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Interstellar Arrival: Slowing the Sail
by Paul Gilster on November 7, 2014
Some final thoughts on hybrid propulsion will wrap up this series on solar sails, which grew out of ideas I encountered in the new edition of the Matloff, Johnson and Vulpetti book Solar Sails: A Novel Approach to Interplanetary Travel (Copernicus, 2014). The chance to preview the book (publication is slated for later this month) took me in directions I hadn't anticipated. Solar Sails offers a broad popular treatment of all the sail categories and their history, as you'd expect, but this time through I focused on its four technical chapters on sail theory that helped me review the details.
And because I kept running into the idea of multiple modes of propulsion, my thoughts on avoiding doctrinaire solutions continue to grow. In fact, I'd venture to say that probing into the possibilities of multimodal propulsion may offer a serious opportunity for insights. Centauri Dreams regular Alex Tolley came up with one of these yesterday, asking whether a sail mission to Jupiter space might deploy the planet's huge magnetic field as an assist. Alex invokes Pekka Janhunen's ideas about electric sails. Let me quote from the Solar Sails book on what Janhunen has in mind:
Similar to the magsail, this concept uses the solar wind for producing thrust. However, different from the magsail, this sail interacts with the solar plasma via a mesh of long and thin tethers kept at high positive voltage by means of an onboard electron gun. In its baseline configuration, the spacecraft spins and the tethers are tensioned by centrifugal acceleration. It should be possible to control each wire voltage singly, at least to within certain limits.
We get thrust out of this when protons from the solar wind, positively charged, are repelled by the positive voltage of the spacecraft's tethers, while electrons are captured and ejected — otherwise, their growing numbers would neutralize the voltage in the tether mesh. But Alex also brings to mind Mason Peck's interesting work at Cornell on miniaturized 'Sprites,' tiny chip-like spacecraft that could use the Lorentz force to accelerate in directions perpendicular to the magnetic field. Remember that Jupiter's magnetic field is 18,000 times stronger than Earth's, a useful resource if we can tap it even so far as to adjust the orbits of planetary probes.
Alex's thoughts on the matter deserve to be quoted:
We often think of sail ships as clipper ships – i.e. using large surfaces to capture or direct the wind to move. But modern ships use screws. There have also been numerous wind turbine designs that offer advantages over canvas sails, even if they are not as aesthetic to the eye. (Clipper ships were possibly the most pleasing ship designs ever built). Might we be thinking too much in terms of sails that mimic the romance of traditional sails, rather than designs that might offer better performance, albeit with some aesthetic loss?
Interstellar Arrival
A sense of aesthetics produces pleasing designs but what looks best isn't always what we need. Back in my flying days some of us used to talk about (and in a few cases actually fly) some of the great aircraft designs of the 1930s and later, and although I never got my hands on the controls of one, a great favorite was the Beech Staggerwing, a gorgeous design with a negative wing stagger, meaning that the lower wing is farther forward than the upper. Designs like this could be sleek and lovely because of the medium they worked in. But spacecraft don't need wings and streamlined fuselages, and our Voyagers and Cassinis look nothing like the wilder designs of early science fiction because they don't need to, never encountering a planetary atmosphere.
Image: The Beech Model 17 Staggerwing, first produced in 1932. Credit: Wikimedia Commons.
A beamed lasersail on its way to Alpha Centauri may be anything but a thing of beauty. Once the mission enters its cruise phase, the sail can be safely stowed, and one good use for it would be to shroud the payload to offer additional protection against radiation. We're always trying to think of ways to get more value out of existing assets, which is what extended missions are all about. Or think about the Benfords' JPL work that revealed desorption. No one with an eye for design would come up with painting a desorption layer on a sailcraft, but it's conceivable that desorption, which is the release of CO2, hydrocarbons and hydrogen from within the manufactured sail as it heats up under the beam, could give an added kick to interplanetary sails being pushed by powerful microwave beams.
Mentioning Forward brings me back around to the 'staged sail' concept that he worked out for stopping at another star. The sail has three divisions, as shown in the diagram below, which is taken from his paper on a manned mission to Epsilon Eridani. 'Staging' the sail means losing first the outer ring, then the middle one, until only the inner ring is left. In sequence, the spacecraft slows down by using laser light beamed from our Solar System, reflected off the now separated outer sail as it approaches the star — the light is directed back at the two remaining sail segments with payload. Ingenious tinkering let Forward use the second sail detachment as the way the crew got home, with laser light boosting the much smaller inner sail by reflection from the middle segment.
Image: Robert Forward's staged sail concept. What he calls a 'paralens' in the diagram is an enormous Fresnel lens in the outer Solar System, made of concentric rings of lightweight, transparent material with free space between the rings. Credit: Robert Forward.
Staged sails are hard to see as anything but a longshot — the success of the mission depends not only upon perfect execution of the staging process but, crucially, upon the laser beam from Earth being able to illuminate the sail segments effectively. Forward was fully aware of the possibilities here, and you can find discussion in places like his novel Rocheworld (Baen, 1990) about how politics on Earth might affect the use of the expensive beam. I for one wouldn't want to put my life in the hands of a design like this, which depends so crucially upon decisions made far from the spacecraft.
Interestingly, like Mason Peck, Forward had some thoughts on how we might use the Lorentz force as well. Remember that a charged object moving through a magnetic field experiences this force at right angles to its direction of motion and the magnetic field itself. Out of this you get 'thrustless turning,' which both Forward and Philip Norem thought could be used for deceleration. Instead of staged sails, you get an electrostatically charged probe — think of Janhunen's electric sail tethers — on a trajectory that goes well beyond the target star. The spacecraft's interactions with the galactic magnetic field bend its trajectory so that it approaches the target from behind.
Once it's inbound to the destination system, a laser beam from Earth can be turned upon it to slow it down for arrival. The idea is anything but aesthetic, just as the Janhunen sail would look like something closer to a porcupine than the silvery lozenge of an early SF starship. It's also hampered by the fact that mission times, already measured in decades at minimum, are tripled with the use of this maneuver. I should mention that Solar Sails authors Gregory Matloff and Les Johnson have also explored the uses of electrodynamic tethers to supply power to an Alpha Centauri expedition, even if a Norem-style arrival seems too lengthy.
Creative thinking about these matters often springs from putting two or more solutions together to see what can happen. What I've always admired about the interstellar community is its ability to re-examine older concepts to look for interesting cross-pollination of ideas. As we move into the era of increasingly tiny components, it's heartening to think how many designs will be affected by new nanotechnological possibilities. Mason Peck has talked about using Jupiter's magnetic field to spew thousands of 'Sprites' out on interstellar trajectories. What else can we imagine as we look for extended uses of existing tech and ponder where they might lead us?
Forward's paper on staged sails is "Roundtrip Interstellar Travel Using Laser-Pushed Lightsails," Journal of Spacecraft and Rockets 21 (1984), pp. 187-195. The Norem paper is "Interstellar Travel: A Round Trip Propulsion System with Relativistic Capabilities," AAS 69-388 (June, 1969). Forward's paper on Lorentz force turning is "Zero-Thrust Velocity Vector Control for Interstellar Probes: Lorentz Force Navigation and Circling," AIAA Journal 2 (1964), pp. 885-889. Matloff and Johnson discuss electrodynamic tethers in "Applications of the Electrodynamic Tether to Interstellar Travel," JBIS 58 (June, 2005), pp. 398-402.
Alex Tolley November 7, 2014, 16:23
I think of a magsail as a magnetic parachute for decelerating. However, is it possible to reconfigure a sail to become a ramscoop instead, using the scoop's drag to advantage here, as well as the fusion rocket's thrust to decelerate? If so, then it might be worth examining the tradeoffs this hybrid system.
The engines needn't be fusion rockets either, just solid state ion spray engines using the charged stellar wind as the propellant, making this suitable for small cubesat class payloads as well as larger craft.
I don't think we need to a priori assume that resources in the target system cannot be utilized until the craft is nearly at rest, as is commonly envisioned. It might be possible to actively build elements of a deceleration device (e.g. electric sail) from scooped materials as the craft decelerates, thus increasing its performance at both ends of the journey, using the sparse material scooped up while decelerating from a small fractions of c (~1300 km/s for the 1000 years to alpha Centauri solar sail scenario).
Michael November 7, 2014, 17:26
@Alex Tolley November 7, 2014 at 16:23
'I think of a magsail as a magnetic parachute for decelerating. However, is it possible to reconfigure a sail to become a ramscoop instead, using the scoop's drag to advantage here, as well as the fusion rocket's thrust to decelerate? If so, then it might be worth examining the tradeoffs this hybrid system.'
If you collect the fuel you have two problems, one you increase the mass of the craft to slow down by collecting it and second the ignition of the engine will clear the fuel from in front of the craft. Unless the scoop collects the material and bends it almost 180 degrees so that the deflected fuel acts as a greater sized scoop funnelling the material in to be turned around.
Perhaps we could send out an adjustable beam of material first by particle beam, the craft will then intercept the material later on in the flight and use it to slow down.
