I signed off a purchase order last month for a quarter of a million pounds (sterling) of density measurement (equipment rental and the technicians to run it). Please tell me what your techniques are. If we can split the difference and pocket it, we'll both be rich.
Density is mass over volume. The volume is easy enough to get by telescopic examination. How are you going to weigh it? Be explicit in your assumptions.
That alone gives a fairly good indication of solidity.
Density gives a good indication of "solidity". It does? At the extremes, yes ; osmium is harder than aerogel. But at intermediate values, it's not so useful. (That's not the reason for spending money on density measurements above, but the data is already caught. Density is not a terribly good proxy for drillability. See figures 1 + 2 in www.northbasinenergy.com/media/research/SPE_106571.pdf for data in the public domain. I've no reason to think that other measures of rock "strength" are better correlated ; rocks are messy subjects.)
As you wish: Coming to a position of relative rest quickly takes a lot of energy.
This sentence makes no sense.
It makes perfect sense to me. There is a problem with your understanding of physics.
There is no universal reference frame for position. (Velocity and acceleration are first and second differentials of position w.r.t. ("with respect to") time, so the same comments apply to them.) There is no centre to the universe, or place which is the origin of measurement. Therefore all positions are relative to some chosen origin. In this case, we may choose the asteroid as the origin.
Your interacting spacecraft starts at Earth, which is a long way from the asteroid but moving towards it ; it needs to get closer to the asteroid, then it needs to come to a halt w.r.t. the asteroid. So, it's velocity compared to the asteroid is going to have to increase to bring the two closer, and a change of velocity defines an acceleration. Newton "F=m.a" ; there are forces needed to achieve that. Then the spacecraft will need a (relatively) large acceleration in the opposite direction (remember - momentum, velocity and acceleration are all vectors, not scalars) to reduce it's velocity compared to the asteroid to almost zero. That again requires large forces and so a lot of energy.
Clearer now?
You could, if you so desire, choose your origin to be in a galaxy receding from Earth at 0.9 of Legal Max ; it would make the maths more complex (relativistic momentum? Euchh!) but the results would be the same.
We were doing this sort of stuff in compulsory science classes at age 13-14. You can't have passed your science exams without being able to work this sort of thing out.
Incidentally, the word "quickly" in the sentence you're upset with is superfluous. The energy required is the same whether it happens quickly or slowly.
Yup, a good squirt with super glue or chewing gum and then you can mount a few big ass engines on it
Is that Kryptonite super gum, or Unobtanium chewing glue?
Maybe that's being a bit harsh. But if you think about how long it took to come up with the repair patches and glue for the space shuttle... it's a bit more demanding than you make it sound. (Sorry ; Dad's a polymer chemist. I've had to put up with "it's not as easy as that" for most of my life.
Trivial? Maybe not quite trivial, but not exactly difficult. A decent clock ; a decent telescope and mounting (surprisingly made with clockwork-related technologies) ; some well-understood calculations. We've been doing it, successfully, for several centuries, and it's now fairly well automated.
In contrast, at my specimen range (1000km from ground zero), the 1km impactor I wouldn't see the fireball, while the 10km impactor I'd probably be burned to death with radiant heat like a gas burner on full, 10cm from my skin, for nearly a half-hour.
It's not a detailed calculation, but it's reasonable.
And if you scatter the stuff enough, it won't even hit the earth.
FTFY
And if you don't sufficiently scatter the impactor - because we do not know what the physical properties and internal construction of Joe Random Asteroid is?
If we've got the luxury of 10 or 20 years to study an incoming object, learn about it's structure, perhaps throw some fridge-sized lumps of copper at it (q.v. the Deep Impact mission) to do some asteroid-seismology... then that's great. And in that time interval we can implement a gravity tow effort without increasing the hazard the impactor represents.
Then, if the gravity tow isn't enough, we can put up another towing vehicle (more mass ; more force). Or if we've really no other option, we might have to deploy the nukes (probably in stand-off mode, I'd suspect ; much more controllable than a contact explosion!).
What did that Greek doctor guy say a couple of thousand years ago? "First, do no harm." Less stupid than some of today's crop of Slashdolts.
If we've only got a year or two before impact... we're probably pretty well fucked. We'd probably not see it before it was about to hit. We don't spend anything like enough on early threat detection.
