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User: Xandu

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Comments · 89

  1. Re:I met this guy. on BLAST Telescope About To Launch From Antarctica · · Score: 4, Informative

    It also had a two-meter mirror, but this one was made out of glass, (instead of aluminum) cost a million dollars, and shattered on takeoff.

    Well, it did have a two-meter mirror, and did cost $1 million. But it was made of carbon-fibre, and did not shatter. Yes, the launch was a little rought, and yes it didn't work perfectly at float, and yes there was damage to it when we recovered. But was that due to takeoff, landing, or both? I'm sure it was a little of both, but how much damage from launch we'll never know.

  2. Re:editing flaw in the webcam stream... on BLAST Telescope About To Launch From Antarctica · · Score: 2

    Well, the webcam has long been turned off, as the launch was about 12 hours ago. The balloon only takes about 3 hours to get to float (maximum altitude), so it is only a tiny dot the webcam now.

  3. Re:A good electric Car. on Capacitors to Replace Batteries? · · Score: 1

    The best internal combustion engines get 50%. Another up to 50% or so is lost in the drivetrain, transmission, differential, etc. I assumed the worst case for an electric car, in that it is 'traditional' with the electric motor replacing the gas engine (all the rest the same) so this factor doesn't matter. I didn't bother with newer (but still maturing) designs, like electric motor in the hub of the wheel etc., which may have much higher total efficiencies (by getting rid of the drivetrain/transmission altoghther).

  4. Re:A good electric Car. on Capacitors to Replace Batteries? · · Score: 1

    So to clarify, I did dislexify the price, and I needed to multiply by 80% efficiency for the electric engine, not divide, so we get $1.45.

    Better than I thought.

  5. Re:A good electric Car. on Capacitors to Replace Batteries? · · Score: 1

    Oops, you're right. My dyslexia coupled with the early morning screwed things up. But it's close.

    Oops was brought to you be erasers. Don't make a mistake without them.

  6. Re:A good electric Car. on Capacitors to Replace Batteries? · · Score: 1

    The second challenge there would be a power infrastructure capable of supporting many thousands of fast recharges like that.

    Good question. Let's see. First, how much energy does a car use? (Warning, I'm using estimates geared towards someone in the US. Your milage (literally) may vary).

    For a 400 mile trip, and 20 miles per gallon, we need 20 gallons of gas. Gas has 131 MJ/Gallon, and engines are almost 50% efficient, so that's 20 gallons x 131 MJ/gallon * 50% = 1310 MJ. Electric engines are much more efficient, at about 90%, we'll say 80% to be conservative. So we need 1310 MJ/80% = 1637.5 MJ. Let's say we want this recharge to take 5 minutes, so it's on the order of a fuel fillup.

    That's about 5.5 MW. Damn, most places couldn't do one charge. So, let's say you have some heavy duty hookups, capable of 200 amps at 400 volts (200 amps choosen so your cables aren't so bulky they're too hard for a single person to hook up to a car, and 400 volts so you don't need to worry too much about arcing and the such). Thats nearly 5.75 hours. A long time if it's in the middle of your trip, but ok for an overnight kind of charge, and at a power level not much more than most homes are capable of providing. Proving that we not only need a better power infrastructure (at least at 'gas stations'), but new ways to safely (and temporarily) connect high voltage/current to a car and then disconnect when done.

    Also, at an average price of 10 cents per kWh, it's not that far off current fuel prices, at $2.75 / gallon equivalent.

  7. Re:Runway Lengths on One REALLY Long Runway for Rent · · Score: 4, Informative

    In fact, the higher you go in elevation, the longer runway planes need. The longest runway at Denver, for example, is 16,000 feet.

  8. Re:"1U?" on Supermicro Announces Quad-Opteron 1U Motherboard · · Score: 1

    If, on the other hand, you use Google to search for 1u, the very first link gives a nice, detailed explanation on exactly what 1U means.

    Are you feelin' lucky? Well, are you? Punk!

  9. Re:totally disagree on On the Matter of Slashdot Story Selection · · Score: 1

    the whole point of something like slashdot is that if you give many people a small incentive to provide others with useful/interesting information, people will get the best content very quickly.

    Yes.

