Pictured: YaEDU nuclear engine
Source: https://www.roscosmos.ru/media/files/docs/2017/SpAsBus/sopov_vizionerstvo.pdf
Russia
Russia, along with the United States, remains the global leader in space nuclear reactor (SNR) technology, drawing on the experience of the Soviet Union’s extensive space reactor program. The Soviet Union’s first fission system for use in space was the 1964 Romashka fast reactor, which was not launched into orbit. It was the basis for the standardization of the BES-5 Buk reactor in 1971. The BES-5 was created to power the Soviet Union’s Radar Ocean Reconnaissance Satellite or RORSAT system known as US-A, which sought to monitor NATO and merchant vessels from low-earth orbit. The BES-5 was a fast reactor that used HEU enriched to 90% and a liquid metal coolant (NaK). The Soviets likely considered fast reactors because moderator materials used in power reactors may add mass and bulk, which is not desirable in a spacecraft. The reactor was designed to be ejected from the satellite into a disposal orbit at the end of its operational life in order to prevent the radioactive fuel from re-entering earth's atmosphere. But this system proved to be woefully flawed, and the BES-5 reactor was involved in multiple accidents, most notably the Kosmos 954 incident, which scattered radioactive debris over northern Canada, and the Kosmos 1402 incident, which occurred over the Atlantic Ocean. In the latter case, radioactive strontium in rain samples from Fayetteville, Arkansas in the months following the incident was determined to have come from the Kosmos 1402 core. [1] It was widely believed that either of these reentries would have resulted in a major radiological catastrophe if they had occurred over populated areas. [2]
The BES-5 was succeeded by the TOPAZ-1 reactors. They were more powerful than their predecessors, producing 150 kWt of power to the BES-5’s 100 kWt, while at the same time using only 11.5 kg of HEU compared to 30 kg in the BES-5. [3] The TOPAZ-1 used HEU enriched to 96%, while the BES-5 was 90%. Unlike the BES-5, however, the TOPAZ-1 was a thermal reactor with a hydrogen moderator, which enabled the reduction in HEU. In 1987, the TOPAZ-1 was onboard the Kosmos 1818 and Kosmos 1867 satellites, and unlike their predecessors they were launched into high-earth orbit. Kosmos 1818 began leaking its sodium-potassium coolant in the form of hazardous metallic spheres in 2008. [4] Kosmos 1867 began to do the same in 2014. [5] In total, the Soviet Union launched 35 SNRs – including 31 BES-5, 2 TOPAZ-1 and two other experimental reactors – before its collapse in 1991.
The collapse of the Soviet Union did not mean the end of Russia’s SNR development. The TOPAZ-2, which had been developed by the Soviet Union but not tested or launched due to a lack of funding, was purchased from Russia and shipped to Albuquerque, NM starting in 1992 as part of the TOPAZ International Program (TIP). The United States brought over Russian scientists and engineers to verify its reliability, presenting the only opportunity for Russian scientists to continue the development of thermionic space nuclear power systems for civil applications. [6] The TIP became the first prominent example of international cooperation between Russia and the United States in a formerly highly classified area of technology following the collapse of the Soviet Union. Notably, the TOPAZ-2 purchase was not intended as an assistance program; rather it allowed the United States to obtain advanced space nuclear power technology at a fraction of the cost of domestic development. [7] The TOPAZ-2 was the basis for the Nuclear Electric Propulsion Space Test Program (NEPSTP), an international development program. The Johns Hopkins University Applied Physics Laboratory designed a prototype spacecraft and testing program in 1993, but the spacecraft was never developed beyond the design phase. Funding for TIP was cut in 1996, resulting in the return to Russia of the scientists and the functioning TOPAZ-2 models.
Meanwhile, in 1993, Russia began development of the more powerful TOPAZ-3. In 1998, as political attitudes in Russia shifted away from cooperation with the US, the Russian Government adopted the resolution “On the Concept of the Development of Space Nuclear Energy in Russia,” aimed at “maintaining Russia's leading position in the field of space nuclear technologies, highly qualified personnel, a unique experimental and industrial-technological base, and infrastructure of scientific centers that carry out work in this area”. [8]
Russia’s primary active space reactor program is known as the Megawatt-class Nuclear Propulsion and Power Engine System (YaEDU). It is a joint project of a group of enterprises that are part of the Roskosmos and Rosatom consortium structures. The propulsion system will be designed and assembled by the Keldysh Research Center, while the main builder of the reactor unit is the N.A. Dollezhal Research and Development Institute of Power Engineering (NIKIET). Additional work on the project is being performed by the Arsenal Design Bureau and the Krasnaya Zvezda State Enterprise, which built the Soviet SNRs, as well as RSC Energia, the main manufacturer of Russian space components.
