Loading

RU

ISS EXPRESS

From two-day to ultra-short flights

In 2020, the Russian spacecraft Soyuz MS-17 docked with the ISS, having performed the first ever ultra-short two-orbit rendezvous. It used to take up to two days to chase down the ISS, but this record-breaking flight took just 3 hours 3 minutes. We investigate how Roscosmos achieved this breakthrough, and whether future astronauts and cosmonauts will soon be able to fly to the ISS faster than some people on Earth get to work.
RU
In 2020, the Russian spacecraft Soyuz MS-17 docked with the ISS, having performed the first ever ultra-short two-orbit rendezvous. It used to take up to two days to chase down the ISS, but this record-breaking flight took just 3 hours 3 minutes. We investigate how Roscosmos achieved this breakthrough, and whether future astronauts and cosmonauts will soon be able to fly to the ISS faster than some people on Earth get to work.

HOW FAR IS IT TO THE ISS?

Poyekhali!
"Let's go!" — Gagarin's last words before lift-off.

On April 12, 1961, at 09:07 Moscow time, the Soviet spacecraft Vostok 1 lifted off for the first time from the Tyuratam missile test range (now the Baikonur Cosmodrome) in Kazakhstan with a person on board. After 108 minutes of flight and one loop in near-Earth orbit, it successfully returned to terra firma, ushering in a new era of crewed spaceflight and making Yuri Gagarin a household name ever since.

the maximum altitude of the first crewed spaceflight

The Vostok 1 spacecraft ascended roughly 85 km higher than planned.

The Soviet Union’s triumph could hardly fail to elicit a response from its main space race rival, the United States. The Americans had already declared their intention to be first to send a human being into space under Project Mercury, their supposed revenge for Sputnik 1. Less than a month after Gagarin's flight, astronaut Alan Shepard crossed the Kármán line (the notional boundary at which outer space begins), without, however, going into orbit. The World Air Sports Federation recognized this 15-minute ride as a spaceflight, but most often the title of first US astronaut is given to John Glenn. On February 20, 1962, Glenn orbited Earth three times.

Shepard's flight was more like a space-hop. The launch vehicle left Earth's atmosphere, but did not attain the first cosmic velocity (7.9 km/s), meaning that the craft could not be put into orbit. As a result, it re-entered the atmosphere just a few minutes after engine cut-off. Such flights are called suborbital. There have been relatively few crewed suborbital missions. For 60 years, orbital flights have been the mainstay of human space travel.

SPACEFLIGHT CLASSIFICATION
SPACEFLIGHT CLASSIFICATION

Orbit of habitation

Like any celestial body, our planet has a gravitational field and orbital paths around it. In Earth’s case, these are occupied by artificial satellites (ranging from spacecraft and research vehicles to space debris). In terms of altitude, orbits come in three flavors: low-Earth, medium-Earth, and high-Earth.

The boundaries of low-Earth orbit begin and end at approximately 200 km and 2,000 km, respectively, above Earth's surface. Compared to the next category, medium-Earth orbit, this section of space is narrow, yet, as the nearest to us, it is also the busiest. Orbiting here are observation and reconnaissance satellites: their proximity to Earth makes it possible to obtain highly accurate images of terrestrial objects. Many communications satellites are also low-orbiting — telecoms companies often launch so-called satellite constellations to achieve greater coverage. Last but not least, there are people. To date, all human spaceflights, with the exception of the Moon landings, have been in low-Earth orbit.

ORBIT CLASSIFICATION BY ALTITUDE
ORBIT CLASSIFICATION BY ALTITUDE

The highest-ever piloted spaceflight in low-Earth orbit was made in 1966 by the crew of Gemini 11. On its 26th orbit of Earth, the spacecraft climbed to an altitude of 1,370 km. To this day, the only space program ever to go beyond near-Earth space is the Apollo lunar mission.

Interplanetary travel (including to the Moon) is one of the key goals that spurred the development of crewed space exploration. Another was long-term stays aboard orbital stations. For more than 20 years, humankind’s main abode in low-Earth orbit has been the International Space Station. It was preceded by the Soviet/Russian Salyut, Almaz and Mir and the US Skylab stations.

