This parallels the "Big Tobacco" cases. The oil companies are the ones who have profited and lied about the side effects of their product. In fact, it is burning coal, not oil, that is the main cause of the CO2 emissions that contribute to the anthropogenic component of global warming.
In fact, the history of Antarctic exploration is filled with accounts of equipment that failed even though it worked perfectly well in less harsh environments than Antarctica. Designing for Antarctica is non-trivial.
And the environment of Antarctica is benign compared to Mars.
Out of curiosity, did anyone look at piezo electric or electrostatic methods? How did they fare?
Yeah, both of these were looked at. We thought about miniature piezo vibrators on the cells, but didn't actually get to the point of doing any tests under Mars conditions. We did a bit of work with electrostatics-- in fact, the mitigation technique I like best right now uses a DC glow discharge ("Paschen discharge") which is pretty easy to start at Mars pressure, very near the Paschen curve minimum.
The optimum design would be nothing like a conventional car windshield wiper. Think closer to a free-spinning ostrich-feather duster
What are the triboelectric properties of ostrich feathers? If rubbing an ostrich feather across a solar panel charges up the panel electrostatically (and think of rubbing something on Mars like petting your cat in the middle of a very cold winter, except Mars is really really dry) you are in deep trouble. (obSF: "Dust Rag," Hal Clement).
How do you sterilize an ostrich feather to get it past the planetary protection protocol?
What is your failure-mitigation mechanism for the case the mechanism jams when the feather is halfway across the solar panel? (keep in mind that shadowing just one solar cell in a string will take the entire string off line.)
driven by a magnetic actuator
The dust on Mars is preferentially attracted to magnets.
Mars is very cold, and very dry, and very dusty. What are you proposing to use to lubricate this mechanism? How are you keeping it from jamming? What's your plan to ensure that the acoustic environment inside the launch shroud doesn't vibrate it until the shaft bends? (That long ostrich feather looks like a cantelever that's going to resonate like heck. Tie downs? OK, another few moving parts; more failure modes, more wires connecting to D/A lines connecting to the computer.)
that is automatically pulled clear of the panels by gravity. That's one moving part, gravity doing half your work for you,
I don't even know what you mean here. There's no free lunch, even on Mars; if you have weights and pulleys moving it one way, you need exactly that much more energy to move it the other way.
and since it doesn't rain on Mars there would be a chance of breaking within the first ten years of continuous use of close to zero.
Failure analysis is a difficult task, and it's the failure modes that you don't think of that kill you. I'm hard-pressed to think of mechanical devices that work reliably for ten years with no servicing in severe environments on Earth, and you're proposing close to zero chance of breaking on Mars. My car's windshield wipers get a little unreliable at merely 0F; I don't think I'd like to claim "no chance of failure" at, say, -50.
....although it may seem like it, my point here is not merely to poke holes at superficial solutions (to be fair, you did say "off the top of my head."). The point is that space is not like Earth, and there really are reasons that it is harder to do things in space than it is on Earth. Something like you propose probably could be made to work, but your offhand thought that oh, it would be simple and cheap and reliable is just offbase.
It's worth keeping in mind that the causal relationship may very well go the other way-- people who are seriously depressed lose their interest in hobbies or going out and meeting people, not the other way around.
We actually had built a dust experiment to test out some methods of removing dust. It had been scheduled to fly on the Mars-2001 Surveyor Lander, but the 2001 lander mission was cancelled after the failure of the 1999 Polar Lander (which used the same basic spacecraft design). In fact, we talked about dust removal technology for the MER, but it simply turned out that the most reliable solution was to increase the size of the panels so that they would still be at nominal power after 90 days worth of calculated dust accumulation. (My Pathfinder data showed about a quarter of a percent loss of power due to dust per (Martian) day, for what it's worth, but the longer term data looked hint that it was leveling out with time). There's just a lot of reliability in the no-moving-parts solution, and as a bonus, it gave the rover quite a bit of power margin at landing (and, in fact, after landing too-- the dust-related power loss in fact does tail off.)
