Slashdot is powered by your submissions, so send in your scoop


Forgot your password?
Slashdot Deals: Deal of the Day - Pay What You Want for the Learn to Code Bundle, includes AngularJS, Python, HTML5, Ruby, and more. ×

Comment Re:The real worry should be Kessler Syndrome (Score 1) 98

Just making a single important orbit permanently uninhabitable can be pretty devastating.

Imagine a small satellite in a retrograde orbit close to the geosynchronous ring. The satellite is just a big hunting rifle cartridge full of buckshot with a tiny remote controlled gas canister that can turn it into a slowly expanding cloud of ruin. It will destroy everything in that orbit within twelve hours, hitting satellites at a relative speed of 6000 m/s.

[shudder] I didn't know I was that evil.

Comment M-DISC and a media-grade fire resistant safe (Score 1) 174

Even a single copy on M-DISC in a media-grade fire resistant safe is more likely to survive the next 35 years intact and readable than the alternatives. Cloud, hard disk arrays, tapes, whatever. The total maintenance cost over this time is dramatically lower than the alternatives, too (virtually zero).

And I would not worry about availability of readers in 35 years. I don't see passive physical media completely going away. Passive media carrier that does not include electronics. There will always be a niche for that. The drives you will buy in 30 years are likely accept the same 12cm disc form we have been using for the last 35 years and be backward compatible with CD, DVD, Blu-ray, Violet-ray, UV-ray, Gen1 holographic, Gen2 quantum, Gen4 quarkstore and Gen4 planckstore disks :-)

Comment Re:Made of Unabtanium (Score 1) 120

In an HX thruster, liquid propellant is pressure- or pump-fed to a lightweight planar heat exchanger. For orbital launch, the propellant of choice is liquid hydrogen. H2 provides a vacuum Isp of 600 seconds, sufficient for a robust single-stage-to-orbit capability, at a heat exchanger temperature of only 1000 C (less than 2000 F). The heat exchanger can therefore be made of ordinary materials, rather than exotic high-temperature alloys, which allows building cheap expendable vehicles.

Kare, Jordin T. "Modular Laser Launch Architecture: Analysis and Beam Module Design." Final Report USRA (2004).

This report is about laser heat exchanger launch system but should be valid. Dr. Kare has studied both laser and microwave launch systems. A single-stage-to-orbit vehicle does not shed tanks or stages. When it reenters the atmosphere is it a big empty tub with a very low cross-sectional mass density. The temperatures it encounters are dramatically lower than a capsule or the shuttle.

In other words, this is far from being the most difficult part of the system.

Comment Let's teach them about information first (Score 1) 211

We live in a world of information. So let us teach them about information first. What is information? How has it been encoded, stored, reproduced, processed and transmitted throughout history? What is encryption? How trustworthy is a source of information? How do we assess that?

It should definitely include some material about the concept of processing information by an algorithm. I am not sure that actual coding is really for everyone - but being literate about information definitely is.

Comment Trustworthy? Gandi or PairNic (Score 1) 295 French open source geeks. They've been in the registrar business for about as long as you've been on Slashdot. Many consider it an advantage for their registrar to be outside US jurisdiction. Their terms of use and conduct in the face of legal challenges have received thumbs-up from privacy activists and lawyers.

PairNIC, operated by Pair Networks. From their web site: "Launched in January 1996 and profitable since its second month of operation...". I have hosted with them for many years and their reliability is unbeatable. If you are a US-based business you can't escape US jurisdiction anyway and probably won't mind paying a couple of dollars more.

Comment Re:Not just for the retro look (Score 2) 328

> TFA talks about the filament temperature: 60C. This is no problem.

It's "no problem" because someone has done the work to solve it. A filament has a very small surface area to dissipate heat. Air is a very poor heat conductor. Glass too. Without the helium fill gas and a sufficiently large bulb envelope area the filament equilibrium temperature for the same electric power would be much higher and greatly reduce the efficiency and lifetime of the bulb.

> Holding helium for years is easy. Sealed glass is traditional in bulb manufacturing and is sufficiently helium tight.

Again, it's easy once someone has solved it. If it were not for the legacy of incandescent bulb production techniques and facilities making this a solved problem
I am pretty sure this idea would have been dropped in favor of other LED packaging methods based on plastic and aluminum.

Comment Not just for the retro look (Score 4, Insightful) 328

I find it interesting that there are sound engineering reasons behind this shape, not just the retro look. The filament shape solves the 360 degree light distribution of most LED lamps but raises the issue of how to cool it effectively when not in contact with a heat sink. Helium has a much higher heat conductivity than air and moves the heat effectively to the envelope. Holding the helium for years without leaking is difficult requires something more gas tight than plastic. Forunately, there are many factories for glass bulbs that would otherwise be closed due to the decline in incandescent lamp sales. The technology for the glass envelope and sealed leads is a result of many years decades of development and probably would not have been worth the investment just for this purpose but these factories are already there with trained personnel and fully depreciated equipment.

Comment A story of Saint Brigid. (Score 5, Funny) 132

"A certain woman who had taken the vow of chastity fell, through youthful desire of pleasure and her womb swelled with child. Brigid, exercising the most potent strength of her ineffable faith, blessed her, causing the child to disappear, without coming to birth, and without pain. She faithfully returned the woman to health and to penance."

Was the mother of that child trying to hint something with that choice of name?

Comment Re:Monsanto (Score 1) 100

I think people may be confusing hybrid seeds with terminator seeds.

Most modern seeds are a cross between two parent lines. They are not stable and the next generation of seeds will not have the same carefully selected properties. This is not done on purpose to prevent them from being reused - it's just a property of the most effective method of generating seeds with targeted properties.

High quality open source seeds will most likely be hybrids, too. You will not be able to reuse their seeds. But the parent lines will not be kept as a guarded secret and multiple seed producers will be able to make generic versions at reasonable prices.

"If I do not want others to quote me, I do not speak." -- Phil Wayne