    Beatles Beatles is a great example of this. apparently his or her major concern is promoting a fairly pointless website about George Harrison. in order to do this he spends major amounts of time finding interesting news stories and submitting them to /. for YOU to read. his only reward is a link to his website - at no cost or damage to you whatsoever.

    Almost. And I'm not arguing that he shouldn't get the link, only that he should get only partial benefits from the link. People on slashdot will still see it; bots (webcrawlers) won't.

    And there was cost and damage to me (in this case). The discussion about the article was partially sidelined by discussion on BeatlesBeatles, the George Harrison website, and conspiracy theories linking them with slashdot.

    without the submitter link, the balance would tip in favour of those who want to make the front page either because they are spamming the links in the article itself (eg Roland Piquepaille) or to push some agenda.

    I still argue that the other benefits (listed in my post above) are (and should be) sufficient to get decent articles.

    If I carry your argument over to the comments, I would think that everything would be spam, self-serving, and/or trolls. Sure, slashdot gets a lot of that, but moderation and karma keep it at bay (at least to a certain level). But there is good discussion on slashdot for little reason more than to have good discussion; shouldn't the same hold true for submissions?

    some big stories appear on a whole bunch of news sites in a short space of time, and presumably get submitted here multiple times. it's the ones which are only submitted once, and don't appear many other places, that are the slashdot gold. and hence the obsessive submitters make a big contribution to the magic. (also, i would guess, ones who obsess a particular topic, and submit quite a few stories about say, heatsinks until once in a while an genuinely interesting heatsink story comes along.)

    Yes. But I still believe that the other submitter benefits are enough to keep the submissions coming. Good ones, too. Maybe BeatlesBeatles will stop, as he just want's the PageRank, but I doubt it. I'm sure he gets alot of clicks from slashdot users, and if you're posting to slashdot, that should be enough.

  10. Re:There is an issue here you didn't address. on On the Matter of Slashdot Story Selection · · Score: 4, Interesting

    It's possible that **BeatlesBeatles free time (to spend submitting slashdot stories) and ScuttleMonkey's shift at manning the slashdot submission bin happen to line up. (I couldn't really check, as I don't know what **BeatlesBeatles uid/exact username is)

  11. Re:A simple suggestion: on On the Matter of Slashdot Story Selection · · Score: 1

    Use nofollow for all submitter links. Period.

    Slashdot doesn't need to endorse links that aren't part of the article, and if the link is relavant to the article, it should be in the article, not the submitter's name.

    People shouldn't submit to slashdot to improve their personal search engine ranking. The (geek) noteriety and/or 10 karma points (if it's still 10, I have no idea since we can't see the numbers anymore) and/or pride should be enough. Having your link appear is part of the (geek) noteriety, and shouldn't include slashdot's PageRank as part of it.

  12. Re:Vacuum Sweeper on Mark Newport's Knitted Heroes · · Score: 1

    The quickies were awesome. Only Taco would post them, and they were just a big collection of random stuff submitted to /. that couldn't deserve their own articles, but en masse, is worth posting. Often humorous, always full of links. Those were the days (I, like you jawtheshark, read slashdot long before registering).

    When I pulled up slashdot, I saw the ol' quicky icon and was overjoyed, but as I scrolled down, SkuttleMonkey made me sad. And mad. SkuttleMonkey needs to learn, this is slashdot. Dupes I can tolerate (somewhat, ok, barely), but bait and switch with the quicky icon? How dare you?

    Bring back the quickies, damn you!

  13. Obligitory Wikipedia Link on Technology Behind Plasma Displays · · Score: 5, Informative

    Of course, you can get all this (and more) at Wikipedia's Plasma Display page.

    [I realize this is probably karma whoring, but I hate it when there's only one link in summary and it doesn't even have much info, and is littered with ads, and you have to look at 3 pages to get the whole article. That and run on sentences.] ;-)

  14. Re:CPU power consumption on Harvesting & Reusing Idle Computer Cycles · · Score: 1

    It varies widly (wildly) in the States. New York is like 19 cents, Kentucky is about 4. It just depends on where you are, how they locally produce electricity, and demand/infrastructure.