Today's "satellite city" floats at an altitude of approximately 420 km above Earth's surface, a stone's throw away in cosmic terms. Hard to believe, perhaps, given the early space race predictions, that humankind has set up base so close to home and barely moved on in the past 60 years.

...If we need total weightlessness to conduct experiments, there is no point in flying far. But in terms of further development, we must look beyond the limits of low-Earth orbit

SERGEI KRIKALEV, Executive Director for Crewed Space Programs, Roscosmos State Corporation

...If we need total weightlessness to conduct experiments, there is no point in flying far. But in terms of further development, we must look beyond the limits of low-Earth orbit

From Earth to the ISS

The ISS is the most expensive science project in history and the largest human-made satellite. Construction began in 1998 as part of a collaboration between the Russian, US, Canadian, Japanese and European space agencies. The first crew, consisting of Russian cosmonauts Sergei Krikalev and Yuri Gidzenko and US astronaut William Shepherd, arrived on the ISS at the end of 2000, since when international teams have kept the station permanently occupied. There are two main mission control centers: one in the city of Korolyov, Moscow Region, responsible for the Russian Orbital Segment; the other in Houston, Texas, responsible for the US Orbital Segment. At the same time, the European Space Agency's mission control center in Oberpfaffenhofen, Germany, supports the Columbus space laboratory, and the Japanese Experiment Module, known as Kibō, is run from the Tsukuba Space Center (50 km from central Tokyo).

The crew of the first long-duration stay was delivered to the ISS by the Russian ship Soyuz TM-31. Later, together with the Soyuz fleet, the reusable vehicles of the US Space Shuttle program handled crew rotation. In 2003, after the Columbia disaster, Space Shuttle flights were suspended until mid-2005. Then, in 2011, when NASA finally wound up the Space Shuttle program, Soyuz became the only carrier of astronauts and cosmonauts to the ISS. This state of affairs lasted nine years, until Dragon 2 (also known as Crew Dragon), built by the private US company SpaceX, made its crewed flight. On May 31, 2020, Elon Musk successfully delivered astronauts Douglas Hurley and Bob Behnken to the ISS.

Today, uncrewed space flights to the station are carried out by four cargo ships: Russia's Progress, Japan's H-II Transfer Vehicle (HTV) and America's Dragon and Cygnus. From 2008 to 2014, the European Space Agency's Automated Transfer Vehicle (ATV) also flew to the station. The spacecraft deliver cargo and equipment necessary for the operation of the ISS, scientific experiments and the sustainability of the crew.

The limits of possibility

The ISS is unique. Among its many features is its variable altitude. The impact of the upper layers of Earth's atmosphere slows down the station, gradually reducing its orbit. Proximity to the planet also affects the period of rotation around it; the ISS encircles Earth in approximately 90 minutes.

Therefore, the station does not use the Sun as a time reference point.

To prepare for docking a spacecraft with the ISS, the station's orbit is adjusted. By firing the engines of the already docked Progress craft, the ISS is "raised" by several hundred meters. Often, its orbit is altered to avoid collision with space debris, as this can easily puncture the skin of the modules.

Wouldn't it be better to boost the ISS even higher? No, because in calculating the station's orbit several important restrictions need to be taken into account. First, the ISS can go no higher than 500 km — beyond this mark the radiation level rises significantly and would pose a risk to the crew. Second, the orbital altitude depends on the technical capabilities of the spacecraft delivering the crew; the Soyuz ships are designed for flights of up to 460 km high. During the Space Shuttle era, for example, the ISS was at an altitude of around 350 km, since the shuttles simply couldn't fly any higher. Lastly, launching a rocket is not cheap, and the ISS needs regular supplies of equipment. The higher the station, the less cargo can be delivered, and this would necessitate more flights. There is no squaring this vicious circle.

