The significance may be that the neutron spectrometer is working.;)
Really, the significance depends on who you're talking to. To the geochemists, I'll bet it means that there are probably mineral formations being made by percolation of soda-water through rocks (place a CO2 glacier on top of an H2O glacier and you'll get things dissolving into each other near the bottom where the pressures get up there). To the xenobiologists, it means that they've got a place to look for life. To the planetary scientists, they've got something against which to test their models of atmospheric/hydrospheric formation and evolution. To the Mars Society, it's a guarantee of the raw materials for rocket fuel, agriculture and an eventual technological society on the Red Planet.
If you locate them in airports, what about people who work in the airport and have long term exposure?
Metal roofs, reflective glass (we've already got that on most office buildings which is why it's nearly impossible to use your radio very far inside), place all parking beneath parts of the power receivers. People who have to work on the ramp or runways could use protective clothing; an aluminized-mylar poncho (solid or fine mesh) and a wide-brimmed hat with a layer of the same in it would do the job.
A whale of a lot better than average sunlight
on
Lunar Lasers
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· Score: 2
So you'd need a close to 100% efficiency for a rectenna just to break even with photovoltaic cells (from a surface standpoint).
Average != peak. The rectenna is going to crank out a lot more juice under conditions of cloud and fog, and infinitely more at night.
Nobody's gotten this right yet
on
Lunar Lasers
·
· Score: 4, Informative
1. How will they focus the beam on receptor antenas?
There are some pretty simple ways of doing this. One is to send a "pilot beam" from the receiver to the transmitter, and use it as a phase reference. Using techniques of phase reversal (see this guy's bio) you can create a coherent beam at the other end of a "lumpy" medium like wavy glass (or the ionosphere, or a chicken [see the bio]).
2. How will they keep airplanes from flying across the beams?
They won't; the beam intensity isn't sufficient to be a problem. It just struck me that it would be ideal to locate airports in the middle of the receiver farms, because that will keep development from encroaching under the approach and departure paths and creating noise problems and threats to persons on the ground from crashes.
The only way for this not to harm you would be for it not to strike you. Early radar technicians learned about microwave cooking standing in front of such beams
There are easy ways to avoid it striking you (a wide-brimmed tinfoil hat might actually have usefulness against something in the real world). The best is to make sure it can't go anywhere other than where it's intended, using a technique like an encoded pilot beam. Turn off the pilot beam, the transmitter no longer has a phase reference, the various transmitter sections go incoherent, the power gets radiated all over the sky and falls to minuscule levels on Earth.
The efficiency doesn't include conversion TO microwaves (which you have to do anyway). Besides, long-distance transmission via microwave would require an infrastructure of orbital reflectors, which would be expensive to develop and have significant uncertainties. You can imagine how eager utility companies are to do this, when the costs of right-of-way and wire and towers are well-understood and easy to explain to stockholders and auditors.
Power doesn't just "dissipate". It can be part of a divergent beam, which just gets bigger and bigger, it can be absorbed (converted into e.g. heat) or it can be scattered. In the vacuum of space there is almost nothing to absorb or scatter significant amounts of such a beam, so we're left with divergence. You can keep divergence of a coherent beam to an arbitrarily small amount by making your transmitting antenna larger.
As for building sats in geosync, I agree with you except for the issue of light pollution (but the relay sats required to send power to the half of the earth invisible from the Moon would present the same problem). The real problem is where you get the raw materials for the plants regardless of where they're located. Using near-earth asteroids instead of the moon may be easier and cheaper, avoiding the difficulty of having to work in gravity, at a couple of miles/second delta-V from an earth-return trajectory, and all those other issues. Lunar chauvinism shouldn't blind us to taking the most cost-effective route to the goal.
Catching them is a lot simpler than that
on
Lunar Lasers
·
· Score: 3, Insightful
No, they don't boil water and spin turbines. What you do is to take the microwaves, catch them with an antenna (they are radio, after all) and rectify them with a diode (what you get is just very, very high-frequency alternating current which can be converted to DC with that most simple of all semiconductor devices).
Before you go "Bah", please understand that this has actually been tested over an atmospheric path crossing as much air as you'd need to from a typical orbit, and efficiencies around 80% were measured.
