Nuclear Rocket Concept Conceived.
The external and internal structure of isotope thermal batteries.
TOPAZ space nuclear reactor.
Apollo 14 Is placed in the lunar surface of the isotope hot batteries.
According to Xinhua News Agency recently, the Russian national space company initiated the development of laser orbit satellite charging 'orbital nuclear power station' was questioned, but in fact, in space has been widely used in nuclear energy and is expected to become space in the future Detect the core source of power.
Chemical energy, solar energy has limitations
Whether it is a manned spacecraft carrying astronauts traveling in space or a variety of unmanned aerial vehicles such as satellites and detectors, a large number of electronic equipment are equipped. A stable and sufficient power supply is the basic condition for the normal operation of the spacecraft.
Early spacecraft, most of the use of chemical batteries as a source of electricity.The basic principles of these chemical batteries and our daily life using dry batteries, cell phone batteries, etc., can continue to supply time is not long.When the battery power is depleted, Because there is nowhere to recharge, the spacecraft has to stop working, and China's Dongfanghong-1 satellite, which has only been working in space for 28 days, is limited by its battery capacity.
Today's spacecraft, orbital work most of the stretch out of a shape-like devices such as the well-known Shenzhou spacecraft, in the rear of the propulsion module has a pair of such 'wings.' The spacecraft's 'wings' Is a solar-powered windsurfing board whose function is not to fly, but to convert solar energy into electrical energy.With the continuous improvement of solar energy technology, solar panels have become more and more efficient and have become working near the earth Of spacecraft, and although the solar energy is inexhaustible, but if you want to fly like Spacefly to Pluto's 'Horizons' and the 'travelers' who fly out of the solar system, Solar energy is not enough to support spacecraft work, and as the distance to the sun increases, the sun's rays will become weaker and weaker and the solar panels will generate less and less electricity.
In fact, the sun's internal nuclear reaction comes from the fact that the sun emits light and heat, and at present, mankind has mastered the technology of using nuclear power generation and has established a number of nuclear power stations to convert nuclear energy into the electricity we need in our daily life In space, nuclear energy has also been widely used and is expected to become a core source of space exploration in the future.
Isotope hot battery deep space exploration of the mainstream power supply
Spacecraft power requirements, in addition to providing a stable power supply, but also requires it to small size, light weight, can work reliably over a long period of time, without failure.In order to achieve this requirement, the United States and the Soviet Union were selected Two different technical routes: At the time, the Soviets miniaturized nuclear reactors used on terrestrial nuclear power stations and equipped them with powerful satellites, while Americans were more likely to prefer safe, simple-structured isotope thermal batteries.
Isotope thermoelectric cells are not complicated in principle, and their basic structure is similar to that of a coal-fired furnace. The isotope thermoelectric cells are generally cylindrical in shape with nuclear fuel being able to generate heat through spontaneous decay reactions, such as briquette that is burning. The reason why isotope thermoelectric cells are able to convert the heat released by nuclear fuel into electrical energy is because the outer walls of the batteries that enclose the nuclear fuel are unusual and the outer wall device called thermocouple is made of special semiconducting materials.When thermocouple When temperatures are not the same on both sides, it can generate electricity outwards and convert heat energy into electricity, a phenomenon called voltage-induced temperature effect called 'Seebeck effect', by which German physicist Thomas John Named after Seebeck As the decay of nuclear fuel continues, the temperature difference between the inside and outside of the isotope thermal cell can persist, producing stable energy through the thermocouple.
In nature, there are many isotopes that can spontaneously decay, and the choice of what kind of isotopes to use as a nuclear fuel for an isotope thermal battery is also stressful. First, the decay rate of this element should not be too fast. In the short term, most of their energy will be released and can not sustain long-term spacecraft work. Second, the amount of energy produced per unit mass of nuclear fuel must be sufficient so that the spacecraft can meet its needs by carrying only a small amount of nuclear fuel, More weight is used to carry the payload for carrying out the task. Third, the type of radiation emanating from the nuclear fuel decay should be as easily absorbed by the thermocouple as possible.
After scientists screened these three criteria, plutonium 238 became the most widely used nuclear fuel for aerospace isotope hot batteries, with a half-life of 87.77 years and a power of 0.54 watts per gram of plutonium 238, satisfying the first two Even more commendable is that plutonium 238 in the decay, the radiation generated almost all of the thermocouple easy to absorb α rays, but not very strong penetration, but also not easily absorbed by the thermocouple β rays. , Almost all of plutonium 238 is absorbed by the thermocouple itself during decay, so that no additional shielding is provided outside the RTG to prevent the beta radiation from damaging other devices.
Plutonium 238, which has fewer sources and is more complex in its preparation, is therefore more costly and less productive, and currently produces only 1.5 kg of plutonium a year throughout the United States.238 However, due to its excellent properties, it has so far been difficult to find other alternatives that can fully replace it isotope.
