The shuttle wasn't intended to be an experiment. It was intended to be a working vehicle. Its goal was to reduce the cost of launching to orbit. It was on this basis that the shuttle was funded in the first place.
It utterly failed to achieve this goal. In doing so, it blocked the continued development of expendable launchers in the US that very likely would have reduced launch costs (as they did in Europe and USSR/Russia.) We are considerably worse off today in space because of the shuttle.
As for the ISS not existing: that would be a huge benefit! The only significant achievement of the ISS is to make the shuttle program look good in comparison. Something like ISS only makes sense if you have a workable, economic launch system, which the shuttle never was. ISS was based on the lie that the shuttle wasn't failing, and, like anything based on a lie, became a fiasco.
JIMO is gone for excellent reasons. The nuclear propulsion technology sucked (completely pathetic thrust/mass ratio, so the mission would take far longer that it really should have), the mission was very expensive (and that expense was growing), and the relevance to the new goals at NASA was tenuous at best.
Freeman Dyson commented that JIMO would set nuclear propulsion technology back a generation. I'm sure he's glad to see it gone.
What's more, the scheme of 'accelerating deuterons and slamming them into a target' is only, what, more than six decades old?
Hell, Scientific American had an Amateur Scienstist column on building your own neutron generator using a van deGraaf generator to accelerate deuterons down a glass vacuum tube.
You don't see scientists getting excited about it because it cannot, even in principle, lead to net energy gain.
Can you cleanly separate the internals of the system from the external interfaces? That way, interaction with the internals can be scripted without having to watch GUIs or blinking lights. You do have to test the part that drives the GUI/etc., but that is presumably easier than having to do all the system tests through it.
IIRC, the SRB with the burnthrough later exploded by itself (after the stack had broken up, but before the range safety destruct signal could be sent.) If that's the case, having the hole on the other side would just have delayed destruction of the stack by less than a minute,
Efficiency is not a showstopper. Even a very inefficient 'electric' car still can beat a gasoline engine in marginal cost per mile.
Where electric cars (including those that store energy in compressed air) have problems is energy density. The compressed air car could do a bit better there if it also had a resistively heated thermal mass to heat the air before expansion. The thermal mass would be recharged from the wallplug at the same time the air tanks are refilled. Low atomic number materials can store a great deal of thermal energy; LiH heated to a vapor pressure of 1 bar, for example, stores several megajoules per kilogram.
Of course you're supposed to test huge chunks of software all at once. There are interaction bugs that come up only when you do that.
What you are trying to say, I think, is that that isn't the only kind of testing you should do, particularly to the exclusion of unit testing. That's a special case of a more general statement: you should do many different kinds of testing, because different strategies find different kinds of bugs, and the combination is often more powerful than any one approach.
I'm a great fan of randomized testing, and have used it to good effect in testing Common Lisp compilers as part of the GNU CL ANSI test suite. The oracle problem is tractable, since one can do differential testing -- test that two different computations that should produce the same answer actually do. For example, construct a random lisp form, then eval it, and also wrap it in a lambda form, then compile and funcall. Differences in output, errors during compilation, or errors during execution all indicate bugs (assuming one has generated legal lisp code.)
This and other more focused random testing schemes have found oodles of bugs in many Common Lisp implementations.
No, it is *you* who are patently incorrect. CO2 is *not* being absorbed geologically (aside from dissolution into the ocean) at a significant rate. Think, please -- if CO2 were really being so readily absorbed it wouldn't have been present in the atmosphere in the first place at anywhere close to current concentrations. That it was present is a reflection of the saturation of surface reservoirs.
You are also thinking very muddily about the effect of water vapor. Injection of a unit of CO2 that persists for centuries will have a much greater integrated effect than a local injection of water vapor that lasts for a few hours or days.
The point remains that water of combustion, released into the atmosphere, precipitates out within days. It is not a long term problem.
CO2 released by combustion, on the other hand, causes a sustained increase in atmosphereic CO2 that will take centuries to revert. And, no, it is not the case that 'CO2 is also absorbed into numerous geologic features beyond the ocean', to any significant extent on a time scale of less than millenia.
Humans *have* affected the water vapor content of the atmosphere, though. Plants transpire enormous amounts of it, and any time we alter plant cover we're modifying this input. The water produced by combustion will be, by comparison, a very small perturbation.
