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Comment: Re:Funny Timing (Score 1) 59

by Dan East (#48431349) Attached to: The Nintendo DS Turns 10

I just fired up an old beat up micro I had laying around last week. At the time it was released, the micro had one of the highest DPI color screens I'd ever seen. Still the SP is my favorite. It was the first Gameboy of any kind with an actual backlit screen, and it was beautiful to behold. Games looked so vibrant and clear compared to the Gameboy Advanced, that they almost didn't event seem like they were the same games. The clamshell design was also new and suited to the device perfectly. When closed it wasn't much larger than the screen, and the cartridge fit flush into the device - it was nice and compact when closed. It was also the first gameboy with an integrated rechargeable battery, and it seemed to last for ages. Really, the SP was the most revolutionary single portable gaming device produced by Nintendo. The one and only thing the SP lacked, which was due to the CPU / cartridge hardware being designed well before the SP came out, was a hibernate / suspend type capability when closed (it still seems to me they could have managed that somehow).

Comment: Owning stock (Score 2) 194

by Dan East (#48431299) Attached to: Harvard Students Move Fossil Fuel Stock Fight To Court

Is it common stock or non-voting? If common stock then I would think they would want the school to have a vote in what the energy companies do. Regardless, if it's a wise investment that is generating profit, then it really doesn't matter. It's not like selling the stock is going to hurt the company or the stock value. I guess some people just can't sleep at night over these kinds of things.

Comment: Re:With a RTG, it couldn't have got to the comet. (Score 5, Interesting) 480

by Dan East (#48423627) Attached to: What Would Have Happened If Philae Were Nuclear Powered?

No matter how you build them, nuclear Radioisotope Thermal Generators are heavy.

That's totally inaccurate. I went into details about this a couple days ago when Philae was discussed here. In that case someone said that because it took 10 years to arrive at the comet, an RTG couldn't have been used. I'll just copy/paste my other post since it already covers your statement.

The lander only uses 32 watts of power. The MMRTG used in Curiosity provides 125 watts of power initially, and 100 watts after 14 years. The mass of that specific RTG (the MMRTG, 45kg) would be too great for use in Philae, but then it also produces 3 times more energy than needed (even after 14 years). RTGs have been made in many sizes for many different applications, so it would simply have been a matter of designing an RTG that produces 40-45 watts of power after 10 years.

However, one of the main uses of the 32 watts of power required by Philae is just to keep the batteries warm so they don't fail. RTGs produce more "waste" heat than they do electricity. For example, the MMRTG used in the Curiosity rover produces 2 kW of heat, of which 125 W is converted to electricity. The extra heat is used to keep the various temperature-sensitive parts of the rover nice and warm so they don't fail. With Philae, a good portion of the 32 watts of the solar power it requires is just to keep the battery warm. So if an RTG were used, it wouldn't even need to produce 32 watts of electricity since it can keep the lander warm directly.

Looking at the mass and wattage produced, the RTGs ("SNAP-19") in the Pioneer probes would have been just about perfect for Philae. They produce 40 watts of power and weigh 13.6 kg. Philae's current electrical system weighs 12.2 kg, so that's at least in the ballpark. The RTGs on the surface of the moon, as manually placed by Apollo astronauts's would have been a bit heavy at 20 kg. One of those RTGs was still producing 90% of its power after 10 years.

The SNAP-9A used in the Transit 5B-2 navigation satellite launched in 1963 weighed 12.3 kg and produced 25 watts of power. That looks about like a perfect fit for Philae, and I'm sure more efficient thermocouplers are available today that could further reduce the weight.

Comment: Physical constraints (Score 1) 315

I know they were looking at this in a very theoretical way, but in the real world there are of course physical constraints. We already have "robots" that kill people autonomously, in the form of guided missiles, cruise missiles and smart bombs. However, I think in this case we're talking about identifying an object as a human, and then killing that human. The most simple form of this, which is what we're likely to see in use next, is an autonomous gun turret. However, with any sort of weapon of this kind, it is very easy to apply physical constraints. For example, a gun turret could be mounted to protect the no-man's-land in a specific perimeter of a military base. It would be designed and mounted so that it cannot physically rotate 360 degrees, for example, and thus could not target friendly soldiers inside the base. Whenever a person needed to go out into the zone the weapon patrols, the weapon would be physically deactivated - removing power, a physical block preventing it from moving, the removal of ammunition, etc.

Now if we're talking about free-ranging robots than go out and kill, then that's a bit more complex, although as long as humans are the ones creating the robots, we can always build in physical constraints. For example the ability to disable power to the robot using a circuit that is totally external to and in no way connected to the robot's actual logic or control.

Comment: Re:RTG (Score 4, Informative) 87

by Dan East (#48399179) Attached to: After Four Days, Philae Team Gets to Rest

It took ten years to get the Rosetta mission to the comet. By then a RTG would be fairly depleted too.

That isn't a legitimate reason to not use RTG for Philae. The lander only uses 32 watts of power. The MMRTG used in Curiosity provides 125 watts of power initially, and 100 watts after 14 years. The mass of that specific RTG (the MMRTG) would be too great for use in Philae, but then it also produces 3 times more energy than needed (even after 14 years). RTGs have been made in many sizes for many different applications, so it would simply have been a matter of designing an RTG that produces 40-45 watts of power after 10 years.

However, one of the main uses of the 32 watts of power required by Philae is just to keep the batteries warm so they don't fail. RTGs produce more "waste" heat than they do electricity. For example, the MMRTG used in the Curiosity rover produces 2 kW of heat, of which 125 W is converted to electricity. The extra heat is used to keep the various temperature-sensitive parts of the rover nice and warm so they don't fail. With Philae, a good portion of the 32 watts of the solar power it requires is just to keep the battery warm. So if an RTG were used, it wouldn't even need to produce 32 watts of electricity since it can keep the lander warm directly.

Looking at the mass and wattage produced, the RTGs ("SNAP-19") in the Pioneer probes would have been just about perfect for Philae. They produce 40 watts of power and weigh 13.6 kg. Philae's current electrical system weighs 12.2 kg, so that's at least in the ballpark. The RTGs on the surface of the moon, as manually placed by Apollo astronauts's would have been a bit heavy at 20 kg. One of those RTGs was still producing 90% of its power after 10 years.

Regardless, the fact that the Philae mission would last more than 10 years is not a reason to not have used RTG. Other issues (obtaining the radioactive material, environmentalists throwing a fit, inexperience of the ESA with that kind of power source, delays in production, etc) certainly dictated that an RTG wasn't used, but it was most certainly not due to any technical limitation.

Comment: Good news? (Score 3, Interesting) 127

by Dan East (#48365009) Attached to: FCC Confirms Delay of New Net Neutrality Rules Until 2015

This is probably good news. Obama makes a public statement urging the FCC to step in and enforce net neutrality, and the FCC suddenly delays a decision they were about to make. That means the decision had already been made and it was that the FCC was not going to intervene. Now they are reconsidering and thus they want more time to figure out what all Obama's request entails.

Comment: Re:no dimocrats (Score 1) 551

by mcgrew (#48358951) Attached to: In this year's US mid-term elections ...

You know, danbert8, you would come across as far less ignorant if you googled first. FYI, that link leads you to information about federal taxes that go to schools. And you don't know that the INTERSTATE highway system was built by the federal government under Eisenhower, and that all the states get federal money for roads and highways?

Comments like yours is why I've spent a lot less time at slashdot lately. You should be ashamed of yourself.

"Ahead warp factor 1" - Captain Kirk

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