Group items tagged

In order to overcome the communication blackout problem suffered by hypersonic vehicles, a matching approach has been proposed for the first time in this paper. It utilizes a double-positive (DPS) material layer surrounding a hypersonic vehicle antenna to match with the plasma sheath enclosing the vehicle. Or in more easy language, basically one provides an antenna as capacitor, in combination with the plasma sheath (an inductor), they form an electrical circuit which becomes transparent for long wavelength radiation (the communication signal). The reasons is that fluctuations are balanced by the twin system, preventing absorption/reflection of the incoming radiation. Elegant solution, but will only work on long wavelength communication, plus I am not sure whether the antenna needs active control (as the plasma sheath conditions change during the re-entry phase).

There we go: Deep Learning predicts disruptions in plasmas. The paper related to this article is here: https://arxiv.org/abs/1802.02242

Sterilizing food with solar wind??

Funded!!!

"Because, quite simply, we think ours will be better!"

"Right hand rules!"

I am also looking into this idea since some time and it seems NASA is already ahead, awarding two contract to investigate magnetoshell aerocapture. This could be interesting for probes that want to enter eg Marsian atmospheres at relatively high velocity. Or for multiple re-entry s/c at Earth. The idea of the experiment, The satellite will carry a copper coil, powered by a lithium-ion battery, that generates a magnetic field around the probe. As it descends, the spacecraft will eject a small amount of plasma. This gets trapped in the magnetic field, creating a protective bubble that stops air molecules colliding with the craft and producing heat.

A few years back Mimmo has worked on this, rather from the theory side if I remember well ...

The power requirements for such a thing must be HUGE!

More developments in the laser filamentation community. Makes me wonder again about Christophe's ideas for a space-formed filament as new and efficient microwave waveguide.

A 60-year-old theory about the structure of the magnetic fields that surround Earth has been confirmed directly for the first time. The lead author of the paper is an undergraduate student who invented a way to view the Earth's magnetosphere in three dimensions.

Protons, neutrons melt to produce 'quark-gluon plasma' at RHIC .... hot stuff

posted already further down

An exhaustive overview of all possible advanced rocket concepts, eg.. "As an example, consider a photon rocket with its launching mass, say, 1000 ton moving with a constant acceleration a =0.1 g=0.98 m/s2. The flux of photons with E γ=0.5 MeV needed to produce this acceleration is ~1027/s, which corresponds to the efflux power of 1014 W and the rate of annihilation events N'a~5×1026 s−1 [47]. This annihilation rate in ambiplasma l -l ann corresponds to the value of current ~108 A and linear density N ~2×1018 m−1 thus any hope for non-relativistic relative velocity of electrons and positrons in ambiplasma is groundless." And also, even if it would work, then one of the major issues is going to be heat dispersal: "For example, if the temperature of radiator is chosen T=1500 K, the emitting area should be not less than 1000 m2 for Pb=1 GW, not less than 1 km2 for Pb=1 TW, and ~100 km2 for Pb=100 TW, assuming ε=0.5 and δ=0.2. Lower temperature would require even larger radiator area to maintain the outer temperature of the engine section stable for a given thermal power of the reactor."

The problem is not achieving a high energy density, that we can already do with nuclear fission, the question however is how to confine or harness this power with relatively high efficiency, low waste heat and at not too crazy specific mass. I see magnetic confinement as a possibility, yet still decades away and also an all-or-nothing method as we cannot easily scale this up from a test experiment to a full-scale system. It might be possible to extract power from such a plasma, but definitely well below breakeven so an additional power supply is needed. The fission fragments circumvent these issues by a more brute force approach, thereby wasting a lot of energy for sure but at the end probably providing more ISP and thrust.

Sure. However, the annihilation based photon rocket concept unifies almost all relevant drawbacks if we speak about solar system scales, making itself obsolete...it is just an academic testcase.

ESA Science & Technology: A leap forward in probing magnetic reconnection in space: Magnetic reconnection is a fundamental physical process in the Universe, playing a major role in various phenomena such as star formation or solar explosions, but also preventing plasma confinement in fusion reactors on Earth. However, a lack of precise measurements at the heart of this physical process prevents a full understanding of this phenomenon.

"chances are that if 700 passengers are flown annually, up to 10 of them might not survive the flight in the first years of the operations." most remarkable also the question who is to blame if a dead and burned space tourist corps comes crashing down from the sky into your car.

This calls for some we serious simulations by the Petkow code it seems to me ...

I still would need some serious input data...

First experimental study of laser filamentation in the mid-IR.

a point called plasma/fuel break-even is reached where the energy released is higher than the power absorbed by the pellet. Of course, to produce 192 high power lasers does also have an efficiency. Thats why 'machine break-even' or even 'grid break-even' is more important and still quite a long way off. It does show that laser fusion is catching up quickly, although with serious bumps along the road.

Can we have one?

They say they create 2 GeV electrons in a very small setup. However the laser they use is more than 10 meters in length. Still a really nice result.

Compared to a 27km circumference this is major achievement and it is indeed already foreseen that future colliders will include this technology as beam fillers and pre-accelerators at some point. The technique is quite elegant and a lot more energy efficient. Nevertheless, there are also thoughts that future particle colliders might actually go towards space and study collisions orginating from extremely energetic cosmic particles

Do you know this one ? (no time to go through the bookmarks...)

They just got 1.7 million euros from the EU "to build the laboratory prototypes of the key components of the electric sail": http://en.ilmatieteenlaitos.fi/press-release/121643

very interesting info indeed!!

is this just another cold fusion crap or something we could have a closer look at .... still not clear to me ... anybody?