With that said, let me note that dust removal is probably a bit harder than you realize. The optical data showed that suspended dust is extremely fine-- the cross-section weighted average particle radius is about 2.5 microns, so these particles are about the size of the particles in tobacco smoke. Particles this fine are predicted to adhere extremely well, by van der Waals and electrostatic forces. Picture trying to use your windshield wipers to clean the dust off your windshield, without using the wiper fluid. (and wiper fluid is tricky on Mars, too; you need it to stay liquid for long enough to run the wiper, and neither evaporate or freeze before it hits the panel). And blowing dust off is very tricky-- the atmospheric pressure is less than 1% that of Earth's. We could carry fluid, or compressed gas, but those would be consumables-- and if we had designed the mission and budgeted consumables for a 90 sol lifetime, we'd have run out of them years ago anyway, so we'd be in the same position we're in now anyway.
A feather duster might work, but feathers almost certainly violate the planetary protection policy:)
And for that matter, there's nothing at least in the summary that says anything about orbit... just space.
The article specifically states that he's planning on sending it into orbit.
Not just space. Orbit.
Indicating that he doesn't have a clue.
... for reference, in regard to the earlier thread, escape velocity is in fact 1.414 times greater than orbital velocity. (from the virial theorem, if it matters).
I have to say it rather cheeses me off when Slashdot wastes bandwidth on idiocy that doesn't pass back of the envelope calculations. The CBC can waste space on this, since after all, they have to fill their airtime with something, but/. claims to be "news for nerds" and that should mean, news for people who can do a back of the envelope calculation.
Clearly the professors (Markus Zahn and at least one other) have studied the invention and cannot explain the result.
To the contrary. If you actually read the article, it stated that he had not yet studied it and did not have an opinion.
It's hard to tell exactly what's going on-- the first thing I'm wondering about is whether he's collecting stray fields (the modern world is full of electromagnetic fields)-- but I am, in fact, impressed with the fact that he's actually going to MIT and showing it to people asking for an opinion from people who have a good understanding of science. That's the right step; good move.
That might work... except that I need about 50 password (and, yes, I make them all different)... and they all have different schedules for being changed... and they all have different allowable lengths (some can't be longer than 8 characters... some can't be shorter than 8 characters)... and they all have different specifications for what characters they must contain, and what characters they must not contain (some accounts require special ch@r@c+er$... some can't accept them... some can't accept anything but Caps and smalls)...
Exactly! As far as I can tell, the security policy here actually makes us less secure with their idiotic mandatory policies that passwords be changed frequently, and have numbers and garbage characters so that they can't be memorized. This guarantees that pretty much everybody writes down their passwords-- they have to. What an idiotic policy!
What in the world is the alleged security benefit of a requirement for frequent password changes? I assume that they are thinking of stopping a brute-force attack. But that'd dumb, because of course any given password change is just as likely to change the password into the range currently under attack as it is to change it out of the range under attack. Password changes don't affect the differential probability of a brute force attack from succeeding at all. Even if the hacker is focussed on breaking just one account (instead of, say, attacking ten thousand accounts) and has unlimited time to do it, the average time to break in is independent of whether the password changes frequently or not.
If I were making a security policy, I'd emphasize that the single biggest security hole is using the same password on multiple accounts. (Because then a phishing expedition that hooks one password hooks them all). But security here never seems to care about or mention that.
Jean-Pierre Petit, ex director of CNRS, made a lot of mathematical proof of the possibility of negative mass and the implication. For reference, Bondi showed that negative mass is not incompativle with General Relativity back in 1957:
Bondi, H. "Negative Mass in General Relativity," Reviews of Modern Physics, Vol. 29, No.3, July 1957
The originally traversable-wormhole solutions to general relativity, published by Morris and Thorne (and then later expanded by Morris, Thorne and Yurtsiver) did look like black holes from the outside-- they were, essentially, based on the maximally-extended Flamm embedding of the Schwartzschild solution. But then Matt Visser pointed out that you can embed a wormhole into flat space; the Schwartzschild like part of the solution really is irrelevant to the wormhole feature. So, no, a wormhole doesn't really have to look like, or behave like, a black hole.