I've mentioned Fischer-Tropsch diesel in some other messages. It can be made from gasified biomass, organic waste, natural gas (just converting the NG being flared in remote sites, so-called 'stranded gas', would add 4 million barrel/day to world liquid fuel production), coal, or other unoxidized carbon sources.
Fischer-Tropsch diesel made using natural gas has a sulfur concentration of less than 1 ppm, a cetane rating of 74, and causes marked reductions in CO, particulate, hydrocarbon, and NOx emissions. The low sulfur makes NOx-destroying exhaust gas catalysts more practical. For these reasons CARB is already pushing for use of the stuff. FT from other feedstocks would require more scrubbing of sulfur from the syngas (the CO + H2 mixture that is reacted to make the liquid fuel), but that is well established technology.
There's this notion going around that hydrogen-fueled cars will increase global warming because they put water vapor into the atmosphere.
Simply put, this is nonsense. The concentration of water vapor in the atmosphere is controlled by evaporation and precipitation, not by injection of new water into the biosphere from combustion. In this is it completely unlike CO2, which has no comparably large surface reservoir (CO2 does dissolve in the ocean, but only the surface layers are in close contact with the atmosphere, and they cannot soak up all the CO2 being added.)
The thickness of radiation shielding for a reactor is a function of physics, not vehicle size. In a sub or ship, the vehicle is large enough that the crew can be shielded from the radiation. In a car, the driver (and bystanders) could not be.
Maybe if everyone drove a Canyonero the size of a large house it could be possible.
The way India and China are going to reduce oil demand is by increasing synfuel production. China has lots of coal, and is building large synfuel plants to convert it to liquid fuels.
The CO2 emissions are even worse than with oil, but it's a lot cheaper than hydrogen-from-moonbeams.
In any compressed gas, there are two effects going on. First, some molecules are close together and are weakly (and temporarily) bound. This reduces the stored energy in the system. The lower the temperature, the larger the fraction of molecules like this (and, eventually, the gas liquefies).
On the other hand, some molecules, at any instant, are in the process of violently colliding. They are briefly in a state of close approach where some of their kinetic energy has been converted to positive potential energy. At a given density, the higher the temperature, the larger the fraction of molecules that are in this second condition. This adds stored energy to the system.
For any gas, as you increase the temperature, the second effect eventually overcomes the first, and the gas has positive stored energy due to intermolecular interactions. This temperature is called the Joule inversion temperature. Hydrogen is one of the few gases for which this temperature is below room temperature.
An even better idea is Fischer-Tropsch diesel with the synthesis gas coming from gasified biomass. This uses all the energy in the plant -- cellulose, hemicellulose, lignin, everything -- not just starches or oils produced in seeds. You can even extend it by providing the steam for gasification using nuclear energy (instead of by burning some of the biomass).
An overwhelming fraction of the hydrogen made in the US each year is not made by electrolysis. Electrolysis is grossly noncompetitive at current electricity prices. Instead, hydrogen is made thermochemically from natural gas or other carbonaceous fuels (coal, biomass, petroleum coke, etc.)
Compressed hydrogen has only a fraction of the energy density of compressed natural gas, so the range would be even worse (if burned in an internal combustion engine). Even with fuel cells, the range would be bad -- and fuel cells are still many times too expensive to be practical.
This is not part of a 'chicken and egg' situation. Lack of fueling stations is not what's holding back hydrogen cars. What's holding them back is: (1) lack of range (due to the low energy density of compressed hydrogen gas, and lack of practical alternatives), (2) cost of hydrogen itself, and (3) the still very high cost of fuel cells. The last point is important, since hydrogen as a fuel makes very little sense for internal combustion engines -- since the hydrogen is made from natural gas, you might as well just burn natural gas in the vehicle, or a liquid fuel derived from gas.
BTW, if it's oil independence you want, Fischer-Tropsch diesel fuel is already very competitive at today's oil price (it would be competitive with oil at $25/barrel.) Expect many more synfuel plants to be built if oil stays expensive.
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The shuttle wasn't intended to be an experiment. It was intended to be a working vehicle. Its goal was to reduce the cost of launching to orbit. It was on this basis that the shuttle was funded in the first place.
