sarmat is really more the successor of the SS-19 Stilleto rather than the SS-18,” Kofman told The National Interest.

“There is conflicting information on the size, tonnage and throw-weight of this missile, but generally it seems to be much smaller than the SS-18 Mod 5 and slightly larger than the SS-19. If you check the payload for the SS-19 you will see that it was 4.35-tons.”

While the RS-28’s reported throw weight of 5-tons is reasonable, there is a disconnect between that figure and the number of warheads and decoys carried onboard the new missile.

“Assuming that this missile is larger than the SS-19 by some amount, and with technology better than what was available in 1970s, it seems quite reasonable that the throw weight is in the 5-ton range, but it does not explain other claims about warheads and decoys,” Kofman said.

“If RIA is right—and it probably is not right—how do you fit a payload of 10 warheads and tons of decoys into 5-tons?”

The RIA report does seem to indicate that the RS-28 is closer in size and capability to the SS-19.

“The only thing this helps substantiate is that Russia's next heavy missile is much closer to the size of the SS-19 than the SS-18, but there are large questions outstanding about conflicting claims about throw-weight, warheads and penetration aids,” Kofman said.

“They are mutually inconsistent.”

Ultimately, the RS-28 will likely have fewer warheads and more decoys and other systems to increase its survivability.

“The further along we get it becomes clearer that this is a replacement for the SS-19 with more warheads and penetration aids,” Kofman said.

“I think current trends in Russian thinking will place a premium on penetration aids, and as such the missile may compromise on number of warheads. RIA's payload figures are not at all unreasonable, but equally unreliable.”

The consensus in Washington is that the new weapon is indeed a SS-19 replacement. Though The National Interest was not able to contact him in time for this story, Russian nuclear weapons expert Pavel Podvig has long suggested that the RS-28 is a SS-19 replacement. It seems his hypothesis was likely correct.

Dave Majumdar is the defense editor for The National Interest. You can follow him on Twitter: @Davemajumdar.

Image: Reuters.