At present, the optimal altitude is slightly over 400 km. Incidentally, back on Earth, that is the distance that separates the Russian cities of Moscow and Smolensk. This can be covered in one hour by plane, in four hours by high-speed train, and in five hours by car. But for astronauts and cosmonauts, the journey to the ISS until recently took up to two days. Given the speed at which spacecraft travel, one might think this distance could be covered in a minute, but in reality that is not quite the case.

RENDEZVOUS IN ORBIT

Feeling the need...

Three, two, one, lift-off! Ignition, a flash of flame, and the launch vehicle rises heavenwards. A few minutes later, the rocket jettisons its lower stages and sends the payload craft on its space odyssey, the final destination being the ISS. And while it might seem that once the spacecraft is in orbit the hard part is over, the work for mission control is only just beginning, because docking with the ISS lies ahead.

It is impossible to imagine how the ISS would operate without docking technology, yet spacecraft rendezvousing was performed long before the appearance of orbital stations. In the past, the two ships were simply "fired" at each other. It went as follows: one craft was launched, the other a day later from the same launch pad at the precise moment when the first was passing overhead. Because the distance between them was short, the first dockings were lightning fast. The record time belongs to the Soviet Union.

the time between launch and docking of the uncrewed vehicles Kosmos 212 and Kosmos 213 in 1968

The silver medal goes to NASA: two years earlier, Gemini 11 docked with the Agena rocket in 94 minutes.

At the dawn of the era of flights to orbital stations, the Soviets mastered one-day rendezvous missions. Technically they were sound, but took a toll on the cosmonauts. After 24 hours, the acute phase of adaptation to weightlessness sets in, coordination deteriorates, and the risk of failure in the event of having to switch to manual docking increases. Hence, it was safer to perform the docking procedure on the second or third day, when the peak of space sickness had passed. Since 1986, when the Mir station was launched, a two-day scheme has been in operation. This approach was later inherited by the ISS.

Under the two-day scheme the ship makes 34 rotations around Earth, during which it must ascend from its lower trajectory to the ISS orbit and commence the approach. But this is complicated by the fact that all this time the station has been moving along at its own speed. Therefore, mission control calculates a special set of maneuvers to allow the spacecraft to "catch up" with the ISS. During the flight the cosmonauts inevitably have to deal with "deaf orbits" — when the spacecraft is out of contact with mission control for several hours. For this reason, no important operations are performed during these periods, and the crew rests or sleeps.

The docking itself takes place during the 34th orbit. Although the maneuver is computer-controlled, should an unforeseen circumstance arise, the ship's commander takes over. Manual docking requires some additional actions. For example, the crew must wait for the right light conditions, so that the Sun does not shine in their eyes during docking.

The station is not a small target ship [for training purposes]. It is impossible to dock [with the ISS] in 94 minutes, especially given its international status. We must observe all the laws, the main one being to fly slowly

RAFAIL MURTAZIN, Head of Ballistics, Energia Rocket and Space Corporation (RSC Energia)

The station is not a small target ship [for training purposes]. It is impossible to dock [with the ISS] in 94 minutes, especially given its international status. We must observe all the laws, the main one being to fly slowly

While two-day flights are no particular problem for Progress cargo ships, these 50 hours are a real endurance test for Soyuz crews. For all its merits, Soyuz is quite a cramped spacecraft. It offers the crew minimal comfort during the main operations: launching, maneuvers and docking.

During "deaf orbits" two people rest in the habitation module, the commander remains in the descent vehicle, and the ship itself points towards the Sun in "spin" mode to recharge its batteries. This is good for the ship's systems, which get topped up with solar energy, but less so for those in the habitation module, whose vestibular organs suffer all the effects of the spinning and twisting.

the available space per crew member in the descent vehicle of the Soyuz spacecraft

Including the habitation module, the available space per person is 1.2 m3.

...the need for speed

To cope with the heavy physical loads in space, cosmonauts receive extensive pre-flight training. The same cannot be said for space tourists, who spend far less time on such preparation. "Now I knew why we had those dreaded spinning chair trainings," Anousheh Ansari, an Iranian-American who flew to the ISS in 2006 on a space tourism program, wrote in her blog. For Ansari, 34 orbits were tough going. The initial euphoria quickly gave way to space sickness. Aboard the ISS, she needed another day to recover from the flight.

