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Comment: Re:Why on the ISS? (Score 1) 159

by necro81 (#49510627) Attached to: ISS Could Be Fitted With Lasers To Shoot Down Space Junk
That was my reaction, too: what advantage does putting it on the ISS get you, balanced against any added costs / difficulties / constraints, compared to a standalone satellite? On the plus side, you have an abundance of solar power available, along with cooling loops, attitude control, etc. What is more, you may be able to make use of astronauts to provide debug and repair capabilities. On the other hand, you are limited to the ISS' orbital inclination and altitude, and probably a variety of added design constraints and safety standards.

Comment: Re:Nice (Score 5, Informative) 78

by necro81 (#49477535) Attached to: New Horizons Captures First Color Image of Pluto and Charon

the probe is not designed to transmit while aiming its instruments (to save money; contrast with Voyagers)

Voyager has most of its instruments, including the cameras, on a movable platform. This allowed the positioning of the spacecraft and its high-gain antenna (the dish) to be decoupled from the positioning of the sensors. That made it very versatile and capable but, as you mentioned, more expensive. It also increases technical risk. What if the scanning platform jams up? (Some instruments could end up forever pointed back at the spacecraft! There are only so many multi-spectral selfies you would ever want to have.)

New Horzions is, for all intents and purposes, a single solid body. For 98% of its operational life, it's spin stabilized with its dish pointed squarely back towards Earth. That won't suffice for the intensive observations it was built for, so it will stop spinning and tilt itself this way and that to point its sensors at Pluto during its close encounter. Of course, when it is tilting this way and that, it is no longer pointing its main dish at Earth, so there can't be substantial communications. There is still the low-gain antenna, which is much less directional, which will allow for continuous commanding and telemetry, but has too little bandwidth for much science data to be beamed back. (more info here)

Comment: Re:Going off the grid completeletly is stupid (Score 1) 280

by necro81 (#49452707) Attached to: The Myth of Going Off the Power Grid

Why not use the grid as a reservoir..like a battery or capacitor?

The primary reason is because there is no appreciable storage or capacitance in the grid. Every watt that is generated is balanced by a watt of consumption, second to second. That is what the purpose of an Independent Service Operator (ISO) is - forecasting supply and demand on a minute- and hour-basis, and ensuring that balance is maintained. When instantaneous supply does not match demand, the grid becomes unstable. This usually first manifests as frequency drift - it'll rise or fall from its nominal 60 Hz (50 Hz in other countries), followed by voltage drift. Eventually you get bad things like failing transmission lines and transformer fires.

There is some flexibility on both the supply side ("dispatch" power that can be ramped up very quickly) and some on the demand side (certain large users - factories and such - can temporarily throttle their usage in exchange for payments. Residential customers can have their air conditioners temporarily switched off by the utility - again in exchange for payment). There is a small bit of storage - pumped water hydro, flywheels, batteries - but it's pretty localized, and minuscule compared to the total energy utilization. There is also some dispatchable demand to take up excess supply - ice generation and hot water generation - but that, too, is pretty small peanuts.

Some efforts have been made to make a bigger business out of grid-tied storage, but they haven't been ringing successes just yet due to the large capital costs. If someone could cut the capital cost of storage in half, you could expect to see more large-scale deployments, probably in conjunction with intermittent renewables. This may well be Elon's master plan.

Comment: Re:The main challenges... (Score 3, Informative) 142

by necro81 (#49421695) Attached to: Stanford Develops Fast-Charging, Stable Aluminum Battery

While that's almost perfect as a replacement for lead-acid batteries, it's not enough to replace two AA batteries (2.4v/3v) or one lithium-ion (3.6~3.7v)

I would argue that the cell voltage is largely irrelevant. If you need to put more cells in series, it doesn't matter much. What matters more is the energy density - if you end up with twice as many cells (to get voltage equivalent to li-ion), but have equal or better energy density (Whr/kg or Whr/L) at equal or better cost, then you still have a win.

