Today, many of us know, or at least have heard of, the private company SpaceX's family of partially reusable launch vehicles. Thanks to the success of the company, as well as the personality of the founder, Elon Musk, who himself often becomes the hero of news feeds, Falcon 9 rockets, SpaceX and space flights in general do not leave the pages of the international press. At the same time, Russia had and still has its own developments and no less interesting projects of reusable missiles, about which much less is known. The answer to the question why this is happening is obvious. Ilona Mask's rockets regularly fly into space, and reusable and partially reusable Russian rockets are so far only projects, drawings and beautiful pictures in presentations.
Space launches today
Nowadays, we can safely say that Roskosmos at some point missed the topic of reusable missiles, having in its hands developments and projects that were ahead of other countries by several years. All projects of Russian reusable missiles were never completed, not implemented in metal. For example, the reusable single-stage Korona launch vehicle, developed from 1992 to 2012, was never brought to its logical conclusion. We are already seeing the result of this miscalculation in development. Russia has seriously lost its position in the commercial space launch market with the advent of the American Falcon 9 rocket and its variants, and is also seriously inferior in terms of the number of space launches made per year. At the end of 2018, Roscosmos reported 20 space launches (one unsuccessful), while back in April 2018, in an interview with TASS, the head of Roscosmos Igor Komarov said that it is planned to carry out 30 space launches by the end of the year. The leader at the end of last year was China, which carried out 39 space launches (one unsuccessful), followed by the United States with 31 space launches (no unsuccessful ones).
Speaking about modern space flights, it is necessary to understand that in the total cost of launching a modern launch vehicle (LV), the main expense item is the rocket itself. Its body, fuel tanks, engines - all this flies away forever, burns up in the dense layers of the atmosphere, it is clear that such irretrievable expenses turn any launch of a launch vehicle into a very expensive pleasure. Not maintenance of spaceports, not fuel, not assembly work before launch, but the price of the launch vehicle itself is the main item of expenses. A very complex technological product of engineering thought is used for a few minutes, after which it is completely destroyed. Naturally, this is true for disposable rockets. The idea of using recoverable launch vehicles suggests itself here by itself, as a real chance to reduce the cost of each space launch. In this case, even the return of only the first stage makes the cost of each launch lower.
Landing of the returnable first stage of the Falcon 9 launch vehicle
It is a similar scheme that the American billionaire Elon Musk implemented, making the recoverable first stage of the heavy Falcon 9 launch vehicle. While the first stage of these missiles is partially recoverable, some landing attempts end in failure, but the number of failed landings dropped to almost zero in 2017 and 2018. For example, last year there was only one failure for every 10 successful landings of the first stage. At the same time, SpaceX also opened the new year with a successful landing of the first stage. On January 11, 2019, the first stage of the Falcon 9 rocket successfully landed on a floating platform, moreover, it was reused, and earlier it launched the Telestar 18V communications satellite into orbit in September 2018. Nowadays, such returnable first stages are already a fait accompli. But when the representatives of the American private space company only spoke about their project, many experts doubted the possibility of its successful implementation.
In the realities of today, the first stage of a heavy-class Falcon 9 rocket in some launches can be used in a reentry version. Taking the second stage of the rocket to a sufficient height, it separates from it at an altitude of about 70 kilometers, undocking occurs approximately 2.5 minutes after the launch of the launch vehicle (the time depends on the specific launch tasks). After separation from the LV, the first stage, using the installed attitude control system, performs a small maneuver, avoiding the flame of the working second stage engines, and turns the engines forward in preparation for the three main braking maneuvers. When landing, the first stage uses its own motors for braking. It is worth noting that the returned stage imposes its own restrictions on the launch. For example, the maximum payload of a Falcon 9 rocket is reduced by 30-40 percent. This is due to the need to reserve fuel for braking and subsequent landing, as well as the additional weight of the installed landing equipment (lattice rudders, landing supports, control system elements, etc.).
The successes of the Americans and a large series of successful launches did not go unnoticed in the world, which provoked a series of statements about the start of projects using partial reusability of rockets, including the return of side boosters and the first stage back to Earth. Representatives of Roscosmos also spoke on this score. The Company started talking about the resumption of work on the creation of reusable missiles in Russia at the beginning of 2017.
