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Россия отправляет космический аппарат на Фобос - Наука и техника - Космос - Космонавтика и исследования космоса - Межпланетные аппараты - Компьюлента

Наука и техника / Космос / Космонавтика и исследования космоса / Межпланетные аппараты / 10 июля 2001 года, 17:14 | Текст: К. Т. В 2005 году к Марсу отправится российский космический аппарат "Марс-Фобос-Грунт". Сейчас этот проект находится в стадии опытно-конструкторских работ. Предыдущие отечественные проекты по исследованию тел Солнечной системы были ориентированы на запуск межпланетных аппаратов дорогостоящим ракетоносителем тяжелого класса "Протон-К". "Марс-Фобос-Грунт" принадлежит к иному классу космических аппаратов, и в космос его могут выводить ракеты лёгкого или среднего класса. // Дальше — www.compulenta.ru

 

В 2005 году к Марсу отправится российский космический аппарат "Марс-Фобос-Грунт". Сейчас этот проект находится в стадии опытно-конструкторских работ.

 

Mini nuclear reactor could power apartment blocks

19:00 22 August 01
Peter Hadfield and Michael Fitzpatrick

A nuclear reactor designed to generate power in the basement of an apartment block is being developed in Japan. In the past few months government-backed researchers have been testing a fail-safe mechanism for the reactor, which will close down automatically if it overheats.


Photo: Stone
The Rapid-L reactor was conceived as a powerhouse for colonies on the Moon. But at six metres high and only two metres wide this 200-kilowatt reactor could relatively easily fit into the basement of an office building or apartment block, where it would have to be housed in a solid containment building.

"In the future it will be quite difficult to construct further large nuclear power plants because of site restrictions," says Mitsuru Kambe, head of the research team at Japan's Central Research Institute of Electrical Power Industry (CRIEPI).

"To relieve peak loads in the near future, I believe small, modular reactors located in urban areas such as Tokyo Bay will be effective," he says. Kambe's research is being financed by the Japan's Atomic Energy Research Institute.


Liquid control


Unlike normal nuclear reactors, the Rapid-L has no control rods to regulate the reaction. Instead, it uses reservoirs of molten lithium-6 - an isotope that is effective at absorbing neutrons. The reservoirs are connected to a vertical tube that runs through the reactor core.


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During normal operation the tube contains an inert gas. But as the temperature of the reactor rises, the liquid lithium expands, compressing the inert gas and entering the core to absorb neutrons and slow down the reaction.

The lithium acts as a liquid control rod. And unlike solid control rods, which have to be inserted mechanically, the liquid expands na…

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Fragment of ancient asteroid falls to Earth

[23 Aug 2001] A meteorite that plunged to Earth in January 2000 may be the first fragment ever found of a primitive kind of asteroid. The characteristics of the Tagish Lake meteorite closely match the 'D-type' asteroids common in the outer solar system, according to Takahiro Hiroi of Brown University, US, and colleagues. Meanwhile, Sandra Pizzarello of Arizona State University and team analysed the carbon-rich meteorite to shed light on the chemistry of the early solar system (T Hiroi et al; S Pizzarello et al 2001 Science to appear).
Asteroids are classified by their optical properties and their dynamics. Most meteorites are thought to be fragments of asteroids, so the spectrum and brightness of the light reflected from a meteorite helps astronomers to identify which type of asteroid it came from. The arrival time of the meteorite on Earth is also a crucial factor in matching it to the motion of a certain asteroid.

Hiroi and colleagues found that the Tagish Lake meteorite reflected just 3% of the light incident upon it, a similar value to D-type asteroids. The spectrum of this reflected light also very closely matched that of a particular D-type asteroid called 368 Haidea. But the team found that another candidate - asteroid 773 Irmintraud - was more likely to have lost fragments at the right time because it was more strongly distorted by Jupiter's gravity.

Hiroi and colleagues hope that better observations of D-type asteroids and more detailed studies of their dynamics will allow them to identify the parent asteroid of the Tagish Lake meteorite with greater certainty. They warn, however, that it is difficult to match meteorites with asteroids: those meteorites that reach Earth are not a representative sample because many are too fragile to survive the journey through our atmosphere.

Pizzarello and co-workers believe that the Tagish Lake meteorite - preserved…

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Lasers energise fusion research
[23 Aug 2001] A new method to kick-start nuclear fusion has boosted hopes of harnessing the energy that powers the Sun. Scientists from Japan and the UK have used lasers to both compress and ignite the nuclear fuel, a technique that could be scaled-up to power reactors that produce hundreds of times more energy than they consume (R Kodama et al 2001 Nature 412 798).
Nuclear fusion is an attractive potential source of energy because the two isotopes of hydrogen used for fuel - deuterium and tritium - are readily available. It also produces no carbon dioxide or long-lived radioactive decay products. However, a temperature of about 50 million degrees is required to overcome the repulsion between the fusing deuterium and tritium nuclei.

The new 'fast ignition' technique has been demonstrated by Ryosuke Kodama and colleagues of Osaka University and researchers from the Rutherford Appleton Laboratory, Imperial College and the University of York in the UK. Like the conventional 'inertial confinement' method, fast ignition uses laser pulses to compress pellets of deuterium and tritium and the exploding plasma surrounding the pellets causes an equal and opposite implosion of the fuel. But unlike the old approach, in which the compressed fuel is heated by the collapse of accurately timed shock waves, fast ignition uses a second, shorter, laser pulse to start the fusion chain reaction.

The technique requires a less precise implosion but is more difficult because the short laser pulse is deflected by instabilities it creates in the plasma. The researchers resolved this problem by inserting a polymer cone inside the fuel pellet, which allows the beam to pass through unimpeded.

The use of a second laser halves the amount of energy needed to power the long-pulsed laser. The team now needs to establish if increasing the energy of the short-pulsed laser raises the fusion temperature. "At the moment…

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First hints of novel nuclei

[21 Aug 2001] A super-heavy isotope of hydrogen that has four neutrons and a proton in its nucleus has been detected for the first time. Physicists have been attempting to create hydrogen-5 - which is thought to exist inside stars - for over 40 years. An international collaboration identified the highly unstable isotope at the RIKEN detector in Japan (A Korsheninnikov et al 2001 Phys. Rev. Lett. 87 092501). Meanwhile, physicists at Brookhaven National Laboratory in the US have created a significant number of nuclei containing two 'strange' quarks. Such matter is thought to be abundant in neutron stars (J Ahn et al 2001 Phys. Rev. Lett. to appear).
Physicists from RIKEN, the JINR and Kurchatov laboratories in Russia, and the GANIL laboratory in France detected the hydrogen-5 in collisions between a beam of helium-6 nuclei and a cryogenic hydrogen target. When a helium-6 nucleus collides with a hydrogen nucleus, it can donate all four of its neutrons to the hydrogen. This leaves two spare protons that are ejected from the target as a helium-2 nucleus, which quickly decays into two protons. The energies and angles of the protons were measured by the RIKEN detector, and revealed a peak in the energy spectrum consistent with a hydrogen-5 nucleus.

In the Brookhaven experiment, a team of 50 physicists from six countries created the strange nuclei by firing an intense beam of protons at a tungsten target to create a beam of 'kaons' - particles that contain one strange quark. The kaons impinged on a beryllium target to create both strange quarks and antiquarks. These quarks and antiquarks can then form a nucleus consisting of a proton, a neutron and two 'lambda' particles. Each lambda particle contains one up, one down and one strange quark, making the nucleus 'doubly strange'.

Around 40 such nuclei were produced in the Alternating Gradient Synchrotron at Brookhaven. "That's enough events to begin a s…

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