I basically became a mummy from that point forward. I only did very small slow movements and even that would make me feel really sick…

ANOUSHEH ANSARI, the first female tourist in space

I basically became a mummy from that point forward. I only did very small slow movements and even that would make me feel really sick…

After this incident, RSC Energia thought about how to make life easier for the crew. According to the medics, the state of euphoria induced by zero-gravity flight passes on the fifth or sixth orbit; plus it is easier to cope with space sickness in the more comfortable conditions aboard the ISS. Thus, the ballistics experts decided that the ship should dock before entering the passive "deaf zone," which begins immediately after the fifth revolution. At first, they developed a five-orbit scheme, but, due to various characteristics of the control system, it was impossible to test on the Progress vehicles. The only feasible short-scheme option turned out to be four orbits.

To implement the plan, RSC Energia came up with a revolutionary (quite literally) approach. Previously, to move a spacecraft from the insertion orbit to the intermediate, so-called phasing orbit, the vehicle spent a whole revolution carrying out measurements and calculations required for the maneuver. Henceforth, the preliminary calculations were carried out on Earth, allowing the spacecraft to enter the phasing orbit immediately after launch. Subsequent revolutions were spent measuring the orbit and fixing insertion errors by means of corrective burns — the Soyuz-FG launch vehicle, with its analogue control system, always put crewed vehicles into orbit with a large degree of error. The spacecraft then made an autonomous rendezvous with the ISS on the fourth orbit.

34-ORBIT SCHEME FOR FLIGHTS TO THE ISS
LOW-EARTH ORBIT COELLIPTIC ORBIT PHASING ORBIT ISS ORBIT EARTH ISS SOYUZ DOCKING OF SOYUZ WITH THE ISS
4-ORBIT SCHEME FOR FLIGHTS TO THE ISS
LOW-EARTH ORBIT COELLIPTIC ORBIT PHASING ORBIT ISS ORBIT EARTH ISS SOYUZ EARTH DOCKING OF SOYUZ WITH THE ISS

That is how the four-orbit scheme came about. It reduced the flight time to six hours, while preserving the option to switch to the usual two-day scheme in the event of an unforeseen circumstance. The short-flight scheme was tested on the Progress vehicles in 2012 and 2013. After three successful attempts on these cargo carriers, it was decided to test it on Soyuz itself. In March 2013, Roscosmos cosmonauts Pavel Vinogradov and Alexander Misurkin and NASA astronaut Christopher Cassidy reached the ISS in a then-record six hours. After the switch to the new Soyuz MS spacecraft, crewed short-scheme flights effectively became routine.

The nature of the work changed, but it didn't become twice as hard. The key is precision. [The scheme] is easily doable for well-trained crews, and all our crews are well-trained.

PAVEL VINOGRADOV, commander of the Soyuz TMA-08M crew that executed the four-orbit scheme

The nature of the work changed, but it didn't become twice as hard. The key is precision. [The scheme] is easily doable for well-trained crews, and all our crews are well-trained.

Ballistic curling

Yet ultra-short flights to the station were no panacea. True, the flight time decreased, but the cosmonauts' working hours grew longer. There were no more "deaf orbits," which, under the two-day scheme, gave the crew time to rest. Now, in the interval between breakfasting and docking, there lay 16-18 hours of duty, 11 of them in spacesuits. As the medics pointed out, the crew was still arriving at the ISS tired. The ballistics experts scratched their heads once more. This time they proposed reducing the flight time from six hours to three.

With the introduction of the Soyuz 2.1 rocket, the ultra-short two-orbit rendezvous scheme developed in 2016 became possible. Unlike the previous Soyuz-FG, the new carrier is equipped with a digital control system, which allows spacecraft to be put into orbit with precision. The flight begins using the same principle as the four-orbit method, but thanks to the accuracy of the rocket, no corrective maneuvers are required. The new scheme saves two propulsive burns and three hours.