It utterly failed to achieve this goal. In doing so, it blocked the continued development of expendable launchers in the US that very likely would have reduced launch costs (as they did in Europe and USSR/Russia.) We are considerably worse off today in space because of the shuttle.
As for the ISS not existing: that would be a huge benefit! The only significant achievement of the ISS is to make the shuttle program look good in comparison. Something like ISS only makes sense if you have a workable, economic launch system, which the shuttle never was. ISS was based on the lie that the shuttle wasn't failing, and, like anything based on a lie, became a fiasco.
JIMO is gone for excellent reasons. The nuclear propulsion technology sucked (completely pathetic thrust/mass ratio, so the mission would take far longer that it really should have), the mission was very expensive (and that expense was growing), and the relevance to the new goals at NASA was tenuous at best.
Freeman Dyson commented that JIMO would set nuclear propulsion technology back a generation. I'm sure he's glad to see it gone.
Arms are far from a minor platform. How many cell phones do you think are sold every year?
What's more, the scheme of 'accelerating deuterons and slamming them into a target' is only, what, more than six decades old?
Hell, Scientific American had an Amateur Scienstist column on building your own neutron generator using a van deGraaf generator to accelerate deuterons down a glass vacuum tube.
You don't see scientists getting excited about it because it cannot, even in principle, lead to net energy gain.
Can you cleanly separate the internals of the system from the external interfaces? That way, interaction with the internals can be scripted without having to watch GUIs or blinking lights. You do have to test the part that drives the GUI/etc., but that is presumably easier than having to do all the system tests through it.
IIRC, the SRB with the burnthrough later exploded by itself (after the stack had broken up, but before the range safety destruct signal could be sent.) If that's the case, having the hole on the other side would just have delayed destruction of the stack by less than a minute,
After hitting the water at 200 mph, I doubt anyone drowned.
It doesn't, but clearly a hydrogen zealot doesn't want hydrogen to have an 'explodes if you look at it funny' reputation.
Actually, the notion that the Hindenburg was doomed by its skin appears to be crank theory that fooled a lot of people.
Efficiency is not a showstopper. Even a very inefficient 'electric' car still can beat a gasoline engine in marginal cost per mile.
Where electric cars (including those that store energy in compressed air) have problems is energy density. The compressed air car could do a bit better there if it also had a resistively heated thermal mass to heat the air before expansion. The thermal mass would be recharged from the wallplug at the same time the air tanks are refilled. Low atomic number materials can store a great deal of thermal energy; LiH heated to a vapor pressure of 1 bar, for example, stores several megajoules per kilogram.
Of course you're supposed to test huge chunks of software all at once. There are interaction bugs that come up only when you do that.
What you are trying to say, I think, is that that isn't the only kind of testing you should do, particularly to the exclusion of unit testing. That's a special case of a more general statement: you should do many different kinds of testing, because different strategies find different kinds of bugs, and the combination is often more powerful than any one approach.
I'm a great fan of randomized testing, and have used it to good effect in testing Common Lisp compilers as part of the GNU CL ANSI test suite. The oracle problem is tractable, since one can do differential testing -- test that two different computations that should produce the same answer actually do. For example, construct a random lisp form, then eval it, and also wrap it in a lambda form, then compile and funcall. Differences in output, errors during compilation, or errors during execution all indicate bugs (assuming one has generated legal lisp code.)
This and other more focused random testing schemes have found oodles of bugs in many Common Lisp implementations.
That's 45 meters deep, not kilometers.
No, it is *you* who are patently incorrect. CO2 is *not* being absorbed geologically (aside from dissolution into the ocean) at a significant rate. Think, please -- if CO2 were really being so readily absorbed it wouldn't have been present in the atmosphere in the first place at anywhere close to current concentrations. That it was present is a reflection of the saturation of surface reservoirs.
You are also thinking very muddily about the effect of water vapor. Injection of a unit of CO2 that persists for centuries will have a much greater integrated effect than a local injection of water vapor that lasts for a few hours or days.
The point remains that water of combustion, released into the atmosphere, precipitates out within days. It is not a long term problem.
CO2 released by combustion, on the other hand, causes a sustained increase in atmosphereic CO2 that will take centuries to revert. And, no, it is not the case that 'CO2 is also absorbed into numerous geologic features beyond the ocean', to any significant extent on a time scale of less than millenia.