Adding satellite radio to the trucks would make them more expensive and drive up the upkeep. Why should a rental agency spend the money when it's obvious that people will pay to rent a truck with a broken radio? Budget, Ryder and U-Haul will spend money to keep their losses down and revenue up, so they'll do things like tracking their vehicles by satellite so they can schedule better. Satellite radio is a non-starter for them.
Montana: 882,779
N. Dakota: 633,666
S. Dakota: 733,133
Wyoming: 479,602
Total: 2,728,180
The total population of those four states is about what one of those services needs as a subscriber base to break even. You'd need an awfully high subscription rate to make much of your money there.
ask anyone who has driven across Montana, Wyoming, and one or both of the Dakotas: There are literally miles and miles where you cannot get any radio at all.
Those are also areas where people are also spread very thinly. You're not going to pay for your satellite network with 15% of those people; you're going to need 3% of the suburban drivers. U-Hauls are the same, people don't use them often enough to make it worth putting a sat radio in it. Those things usually don't even have cassette decks, let alone CD players. (Yes, I have way too much experience with rental trucks.)
Long-haul truckers are probably a solid market, but I don't know how many of them there are or if they'd make a big difference in the bottom line.
I normally ignore people who are [stupid|ignorant|trollish] enough to get their karma that far into negative territory, but...
If the greenhouse effect from all the original CO2 had been good enough to keep the planet warm it would never have frozen in the first place.
Wrong. To be effective as a greenhouse agent, the CO2 has to be in the atmosphere. Weathering of rocks removes CO2 from the atmosphere and turns it into carbonates; to get back into the atmosphere it has to be recycled by volcanic activity. When Mars (which is a planet much smaller and lighter than Earth) cooled off, its tectonic processes stopped, there was not enough vulcanism to keep pace with weathering, and the atmosphere dwindled to the point where it froze. Or so goes the scenario.
A) it wasn't good enough and no matter how much of the trapped CO2 you release it won't warm mars much
Or it only needs a kick of maybe ten degrees worth of warming, and then the same feedback loop which led to the iceball catastrophe will do the rest.
B) More likely the atmosphere has been eroded over the billenia by the solar wind and it has literally blown away and there is very little frozen CO2 to liberate in the soil.
(You mean "æons"; "billenia" isn't a word.) We know that the ephemeral Martian icecaps are CO2 snow, and from basic chemical work we know how much CO2 can be adsorbed on various minerals. There's definitely a lot of CO2 there, the question is how much and how much the temperature has to rise to liberate it.
Mars has its own cycle of precession of its rotational axis, and it's known that a long period of summer in a hemisphere tends to cut down on the amount of ice there. If the period of Mars' aphelion (where it is moving most slowly in it orbit, and thus spending the most time) now coincides with southern-hemisphere summer, you'd expect the CO2 icecap to be shrinking. Note that this would mean nothing whatsoever with respect to conditions on Earth.
Photodissociation of water may have released a lot of Martian hydrogen to leak away (the very high proportion of deuterium in Martian water compared to Earth's strongly argues for this), but the oxygen and whatnot are too heavy for much to escape that way. The only place for them to have gone is down.
This means that the oxygen, nitrogen and carbon are probably in the soil. This would explain why Mars is so red (all that oxidized iron) and why the atmosphere is so rarefied (most of the gases are tied up as permafrost, adsorbed gas or chemical compounds like nitrates). It also means that the right kind of change can release them and make them into a thick atmosphere again.
Bob Zubrin of the Mars Society has written that we could start what would probably be a substantial greenhouse effect on Mars with only a few million tons of greenhouse gases (such as sulfur hexafluoride and methane) per year. This is the output of one large-scale industrial plant. Once you start heating the soil the adsorbed gases come out and the permafrost melts, leading to more warming and more gas release. Once you've got 200 millibars of atmosphere you can walk around outside with nothing fancier than a heavy parka and an oxygen mask. That's not bad for a planet that's currently an iceball with 7 millibars of fire-extinguisher contents for "air".
From what I understand, we still don't fully understand how flapping wings fully work. Until recently, calculations on the lift provided by bees wings showed that they should crash and burn.
