And considering the solid rocket boosters were designed to splash down in the ocean to be recovered and refurbished, I'd say the big body of water is kind of important. It wouldn't go over quite as well to drop them onto a rocky desert plain as into a relatively homogenous body of water.
Err...no one has ever tried any long term experiments on bone loss in 0.38 gravity. It's entirely possible that 0.38 is enough to significantly reduce bone loss. As far as the near term goes, though, I believe some cosmonauts spent over a year straight on Mir. They weren't in great shape when they landed, but they survived.
Rotating space station are theoretically fine. There really is no difference as far as anyone can tell (including Einstein) between a gravitational field and an accelleration. Two minor issues that come to mind are angular momentum, which make it difficult to re-orient a spinning space ship, and Coriolis effect, which may cause nausea when you stand up in a relatively small rotating station. It's kind of like leaning outward on a playground merry-go-round, because changing your radius changes your angular velocity, which messes with your sense of balance.
The real issues are engineering and economic related. We've never been willing to commit to building a station big enough to be worth spinning. Plus, docking would be rather complicated. You could just stop the whole thing, which would burn up a lot of fuel, or you can dock at the very center and have your docking collar spin relative to the station (being still overall). However, I suppose another option, if you have a symmetrical, relatively narrow capsule like Orion, is just let the thing spin and ignore the fact that being inside it is disorienting and everything drifts to the outside. The bigger the station, the less of an issue this is because you don't need to rotate as fast (a = omega^2 * r).
In some ways it is better than the shuttle. For one, the design concept (cargo and especially re-entry shield as far away as possible from the explosive stuff and things that fall off) is inherently safer. It is more versatile in that it's mass and re-entry concept does not limit it to low earth orbit. It is thermally a better overall re-entry design. Even the landing is simpler, although it may not seem so at first review (the shuttle has only 2 or 3 landing options and it comes in really fast).
And there are ways that it's inferior. It can't return a large cargo to earth. It can't support major missions on it's own (like Columbia's last mission, where it carried a pressurized science module with over 100 experiments). It can't serve as nearly as effective work platform (think Hubble repair), lacking an airlock and that cool robotic arm. It will only look pretty darn awesome instead of freaking, amazingly awesome when taking off and landing. Etc.
The point that I really want to make with this post is that we are still number 1, although I wish we had needed to work twice as hard to maintain the lead we have over anybody else. Instead Russia, the historic embarrasser of riches, is hanging onto the success of their Soyuz design and doing almost nothing else. Off the top of my head I can't think of a mission not related to the ISS in years, aside from commercial launches. China is talking big, but at this point has launched 3 people on two manned missions and has an unmanned lunar mission in the works. Europe as a whole is looking good, with several major ISS modules to their credit, the Mars and Venus Express probes plus a few smaller missions like SMART-1, and a healthy commercial market, but no real ambitions for growth. Japan has stayed on the down low, catching headlines for the ill-fated but ambitious missions to an asteroid and Mars, but backing away from their original intent to contribute a laboratory module to the ISS. Only the EU and Russia have together proposed a new manned spacecraft, the Klipper, but have not yet committed any real money to it.
In the meantime, the US has continued to carry the bulk of the ISS (although as much due to our own desire to as to any other partner's avoidance of it). The shuttle has successfully returned to flight. Its replacement is well underway. Unless I'm forgetting something, with Hubble, Chandra, SOHO, and Spitzer we're the only nation managing major space-based observatories. We have probes on their way to Mercury (Messenger) and Pluto (New Horizons), a fantastic probe returning tons of data on Saturn (Cassini), and three orbiters around Mars. Then there's those indominatable rovers, which have been operating for over 10 times as long as their design goal and are soon to be joined by the Phoenix Polar Lander, followed by the impressive Mars Surface Laboratory in 2009. Don't forget Deep Impact or Stardust either, the former of which looked inside one comet, while the latter collected samples from another. As far as the moon goes, the Lunar Reconnaisance Orbiter will launch in 2008 with follow-ons to be designed based on research over the next five years.
And the private side of things looks good, too. The Boeing and Lockheed's Delta and Atlas lines are maintaining a reasonable market share. Investors are excited about Virgin Galactic and Scaled Composites. Orbital Sciences in holding up the small end of orbital things, with SpaceX coming up fast behind. Speaking of SpaceX, they're looking quite sharp with the Dragon capsule and Falcon IX well under development for the COTS program (and Orbital Sciences is subcontracting for the other COTS winner).
I think the progress is frustratingly small, but it's there, and it's certainly not backwards.
A very good comment. Considering a manned Mars mission in light of what it took to get to the moon the first time, what it takes to get an unmanned mission one-way to Mars, and how many pounds of groceries I buy each week to feed just myself (a Mars mission would be at least 3 people for anywhere from 6 months to 2 years), I'm skeptical that even the Mars Direct is feasible, and there's quite a few engineers familiar with spacecraft design pushing the Mars Direct architecture.
In a world where you can run down to the dealer and buy a car with probably 15,000 parts for $25,000 that works and conveys a sense of being trouble-free, it's hard for a lot of people to understand why it takes 8 years to design a new spacecraft that on the outside looks just like the old one and doesn't even have a big screen TV, or why it should cost $100 billion to return to the moon.
In the 60's we spent over $100 billion (2006 eqivalent) in about 10 years to land 2 people using a bare-bones single-purpose system that flew 7 missions (6 landings). Now we're looking at spending $100 billion to double the number of feet on the lunar surface, and double or triple the mass landed, plus have a new low earth orbit crew vehicle, new heavy lift vehicle, and a sustainable infrastructure.
Of course the really big difference is that in the 1960's, Congress basically said "how much will it cost to get this done by the end of the decade?" wrote out a check, and directed most of NASA's resources to Apollo. Today, they've said, "Do this, but you have this much money per year and you can't forget to keep working on this (ISS), that (space science), and that other thing (aeronautical science), too. How long will it take?"
So, any ideas as to if any particular location on Earth will have a better show?
From the article (which also has links to tips for backyard astronomers wanting to witness it):
The time to watch: Saturday, September 2nd at 10:41 p.m. PDT (Sept. 3rd, 0541 UT)...The nominal impact time favors observers in western parts of North America and across the Pacific Ocean.
10:41 PM on the west coast or 1:41 AM on the east coast. It will probably have set or be setting at that time on the east coast, and the twilight will probably still be too bright in Hawaii. There's also a nice graphic showing the location of impact with a quarter moon. The impact will be in the shadowed half, making it easier to spot, but they're unsure exactly what brightness to expect. It could be as bright as magnitude 7 (theoretically visible with binoculars, IIRC) or as dim as magnitude 15, in which case it's doubtful anyone will see it. There is also a small chance that their estimates are a little off, in which case it may hit one orbit early or miss and hit one orbit late, so the time is really +/- 5 hours.
So what is the "responsiveness image" presented by this article, considering it's an anonymous submission linking to a Wordpress blog that appears to have been created soley for the purpose of presenting a 2nd-hand discussion of a paper published 3 years ago? The part that really confuses me is the lack of ads.
Tyler, J. R. & Tang, J. C. (2003). When Can I Expect an Email Response? A Study of Rhythms in Email Usage. Proceedings from ECSCW '03: European Conference on Computer-Supported Cooperative Work, 239- 258.