@Michael "If you collect the fuel you have two problems, one you increase the mass of the craft to slow down by collecting it"
Only if you collect it. If you burn it off as it is collected, I don't think this should be a problem.
"second the ignition of the engine will clear the fuel from in front of the craft."
I would have thought the reverse – the scoop will try to collect the exhaust, making it useless for thrust. It may be totally impractical, or even theoretically silly. But yes, there are many issues, which is why I asked the question. It seems an obvious approach and therefore may have been addressed in the past, especially when the Bussard ram jet idea was shown likely be be unworkable, resulting in more drag than engine thrust.
ProjectStudio November 7, 2014, 22:25
"The spacecraft's interactions with the galactic magnetic field bend its trajectory so that it approaches the target from behind."
Astronomers are only recently getting a better idea of some of symmetries of the galactic magnetic field. I'll venture to open up the possibility, which would have been on the ragged fringe not long ago, to say that the properties of the galactic magnetic field, and the wide and regional co-existing currents that must be entwined with those fields, might well influence our choice of destination for a magnetic/electric hybrid probe.
http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_takes_magnetic_fingerprint_of_our_Galaxy
http://www.astronomy.com/news/2014/02/scientists-reveal-cosmic-roadmap-to-galactic-magnetic-field
Eniac November 8, 2014, 0:38
Lorentz turning is a fascinating subject. As ProjectStudio mentions, the galactic field is not homogeneous at all. Navigating it by Lorentz turning might be much like navigating balloons (or sailships, for that matter) on Earth: Indirect and using complex maneuvers.
'But spacecraft don't need wings and streamlined fuselages, and our Voyagers and Cassinis look nothing like the wilder designs of early science fiction because they don't need to, never encountering a planetary atmosphere.'
As we get faster and faster the particles that the craft will encounter will behave like an on coming wind, this will necessitate a streamlined craft of thin dimensions. Streamlined so that an impact will more likely be deflected to the side and thin to avoid collisions altogether. Very fast craft in the future may be designed more like a needle than a blunt nosed hammer.
Paul Gilster November 8, 2014, 12:46
Michael, as we get up into these speed ranges, we'll also be needing serious shielding against what impacts do occur. Lots to work on there as we conceive of spacecraft moving at even modest percentages of lightspeed.
Horatio Trobinson November 8, 2014, 12:48
Can anybody explain why the need to beam things from Earth with all the energy and warming problems we already have on its surface?
Wouldn't it be better to beam lasers from Titan where fuel doesn't even need to be extracted and there's no intelligent life (that we know of) to be harmed by our industry?
(Titan being just an interesting example, but it could be any spatially favourable point of the solar system that also has decent amounts of usable energy in some form)
Beaming from close solar orbit is what is envisioned here, allowing us to extract the huge energies we'll need to power up these futuristic laser arrays. This is what people like Forward were talking about, a space-based infrastructure that could sustain the power stations in space close to the Sun that were needed for the ambitious missions he was thinking about.
@Horatio – While there is carbon fuel in abundance on Titan, there is no free oxygen to burn it with. Sometime in the future, it may be that Titan's hydrocarbons become the largest source of feed stocks for carbon structures and artifacts. Sail transport might make this viable economically, rather than brute force synthesis from carbonate rocks and water.
Rob Henry November 8, 2014, 21:23
Alex Tolley, in principle you might be able to lift carbon out of Titan's gravity well for 11% the energy cost of reducing CO2, but such a scheme would suffer multiple problems if we are ever to expect it as a vision of the future. I will try to list them.
1 We are assuming the oxygen is a waste product to be discarded. If we need O2 we would find a lower cost in obtaining it from (cometary) CO2 than water. The C would then come free.
2 If he have ANY H2 freely available, once more we get C for free from CO2 with water as the waste product.
3 Titan's spin is so slow we could never build a space elevator there. We can however take its N2 for free if we can ever combine waverider technology with the slingshot effect. Thus huge amounts of N2 (for O'Neill habitats) might come from Titan, but only about 2% carbon should tag along.
4 There is oodles of C everywhere, except the inner solar system – organics being more common than rock. A very short space elevator on Haumea would just spew it out to wherever we wanted – to give but one example.
Oh, In point 4 it might be important to note I was thinking of exporting Haumea's CH4 in preference to its CO2, thus giving Titan no advantage there at all.
@Paul Gilster November 8, 2014 at 12:46
'Michael, as we get up into these speed ranges, we'll also be needing serious shielding against what impacts do occur. Lots to work on there as we conceive of spacecraft moving at even modest percentages of lightspeed.'
We currently have the tech to stop high energy atomic impacts very easily,
surprisingly a 300 micron aluminium/Mylar layer is enough to stop 4.5 MeV protons (10% c) or reduce the velocity of a significant number of them. A nice thing about a needle design is that a very high positive voltage can be produced at the tip which is strong enough to deflect positive charges away from the craft. Dust is also quite rare in space and not massive at all ~10^-17 kg.
@ Rob – And thus are the Saudi States of Titan stillborn. Someone should create a website collecting these sorts of calculations so that space resources can be categorized by availability and energy cost. Good to know that N2 is Titan's most valuable resource when greening the solar system.
Eniac November 9, 2014, 18:43
Penetration depth increases pretty rapidly with energy, and more rapidly with velocity. At 30% c you already will need an inch or so of aluminum, I think. Using charge (or magnetic fields) to deflect the ISM would be a good idea, in principle, if only the ISM were to cooperate and be charged. Alas, it isn't, at least not in our galactic neighborhood. So, we'd have to efficiently ionize it ahead of the vehicle, somehow, which creates whole new levels of complexity and mass requirements. Better to just absorb it in a shield, I suppose.
At around 30% c the radiation that was ISM also starts to deposit large amounts of heat, which will require the shields not only to be thick, but also refractory and white hot in order to reradiate the imparted energy. This effect goes up with the third power of velocity, and becomes very, very limiting beyond 30% c. Tungsten or carbon may be the two materials best suited to the task, rather than aluminum.
Michael November 10, 2014, 1:23
If you work out the energy of hitting the ISM gas (1/cm^3) at 0.3 c it is quite low 0.154 W/cm^2, even an ISM dust particle ~10^-17 kg will do little. As for the neutral particles a strong electric field will have the effect of ionising them as they approach it and then perhaps a magnetic field could be used to deflect them. We must be careful with the type of materials used as at high enough energies neutron spalling becomes a problem.
With larger craft I thought about using a radiation channel all the way through the crafts stages, they don't have to physically touch, from the reaction chamber exhaust. The high energy light radiation and neutrons would be reflected off the low angled walls of the channel and out the front (the channel entrance could be adjustably magnetically pinched to allow charged radiation through). The radiation would be sufficient to not only ionise neutral gases but also move the ionised ones as well using the gamma ray/neutron component.
Eniac November 11, 2014, 1:05
0.154 W/cm^2 is brighter than sunshine, so it is not really low. And it rises very fast at higher velocities. I am not sure you can ionize the ISM with radiation. It would require incredibly dense radiation to be sure to hit most of the atoms.
Eniac November 11, 2014, 13:28
Michael, I get a different result from yours: 0.3 c is 10^8 m/s, or 10^10 cm/s. That means 10^10 protons per second per cm^2. Each proton has a mass of 1.7*10^-27 kg, or an energy of 0.5*mv^2 ~ 8*10^-8 Joule. Power is incidence rate (10^10/s) times energy (~8*10^-8 J), coming to about 800 W/cm^2. This is 5000 times your result, and it implicates an equilibrium temperature of more than 7000 K, which is hotter than the surface of the sun and cannot be withstood by any materials.
I am not sure what is wrong here. May be you could double-check my calculation and point out the mistake?
When using a solid shield, assuming my above calculation is correct, the maximum velocity we could go is around 0.1 c. Beyond that, blocking shields are going to get too hot. An alternative to a fully blocking shield would be a thin foil, which could strip the electrons from the incoming hydrogen atoms without absorbing too much energy to radiate back into space. The remaining protons could then be diverted somehow by electromagnetic fields so they never impact any part of the ship. The foil would be subject to heavy erosion and would have to be constantly renewed, in my estimation. Whether the resulting consumable mass burden is prohibitive remains to be calculated.
Others have suggested droplet spray as a shield, which presumably is afflicted with a similar or worse consumable mass burden.
Rob Henry November 11, 2014, 17:32
Michael and Eniac, I have noticed that estimates of the ISM density seem to vary greatly, but not by the orders of magnitude that would relsolve your disagreement.
Eniac, I note you continue to concentrate on the macroscopic effects, yet it is very hard to believe that the microscopic effect of erosion will not dominate over those minor considerations. At 0.3c the proton hitting the shield would only have to impart a few billionths of its kinetic energy on a surface molecule that it disturbs for that molecule to fly free. In theory, each proton could loosen millions of (metal) atoms, but it would more likely only effect just a handful, Still we are talking about the potential loss of about a 100-1000 kg of metal for every kg of ISM intercepted. I think current ideas of shielding around or above 0.1c may turn out to be fantasy.
