MAI told how plasma engines have increased the payload capacity of Russian missiles
Plasma engines were able to significantly increase the payload capacity of the Russian Soyuz and Proton rockets. Slow, but effective, they allow you to take much more cargo into high orbits. What will be the new fuel for such engines and whether they can be used for flights to the Moon, other planets and on the ISS, "Gazeta.Ru" said Vladimir Kim, Chief Researcher at the Research Institute of Applied Mechanics and Electrodynamics of the Moscow Aviation Institute.
- Plasma engines are increasingly being used in space, Russia retains a leading position in this area. Tell us, when did you think about using such engines?
- It happened in the early 60s. But the first ideas on the acceleration of ions by an electric field in a plasma layer with a transverse magnetic field were expressed back in the late 50s by Askold Zharinov, a researcher at the Institute of Atomic Energy of the USSR Academy of Sciences. And in 1961, he proposed an engine circuit with an anode layer that implements this idea. Following this, in 1962, another employee of the IAE, Alexey Ivanovich Morozov, proposed accelerating ions in an extended plasma layer with crossed electric and magnetic fields with fields of a certain configuration, and the first laboratory models of future stationary plasma engines (SPD) were created at the IAE under his leadership by 1964. By 1968, long - running models had already been created,
Usually, when a satellite is launched, it does not fall exactly into the orbit that is convenient from the point of view of a periodic review of the Earth's surface. And this experimental engine was able to change the altitude of the satellite's orbit by about 17 km and transfer it to the so-called sun-synchronous orbit, which was perceived as a great success and accelerated further development of the SPD (stationary plasma engine. - "Newspaper.Ru»).
- Electro-reactive engines include plasma and ion engines. What is their difference?
- In an ion engine, only ions are accelerated by an electric field and a unipolar (mono-charged) flow is formed. Therefore, only a certain flow of ions can be passed through the acceleration system at any given time, because their volumetric charge limits the ion current density and the density of the resulting thrust.
To date, several types of plasma engines have been developed. Their main difference from ion engines is that the acceleration of ions flowing out of the engine in them is carried out in a plasma medium containing approximately the same number of ions and electrons per unit volume, which removes the limitation of the current of accelerated ions by their volume charge. This makes it possible to obtain significantly higher flow densities of accelerated ions and reactive thrust in plasma engines, and engines for obtaining the same thrust are significantly smaller.
- Was the USSR a leader in the development of SPD?
- After the first launch of the USSR, work on the creation of SPD accelerated, and up to the 90s their development was carried out only in the USSR. The Americans also started these works in the early 60s, but after a few years abandoned them, considering that these engines are not very efficient.
After everything went well with us, Americans and specialists from other countries returned to the idea in the early 90s. They began to get acquainted with the results, invite our specialists, and start joint work. And by the 2000s, they had accumulated experience in order to start their own developments.
- What determines the service life of the engine, fuel reserve or wear?
- The service life, of course, is determined by how much of the working substance ("fuel") is filled in the tanks (as in the car). Besides, every engine wears out sooner or later anyway. It turned out that in the SPD it is difficult to perfectly focus the flow of ions, which "touches" the walls of the discharge chamber and "constricts" them, which determines the life of the engine. The first engines could work 100 hours, the first flown engines could work thousands of hours, and modern engines can already work tens of thousands of hours.
Electric rocket engines (ERD) differ from chemical jet engines in that they use a working substance more economically, which is called "fuel" in foreign works. This is the main advantage of the ERD. If a liquid jet engine has a maximum exhaust velocity of 4-5 km/s, then the SPD already provides an expiration velocity of 10-20 km/s. And today this indicator reaches 30 km/s, which is 3-10 times better than that of low-thrust chemical engines. Accordingly, in order to obtain the same thrust, it is necessary to spend as many times less working substance.
- What is the fuel?
- "Fuel" is characteristic of chemical engines, in which the energy for its acceleration is obtained by burning it. In the ERD, the particles of the working substance are accelerated due to the electrical energy supplied to the engine from the outside. Until very recently, xenon was used in the SPD as a working substance. It is an inert gas with a large atomic mass, ionizes well and is stored well. Recently, krypton has also begun to be used. It is worse in terms of engine efficiency, but it is significantly cheaper. The problem with xenon is that it is very expensive, rarely distributed in nature and produced in relatively small quantities. Until recently, only a few tens of tons of xenon per year were produced in the world.
Our work on krypton has so far been purely research, since we did not have such a rigid need and we have not yet reached its application.
- Why, nevertheless, do Western companies use our SPD OKB "Torch"?
- Fakel started developing the SPD, starting with the first sample tested in space, and since then it has been producing the SPD-50, SPD-70, SPD-100 and SPD-140 engines, which fly on our and Western satellites. Therefore, Fakel has accumulated a lot of experience in creating flight products, and in fairly large volumes. As a result, the "Torch" engines have very few failures. In the West, until recently, there were no specialized enterprises that industrially produced this type of engines, and they did not have as much experience in using SPD in space as the Torch.
- What is the main problem solved by the LDS in space?
- Until recently, it was mainly bringing satellites to a working point in geostationary orbit (GSO) and maintaining them at this point for 10-15 years of their active existence, which made it possible to reduce the mass of the RV necessary for this and thereby increase the mass of the target equipment. In recent years, a new problem has been solved: we have a certain set of launch vehicles (LV) that can put spacecraft of a certain mass into reference orbits, and then either they bring the spacecraft to the GSO with an upper stage, or slowly (due to low thrust) transfer it to the target orbit with the help of SPD. Due to low thrust, more time is spent, but it is possible to deliver there one and a half to three times more mass in 3-6 months..