For no reason other than because I'm evil, I present to everyone the following back-of-the-napkin/sources-from-wikipedia analysis:
There was an article a while back about game console power consumption, but rather than dig that up, I'll assume a PS3 will average 200 Watts while cranking away on proteins. It's a good, round number. And I'll assume that I'd spend an hour per day actually playing games. Electricity in my area costs about $0.08/kW-hr.
1679 kW-hr/year * $0.08/kW-hr = $134.32/year for electricity to fold imaginary proteins. Ouch.
And for those worried about C02, 1679 kW-hr is 6,044,400 kJ, which is the energy equivalent to 46 gallons of gasoline (efficiency of conversion not accounted for). Alternately, assuming your electricity comes from a natural gas (CH4 ~ 891 kJ/mol) plant operating at 40% efficiency, one year of folding on your PS3 would release 746 pounds of CO2 (plus 1220 pounds of water vapor).
Gee, aren't numbers fun? In the fight to cure cancer, you actually end up breaking the bank and destroying the planet. That sucks.
I probably really shouldn't have posted that. I'm going to give all the idealistic, penny-pinching, obsessive-compulsive, environmentalist slashdot readers a complex.
Funny, we already discussed the name a month ago. Actually, the funny part is that for once, it wasn't the Slashdot editors that made it a dupe, it was NASA...sort of.
Apparently some clever folk at collectspace.com with too much spare time started digging around and came up with some internal correspondence or something to that effect stating that the project would be called Orion. Then they kept on digging and found that NASA had registered the name as a trademark when used in aerospace. Remarkably, they even found project logos for Orion, Constellation, and Ares. I saw the story on several space news sites, so I was a little taken aback when CNN was reporting that the name had just been released today.
Also, you're confusing two extremely similar names. Aries is one of the famous constellations of the zodiac, and was also a derivative of the Minuteman missile. Ares is the name of the new rocket series and is the god of war in Greek mythology, their counterpart to the Roman Mars. I think it's a somewhat unfitting name since the vehicle is to be used for low Earth orbit and travel to the moon...not to Mars.
Blog First, Then Scientific Journals.
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Dark Matter Exists
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· Score: 3, Insightful
Funny, I always figured the announcement of experimental confirmation of dark matter would first be published in a scientific journal or announced at a news conference...not on a blog shared by Mark, Claire, and Sean, whoever they may be.
* Note that I tried to go back and confirm the names and finish reading the story so I would have something intelligent to say, but apparently the user's CPU allottment only accounts for 20% of the server's total, suggesting that there may be another form of CPU cycles that don't interact with visitor's to the linked site. I think we should call these "dark CPU cycles."
Another good paragraph, more Catch 22
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iPods at War
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· Score: 4, Insightful
Another thing about Catch 22 is that it showed how the first contention of the article, that soldiers used to go to battle with nothing more than a rifle and a backpack isn't true. Remember Orr, Yossarian's tent-mate? He was always adding stuff to the tent. Basically everytime he came into a scene, he was either being shot down or trying to get the gas stove working better. Or consider the show MASH. Hawkeye's tent was full of "luxury" items. Ok these are fictional accounts, but based on non-fiction accounts I've read, I'd be willing to bet they were pretty close the real case in terms of personal possessions...at least for units that stayed in one place for any significant amount of time.
Here's another good paragraph
Ana Marie Cox argued that soldiers' expectations of war are now so shaped by movies and video games that they are unable to experience a conflict in any other way. They want to see battle as pure action, devoid of context, full of simple goals and explosions, and so when they put together music videos of their time in Iraq (and most home videos do feature music), they tend to unconsciously echo the movies and games they've seen and played.
I'm more inclined to think it goes the other way: movies and video games are unable to depict conflict any other way than by focusing on the action, only filling in the context sufficiently to give the viewer/gamer a plausible plot. Except for fans of the movie Jarhead, nobody is very much fascinated by the mundane elements of war: cleaning your rifle, trying to stay awake through guard duty, cleaning your rifle, doing PT, cleaning your rifle, cleaning the latrines, cleaning your rifle. Audiences expect 5 minutes of that, then a lot of shooting and heroism.
Consider amatuer movies at home. For example, the obligatory end-of-the-season high school football team music video recap. It's all clips of tackles, touchdowns, passes, field goals, pranks during scrimmage, etc. Nobody's interested in the time spent running around the track, doing calistenics, sitting on the bench, and especially not sitting in class trying to maintain acedemic elegibility.
Furthermore, we really are talking about amatuer's here, putting together simple recaps. They're not master storytellers. They don't have the time or luxury of putting together complex narratives, and since they're only sharing this with friends and family, they don't need complex expositions making it clear to the viewer that this is so-and-so's involvement in Operation Enduring Freedom.
Yeah, let the MPAA and RIAA go after the piracy of media by soldiers afield.
Actually, let them go after the parties offering the goods for sale. As I understand, the lawyers interest is not as much in the receivers as the providers. Please, go confront Abdul about his copying CD's to sell to the GI's. A flak jacket might be a good a better idea than a briefcase, though.
It's worth mentioning, however, that by the time the COTS participants are ready to demo, NASA will be ready to retire the shuttle, and still be four years short of being ready with the CEV, so the shuttle cost is somewhat irrelevant, especially in view of it's different capabilities. Their comparable options would be the Boeing Delta IV and Lockheed Atlas V EELV's, which aren't nor are they planned to be man-rated and cost over $100 million per vehicle, or the Russian Soyuz and Progress capsules. I've read that the Soyuz cost about $70 million per launch, in equivalent US dollars. The Progress are a little cheaper.
Your SpaceX costs are correct, or nearly so. Right now the Falcon 9 is slated to cost between $27 and $35 million per launch. However, Musk has stated that the Falcon 9 is to be reusable, so I suspect that figure assumes that plan works out. Also, that number does not include the cost of the Dragon capsule, which I suspect will run anywhere from $5 and $20 million more.
Figures on the cost per shuttle flight range from $55 million, which is how much it costs to do between flight maintenance, preparation, training, and actually operate the mission, up to about $1.1 billion, if you include every single penny spent ever spent on the shuttle program, including R&D (and probably related projects that were killed like the fly-back boosters) and assume no more flights will be made.
Everyone go take a look at the illustrations in the article if you haven't. That Dragon looks really cramped when you squeeze 7 people into it. Worse than flying coach on Southwest. I know the space shuttle typically orbits for about 2 days before docking with the ISS. I hope that's just a fuel saving measure, because I couldn't imagine spending more than 6 hours in that position.
The earth is not genuinely round. Most everyone who paid attention in their freshmen science class in high school knows that it's bulges about the middle due to centrifugal momentum. Same for Jupiter. If you really want to get specific, there's tons of mountains and cliffs on earth that further screw up the roundness and even the convexness of the surface, but that's just getting silly. Bodies like Demos and Phobos are less round, but gravity must have some effect on their shape. Also, material matters. An icy body like Pluto is thought to be would form into a round shape at a lower mass than a rocky one.