Even if all the pieces are so small that none reach the surface, all of that energy is just turned into a heat flash, shock wave, and ends up dumped into the atmosphere.
Yep. Agreed.
The Earth's surface would be pretty much slagged regardless.
Now, it's not actually quite that bad. Life on the Earth's surface would be pretty grim. Life in burrows, in caves, in the soil... much better situation. Life in the seas however - relatively mild effects. (That's one of the puzzling aspects of the putative "dinosaur killer" impactor - the KT extinction event had drastic effects on some groups of marine organisms, but not others.) Even in the LHB (Late Heavy Bombardment, when most of the Lunar maria were formed), the likelihood is that the deeper ocean basins (the Earth had pretty much it's current complement of water by this time) remained hospitable to life. If you call 50degC water and lots of hydrothermal activity "hospitable". Strangely, the root of the "tree of life" contains organisms that are able to survive and thrive in hot, acidic, mineral-laden water. Interesting that.
It completely overwhelms the atmosphere's ability to act as a heat sink.
The atmosphere is equivalent to about 10m of depth of water, and 3 to 5m of soil. From which one can make some uncontroversial predictions.
The problems that need addressing are not the "it'll happen in 20 years" ones. It's the "it'll happen in 2 years" ones. So... if the explosion doesn't work, you've now got (say) 18 months to implement another solution on a dozen major impactors and a small cloud of debris from the explosion heading off on non-intersecting orbits.
But at the moment, we don't have a workable scheme to deal with any detected impactor. It's "head between the legs and kiss your arse goodbye" time.
I make it about 65 billion tonnes, for a dinosaur killer scale asteroid (I am not 100% convinced that the Chixulub impactor actually killed off the dinosaurs ; but it would sure as hell been a bad hair day for them.) of 5km diameter, and assuming a net density of 1tonne/ cubic metre. Which would be high for a (water-ice) comet but not far off right for a "rubble-pile" asteroid.
If you've got years of warning, then you don't need to do things like throwing bombs around. You've got the time to use less drastic techniques.
Even a solid rock of extinction size would do less damage if you break it up into more than one piece, and in doing so deflect significant chunks of it such that they would not even hit the earth.
The only important effect would be if you actually get some of the pieces to not hit the Earth. Which you can do if you've got years and multiple orbits of warning. If you've got a few days or weeks warning warning, then you're also not going to have time for the debris to disperse sufficiently.
But don't worry ; in that circumstance the gravity tow idea isn't going to work either. For days or weeks everyone on the planet who cares to know is going to be aware of the date and time of their death, to an accuracy of a few minutes.
Most of the rocky bodies we've investigated and photographed are loose creations of material which would most likely burn up in the atmosphere if you simply spread them out a bit.
Two issues arise from your characterisation : firstly, these "rubble piles" are not very good at transmitting shocks. If you plant your nuke on the surface, the rocks near the nuke are going to get a big shove, but as they project away from the explosion point, they'll cut through the rubble and impart relatively little energy to the rest of the pile. Which is why many of the imaged asteroids have seemingly gigantic craters on them from large impacts which should have disintegrated the asteroids. If they were rigid bodies. But they're not ; they're rubble piles which accommodate the impact energy by internal rearrangement.
(Incidentally, this structural weakness is part of the reason that you're nuke is going to detonate on the surface. You're not going to be able to dig a pit deep enough to get the bomb significantly (several kilometres) down into the rock. How you're going to anchor your drilling equipment to such a weak substrate is just one of the impossible things you need to do before breakfast.)
Secondly. you're missing a point about "burning up in the atmosphere". As you "burn up" each impactor, the air gets hotter. With a lot of impactors, all of the atmosphere gets hot. With enough (a multi-kilometre impactor disintegrating, or the ejecta from one such re-impacting on the rest of the planet), all of the atmosphere gets hot. Hot enough to burn. Hot enough to cause "flash-over" fires all around the planet. (Your fire-fighting training at work included "flash-over"? When the radiated heat from a fire in area causes the surface of other objects to start burning directly. Mine did. I've friends who lost parts of their faces to a flash-over fire at work; it's not nice. 167 of our colleagues died that night.)