No, what the calculations indicated was that bees could not glide. Which they can't, and don't. Until CFD work was sufficiently advanced it wasn't well-understood how they did fly (the behavior of fluids at low Reynolds numbers wasn't that easy to analyze), but nobody seriously wrote "Bees shouldn't be able to fly".
There's a full analysis of this folktale on the web somewhere, but I'm at work and don't have time to go looking for it to post a cite.
What I was thinking was not of straight exhaust.. but of somehow mining the catalytic converter.
You'd all but certainly want to put the unit downstream of the cat regardless, because you need a certain exhaust-gas temperature to get the cat to "light off" in the first place and you don't want to chill it. However, I doubt that you're going to get a great deal of energy from the cat itself; the cat can only grab energy from unburned fuel, and the engine does a pretty good job of that already (with modern controls).
You'd probably have your biggest "win" by coming up with a way to manage the temperature of the gas going into the cat. If you could come up with a thermostat to switch the heat flow from the header pipe to an "upstream" thermoelectric converter such that the system was only "on" when the gas was getting too hot for the cat (and the pipe was insulated when it was cold), and use a "downstream" thermoelectric converter to make use of all the heat coming out of the cat, you'd be making the best of it.
I saw a patent for an idea which might interest you. Someone had the idea of putting a heat exchanger in the exhaust pipe to rapidly heat engine coolant (this would have to be "downstream", of course). When the engine was warm a valve would open and bypass the heat exchanger. The heat exchanger could be somewhat restrictive, which would increase exhaust back-pressure and exhaust-gas temperature with it. This would make the catalytic converter light off faster and reduce pollution. Not bad for people who live in places where it gets cold, huh?
Consider the open flame of a gas range literally belching heat, much of which escapes into the air or is absorbed by the metal around it. What if the oven and catch-plates below each burner were lined with a hard-coated version of the device?
If the furnace has a pilot flame, it already has one. There is a little thermocouple element heated by the pilot; this generates enough current to hold a solenoid valve open. This valve allows gas to flow to the pilot flame. If the flame goes out, the thermocouple cools and the gas valve closes. Modern furnaces use electronic ignition and eliminate the pilot flame and all its waste.
Quite nearly every home contains dozens of devices that let off lots of energy while in use. Think of your oven, dryer, toaster, refrigerator, furnace... dare I say woodstove?!? Lining these heat-driven devices with such a product could prove valuable.
Water heater, furnace, woodstove - yes. Oven, toaster, refrigerator - almost certainly not; ovens and toasters would be better improved by increasing insulation, and the grease and other crud in the outflow of an oven would probably clog your generator's collector fins. The refrigerator's efficiency will be cut by anything which increases the condenser temperature; you don't want to try generating electricity from that (but preheating your domestic hot water supply, which is generally cold, would improve matters). Dryer, maybe; it depends on how high a temperature you need at the drum, but being able to scavenge 5-10% of the flame's heat and turn it into juice might let you run the motor and maybe the washing machine too.
In older homes where radiators are the norm, this might even provide an economical way to prevent burns from leaning up against those pesky pipes!!!
Wrong end. Where you'd want to put the thermopiles is between the flame and the water in the boiler; that would give you a nice temperature drop between ~400 C on the hot side and ~100 C on the cold side. You wouldn't get enough T between steam and the room air to make it useful; you might as well just put a grille over the pipe so you can't put skin on it.
And then the stories are legion about prime fisheries being destroyed by warmer water-pacific anchovies, for instance.
That's because the cold-water fisheries are cold because they are fed nutrients by upwelling of nutrient-rich deep (and cold) water. If that upwelling is choked off by warm, nutrient-depleted water, the fishery collapses. It's not the temperature, it's the nutrient content of the water; if you used an ocean-thermal system to bring up deep, nutrient-rich water and warm it, you'd still have things growing in it like mad.
Car engines are fairly temperature-sensitive, and generally are most efficient at about 150 Farenheit. They also crap out if they get too hot-usually around 250-270 Farenheit
That's because ethylene glycol coolants are boiling at the hotspots, reducing heat-transfer efficiency and exacerbating the problem. If you use a coolant with more "headroom", such as propylene glycol or oil, you can run at higher coolant temperatures.
Also, the electrical system is dependent on staying fairly close to 12VDC. Too much or too little can screw up computers.