The new definition definitely has a good element of precision to it, but consider two bodies of the same mass and composition where one is "rounder" than the other, perhaps due to a major impact event or something (I believe one of Saturn's moons is like this). There's no real difference that distinguishes one as a planet and the other as an asteroid, at least not like there is a difference between carbon and nitrogen. It's just going to be a fact of astronomy things are not as discrete as in some other fields. I guess they felt they had to draw a solid line somewhere for the definition, but that line was still arbitrarily drawn and it's not quite solid.
Anyway, I'm sure kids for another generation or two will still memorize the 9 historical planets. Then teachers may slowly start making them memorize the 8 major planets (or perhaps Ceres will take Pluto's place in the list) and remember that there are dozens of smaller planets.
The definition also, as near as I can tell, still leaves the upper end in question. At what point is a body a star rather than a planet? Supposedly some of the extrasolar planets found are large enough to initiate fusion of deuterium at their cores.
Right...and I bet because of the points you made, land values aren't very high. 300 acres amounts to chump change. I guess they figured as long as they aren't using the land, they might as well look good while getting it off their hands. The only thing this place has going for it is a similar latitude to Baikanor, where the Russians launch their rockets from. Along the same vein, I've got a microwave I don't use anymore. Are there any universities that might want it for electromagnetics research?
As you hang around Slashdot longer, you will eventually learn how to distinguish between genuine news and overhyped press releases from clever venture capitalists picking up investments from gullible people. Not only is there nothing out there to support the facility, I don't think there's even a sustainable market for launches from there. No company has yet launched a privately developed rocket into orbit, so there's also not much in the way of products. The closest, SpaceX, already has invested a significant amount in launch facilities at White Sands and the Kwajalein Atoll, and no one on their current list of customers is interested in a high inclination orbit anyway. Boeing and Lockheed are pretty much tied down by their infrastructure and regulation to their established facilities.
Biosphere was intended to create a fully self-contained, (almost...heat was a problem) self-cycling bio-system...a miniature earth. It's primary concern was simulating a natural environment. The Mars Society's project is more concerned with people's ability to function in close quarters, in uncomfortable conditions for extended periods of time.
The Mars Society will pay travel expenses to the Desert and the Arctic Stations. There will be no salary. (from the article)
Hmmm, if they can't even pay their talented, dedicated researchers, I'm wondering how much they have to invest in a reliable shelter and gear for spending 4 months up in the cold.
On the other hand, early DS9 was very similar to TNG: episodic vignettes that can be neatly wrapped up when the hour is through, and everything is the same at the end as it was in the beginning.
If you think about it, that's really the format of the original, too. I would argue it even contributed to its success. Like The Twilight Zone, Star Trek was really a vehicle to explore individual SciFi stories, but Star Trek deviated slightly and gave the stories to audience with a consistant cast of characters (with the exception of that security officer who died in every single landing party).
In contrast shows like
Battlestar Galactica
had a continuously developing storyline making them more like a book instead of a compilation of short stories. It makes for a more engaging viewing experience, but takes more interest to get into it, since if you miss an episode, you miss out on elements of story.
Re:This requires not storing in insulators?
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Halving Half Lives
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· Score: 1
Insulators block whatever the heck you want them, too. Electrical insulators block electricity, thermal insulators block heat. I guess you could call something that blocks radiation a radio-insulator.
Anything can be used as shielding against gamma rays, but higher density materials are more effective. Concrete is popular because it's cheap and every 2.5 inches absorbs half of the gamma ray flux. 2 feet of concrete will reduce gamma ray flux to 0.1% of the incoming level.
Also, beta particles release gamma rays when they hit something, and alpha particles produce gamma rays when they decay. However, in both cases if you're already dealing with gamma rays, you've by probably by extension dealth with the heavier particles.
When someone says fiber reinforced polymer (FRP), the mean a composite like fiberglass or carbon fiber. Reporters generally don't understand this and like the sound of FRP better anyway. The material is nothing new.
They're not talking about building an entire bridge out of it. The article doesn't say what, although I could probably find it with a thorough google search. Most likely the road deck (the city of Portland has one drawbridge that was recently retrofitted with composite decks for weight savings, with two more planned/in progress) and possibly some of the girders and cables. Most of the mass of the bridge will undoubtably still be concrete and steel.
Composite materials (including FRP's) typically begin to break down at a few hundred degrees, although that is highly dependent upon the type of matrix material (usually an epoxy) that is used. The matrix will generally fail well before the fiber does. Also a minor correction, but the WTC collapse was due to a phenomena known as creep, where metals at elevated temperatures slowly deform despite being well below their yield stress. In this case, they deformed to the point where some members buckled, and collapse proceded rapidly from that point.
Cost of building processes is taken into account when planning for a major project. This includes developing repeatable processes that can be conducted in a construction environments and training the workers. In this case, many of the members will actually be prefabricated and installed whole using more traditional methods of assembly. Most likely in this case, one of the bidding companies has some particular expertise working with composites.
I believe most environmental impact filings on civil projects also require end-of-life plans. Fiberglass is quite capable of being disposed of safely.
FRP - Fiber Reinforced Polymer really means composites. In this case, probably some type of fiberglass or carbon fiber composites. To merely call it plastic is a little misleading, especially since not all polymers used in composites are plastics. Technically, even concrete is a composite, but obviously of a different nature than we're discussing here.
Also, this is only relatively new. This is one of those repeat stories that comes up from time to time when some editor thinks he's stumbled upon something incredible. I think I saw an article about "glass" bridges in Popular Mechanics 7-8 years ago (meaning fiberglass, actually, but that didn't stop the PM artists from drawing pictures of transparent bridges). For several years, a largely composite cable stayed bridge has been in planning stages as a replacement for an old span on Interstate 5 in California.
More currently, I interned with a company that assisted with a fiberglass reinforcement of a small concrete and steel bridge near Mt. Hood in Oregon. The city of Portland and Martin Marietta Materials recently replaced the slippery-when-wet steel deck on the Broadway Bridge in downtown Portland with a composite deck that performs comparably to concrete for traction and longevity, but is light enough not to interfere with raising the drawspan. Two more bridges in Portland are slated for similar modifications.
One of the articles linked in the submission states the plan is to have Japanese astronauts landing on the moon by 2020, begin construction by 2025, and be permanently manned by 2030. Given that NASA's goal is to return to the moon by 2018, and that Japan's space agency is much smaller and younger than ours with no direct experience in manned exploration and no heavy-lift infrastructure, this really sounds extremely ambitious.
Yes, the bits and pieces of the technology exist, but the systems do not. We've proven in the past we can build the systems, but we still have to knuckle down and spend the time and money doing so again.
As I was watching it last night, I could visualize thousands of people on their laptops first flocking to the Colbert Report entry to see if he had really changed it, along with a few immediately updating it to read that "Colbert often refers to Oregon as Idaho's Portugal." About two minutes later, I figured they would all be heading over to the elephant entry to modify that, and then I estimated that within 5 minutes, a handful of moderators watching the show would have no doubt reverted and temporarily locked down both pages.
As I look at http://en.wikipedia.org/wiki/The_Colbert_Report I see that there were approximately 150 edits yesterday, a significant portion of them reverts, it is semi-protected, and there are probably 20-30 threads discussing yesterday's show in the discussion for the entry. However, Oregon doesn't appear anywhere in the entry if I search the page.