  15. Re:CPU power consumption on Harvesting & Reusing Idle Computer Cycles · · Score: 1

    In the case of United Devices, a redundancy level of 5 is not out of the question. They are dealing with totally anonymous computers, and need to verify that their computations 'add up'. However, in the case where you have more direct access to the machines (and therefore better control and trust), as in the case of a University rolling this out (University of Texas in this case), they can probably skimp on the redundancy.

  16. Re:CPU power consumption on Harvesting & Reusing Idle Computer Cycles · · Score: 1

    In New York City power costs 19 cents per kilowatt-hour. :(

    True, but I took numbers for the location in question, namely Texas. But the argument is nearly independant of the cost of electricity. As long as people who don't need super powerful machines continue to have them, and as long as computers consume much (over 50%) of their power regardless of CPU state (as they still do today), it makes sense to use the spare cycles. At least in some situations.

  17. Re:CPU power consumption on Harvesting & Reusing Idle Computer Cycles · · Score: 4, Insightful

    But it isn't that expensive. Let's call it 100W extra. 24 hours in a day gives us 2.4 kWh per day. For a year, call it 876 kWh. Approximate cost of electricity (in Texas) is about 10 cents per kilowatt-hour. That's $87.50 per year. Let's assume that you can extract half of the computer's horse-power for your cluster (the rest is lost in overhead of the cluster software etc, and of course, whatever the actual user of the PC does, which is often just word processing, email, and surfing the web). For an extra ~$175 per year you get the equivelant of another computer.

    If you wanted to get that computing power in a stand alone system, you'd not only have to purchase the PC (up front capital), but you'd have to pay more for electricity. From the reference link, only about 30% of a computer's power is used by the CPU, the rest is doing nothin'. The computers referenced, at full bore use 185W (best case). That's $162 per year at my 10 cent per kilowatt hour quote. Cheaper, sure, but by the cost of a computer? Not even close.

    Of course, there are other (hidden) costs involved in both methods, of which I'm not including in my (overly?) simplified model. And I'll just brush under the rug the fact that this kinda assumes that the average secretary has a top of the line system to surf the web with.

  18. Re:Duration - Why Not Longer? on BLAST High Altitude Telescope Launched · · Score: 1

    And in case anyone is still following this article and/or thread:

    BLAST has now landed. It was cut down a little short of the plan, as it veered a little further north than we had hoped (and than the wind models and soundings predicted), so it was brought down on Victoria Island, NWT. There are currently people out surveying the gondola at it's landing site, and it should be recovered in the next few days. No real word on damage other than from a thousand feet up (in a plane) it looks not bad.

  19. Re:It would have to be in inordinately large meteo on BLAST High Altitude Telescope Launched · · Score: 1

    If it is a multi-cell balloon, it'd probably equalize at a lower altitude. Not so good for BLASTing, but considerably better than taking all of the nice electronics for a dip in the briny at circa 700km/h about 30 seconds later.

    It is not a multi-cell balloon. But if the meteor put a hole the size of a basket ball through the balloon, it would take days (probably many days) for it to leak enough to hit the ground. There are two valves on the top of the balloon that are used to release some of the helium if we want to go a little lower (which are about as big as a basketball each), and it takes on the order of several hours to drop even a kilometer (we're at 38 km).

    If the metoer managed to rip a hole large enough to make it matter, BLAST would come down on a parachute. The system is meant to be as failsafe as possible, so the gondola (BLAST) hangs from a set of cables called the 'flight ladder' (which has rungs for stability, so it looks like a ladder). This flight ladder is attached to the parachute directly. The parachute is outstreched; the ladder is attached to the bottom, and at the top of the parachute is the (bottom) of the balloon. So if the balloon stops working, the rest will fall, and when there is enough atmosphere, the parachute will snap open.

    But if we're on this ludicrously huge meteor idea, sure, the meteor could also take out the parachute, and then we're screwed. But that's a little on the unlikely side of things.

  20. Re:Duration - Why Not Longer? on BLAST High Altitude Telescope Launched · · Score: 5, Informative

    * Didn't see an answer about which lifting gas - H2 or He?

    I think that Prof. Barth's text got cut off in a weird way. He's probably tired. We all are. The balloon is filled with helium.

