Spaceflight Insider

Soyuz MS-04 sends two-man crew on fast-track to ISS

Soyuz MS-04 launch

Soyuz MS-04 launches from Baikonur Cosmodrome in Kazakhstan. Liftoff took place at 3:13 a.m. EDT (07:13 GMT) April 20, 2017. Photo Credit: Aubrey Gemignani / NASA

The two newest International Space Station (ISS) inhabitants are on their way to the orbiting outpost. Soyuz MS-04 lifted off at 3:13 a.m. EDT (07:13 GMT) April 20, 2017, from the Baikonur Cosmodrome in Kazakhstan.

Expedition 51 crew members Jack Fischer, a NASA astronaut, and Fyodor Yurchikhin, a Russian cosmonaut, will join NASA astronaut Peggy Whitson, European Space Agency astronaut Thomas Pesquet, and Russian cosmonaut Oleg Novitskiy.

Expedition 51 crew launch

NASA astronaut Jack Fischer, top, and Russian cosmonaut Fyodor Yurchikhin wave goodbye before boarding the Soyuz spacecraft to take them to the International Space Station. Photo Credit: NASA

The Roscosmos State Corporation for Space Activities, better known as Roscosmos, is only sending two people inside the Soyuz instead of three. This was a result of a decision by the Russia to reduce the size of its station crew size from three per expedition to two in order to save money to launch a new module to the ISS – the decade-delayed Nauka science module.

The extra seat will afford already-in-space Whitson a three-month extension to her space stay. She will return to Earth with the Soyuz MS-04 crew in early September 2017, instead of early June, with Pesquet and Novitskiy in Soyuz MS-03.


Taking slightly more than 10 seconds between ignition and liftoff, the Soyuz-FG presented a ponderous sight as its five engines – one RD-108A in the core, and a single RD-107A engine in each of the four liquid-fueled boosters – spooled-up to flight speed.

Once the engines passed health checks, the launch mounts released the rocket, allowing it to lift off from launch pad 1/5 – the same pad Yuri Gagarin flew into space from in 1961.

The launcher was pushed skyward by a combined 933,000 pounds-force (4,100 kilonewtons) of sea-level thrust from the five engines. Just short of two minutes into the flight, the launch escape system (LES) was jettisoned.

Designed to rapidly pull the crewed spacecraft away from a stricken rocket in the event of a catastrophic failure, the LES is discarded once it can no longer be used.

Not long after jettisoning the LES, the four strap-on boosters consumed their supply of highly refined kerosene (RP-1) and liquid oxygen (LOX) propellant and separated from the still-firing core stage.

The four boosters, now independent from the rest of the launch vehicle, appeared to form a cross as they performed a flipping and tumbling maneuver during their free-fall to the ground below. This aerial display is called the Korolev Cross in homage to Sergei Korolev, the inventor of the R-7 rocket – a precursor to the Soyuz booster.

Hot staging

At an altitude of 48 miles (78 kilometers) and above most of the atmosphere, the protective aerodynamic shroud covering the Soyuz spacecraft was no longer needed. Splitting in half along its length, the fairing separated from the launch vehicle and exposed the spacecraft to the harsh near-space environment.

The core stage’s RD-108A engine continued to fire, pushing the rocket and its crewed payload to an altitude of 95 miles (153 kilometers) and a velocity of 8,500 mph (13,600 km/h).

The Soyuz’s second stage (or third, depending on how the boosters are classified) began to fire its RD-0110 while still attached to the core stage – an operation known as “hot staging” – and separated approximately 4 minutes, 45 seconds into flight.

Hot staging negates the need for separation motors in the core stage, thus decreasing the complexity of the staging process. It has been a mainstay of much of the Russian spaceflight industry for 60 years.

Express route to the ISS

The upper stage’s RD-0110 burned for approximately four minutes, placing the Soyuz MS-04 spacecraft on a trajectory to reach the ISS a scant six hours after leaving Kazakhstan. In the past, Soyuz spacecraft have taken upward of two days to reach the orbiting laboratory.

Shortening the rendezvous profile to six hours – just four orbits around Earth – not only offers the benefit of getting a crew to the station more quickly but also helps conserve the spacecraft’s limited supply of consumables, such as fuel and oxygen.

With only a four-day supply of those consumables aboard the spacecraft, the expedited rendezvous and docking process gives extra margin in the event of an emergency.

Soyuz MS-04 is scheduled to dock with the International Space Station’s Poisk module at 9:23 a.m. EDT (13:23 GMT) and will be carried live on NASA TV. That will be followed by the opening of the hatches between the spacecraft and ISS at 11:05 a.m. EDT (15:05 GMT).

Soyuz MS-04

Soyuz-FG / MS-04 launch. Photo Credit: Aubrey Gemignani / NASA


Soyuz MS-04 launch

Soyuz-FG / MS-04 launch. Photo Credit: Aubrey Gemignani / NASA


Soyuz MS-04 launch

Soyuz-FG / MS-04 launch. Photo Credit: Aubrey Gemignani / NASA


Soyuz MS-04 launch

Soyuz-FG / MS-04 launch. Photo Credit: Roscosmos


Video courtesy of NASA


Video courtesy of Телестудия Роскосмоса (Roscosmos TV)



Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

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