There's probably 300 edits to Elephant, too, and the discussion suggests that long-contributing members joined in on the vandalism.
On a side note, I think this is a perfect example of the wikipedia model working successfully. Not a claim that wikipedia is perfect, but the community successfully limiting such "organized" vandalism on such an open site in commendable.
Actually, you've only accounted for about half of the determination of pain. Also, it's the energy that is the same, not the force.
Force = pressure * area = mass * accelleration. Assuming the main determinant of how much pain you feel is pressure (a rough but reasonable assumption), then just do some real quick algebra and note that:
Pressure = mass * acceleration / area
Obviously, the more distance you can distribute that accelleration over, the lower the acceleration and hence the lower the force.
As an example some of us may have experienced personally when we were little, consider catching a sharply thrown baseball in a glove and compare that to taking a sharply thrown baseball in the chest (lesson: don't get distracted when playing shortstop). The glove alone has several inches of give while absorbing the energy of the ball (assuming you catch it in the web, rather than on your palm), and if you pay attention you'll also notice most people give with their arm as they catch. In comparison, the ball hitting you in the chest slows down in about the distance it deforms your chest (staggering happens to slowly to really count). Actually, given the extra mass, a fastball is probably a good approximation of a pistol round for momentum as well as for the area that body armor distributes the force of a bullet.
I've never shot a.45 pistol, but I have shot 9mm and that little round will move your arm by probably about 6 inches unless you're particularly tense. And if you are really tense, you'll probably find that shooting the gun actually does hurt your hand. I've also shot rifles as big as.50 Browning. If you don't have the butt tightly up against your shoulder, effectively making your body and the gun one rigid mass that will be accellerated simultaneously, you're going to be in pain when the butt hits you.
To sidestep back to the main discussion, a lot of people seem to think of this fluid as magical ("imagine what it could do for car safety," etc). The practical limitation is that it only achieves the extremely high shear rate needed to "lock up" in small areas. If you try to deform a 1 inch square piece of material by 1 inch in 0.01 second, the shear rate is relatively high. If you try to deform a 10 inch square piece by 1 inch, you'll find that the displacement is distributed and the average shear is only about 10% as much as the other case. That's assuming you can deform the two samples in the same manner, which would be pretty tough for any load case other than planar stretching. If you coated a car bumper with this stuff, it would probably just crack at the areas of highest deformation and not react at all at the areas of lowest deformation in an accident. Of course, you could simply fill the entire bumper up with it...
Regarding the efficiency, I fully recognized that when I post the comment you quoted. The main issue, as we both recognized, is the energy density. Most of my post in the original article was addressing that in light of a suggestion that was made about commercial trucks.
More in line with your point, though: Electric motors actually have wonderfully stable efficiency curves over their load and speed ranges compared to ICE engines, but that's not the only factor coming into play. Drag is really important hear. Displacing air takes work which means wasted energy. The amount wasted scales roughly with the square of your velocity. Of course, both electric and ICE vehicles face this problem. The difference is electric motors are relatively efficient regardless of whether you're going fast or slow, so if you go slow, because there's less work accomplished on the ambient air, you waste less energy. With a car, however, the engine efficiency is terrible at low speeds, but increases up to a certain point. Therefore, your car's overall efficiency actually peaks at an intermediate speed between the 0 and redline. In most passenger cars this is around 55-65mph. In an electric car, it would theoretically be much lower.
This doesn't mean that electric cars suck, it just means they're far better suited for city driving than highway driving. Yes, better suited than gasoline cars. The EPA (see fuel economy.gov) fuel cost estimates place electric vehicles at half or less than equivalent gas vehicles. You really just have to get around the range issue.
Also, electric vehicle efficiency also has to include generator and transmission efficiencies. I've never seen a good thorough analysis, but my estimates suggest that electric cars overall do come out slightly ahead in overall efficiency.
My comment about McD's was taken out of context from the original discussion. A branch had started discussing the applicability for long trips, and another poster suggested that common pitstops like fast food joints could offer recharging stations as a bonus to attract more customers. His idea was to go 250 miles at 70 mph would take about 3.5 hours, which would put the driver at about snack time, so why not plug in and charge for 15 minutes while you eat? As I pointed out, that unfortunately doesn't work. He also had a suggestion about commercial freight, leading to the rest of the long comment quoted in today's backslash.
I still maintain that the electric car is poorly suited for long trips. It would theoretically be possible to replace gas stations with battery-swap stations that will stick a freshly charged pack in for a fee, but even that is a little tough. The Tesla's pack weighs about 1000 pounds. You may think, "but it's a roadster, it needs a lot of juice." That's partially true, but really any car with a similar CD, weight, and rolling friction is going to take about the same amount of total energy. The big difference is how fast you drive and if the motor is sized to give peak efficiency at your driving speed.
Ok, so it's 1000 pounds of batteries give or take. Your best bet is probably to break it down into modules that are standard between all vehicles so the stations don't have to stock multiple types. Perhaps each one ways 200 pounds. A commuter car might need 4 of them. A family wagon 5. A delivery van 8-10. Then you drive your car up onto a service ramp, they wheel a jack underneath, drop out the spent units, wheel some fresh ones into place, and jack them up. In addition to standard battery packs, you would also need the manufacturers to make them accessible in a consistent method. Given weight and space concerns, that may be difficult to achieve.
I'm wandering into design questions here, so I'm just going to say the last thing I came to say and leave it at that. Electic cars could work fantastic for commuter purposes, but I think for the time being gas is still our best bet for most other applications. Obviously it's expensive and somewhat inefficient to own a ton of different cars, but concepts like rentals or flex cars could be perfect for filling those rarer needs.
When connected to a special 220-volt, 70-amp outlet, recharging takes about three and a half hours.
15 minutes on the charger might get you another 15-20 miles. And 220 volts at 70 amps is a pretty hefty 15 kilowatts, so to have a dozen cars sitting at the local McDonalds charging is going to be draining about 180 kW from their coinpurse. That is a serious amount of juice. Also, I'm skeptical that you'll be getting 250 miles at 70 mph. If I remember right, electric motor efficiency and power typically increase with load, but fall off with speed, which makes them awesome for say, a 0-60 run in 3 seconds, but marginal at best for high speed cruising. That 250 mile range estimate is probably at significantly lower speeds.
Big rigs generally run around 5 mpg, but it varies quite a bit around that number depending on the truck, the load, and the speed. Few truckers drive at the most efficient speed because it increases the labor costs significantly.
If you're suggesting running commercial trucks on electricity, forget it for the foreseeable future. It's definitely been considered. Not only is there the conflicting speed issues I mentioned above, but you run up against the energy density limitations of batteries fast. Assuming the numbers from the article are correct (I doubt it...something isn't quite adding up according to my gut) and unrealistically taking the charge/discharge at 100% efficiency, it's storing up 194 MJ. Gasoline holds about 120 MJ/gallon, so the 1000 pounds of batteries (according to the Tesla website) are equivalent to about 1.5 gallons of gas (6.3 pounds/gal). Divide that by an efficiency of around 30% and you've got a 32:1 energy density ratio in favor of gasoline. For a truck to haul the equivalent of 150 gallons of fuel (actually diesel, not gas, but close enough), it would need about 30,000 pounds of batteries. But then you have to go farther and take into account that 2/3's of its cargo capacity has been replaced by fuel, so you need to make 3 times the number of trips. And you've got a lot of trucks either sitting idle recharging or having their 30,000 pounds of batteries swapped out every few hundred miles.
