New technique may allow lasers to rapidly heat material to temps hotter than the sun.

[Aethon]

http://phys.org/news/2015-11-lasers-rapidly-materials-hotter-sun.html

This could mean that controlled fusion is a mere 25 years in the future.

[Bill Phil]

It's always 25 years away....

Seems promising. Hope it actually leads somewhere.

[K^2]

It's always 25 years away....

No, it used to be fifty. Then it was ten for a while. We've only leveled off on 25 in the last 20 years or so.

[Bill Phil]

No, it used to be fifty. Then it was ten for a while. We've only leveled off on 25 in the last 20 years or so.

Exactly, the last 20 years. That's forever. That's always.... *shifty eyes*...

Nothing before that matters to anyone today, to be honest...

But I do hope fusion becomes a real thing. I think that it's going to be doomed to being useful only at large scales.

[fredinno]

Exactly, the last 20 years. That's forever. That's always.... *shifty eyes*...

Nothing before that matters to anyone today, to be honest...

But I do hope fusion becomes a real thing. I think that it's going to be doomed to being useful only at large scales.

Only if we could get LFTR online, in the near term (in a decade)...

[K^2]

But I do hope fusion becomes a real thing. I think that it's going to be doomed to being useful only at large scales.

Quite likely. So we're still going to need to figure out good energy storage if we want to use all that energy for something we're not doing with it now. I still have high hopes for nuclear isomer energy. If someone can figure out a reactor that produces necessary isomers in large quantities without costing too damn much, maybe we can start building flying cars and maybe even electric SSTOs finally.

[SomeGuy12]

[quote name='K^2']Quite likely. So we're still going to need to figure out good energy storage if we want to use all that energy for something we're not doing with it now. I still have high hopes for nuclear isomer energy. If someone can figure out a reactor that produces necessary isomers in large quantities without costing too damn much, maybe we can start building flying cars and maybe even electric SSTOs finally.[/QUOTE]

How does nuclear isomer energy help with this? A quick perusal of wiki didn't lead to any answers as to whether

1. Can you control the rate of energy release? If it's uncontrolled decay, like RTGs, it doesn't work for flying cars or SSTOs because the reaction can't be stopped (such as when the car lands or the SSTO reaches orbit and needs to reduce heat load)

2. Does it always release gamma rays and neutrons? If yes, then the mass of shielding and the danger makes it unfeasible.

[Bill Phil]

[quote name='SomeGuy12']How does nuclear isomer energy help with this? A quick perusal of wiki didn't lead to any answers as to whether

1. Can you control the rate of energy release? If it's uncontrolled decay, like RTGs, it doesn't work for flying cars or SSTOs because the reaction can't be stopped (such as when the car lands or the SSTO reaches orbit and needs to reduce heat load)

2. Does it always release gamma rays and neutrons? If yes, then the mass of shielding and the danger makes it unfeasible.[/QUOTE]

I think it's the nuclear batteries. I think of Fallout, but... That's me. Like an RTG, but I guess more energy? Or more of it can be released at a given time?

[Hcube]

I was never fond of the laser-induced fusion technique... A tokamak seems like a better way of doing it. But if this new laser is as effective as it is said to be, maybe the LMJ project could get on the same level as ITER and Z-machine... My favorite is ITER ^^ that's the one project that seems to have the best chances of making real big progress

[quote name='SomeGuy12']How does nuclear isomer energy help with this? A quick perusal of wiki didn't lead to any answers as to whether

1. Can you control the rate of energy release? If it's uncontrolled decay, like RTGs, it doesn't work for flying cars or SSTOs because the reaction can't be stopped (such as when the car lands or the SSTO reaches orbit and needs to reduce heat load)

2. Does it always release gamma rays and neutrons? If yes, then the mass of shielding and the danger makes it unfeasible.[/QUOTE]

I'm no expert in this (not at all) but :
1)I'm pretty sure stable isotopes are a thing, so no decay and you could get the energy back from nuclear reaction
2)i don't think it has to, AFAIK some transmutations are "pure" and don't release gamma or neutrons. (And others particles are pretty easy to stop)

EDIT : That's not how it works. See below Edited November 17, 2015 by Hcube

[K^2]

[quote name='SomeGuy12']1. Can you control the rate of energy release? If it's uncontrolled decay, like RTGs, it doesn't work for flying cars or SSTOs because the reaction can't be stopped (such as when the car lands or the SSTO reaches orbit and needs to reduce heat load)

2. Does it always release gamma rays and neutrons? If yes, then the mass of shielding and the danger makes it unfeasible.[/QUOTE]
There is no fission. The decay is from an excited state to a ground state. The only radiation released is gamma, which is easy to shield from. The only radiation that's really hard to shield is neutron, which isn't released, since you don't change the isotope. And yes, you can control the decay rate. That's the whole point.

