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by : Nur Syuhadah Husein
Interplanetary satellites that fly toward planets such as Jupiter and Saturn are so far away from the Sun that they cannot use solar panels to generate their power. These satellites uses RTGs ( radioisotope thermoelectric generators ) to generate their power. An RTG uses radioactive material such as plutonium to generate heat and the thermocouples will convert the heat to electricity. RTGs have no moving parts, so they are reliable and the radioactive material generates heat for many years.

Satellites that uses RTGs (Plutonium-238) are :

1)    New Horizons

2)    Voyager 1 and Voyager 2

3)    Cassini-Huygens

4)    Galileo

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Example of Satellite : New Horizon (shared by Nur Syuhadah Husein)

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Example of Satellite : New Horizon (shared by Nur Syuhadah Husein)

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New Horizons uses RTG to get to Pluto

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Plutonium played a key role in the New Horizons mission to Pluto. More Plutonium: https://www.youtube.com/watch?v=89UNPdNtOoE Featuring Professor Martyn Poliakoff.

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By: Putri Annur Khaleeda

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Launchpad: History, Benefits and Safety of Radioisotope Power Systems

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Video nominated for a 2012 Capitol Region Emmy On our NASA site at: https://nasaeclips.arc.nasa.gov/playlists/launchpad?v=launchpad-history-benefits-and-safety-of-radioisotope-power-systems With safety designed from inside out and outside in, see how NASA has used Radioisotope Power Systems, or RPS, for more than 20 missions over the last 50 years.

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By: Putri Annur Khaleeda

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Launchpad: What Are Radioisotope Power Systems?

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On our NASA site at: https://nasaeclips.arc.nasa.gov/playlists/launchpad?v=launchpad-what-are-radioisotope-power-systems NASA uses Radioisotope Power Systems, or RPS, to convert heat from radioactive decay to electricity, creating predictable, continuous power for long missions in extreme environments. But learn how a next generation Radioisotope Stirling Engine will perform four times more efficiently and help NASA use even less of a precious resource.

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A Radioisotope Thermoelectric Generator (RTG, RITEG) is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect.

This generator has no moving parts. RTGs have been used as power sources in satellites, space probes, and unmanned remote facilities such as a series of lighthouses built by the former Soviet Union inside the Artic circle.

RTGs are usually the most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit.

HISTORY

The RTG was invented in 1954 by Mound Laboratories scientists Ken Jordan and John Birden. They were inducted into the National Inventors Hall of Fame in 2013. Jordan & Birden worked on an Army Signal Corps contract (R-65-8- 998 11-SC-03-91) beginning on January 1, 1957, to conduct research on radioactive materials and thermocouples suitable for the direct conversion of heat to electrical energy using Polonium-210 as the heat source. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg Ohio, under contract with the United States Atomic energy Comission. The project was led by Dr. Bertram C. Blanke.

The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, aboard the Navy Transit 4A spacecraft. One of the first terrestrial uses of RTGs was in 1966 by the US Navy at uninhabited Fairway Rock in Alaska.

By: Putri Annur Khaleeda

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 A model of enhanced multi-mission thermoelectric generator.

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 A model of enhanced multi-mission thermoelectric generator.

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By : Aiqa Arbila Abdul Halim

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How does thermoelectric device contribute to a change in power source ?

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How does thermoelectric device contribute to a change in power source ?

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By : Aiqa Arbila Abdul Halim

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A radioisotope thermoelectric generator (RTG, RITEG) is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect.

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Heat being an important power source in a spacecraft ?

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Heat being an important power source in a spacecraft ?

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By : Aiqa Arbila Abdul Halim

When it comes to space mission where security is the top most priority, there is a constant revolution on what can be further improved and these contributing factors often originate from the basic power system source, solar radiation ( sun), dynamic power ( movement ), fuel cells ( chemical ) and static power conversion ( heat ). Without a power system which is adequate in sustaining the harsh unpredictable space environment, the objectives of a space mission is at a risk of being compromised.

Related Articles - Significance of a Power System in a Spacecraft.

How does thermoelectric play a paramount role in a spacecraft mission?

Now, generally thermoelectric functions to produce electricity when there is a difference in temperature. In spacecraft language and application, thermoelectric devices exploits heat from engines and motors and use it to power sensor and wireless sensor for condition monitoring execution.

- Improved system efficiency when paired up with solar cell to produce more power.
- Reduced cost by reducing petrol consumption through aircraft engine waste heat harvesting.
- A significance increased in performance when communication front end cooling reduces noise.

There are limitations however when it comes to the current possible market thermoelectric devices in terms of efficiency and cost and the most suggested improvement is to come up with high payoff applications capable in exceeding the maximum degree.

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Why are Power Systems important?