Obviously these are really rough numbers, but other engineers have already looked at the idea in more detail and rejected it.
I'm not trash-talking the Tesla. It looks like a lot of fun, but like all sports cars, it's a toy and not a good comparison for commercial trucking. Most of a car's weight is itself, be it gas or electric. Most of a truck's weight is it's cargo.
For the record, I think electric can work extremely well for short range commuting (5-10 miles on city streets), but if you travel far, you'll realistically be looking at gas.
Slashdot Mirror
And considering the solid rocket boosters were designed to splash down in the ocean to be recovered and refurbished, I'd say the big body of water is kind of important. It wouldn't go over quite as well to drop them onto a rocky desert plain as into a relatively homogenous body of water.
Err...no one has ever tried any long term experiments on bone loss in 0.38 gravity. It's entirely possible that 0.38 is enough to significantly reduce bone loss. As far as the near term goes, though, I believe some cosmonauts spent over a year straight on Mir. They weren't in great shape when they landed, but they survived.
Rotating space station are theoretically fine. There really is no difference as far as anyone can tell (including Einstein) between a gravitational field and an accelleration. Two minor issues that come to mind are angular momentum, which make it difficult to re-orient a spinning space ship, and Coriolis effect, which may cause nausea when you stand up in a relatively small rotating station. It's kind of like leaning outward on a playground merry-go-round, because changing your radius changes your angular velocity, which messes with your sense of balance.
The real issues are engineering and economic related. We've never been willing to commit to building a station big enough to be worth spinning. Plus, docking would be rather complicated. You could just stop the whole thing, which would burn up a lot of fuel, or you can dock at the very center and have your docking collar spin relative to the station (being still overall). However, I suppose another option, if you have a symmetrical, relatively narrow capsule like Orion, is just let the thing spin and ignore the fact that being inside it is disorienting and everything drifts to the outside. The bigger the station, the less of an issue this is because you don't need to rotate as fast (a = omega^2 * r).
In some ways it is better than the shuttle. For one, the design concept (cargo and especially re-entry shield as far away as possible from the explosive stuff and things that fall off) is inherently safer. It is more versatile in that it's mass and re-entry concept does not limit it to low earth orbit. It is thermally a better overall re-entry design. Even the landing is simpler, although it may not seem so at first review (the shuttle has only 2 or 3 landing options and it comes in really fast).
And there are ways that it's inferior. It can't return a large cargo to earth. It can't support major missions on it's own (like Columbia's last mission, where it carried a pressurized science module with over 100 experiments). It can't serve as nearly as effective work platform (think Hubble repair), lacking an airlock and that cool robotic arm. It will only look pretty darn awesome instead of freaking, amazingly awesome when taking off and landing. Etc.
The point that I really want to make with this post is that we are still number 1, although I wish we had needed to work twice as hard to maintain the lead we have over anybody else. Instead Russia, the historic embarrasser of riches, is hanging onto the success of their Soyuz design and doing almost nothing else. Off the top of my head I can't think of a mission not related to the ISS in years, aside from commercial launches. China is talking big, but at this point has launched 3 people on two manned missions and has an unmanned lunar mission in the works. Europe as a whole is looking good, with several major ISS modules to their credit, the Mars and Venus Express probes plus a few smaller missions like SMART-1, and a healthy commercial market, but no real ambitions for growth. Japan has stayed on the down low, catching headlines for the ill-fated but ambitious missions to an asteroid and Mars, but backing away from their original intent to contribute a laboratory module to the ISS. Only the EU and Russia have together proposed a new manned spacecraft, the Klipper, but have not yet committed any real money to it.
In the meantime, the US has continued to carry the bulk of the ISS (although as much due to our own desire to as to any other partner's avoidance of it). The shuttle has successfully returned to flight. Its replacement is well underway. Unless I'm forgetting something, with Hubble, Chandra, SOHO, and Spitzer we're the only nation managing major space-based observatories. We have probes on their way to Mercury (Messenger) and Pluto (New Horizons), a fantastic probe returning tons of data on Saturn (Cassini), and three orbiters around Mars. Then there's those indominatable rovers, which have been operating for over 10 times as long as their design goal and are soon to be joined by the Phoenix Polar Lander, followed by the impressive Mars Surface Laboratory in 2009. Don't forget Deep Impact or Stardust either, the former of which looked inside one comet, while the latter collected samples from another. As far as the moon goes, the Lunar Reconnaisance Orbiter will launch in 2008 with follow-ons to be designed based on research over the next five years.
And the private side of things looks good, too. The Boeing and Lockheed's Delta and Atlas lines are maintaining a reasonable market share. Investors are excited about Virgin Galactic and Scaled Composites. Orbital Sciences in holding up the small end of orbital things, with SpaceX coming up fast behind. Speaking of SpaceX, they're looking quite sharp with the Dragon capsule and Falcon IX well under development for the COTS program (and Orbital Sciences is subcontracting for the other COTS winner).
I think the progress is frustratingly small, but it's there, and it's certainly not backwards.
A very good comment. Considering a manned Mars mission in light of what it took to get to the moon the first time, what it takes to get an unmanned mission one-way to Mars, and how many pounds of groceries I buy each week to feed just myself (a Mars mission would be at least 3 people for anywhere from 6 months to 2 years), I'm skeptical that even the Mars Direct is feasible, and there's quite a few engineers familiar with spacecraft design pushing the Mars Direct architecture.
In a world where you can run down to the dealer and buy a car with probably 15,000 parts for $25,000 that works and conveys a sense of being trouble-free, it's hard for a lot of people to understand why it takes 8 years to design a new spacecraft that on the outside looks just like the old one and doesn't even have a big screen TV, or why it should cost $100 billion to return to the moon.
In the 60's we spent over $100 billion (2006 eqivalent) in about 10 years to land 2 people using a bare-bones single-purpose system that flew 7 missions (6 landings). Now we're looking at spending $100 billion to double the number of feet on the lunar surface, and double or triple the mass landed, plus have a new low earth orbit crew vehicle, new heavy lift vehicle, and a sustainable infrastructure.
Of course the really big difference is that in the 1960's, Congress basically said "how much will it cost to get this done by the end of the decade?" wrote out a check, and directed most of NASA's resources to Apollo. Today, they've said, "Do this, but you have this much money per year and you can't forget to keep working on this (ISS), that (space science), and that other thing (aeronautical science), too. How long will it take?"
From the article (which also has links to tips for backyard astronomers wanting to witness it):
10:41 PM on the west coast or 1:41 AM on the east coast. It will probably have set or be setting at that time on the east coast, and the twilight will probably still be too bright in Hawaii. There's also a nice graphic showing the location of impact with a quarter moon. The impact will be in the shadowed half, making it easier to spot, but they're unsure exactly what brightness to expect. It could be as bright as magnitude 7 (theoretically visible with binoculars, IIRC) or as dim as magnitude 15, in which case it's doubtful anyone will see it. There is also a small chance that their estimates are a little off, in which case it may hit one orbit early or miss and hit one orbit late, so the time is really +/- 5 hours.
