Russian Progress M-25M docks with the ISS
A Russian Soyuz 2-1A rocket lofted the latest Progress resupply vehicle (M-25M) for a fast rendezvous trip to the International Space Station (ISS). The launch of the Progress – riding on a Soyuz 2-1A for the first time – occurred at 07:09 GMT on Wednesday from the Baikonur Cosmodrome in Kazakhstan, ahead of a six hour trip to the orbital outpost.
Russia’s Soyuz-2-1A rocket was used to launch the resupply vehicle for the first time, taking over from the Soyuz-U.
The 2-1 version of the world famous rocket first flew in November 2004. Derived from the earlier Soyuz-U and the Soyuz 11A511 before that, the rocket was intended as an eventual replacement for all of the Soyuz and Molniya variants then in service.
The Molniya-M was retired from service in 2010 and the Soyuz-2 has already replaced the Soyuz-U for all launches apart from Progress missions to the International Space Station. That was until Wednesday’s mission.
The Soyuz-2 has three principal variants; the 2-1a, 2-1b and 2-1v (v being the Romanisation of the third letter of the Cyrillic alphabet). The 2-1a is a modernised version of the Soyuz-U, while the 2-1b introduces a new RD-0124 stage engine.
The Soyuz-2-1v, which is also known as Soyuz-1, uses an NK-33 engine to power the core stage and does away with the four boosters flown on all other Soyuz rockets.
The first and second stages of the Soyuz-2-1a burn in parallel; the first stage consists of four strap-on boosters powered by RD-117 engines, clustered around the core, or second stage, which is powered by an RD-118.
Atop the core sits the third stage with an RD-0124 engine that injected the Progress spacecraft into its target orbit.
The RD-0124 is used as a second stage in Soyuz-2.1v, but on Soyuz-2.1b it is on the third stage.
Once orbital insertion was achieved, the race to hook up with the ISS, in just six hours, requires the first of two engine burns on the vehicle’s initial orbit of the Earth. The requirements were already onboard the Progress’ computers.
With all going to plan, the second orbit required the help of ground controllers, with actual orbital parameters uplinked from a Russian Ground Site (RGS), allowing for a further eight rendezvous burns to be performed over the next five hours of flight.
This fast rendezvous technique has been successfully employed on a number of Progress and Soyuz flights lately.
However, there was a problem during the “Dv3” burn on the Soyuz TMA-12 mission – which resulted in mission controllers opting to move to a new flight profile that allowed for Soyuz to arrive in the previously used two day rendezvous profile.
It was later revealed by sources that the 24 second DV3 burn did not occur due to an attitude problem with the Soyuz that lofted it into orbit – an error of just one degree.
This was apparently related to an over-performance of the Soyuz FG rocket – resulting in Soyuz being in a higher orbit that planned. As such, the TMA-12M’s flight computer provided an automated “no burn” command, due to the incorrect attitude of the vehicle.
Controllers opted to move to the back up plan of a two day rendezvous, with all burns relating to this flight profile conducted without issue. The Soyuz – with its three member crew – successfully docked with the MRM-2 port two days later.
For Progress M-25M’s arrival, the usual requirement of bidding farewell to a previously docked Progress was conducted earlier this week.
Progress M-24M undocked on Monday and will undergo three weeks of engineering tests in orbit before being commanded to reenter Earth’s atmosphere, where it will burn up over the Pacific Ocean.
The latest Progress sports an increased cargo manifest, afforded to it via the additional power of the Soyuz 2-1A.
Although this is not the primary reason for switching to the Soyuz 2-1A, an extra 400 kg can be lofted via this new partnership, although not all of that additional margin has been taken advantage of with Progress M-25M as such an increase would likely require design changes to the Progress.
The cargo ship’s manifest includes 1,300 kg of dry cargo, 420 kg of water in the Rodnik tanks, 880 kg mid- section propellent and 250 kg of PAO propellant for the ISS.
Progress M-25M dock with the space station’s Pirs docking compartment exactly six hours after lift-off.