Launch vehicle "Korona" - general view
Reusable Korona rocket and earlier projects
It is worth noting that the idea of reusable missiles was studied back in the Soviet Union. After the collapse of the country, this topic did not disappear; work in this direction continued. They began much earlier than Elon Musk just spoke about it. For example, the blocks of the first stage of the super-heavy Soviet rocket Energia were supposed to be returned, this was necessary for economic reasons and for the implementation of the resource of the RD-170 engines, designed for at least 10 flights.
Less well known is the project of the Rossiyanka launch vehicle, which was developed by the specialists of the Academician V. P. Makeev State Rocket Center. This enterprise is mainly known for its military developments. For example, it was here that the majority of domestic ballistic missiles intended for arming submarines were created, including the R-29RMU Sineva ballistic missiles currently in service with the Russian submarine fleet.
According to the project, the Rossiyanka was a two-stage launch vehicle, the first stage of which was reusable. Essentially the same idea as the SpaceX engineers, but a few years earlier. The rocket was supposed to launch 21.5 tons of cargo into a low reference orbit - indicators close to the Falcon 9 rocket. The return of the first stage was to take place along a ballistic trajectory due to the re-inclusion of the standard stage engines. If necessary, the carrying capacity of the rocket could be increased to 35 tons. On December 12, the Makeyev SRC presented its new rocket at the Roscosmos competition for the development of reusable launch vehicles, but the order for the creation of such devices went to the competitors of the Khrunichev State Research and Production Space Center with the Baikal-Angara project. Most likely, the specialists of the Makeev SRC would have had the competence to implement their project, but without sufficient attention and funding it was impossible.
The Baikal-Angara project was even more ambitious; it was an aircraft version of the first stage return to Earth. It was planned that after reaching the set height of the compartment, a special wing would open at the first stage and then it would fly along an airplane with a landing at a conventional airfield with the landing gear extended. However, such a system itself is not only very complex, but also expensive. Her indisputable merits included the fact that she could return from a greater distance. Unfortunately, the project was never realized, it is still sometimes remembered, but nothing more.
Now the world is thinking about fully reusable launch vehicles. Elon Musk announced the Big Falcon Rocket project. Such a rocket should receive a two-stage architecture uncharacteristic for modern cosmonautics, its second stage is a single whole with a spacecraft, which can be both cargo and passenger. It is planned that the first stage of Superheavy will return back to Earth, performing a vertical landing at the cosmodrome through the use of its engines, this technology has already been perfectly developed by SpaceX engineers. The second stage of the rocket, together with a spacecraft (in fact, this is a spacecraft for various purposes), which was named Starship, will enter the Earth's orbit. The second stage will also have enough fuel left to decelerate in the dense layers of the atmosphere after completing a space mission and land on an offshore platform.
It is worth noting that SpaceX does not have a palm in such an idea either. In Russia, the project of a reusable launch vehicle has been developed since the 1990s. And again, they worked on the project at the State Rocket Center named after Academician V. P. Makeev. The project of the reusable Russian rocket has the beautiful name "Korona". Roscosmos remembered this project in 2017, followed by various comments on the renewal of this project. For example, in January 2018, Rossiyskaya Gazeta published the news that Russia had resumed work on a reusable space rocket. It was about the Korona launch vehicle.
Unlike the American Falcon-9 rocket, the Russian Korona has no detachable stages; in fact, it is a single soft takeoff and landing spacecraft. According to Vladimir Degtyar, General Designer of the Makeyev SRC, this project should open the way for the implementation of long-distance interplanetary manned flights. It is planned that the main structural material of the new Russian rocket will be carbon fiber. At the same time, the "Korona" is designed to launch spacecraft into low earth orbits with an altitude of 200 to 500 kilometers. The launch vehicle mass is about 300 tons. The mass of the output payload is from 7 to 12 tons. The takeoff and landing of the "Korona" should take place using simplified launch facilities, in addition to this, the option of launching a reusable rocket from offshore platforms is being worked out. The new launch vehicle will be able to use the same platform for takeoff and landing. The rocket preparation time for the next launch is only about a day.
It should be noted that carbon-fiber materials required to create single-stage and reusable rockets have been used in aerospace technology since the 90s of the last century. Since the beginning of the 1990s, the Korona project has come a long way of development and has evolved significantly, needless to say that initially it was about a disposable rocket. At the same time, in the process of evolution, the design of the future rocket became both simpler and more perfect. Gradually, the developers of the rocket abandoned the use of wings and external fuel tanks, having come to the understanding that the main material of the body of the reusable rocket would be precisely carbon fiber.