This is interesting, but looking at the article, i can't see that it's much different from work that we published over a decade back in a paper where we pointed out properties of wormholes, and noted that they might be visible by the signature of the negative effective mass on the bending of light:
Natural Wormholes as Gravitational Lenses, John G. Cramer, Robert L. Forward, Michael S. Morris, Matt Visser, Gregory Benford, Geoffrey A. Landis. U.C. Irvine even wrote a press release about this paper, which I've put on my website.
It's a little hard to tell from this very brief article, but what he calls "phantom matter" is what other physicists call "exotic matter" or sometimes "negative matter," which violates one of the positive energy-conditions, and thus has negative energy (in some reference frame). Matt Visser's book Lorentzian Wormholes has a lot more technical details about the various formulations of the positive-energy conditions.
Yes, and that's doubly annoying for bicyclists and motorcyclists, who don't trip the sensor at all, so they have to go through a red light if they want to move, or else wait all night.
A better use of cell phones for traffic jam mitigation would be to have every one of the electronic gadgets that regulates traffic (like those "press this to get a walk signal" buttons, too) have a little sign with a number on it to call when it doesn't work...
I wouldn't want to participate in a program that would help the Department of Fatherland Security anyway, they'll probably find some way to get unfettered access to the information. Hmmm.... Trying to think of a rationale that might be used for why Homeland Security would have to want to look at the traffic jam data, they could say that they need the data to practice so that, if it ever happens that a disaster means that they need to evacuate a city, they could develop a system that would allow them to do wo without clogging the streets.
But actually, that would be a good us of the system; if there ever were an evacuation, it would be useful to have a system to reroute around the inevitable traffic jams...
This seems to me to be a failure of NASA as much as Rocketplane Kistler. The objectives appear to be entirely unrealistic. NASA wants two separate companies to develop two separate vehicles capable of unmanned resupply of the ISS
To the contrary. Both of the companies who won the COTS contract had already been developing vehicles-- in Kistler's case, for over a decade. The agreement was for the companies to take low-cost launch vehicles that they were already developing, and adapt them to the NASA needs.
It looks like a win-win situation; these companies have proposed that they can reduce the cost of space access, and are using non-government funding to develop their vehicles. If they succeed, it would be a very beneficial thing for NASA, and for that matter for the whole space industry. Indeed, it's a risky bet-- the history of private space development is littered with the business plans of failed launch ventures, and it really is rocket science-- but the payoff is high, and the money ventured is relatively low.
The problem is that the concept does depend on the companies developing their vehicles with outside funding. And they knew that right from the start; the contract was written that NASA funding would continue if and only if there was external capital supplied, with specific milestones. Kistler had claimed to have outside investors with the funding, but for one reason or another the promised funds kept getting pushed back and back, and the milestones kept slipping into the future.
So what is it that the company who got kicked out did? The agreement was to provide some kick-start funding, contingent on the company gathering private funding to develop the vehicle.
Kistler failed to gather the commitments for private funding within the mutually-agreed period of time.
In any country with over a million or so people, there's sure to always be somebody who claims fraud on any election. The point is that it should be clear to the rest of the people that these claims are crackpot. If the answer is "well, the software claims the election was fair, and we trust the software..." then that doesn't inspire confidence. And if they say that the software's proprietary, you're not allowed to look at what it does... and there's no way to recount, you just have to accept it... that's not good for confidence in the system, even if it actually really is true that the vote counting was fair.
Who the heck's idiotic idea was it that companies could make software to count votes, and then not let anybody look at the software and see what it actually does because it's "proprietary"?
Every failure always looks like a dumb mistake in hindsight. Risking failures is part of the path to succeeding. So, assuming that they learned from their mistakes, I'll cheer Scaled Composites on for actually doing things, even if they sometimes make mistakes. To quote Teddy Rooseveldt: "The only man who makes no mistakes is the man who never does anything."
...or, quoting Rooseveldt in more detail:
It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly; who errs and comes short again and again; because there is not effort without error and shortcomings; but who does actually strive to do the deed; who knows the great enthusiasm, the great devotion, who spends himself in a worthy cause, who at the best knows in the end the triumph of high achievement and who at the worst, if he fails, at least he fails while daring greatly. So that his place shall never be with those cold and timid souls who know neither victory nor defeat."