The two-orbit flight simplifies the job of the cosmonauts: fewer operations, fewer switch-ons of the Soyuz engine. The ballistics team, on the other hand, has to cope with more tasks. The key parameter when it comes to docking with the station is the phase angle (the angle between the ship and the target in the orbit plane). The spacecraft and the ISS must both be at a certain angle at the moment of orbit insertion. The shorter the flight time, the smaller the phase range (the allowable phase angles at which docking is possible). For comparison, the phase ranges of the two-day, four-orbit and two-orbit schemes are, respectively, 150, 22 and 6 degrees. Under the two-orbit scheme, it is harder to "catch" the station; if something goes wrong, the ship has to be relaunched the following day, this time using the two-day scheme.

2-ORBIT SCHEME FOR FLIGHTS TO THE ISS
LOW-EARTH ORBIT ISS ORBIT EARTH ISS SOYUZ EARTH DOCKING OF SOYUZ WITH THE ISS

On top of everything else, the station is descending daily. Therefore, to ensure the exact phase conditions at the time of launch, RSC Energia and mission control prescribe corrective maneuvers to maintain the altitude of the ISS orbit for months ahead. The developer of the short-flight scheme, Rafail Murtazin, describes this approach as "ballistic curling." For those unfamiliar with curling, the game involves sliding stones on ice toward a target area; likewise, the aim of short flights is to "slide" the orbital station into position for a fast docking. Under the metaphor, ISS orbit corrections are like stones in curling. In the game, players use stones to guard the "house" (target area); up in outer space, ISS orbit corrections are used to "guard" the insertion phase. If, prior to launch, the ISS orbit needs to be corrected to evade space debris, the ballistics team can sacrifice one of its "stones." What's more, this does not require additional fuel expenditure on the part of the station.

I consider the two-orbit scheme to be easier on the bodily organs. <...> In essence, the work is no different, only it's done without breaks, more compactly and dynamically

SERGEY RYZHIKOV, commander of the Soyuz MS-17 crew that executed the two-orbit scheme

I consider the two-orbit scheme to be easier on the bodily organs. <...> In essence, the work is no different, only it's done without breaks, more compactly and dynamically

Reducing the load on the cosmonauts is not the only advantage of the ultra-short scheme. The new method significantly improves the ship's fuel consumption. According to the ballistics experts, the two-orbit scheme saves Soyuz approximately 30 kg of fuel, since none is expended on reorientation maneuvers and additional revolutions. Fuel is never a luxury: the more that remains in the spacecraft's tanks, the safer and more reliable the flight. For example, reserve fuel allows for a second docking attempt in the event of a mishap first time around.

The first tests of the two-orbit scheme on the Progress vehicles in 2017 and early 2018 failed. Following further technical issues, the cargo carriers were eventually launched on the backup date using the two-day scheme. This launch was performed successfully in July 2018: Progress MS-09 reached the ISS in 3 hours 40 minutes. After five trouble-free flights, it was decided to test the ultra-short scheme on a crewed spacecraft.

HOW LONG DOES IT TAKE TO FLY TO THE ISS
HOW LONG DOES IT TAKE TO FLY TO THE ISS

Soyuz's first ever ultra-fast flight to the ISS took place on October 14, 2020. Russian cosmonauts Sergey Ryzhikov and Sergey Kud-Sverchkov and NASA astronaut Kathleen Rubins flew to the station in a record 3 hours 3 minutes. The Soyuz 2.1a rocket was launched from the Baikonur Cosmodrome at 08:45 Moscow time, and by 11:48 Moscow time the Soyuz MS-17 spacecraft, carried inside the rocket, had made a routine docking with the Rassvet module of the Russian segment of the ISS.

3 hours 3 minutes halves the previous record. Russians live in the fast lane, as we say. We believe this [ultra-short scheme] can still be improved.

DMITRY ROGOZIN, Director General, Roscosmos State Corporation

3 hours 3 minutes halves the previous record. Russians live in the fast lane, as we say. We believe this [ultra-short scheme] can still be improved.