Michael November 11, 2014, 18:11
@Eniac November 11, 2014 at 13:28
It looks like you have used cm/s as the velocity when it should be m/s, I get approx ~600W/m^2 (~body temperature with an ideal radiator), I had fat fingers by putting a 2 in the mass of the proton in my first result.
The radiation output from the exhaust down the channel will be around 10-100 MW of spectrum radiation, if I remember 50 % at~10000 K is the ionisation temperature of hydrogen, gamma rays would interact with ionised hydrogen atom directly. That amount of radiation is going to hit something for sure. I can't see the ISM been a problem, a rock will be a problem though!
ProjectStudio November 12, 2014, 0:48
@Eniac
Average space density is likely be 1 atom per cubic cc, but in the local interstellar cloud may be a tenth of this, or in the local bubble a twentieth (0.05 atoms/cc), which would adjust your calculated result in the range from 4 – 80 W/cm^2
https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Interstellar_medium.html
So the heat could be manageable at one third light speed, depending on the locale, direction and distance to be traveled.
Sorry, should have been a range of 40 – 80 W/cm^2
Alex Tolley November 12, 2014, 11:14
ISM density => 10^6 molecules/cm^3 (max) – 10^-4 (min) [Wikipedia]
Distance to a-Centauri cm = 4.3 * 365*24*3600 * 3*10^5 km
= 4.3 * 365*24*3600 * 3*10^5 * 10^5 cm
~= 4 * 10^18 cm
=> 4 * 10^24 molecules.
=> 4 * 10^24 / 6 * 10^23 gm H
~= 7 gm.
Call it 10 gm as a round number.
10^-9 gm
What this suggests to me is that the erosion problem is going to be severe in the cool dense ISM, but negligible in the hot, ionized ISM (where repulsive fields may work). Therefore navigation is going to be important and that ISM density maps will be as important to stellar craft as winds and currents were to sailing ships.
Do we need to send out fast probes to do the mapping (slow, limited data, and expensive), or can we do this with telescopic instruments within the solar system?
@Rob Henry November 11, 2014 at 17:32
'Eniac, I note you continue to concentrate on the macroscopic effects, yet it is very hard to believe that the microscopic effect of erosion will not dominate over those minor considerations. At 0.3c the proton hitting the shield would only have to impart a few billionths of its kinetic energy on a surface molecule that it disturbs for that molecule to fly free.'
If we have 1 proton/cm^3 and we went all the way to A Centauri every one of the surface atoms would be hit-on average-. It is quite true that a hit would disrupt the chemical bonds of a large number of atoms but I see only a few would escape from the surface, lets say 1000. Now there are 6 x 10^-9 kg of material per cm^2 all the way to A.C so lets say we lose 1000 times that which is 6 x 10^-6 kg or about 60 grains of salt per cm^2
There are ways to reduce the loss as well, if we say made the shield from iron and a powerful magnetic field applied it could force some of the atoms to return to the shield by magnetism, I like the adjustable magnetic liquid best. We could also have a thin layer of low density material on top which would allow the atoms in but not allow the sputtered atoms back out or at least reduce the number of escapees.
Thanks ProjectStudio for the link
Space is empty. You just won't believe how vastly, hugely, mind- bogglingly empty it is. I mean, you may think your refrigerator is empty, but that's just an empty tin of peanuts to space.
Michael, I love simplicity. Rather than mix units (eg use of cm and joule/watt instead of erg) allow me to stick to SI. Your atom per cm3 becomes a million per cubic meter.
Now let us work with that ISM to alpha centauri (4×10^16m away). We thus intercept 4×10^22 atoms/sqm. If we lost a thousand W atoms (with a molecular weight of 3×10^-25kg) to each proton that would be a loss of
4×10^22 x 3×10^-25 x 1000 = 12kg/sqm.
This is not insuperable if it is kept to below this, but is significant. I think you forgot that shield atoms will likely be 25 – 300 times heavier than the proton (with B or C being the only notable exceptions)
One thing I must ask: is it possible to have waves in the ISM that are, say, 100x denser? If it is, then hitting a small patch of it would melt the shield at 0.3c anyway.
Michael is right, I used the wrong units for the proton energy, thereby being off by four oders of magnitude. Good thing, too! So, thick shields should work pretty well up to 0.6 or 0.7 of c. Sorry about the false alarm, I feel terrible.
Rob Henry has a good point about sputtering, one I have made myself before. I think it applies more to thin sails or ionization foils, less to thick shields where most of the time the particle travels in the interior where displaced atoms cannot escape. You will get crystal structure defects, but metals should do just fine with that, perhaps even improve. There will be ablation at the surface, though, and Michael has provided a reasonable estimate for that..
Alex is right about the great variety of ISM that is out there, except that I think it varies on a scale much larger than individual stars, such that we are probably stuck with a pretty even density of whatever it happens to be in our neighborhood. As ProjectStudio says, it seems we are lucky and it is quite a bit less dense than the average. So, all is good with thick shields, as long as we are not talking significant gamma factors (Sorry, Tau Zero…).
Thin sails, on the other hand, as well as micro-spacecraft, will probably still be quickly overwhelmed by the sputtering. This should be confirmed by actual calculations, of course. Particle physicists have a lot of experience firing energetic particles through thin foils. I believe I read somewhere those do not last long, but I am not knowledgable about that, myself.
Rob Henry November 13, 2014, 2:37
Perhaps it would help if I give a ballpark estimate of the extent of the erosion, especially since I have never seen that done before. Here goes.
The protons hit the shield at such high velocities that we may expect that the first cause of friction will be more due to broken bonds than molecules vibrating within a lattice. Let us call the proportion of all energy that goes into breaking bonds X. If the shield is warm, those bonds will reform. If the shield is cold, they will not causing it to become brittle. Now a kilo of H at 0.3c has 4000 million MJ, thus breaking 900 million Xkg of tungsten.
Next we need to know what proportion of those molecules are near enough the surface to escape. Michael mentioned a 300 micron penetration depth, but the energy distribution will be skewed toward the surface. I will assume that skew conveniently cancels X, and that only the very top surface layer can escape. 300 microns is close to a million interatomic distances.
Finally we have it, about a ton of shield for every kg of ISM intercepted – so Michael's earlier estimate might have been right to within an order of magnitude, and mine a couple of orders too high.. Mind you, doing the exercise shows how a tiny bit of ISM can make a huge amount of shield brittle if it ever gets to cold for broken bonds to reform!
is it possible to have waves in the ISM that are, say, 100x denser?
Aren't we likely to get that just by random distributions? Then there are the wave fronts due to nova/supernova explosions that I assume are higher densities than their local ISM. It just seems unlikely to me that the ISM is evenly distributed except on large scales. At some scales there is likely to be density variation that would affect the ship. If so, local density changes could feel like more than mild "buffeting". I see this as analogous to the solar weather, but at different scales (although this scale may be greater than the distance to alpha Centauri.)
Rob: I don't think breaking of bonds is the issue here so much as knocking atoms completely out of their positions, leaving holes. In metals, there aren't really bonds so much, at all, anyway.
I found the following paper on sputtering: http://authors.library.caltech.edu/4676/1/OLLprl76.pdf. It describes 12 MeV protons incident on niobium, which, I believe, is pretty close to our situation.
It appears that the yield values are generally not far from 1, never above 10. This bodes well, as it would mean that surface erosion could be quite minimal. Assuming a yield of 5, we might lose only 10 or so microns on a trip to Alpha Centauri. This is bad if you want a sail that is much thinner than that, but it should work very well for a thick solid shield. I am beginning to feel outright optimistic about this issue.
Oh, it helps noting that I assume the amount of ISM material between here and Alpha Centauri to amount to a layer of a few microns, were it condensed. I recall once calculating that to be the case, but we all know the reliability of my calculations by now….
'Now let us work with that ISM to alpha centauri (4×10^16m away). We thus intercept 4×10^22 atoms/sqm. If we lost a thousand W atoms (with a molecular weight of 3×10^-25kg) to each proton that would be a loss of
Good spot Rob, i forgot it was heavier atoms that would be ejected but surprisingly there are only a few ejected at the surface as most of the energy is dumped in the interior of the material, think of the bragg peak.
http://en.wikipedia.org/wiki/Bragg_peak
Perhaps nanotubes aligned with the axis could do the job of channeling the oncoming material into the interior where there is no escape.
'If the shield is warm, those bonds will reform. If the shield is cold, they will not causing it to become brittle.'
Hydrogen embrittlement is a possible issue but annealing could possibly be used to remove it. I am thinking of a possible magnetic liquid that can be adjusted in depth so that if a large dust particle is sensed it could be thickened in that area before impact.
'Good thing, too! So, thick shields should work pretty well up to 0.6 or 0.7 of c. Sorry about the false alarm, I feel terrible.'
Don't worry about it, I once had the job of getting some expensive ceramic bearings made up for a machine, I asked for imperial when the machine was metric. The engineer who had the job of putting the imperial bearings on the metric shafts was found in a great deal of sweat and distress! I am sure they have all forgotten about it by now but I haven't.
So in order to protect the craft we may need active, geometric and passive protection but I don't see a great issue about it. Larger dust is an issue, one hit of a grain of sand and there is going to be a big bang.
This however is not going to help us slow down.
Ole Burde November 14, 2014, 8:03
Here's a question : If we use a Ramscoop to decelerate , would there be a profitable element of "recycling" of particles ? I can imagine that a certain fraction of the exhaust particles wil collude repeatedly with other particles ,gradually slowing them down and perhabs leaving a trail of awaiable material for the ramscoop to re-use ?