In the latest version of the reusable Korona rocket to date, its mass is approaching 280-290 tons. Such a large single-stage launch vehicle requires a highly efficient liquid-propellant rocket engine that runs on hydrogen and oxygen. Unlike rocket engines, which are placed on separate stages, such a liquid-propellant rocket engine should work effectively in various conditions and at different altitudes, including takeoff and flight outside the Earth's atmosphere. “An ordinary liquid-propellant rocket engine with Laval nozzles is effective only at certain altitude ranges,” say the Makeevka designers, “for this reason, we came to the need to use a wedge-air liquid engine on the rocket. The gas jet in such rocket engines adjusts itself to the pressure “overboard”; moreover, they retain their efficiency both at the surface of the Earth and quite high in the stratosphere.
RN "Korona" in orbital flight with a closed payload compartment, render
However, so far in the world there simply does not exist a working engine of this type, although they were actively developed in the USSR and the USA. Experts believe that the Korona reusable launch vehicle should be equipped with a modular version of the engine, in which the wedge-air nozzle is the only element that currently does not have a prototype and has not been tested in practice. At the same time, Russia has its own technologists in the production of modern composite materials and parts from them. Their development and application are quite successfully engaged, for example, in JSC "Kompozit" and the All-Russian Institute of Aviation Materials (VIAM).
For a safe flight in the Earth's atmosphere, the Korona's carbon-fiber structure will be protected by a heat-shielding tile, which was previously developed at VIAM for the Buran spacecraft and has since gone through a significant development path. “The main heat load on the Korona will be concentrated on its bow, where high-temperature thermal protection elements are used,” the designers note. “At the same time, the flared sides of the launch vehicle have a larger diameter and are located at an acute angle to the air flow. The thermal load on these elements is less, and this, in turn, allows us to use lighter materials. As a result, a saving of about 1.5 tons of weight is achieved. The mass of the high-temperature part of the rocket does not exceed 6 percent of the total mass of the thermal protection for the Korona. For comparison, the space shuttle shuttle accounted for more than 20 percent."
The sleek, tapered shape of the reusable rocket is the result of a lot of trial and error. According to the developers, while working on the project, they reviewed and evaluated hundreds of different options. “We decided to completely abandon the wings, like those of the Space Shuttle or on the Buran spacecraft,” the developers say. - By and large, when in the upper atmosphere, the wings only interfere with the spacecraft. Such spaceships enter the atmosphere at hypersonic speed no better than an "iron", and only at supersonic speed they switch to horizontal flight, after which they can fully rely on the aerodynamics of the wings."
The cone-shaped axisymmetric shape of the rocket allows not only to facilitate heat protection, but also to provide it with good aerodynamic qualities when moving at high flight speeds. Already in the upper atmosphere, the "Korona" receives a lifting force, which allows the rocket not only to slow down, but also to make maneuvers. This allows the launch vehicle to maneuver at a high altitude when flying to the landing site; in the future, it only has to complete the braking process, correct its course, turn aft downward using small maneuvering engines, and land on the ground.
The problem with the project is that Korona is still being developed in conditions of insufficient funding or its complete absence. Currently, the Makeyev SRC has completed only a draft design on this topic. According to the data announced during the XLII Academic Readings on Cosmonautics in 2018, feasibility studies were carried out on the project for the creation of the Korona launch vehicle and an effective rocket development schedule was drawn up. The necessary conditions for the creation of a new launch vehicle have been investigated and the prospects and results of both the development process and the future operation of the new rocket have been analyzed.
After the burst of news about the Korona project in 2017 and 2018, silence follows again … The prospects of the project and its implementation are still unclear. Meanwhile, SpaceX is going to present a test sample of its new reusable Big Falcon Rocket (BFR) in the summer of 2019. It may take many years from the creation of a test sample to a full-fledged rocket, which will confirm its reliability and performance, but for now we can state: Elon Musk and his company are making things that can be seen and touched by hands. At the same time, Roskosmos, according to Prime Minister Dmitry Medvedev, should end its projecting and chat about where we will fly in the future. You need to talk less and do more.