To fully test the new scheme, Roscosmos conducted two crewed flights in 2021. The first one took place on April 9. The Soyuz MS-18 (also known as Yu.A. Gagarin) spacecraft reached the ISS in roughly 3.5 hours. On October 5, the Soyuz MS-19 spacecraft brought to the station cosmonaut Anton Shkaplerov, actress Yulia Peresild and director Klim Shipenko, who will shoot the first ever feature film in space. All this time the Progress vehicles were being launched under the two-day scheme so as to focus all efforts on ensuring the right phase for the Soyuz ships.

Sergey Kud-Sverchkov, whose two-orbit flight to the ISS in the fall of 2020 was his first ever lift-off into space, says that he endured the acute stage of space sickness when already aboard the station. "Rookies like me are prepared in advance. We know how to behave the first time in zero gravity: move smoothly, no rushing. Your work capacity decreases, of course, but it's still possible to do all your assigned tasks," he said.

When all the tests are done, flights to the ISS will be faster than getting from A to B back on Earth. But for some there is no limit to perfection. And so the ballistics department of RSC Energia developed an even shorter rendezvous scheme — in one orbit.

INTO THE FUTURE IN ONE ORBIT

Even faster

In April 2021, Roscosmos head Dmitry Rogozin announced that a single-orbit flight scheme could be tested on the Progress vehicles as early as 2022. The concept was developed by RSC Energia in 2019. Experts calculate that the new scheme will allow a spacecraft to rendezvous with the ISS in about two hours.

After launch, it is planned that the spacecraft will make two propulsive burns to put it into a coelliptic orbit that is geometrically similar to that of the ISS. This means that at each point the difference in altitude between the orbits will be the same. When the observation angle between the station and the spacecraft equals 23 degrees, a third burn will propel the vehicle toward the ISS for docking. But to implement the scheme, one more element is required: quasi-coplanar insertion.

1-ORBIT SCHEME FOR FLIGHTS TO THE ISS
COELLIPTIC ORBIT ISS ORBIT EARTH ISS SOYUZ EARTH DOCKING OF SOYUZ WITH THE ISS

As previously noted, the main factor determining the duration of the rendezvous between the spacecraft and the ISS is the phase angle between them at the moment of launch. And here arises the main difficulty: for a single-orbit flight, the phase range must be 0.5 degrees. For comparison, under the two-orbit scheme the value is 6 degrees.

Just imagine the precision required! It's impossible, it's the eye of a needle. What's the solution, don't fly? No, there's a technique called quasi-coplanar insertion.

RAFAIL MURTAZIN, Head of Ballistics, RSC Energia

Just imagine the precision required! It's impossible, it's the eye of a needle. What's the solution, don't fly? No, there's a technique called quasi-coplanar insertion.

When launching from Baikonur, quasi-coplanar insertion helps to increase the phase range by up to 20 degrees (improving the chances of "catching" the station). Essentially, this method works by inserting the spacecraft into an orbit with an inclination that differs from the inclination angle of the ISS orbit to the equator (51.66 degrees). Thus, after launch, the spacecraft and the station find themselves in different planes. To correct this, the spacecraft must perform an additional maneuver. According to Murtazin, the Soyuz 2.1a launch vehicle is technically capable of implementing the single-orbit scheme.

The single-orbit rendezvous scheme with quasi-coplanar insertion will be more effective for launches from the Vostochny Cosmodrome, which is located in the Amur Region in the Russian Far East. Baikonur is located at a latitude of 46.5 degrees, and Vostochny at 51.7, which is closer to the orbital inclination angle of the ISS. Thanks to quasi-coplanar insertion, a phase range of approximately 100 degrees can be achieved at Vostochny. This will allow launches to be carried out almost daily.

At present, all crewed missions are launched from Baikonur. But work on a second launch pad at Vostochny for the Angara launch vehicle is underway. So crewed missions launched from the Russian Far East will soon be a reality.