The sums have been done - over a decade ago - and published. You have had a decade to disagree and prove them wrong. Where's your paper?
You fire your retro rockets to push yourself away from the rock, in the process pushing the rock away from you, back towards it's original destination.
This is only a problem if your retro-rocket plumes impact on the rock you're trying to tow around. So, you arrange your retro rockets to fire in pairs at (say) pi/4 radians to the desired line of thrust, and at sqrt(2) of the required power.
(Exact angles and forces will need refinement for the exact circumstances. How big is the asteroid ; how close do you need to get ; how much time do you have to achieve the deflection. In practice, I'd suspect that you'd use 3 thrusters on orthogonal axes, which is a common configuration on satellites already for these very reasons.)
Do them all, see what works best, then do that for the next one.
The discussion is specifically about "extinction level" impactors. Get it wrong first time and you do not get a second chance.
This game doesn't have a "save" option. When you die, it's permanent. You don't get to do a rehearsal unless you spend some of your development budget and time on doing a rehearsal. There is no guarantee that you will have time to do a rehearsal. Or indeed, to actually do anything. Nature doesn't care.
And since the computers are said to be identical, why the desire to move back to A?
The desire, as I read it, is to have the "A" side back available as a backup. So, in the event of another fault (hypothesis : cosmic ray hit) on the "B" side, then they'll be able to recover the rover's operational capability using the "A" side.
UK banks are terrible when it comes to "there be dragons" parts of the world.
Agreed. When I was getting married, my Russian wife needed to set up a bank account in the UK. Unsurprisingly. Off to Royal Bank of Scotland, who took the detailes, examined the marriage certificate, passport, visa, NI card... filled in forms. And then sent her chequebook and bank cards to her OLD address in Siberia.
Pathetic. That's "Royal Bank of Scotland", for anyone who missed it the first time round.
my own country (UK) have enough renewable resources to cover all our needs if fully developed. Scotland in particular is on target to be 100% renewable by 2020
And how are England, Wales and Northern Ireland going to manage if, as seems entirely plausible, the people of Scotland vote for independence in the 2014 referendum?
FWIW, in the 30 years that I've been living in Scotland, I've never yet heard a Scots Nationalist give a coherent answer to the Shetland question. If it's good for Scotland to take control of the majority of the north Sea oil production and secede from the UK, then it is exactly as good for Shetland to secede from the newly independent Scotland, and take over half the (UK sector's) oil reserves with them. Maybe they'd join up with the Noggins - the two nations have always got on well.
I get a vote. I haven't decided which way to vote. I suspect the vote is going to be quite close.
(On a sideline... if Scotland breaks up the UK, would the English and Welsh be stupid enough to stay entangled with the mess that it Northern Ireland? That's totally unrelated to this topic. But it's amusing to consider the apoplectic fits that raising the question would provoke in "Loyalists.")
Technically i am somewhat pro nuclear. However that is not the same as saying i trust the companies or governments or even the IAEA for that matter to do nuclear safe. And we still are not dealing with the waste we already have.
Which is why, for decades, I've been proposing that where ever possible, nuclear waste should be stored in locations that would guarantee that the first people to die if it is mis-handled are the politicians in charge of it.
In Britain, that means a relatively shallow waste repository in the London Clay Formation, with the entrance through the House of Commons. In Paris, it's not so clear. You'd probably have to have the repository much deeper in the "Greensand" (equivalent ; I've not drilled in the Paris Basin ; did I say that I'm a geologist?) to be below the aquifers in the Chalk Group. Berlin... sorry, I know nothing about it's regional geology. Ditto for Washington DC.
But the important principle is simple : politicians will only pay for proper maintenance of waste dumps if they will be the first to die. So, you arrange for the politicians to be the first to die. Painfully, if possible. In the words of the meerkat, "Simples!"
we could always use an old frack-hole and the broken-up shale could be a heat-exchanger?
Wearing my geological hard-hat... the idea is starting from as poor position. Shales are sedimentary rocks, deposited in water, so they formed at low temperature (a few tens of degrees centigrade, no higher). They'll have got hotter with burial, but that will have been heat coming in from elsewhere (a small contribution from local radiogenic heat, but even the "hottest" shales, 300+API, are only a few hundreds of ppm U+Th+K). So, to get best efficiency it would almost always be better to go to the source of that heat. You'd then get a higher temperature difference and thus higher possible efficiency.
