Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Note: You can take 10% off all Slashdot Deals with coupon code "slashdot10off." ×

Comment Re:pros and cons (Score 3, Insightful) 316

> IF the F-35 does four different roles

But it can't do _any_ of the roles well. The tradeoffs made to accommodate all different military branches needs have played havoc with doing _any_ role well. The repair and upkeep costs are astronomical, it's a fuel glutton, it's fragile, and it's clumsy.

Comment Re:su (Score 1) 717

The settings of what to keep and preserve are optional, set in the "/etc/sudoers" file and modified heavily by the use of "sudo -s", "sudo -s -H", and "sudo -i" command line options. I recently walked through this with someone who was surprised that their ssh-agent access was lost when they used "sudo -i -u appname". to edit files as an application owner.

Comment Sudo did this better 15 years ago (Score 0) 717

"su" was replaced for almost use by "sudo" shortly after its first release in 1999, as a lightweight thorough, and fine grained replacement. Sudo's only flaw is the ability to sanity check and reject individual "included" files from /etc/sudoers.d, which makes editing them somewhat dangerous.

Mr. Pottering is, I'm afraid, insistent on replacing the entire UNIX and Linux infrastructure with a proprietary, Linux-only, sprawling and destabilized octopus that persists in breaking stable environments and stable tools.

Comment Re:Cannot scale anyway (Score 1) 366

The article you point to is very interesting, but quite sketchy: I assume they're breeding tritium from Lithium-6? That's an exothermic reaction as well, so _in theory_ it might be sustainable and address the need for fission based sources of tritium.. But since it's not actually been demonstrated anywhere, I'll remain sceptical about its practicality and scalability. In addition, this research and most other fusion leave out the energy costs of refining the _deuterium_ fuel. That's another cost in the energy budget for fusion reactors that is often left out.

Please excuse me if I seem to be presenting moving targets by raising other efficiency and cost concerns than the original: There are so _many_ places the optimistic hopes for fusion energy break down that even if several are addressed, it doesn't resolve the other factors that limit practicality and scalability of fusion based power.

Comment Re:Cannot scale anyway (Score 1) 366

Let's take a quick back of the envelope look, without wishful optimism already in force.

The net energy of a U-235 fission event is approximately 235 MeV, That of a fusion event involving deuterium and tritium is approximately 18 MeV, less than one tenth of the energy of the energies involving a single pair of atoms. The slow neutron reaction used to generate tritium from lithium itself yields roughly 5 MeV, which might be possible to harvest. If we count atom by atom, rather than by mass, U-235 still yields roughly 10 times the energy of fission. But to produce enough tritium to harvest and actually fuel a fusion reactor, let's assume that we're recovering as much as 1/10 of the fission events as usable tritium fuel. That's a _very_ optimistic number, refining nuclear materials is quite dangerous and quite wasteful.

That means relative power output of the fusion plant, at the most optimistic 100% efficiency of the fusion plant itself, of 1% of the energy output of the fission based tritium source. Even a factor of 10 improvement in any step, or a few factors of 2 improvement at several stages, leaves the fusion plant far behind the energy production of the fission plants needed to fuel it.

Comment Re:Pointless (Score 4, Insightful) 152

> The whole reason I use Uber is to find a driver with a clean car, clean clothes, good local language, good knowledge of the city, good driving skills, sane metering device, known rates and acceptable behavior.

I've been dealing with those services in an urban are lately. Good luck with "driving skills", "local language", and "knowledge of the city". I've nothing personal against Lyft or Uber's attempts to modernize and improve cab services, but they _are_ cab services. And as their numbers grow, they're running into the same problems with more employees and less skilled drivers that the cab companies do. The "real cab companies" should have been willing to invest in this approach a decade ago when cell phones and geo-locatoin first started becoming useful about 10 years ago.

Comment Could be worse, Fesora 19, Schroding"er's Release (Score 2) 46

It could have been worse. Fedora 19 was the "Schrödinger's Cat" release, and it broke number of software installation tools . Many old scripts in bash, ruby, or perl would read "/etc/issue.net" or "/etc/fedora-release", and now had to parse the Unicode content with a single quote and two text words embedded in the text. For many old, simply written shell scripts, in particular, it broke them _very_ badly.

For many of us, Fedora 19 was known as the "Bobby Tables" release. ( https://xkcd.com/327/ )

A verbal contract isn't worth the paper it's written on. -- Samuel Goldwyn