The project’s ultimate goal is to create a nuclear power plant for propulsion with an electric power capacity of at least 1 MWe (3.8 MWt) for use onboard a spacecraft. That spacecraft is named the Transport and Energy Module (TEM), and is often referred to as a space tug. Thus, the TEM will use nuclear electric propulsion, wherein thermal energy from a nuclear reactor is converted to electrical energy, which is then used to drive an ion thruster for propulsion while also powering other components of the ship. For more information on ion-thrusters and nuclear electric propulsion, watch the video below.
The YaEDU (Nuclear Propulsion and Power Engine System) consists of a small fast-neutron reactor. The chief designer of the reactor is Yuri Dragunov, a well-known academic and prolific writer of technical articles related to nuclear reactor designs. [9] Dragunov has argued that the design may be adapted for use in small nuclear power plants (SNPP), for example on a planetary surface. [10] The reactor is patented in the Russian Federation under the reference #2562237. [11] It uses highly enriched uranium dioxide (UO2) as fuel. [12] While the precise enrichment level of the uranium is not stated on the patent or on the information provided by any of the project’s contractors, academic articles mentioning the design put the enrichment level at 90% (thus HEU), which is the same as the Soviet BES-5 Buk SNR. [13]
The YaEDU has preliminarily designed reactor temperature of 1500° C, one of the highest among all space nuclear reactor designs. [14] The thermal power is converted into electric power through Brayton turbines. The reactor will be capable of working for more than 100 thousand hours (11 years). [15]
The YaEDU will be able to reduce the flight time to Mars, currently 1.5-2 years on conventional rockets, to just 2-4 months. [16] It is important to note that the YaEDU has no analogues in the world, as no nuclear electric propulsion system of this power has ever been built, and it depends on a number of major technological innovations, such as its cooling system. [17]
In 2010, Russian President Dmitry Medvedev ordered the creation of a transport module based on a megawatt-class nuclear reactor at the cost of 17 billion rubles or $600 million. [18] While Russia initially sought international partners in the project, as Russia’s relations with much of the international community began to deteriorate in 2011, Russia decided to continue development alone. [19] The total running cost is estimated at 20 billion rubles, which is now less than $300 million because of the Russian Ruble’s steep devaluation in 2014. [20] A total of 22 billion rubles ($342 million) were allocated to the project in the 2016-2025 Roscosmos budget. [21]
In 2013, Anatoly Koroteev, director of the Keldysh Center, said that the space nuclear reactor system design (YaEDU) would be ready by the end of 2014, and the entire installation would be ready for flight in 2018. [22] NIKIET completed testing the space nuclear reactor control system in 2014. [23] Technological tests of the reactor vessel were competed in 2015. [24]
In 2016, a flight prototype was expected to be ready as early as 2022-2023. [25] Also in 2016, Roscomos announced a tender for the development of proposals for testing key elements of the megawatt-class nuclear reactor onboard the International Space Station.
In 2017, Arsenal’s contract was modified to make a space tug not only with a nuclear power plant, but also with non-nuclear powered spacecraft electric propulsion system as a backup, which may be a sign of delays with the SNR. [26]
In 2018, the head of Roscosmos said that the TEM may at first only have a half-megawatt powerplant instead of a megawatt. He claimed that the final one-megawatt version would be ready for launch in 2030. [27]
Testing of the YaEDU’s cooling system, considered the most technically innovative part of the project, was completed in 2018. Its setup is similar to a shower, in which liquid does not circulate in pipes, but is sprayed in the form of droplets on the working circuit. These droplets are then released into space where they release heat. A hydraulic collector collects the cooled droplets and sends them back to the working circuit to repeat the cooling cycle. The larger surface area of the droplets allows the liquid to cool much faster than conventional cooling systems. Additionally, the structure becomes much lighter and its survivability increases - a meteorite flying through the liquid will not damage the cooling system. [28]
In 2018, Roscosmos fined the Keldysh Research Center for missing the deadline in the contract to fully assemble the YaEDU. [29] In 2020, Roscosmos is scheduled to launch a dummy of the TEM without the reactor. [30] In 2019, a model of the TEM, rather than an illustration, was shown to the public for the first time. [31]
Russia is developing an HEU-fueled SNR with a tentative launch year of 2030 as part of a ground-breaking system, and a prototype could be tested well before then. This project receives fairly substantial attention in the Russian media. Russia also has significant capabilities in the field of nuclear thermal rockets, but no outer space launches of these reactors are currently planned. Russia does not have an official HEU reduction policy, meaning that they are unlikely to forgo the use of HEU in space despite proactive engagement from the international community. [32]
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