Carnot covered this in the foundations of thermodynamics nearly 2 centuries ago and it's not wrong.
Getting a large enough volume of rock sufficiently finely fractured to release enough heat for long enough to amortise the energy cost of building the wells... that's the problem. You need as high a rock temperature as possible (for efficiency, above) at as shallow a depth as possible (to reduce the investment of energy, materials etc in the well). As someone mentioned up-thread - this adds up to being in a volcanic region, for optimal geothermal energy production. Which doesn't mean that it won't work elsewhere, just that it won't be optimal.
While still wearing my geologist's hard hat, and packing my bags to go and work on a Norwegian oil well tomorrow afternoon, I don't give a shit about whether I'm working on an oil well, a gas well, a water/ mud/ CO2 injection well, or a geothermal well. They all need geological planning and on-site supervision for well safety and optimisation. Which is my pay cheque, thank you. Not that saying that is going to quiet the conspiracy nutcases.
Quite possibly, banned.
If you are in a working environment where flammable or explosive atmospheres are present as a normal part of normal operations, or as a part of "foreseeable emergency" operations, then the normal situation is to have a gas-proof, purged (from a known-clean air supply under positive pressure) power control box which monitors several flammable gas monitors in the area under consideration. If the gas monitors detect non-trivial amounts of flammable gas in the purged zone, or in the supply of "clean" air to the purged zone, then the system shuts down the power. Immediately. Within one cycle of AC. No "if", no "but", no "maybe", no "can I finish this write". No polite prompt that "The system is going down for power down now" followed by a shrinking white dot. Power is off NOW.
Multiple people have died for getting that wrong. Hundreds of millions of dollars of equipment have been burned or sunk. Lawsuits have occurred. Which is why the sparkies take it seriously.
I no longer work in such areas routinely, but I spent 20 years using and maintaining such equipment, including those gas detectors. Shit, they can be pernickety, particularly the gas detectors, and particularly when they get dosed with seawater spray that comes through when the waves are hammering 20m up the side of the vessel.
One of the companies that I work with routinely issues all of it's field staff with specialised laptops suitable to this environment. The staff must use one of these machines to log into the company network (this is enforced by spyware root-kitted in on the installation image and locked behind password-protected hardware (the "unit" has routers that refuse network service to computers that aren't running the spyware). The wifi cards are removed (people at this company have died through violation of radio silence rules when handling explosives ; so that possibility is eliminated ; it's easier than going back to court to explain why someone else has died) and to maintain the immediate effectiveness of the power shutdown systems, the batteries are removed and the battery terminals are hot-glued over so that they can never be re-fitted. (I guess they haven't worked out a procedure to get around the CMOS backup batteries. But being soldered into a PCB, they're probably unlikely to spark themselves.)
"No UPS" is a perfectly acceptable, expectable industrial situation. I've worked under such circumstances for nearly 30 years.
The legislative framework in which my work environment developed was derived from electrical equipment in coal mines, and the bodies that certify equipment designs were founded in the 1930s. Flammable atmospheres and electrical equipment are not a new combination, and lots of solutions have been tried. The rarity of such explosions is a testimony to the industry having stopped (mostly) arguing about the costs of this approach. Occasionally someone tries to cut corners - through ignorance or cost-cutting. I'd bet... TWO... pints of beer that the 29 bodies in the Pike River mine died due to short-cutting something in this regulatory regime. Though I now see that the final report has been released and prosecutions have occurred, so I suppose I've got some reading to do (my suppositions are reasonable. See item one of this list from the report on the homicides : "It is not possible to be definitive, but potential ignition sources include arcing in the mine electrical system, a diesel engine overheating, contraband taken into the mine, electric motors in the non-restricted part of the mine and frictional sparking caused by work activities."). Not a problem I have to work with in detail any more - my job is (partly) to avoid generating those flammable atmospheres in the first case (which clearly wasn't done
Lead-containing silicate glasses are relatively reactive, chemically. Don't do it - send them for proper disposal. If nothing else, within a short time (years to decades at most), a dry-stored landfill of CRT tubes, broken or not, is going to be worth smelting. To reclaim the lead.
