The SS-X-31 (Russian designation: RS-26 Rubezh) is a Russian solid-fueled, road-mobile intercontinental ballistic missile (ICBM) currently in development. Although classified as an ICBM under the New START Treaty, the SS-X-31 has been tested with heavier payloads at ranges below 5,500 km, potentially putting Russia in violation of the Intermediate-Range Nuclear Forces (INF) Treaty.
SS-X-31 at a Glance
Originated from: Russia
Possessed by: Russia
Alternate name: RS-26, Rubezh, Frontier, Avangard, Yars-M, KY-26
Class: Intercontinental Ballistic Missile (ICBM) / Intermediate Range Ballistic Missile (IRBM) [classification disputed]
Basing: Road-mobile
Length: 12 m
Diameter: 1.8 m
Launch weight: 36,000 kg
Payload: 800 kg
Warhead: Nuclear, single warhead or MIRV
Propulsion: Solid propellant
Range: 5,800 km
Status: In development
SS-X-31 (RS-26) Development
Development of the SS-X-31 began in 2008 by the Moscow Institute of Thermal Technology. It is reportedly based on the RS-24 Yars ICBM, although Russia has acknowledged that the SS-X-31 has fewer stages and a shorter range compared to the Yars.1
The SS-X-31’s first test launch, which ended in failure, occurred September 28, 2011 at the Plesetsk Cosmodrome. The missile veered off course and crashed eight kilometers from its launch site.2
In May 2012, a second test was reportedly successful. The missile travelled 5,800 km with a single, light-weight warhead. As a result of this flight test, the SS-X-31 was classified as an ICBM under the New START Treaty, which seeks to limit and reduce the number of strategic arms between the United States and Russia.
A subsequent test in October 2012, however, flew 2,000 km with a heavier payload from the Kapustin Yar testing range to Sary Shagan (located in southern Kazakhstan). All flight tests since have also been flown to medium-range distances (between 1,000 and 3,000 km). This has raised questions concerning Russia’s compliance with the INF Treaty, which forbids the deployment of missiles with ranges between 500-5,500 kilometers.3
| Date | Launch site | Destination | Result | Distance |
| September 27, 20114 | Plesetsk | Kura | Failure | 8 km |
| May 23, 20125 | Plesetsk | Kura | Success | 5,800 km |
| October 24, 20126 | Kapustin Yar | Sary Shagan | Success | 2,000 km |
| June 6, 20137 | Kapustin Yar | Sary Shagan | Success | 2,000 km |
| March 18, 20158 | Kapustin Yar | Sary Shagan | Success | 2,000 km |
An exhibition to U.S. inspectors was planned for November 2015. However, it was cancelled and rescheduled for 2016. It has since been postponed until 2017. There has been little activity to indicate plans are moving forward to officially deploy the missile.9
SS-X-31 (RS-26) Specifications
The SS-X-31 is a solid-propellant, road-mobile ICBM. It is estimated to be 12 m long and 1.8 m in diameter. It is reportedly based on the RS-24 Yars ICBM, but its dimensions are also similar to the SLBM Bulava-30.10 It weighs 36,000 kg and carries an 800 kg nuclear warhead. It is currently unclear if the SS-X-31 carries a single warhead or multiple MIRVed warheads. Russia tested the missile with both payload configurations in 2013.