    * Wouldn't launching from the North Pole station in summer (now, really) mean no daily temperature cycles or sunlight-heating differentials?

    Which North Pole station are you talking about? The secret one that no one knows about? Seriously, the problem would be transportation. How would you get the (heavy) equipment out there? Where would we land when it's time to terminate the flight? We'd like to be able to recover the entire experiment, and there is basically no plane that could, in once piece, carry a 2700kg gondola from the polar ice cap back to civilization.

    There are usually 2 balloon flights a year from McMurdo. People have talked about launches from South Pole (where there is a station), but the cost of getting everything out there is way way way to expensive, when McMurdo is almost as good (or better).

    * Does anyone from Russia's version of the National Science Foundation or any of the Russian science bureaus read Slashdot?

    Good question. Since it didn't make the front page, only the Science page, probably not. ;-)

    * Was there something specific that caused Russia to say no to overflight rights?

    Nothing specific, they currently prohibit everyone but the French. It's being worked on, but it's too late for us. Next season (next year) other experiments will probably be allowed to fly all the way around.

    * Politics aside, what was the maximum probable mission time - just another day or two or (if going over Russia was possible) doubling to 14 or more days?

    For an LDB balloon the nominal time is 14 days, and there have been flights as long as about 30 days. Those all flew from McMurdo (Antartica), where there is no issue with flying over other countries. (14 days happens to be about the time is usually takes to circumnavigate the pole at these altitudes).

    For BLAST, we're limited by the cryogens in the cryostat that houses our detectors. As configured, we get about 11 days hold time. That would double our data time time around (looks like we'll get about 5 days at float). With a few modifications, we should be able to get the hold time to 14-15 days.

    * Has anyone assigned probabilities to each of the various failure modes?

    Historical data indicates that a balloon operates to achieve scientific minimums 95% of the time.
    prof_barth tells me that annecdotally, about 1/5 experiments get torched on landing.

    * If gondola weight determines spare gas capacity determines flying time, isn't there a way to just create an elastic balloon material that doesn't need a relief valve?

    Theoretically, yes. They've tried, and NASA calls it ULDB (we're LDB, that's for long duration balloon, ULDB is ultra-long duration balloon). They've only just started to test them in the last few years, and so far they have all had some kind of failure (often a 'catastophic leak'). If they get one up that doesn't leak, they expect it'll last for 90 days or so. prof_barth says apparently, back in the early 90's, some small super-pressure balloons (w/ very small payloads) managed to go over 100 days.

    And our balloon doesn't have a relief valve per se, it just has vents to the bottom that are open always.

    * Are the bureacrats Russian or American or someone else? (Somehow I'm confident it's not the Canadians...)

    Good question. both

    * If politics determines mission time regardless of the technical stuff, WHO IS WORKING ON THE POLITICS? (I know, international relations can be much more complicated than the science, but its frustrating to hear from my side, too. I like to read about the cool stuff you're doing). Who do we contact to help push this along for the next mission?

    I don't know. But the

  21. Re:We love you Matt! on BLAST High Altitude Telescope Launched · · Score: 1

    Matt, I didn't write this. Really

    I believe you. But I want to know who did write it.

  22. Re:Load testing on New Global Directory of OpenPGP Keys · · Score: 1

    Who needs to load-test a server when you have slashdot to do it for you?

    Looks like they didn't pass the test.

  23. Re:It should be noted on 230mph Electric Car · · Score: 3, Informative

    I think the point the parent poster was making was that given two 'similarly' sized motors, electrics' have more torque.

    Look at the specs for the Prius:

    Gas Engine:
    76 hp @ 5000 rpm
    82 ft-lb @ 4200 rpm

    Electric Motor:
    67 hp @ 1200-1540 rpm
    295 ft-lb @ 0-1200 rpm

    Both generate comperable max horsepower (albeit at different speeds), but the electric motor has "torque coming out the ass", and does so even at 0 rpm.

  24. Re:Company-owned? on The Traveling Salesman Problem Meets Starbucks · · Score: 1

    Almost every location is company owned, but there are some franchises, usually in grocery stores and the like.

  25. Re:free nookie on Best Results From Bartering Computer Services? · · Score: 3, Funny

    It's not /free/ if you had to fix her computer for it.