A reliable, ongoing power supply is essential to a space mission's success. The Sun provides around 1.4 kilowatts of power per square metre in Earth orbit - a bountiful resource that spacecraft designers do their very best to take advantage of. This is why the majority of spacecraft incorporate wing-like solar arrays or else have them layered across their hull.

These are composed of photovoltaic cells connected in a network, which produce an electrical current when light shines on them -working like the light emitting diodes of (LEDs), but in reverse. It is interesting to note that the technologies behind both solar cells and LEDs are very similar.

But this free availability of power does not mean designing a satellite's power system is an easy task. Photovoltaic cells efficiency reaches 30% for the latest designs but it is reduced by heating from the Sun and radiation damage during a satellite's lifetime. This means that solar arrays have to be of a significant size to deliver useful power levels (in the order of tens of square metres for a typical communications satellite).

Most satellites have orbits that will take them out of the Sun into shadow behind the Earth - for a low-Earth orbiting spacecraft that occurs once per orbit - so they are also equipped with rechargeable ('secondary') batteries to keep them powered in the meantime. These batteries are in general the only power source available just after launcher separation and until the solar generators are deployed and properly Sun pointed.

A satellite's electrical loads will often vary, depending on which instruments or subsystems are running at a particular time. One of the most important tasks of the power conditioning is therefore to control in an optimum way the exchanges of power between the solar generator, the battery and the loads. This means ensuring that the power delivered to the loads stays within the voltage range they can accept, sizing the solar array so that the battery can be replenished while the spacecraft equipment are supplied, ensuring that the battery will not experiment any excess charging current or voltage but also, in some exceptional anomalous situations, being able to disconnect some units (the so called non -essential ones) to avoid a battery full discharge and to safeguard the spacecraft.

The power system being a unique resource of the spacecraft, it has to be protected against failures of the supplied units that could degrade it or even take it out of service, especially short-circuits. This is exactly the same concern as in a house, where a centralised distribution panel hosts circuits breakers or fuses to eliminate uncontrolled current surges. Aboard a spacecraft both fuses or electronic circuit breakers are commonly used.

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A reliable, ongoing power supply is essential to a space mission's success. The Sun provides around 1.4 kilowatts of power per square metre in Earth orbit - a bountiful resource that spacecraft designers do their very best to take advantage of. This is why the majority of spacecraft inco...

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By: Cheaw Boon Hong
What if there were a way to take the waste heat that spews from car tailpipes or power plant chimneys and turn it into electricity?
Actually the idea had been turned into a reality. Now, everyone has used to called it Thermoelectrics.A thermoelectric is a material that turns heat into electricity.
Mechanism of Thermoelectrics is shown below

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**By Sing Mei

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Thermoelectric power generation - thermoelectric power generator

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Thermoelectric power generation using a Tellurex Z-max thermoelectric module. By applying heat, we create a temperature difference across the two services of the thermoelectric module, resulting in enough power to energize the light connected to the thermoelectric module.

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**By Sing Mei
Seebeck effect occurs when 2 different types of semi-conductive metals are connected. When one end of it is being heated (by the heat produced from radioactive elements), electric potential is produced and electrons will start to move.  Electrons move from the heated part to the colder part. This movement of electrons will  generate electrical current, powering electrically driven device connected in the middle.

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**By Sing Mei
Heat that is needed to generate power comes from decay of radioactive materials. Normally, the power generated by heat from decay of radioactive is used for interplanetary missions requiring power of hundred watts. Radioactive materials decay into non-radioactive elements depend on their half-life. Different radioactive isotopes have different half-lives which can last for years.

Radioisotope thermoelectric generators employ radioactive materials to produce heat and make use of a principle of electrics known as Seebeck effect.

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Video of Application of RTG in Space Exploration

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Video of Application of RTG in Space Exploration

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By: Tan Chun Khuen

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Radioisotope Thermoelectric Generators: RTG Energy for Space Exploration

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This US Department of Energy Video describes how Radioisotopic Thermoelectric Generators (RTGs) can be used to provide power for space probes.

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By: Tan Chun Khuen
RTGs work by converting the heat given off by a radioactive isotope (such as plutonium) into electricity by an array of thermocouples which then power the spacecraft.

What is isotope? They have extra neutrons and they become radioactive, releasing protons, neutrons, and energy in a process called decay. This is a much different technique than that used by nuclear power stations on Earth. Nuclear reactors generate heat by fission, a process in which atoms are split by a bombardment of neutrons. In an RTG, heat is generated only by the natural radioactive emissions of the isotope contained in it.

