[QuantumDot]

I don’t know quite what it is you want but i would be willing to try.

[QuantumDot]

White graphene or hexagonal boron nitride is a insulator, can survive harsh conditions, and boron 10 can absorb neutrons.

While currently expanse like graphene which recently developed a roll to roll processing method which should really bring down its price, so it still needs research but i have read that you can tune it band gap by mechanical straining it.

Quantum dots are also some thing that seems to fit the bill for the insulator since you can tune its band gap by size, and material selection, and you can also make it into an aerogel which means that you might be able to simply have a metal aerogel combine with a metal chalcogenide aerogel to make your onion to absorb the x-rays.

[QuantumDot]

there is a design for a thermo photo voltaic device that in theory could achieve 85 percent efficiency, from what i have read it hasn’t come close to actually achieving that but there is hope that it will.

[QuantumDot]

I agree with Rezwan, i think that it should involve a number of the smaller cheaper and more radical aneutronic fusion ideas.

like:
focus fusion
magnetic target fusion
ballistic colloidal fusion
pyroelectric crystal fusion
pops polywell fusion

an hour or two hour episode on each of these would be quite interesting since i think that i have heard that all of these have achieved fusion and that all of them think that they can do boron 11 fusion and that they would call be working in 5 years or less.

[QuantumDot]

for radiation shielding they should look at demron, which claims to be able to stop a certain amount of gamma rays.

especially for vehicles or mobile DPF for power, or neutron sources

http://www.radshield.com/

[QuantumDot]

If you are interested in looking at some materials check out this site https://www.inventables.com/

its crazy some of the stuff they have listed but they also don’t have some of the other great stuff like demron, but what ever check it out.

[QuantumDot]

you could add a plasma wakefield to double or more then double the exit velocity for not much of an increase in size.

[QuantumDot]

vansig wrote: Seeing as no one has, as yet, found a way to make or contain antimatter in sufficient quantity to use it for propulsion, let’s plan to go with something that has a chance of being feasible sooner.

That may not be true. people have been able to make fairly large abouts of positrons with a petawatt laser, and some think or claim to be able to store positronium with is a positron electron pair orbiting each other for years instead by using electromagnetic fields to increase the size or there orbits so that they don’t hit one another. And with the recent production of a BEC made of positronium the accusal handling of it to do work is improving.

But its still all between 4 and 2 in the technology readiness level, and none of it is efficient or ready for practical work in space.

production of positrons
https://publicaffairs.llnl.gov/news/news_releases/2008/NR-08-11-03.html

since the dpf would produce a beam of charged particles you could place undulators there instead of to convert it to a free electron laser and maybe you could then used chirped pulse amplifiers to but it in the petawatt range

storage of positronium
http://news.nationalgeographic.com/news/2006/05/0504_060504_antimatter_2.html

bec positronium
http://www.physorg.com/news191868695.html

other sites
http://thefutureofthings.com/articles.php?itemId=33/64/
http://www.centauri-dreams.org/?p=11444
http://atomicrockets.posterous.com/?tag=antimatter

[QuantumDot]

controlling thermal emission radiation
http://availabletechnologies.pnl.gov/technology.asp?id=82

micron-gap thermal photovoltaics
http://greeneroz.net/component/content/article/5105-thermal-photovoltaics-breakthrough-by-mtpv-corp.html
http://www.greendiary.com/entry/mit-researchers-set-to-defy-carnot-limit-in-reusing-90-of-waste-energy/
http://www.energy-review.info/blog/quantum-dots-photovoltaics/

spacecraft skin
http://www.msnbc.msn.com/id/26294999/
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=WPCP_010576&use_sec=true&sec_url_var=region1&__uuid=f9d2789c-bb62-4ae4-a6d6-a0bab194394a

planks law breakdown
http://www.sciencedaily.com/releases/2009/07/090730154025.htm

check out these sites for current and upcoming technologies.