So what is the "responsiveness image" presented by this article, considering it's an anonymous submission linking to a Wordpress blog that appears to have been created soley for the purpose of presenting a 2nd-hand discussion of a paper published 3 years ago? The part that really confuses me is the lack of ads.
For no reason other than because I'm evil, I present to everyone the following back-of-the-napkin/sources-from-wikipedia analysis:
There was an article a while back about game console power consumption, but rather than dig that up, I'll assume a PS3 will average 200 Watts while cranking away on proteins. It's a good, round number. And I'll assume that I'd spend an hour per day actually playing games. Electricity in my area costs about $0.08/kW-hr.
0.2 kW * 23 hr/day * 365 day/year = 1679 kW-hours/year
1679 kW-hr/year * $0.08/kW-hr = $134.32/year for electricity to fold imaginary proteins. Ouch.
And for those worried about C02, 1679 kW-hr is 6,044,400 kJ, which is the energy equivalent to 46 gallons of gasoline (efficiency of conversion not accounted for). Alternately, assuming your electricity comes from a natural gas (CH4 ~ 891 kJ/mol) plant operating at 40% efficiency, one year of folding on your PS3 would release 746 pounds of CO2 (plus 1220 pounds of water vapor).
Gee, aren't numbers fun? In the fight to cure cancer, you actually end up breaking the bank and destroying the planet. That sucks.
I probably really shouldn't have posted that. I'm going to give all the idealistic, penny-pinching, obsessive-compulsive, environmentalist slashdot readers a complex.
Funny, we already discussed the name a month ago. Actually, the funny part is that for once, it wasn't the Slashdot editors that made it a dupe, it was NASA...sort of.
Apparently some clever folk at collectspace.com with too much spare time started digging around and came up with some internal correspondence or something to that effect stating that the project would be called Orion. Then they kept on digging and found that NASA had registered the name as a trademark when used in aerospace. Remarkably, they even found project logos for Orion, Constellation, and Ares. I saw the story on several space news sites, so I was a little taken aback when CNN was reporting that the name had just been released today.
Also, you're confusing two extremely similar names. Aries is one of the famous constellations of the zodiac, and was also a derivative of the Minuteman missile. Ares is the name of the new rocket series and is the god of war in Greek mythology, their counterpart to the Roman Mars. I think it's a somewhat unfitting name since the vehicle is to be used for low Earth orbit and travel to the moon...not to Mars.
Funny, I always figured the announcement of experimental confirmation of dark matter would first be published in a scientific journal or announced at a news conference...not on a blog shared by Mark, Claire, and Sean, whoever they may be.
* Note that I tried to go back and confirm the names and finish reading the story so I would have something intelligent to say, but apparently the user's CPU allottment only accounts for 20% of the server's total, suggesting that there may be another form of CPU cycles that don't interact with visitor's to the linked site. I think we should call these "dark CPU cycles."
Another thing about Catch 22 is that it showed how the first contention of the article, that soldiers used to go to battle with nothing more than a rifle and a backpack isn't true. Remember Orr, Yossarian's tent-mate? He was always adding stuff to the tent. Basically everytime he came into a scene, he was either being shot down or trying to get the gas stove working better. Or consider the show MASH. Hawkeye's tent was full of "luxury" items. Ok these are fictional accounts, but based on non-fiction accounts I've read, I'd be willing to bet they were pretty close the real case in terms of personal possessions...at least for units that stayed in one place for any significant amount of time.
Here's another good paragraph
I'm more inclined to think it goes the other way: movies and video games are unable to depict conflict any other way than by focusing on the action, only filling in the context sufficiently to give the viewer/gamer a plausible plot. Except for fans of the movie Jarhead, nobody is very much fascinated by the mundane elements of war: cleaning your rifle, trying to stay awake through guard duty, cleaning your rifle, doing PT, cleaning your rifle, cleaning the latrines, cleaning your rifle. Audiences expect 5 minutes of that, then a lot of shooting and heroism.
Consider amatuer movies at home. For example, the obligatory end-of-the-season high school football team music video recap. It's all clips of tackles, touchdowns, passes, field goals, pranks during scrimmage, etc. Nobody's interested in the time spent running around the track, doing calistenics, sitting on the bench, and especially not sitting in class trying to maintain acedemic elegibility.
Furthermore, we really are talking about amatuer's here, putting together simple recaps. They're not master storytellers. They don't have the time or luxury of putting together complex narratives, and since they're only sharing this with friends and family, they don't need complex expositions making it clear to the viewer that this is so-and-so's involvement in Operation Enduring Freedom.
Actually, let them go after the parties offering the goods for sale. As I understand, the lawyers interest is not as much in the receivers as the providers. Please, go confront Abdul about his copying CD's to sell to the GI's. A flak jacket might be a good a better idea than a briefcase, though.
It's worth mentioning, however, that by the time the COTS participants are ready to demo, NASA will be ready to retire the shuttle, and still be four years short of being ready with the CEV, so the shuttle cost is somewhat irrelevant, especially in view of it's different capabilities. Their comparable options would be the Boeing Delta IV and Lockheed Atlas V EELV's, which aren't nor are they planned to be man-rated and cost over $100 million per vehicle, or the Russian Soyuz and Progress capsules. I've read that the Soyuz cost about $70 million per launch, in equivalent US dollars. The Progress are a little cheaper.
Your SpaceX costs are correct, or nearly so. Right now the Falcon 9 is slated to cost between $27 and $35 million per launch. However, Musk has stated that the Falcon 9 is to be reusable, so I suspect that figure assumes that plan works out. Also, that number does not include the cost of the Dragon capsule, which I suspect will run anywhere from $5 and $20 million more.
Figures on the cost per shuttle flight range from $55 million, which is how much it costs to do between flight maintenance, preparation, training, and actually operate the mission, up to about $1.1 billion, if you include every single penny spent ever spent on the shuttle program, including R&D (and probably related projects that were killed like the fly-back boosters) and assume no more flights will be made.
Everyone go take a look at the illustrations in the article if you haven't. That Dragon looks really cramped when you squeeze 7 people into it. Worse than flying coach on Southwest. I know the space shuttle typically orbits for about 2 days before docking with the ISS. I hope that's just a fuel saving measure, because I couldn't imagine spending more than 6 hours in that position.
The earth is not genuinely round. Most everyone who paid attention in their freshmen science class in high school knows that it's bulges about the middle due to centrifugal momentum. Same for Jupiter. If you really want to get specific, there's tons of mountains and cliffs on earth that further screw up the roundness and even the convexness of the surface, but that's just getting silly. Bodies like Demos and Phobos are less round, but gravity must have some effect on their shape. Also, material matters. An icy body like Pluto is thought to be would form into a round shape at a lower mass than a rocky one.
The new definition definitely has a good element of precision to it, but consider two bodies of the same mass and composition where one is "rounder" than the other, perhaps due to a major impact event or something (I believe one of Saturn's moons is like this). There's no real difference that distinguishes one as a planet and the other as an asteroid, at least not like there is a difference between carbon and nitrogen. It's just going to be a fact of astronomy things are not as discrete as in some other fields. I guess they felt they had to draw a solid line somewhere for the definition, but that line was still arbitrarily drawn and it's not quite solid. Anyway, I'm sure kids for another generation or two will still memorize the 9 historical planets. Then teachers may slowly start making them memorize the 8 major planets (or perhaps Ceres will take Pluto's place in the list) and remember that there are dozens of smaller planets. The definition also, as near as I can tell, still leaves the upper end in question. At what point is a body a star rather than a planet? Supposedly some of the extrasolar planets found are large enough to initiate fusion of deuterium at their cores.