Not so, even today. The computer generally runs on a linear regulator and, aside from overheating the chip, it couldn't care less what the system voltage is as long as it's enough to get 5 volts at the Vcc pin. The typical specs I see call for modules to work up to 16 volts or more, and down to 8 or 9.
Even less so in the future, because vehicle designers are moving to 42-volt electrical systems so they can get rid of belt drives and use electric instead for things like the air conditioning, power steering and even ride control motors. Of course, the computers will be using switched power supplies by then.
It's true, the applications for automobiles seem rather limited, but thermionics could stand to revolutionize the nature of power plants....
Thermionics, as I understand it, eliminates the "middleman" of the equation by translating heat directly to electricity. It certainly will be interesting to see how this develops on a commerical and thus much larger scale.
You are mistaking mechanical simplicity with thermodynamic efficiency. There is no relationship between them. The most efficient powerplants these days are combined-cycle gas turbine powerplants, which burn fuel in a gas turbine and obtain some power at the turbine shaft, then run the turbine exhaust gases into a boiler where the heat makes steam to run a steam turbine. The total efficiency of one of these plants can exceed 60%. Notice that these are not simple devices.
In contrast, the only thermoelectric generator I know you can buy is for running a little fan which goes on the top of your wood stove. The efficiency of these things is very low, and they are only used where mechanical simplicity is an overriding requirement (such as the power supplies on deep-space probes, which are heated by radioisotope sources). If MIT has come up with a converter which is efficient enough to be worth carrying on a vehicle to scavenge energy from the exhaust heat, that's better than anything we've got today.
Actually it would increase the entropy, because every energy transformation increases the entropy in the universe...
No, it would decrease the entropy versus the default case, because part of the heat would be converted to work. Without the conversion all of the heat would be dumped into the atmosphere and diluted to uselessness; with the conversion, only the un-converted fraction is dumped. To the extent that the total fuel burned is reduced, the entropy increase is also reduced.
First your 100 HP engine will only produce 25-35 HP most of the time. Peak power is only produced during hard accerlation during cruse it's much lower and at iddle almost nonexistant.
Which doesn't make much difference, because the engine's waste-heat output doesn't change nearly as fast with throttle opening as the crankshaft output does. Even at idle (zero power) you are still burning fuel and still pumping heat out the exhaust pipe. If you can force that waste heat to do some work for you instead of just being diluted to uselessness in the atmosphere, you've accomplished something.
A hybrid vehicle would probably shut down the engine at idle and eliminate that waste-heat stream, so the thermal converter would be more useful as a way to increase the general efficiency level of the powertrain. If you can get an extra 10% off the 40% of the heat which is rejected through the exhaust, that's 4% of your fuel value; added to a 30% engine thermal efficiency, you've gained 13%. That's nothing to sneeze at.
The auto companies are changing over to 42-volt electrical systems and Integrated Starter-Generators (ISGs) to obtain the 5-7 KW that new vehicle systems will require, and also to obtain idle-shutdown capabilities to save fuel. The ISG would work beautifully in tandem with a thermionic heat engine driven by the exhaust heat, because the power from the thermionic generator could reduce the load on the ISG, reducing its power drain and thus vehicle fuel consumption. If the thermionic system could produce more electric power than required by the vehicle the excess power could be used to drive the ISG as a motor, helping to propel the vehicle. This is an example of a "bottoming-cycle engine", creating useful work out of the waste heat of another engine.
Somehow I think that a company which is using solid-fuel rockets (because they're reliable and rugged?) isn't going to spend the money to build a booster using exotic, corrosive mixtures which also present a toxic hazard to both flight and ground crew. The Black Horse people claim a specific impulse of 330 seconds for H2O2/JP-5 (see Black Horse: One Stop to Orbit), which is considerably better than solids too and all but certainly far cheaper to develop than an exotic. The optimum for cheapness might be something as mundane as sub-cooled propane and LOX.
Buran didn't get it quite right, so I'm going to see if I can briefly but accurately sum up why this is an improvement.
When a rocket takes off from the ground, it is throwing away gas at many times the speed of sound while it's moving very slowly. If you calculate the amount of energy which actually accrues to the rocket versus what disappears as heat and noise with the exhaust gas, the efficiency is dismal. Launching from an aircraft allows the rocket to begin operating at a much higher efficiency; indeed, the air-launched rocket starts at a speed and altitude that the ground-launched rocket may have to burn half of its mass to reach.