[QuantumDot]

How much would it help to increase the temperature to ~300keV and the density to about 1 atm or 760 torr?
and would it still be stable at these levels?

[QuantumDot]

http://www.msnbc.msn.com/id/26294999/

Check out this spacecraft skin

i guess that it would need a combined solar sail/ radiator so could reduce the power level.

so a DPF could be used for additional propulsion for lasers for the solar sail as well as direct thrust and isn’t a DPF suppose to be 70 percent efficient not 50.

[QuantumDot]

Pyroelectric and thermoelectric devices could be used to take some of the heat away and convert it to electricity.

[QuantumDot]

One way to cooling things that would massively reduce the use of radiators would be optical refrigeration,

“Optical refrigeration (also called laser refrigeration or anti-Stokes fluorescent cooling) is a technique for cooling a macroscopic crystal (or a piece of glass) with a laser beam. The crystal must be doped, e.g. with ytterbium or thulium ions, which are excited by the laser beam. The laser wavelength is chosen such that it is longer than the average wavelength of the resulting fluorescence. This means that the energy of the absorbed photons is lower than the average energy of the emitted photons, so that energy is removed from the crystal. Of course, it is essential that the quantum efficiency of the fluorescence is high, and that nearly all fluorescence light can leave the crystal without being absorbed, e.g. by impurities: a single absorbed photon would offset the cooling effect of many other photons.

Cooling a piece of ZBLAN glass in a “laser fridge” from room temperature down to 208 K has been demonstrated [2], and 155 K have been achieved with Yb:LiYF4 [6]. In theory, even temperatures of the order of 77 K (liquid nitrogen) should be reachable. Certain ytterbium-doped crystal materials, particularly tungstates such as Yb:KGW = Yb:KGd(WO4)2, appear to be suitable for this purpose.

Possible applications of laser refrigeration are the replacement of Stirling coolers and the like (avoiding moving parts, vibrations, etc.), but also radiation-balanced lasers, where the internal heat generation is essentially compensated by optical refrigeration.

It is instructive to consider entropy changes associated with laser refrigeration. The reduction in thermal entropy of the cooled device is more than compensated by the increase in entropy which arises from the conversion of narrow-band focused laser light into fluorescence light, which has a much higher entropy due to the many spatial modes and different frequencies involved in the emission.

See also the article on laser cooling, which deals with the cooling of microscopic particles, rather than macroscopic samples. The physical principles behind such cooling methods are rather different from those of optical refrigeration.”( http://www.rp-photonics.com/optical_refrigeration.html )

other sites to look at are
http://www.physorg.com/news183987251.html
http://encyclopedia2.thefreedictionary.com/Optical+refrigeration

[QuantumDot]

Recently some physicist have observed electrons having a negative mass before undergoing acceleration which is more or less what woodward expected which means that his theoretical mach reaction-less propulsion device might just be possible, but you would still have to power the thing and scale up it performance to meaningful levels.

various people are studying the mach drive and some have reported limited success, work is still ongoing.

electron negative inertial mass
http://www.sciencedaily.com/releases/2010/04/100412084525.htm
http://www.technobahn.com/news/Negative_Mass_and_High_Speed:_How_Electrons_Go_Their_Own_Ways_2010041200003007.html

woodward mach drive
http://www.centauri-dreams.org/?p=1324
http://en.wikipedia.org/wiki/Woodward_effect

[QuantumDot]

Well since fusion propulsion is one of the only options for interstellar flight and the DPF is about the only near term option, its worth a serious look.

the other options are light sails, antimatter catalyzed fusion, a field reversed configuration( think VASMIR only blown up to cause fusion), and pulsed detonation either with small pellets ignited with lasers or small bombs, the last option is one based on Bussards work either the polywell or the ram-scoop. And from what i have heard only the light sails can be said to be near term.

And of course you would want to test it in the solar system first with a direct flight to mars which should only be 30 days and a gravity spin around the sun but after a few years of tests you would want to try to use it for the real deal and send it to another star.

[Author]

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