This link http://science.time.com/2014/01/03/watch-scientists-suspend-objects-in-midair-with-sound-waves/ shows sound waves trapping materials. If not can photons be used the same way to trap a plasma for example by placing it at the intersection of the electromagnetic waves?
In space the fusion reactor can be used to power interstellar missions. The reactor can be turned off during accelerations.
What do you say about my idea?
First the trapping with sound waves:
Sound waves are transmitting energy. Similar behavior can be observed for photons, a phenomenon known as radiation pressure. However, you need reflection of the sound wave to maximize the effect. Plasma is trasparent, or semi-transpared, to sound waves in gases, even if the sound speed can be considerably different and some reflection is still possible. You can have some effect, but not sufficient to trap plasma.
The same can be said for trapping by light. This is done with a very powerful laser in inertial confinement. In this case also sound wave contribute to the compression. But the energy is very high. If you are thinking of using a laser used to trap cold atoms to confine a plasma, it is not possible. The plasma temperature is too high, and electrostatic forces are very strong, I do not think it can be done.
Just a small amendment to Gianpiero's nice answer: The laser light in inertial confinement fusion is not really used to confine the plasma, it creates a shockwave, which then ignites the plasma.
In general it should be impossible to confine a plasma just by means of radiation pressure as this kind of pressure is very low even for high energetic photons compared to the thermodyamical and electric pressure (if you think of the Coulomb force from the charges in the plasma per unit area as a kind of pressure) of a plasma.
you may use sound waves as pressure waves, and play with some kind of pressure domains which may affect your plasma.. but do not call it confinement.
This is just the plot of Morgan Freeman and Keanu Reeves' "Chain Reaction" Hollywood movie. It is unlikely to work, for the following reason. Any confinement requires a force, in order to prevent uncontrolled plasma expansion. No matter what the physical nature of the wave is like, the amount of momentum transmitted by the wave across space per unit time and unit area (i.e., the pressure) perpendiculary to the direction of propagation is equal to the flux of power transmitted by the wave, divided by the phase speed of the wave (see e.g. Feynman's Lectures on Physics). If there is total wave reflection at plasma surface (unlikely), the net confining pressure due to the wave is just twice this value. A thermonuclear plasma undergoes an expanding pressure of about 50 Atm = 5*10^6 Pa. If the confining waves are acoustic waves, as you assume, then the phase speed is the speed of sound. To fix the ideas, assume a speed of sound of 1000 m/s. Then the acoustic power flux should be 2 * 5*10^6 * 10^3 = 10^10 Watt/m^2, i.e. some orders of magnitude lower than the value of an artillery shell. Trouble is, even in purely adiabatic conditions a sound wave of 0.05 Pa (your voice) induces a heating of 40 microK, and a sound wave of 30 kPa induces a heating of 24 K. Extrapolation shows that a wave at 5*10^6 Pa induces a heating of thousands of K. And this is just a rough understatement, as wave propagation is unlikely to be purely adiabatic (strong shock waves are likely to be at hand on the plasma expansion time-scale, and strong shock waves raise entropy a lot). Such a strong heating raises the thermal conductivity of the plasma, thus spoiling energy confinement. Not to mention the impact of hydrodynamical, Rayleigh-Taylor instabilities, which occur whenever a dense, unmagnetised plasma is surrounded by a less dense, unmagnetised fluid (as in the confinement scenario you envisage). For a comprehensive review, see https://en.wikipedia.org/wiki/Bubble_fusion . Admittedly, a different point of view is hinted at in http://gizmodo.com/an-odd-hypothesis-about-bubbles-could-finally-lead-to-n-1681767423
Max,
>In space the fusion reactor can be used to power interstellar missions.
>The reactor can be turned off during accelerations.
Absolutely.
One simply (!) needs to:
a) build a viable fusion reactor
b) transport it to space
No new physics required, some intense R&D for solving the first-wall problems, and then a flotilla of heavy lift launchers. An idea as old (almost) and good as the stars themselves.
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