No network content (because no network connection) ; no way for billing to occur ; no problem.
I've never paid for an add-on in any game, ever. Is it common?
Slashdot Mirror
It can? Do enlighten us further.
I signed off a purchase order last month for a quarter of a million pounds (sterling) of density measurement (equipment rental and the technicians to run it). Please tell me what your techniques are. If we can split the difference and pocket it, we'll both be rich.
Density is mass over volume. The volume is easy enough to get by telescopic examination. How are you going to weigh it? Be explicit in your assumptions.
Density gives a good indication of "solidity". It does? At the extremes, yes ; osmium is harder than aerogel. But at intermediate values, it's not so useful. (That's not the reason for spending money on density measurements above, but the data is already caught. Density is not a terribly good proxy for drillability. See figures 1 + 2 in www.northbasinenergy.com/media/research/SPE_106571.pdf for data in the public domain. I've no reason to think that other measures of rock "strength" are better correlated ; rocks are messy subjects.)
It makes perfect sense to me. There is a problem with your understanding of physics.
There is no universal reference frame for position. (Velocity and acceleration are first and second differentials of position w.r.t. ("with respect to") time, so the same comments apply to them.) There is no centre to the universe, or place which is the origin of measurement. Therefore all positions are relative to some chosen origin. In this case, we may choose the asteroid as the origin.
Your interacting spacecraft starts at Earth, which is a long way from the asteroid but moving towards it ; it needs to get closer to the asteroid, then it needs to come to a halt w.r.t. the asteroid. So, it's velocity compared to the asteroid is going to have to increase to bring the two closer, and a change of velocity defines an acceleration. Newton "F=m.a" ; there are forces needed to achieve that. Then the spacecraft will need a (relatively) large acceleration in the opposite direction (remember - momentum, velocity and acceleration are all vectors, not scalars) to reduce it's velocity compared to the asteroid to almost zero. That again requires large forces and so a lot of energy.
Clearer now?
You could, if you so desire, choose your origin to be in a galaxy receding from Earth at 0.9 of Legal Max ; it would make the maths more complex (relativistic momentum? Euchh!) but the results would be the same.
We were doing this sort of stuff in compulsory science classes at age 13-14. You can't have passed your science exams without being able to work this sort of thing out.
Incidentally, the word "quickly" in the sentence you're upset with is superfluous. The energy required is the same whether it happens quickly or slowly.
Is that Kryptonite super gum, or Unobtanium chewing glue?
Maybe that's being a bit harsh. But if you think about how long it took to come up with the repair patches and glue for the space shuttle ... it's a bit more demanding than you make it sound. (Sorry ; Dad's a polymer chemist. I've had to put up with "it's not as easy as that" for most of my life.
Hayabusa. en.wikipedia.org/wiki/Hayabusa ; NEAR en.wikipedia.org/wiki/NEAR_Shoemaker
www.nasa.gov/deepimpact
Trivial? Maybe not quite trivial, but not exactly difficult. A decent clock ; a decent telescope and mounting (surprisingly made with clockwork-related technologies) ; some well-understood calculations. We've been doing it, successfully, for several centuries, and it's now fairly well automated.
Do you know the impact stimulator? http://impact.ese.ic.ac.uk/ImpactEffects/
Plugging in 1 and 10km asteroids, impacting crystalline rock at 25km/s (middle velocity) (full parameters in this link : http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=1000&distanceUnits=1&diam=10&diameterUnits=2&pdens=&pdens_select=1500&vel=25&velocityUnits=1&theta=90&wdepth=&wdepthUnits=1&tdens=2750 )... the transient craters would be 3km and 23km respectively. The latter would expose the mantle - temporarily. But within a matter of minutes to hours, collapse of the crater walls and fallback of ejecta would cover it up again.
In contrast, at my specimen range (1000km from ground zero), the 1km impactor I wouldn't see the fireball, while the 10km impactor I'd probably be burned to death with radiant heat like a gas burner on full, 10cm from my skin, for nearly a half-hour.
It's not a detailed calculation, but it's reasonable.
FTFY
And if you don't sufficiently scatter the impactor - because we do not know what the physical properties and internal construction of Joe Random Asteroid is?