For example, "Proton", using a traditional upper stage, can bring a little more than 3 tons to the GSO, and "Unions" - about half a ton.
If you use the ERD, then the Soyuz with RB and ERD can already deliver 2-2.5 tons to the GSO. And on the "Proton" with RB and ERD, 4 or more tons are quietly delivered there. It takes a long time, but the effect on the delivered mass is ultimately much greater. The longer we work with the ERD, the greater the mass effect.
- If the SPD has been used for a long time, then what is your work at MAI to create an electoreactive system for pre-launch and orbit correction of high-mass vehicles?
- Our Institute has been working for many years with JSC "Information Satellite Systems" (JSC ISS) to find ways and develop ways to use ERD to improve the efficiency of these satellites. Our specialists have studied different carriers, different upper stages, different withdrawal schemes, traction control programs. What is the difficulty of flying to the ERD? A spacecraft with an ERD-based motion control system makes many, many turns before it goes out, for example, to the GSO. They justified the expediency of using the ERD, and new programs for controlling this low-thrust movement were developed and recommended.
Next, we created a mock-up sample of the main elements of the motor system, which can be used to solve this problem. We studied the joint operation of the SPD-140D engine, which we have not yet used, with the power supply system developed by the Tomsk SPC Polyus. Since the engine is a gas-discharge device, special testing of its combination with the power supply system is required.
If you want to deliver a heavy satellite to the target orbit quickly enough with the help of the SPD, you need more thrust - you can use two engines or SPD-140 engines with more thrust. Therefore, we conducted a preliminary study of this possibility. In addition, we have conducted docking tests - this is the joint work of the engine, conversion and control systems.
The spacecraft has a solar battery that produces electricity with a voltage of 27, 50 or 100 volts. And then, in order for the engine to work, a voltage conversion and control system is needed. We have shown that, in principle, it is possible to reliably launch and sustainably work with the engines that Fakel currently has, with the conversion and control system developed by the Polyus SPC.
A new direction that we are currently developing ourselves is engines on krypton. MAI is experimenting with systems of different power, ranging from 100 watts to a dozen kilowatts. This is a fairly wide range. We are creating competitive samples that can be converted into flight ones. In particular, we are ready to transfer engines of low power, up to 1 kW, to the industry. And we are already waiting for customers who will make engines.
- Has the correctness of your calculations already been confirmed by real launches?
- The pre-launch system based on the SPD engines in Russia has already worked when launching six satellites on the GSO. For the first time it was implemented during the launch of the Express AM5 and Express AM6 spacecraft, which could not be delivered to the GSO without using the ERD, since the spacecraft's masses exceeded the rocket's capabilities by 100 -200 kg.
Therefore, the standard engines of the spacecraft orientation and correction system based on the SPD-100 engines were used, and they were brought to the GSO by the named engines, which were then used for orbit correction.
- What was the uniqueness of the paired launch of the Express-80 and Express-103 satellites by one Proton on July 31, 2020?
- Special engines have already been installed on them, which were designed for pre-production. The total mass of the satellites was more than 4 tons on the GSO, i.e. significantly more than with a conventional launch on the Proton geostationary rocket with an upper stage. With the addition of the ERD, they were put into an intermediate orbit with one launch, and then each of them was released into its orbit by two SPD-100 engines. One for 160, and the other for 149 days, and the effect of increasing the delivered mass on the GSO of the mass of two spacecraft was 775 kg.
The operating time of geostationary satellites is now about 15 years. Compared to 15 years, even six months is not such a terrible amount. That's why many people are doing it now - both here and abroad.
- What prospects does the use of more powerful SPDs open up?
- The Americans considered the possibility of using commercial engines of the OKB "Torch" for the implementation of interplanetary flights. American and Japanese probes, for example, the Hayabusa spacecraft, have already flown to asteroids on ion engines. Ion engines have even higher expiration rates and are considered more promising for deep space flights. And the SPD are considered suitable for solving near-Earth problems. On the SPD type engines, the longest flight was made to the Moon under the European Smart 1 program.
We don't look that far, mostly while we're looking at the moon in terms of using these engines. In particular, options for lunar ferries are being considered, with which it is possible to transport cargo to the Moon and/or back.
The possibility of interplanetary flights of automatic spacecraft with the SPD was also considered. So, our ballistics have already simulated flights of such spacecraft to distant planets and have shown that in some cases it is possible to achieve the goal even faster than using traditional chemical engines.
- Is it possible to use the SPD to maintain the altitude of the ISS orbit or the future ROSS station?
- Such proposals have already been made by us and other specialists. For example, the ISS can be supported not by conventional Progress cargo ships, but by a Progress equipped with an LDS-based propulsion system, which will support the station in the desired orbit, compensating for aerodynamic drag with less working matter and, consequently, with fewer Progress launches.
- Which engine is sufficient for these purposes?
- For example, two engines of the SPD-140 scale. In principle, there should be enough electricity on the ISS, because now more than 100 kW is produced on board the ISS and it is possible to allocate the necessary power at the level of 10 kW for such a propulsion system.
- What are the prospects for creating a nuclear-powered SPD instead of a solar one?
- The SPD has already flown with power from a nuclear source. Projects using nuclear-electric tugs with ion engines are also being worked out. These are specific and rather complex devices that can be developed and used to implement promising lunar and interplanetary programs.
Pavel Kotlyar