@ole Burde, if the ejected particles collide with the ISM, it will increase their velocity in the direction of flight. This will reduce the effectiveness of the ISM as a braking medium. So recycling in this case is just like recycling rocket exhausts, it cannot work. If we use the ramscoop idea, we really need to fire the particle exhaust as a narrow beam outside the cone of the scoop so that we get the thrust benefit without disturbing the scoop drag.
Ole Burde November 14, 2014, 16:15
Allex Tolley : Firing outside the cone is the first-order logic solution , but perhabs there is another : What if multiple collutions will bring the fired particles to a low average speed far far awy from the vehicle ,most of the energy having been translated into radiation . The ramscoop would then meet a bigger concentration of particles MUCH later in the process , perhabs several decades later , and this might happen exactly when the speed otherwise would fall below the minimum value of effective "scooping" …It would demand that the beam would be extreemely narrowly focussed in order to NOT desturb mot of the stuff being scooped (exept for very small spot in the middle) from the medium range path of the vehicle , but this problem of focussing a beam narrowly for an extreemly long range , is one that will have to be solved anyhow in order to get accelerated away from earth .
Michael, your magnetic liquid intrigues me. What about the Curie temperature?
http://en.wikipedia.org/wiki/Curie_temperature
Did you mean a magnetic fluid? or were you really thinking of a liquid?
Thanks Michael for that Bragg peak information. It certainly helps limit the problem.
Thanks for that sputtering reference Eniac. The results seem at least an order of magnitude less than my estimate, and in line with what might be expected if factoring in that Bragg peak – interesting. A quick and simplified calculation by me puts the energy of a .3c proton at 50 MeV and these were 12 MeV.
On the completely different matter of the internal structure becoming brittle, though metal bonds are different than ceramic, I am pretty sure the bonds will not reform at cryogenic temperatures – though their activation energies will be lower. My guess is that 50-100 K is where that trouble might start, and I would love to see that experiment repeated at those temperatures.
Rob: Even though my most prohibitive calculations were, luckily, wrong; at 0.3 c we are still talking an energy deposition comparable to terrestrial sunshine on a black surface, which would make cryogenic temperatures very difficult to maintain. And why would we want to?
'Michael, your magnetic liquid intrigues me. What about the Curie temperature?'
I was thinking along the lines of a ferro-fluid in which we can control a peak to face an on coming particle very fast. If we can do that we could handle much larger particle impacts. It would be a compromise between the mass of the system used to control it and its effectiveness at stopping large particles. My thought are of using a metal eutectic, maybe Galinstan, which has a low vapour pressure and melting point (-19 C) mixed with a nano-ferro magnetic material. There are lower ones than this.
http://en.wikipedia.org/wiki/Galinstan
http://en.wikipedia.org/wiki/Ferrofluid
http://nldlab.gatech.edu/w/images/6/6a/Presentation.pdf
A Eniac writes 'cryogenic temperatures would be very difficult to maintain'. at the front of the craft due to on coming material, he is correct and this would benefit us. My worry at high velocities is neutron spalling and secondary radiation.
As for slowing down a magnetic sail I wonder if it is possible to have a close approach of a red dwarf (we can get very close) and enter the leading rotation region of the star and cut its powerful magnetic field. There are sure to be a lot of ions trapped in a belt around the equator which would interact with the crafts magnetic field as well adding to the braking effect of the magnetic field coupling.
Just bouncing an idea out there.
@Michael, I'm not sure that a ferrofluid is what you want as it is a solid liquid mix – or colloid. Those galinstan type liquids sound more promising iff all their main constituent (surface) atoms are magnetic.
@Eniac, estimates of the ISM in our region vary. Above, someone thought that one of the best estimates for it locally was only a 20th our standard million/m3 working figure. In ceramic, even 300K is not warm enough to remove all the damage.
http://en.wikipedia.org/wiki/Thermoluminescence_dating
At lower temperatures we will have even more problems. I estimate that about a 10% the energy of these particles showers will go into breaking bonds. From my above figure for a W shield, that would mean a single gram of ISM powderising to the atomic level 100 tons of tungsten. The grain size at failure should be well above atomic level, so perhaps the true figure is even worse.
Michael, If you are breaking close around a red dwarf after having come of 0.3c then you are a braver man than I. My thinking is, that for the extra paraphernalia and its optimization to be worth it the breaking effect would have to be significant. If we had already bled off 99.9% of our kinetic energy, we would still be traveling at 1% c. Now at such speeds we would pass through a path of 0.1AU in 5000 seconds, so breaking a sizable chunk of the rest of the kinetic energy with 0.1% of that energy going into vibrational heating would cause a payload/sail with the specific heat capacity of water to want to heat up at the rate 200K/s. Most materials have a lower specific heat capacity than water.
Above, to be consistent with earlier dissuasions, I should have said we need to dissipate 1 MW/kg at 0.1% efficiency.
'I'm not sure that a ferrofluid is what you want as it is a solid liquid mix – or colloid. Those galinstan type liquids sound more promising iff all their main constituent (surface) atoms are magnetic.'
It does not matter if the surface atoms are magnetic only that the liquid response to a controlling field to shift fast.
'At lower temperatures we will have even more problems. I estimate that about a 10% the energy of these particles showers will go into breaking bonds. From my above figure for a W shield, that would mean a single gram of ISM powderising to the atomic level 100 tons of tungsten. The grain size at failure should be well above atomic level, so perhaps the true figure is even worse.'
The bonding strength of materials is meaningless at such high velocities, even if it is a problem perhaps we could inject a metallic liquid into the powered tungsten material to keep it intact with a much lower melting point.
'Now at such speeds we would pass through a path of 0.1AU in 5000 seconds, so breaking a sizable chunk of the rest of the kinetic energy with 0.1% of that energy going into vibrational heating would cause a payload/sail with the specific heat capacity of water to want to heat up at the rate 200K/s.'
There is a lot of energy to get rid of, I think even vaporising hydrogen, which has a higher heat capacity than water would not remove the energy. Maybe using the technique below a certain velocity would be better.
Yes Michael, the bonding strength WOULD be meaningless if it is warm enough for bonds to reform or if we are in a true liquid. Eg,, at a guess, those colloidal particles in a ferrofluid might get broken up ever finer by the protons till they loose their magnetism.
'Eg,, at a guess, those colloidal particles in a ferrofluid might get broken up ever finer by the protons till they loose their magnetism.'
Iron does not lose its magnetism at the atom scale.
Now as to whether tungsten would be a suitable shield material it appears not, the energy aborbed during the 4.3 ly trip to A.Cent would need a shield over three meters thick per cm^2 (7.7 kg) to prevent all the bonds been broken.
Hydrogen would have no such problem which would require only 0.061 kg per cm^2 or much less because of the rebonding process that would take place naturally. Keeping the hydrogen contained at temperature would be an issue though but not insurmountable and compounds of hydrogen could do the trick.
As for slowing down the sail I am still thinking of a fission reaction start up at the start of the deceleration phase which spreads the fission/products onto the target star side of the sail, in essence using a fission fragment process.
Chris (from MN) November 23, 2014, 1:41
Why use photons if you're not going near the speed of light but are only going at a maximum of 5-10% or 30% of c?
It's 10-100x more efficient to send a beam of subrelativistic dust particles (initially charged for acceleration in a large, linear accelerator then neutralized to keep them from being pushed around by the solar wind and magnetic fields). The particles can be vaporized, perhaps by a laser or a particle beam on the target craft, as they near the target craft and then the subrelativistic plasma's momentum can be captured by a small magnetosail (and some of its energy used to power the laser). Importantly, this also means you don't need enormous laser optics and you could actually contemplate engineering this sort of thing.
Once you near the target system, you would expand the magnetosail to brake against first the interstellar medium and then the stellar wind of the target system.
I think this combination is much more efficient and practical than almost any other system of interstellar travel I've seen mentioned. And we could use it for exploring the outer portions of our solar system (like the Oort cloud), as well. The high efficiency of the concept (and lack of a need for solar-system-spanning optics precise to within tenths of microns) would allow it to possibly be built on some scale in this century, and certainly some of the main technical uncertainties (how do you accurately aim subrelativistic dust particles? how do you build an accelerator capable of gigawatts of efficient acceleration? how do you vaporize subrelativistic dust particles efficiently and precisely at a distance?) could be resolved at the lab scale this century.
Paul Gilster November 23, 2014, 14:46
Chris, some of these issues show up in "Smart Pellets and Interstellar Propulsion": https://centauri-dreams.org/?p=31062
and you may also want to check "Clifford Singer: Propulsion by Pellet Stream": https://centauri-dreams.org/?p=31057
Your post also recalls Jordin Kare's SailBeam concept in some ways: https://centauri-dreams.org/?p=31049
Like you, I find the particle/pellet stream concept very interesting. Nordley's 'smart' pellets seem promising once we get to that level of nanotech.
Next post: Tennessee Valley Interstellar Workshop
Previous post: Hybrid Strategies for Deep Space