If we've got the luxury of 10 or 20 years to study an incoming object, learn about it's structure, perhaps throw some fridge-sized lumps of copper at it (q.v. the Deep Impact mission) to do some asteroid-seismology ... then that's great. And in that time interval we can implement a gravity tow effort without increasing the hazard the impactor represents.
Then, if the gravity tow isn't enough, we can put up another towing vehicle (more mass ; more force). Or if we've really no other option, we might have to deploy the nukes (probably in stand-off mode, I'd suspect ; much more controllable than a contact explosion!).
What did that Greek doctor guy say a couple of thousand years ago? "First, do no harm." Less stupid than some of today's crop of Slashdolts.
If we've only got a year or two before impact ... we're probably pretty well fucked. We'd probably not see it before it was about to hit. We don't spend anything like enough on early threat detection.
Yep. Agreed.
Now, it's not actually quite that bad. Life on the Earth's surface would be pretty grim. Life in burrows, in caves, in the soil ... much better situation. Life in the seas however - relatively mild effects. (That's one of the puzzling aspects of the putative "dinosaur killer" impactor - the KT extinction event had drastic effects on some groups of marine organisms, but not others.) Even in the LHB (Late Heavy Bombardment, when most of the Lunar maria were formed), the likelihood is that the deeper ocean basins (the Earth had pretty much it's current complement of water by this time) remained hospitable to life. If you call 50degC water and lots of hydrothermal activity "hospitable". Strangely, the root of the "tree of life" contains organisms that are able to survive and thrive in hot, acidic, mineral-laden water. Interesting that.
The atmosphere is equivalent to about 10m of depth of water, and 3 to 5m of soil. From which one can make some uncontroversial predictions.
But at the moment, we don't have a workable scheme to deal with any detected impactor. It's "head between the legs and kiss your arse goodbye" time.
We don't have a strategy for dealing with those.
We don't even have a hint of a strategy for dealing with those.
I make it about 65 billion tonnes, for a dinosaur killer scale asteroid (I am not 100% convinced that the Chixulub impactor actually killed off the dinosaurs ; but it would sure as hell been a bad hair day for them.) of 5km diameter, and assuming a net density of 1tonne/ cubic metre. Which would be high for a (water-ice) comet but not far off right for a "rubble-pile" asteroid.
If you've got years of warning, then you don't need to do things like throwing bombs around. You've got the time to use less drastic techniques.
The only important effect would be if you actually get some of the pieces to not hit the Earth. Which you can do if you've got years and multiple orbits of warning. If you've got a few days or weeks warning warning, then you're also not going to have time for the debris to disperse sufficiently.
But don't worry ; in that circumstance the gravity tow idea isn't going to work either. For days or weeks everyone on the planet who cares to know is going to be aware of the date and time of their death, to an accuracy of a few minutes.
Two issues arise from your characterisation : firstly, these "rubble piles" are not very good at transmitting shocks. If you plant your nuke on the surface, the rocks near the nuke are going to get a big shove, but as they project away from the explosion point, they'll cut through the rubble and impart relatively little energy to the rest of the pile. Which is why many of the imaged asteroids have seemingly gigantic craters on them from large impacts which should have disintegrated the asteroids. If they were rigid bodies. But they're not ; they're rubble piles which accommodate the impact energy by internal rearrangement.
(Incidentally, this structural weakness is part of the reason that you're nuke is going to detonate on the surface. You're not going to be able to dig a pit deep enough to get the bomb significantly (several kilometres) down into the rock. How you're going to anchor your drilling equipment to such a weak substrate is just one of the impossible things you need to do before breakfast.)
Secondly. you're missing a point about "burning up in the atmosphere". As you "burn up" each impactor, the air gets hotter. With a lot of impactors, all of the atmosphere gets hot. With enough (a multi-kilometre impactor disintegrating, or the ejecta from one such re-impacting on the rest of the planet), all of the atmosphere gets hot. Hot enough to burn. Hot enough to cause "flash-over" fires all around the planet. (Your fire-fighting training at work included "flash-over"? When the radiated heat from a fire in area causes the surface of other objects to start burning directly. Mine did. I've friends who lost parts of their faces to a flash-over fire at work; it's not nice. 167 of our colleagues died that night.)