Nozzles cost about the same, but a nozzle with a bigger bell can expand the gases more and get more thrust out of them. More thrust for the same fuel means more payload to orbit, and costs go down. You can't use a large-bell nozzle on a launch from the ground because the gases would be over-expanded, separate from the nozzle walls and cost you badly in efficiency and thrust. This means that the rocket launching from high altitude has an advantage which goes well beyond starting a bit higher.
The payload at the end of a rocket burn is an exponential function of the delta-V (the more speed you have to put on, the more of your vehicle has to be fuel and the less is payload); getting a 550-600 MPH or so head-start helps a lot. So does the aerodynamic lift of the wing, which is effectively "vertical thrust" that comes for a fraction of the fuel required to produce the same with rocket fuel.
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Really, the significance depends on who you're talking to. To the geochemists, I'll bet it means that there are probably mineral formations being made by percolation of soda-water through rocks (place a CO2 glacier on top of an H2O glacier and you'll get things dissolving into each other near the bottom where the pressures get up there). To the xenobiologists, it means that they've got a place to look for life. To the planetary scientists, they've got something against which to test their models of atmospheric/hydrospheric formation and evolution. To the Mars Society, it's a guarantee of the raw materials for rocket fuel, agriculture and an eventual technological society on the Red Planet.
The efficiency doesn't include conversion TO microwaves (which you have to do anyway). Besides, long-distance transmission via microwave would require an infrastructure of orbital reflectors, which would be expensive to develop and have significant uncertainties. You can imagine how eager utility companies are to do this, when the costs of right-of-way and wire and towers are well-understood and easy to explain to stockholders and auditors.
Power doesn't just "dissipate". It can be part of a divergent beam, which just gets bigger and bigger, it can be absorbed (converted into e.g. heat) or it can be scattered. In the vacuum of space there is almost nothing to absorb or scatter significant amounts of such a beam, so we're left with divergence. You can keep divergence of a coherent beam to an arbitrarily small amount by making your transmitting antenna larger.
As for building sats in geosync, I agree with you except for the issue of light pollution (but the relay sats required to send power to the half of the earth invisible from the Moon would present the same problem). The real problem is where you get the raw materials for the plants regardless of where they're located. Using near-earth asteroids instead of the moon may be easier and cheaper, avoiding the difficulty of having to work in gravity, at a couple of miles/second delta-V from an earth-return trajectory, and all those other issues. Lunar chauvinism shouldn't blind us to taking the most cost-effective route to the goal.
Before you go "Bah", please understand that this has actually been tested over an atmospheric path crossing as much air as you'd need to from a typical orbit, and efficiencies around 80% were measured.
Adding satellite radio to the trucks would make them more expensive and drive up the upkeep. Why should a rental agency spend the money when it's obvious that people will pay to rent a truck with a broken radio? Budget, Ryder and U-Haul will spend money to keep their losses down and revenue up, so they'll do things like tracking their vehicles by satellite so they can schedule better. Satellite radio is a non-starter for them.
Montana: 882,779
N. Dakota: 633,666
S. Dakota: 733,133
Wyoming: 479,602
Total: 2,728,180
The total population of those four states is about what one of those services needs as a subscriber base to break even. You'd need an awfully high subscription rate to make much of your money there.
Long-haul truckers are probably a solid market, but I don't know how many of them there are or if they'd make a big difference in the bottom line.
Mars has its own cycle of precession of its rotational axis, and it's known that a long period of summer in a hemisphere tends to cut down on the amount of ice there. If the period of Mars' aphelion (where it is moving most slowly in it orbit, and thus spending the most time) now coincides with southern-hemisphere summer, you'd expect the CO2 icecap to be shrinking. Note that this would mean nothing whatsoever with respect to conditions on Earth.
This means that the oxygen, nitrogen and carbon are probably in the soil. This would explain why Mars is so red (all that oxidized iron) and why the atmosphere is so rarefied (most of the gases are tied up as permafrost, adsorbed gas or chemical compounds like nitrates). It also means that the right kind of change can release them and make them into a thick atmosphere again.