Comment: Re:Just what we need... (Score 1) 142

by necro81 (#49421655) Attached to: Stanford Develops Fast-Charging, Stable Aluminum Battery

Surely washing clothes by hand cuts down on energy usage :)

That may or may not be the case. It depends heavily on the energy investment for that water - how much energy went into getting it, purifying it, distributing it, and heating it. Next, consider the amount of soap you are using. A modern high efficiency washing machine uses very little soap per clothing article. Human hand washing (clothes or dishes) tend to oversoap, which is wasteful on its own, but also requires more water to rinse out. Finally, consider the energy used for drying the clothes. Hand-washing is usually associated with line-drying, but you might still be using an electric dryer.

If you are hunched over a creek, scrubbing your clothes on a rock with freezing, chapped hands, followed by line-drying in the sun, then you clearly are doing better than the status quo. But if you are filling a great big tub multiple times (wash, rinse, etc.), with water that came from oil-fired desalination plants and heated to a balmy 30 C, then using an electric dryer on high, "hand washing" will clearly be more energy-intensive.

Comment: Re:Woop Di Do Da! (Score 4, Interesting) 265

5% of the total energy use is still commendable though, especially in state that consumes as much energy as California

It is worth noting that California is the #2 electricity consuming state in the nation (behind Texas), but has the lowest per capita consumption in the country, roughly half the average per capita consumption of the entire U.S.

Comment: Re:Competing with government-sanctioned monopolies (Score 1) 185

the utility power is a "natural monopoly" and how, therefor, it can not be subject to competition...

I would take a more nuanced approach to it. It's not that it cannot be subject to competition, it's more that it is unreasonable to expect competition to magically appear - as one would expect in other markets - due to the impracticalities (i.e., having two sets of power lines) and the high cost to entry.

Comment: Re:UV sensitivity (Score 2) 95

I take it you've never worked with SLA resins and parts then. Mass-produced plastic parts have varying degradation rates in the sun. Many have UV stabilizers in them that provide them with substantial life (many years) even in direct sunshine. SLA parts, in my experience, have a useful life measured in weeks if allowed to be in the sun. Even sitting around in an office environment, SLA parts will degrade over months.

Comment: Re:projecting UV images from below liquid resin? (Score 1) 95

So I wonder how this UV projector doesn't cause solids to form inside the vat if in fact this projector can cause plastic to solidify as it is being removed from the vat with liquid resin.

Or you could read the article to find out the answers to your questions.

Comment: Re:Wasteful? (Score 1) 95

by necro81 (#49161147) Attached to: Ikea Unveils Furniture That Charges Your Smartphone Wirelessly
Well, to quote the summary: "Ikea's introduction of wireless charging functionality on some of its new furniture heats up the battle for a global wireless charging standard"

Although you can get up into the 80% range (short distance between emitter and receiver, good axial alignment, well-tuned resonance frequencies, and proper shielding), you are more likely to be in the 50-75% efficiency range. That's for the inductive portion; there is also a loss in converting the 120/220V power from the wall. [I speak from professional experience developing a Qi-charged medical device. It was a good solution for the problem, as it allowed the case to be fully sealed, but turned me off the idea of using it for everything that needs charging.] For 5-10 W of actual charge power in the device, your losses from grid to device will be close to that amount This is about as bad as the 50-60 Hz wall wart transformers that we have recently gotten away from.

Comment: Re:is it an engine or a display model? (Score 3, Informative) 58

by necro81 (#49149537) Attached to: Researchers Create World's First 3D-Printed Jet Engines
3D-printed metal has been used for quite a while in some of the lower-performance stages (lower pressure, lower temperature). Examples here. The key benefit is that they are able to integrate convoluted channels within the structure for cooling or mixing. You can also reduce weight by taking away significant internal volume, replacing it with ribs or a sparse matrix. I wouldn't go so far as to say that it's mainstream, but it's close.

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