June 29, 1961, the world's first nuclear-powered spacecraft 'Meridian' 4A military navigation satellite launched and successfully in orbit operation, the use of isotope thermal battery output power of only 2.6 W. After that, isotope thermal battery technology Thriving, with the exception of the 'Horizons' and 'travelers' mentioned earlier, the 'Cassini' probe that recently completed its mission to Saturn, the 'Galileo' probe that toured Jupiter, landing Mars rover Curiosity also uses isotope-powered thermal batteries, which are capable of delivering hundreds of watts to about a kilowatt of power.
In addition to supplying electricity, isotope thermal batteries sometimes use the 'waste heat' of power generation as a 'real stove' to heat spacecraft in space and 'heat' the spacecraft's equipment from being frozen. In "Martian Rescue," the protagonist Matt Damon once ventured to dug out an abandoned isotope hot-battery on a rover to warm himself up.
Space nuclear reactor high-power space power
Although the advantages of isotope thermal batteries are many, they have their own inherent disadvantages: on the one hand, their energy conversion efficiency is low, and generally only less than 10% of the radiation energy is converted into electrical energy. On the other hand, Kilowatts, the power of more spacecraft will be powerless and, with the depletion of nuclear fuel, isotope hot battery output will continue to decline.
Soviet Union in the sixties of last century also successfully design and manufacture of isotope hot-battery power, but perhaps the fighting nation is born with a desire for more powerful power, the Soviet Union's use of nuclear power almost all spacecraft nuclear power reactor space nuclear reactor. Space nuclear reactor like a narrow The nuclear power plant also heats up matter by chain fission reactions of nuclear fuel and generates steam to power the turbine generator to generate electricity. It can also control the operation of the reactor by plugging and unplugging the control rods and using water vapor on the ground Different from turbines, space nuclear reactors usually use steam engines with metal steam. In the 1960s, the Soviet Union successfully developed the BES-5 space nuclear reactor with an output of 3 kilowatts and later developed the TOPAZ reactor with an output of 6 kilowatts .
The first large-scale nuclear airspace incident was accidentally made while the Soviets succeeded in advancing space-borne nuclear reactor technology. The BES-5 reactor was largely assembled on the RORSAT, At a height of only 250 km, it is used to make a quick 'scan' of the Earth to monitor the movements of the U.S. Navy. When a RORSAT satellite is about to reach the end of its working life, it will launch its nuclear reactor onto a 950-kilometer high 'drop track' Where abandoned nuclear reactors will always float in space to avoid creating nuclear pollution on Earth and the rest of the satellite body will fall into the Earth under atmospheric resistance after it loses its motivation.However, in January 1978 On the 24th, an uncontrolled RORSAT satellite, code-named 'Universe 954', failed to properly eject its reactors onto 'discarded orbits' and instead carried it along with its nuclear reactors to disperse radioactive nuclear fuel on Canadian soil. The government had to spend a lot of manpower and resources to find and remove radioactive materials spread over thousands of square miles range .To this end, Canada and the Soviet Union After an international lawsuit demanding the Soviet Union compensate for the economic loss of 6.041 million U.S. dollars, the Soviet Union modified the design of the RORSAT satellite and installed a backup propulsion device on the reactor to keep the reactor normal when the main propulsion device failed At the same time, in the face of the potential risk of space nuclear accidents, U.S. President Carter signed an order banning the use of nuclear energy by U.S. spacecraft operating near Earth.
Nuclear fission nuclear reactors, while at risk, are the only sources of efficient, large-scale capacity utilization of nuclear energy currently in space, and the future will require the launch of more powerful and more-capable nuclear-powered rockets, as well as space-based nuclear reactors. At present, there are basically two technologically proven nuclear-powered rockets: the first is a thermonuclear rocket that uses the heat generated by the nuclear reactor to heat the liquid hydrogen from the fuel tank to a temperature of nearly 10,000 degrees Celsius before being ejected , Pushing the rockets with a strong airstream.At this point, liquid hydrogen did not act as a momentum-generating propellant, as the currently used rockets did, acting as a momentum-generating propellant.It was estimated that this rocket was carried with the same weight of propellant Capacity will be double the current use of chemical fuel rockets.Another more advanced and effective nuclear rocket program, it is the emerging electric propulsion technology and nuclear technology combined with nuclear power rockets.This rocket first use of nuclear energy Generated heat ionization of liquid hydrogen and other propellants to the plasma state.After that, re-use the nuclear reactor power, with electromagnetic Accelerate the plasma, resulting in huge thrust.Because the plasma in the electromagnetic force can be accelerated to a very high speed, or even close to the speed of light, so this rocket can quickly get enough momentum and energy to accelerate to Star Trek required speed.