Bob Zubrin of the Mars Society has written that we could start what would probably be a substantial greenhouse effect on Mars with only a few million tons of greenhouse gases (such as sulfur hexafluoride and methane) per year. This is the output of one large-scale industrial plant. Once you start heating the soil the adsorbed gases come out and the permafrost melts, leading to more warming and more gas release. Once you've got 200 millibars of atmosphere you can walk around outside with nothing fancier than a heavy parka and an oxygen mask. That's not bad for a planet that's currently an iceball with 7 millibars of fire-extinguisher contents for "air".
Why do I have to have the kind of government they deserve?
There's a full analysis of this folktale on the web somewhere, but I'm at work and don't have time to go looking for it to post a cite.
You'd probably have your biggest "win" by coming up with a way to manage the temperature of the gas going into the cat. If you could come up with a thermostat to switch the heat flow from the header pipe to an "upstream" thermoelectric converter such that the system was only "on" when the gas was getting too hot for the cat (and the pipe was insulated when it was cold), and use a "downstream" thermoelectric converter to make use of all the heat coming out of the cat, you'd be making the best of it.
I saw a patent for an idea which might interest you. Someone had the idea of putting a heat exchanger in the exhaust pipe to rapidly heat engine coolant (this would have to be "downstream", of course). When the engine was warm a valve would open and bypass the heat exchanger. The heat exchanger could be somewhat restrictive, which would increase exhaust back-pressure and exhaust-gas temperature with it. This would make the catalytic converter light off faster and reduce pollution. Not bad for people who live in places where it gets cold, huh?
Even less so in the future, because vehicle designers are moving to 42-volt electrical systems so they can get rid of belt drives and use electric instead for things like the air conditioning, power steering and even ride control motors. Of course, the computers will be using switched power supplies by then.
In contrast, the only thermoelectric generator I know you can buy is for running a little fan which goes on the top of your wood stove. The efficiency of these things is very low, and they are only used where mechanical simplicity is an overriding requirement (such as the power supplies on deep-space probes, which are heated by radioisotope sources). If MIT has come up with a converter which is efficient enough to be worth carrying on a vehicle to scavenge energy from the exhaust heat, that's better than anything we've got today.
A hybrid vehicle would probably shut down the engine at idle and eliminate that waste-heat stream, so the thermal converter would be more useful as a way to increase the general efficiency level of the powertrain. If you can get an extra 10% off the 40% of the heat which is rejected through the exhaust, that's 4% of your fuel value; added to a 30% engine thermal efficiency, you've gained 13%. That's nothing to sneeze at.
How do I know? I am very close to the business.
Somehow I think that a company which is using solid-fuel rockets (because they're reliable and rugged?) isn't going to spend the money to build a booster using exotic, corrosive mixtures which also present a toxic hazard to both flight and ground crew. The Black Horse people claim a specific impulse of 330 seconds for H2O2/JP-5 (see Black Horse: One Stop to Orbit), which is considerably better than solids too and all but certainly far cheaper to develop than an exotic. The optimum for cheapness might be something as mundane as sub-cooled propane and LOX.
- When a rocket takes off from the ground, it is throwing away gas at many times the speed of sound while it's moving very slowly. If you calculate the amount of energy which actually accrues to the rocket versus what disappears as heat and noise with the exhaust gas, the efficiency is dismal. Launching from an aircraft allows the rocket to begin operating at a much higher efficiency; indeed, the air-launched rocket starts at a speed and altitude that the ground-launched rocket may have to burn half of its mass to reach.
- Nozzles cost about the same, but a nozzle with a bigger bell can expand the gases more and get more thrust out of them. More thrust for the same fuel means more payload to orbit, and costs go down. You can't use a large-bell nozzle on a launch from the ground because the gases would be over-expanded, separate from the nozzle walls and cost you badly in efficiency and thrust. This means that the rocket launching from high altitude has an advantage which goes well beyond starting a bit higher.
- The payload at the end of a rocket burn is an exponential function of the delta-V (the more speed you have to put on, the more of your vehicle has to be fuel and the less is payload); getting a 550-600 MPH or so head-start helps a lot. So does the aerodynamic lift of the wing, which is effectively "vertical thrust" that comes for a fraction of the fuel required to produce the same with rocket fuel.
Hope that helped.