Clathrates are crystals consisting of tiny cages in which single atoms can be enclosed. These atoms significantly alter the material properties of the crystal. By trapping cerium atoms in a clathrate, scientists at the Vienna University of Technology have created a material which has extremely strong thermoelectric properties. It can be used to turn waste heat into electricity. (from phys.org)

A lot of energy is wasted when machines turn hot, unnecessarily heating up their environment. Some of this thermal energy could be harvested using thermoelectric materials; they create electric current when they are used to bridge hot and cold objects. At the Vienna University of Technology (TU Vienna), a new and considerably more efficient class of thermoelectric materials can now be produced. It is the material’s very special crystal structure that does the trick, in connection with an astonishing new physical effect; in countless tiny cages within the crystal, cerium atoms are enclosed. These trapped magnetic atoms are constantly rattling the bars of their cage, and this rattling seems to be responsible for the material’s exceptionally favourable properties.

“Clathrates” is the technical term for crystals, in which host atoms are enclosed in cage-like spaces. “These clathrates show remarkable thermal properties”, says Professor Silke Bühler-Paschen (TU Vienna). The exact behaviour of the material depends on the interaction between the trapped atoms and the cage surrounding them. “We came up with the idea to trap cerium atoms, because their magnetic properties promised particularly interesting kinds of interaction”, explains Bühler-Paschen.
For a long time, this task seemed impossible. All earlier attempts to incorporate magnetic atoms such as the rare-earth metal cerium into the clathrate structures failed. With the help of a sophisticated crystal growth technique in a mirror oven, Professor Andrey Prokofiev (TU Vienna) has now succeeded in creating clathrates made of barium, silicon and gold, encapsulating single cerium atoms.

The thermoelectric properties of the novel material have been tested. Thermoelectrics work when they connect something hot with something cold: “The thermal motion of the electrons in the material depends on the temperature”, explains Bühler-Paschen. “On the hot side, there is more thermal motion than on the cold side, so the electrons diffuse towards the colder region. Therefore, a voltage is created between the two sides of the thermoelectric material.”

Experiments show that the cerium atoms increase the material’s thermopower by 50%, so a much higher voltage can be obtained. Furthermore, the thermal conductivity of clathrates is very low. This is also important, because otherwise the temperatures on either side would equilibrate, and no voltage would remain.

“The reason for these remarkably good material properties seem to lie in a special kind of electron-electron correlation – the so-called Kondo effect”, Silke Bühler-Paschen believes. The electrons of the cerium atom are quantum mechanically linked to the atoms of the crystal. Actually, the Kondo effect is known from low temperature physics, close to absolute zero temperature. But surprisingly, these quantum mechanical correlations also play an important role in the novel clathrate materials, even at a temperature of hundreds of degrees Celcius.

“The rattling of the trapped cerium atoms becomes stronger as the temperature increases”, says Bühler-Paschen. “This rattling stabilizes the Kondo effect at high temperatures. We are observing the world’s hottest Kondo effect.”

The research team at TU Vienna will now try to achieve this effect also with different kinds of clathrates. In order to make the material commercially more attractive, the expensive gold could possibly be substituted by other metals, such as copper. Instead of cerium, a cheaper mixture of several rare-earth elements could be used. There are high hopes that such designer clathrates can be technologically applied in the future, to turn industrial waste heat into valuable electrical energy.

More than five decades of rocketry from Japan’s Kagoshima Prefecture will continue with the maiden voyage of the new Epsilon vehicle to insert an ultraviolet observatory into low-Earth orbit to observe Venus, Mars, and Jupiter. The 700-pound Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere (SPRINT-A) will utilize an extreme ultraviolet spectrometer and guiding camera and will spend about a year in orbit. Yet as exciting as this scientific payload may be, the Epsilon itself carries much promise for the Japan Aerospace Exploration Agency (JAXA). The rocket’s project manager has described it as a vehicle which will literally “open up the future.” (from americaspace.com)

The 78-foot-tall Epsilon vehicle marries one Solid Rocket Booster (SRB) from the H-IIA rocket as its first stage with upper-stage hardware from the 2006-retired M-V rocket. As a launcher, it is reportedly capable of transporting up to 2,600 pounds of payload into low-Earth orbit. Originally scheduled to fly on 22 August from the Uchinoura Space Center in Kagoshima, its launch date was postponed as JAXA required additional time to resolve a problem surrounding an incorrect line routing in the signal relay equipment used to check Epsilon’s critical functions.