There are only two life forms, -- eukaryotes, which gather their genetic material in a nucleus, and prokaryotes, such as bacteria
Two? For several decades, I thought most biologists considered life as being divided into three main branches ("domains"): eukaryotes, prokaryotes, and archaea.
Slashdot Mirror
And the environment of Antarctica is benign compared to Mars.
Yeah, both of these were looked at. We thought about miniature piezo vibrators on the cells, but didn't actually get to the point of doing any tests under Mars conditions. We did a bit of work with electrostatics-- in fact, the mitigation technique I like best right now uses a DC glow discharge ("Paschen discharge") which is pretty easy to start at Mars pressure, very near the Paschen curve minimum.
What are the triboelectric properties of ostrich feathers? If rubbing an ostrich feather across a solar panel charges up the panel electrostatically (and think of rubbing something on Mars like petting your cat in the middle of a very cold winter, except Mars is really really dry) you are in deep trouble. (obSF: "Dust Rag," Hal Clement).
How do you sterilize an ostrich feather to get it past the planetary protection protocol?
What is your failure-mitigation mechanism for the case the mechanism jams when the feather is halfway across the solar panel? (keep in mind that shadowing just one solar cell in a string will take the entire string off line.)
driven by a magnetic actuatorThe dust on Mars is preferentially attracted to magnets.
Mars is very cold, and very dry, and very dusty. What are you proposing to use to lubricate this mechanism? How are you keeping it from jamming? What's your plan to ensure that the acoustic environment inside the launch shroud doesn't vibrate it until the shaft bends? (That long ostrich feather looks like a cantelever that's going to resonate like heck. Tie downs? OK, another few moving parts; more failure modes, more wires connecting to D/A lines connecting to the computer.)
that is automatically pulled clear of the panels by gravity. That's one moving part, gravity doing half your work for you,I don't even know what you mean here. There's no free lunch, even on Mars; if you have weights and pulleys moving it one way, you need exactly that much more energy to move it the other way.
and since it doesn't rain on Mars there would be a chance of breaking within the first ten years of continuous use of close to zero.Failure analysis is a difficult task, and it's the failure modes that you don't think of that kill you. I'm hard-pressed to think of mechanical devices that work reliably for ten years with no servicing in severe environments on Earth, and you're proposing close to zero chance of breaking on Mars. My car's windshield wipers get a little unreliable at merely 0F; I don't think I'd like to claim "no chance of failure" at, say, -50.
....although it may seem like it, my point here is not merely to poke holes at superficial solutions (to be fair, you did say "off the top of my head."). The point is that space is not like Earth, and there really are reasons that it is harder to do things in space than it is on Earth. Something like you propose probably could be made to work, but your offhand thought that oh, it would be simple and cheap and reliable is just offbase.
It's worth keeping in mind that the causal relationship may very well go the other way-- people who are seriously depressed lose their interest in hobbies or going out and meeting people, not the other way around.
With that said, let me note that dust removal is probably a bit harder than you realize. The optical data showed that suspended dust is extremely fine-- the cross-section weighted average particle radius is about 2.5 microns, so these particles are about the size of the particles in tobacco smoke. Particles this fine are predicted to adhere extremely well, by van der Waals and electrostatic forces. Picture trying to use your windshield wipers to clean the dust off your windshield, without using the wiper fluid. (and wiper fluid is tricky on Mars, too; you need it to stay liquid for long enough to run the wiper, and neither evaporate or freeze before it hits the panel). And blowing dust off is very tricky-- the atmospheric pressure is less than 1% that of Earth's. We could carry fluid, or compressed gas, but those would be consumables-- and if we had designed the mission and budgeted consumables for a 90 sol lifetime, we'd have run out of them years ago anyway, so we'd be in the same position we're in now anyway.
A feather duster might work, but feathers almost certainly violate the planetary protection policy :)
The article specifically states that he's planning on sending it into orbit.
Not just space. Orbit.
Indicating that he doesn't have a clue.
... for reference, in regard to the earlier thread, escape velocity is in fact 1.414 times greater than orbital velocity. (from the virial theorem, if it matters).