After the heat is obtained by radioactive decay of isotope, how does the heat convert into electricity? This can be done by thermocouple. Thermocouple is made of two kinds of metal that can both conduct electricity. They are connected to each other in a closed loop. If the two metals are at different temperatures, an electric potential will exist between them. When an electric potential occurs, electrons will start to flow, making electric current. This is called the Seebeck effect.

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By:Cheaw Boon Hong

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New thermionic generator overcomes the "space-charge problem"

A new type of thermionic generator that turns heat or light into electrical energy has been developed by researchers in Germany and the US. The new design overcomes the "space-charge problem" that has plagued previous attempts at developing practical devices. The device is about four times more efficient than previous generators and the new technology could find use in a range of applications including solar power and the harvesting of waste heat.

Thermionic generators convert heat or light into an electric current by using the temperature difference between two metallic plates that are separated by a vacuum. The "hot" plate is heated either by incident light or thermal conduction and this causes electrons to evaporate from its surface. These electrons then condense on the surface of the cold plate. This creates a charge difference between the two plates, which can drive a usable electric current.

Because they convert heat or light directly into electrical energy, thermionic generators have considerable potential for practical applications. If used in coal-fired power stations, for example, thermionic converters would, in principle, be more efficient than steam turbines. Thermionic generators could also be applied to a variety of lower-temperature applications, such as the collection of solar energy or the recycling of waste heat in car engines.

The space-charge problem

While this potential for highly efficient energy conversion has been known since the late 1950s, the practical applications have been severely limited by what is called the space-charge problem. For plates separated by more than about 3-5 μm, the negative charge of the "cloud" of electrons that forms in the gap inhibits subsequent electrons from being emitted from the hot plate. This effectively puts a halt to the flow of electrons between the plates. While reducing the gap between plates would help, making a generator with plates that maintain a separation of less than 3 μm at high temperatures is extremely challenging.

Previous efforts to solve the space-charge problem have mainly involved inserting caesium ions into the space between the two plates. The positive ions act to neutralize some of the offending charge, thus allowing more electrons to be released from the hot plate. While this approach has been used in the lightweight TOPAZ nuclear reactors that powered some Soviet satellites, it results in a drop in power output of about 50%.

Now, Jochen Mannhart of the Max Planck Institute for Solid State Research in Stuttgart - along with colleagues at the University of Augsburg and Stanford University - has come up with a new way of solving the space-charge problem by creating an electric field in the space between the plates. This field first accelerates the electrons leaving the hot plate and then slows them down as they approach the cold plate. The charge cloud is therefore moved along and does not repel subsequent electrons - allowing for a continuous current. The field itself is created by a honeycomb-patterned gate with hexagonal holes in it. The electrons are guided through the holes by applying a magnetic field between the plates.

A 40% efficiency could be possible

"Practical thermionic generators have reached efficiencies of about 10%. The theoretical predictions for our thermionic generators reach about 40%," says Mannhart. This figure also incorporates the energy needed to create the electric field.

Mannhart and colleagues believe that commercialization of their design could take a further 5-20 years, depending on whether the application is high temperature or low temperature. For the latter, Mannhart says that further optimization of the converter would be needed.

Nicholas Melosh of Stanford University, who was not involved in this study, describes the work as a "clever new technique" to address the space-charge problem, adding that "while more development still needs to be done, this principle could create new devices to convert waste or solar-generated heat into useful electricity".

Planar triode revival

Neil Fox of the University of Bristol in the UK points out that the new generator has similarities to a planar triode design tested at the Massachusetts Institute of Technology (MIT) in the late 1950s. This previous design had suffered from energy loses caused by electron-electron collisions and scattering. "[Mannhart and colleagues] have come up with a rather neat vertical triode structure that seeks to improve on the MIT device, by incorporating beam collimating concepts similar to those used in particle accelerators," explains Fox. "The data presented...show that this magnetic triode is a significant improvement over a closed-spaced diode, but suggests that electron-electron collisions and scattering losses to the gate are still present."

The team is now working to increase the efficiency of its generator design in two ways. First, it is building high-performance converters from existing semiconductor technologies. Second, it is optimizing its electrodes through the use of new materials, especially oxides, and nanotechnology.

The work is described in the Journal of Renewable and Sustainable Energy.

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New generator creates electricity directly from heat - Physics World

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A new type of thermionic generator that turns heat or light into electrical energy has been developed by researchers in Germany and the US. The new design overcomes the "space-charge problem" that has plagued previous attempts at developing practical devices.

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By:Cheaw Boon Hong

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1. Hong
2. Sing Mei
3. Putri
4. Aiqa
5. Syuhadah
6. Chun Khuen

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One of the source of power for spacecraft is from the Heat. Please find all necessary info on this Power source. You should define what is thermoelectric. How can heat generate power? find an example of spacecraft use heat. What is RTG? how RTG works.