Right...and I bet because of the points you made, land values aren't very high. 300 acres amounts to chump change. I guess they figured as long as they aren't using the land, they might as well look good while getting it off their hands. The only thing this place has going for it is a similar latitude to Baikanor, where the Russians launch their rockets from. Along the same vein, I've got a microwave I don't use anymore. Are there any universities that might want it for electromagnetics research?
As you hang around Slashdot longer, you will eventually learn how to distinguish between genuine news and overhyped press releases from clever venture capitalists picking up investments from gullible people. Not only is there nothing out there to support the facility, I don't think there's even a sustainable market for launches from there. No company has yet launched a privately developed rocket into orbit, so there's also not much in the way of products. The closest, SpaceX, already has invested a significant amount in launch facilities at White Sands and the Kwajalein Atoll, and no one on their current list of customers is interested in a high inclination orbit anyway. Boeing and Lockheed are pretty much tied down by their infrastructure and regulation to their established facilities.
Biosphere was intended to create a fully self-contained, (almost...heat was a problem) self-cycling bio-system...a miniature earth. It's primary concern was simulating a natural environment. The Mars Society's project is more concerned with people's ability to function in close quarters, in uncomfortable conditions for extended periods of time.
Hmmm, if they can't even pay their talented, dedicated researchers, I'm wondering how much they have to invest in a reliable shelter and gear for spending 4 months up in the cold.
Fine, you come up with a cheap design to add on to a rover that will
If you think about it, that's really the format of the original, too. I would argue it even contributed to its success. Like The Twilight Zone, Star Trek was really a vehicle to explore individual SciFi stories, but Star Trek deviated slightly and gave the stories to audience with a consistant cast of characters (with the exception of that security officer who died in every single landing party).
In contrast shows like
Battlestar Galactica
had a continuously developing storyline making them more like a book instead of a compilation of short stories. It makes for a more engaging viewing experience, but takes more interest to get into it, since if you miss an episode, you miss out on elements of story.Insulators block whatever the heck you want them, too. Electrical insulators block electricity, thermal insulators block heat. I guess you could call something that blocks radiation a radio-insulator.
Anything can be used as shielding against gamma rays, but higher density materials are more effective. Concrete is popular because it's cheap and every 2.5 inches absorbs half of the gamma ray flux. 2 feet of concrete will reduce gamma ray flux to 0.1% of the incoming level.
Also, beta particles release gamma rays when they hit something, and alpha particles produce gamma rays when they decay. However, in both cases if you're already dealing with gamma rays, you've by probably by extension dealth with the heavier particles.
When someone says fiber reinforced polymer (FRP), the mean a composite like fiberglass or carbon fiber. Reporters generally don't understand this and like the sound of FRP better anyway. The material is nothing new.
They're not talking about building an entire bridge out of it. The article doesn't say what, although I could probably find it with a thorough google search. Most likely the road deck (the city of Portland has one drawbridge that was recently retrofitted with composite decks for weight savings, with two more planned/in progress) and possibly some of the girders and cables. Most of the mass of the bridge will undoubtably still be concrete and steel.
Composite materials (including FRP's) typically begin to break down at a few hundred degrees, although that is highly dependent upon the type of matrix material (usually an epoxy) that is used. The matrix will generally fail well before the fiber does. Also a minor correction, but the WTC collapse was due to a phenomena known as creep, where metals at elevated temperatures slowly deform despite being well below their yield stress. In this case, they deformed to the point where some members buckled, and collapse proceded rapidly from that point.
Cost of building processes is taken into account when planning for a major project. This includes developing repeatable processes that can be conducted in a construction environments and training the workers. In this case, many of the members will actually be prefabricated and installed whole using more traditional methods of assembly. Most likely in this case, one of the bidding companies has some particular expertise working with composites.
I believe most environmental impact filings on civil projects also require end-of-life plans. Fiberglass is quite capable of being disposed of safely.
FRP - Fiber Reinforced Polymer really means composites. In this case, probably some type of fiberglass or carbon fiber composites. To merely call it plastic is a little misleading, especially since not all polymers used in composites are plastics. Technically, even concrete is a composite, but obviously of a different nature than we're discussing here.
Also, this is only relatively new. This is one of those repeat stories that comes up from time to time when some editor thinks he's stumbled upon something incredible. I think I saw an article about "glass" bridges in Popular Mechanics 7-8 years ago (meaning fiberglass, actually, but that didn't stop the PM artists from drawing pictures of transparent bridges). For several years, a largely composite cable stayed bridge has been in planning stages as a replacement for an old span on Interstate 5 in California.
More currently, I interned with a company that assisted with a fiberglass reinforcement of a small concrete and steel bridge near Mt. Hood in Oregon. The city of Portland and Martin Marietta Materials recently replaced the slippery-when-wet steel deck on the Broadway Bridge in downtown Portland with a composite deck that performs comparably to concrete for traction and longevity, but is light enough not to interfere with raising the drawspan. Two more bridges in Portland are slated for similar modifications.
One of the articles linked in the submission states the plan is to have Japanese astronauts landing on the moon by 2020, begin construction by 2025, and be permanently manned by 2030. Given that NASA's goal is to return to the moon by 2018, and that Japan's space agency is much smaller and younger than ours with no direct experience in manned exploration and no heavy-lift infrastructure, this really sounds extremely ambitious.
Yes, the bits and pieces of the technology exist, but the systems do not. We've proven in the past we can build the systems, but we still have to knuckle down and spend the time and money doing so again.
As I was watching it last night, I could visualize thousands of people on their laptops first flocking to the Colbert Report entry to see if he had really changed it, along with a few immediately updating it to read that "Colbert often refers to Oregon as Idaho's Portugal." About two minutes later, I figured they would all be heading over to the elephant entry to modify that, and then I estimated that within 5 minutes, a handful of moderators watching the show would have no doubt reverted and temporarily locked down both pages.
As I look at http://en.wikipedia.org/wiki/The_Colbert_Report I see that there were approximately 150 edits yesterday, a significant portion of them reverts, it is semi-protected, and there are probably 20-30 threads discussing yesterday's show in the discussion for the entry. However, Oregon doesn't appear anywhere in the entry if I search the page.
There's probably 300 edits to Elephant, too, and the discussion suggests that long-contributing members joined in on the vandalism.
On a side note, I think this is a perfect example of the wikipedia model working successfully. Not a claim that wikipedia is perfect, but the community successfully limiting such "organized" vandalism on such an open site in commendable.
Actually, you've only accounted for about half of the determination of pain. Also, it's the energy that is the same, not the force.
.45 pistol, but I have shot 9mm and that little round will move your arm by probably about 6 inches unless you're particularly tense. And if you are really tense, you'll probably find that shooting the gun actually does hurt your hand. I've also shot rifles as big as .50 Browning. If you don't have the butt tightly up against your shoulder, effectively making your body and the gun one rigid mass that will be accellerated simultaneously, you're going to be in pain when the butt hits you.