The sums have been done - over a decade ago - and published. You have had a decade to disagree and prove them wrong. Where's your paper?
This is only a problem if your retro-rocket plumes impact on the rock you're trying to tow around. So, you arrange your retro rockets to fire in pairs at (say) pi/4 radians to the desired line of thrust, and at sqrt(2) of the required power.
(Exact angles and forces will need refinement for the exact circumstances. How big is the asteroid ; how close do you need to get ; how much time do you have to achieve the deflection. In practice, I'd suspect that you'd use 3 thrusters on orthogonal axes, which is a common configuration on satellites already for these very reasons.)
The discussion is specifically about "extinction level" impactors. Get it wrong first time and you do not get a second chance.
This game doesn't have a "save" option. When you die, it's permanent. You don't get to do a rehearsal unless you spend some of your development budget and time on doing a rehearsal. There is no guarantee that you will have time to do a rehearsal. Or indeed, to actually do anything.
Nature doesn't care.
The desire, as I read it, is to have the "A" side back available as a backup. So, in the event of another fault (hypothesis : cosmic ray hit) on the "B" side, then they'll be able to recover the rover's operational capability using the "A" side.
To misquote ... whoever actually wrote Star Wars ... "You are not the field service engineer we're looking for!"
Real Mars rover field service engineers go out, fix the falt, and then terraform the planet. With nowt but a roll of duct tape and a can of WD40.
Agreed. When I was getting married, my Russian wife needed to set up a bank account in the UK. Unsurprisingly. Off to Royal Bank of Scotland, who took the detailes, examined the marriage certificate, passport, visa, NI card ... filled in forms. And then sent her chequebook and bank cards to her OLD address in Siberia.
Pathetic. That's "Royal Bank of Scotland", for anyone who missed it the first time round.
And how are England, Wales and Northern Ireland going to manage if, as seems entirely plausible, the people of Scotland vote for independence in the 2014 referendum?
FWIW, in the 30 years that I've been living in Scotland, I've never yet heard a Scots Nationalist give a coherent answer to the Shetland question. If it's good for Scotland to take control of the majority of the north Sea oil production and secede from the UK, then it is exactly as good for Shetland to secede from the newly independent Scotland, and take over half the (UK sector's) oil reserves with them. Maybe they'd join up with the Noggins - the two nations have always got on well.
I get a vote. I haven't decided which way to vote. I suspect the vote is going to be quite close.
(On a sideline ... if Scotland breaks up the UK, would the English and Welsh be stupid enough to stay entangled with the mess that it Northern Ireland? That's totally unrelated to this topic. But it's amusing to consider the apoplectic fits that raising the question would provoke in "Loyalists.")
Which is why, for decades, I've been proposing that where ever possible, nuclear waste should be stored in locations that would guarantee that the first people to die if it is mis-handled are the politicians in charge of it.
In Britain, that means a relatively shallow waste repository in the London Clay Formation, with the entrance through the House of Commons. In Paris, it's not so clear. You'd probably have to have the repository much deeper in the "Greensand" (equivalent ; I've not drilled in the Paris Basin ; did I say that I'm a geologist?) to be below the aquifers in the Chalk Group. Berlin ... sorry, I know nothing about it's regional geology. Ditto for Washington DC.
But the important principle is simple : politicians will only pay for proper maintenance of waste dumps if they will be the first to die. So, you arrange for the politicians to be the first to die. Painfully, if possible. In the words of the meerkat, "Simples!"
Wearing my geological hard-hat ... the idea is starting from as poor position. Shales are sedimentary rocks, deposited in water, so they formed at low temperature (a few tens of degrees centigrade, no higher). They'll have got hotter with burial, but that will have been heat coming in from elsewhere (a small contribution from local radiogenic heat, but even the "hottest" shales, 300+API, are only a few hundreds of ppm U+Th+K). So, to get best efficiency it would almost always be better to go to the source of that heat. You'd then get a higher temperature difference and thus higher possible efficiency.
Carnot covered this in the foundations of thermodynamics nearly 2 centuries ago and it's not wrong.