So lets go over this again. 1) Easy to shield. 2) Releases energy on demand. 3) Long shelf life (~30 years half life). 4) Energy density approximately 10,000 times of chemical fuels.

Unfortunately, current costs are closer to million times higher than these of chemical fuels, making it impractical for pretty much any application. But there have been some developments in greatly reducing these. In other words, don't hold your breath just yet, but it's the sort of technology that might be coming in the next few decades.

[SomeGuy12]

[quote name='K^2']There is no fission. The decay is from an excited state to a ground state. The only radiation released is gamma, which is easy to shield from. The only radiation that's really hard to shield is neutron, which isn't released, since you don't change the isotope. And yes, you can control the decay rate. That's the whole point.

So lets go over this again. 1) Easy to shield. 2) Releases energy on demand. 3) Long shelf life (~30 years half life). 4) Energy density approximately 10,000 times of chemical fuels.

Unfortunately, current costs are closer to million times higher than these of chemical fuels, making it impractical for pretty much any application. But there have been some developments in greatly reducing these. In other words, don't hold your breath just yet, but it's the sort of technology that might be coming in the next few decades.[/QUOTE]

As I understand it, gamma is actually really hard to shield against. [URL="https://en.wikipedia.org/wiki/Radiation_protection"]Wiki[/URL], on radiation shielding, says you need 1 centimeter of lead to cut gamma in half. So if the exposure rate off a high end nuclear reaction, enough to roar on engine thrust into orbit, is a lethal dose in 10 seconds 10 meters away, you need to halve it an awful lot of times to get to acceptable dose rates.

And you can't fly to orbit if you have to have 30 centimeters of lead all the way around you engine. This is especially bad for flying cars, because there is severe danger if you have containment failure (after the aircraft crashes) and you have to shield from all angles because there are people underneath. (I assume you intend for the flying cars to drop people off on rooftops, etc)

Unless you know something about gamma ray shielding I don't, it's one big nope. No way, ever, can humans safely use something like this. Maybe if we were radiation resistant cyborgs with electronic brains that can resist circuitry damage via digital error correction or be replaced when we take radiation damage, but not flesh and blood primates.

Frankly, aneutronic fusion sounds more plausible. The primary reaction doesn't produce any gamma rays or neutrons at all (side reactions do), and the fuel is hydrogen + boron or hydrogen + lithium. Nothing exotic. Ironically, flying cars and SSTOs still don't make sense - the fusion reactor, being a big honking pile of superconducting magnets and electric grids and vacuum layers, is too heavy. Power output scales nonlinearly with bigger reactors because your containment systems act on the surface of the fusing plasma, and so larger reactors need proportionally less magnet mass, etc.

So you might be able to plausibly make a flying ship that could stay airborne for years on engine thrust, but not a flying car. The engines would be superconducting lift fans, and the fusion reaction would produce electricity by collecting it from the moving charged helium atoms that are the main product. Much easier to get power out than from gamma rays, and the conversion apparatus would be much lighter.

Yeah, it might resemble the helicarrier, except it would probably be much more lightly built - thin aluminum and lightweight internal structures, not the thick plates of steel and heavy interior construction a naval vessel uses - and the lift fans would have to be proportionally a lot larger. Also, there would need to be at least 8 or more lift fans - especially if you intend to fly for years, as you need to be able to fly with 1-2 of the fans not running.

Still not an SSTO. To do that, you need to beam power from the ground, using lasers or microwaves. Keep the fusion, fission, or just gas turbines on the ground, leaving the spacecraft light. Edited November 17, 2015 by SomeGuy12

[Hcube]

Gamma is not the easiest to shield from, but it all depends on the energy of particle. Saying that the half attenuation thickness for gamma is x cm of y element is nonsense. (Maybe that's the thing we know about gamma that you don't know haha ^^ wiki is good but full of imprecisions)

I don't know what energy the gammas we talk about have, but for low energy gamma rays the half attenuation thickness of leader is a few millimeters at most. It's usually accepted that reducing 1000 times the energy flux is enough to neglect it in these conditions, so that's about 10-15mm of lead--> the amount of gamma photons will be reduced by a factor of 1024.
I don't enough about the subject to give an opinion about the test of your post, but that's about the first part : no problem with radiation provided the transformations emit low-energy gamma rays. Edited November 17, 2015 by Hcube