Force = pressure * area = mass * accelleration. Assuming the main determinant of how much pain you feel is pressure (a rough but reasonable assumption), then just do some real quick algebra and note that:
Pressure = mass * acceleration / area
Obviously, the more distance you can distribute that accelleration over, the lower the acceleration and hence the lower the force.
As an example some of us may have experienced personally when we were little, consider catching a sharply thrown baseball in a glove and compare that to taking a sharply thrown baseball in the chest (lesson: don't get distracted when playing shortstop). The glove alone has several inches of give while absorbing the energy of the ball (assuming you catch it in the web, rather than on your palm), and if you pay attention you'll also notice most people give with their arm as they catch. In comparison, the ball hitting you in the chest slows down in about the distance it deforms your chest (staggering happens to slowly to really count). Actually, given the extra mass, a fastball is probably a good approximation of a pistol round for momentum as well as for the area that body armor distributes the force of a bullet.
I've never shot a
To sidestep back to the main discussion, a lot of people seem to think of this fluid as magical ("imagine what it could do for car safety," etc). The practical limitation is that it only achieves the extremely high shear rate needed to "lock up" in small areas. If you try to deform a 1 inch square piece of material by 1 inch in 0.01 second, the shear rate is relatively high. If you try to deform a 10 inch square piece by 1 inch, you'll find that the displacement is distributed and the average shear is only about 10% as much as the other case. That's assuming you can deform the two samples in the same manner, which would be pretty tough for any load case other than planar stretching. If you coated a car bumper with this stuff, it would probably just crack at the areas of highest deformation and not react at all at the areas of lowest deformation in an accident. Of course, you could simply fill the entire bumper up with it...
Regarding the efficiency, I fully recognized that when I post the comment you quoted. The main issue, as we both recognized, is the energy density. Most of my post in the original article was addressing that in light of a suggestion that was made about commercial trucks.
More in line with your point, though: Electric motors actually have wonderfully stable efficiency curves over their load and speed ranges compared to ICE engines, but that's not the only factor coming into play. Drag is really important hear. Displacing air takes work which means wasted energy. The amount wasted scales roughly with the square of your velocity. Of course, both electric and ICE vehicles face this problem. The difference is electric motors are relatively efficient regardless of whether you're going fast or slow, so if you go slow, because there's less work accomplished on the ambient air, you waste less energy. With a car, however, the engine efficiency is terrible at low speeds, but increases up to a certain point. Therefore, your car's overall efficiency actually peaks at an intermediate speed between the 0 and redline. In most passenger cars this is around 55-65mph. In an electric car, it would theoretically be much lower.
This doesn't mean that electric cars suck, it just means they're far better suited for city driving than highway driving. Yes, better suited than gasoline cars. The EPA (see fuel economy.gov) fuel cost estimates place electric vehicles at half or less than equivalent gas vehicles. You really just have to get around the range issue.
Also, electric vehicle efficiency also has to include generator and transmission efficiencies. I've never seen a good thorough analysis, but my estimates suggest that electric cars overall do come out slightly ahead in overall efficiency.
My comment about McD's was taken out of context from the original discussion. A branch had started discussing the applicability for long trips, and another poster suggested that common pitstops like fast food joints could offer recharging stations as a bonus to attract more customers. His idea was to go 250 miles at 70 mph would take about 3.5 hours, which would put the driver at about snack time, so why not plug in and charge for 15 minutes while you eat? As I pointed out, that unfortunately doesn't work. He also had a suggestion about commercial freight, leading to the rest of the long comment quoted in today's backslash.
I still maintain that the electric car is poorly suited for long trips. It would theoretically be possible to replace gas stations with battery-swap stations that will stick a freshly charged pack in for a fee, but even that is a little tough. The Tesla's pack weighs about 1000 pounds. You may think, "but it's a roadster, it needs a lot of juice." That's partially true, but really any car with a similar CD, weight, and rolling friction is going to take about the same amount of total energy. The big difference is how fast you drive and if the motor is sized to give peak efficiency at your driving speed.
Ok, so it's 1000 pounds of batteries give or take. Your best bet is probably to break it down into modules that are standard between all vehicles so the stations don't have to stock multiple types. Perhaps each one ways 200 pounds. A commuter car might need 4 of them. A family wagon 5. A delivery van 8-10. Then you drive your car up onto a service ramp, they wheel a jack underneath, drop out the spent units, wheel some fresh ones into place, and jack them up. In addition to standard battery packs, you would also need the manufacturers to make them accessible in a consistent method. Given weight and space concerns, that may be difficult to achieve.
I'm wandering into design questions here, so I'm just going to say the last thing I came to say and leave it at that. Electic cars could work fantastic for commuter purposes, but I think for the time being gas is still our best bet for most other applications. Obviously it's expensive and somewhat inefficient to own a ton of different cars, but concepts like rentals or flex cars could be perfect for filling those rarer needs.
15 minutes on the charger might get you another 15-20 miles. And 220 volts at 70 amps is a pretty hefty 15 kilowatts, so to have a dozen cars sitting at the local McDonalds charging is going to be draining about 180 kW from their coinpurse. That is a serious amount of juice. Also, I'm skeptical that you'll be getting 250 miles at 70 mph. If I remember right, electric motor efficiency and power typically increase with load, but fall off with speed, which makes them awesome for say, a 0-60 run in 3 seconds, but marginal at best for high speed cruising. That 250 mile range estimate is probably at significantly lower speeds.
Big rigs generally run around 5 mpg, but it varies quite a bit around that number depending on the truck, the load, and the speed. Few truckers drive at the most efficient speed because it increases the labor costs significantly.
If you're suggesting running commercial trucks on electricity, forget it for the foreseeable future. It's definitely been considered. Not only is there the conflicting speed issues I mentioned above, but you run up against the energy density limitations of batteries fast. Assuming the numbers from the article are correct (I doubt it...something isn't quite adding up according to my gut) and unrealistically taking the charge/discharge at 100% efficiency, it's storing up 194 MJ. Gasoline holds about 120 MJ/gallon, so the 1000 pounds of batteries (according to the Tesla website) are equivalent to about 1.5 gallons of gas (6.3 pounds/gal). Divide that by an efficiency of around 30% and you've got a 32:1 energy density ratio in favor of gasoline. For a truck to haul the equivalent of 150 gallons of fuel (actually diesel, not gas, but close enough), it would need about 30,000 pounds of batteries. But then you have to go farther and take into account that 2/3's of its cargo capacity has been replaced by fuel, so you need to make 3 times the number of trips. And you've got a lot of trucks either sitting idle recharging or having their 30,000 pounds of batteries swapped out every few hundred miles.
Obviously these are really rough numbers, but other engineers have already looked at the idea in more detail and rejected it.
I'm not trash-talking the Tesla. It looks like a lot of fun, but like all sports cars, it's a toy and not a good comparison for commercial trucking. Most of a car's weight is itself, be it gas or electric. Most of a truck's weight is it's cargo.
For the record, I think electric can work extremely well for short range commuting (5-10 miles on city streets), but if you travel far, you'll realistically be looking at gas.