Thursday, 19 April 2007

Starship: Plasma Shields

Shields For Starships: A Reality?

To protect the occupants from the potentially lethal radiation in space from the Sun, a superconducting ring on board the space craft could produce a magnetic field, or mini-magnetosphere, similar to the Earth's, which would create a 'deflector or plasma shield'.
(Credit: Image courtesy of Royal Astronomical Society)

Cosmic rays and radiation from the Sun itself can cause acute radiation sickness in astronauts and even death. Between 1968 and 1973, the Apollo astronauts going to the moon were only in space for about 10 days at a time and were simply lucky not to have been in space during a major eruption on the sun that would have flooded their spacecraft with deadly radiation. In retrospect Neil Armstrong’s ‘one small step for Man’ would have looked very different if it had.

On the International Space Station there is a special thick-walled room to which the astronauts have had to retreat during times of increased solar radiation. However on longer missions the astronauts cannot live within shielded rooms, since such shielding would add significantly to the mass of the spacecraft, making them much more expensive and difficult to launch. It is also now known that the ‘drip-drip’ of even lower levels of radiation can be as dangerous as acute bursts from the sun.

On the surface of the Earth we are protected from radiation by the thick layers of the atmosphere. And the terrestrial magnetic field extends far into space, acting as a natural ‘force field’ to further protect our planet and deflecting the worst of the energetic particles from the Sun by creating a ‘plasma barrier’.

Now scientists at the Rutherford Appleton Laboratory in Oxfordshire plan to mimic nature. They will build a miniature magnetosphere in a laboratory to see if a deflector shield can be used to protect humans living on space craft and in bases on the Moon or Mars.

In order to work, an artificial mini-magnetosphere on a space craft will need to utilise many cutting edge technologies, such as superconductors and the magnetic confinement techniques used in nuclear fusion.

Thus science is following science fiction once again. The writers of Star Trek realised that any space craft containing humans would need protection from the hazardous effects of cosmic radiation. They envisioned a ‘deflector shield’ spreading out from the Starship Enterprise that the radiation would bounce off. These experiments will help to establish whether this idea could one day become a practical real.
Astronomers Map Out Planetary Danger Zone
Astronomers Make Detailed Image Of Giant Stellar Nursery
Hubble Space Telescope Reveals The Aftermath Of 'Star Wars'

Sunday, 15 April 2007

Where is The Proton?

Scientists Discover Footprints Of Shared Protons

This week in Science, Yale researchers present "roadmaps" showing that shared protons, a common loose link between two biological molecules, simply vibrate between the molecules as a local oscillator, rather than intimately entangling with the molecular vibrations of the attached molecules.

The paper reports clear "roadmaps" for the widely varying, characteristic vibrational frequencies that occur when an excess proton binds together simple nitrogen and oxygen containing molecules.

Rather than studying the proton-trapped pairs of molecules in crystals or in solution at room temperature, as has been common in the past, Johnson's team made their measurements of proton interactions with 18 simple molecules by isolating them in the gas-phase and cooling them to about 50 Kelvin by taking advantage of recent advances in argon nanomatrix spectroscopy.

"Historically it has been very difficult to isolate the signature of an excess proton in a complex environment like a cell membrane, and say with confidence 'Aha, I have one,'" said Johnson. "The proton is in constant motion in a warm, disordered medium, which causes its natural vibrational frequency to spread out over a huge spectral range. As a result, its 'signature' is often thought to comprise the continuous 'junk' background in the vibrational spectra of protonated samples."

"When we cool the isolated systems, the protons sing out their sharp vibrational frequencies, and therefore provide clear signatures that are characteristic of each kind of interaction," said Johnson.

Two oxygen atoms on different molecules are connected by their mutual attraction to an extra proton, shown as a fuzzy ball between them. The presence of such intermolecular binding can now be identified by monitoring the precise vibrational frequency of the bridging proton. (Credit: Image courtesy of Yale University)

The research shows that the extra proton is associated with a specific pair of atoms on the two tethered molecules, participating in partial chemical bonds to both. "In biological systems, any time you have molecules with a nitrogen or oxygen, and add in an extra proton, the proton forms a bond with one of the extra electron pairs that are available," according Johnson. "It crashes the party and changes the character of the molecule."

Extending Johnson's analogy, if another molecule containing nitrogen or oxygen comes by, the proton crashes that party, too. Because the proton is not deciding between one molecule and the other, it is creating a bond between them - crashing both parties at the same time. "A proton is a great handshaker that works the room until it gets to where it is needed," he said.

This motif is the generic intermediate involved in passing a proton through a biological membrane. Each paired interaction forms a locally stable intermediate. In a sense, the oxygen atoms in water molecules chaperone protons between oxygen and nitrogen atoms on organic structures. For example, the primary events in trans-membrane proton pumps require passing protons through many relay steps across the cell membrane.

In earlier studies, Johnson looked only at water molecules trapping protons. This study expands the work to biologically relevant molecules that contain oxygen and nitrogen atoms. In it the researchers were able to look at how stiff the proton trap is between two molecules, and how this stiffness depends on the properties of the molecules to which the protons are attached.

"The strength with which the proton is grabbed by a nitrogen - or oxygen- containing molecule is highly affected by the environment," said Johnson. "So, we systematically changed that environment over a huge range and followed how the localization of the proton changed. We found that the way the proton is localized depends very much on the chemical properties of the atoms you are trapping it with."
Mew NMR Methods by Kurt W Zilm
LUMO Analogy among three fluorides
Argon Nanomatrix Spectroscopy by Mark A Johnson