The R-29RMU2.1 Lajner (Russian: Р-29РМУ2.1 "Лайнер" meaning Liner as in airliner or ocean liner) is a Russian liquid-fuelled submarine-launched ballistic missile (SLBM) and the newest member of the R-29 missile family, developed by the Makeyev Rocket Design Bureau and produced by the Krasnoyarsk Machine-Building Plant.
It was expected to enter service with the Russian Navy's Delta IV-class submarines after a successful test programme that spanned from May to September 2011.
On 9 August 2011, the Russian Ministry of Defense disclosed the details of the Lajner SLBM, whose first launch occurred on 20 May earlier that year.
[4] The second launch of the Lajner missile took place on 29 September 2011 from the submarine K-114 Tula in the Barents Sea aimed at the Kura Test Range.
[7] While it shares flight characteristics with the Sineva, the Lajner is equipped with improved systems to overcome anti-ballistic missile shields.