text:
Q: Get data using node.js from mongoDB I'm trying to get data from mongoDB.
In my schema year - is not unique so I did the following:
 app.get('/getBestByYear/:year', function(req, res) {
Stud.find({}).where('year').in(req.params.year).where('grade').gt(89).exec(function(err,students){
            if(err) throw err;
            res.json(students);
         });
     })

I get an empty string.. What did i do wrong?

A: you can try this code
console.log(req.params.year);   // show to verify year is valid
Stud.find({year: {$in: [req.params.year]}, grade: {$gt: 89}}).exec(function (err, students) {
    if (err) throw err;
    res.json(students);
})

redpajama_set_name: RedPajamaStackExchange


Sake is a fiendishly complicated category, but the majority of bottles can be placed into four distinct styles, based around the percentage of rice-grain polishing (seimaibuai), and whether the sake has had distilled alcohol added: junmai (no fixed polishing amount; no alcohol added); honjozo (minimum of 30% polishing; small amount of alcohol added); ginjo (minimum 40% polishing; alcohol addition optional); and daiginjo (minimum 50% polishing; alcohol addition optional).
The purest form of sake, with no fixed polishing percentage, and no distilled alcohol added.
A minimum of 30% polishing; a small amount of alcohol added to lighten and add fragrance.
Minimum of 40% polishing; alcohol addition optional – bottles labelled ginjo will have alcohol added; those marked junmai ginjo won't.
minimum of 50% polishing; alcohol addition optional – daiginjo sakes will have alcohol added; sakes labelled junmai daiginjo won't.
There is a special fifth category for unpasteurised sakes, called nama, which encompasses all four styles above.
Should I drink it hot or cold?
There is no definitive answer, but the more delicate styles, including ginjo and daiginjo, benefit from being chilled, while more robust styles such as junmai work well at room temperature, or gently heated. And while it's true that some inferior sakes are served warm to mask their faults, serving sakes warm per se is not a reflection on their quality.
So, the more the rice has been polished, the better the sake?
Not necessarily. Sakes made with higher polishing levels may well be more expensive, as the yield will be much lower and more rice needed to produce them, but they are not inherently better because of this.
Any other types of sake I should know?
Nigori sake is unfiltered; koshu means the sake has been aged; kijoshu sake is sweeter, thanks to sake added to the brewing water; and genshu is 'undiluted' sake, with a strength of 17-19% abv, higher than the 14-16% norm.


What's Beyond Forks?: Rogue's Pawn Tour! An interview with Jeffe Kennedy Plus an Excerpt!
Rogue's Pawn Tour! An interview with Jeffe Kennedy Plus an Excerpt!
I'm super excited about this tour! If you read my review of Rogue's Pawn, then you know it makes my day to have Jeffe Kennedy on the blog today!
Since about 1996. I came to writing later in life, after I discovered a career in science wasn't for me. But I started out as an essayist and writer of narrative nonfiction, so I've only been publishing fiction in the last 3-4 years.
A dream. A lot of my stories come from dreams and Rogue's Pawn was particularly that way. It was the first novel I wrote. I woke up on a rainy Saturday morning with the story in my head and sat and wrote on it for half the day.
When you first started writing Rogue's Pawn, did you plan for it to be a series?
I did—just because that initial idea for the story was so big. I wouldn't have planned it that way, but I knew from the beginning that it would take a while to tell all of Gwynn's journey.
Oooh. I'm in the thick of writing it and it hasn't been an easy book. Rogue and Gwynn take a lot of good steps to understand each other and then things happen. Gwynn ends up with a lot of responsibility on her shoulders. Starling is really growing as a person and confronting the reality of being a half-breed. Darling discovers his battle name at last!
Definitely Gwynn. As much as I try to cultivate her to be her own person – and she has grown – she is still, in many ways, my avatar. She's my most difficult character to write for that very reason.
Nobody at all? Hmm. That's a hard one. I'm kind of an open book. There are many things only my man or my mother knows. Or my cats—they see a lot that should never be mentioned.
Dragonflight by Anne McCaffrey. The binding has come apart.
To write every day, at the same time every day. I spent a lot of years resisting this advice. When I finally followed it, I became a writer.
That I'm not the storyteller – that the story comes from outside of me. It's a huge act of faith for me to sit down at the keyboard and trust that the story will come to me. Scary, too!
I love to read – whenever I can. It's even better if I can sit in the sun while reading. I also love to garden and take long walks.
Phedre no Delaunay, because I want to know what it would be like to be her!
"Enough," a male voice said.
As if I'd ceased to exist, Tinker Bell blinked her eyes and regained her lovely self, face smoothing, shining once again in sunny elegance. Reboot and resume program. She gracefully stood and glided to the tray, set the bowl precisely in the center, lifted the tray and left the room without hesitation.
Booted footsteps crossed the room toward me. Act II, scene ii. Exit Nasty Tinker Bell, Enter God-Only-Knows-What-Now. My face was sticky with whatever the brothy stuff had been, my hair wet and fouled. I stank. I hurt. I was chained to a bed in a place so completely unknown I couldn't begin to understand it. I tried to squeeze my legs closer together, but the chains seemed at the limit of their reach. The energy of my brief triumph evaporated, allowing tears to well up again.
Oh, please, please, please, do not cry. The threatening sting worsened. I closed my eyes and one tear leaked out. He stopped next to me, surveying me.
"You're certainly a mess." His wry voice was rich and smooth.
My eyes snapped open to glare at him through the blur. Fifty different smart remarks flew across my tongue, most along the lines that any failures of appearance on my part could be laid on the doorstep of someone besides myself. But even the buzz of the first word on my vocal chords brought searing agony. Relieved to have a legitimate reason for the tears, I almost welcomed the searing sensation.
I thought of the birds crashing in increasing cacophony with a small shudder.
My stomach congealed in panic. Had he heard my secret thoughts? Don't think of them, bury them deep, deep. Think of other things…like what? Think of home, think of Isabel. Isabel, my cat—Clive hated her. What would happen to her now? How could I not have thought of her until this moment? Abandoned, wondering why I never came home for her… And my mother—she'd be frantic. How long had I been gone? They could be all dead and buried, lost to me forever. The anguish racked me.
"Shh." The man sat on the side of my bed now, heavier than Nasty Tinker Bell. He brushed the hair back from my forehead, then placed his long fingers over my brow and, with his thumbs, rhythmically smoothed along my cheekbones, wiping away the tears that now flowed freely.
I stifled a sob. I had cried more in the past day than I had in years. The sweeping along my cheekbones soothed me, melting warmth through my skull. The rhythm became part of my breathing. Deep breaths. Smooth, easy. The awful tightness in my chest gave a little sigh and released.
"Let's try again, shall we?" The man pulled his hands away. I could hear him brush them against his thighs. Soup, tears and blood. Yuck.
My eyes cleared enough for me to see him. Ebony-blue climbed over half his face. The winding pattern of angular spirals and toothy spikes swirled out of his black hair on the left side of his face, placing sharp fingers along his cheekbone, jaw and brow. For a moment, the tattoo-like pattern dominated everything about him. Ferocious and alien.
Once I adjusted, I could see past the lines. His face echoed Tinker Bell's golden coloring. He could be her fraternal twin, with those same arched cheekbones. But where she was golden dawn, he was darkest night. Midnight-blue eyes, that deep blue just before all light was gone from the sky, when the stars have emerged, but you could see the black shadows of trees against the night. He shared Tinker Bell's rose-petal mouth, but with a curious edge to it. I suppose a man's mouth shouldn't remind one of a flower, and there was nothing feminine about this man. Where she wore the pink sugar roses of debutantes and bridal showers, his lips made me think of the blooms of late summer, the sharp-ruffled dianthus, edges darkening to blood in the heat. His bone structure was broader than hers but still seemed somehow differently proportioned, his arms hanging a bit too long from shoulders not quite balanced to his height. Inky hair pulled back from his face fell in a tail down his back. One strand had escaped to fall over his shoulder and I could see a blue shimmer in its silk sheen.
He arched his left eyebrow, blueness in the elegant arch, repeating the deep shades of the fanged lines around it.
I stared at him. What was the question?
Don't forget to check out my review of Rogue's Pawn!
To learn more about Jeffe Kennedy and her books, visit her website.You can also find her on Facebook and Twitter.
Thanks for hosting me - it was a fun interview!


