WASHINGTON — Russia plans to retire its Proton rocket, a heavy-lift workhorse with 50 years and 400 successful missions under its belt, in 2025, some four years after its replacement becomes operational, a top Russian industry official said.

Andrey Kalinovskiy, general director of Proton manufacturer Khrunichev State Research and Production Space Center, based in Moscow, said the Angara family of rockets, now in testing, will become operational in 2021 and fully replace Proton by 2025.

To date, the Khrunichev-built Angara has carried out two demonstration flights, a suborbital launch of the light variant of the rocket and a December 2014 flight of the heavy-lift Angara 5 that carried a dummy payload to geostationary orbit.

The next demonstration is slated for 2016 and also will feature the Angara 5, Kalinovskiy said during a press conference at the Satellite 2015 conference here.

Russia is looking for a commercial payload to fly on that mission, Kalinovskiy said. The Russian government will be responsible for finding the customer, he said, adding that it is too early to say whether the payload will be launched to low or geostationary orbit, the latter being the destination of most telecommunications satellites.

Ultimately, commercial Angara missions would be marketed by International Launch Services of Reston, Virginia, which currently arranges commercial launches aboard Proton.

Angara today can only operate out of the Plesetsk Cosmodrome, which because of its northern Russia location is not ideal for launching geostationary-orbiting satellites, said Phil Slack, president of ILS. Russia is developing an Angara launch site called Vostochny that has a more southern location and will become ILS’s new spaceport once Proton, which operates solely out of the Baikonur Cosmodrome in Kazakhstan, is retired, he said.

Kalinovskiy said the Russian and Kazakh governments are working on arrangements for the future of Baikonur, which also is the exclusive spaceport of Russia’s human spaceflight program.

The Angara family will have three basic variants: one with a single core stage; an intermediate version with three core stages bundled together; and the heavy-lift variant with five cores. The next launch of the light version of Angara is slated for 2017, Kalinovskiy said.