Back to the future

Aerospace engineers have more than a sporting interest in the single-orbit scheme. Ultra-fast flights are necessary for other space programs, too, in particular lunar ones.

The talk is now of single-orbit flights. Why? For a start, we'll knock 1.5 hours off the flight time. But it's not simply about wanting to travel fast; the main thing is what the future holds. And the future belongs to lunar programs.

RAFAIL MURTAZIN, Head of Ballistics, RSC Energia

The talk is now of single-orbit flights. Why? For a start, we'll knock 1.5 hours off the flight time. But it's not simply about wanting to travel fast; the main thing is what the future holds. And the future belongs to lunar programs.

In the 1960s, the USSR and the US both developed docking technologies specifically for crewed flights to the Moon. It was this that made possible the Moon landings under the Apollo program. In one loop, the special lightweight module with the crew prepared for landing on the Moon's surface and, in one loop, returned to the spacecraft, which was waiting patiently in lunar orbit. According to Murtazin, this scheme is relevant for modern programs as well.

The Apollo spacecraft were carried beyond near-Earth space by the Saturn V super-heavy rocket. Today, Russia is developing the super-heavy Yenisei, which is set to become the main launch vehicle for the second stage of the Russian lunar program, which provides for crewed missions. But before it appears, the task can be accomplished using Angara and motherships to be assembled in orbit. Here, too, there is no doing without single-orbit flights.

To deliver a crewed spacecraft to the Moon, it must be docked in low-Earth orbit with an oxygen-hydrogen upper stage, which is launched separately. The docking has to take place in the shortest possible time.

the maximum time the oxygen-hydrogen upper stage can survive in orbit

As it heats up, it loses efficiency.

the maximum time the oxygen-hydrogen upper stage can survive in orbit

As it heats up, it loses efficiency.

Every minute is vital, so the single-orbit scheme is just what is needed. It is additionally planned that, having docked with the upper stage, the spacecraft will make one more orbit of Earth to check all systems and, if everything is in order, head for the Moon.

Such double launches of spacecraft and upper stages will become viable after the second launch pad for Angara is put into operation at Vostochny.

The sky's not the limit

As already mentioned, ultra-fast flights to the ISS were conceived primarily to improve the well-being of the crew by reducing the time spent inside the cramped spacecraft. Moreover, the ship saves fuel and reduces battery consumption, which improves all-round safety. But these are not all the benefits. Short-scheme flights, especially single-orbit ones, open up additional possibilities.

Thanks to such schemes, the working day is reduced not only in orbit, but also back on Earth. During launch under the traditional two-day scheme, mission control works almost 72 hours non-stop. Short-scheme flights significantly relieve the burden on ground staff, who gratefully noted the difference when two-orbit ones were introduced.

What's more, short schemes will be required in case of rescue operations in space or emergency situations aboard the ISS. Assistance from Earth will be able to get there faster, and when human lives are at stake, every second counts.

Another advantage of these schemes is the express delivery to the station of biomaterials for scientific experiments. Work aboard the ISS in this direction is ongoing: over the 22 years of its existence, crew members have conducted more than 2,000 experiments, most of them in the fields of biology and biotechnology. For example, the cultivation of complex protein structures. The pre-experiment preparations are carried out in special laboratories at Baikonur, and the necessary components are packed into the spacecraft 2–3 hours before blast-off. It is important for biologists that the delivery time to the ISS be as short as possible.

We conduct unique experiments on the ISS <...> So it's great to be able to fly there fast. It's a tremendous victory for our scientists.

PAVEL VINOGRADOV, commander of the Soyuz TMA-08M crew that executed the four-orbit scheme

We conduct unique experiments on the ISS <...> So it's great to be able to fly there fast. It's a tremendous victory for our scientists.

Short-scheme flights will also make space more accessible to tourists: it will be physically easier for them to endure the trip to the ISS.

As more than half a century of space exploration shows, docking technologies are crucial and always will be: flights to the ISS and future stations, as well as interplanetary missions, will depend on them. Short-scheme flights, then, are set to be the beating heart of the new Space Age.