Yet it is the cost savings—estimated to be about 30 percent better than the M-V—which JAXA is particularly keen to stress. The launch is estimated to cost in the range of 5.3 billion yen ($53 million), significantly lower than the 7 billion yen ($70 million) fee for an M-V, and such savings have been made partially through the streamlining of launch procedures. It is anticipated that subsequent Epsilon launches may bring costs still lower, into the 3.0-3.8 billion yen ($30-38 million) bracket.

Japan has been flying solid-fueled “pencil” rockets since the mid-1950s, and Epsilon stands firmly upon the shoulders of previous titans and utilizes new, cutting-edge technology. “We aim to greatly simplify the launch system by using artificial intelligence,” said Project Manager Yasuhiro Morita, quoted in a JAXA interview. Morita is a professor in the Department of Space Systems and Astronautics with the Institute of Space and Astronautical Science (ISAS), a subdivision of JAXA. “Today, a typical scenario is hundreds of people assembling at the launch center and working for several months in preparation for a launch. On the day of the launch, dozens of people are in the control room, monitoring every aspect. The Epsilon launch vehicle will drastically change this picture.” By running autonomous health and other checks, supported by artificial intelligence, it is hoped that control personnel with ultimately be able to run the whole show from a pair of laptop computers.

“Rockets use technology from many generations ago,” explained Morita, “so they are like a showcase of deficiencies. There has long been a notion that new technology should be tested over an extended period of time before being used in actual launch vehicles. Consequently, the latest artificial intelligence applications have not yet been employed in rockets. The Epsilon launch vehicle will be the first rocket with artificial intelligence that will perform checks and monitor its own operation autonomously.”

Moving forward from desktop and laptop computers, it is Morita’s hope that by 2017 the Epsilon will be in a position to “monitor and judge its own flight safety autonomously, so that we can remove the radar and antenna used to track and send commands to the rocket.” By assigning further artificial intelligence assets to the vehicle—including the capability to act as its own Range Safety Officer and destroy itself in the event of off-nominal events—the Epsilon will eliminate the need for expensive, ground-based hardware and further simplify launch and tracking facilities.

As the maiden flight of the Epsilon, the mission has attracted a great deal of publicity, both in Japan and around the world. In April-May 2013, it was the subject of a New Launch Vehicle Message Posting Campaign. Some 5,812 messages—the vast majority in Japanese and a few hundred in other languages—were received as part of an effort to share individuals’ “expectations, hopes, dreams, or feelings toward our new launch vehicle.” JAXA then processed these messages into strings of small letters on the Epsilon itself, in order to “make people feel more familiar with space, gaining more understanding of and support for space programs.” According to JAXA, this was a key goal of the Epsilon project.

Testing and processing of the new rocket has gone relatively smoothly, with its upper stage motor static-fired in September 2011 to evaluate the performance of insulation material, followed by last October’s extension test of the second stage motor nozzle. More recently, in April 2013, it was reported that a full-scale model of Epsilon had been transferred from the maintenance tower to the launch pad to demonstrate rollout and other pre-launch protocols.

Liftoff will begin with the ignition of the first-stage’s Nissan-built solid motor, producing an estimated 505,000 pounds of thrust. This will burn for about two minutes, after which the second stage—a modified version of the M-V’s M-34 upper stage, also solid-fueled, with an extendible nozzle—will pick up the thrust for 104 seconds to execute the next stage of the rocket’s climb to orbit. The third stage, based upon the KM-V2b upper stage from the M-V, will then fire for approximately 91 seconds, after which a hydrazine-fed small liquid propulsion system will provide the final boost. According to JAXA’s Epsilon press kit, this final stage will perform two burns and SPRINT-A will be separated from the vehicle about 61 minutes after launch.

The satellite is expected to operate for about a year in an orbit of 590-715 miles, inclined 31 degrees to the equator, from which it will observe the magnetospheric environments of Venus, Mars, and Jupiter. “Capturing the extreme ultraviolet rays emitted from a planet and its periphery, which cannot be observed from the ground, allows us to collect information on the atmosphere that flows into space and the magnetosphere covering the planet,” noted JAXA in its SPRINT-A mission brochure. “This enables us to analyze the composition of the atmosphere and the behavior of the magnetosphere. Our primary theme is each planet’s magnetosphere, the region where the magnetic field of a planet has influence.” Jupiter’s magnetic field is 10,000 times stronger than that of Earth and rotates on its axis at a high rate of around 10 hours per cycle, whereas those of Venus and Mars are far weaker. SPRINT-A will focus on the interactions between planetary magnetospheres and the solar wind.