Our Company was founded in 1850 by William Davis Jr and incorporated as Davis Modern Heating & Cooling in 1982. The Company started with wood & coal heat in the 1800s and then oil heat in the 1920s.
Today, we service all brands of heating and air conditioning equipment. We install High Efficiency Furnaces, Air Conditioners, Heat Pumps and Boilers to match any fuel source including natural gas, propane, heating oil and electric.
We have over 35 years of experience with solar heating and geothermal heat pumps. We are proud to be known as America's Oldest Family Owned Mechanical Contractor.


text:
package org.apache.asterix.runtime.evaluators.functions;

import java.io.DataOutput;

import org.apache.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
import org.apache.asterix.om.base.AMutableString;
import org.apache.asterix.om.base.ANull;
import org.apache.asterix.om.types.ATypeTag;
import org.apache.asterix.om.types.BuiltinType;
import org.apache.asterix.om.types.EnumDeserializer;
import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
import org.apache.hyracks.api.context.IHyracksTaskContext;
import org.apache.hyracks.api.dataflow.value.ISerializerDeserializer;
import org.apache.hyracks.api.exceptions.HyracksDataException;
import org.apache.hyracks.data.std.api.IPointable;
import org.apache.hyracks.data.std.primitive.UTF8StringPointable;
import org.apache.hyracks.data.std.primitive.VoidPointable;
import org.apache.hyracks.data.std.util.ArrayBackedValueStorage;
import org.apache.hyracks.dataflow.common.data.accessors.IFrameTupleReference;

public abstract class AbstractTripleStringStringEval implements IScalarEvaluator {

    private ArrayBackedValueStorage resultStorage = new ArrayBackedValueStorage();
    private DataOutput dout = resultStorage.getDataOutput();
    private IPointable array0 = new VoidPointable();
    private IPointable array1 = new VoidPointable();
    private IPointable array2 = new VoidPointable();
    private IScalarEvaluator eval0;
    private IScalarEvaluator eval1;
    private IScalarEvaluator eval2;

    private AMutableString resultBuffer = new AMutableString("");
    @SuppressWarnings("rawtypes")
    private ISerializerDeserializer nullSerde = AqlSerializerDeserializerProvider.INSTANCE
            .getSerializerDeserializer(BuiltinType.ANULL);
    @SuppressWarnings("rawtypes")
    private ISerializerDeserializer strSerde = AqlSerializerDeserializerProvider.INSTANCE
            .getSerializerDeserializer(BuiltinType.ASTRING);

    private final UTF8StringPointable strPtr1st = new UTF8StringPointable();
    private final UTF8StringPointable strPtr2nd = new UTF8StringPointable();
    private final UTF8StringPointable strPtr3rd = new UTF8StringPointable();

    private final FunctionIdentifier funcID;

    public AbstractTripleStringStringEval(IHyracksTaskContext context, IScalarEvaluatorFactory eval0,
            IScalarEvaluatorFactory eval1, IScalarEvaluatorFactory eval2, FunctionIdentifier funcID)
                    throws AlgebricksException {
        this.eval0 = eval0.createScalarEvaluator(context);
        this.eval1 = eval1.createScalarEvaluator(context);
        this.eval2 = eval2.createScalarEvaluator(context);
        this.funcID = funcID;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void evaluate(IFrameTupleReference tuple, IPointable result) throws AlgebricksException {
        eval0.evaluate(tuple, array0);
        eval1.evaluate(tuple, array1);
        eval2.evaluate(tuple, array2);

        resultStorage.reset();
        try {
            if (array0.getByteArray()[array0.getStartOffset()] == ATypeTag.SERIALIZED_NULL_TYPE_TAG
                    || array1.getByteArray()[array1.getStartOffset()] == ATypeTag.SERIALIZED_NULL_TYPE_TAG
                    || array2.getByteArray()[array2.getStartOffset()] == ATypeTag.SERIALIZED_NULL_TYPE_TAG) {
                nullSerde.serialize(ANull.NULL, dout);
                result.set(resultStorage);
                return;
            } else if (array0.getByteArray()[array0.getStartOffset()] != ATypeTag.SERIALIZED_STRING_TYPE_TAG
                    || array1.getByteArray()[array1.getStartOffset()] != ATypeTag.SERIALIZED_STRING_TYPE_TAG
                    || array2.getByteArray()[array2.getStartOffset()] != ATypeTag.SERIALIZED_STRING_TYPE_TAG) {
                throw new AlgebricksException(
                        funcID.getName() + ": expects input type (STRING/NULL, STRING/NULL, STRING/NULL), but got ("
                                + EnumDeserializer.ATYPETAGDESERIALIZER
                                        .deserialize(array0.getByteArray()[array0.getStartOffset()])
                                + ", "
                                + EnumDeserializer.ATYPETAGDESERIALIZER
                                        .deserialize(array1.getByteArray()[array1.getStartOffset()])
                                + ", " + EnumDeserializer.ATYPETAGDESERIALIZER
                                        .deserialize(array2.getByteArray()[array2.getStartOffset()])
                                + ".");
            }
        } catch (HyracksDataException e) {
            throw new AlgebricksException(e);
        }

        strPtr1st.set(array0.getByteArray(), array0.getStartOffset() + 1, array0.getLength());
        strPtr2nd.set(array1.getByteArray(), array1.getStartOffset() + 1, array1.getLength());
        strPtr3rd.set(array2.getByteArray(), array2.getStartOffset() + 1, array2.getLength());

        String res = compute(strPtr1st, strPtr2nd, strPtr3rd);
        resultBuffer.setValue(res);
        try {
            strSerde.serialize(resultBuffer, dout);
        } catch (HyracksDataException e) {
            throw new AlgebricksException(e);
        }
        result.set(resultStorage);
    }

    protected abstract String compute(UTF8StringPointable strPtr1st, UTF8StringPointable strPtr2nd,
            UTF8StringPointable strPtr3rd) throws AlgebricksException;
}

redpajama_set_name: RedPajamaGithub


text:
Alco var ett bilmärke som tillverkades av ett dotterbolag till American Locomotive Company i Providence, Rhode Island i USA.

Man började med att tillverka franska Berliet-bilar på licens (dessa såldes under namnet American Berliet fram till 1908). De första egna modellerna var kedjedrivna och 4-cylindriga på 22 eller 40 hästkrafter. Alco kom att betraktas som en av de bästa amerikanska bilarna och var av mycket hög kvalitet. Både år 1909 och 1910 vann Alco-bilar tävlingen Vanderbilt Cup. Firman lade stor vikt vid eleganta och välbyggda karosser, och ett brett vitt band runt karossens överkant blev ett kännetecken. Fabriken brukade stolt framhålla att deras bilar var bland de allra dyraste i USA. Man tjänade dock inga pengar på dem, och 1913 lades biltillverkningen ner. Cirka 5 000 Alco-bilar av 54 modeller hade då tillverkats, och den genomsnittliga förlusten för varje bil var 460 dollar.