I have to say it rather cheeses me off when Slashdot wastes bandwidth on idiocy that doesn't pass back of the envelope calculations. The CBC can waste space on this, since after all, they have to fill their airtime with something, but /. claims to be "news for nerds" and that should mean, news for people who can do a back of the envelope calculation.
It's hard to tell exactly what's going on-- the first thing I'm wondering about is whether he's collecting stray fields (the modern world is full of electromagnetic fields)-- but I am, in fact, impressed with the fact that he's actually going to MIT and showing it to people asking for an opinion from people who have a good understanding of science. That's the right step; good move.
That might work... except that I need about 50 password (and, yes, I make them all different)... and they all have different schedules for being changed... and they all have different allowable lengths (some can't be longer than 8 characters... some can't be shorter than 8 characters)... and they all have different specifications for what characters they must contain, and what characters they must not contain (some accounts require special ch@r@c+er$... some can't accept them... some can't accept anything but Caps and smalls)...
What in the world is the alleged security benefit of a requirement for frequent password changes? I assume that they are thinking of stopping a brute-force attack. But that'd dumb, because of course any given password change is just as likely to change the password into the range currently under attack as it is to change it out of the range under attack. Password changes don't affect the differential probability of a brute force attack from succeeding at all. Even if the hacker is focussed on breaking just one account (instead of, say, attacking ten thousand accounts) and has unlimited time to do it, the average time to break in is independent of whether the password changes frequently or not.
If I were making a security policy, I'd emphasize that the single biggest security hole is using the same password on multiple accounts. (Because then a phishing expedition that hooks one password hooks them all). But security here never seems to care about or mention that.
Yes, same Benford.
The originally traversable-wormhole solutions to general relativity, published by Morris and Thorne (and then later expanded by Morris, Thorne and Yurtsiver) did look like black holes from the outside-- they were, essentially, based on the maximally-extended Flamm embedding of the Schwartzschild solution. But then Matt Visser pointed out that you can embed a wormhole into flat space; the Schwartzschild like part of the solution really is irrelevant to the wormhole feature. So, no, a wormhole doesn't really have to look like, or behave like, a black hole.
It's a little hard to tell from this very brief article, but what he calls "phantom matter" is what other physicists call "exotic matter" or sometimes "negative matter," which violates one of the positive energy-conditions, and thus has negative energy (in some reference frame). Matt Visser's book Lorentzian Wormholes has a lot more technical details about the various formulations of the positive-energy conditions.
A better use of cell phones for traffic jam mitigation would be to have every one of the electronic gadgets that regulates traffic (like those "press this to get a walk signal" buttons, too) have a little sign with a number on it to call when it doesn't work...
But actually, that would be a good us of the system; if there ever were an evacuation, it would be useful to have a system to reroute around the inevitable traffic jams...
To the contrary. Both of the companies who won the COTS contract had already been developing vehicles-- in Kistler's case, for over a decade. The agreement was for the companies to take low-cost launch vehicles that they were already developing, and adapt them to the NASA needs.
It looks like a win-win situation; these companies have proposed that they can reduce the cost of space access, and are using non-government funding to develop their vehicles. If they succeed, it would be a very beneficial thing for NASA, and for that matter for the whole space industry. Indeed, it's a risky bet-- the history of private space development is littered with the business plans of failed launch ventures, and it really is rocket science-- but the payoff is high, and the money ventured is relatively low.
The problem is that the concept does depend on the companies developing their vehicles with outside funding. And they knew that right from the start; the contract was written that NASA funding would continue if and only if there was external capital supplied, with specific milestones. Kistler had claimed to have outside investors with the funding, but for one reason or another the promised funds kept getting pushed back and back, and the milestones kept slipping into the future.
Kistler failed to gather the commitments for private funding within the mutually-agreed period of time.
this link has some info and cool pictures.
Who the heck's idiotic idea was it that companies could make software to count votes, and then not let anybody look at the software and see what it actually does because it's "proprietary"?
I have to say, I read the headline and really wondered why slashdot was interested in the Boy Scouts of America.
...or, quoting Rooseveldt in more detail:
--Theodore Roosevelt.
Two? For several decades, I thought most biologists considered life as being divided into three main branches ("domains"): eukaryotes, prokaryotes, and archaea.