Getting a large enough volume of rock sufficiently finely fractured to release enough heat for long enough to amortise the energy cost of building the wells ... that's the problem. You need as high a rock temperature as possible (for efficiency, above) at as shallow a depth as possible (to reduce the investment of energy, materials etc in the well). As someone mentioned up-thread - this adds up to being in a volcanic region, for optimal geothermal energy production. Which doesn't mean that it won't work elsewhere, just that it won't be optimal.
While still wearing my geologist's hard hat, and packing my bags to go and work on a Norwegian oil well tomorrow afternoon, I don't give a shit about whether I'm working on an oil well, a gas well, a water/ mud/ CO2 injection well, or a geothermal well. They all need geological planning and on-site supervision for well safety and optimisation. Which is my pay cheque, thank you. Not that saying that is going to quiet the conspiracy nutcases.
... witness A.P.P., Palaeo.electronica .... to name just two that I've been reading this week.
Quite possibly, banned. If you are in a working environment where flammable or explosive atmospheres are present as a normal part of normal operations, or as a part of "foreseeable emergency" operations, then the normal situation is to have a gas-proof, purged (from a known-clean air supply under positive pressure) power control box which monitors several flammable gas monitors in the area under consideration. If the gas monitors detect non-trivial amounts of flammable gas in the purged zone, or in the supply of "clean" air to the purged zone, then the system shuts down the power. Immediately. Within one cycle of AC. No "if", no "but", no "maybe", no "can I finish this write". No polite prompt that "The system is going down for power down now" followed by a shrinking white dot. Power is off NOW.
Multiple people have died for getting that wrong. Hundreds of millions of dollars of equipment have been burned or sunk. Lawsuits have occurred. Which is why the sparkies take it seriously.
I no longer work in such areas routinely, but I spent 20 years using and maintaining such equipment, including those gas detectors. Shit, they can be pernickety, particularly the gas detectors, and particularly when they get dosed with seawater spray that comes through when the waves are hammering 20m up the side of the vessel.
One of the companies that I work with routinely issues all of it's field staff with specialised laptops suitable to this environment. The staff must use one of these machines to log into the company network (this is enforced by spyware root-kitted in on the installation image and locked behind password-protected hardware (the "unit" has routers that refuse network service to computers that aren't running the spyware). The wifi cards are removed (people at this company have died through violation of radio silence rules when handling explosives ; so that possibility is eliminated ; it's easier than going back to court to explain why someone else has died) and to maintain the immediate effectiveness of the power shutdown systems, the batteries are removed and the battery terminals are hot-glued over so that they can never be re-fitted. (I guess they haven't worked out a procedure to get around the CMOS backup batteries. But being soldered into a PCB, they're probably unlikely to spark themselves.)
"No UPS" is a perfectly acceptable, expectable industrial situation. I've worked under such circumstances for nearly 30 years.
The legislative framework in which my work environment developed was derived from electrical equipment in coal mines, and the bodies that certify equipment designs were founded in the 1930s. Flammable atmospheres and electrical equipment are not a new combination, and lots of solutions have been tried. The rarity of such explosions is a testimony to the industry having stopped (mostly) arguing about the costs of this approach. Occasionally someone tries to cut corners - through ignorance or cost-cutting. I'd bet ... TWO ... pints of beer that the 29 bodies in the Pike River mine died due to short-cutting something in this regulatory regime. Though I now see that the final report has been released and prosecutions have occurred, so I suppose I've got some reading to do (my suppositions are reasonable. See item one of this list from the report on the homicides : "It is not possible to be definitive, but potential ignition sources include arcing in the mine electrical system, a diesel engine overheating, contraband taken into the mine, electric motors in the non-restricted part of the mine and frictional sparking caused by work activities."). Not a problem I have to work with in detail any more - my job is (partly) to avoid generating those flammable atmospheres in the first case (which clearly wasn't done
Lead-containing silicate glasses are relatively reactive, chemically. Don't do it - send them for proper disposal. If nothing else, within a short time (years to decades at most), a dry-stored landfill of CRT tubes, broken or not, is going to be worth smelting. To reclaim the lead.
No network content (because no network connection) ; no way for billing to occur ; no problem. I've never paid for an add-on in any game, ever. Is it common?
Where?
I've been looking for some nice amber to make a present for Mum's 75th. I did her a pendant in jet for her 70th.