Humans *have* affected the water vapor content of the atmosphere, though. Plants transpire enormous amounts of it, and any time we alter plant cover we're modifying this input. The water produced by combustion will be, by comparison, a very small perturbation.
I've mentioned Fischer-Tropsch diesel in some other messages. It can be made from gasified biomass, organic waste, natural gas (just converting the NG being flared in remote sites, so-called 'stranded gas', would add 4 million barrel/day to world liquid fuel production), coal, or other unoxidized carbon sources.
Fischer-Tropsch diesel made using natural gas has a sulfur concentration of less than 1 ppm, a cetane rating of 74, and causes marked reductions in CO, particulate, hydrocarbon, and NOx emissions. The low sulfur makes NOx-destroying exhaust gas catalysts more practical. For these reasons CARB is already pushing for use of the stuff. FT from other feedstocks would require more scrubbing of sulfur from the syngas (the CO + H2 mixture that is reacted to make the liquid fuel), but that is well established technology.
There's this notion going around that hydrogen-fueled cars will increase global warming because they put water vapor into the atmosphere.
Simply put, this is nonsense. The concentration of water vapor in the atmosphere is controlled by evaporation and precipitation, not by injection of new water into the biosphere from combustion. In this is it completely unlike CO2, which has no comparably large surface reservoir (CO2 does dissolve in the ocean, but only the surface layers are in close contact with the atmosphere, and they cannot soak up all the CO2 being added.)
The thickness of radiation shielding for a reactor is a function of physics, not vehicle size. In a sub or ship, the vehicle is large enough that the crew can be shielded from the radiation. In a car, the driver (and bystanders) could not be.
Maybe if everyone drove a Canyonero the size of a large house it could be possible.
The way India and China are going to reduce oil demand is by increasing synfuel production. China has lots of coal, and is building large synfuel plants to convert it to liquid fuels.
The CO2 emissions are even worse than with oil, but it's a lot cheaper than hydrogen-from-moonbeams.
If you had the electricity to do that, you'd be better off just running the car's (electric) motors with it. Why bother with the hydrogen at all?
The problem is where do you get that electricity. Extension cord?
In any compressed gas, there are two effects going on. First, some molecules are close together and are weakly (and temporarily) bound. This reduces the stored energy in the system. The lower the temperature, the larger the fraction of molecules like this (and, eventually, the gas liquefies).
On the other hand, some molecules, at any instant, are in the process of violently colliding. They are briefly in a state of close approach where some of their kinetic energy has been converted to positive potential energy. At a given density, the higher the temperature, the larger the fraction of molecules that are in this second condition. This adds stored energy to the system.
For any gas, as you increase the temperature, the second effect eventually overcomes the first, and the gas has positive stored energy due to intermolecular interactions. This temperature is called the Joule inversion temperature. Hydrogen is one of the few gases for which this temperature is below room temperature.
An even better idea is Fischer-Tropsch diesel with the synthesis gas coming from gasified biomass. This uses all the energy in the plant -- cellulose, hemicellulose, lignin, everything -- not just starches or oils produced in seeds. You can even extend it by providing the steam for gasification using nuclear energy (instead of by burning some of the biomass).
An overwhelming fraction of the hydrogen made in the US each year is not made by electrolysis. Electrolysis is grossly noncompetitive at current electricity prices. Instead, hydrogen is made thermochemically from natural gas or other carbonaceous fuels (coal, biomass, petroleum coke, etc.)
Compressed hydrogen has only a fraction of the energy density of compressed natural gas, so the range would be even worse (if burned in an internal combustion engine). Even with fuel cells, the range would be bad -- and fuel cells are still many times too expensive to be practical.
This is not part of a 'chicken and egg' situation. Lack of fueling stations is not what's holding back hydrogen cars. What's holding them back is: (1) lack of range (due to the low energy density of compressed hydrogen gas, and lack of practical alternatives), (2) cost of hydrogen itself, and (3) the still very high cost of fuel cells. The last point is important, since hydrogen as a fuel makes very little sense for internal combustion engines -- since the hydrogen is made from natural gas, you might as well just burn natural gas in the vehicle, or a liquid fuel derived from gas.
BTW, if it's oil independence you want, Fischer-Tropsch diesel fuel is already very competitive at today's oil price (it would be competitive with oil at $25/barrel.) Expect many more synfuel plants to be built if oil stays expensive.