Källor
Cars Stora Billexikon, band 1

Ej längre existerande amerikanska biltillverkare
Företag bildade 1901
Företag upplösta 1913

redpajama_set_name: RedPajamaWikipedia


OurEnergyPolicy.org | The Water-Energy Nexus: How Can Collaboration Lead to Greater Impact?
This prompt is the second in a series of discussions led by invited speakers at the upcoming 15th National Conference and Global Forum on Science, Policy and the Environment: Energy and Climate Change to be held January 27-29, 2015 in Washington, DC.
Energy and water systems have historically been designed and managed independently. However, the systems are, in fact, interdependent. In its simplest form, the energy-water nexus can be broken into two parts: "energy for water" —the energy required to treat, transport, or heat water—and "water for energy" —the water required for cooling thermoelectric power plants, oil and gas production, hydropower, and bioenergy feedstocks. In the future, the relationship between energy and water systems will evolve, driven by changing energy portfolios and technologies, changing precipitation and temperature patterns, and population growth and migration.
An integrated approach to addressing complex energy-water nexus issues can benefit from technology, policy, data, modeling, and analysis elements. A range of stakeholders can play an important role, including federal/state/tribal/local governments, private industry, NGOs, international organizations, foreign governments, academic institutions, utilities, and citizens.
1) What are the key elements that would distinguish such an integrated approach from a traditional approach?
2) How are goals, priorities, and supporting actions best identified and pursued?
3) Who are the key stakeholders, and what are their optimal roles?
• Department of Energy, The Water-Energy Nexus: Challenges and Opportunities, U.S. Department of Energy Water-Energy Tech Team, June 2014.
• Water in the West, Water and Energy Nexus: A Literature Review, Stanford University Woods Institute for the Environment and Stanford University Bill Lane Center for the American West, September 2013.
• World Bank, Thirsty Energy, Washington D.C., January 2013.
1) What are the key elements that would distinguish such an integrated approach from a traditional approach? 2) How are goals, priorities, and supporting actions best identified and pursued? 3) Who are the key stakeholders, and what are their optimal roles?
12 Responses to The Water-Energy Nexus: How Can Collaboration Lead to Greater Impact?
You are correct in your focus on pumped hydro, but only if we are to move toward a low carbon emission electric power supply.
The alternative carbon free renewable sources of power generation are limited by their unreliable operating characteristics. Wind and solar can only achieve 20% to 35% annual capacity factors; and so must be supported by reliable gas turbine generators to keep the lights on.. Of course, this also provides a great market for energy storage to cover the periods when wind and solar are unavailable. The problem is that wwe cannot find many suitable sites for pumped hydro or air storage capacity. Other storage schemes are not yet close to capable of meeting the demand.
We should also recognize that power generation plants, including conventional steam (rankine cycle) as well as gas turbine (brayton cycle) plants can be, and have been designed to operate with dry cooling systems. The operating cost penalty for steam plants can range up to 10%, to maybe 15% deepending on location and operating requirements. The operating penalty for simple (Brayton) cycle gas turbine plants is relatively insignificant. The aircraft jet engine is a good example.
In summary, conventional power generation plants need not rely on water for cooling. It is a matter of economics. Someone has to cover the increasaed capital and operating costs. Maybe as much as 20% rate increase?
I am very glad to see DOE linking the use of extractive energy generation and water as a criteria for future investment planning. To me there is only one conclusion for action … transition to wind and distributed renewables as soon as possible. 30% generation with no grid issues is possible by 2030, closing the equivalent old coal and nuclear generators, saving water as well as the climate and our air resources. Retrofitting buildings can reduce demand, providing for any projected increase of electricity demand according to many studies. Expanding electric and hybrid cars use would also be a 2 for 1 win.
The Union of Concerned Scientists – has a good study of the intersection of water and energy. Here is a summary of the facts they set out in a way that is easy to wrap your mind around.
•	One load of hot-water laundry (using electric appliances), requires 3 to 10 times more water at a nuclear or coal plant to produce the electricity needed to wash the clothes.
•	a typical 600-megawatt coal-fired power plant consumes and evaporates more than 2 billion gallons of water per year from nearby lakes, rivers, aquifers, or oceans. In the southeastern United States, power plants account for two-thirds of all withdrawals of freshwater.
•	Roughly 1/3 of all U.S. power plants use once-through cooling, and so return virtually all the water they withdraw, however it is returned 17 degrees hotter than when withdrawn. Half of all coal plants report releasing water in the summer at peak temperatures of 100°F or more. Not good for the fish!
•	Creating a single gallon of ethanol consumes, on average, about 100 gallons of freshwater. Electric cars are cheaper and cleaner.
•	Strip mining of coal by mountaintop removal has buried almost 2,000 miles of Appalachian headwater streams—some of the most biologically diverse streams in the country.
•	The arsenic, mercury, lead, and other toxic substances contained in the 120 million tons of coal plant waste produced every year can severely contaminate drinking water supplies. There is no good way to dispose of this waste. One Energy co. says removal of coal ash ponds could take 30 years, cost $10b. Most coal ash ponds are old and unlined and sited by rivers.
•	The process known as hydraulic fracturing that produces oil and gas can potentially lower local water quality, as well as strain local water supplies. Each well requires 2-10million gallons of water and 4 million pounds of sand. One Texas town was pumped dry.
•	38% of the areas where shale gas and oil is most abundant is arid or already under severe water stress according to the World Resources Institute. The wells should not be approved in those dry areas.
•	more than 2,500 small earthquakes that have hit Oklahoma in the past five years They can be linked to fracking wastewater injection. Other stidies are underway.
•	Neither EPA nor states monitor groundwater quality over time to detect contamination from Class II wells. Resources are limited for any kind of monitoring and enforcement for water and air pollution.
A new study by Center for Biological Diversity shows coastal fracking in CA is unique because CA's coastal fracking occurs at shallower depths and with higher concentrations of chemicals than in other areas.
•	Increased earthquake risk linked to fracking and the injection of fracking wastewater into disposal wells.
We no longer have to rely on extractive energy. As we transition to a new, largely distributed structure for our el should be required to look at the water/GHG nexus to limit our long-term investments.
I have prepared a "Gallery of Clean Energy Inventions" exhibit. See https://app.box.com/CLEANENERGYEXHIBIT. Its seven separate exhibits comprise of 41 new types of generators, 16 "Advanced Self-Powered Electric Vehicles" innovations, 25 radioactivity neutralization methods, 22 space travel innovations, 10 technical solutions to water shortages, and torsion field school network.
These inventions are so radical that some may require tens of millions of dollars each to fully exploit. $1 billion would establish a comprehensive proactive clean energy inventions evaluation and development organization headquartered in Nevada. Divisions would include Board of Directors, Corporate Library, Consultants, Teaching Institute, Technical Evaluation and Advisory Board, and Incubator of Russian and Ukrainian Inventions.
Speaking of the nexus of energy and water, seven of the ten "Technical Solutions to Water Shortages" rely on cheap or even free energy or electricity for enhancing the practicality of their respective water sources.
There is water in combusted fossil fuel exhaust, and this distilled water is very usable.
Industry and large commercial buildings consume a lot of natural gas for building space heating or to heat domestic or process water.
In the process of consuming this natural gas efficiently with the technology of Condensing Flue Gas Heat Recovery, this water will be created.
In every 1 lb of combusted natural gas there are 2 lbs of recoverable water.
There are no shortages of proposed pumped storage projects. http://www.ferc.gov/industries/hydropower/gen-info/licensing/pump-storage.asp. While gas plants are flexible, they can't absorb energy using water in oversupply situations such as with wind in the Northwest or the "duck curve" in California with regards to solar.
The integrated energy-water planning problem for the U.S. is a very complex issue that warrants a comprehensive mathematical/computer modeling approach to properly understand the overall impacts of different policy options. In the 1970's and 1980's, I worked on developing integrated mathematical models to understand the interactions of supply and demand for energy in North America, and to assess key policy options. Similar models should now be developed for integrated analysis of supply and demand for energy and water over time. Such models could be regional (e.g. for the U.S. Southwest), national, or for North America as a whole.
There are different methods to increase water supply, such as transporting water from water-rich regions to water-poor regions, and desalination of ocean water (a high-cost backstop technology). The demand for water, like the demand for energy, will depend on its price, and shortages of water supply will be reflected by a higher price (as is always the case in market economic systems). Higher-priced water will lead to less use and water-conservation policies being implemented. Econometric models of water demand need to be built that include the estimated price-elasticities of demand for water over time.
A multi-period linear programming model that minimizes the costs of overall energy and water supply (considering costs of supply technological options and constraints on energy and water supplies in each period) could be integrated with a multi-period econometric model of demand for energy and water, at consistent prices over time. See http://www.jstor.org/discover/10.2307/170225 for our dynamic equilibrium energy modeling methodology developed for the BALANCE Canadian energy model. The resulting "shadow prices" in the model for meeting an incremental unit of demand for energy or water in a time period would be good estimates of efficient market prices.
Such integrated supply/demand models for energy and water will of course depend on good estimates of water supply costs, price-responsiveness of demand, and interaction effects between energy and water (e.g. how much water is needed for natural gas fracking or different types of power plants, how much electricity is needed to transport water), and the sensitivities of the model results to these parameters can be examined. Environmental constraints on global warming greenhouse gas emissions should be included in the models. It would also be important to estimate the costs of preventing water contamination from fracking and coal use.
The building of such integrated energy-water supply/demand models would be the best way to understand the interaction of various supply technologies and policy options on the overall costs of supplying energy and water to meet projected future demand. Policy options could include: raising the price of water to consumers, instituting water-conservation approaches, requiring specified greenhouse gas and other environmental standards to be met, or developing new national and international water transportation systems. Using the integrated mathematical model of the energy-water engineering/economic system, the various policy options could be investigated in an objective and consistent overall framework to derive the most economically-effective long-run solution. This would be an illuminating approach for the various stakeholders, including energy producers, water supply companies, energy and water consumers, and local/state/federal government policy makers, to assess the impacts of proposed policy choices on a range of criteria of interest.
The Department of Energy's report Water-Energy Nexus: Challenges and Opportunities, U.S. Department of Energy Water-Energy Tech Team, of June 2014 identified the key challenge: Federal oversight and administration of water management guidelines is shared across approximately 30 agencies in 10 different departments. Similarly, federal funding for water is split across many agencies, with no single agency ultimately responsible for the impact of multiple contributors (e.g., agriculture, development, and energy) to water management. Highly fragmented authority in managing the country's water has presented challenges in improving water quality in many parts of the country.
Wet cooling of turbine exhaust steam at thermal power plants is the largest consumptive use of fresh water. Each kWh of electricity evaporates 1.8 liters of fresh water into the atmosphere. All that latent heat goes to waste, resulting in low fuel efficiency (heat rate).
ARPA-E recognizes the importance of water issues in power generation and has called for submissions to improve dry cooling, as an alternative to wet cooling, in order that thermal power plants (coal and nuclear) achieve the goal of cooling with no net water dissipation. Applications in ARPA-E eXCHANGE (http://arpa-e-foa.energy.gov). The deadline for submission of Full Applications is 5 PM Eastern Time on February 13, 2015.
The call for solutions is overly prescriptive, however, apparently limited to directly improving air cooling (Category 1) and supplemental cooling or cold storage (Category 2).
Air cooling is too weak (<1 W/cm2, even with blowers) to handle the huge heat flux in power generation. Air cooling at data centers is a challenge, and they are better funded than coal plants. The path to net zero water dissipation must involve reducing the size of the job of heat rejection to a scale that air cooling can handle. That is possible by making wet steam do work before going to the condenser, which has the collateral benefit of improving the heat rate.
We have serious water supply and access problem that will only be exacerbated by increased energy exploration and use, changes in climate, land use stresses, waste and inefficiency in the water and energy systems, poor pricing guidelines and practices, and end use waste including lack of recycling.
The net result is that 99.7% of all the water on earth is not available for human and animal consumption. Of the remaining 0.3%, much is inaccessible due to unreachable locations and depths, and the vast majority of water for human and animal consumption, much less than 1% of the total supply, is stored in ground water. •Experts do agree: Demand is greater than supply. And 36 states face water shortages in the next three years. Every day Arizona and parts of New Mexico use 300 million gallons more than they get in renewable supply. The extra comes from underground supplies which are not renewable. Top four water uses in USA, according to USGS is (in millions of gallons per day) 143,000 for thermoelectric, 130,140 for irrigation and livestock, and 44,200 for public supply and 19,310 for mining and industrial (of which half relates to energy resources), which leaes 16,000 for all other uses of water. For every ton of coal from 800-3,000 gallons of water is used for extraction, transport, store, process and disposal, and the US uses 1 billion tons of coals per year.
This report has been prepared in response to a letter to the Secretary of Energy from the chairmen and ranking members of the House and Senate Subcommittees on Energy and Water Development Appropriations, dated December 9, 2004, wherein they asked for: "a report to Congress on the interdependency of energy and water focusing on threats to national energy production resulting from limited water supplies, utilizing where possible the multi-laboratory Energy-Water Nexus Committee." ACEEE reort. "We Can't Have Water Without Energy, But How Much Energy Do We Need?" by Rachel Young, National Policy Research Analyst" shows (kwh/million gallons) shows 14,000 for wate source conveyance, 16,000 for treatment, 2,000 for distribution, 4,000 for wastewater treatment, and 2,000 wastewater discharge.
US General Accounting Office ENERGY & WATER NEXUS published in December 2012 concluded that thermoelectric power plants use a fuel source—for example, coal, natural gas, nuclear material such as uranium —to boil water to produce steam. The steam turns a turbine connected to a generator to produce electricity. Production of oil shale requires the heating of rock containing solid organic matter to between 650 and 1000 degrees Fahrenheit and injecting water into the formation to stimulate the oil to flow. To date, there has been no commercial production of oil shale resources, in part, because the energy requirements to heat the rock and the water needed to stimulate the flow of oil make the process too costly to compete with other sources of oil. However, according to the U.S. Geological Survey, in terms of water withdrawal, thermoelectric power was the largest source of water withdrawals (49 percent) in 2005, followed by irrigation at 31 percent. Water withdrawal refers to water removed from the ground or diverted from a surface water source, such as an ocean, river, or lake.
A recent World Bank report stated that water will become the natural resource most likely to cause armed conflict in the 21st century. Continual water shortages affect some 40 per cent of the world's population in 80 countries and, given the rapid expansion of the population and ever-increasing demand for water, the situation is expected to deteriorate further. Whereas shortage of land once stood out as the main constraint on food production in the developing world, it is now water scarcity that will constitute the major challenge. Global demand for water is currently increasing at 2.3 per cent a year, doubling every 21 years, and supply can no longer keep up with the growth rate.
Sadly, just like climate change issues, political systems our not suited to resolve these problems until they are in crises mode. Sadly, we are beginning to enter the crises mode.
Some very insightful comments have been made.
Herein lies the challenge: water use for wet cooling constitutes the greatest use of water in power generation. While most new power plants use recirculating cooling systems (see EIA's data), retrofitting existing steam-electric power plants with recirculating systems is difficult, expensive and impossible in some locations. This issue has been studied at length by the Electric Power Research Institute (EPRI). Dry cooling is only feasible where the heat load is relatively low or the ambient temperature is sufficiently low. Rarely can it be used on boiler-based units in hot climates. Besides solar and wind, natural gas reciprocating engine power plants use very little to no water and are being built in hot, arid climates where water resources are scarce. In these cases, a requirement of the bid (plant design and operation) is very low water use.
How that is accomplished in the U.S. speaks directly to Lisa's comment, which is very pertinent: how is water use and energy planning coordinated among the various federal agencies? I believe DOE's role is to 1) identify the issues with reducing water use for energy (and vice versa); 2) develop research priorities for reducing water use and 3) make policy recommendations for including water use as a constraint for energy production. Henry's suggestion that modeling accounts for water use is an excellent idea for planning purposes (modeling is usually restricted to electric transmission constraints). That could be an extremely helpful tool for planning capacity additions and unit retirements.
Over time through retirement of older once-through cooled units and greater deployment of renewables and distributed resources, the energy system will decrease water use. States with water scarcity where droughts have threatened electric power supply (California a good recent example) must look at water use in their permitting process and could codify that into state statutes. In this regard, I see states as having primacy in leading the push for lowering water use.
A key element to an integrated policy approach for energy and water will be equal effort to develop – or promote – integrated regulation that can help balance the tradeoffs inherent in trying to achieve multi-sector goals. This will also require an overhaul of regulatory approaches and frameworks that are aligned with forward-looking policy goals that assume interconnectedness instead of existing separated approaches that keep regulators (and by extension, service providers) straight-jacketed in trying to meet antiquated metrics and standards. For example, regulation can help focus on simultaneous standards of efficiency and intensity by setting strict metrics on something like non-revenue water, which would help with conservation efforts while also reducing the level of energy needed for systems pumps, etc. While this is developed, solutions like the ones already discussed here – vigorous pursuit of renewable energy at both the utility- and distributed-generation scale, streamlining and aligning various agencies and departments that fight for resources or carry out conflicting mandates, financially penalizing wasteful patterns – should be supported to help overcome inertia.
Another key element is educating consumers. Most likely see energy and water challenges as separate. Consumer-level technology can provide some inspiration. As "the internet of things" continues to develop, more and more consumers are receiving alerts, messages, data and other information about a host of things: their electricity consumption, their diet, their health, etc. In pursuing long-term goals, it will be important to find ways to get integrated information in front of stakeholders at all levels — consumers, building managers, city councils, state governments, — regarding metrics that show how much water was used to help provide the electricity they use and how much energy was used to provide the water they consumed. Provide benchmarks, help establish consumption reduction goals and keep them engaged in the process.


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