"that people wouldn't sacrifice for their strongly held beliefs?"
In an evolutionary context, why would people ever have beliefs strong enough they would die for them? Genes that contribute to such behavior should quickly vanish from the gene pool! But they clearly don't. The key to this is that the suicide bombers (or in times gone by tribal warriors) were not the only ones to carry the "die for the cause" genes. Their children did and if you work out the math, it turns out that genes for getting so wrapped up in a cause as to kill and be killed for it did better under reoccurring situations of ecological crisis than doing nothing. The main reason is that the young women who carried copies of the genes of defeated warriors were taken into the victorious tribe as wives and the warrior's genes marched on. Statistically, the effect was about 37% better survival for genes to get hyped up to kill neighbors--under some circumstances. If you work the model the other way, where circumstances did not favor this behavior, the bias was 45% against. So both the tendency to sacrifice and judging when it was effective were strongly selected over the past few million years.
It's weird, but it looks like both wars and religions (i.e., strongly held beliefs) are closely related and both stem from young women being booty in past human environment of evolutionary adaptedness.
I met Theremin about a year before he died. It was at Stanford, at an electronic music celebration for him. Just about all of the big names in electronic music were there. I went because my wife is a big fan of radical music.
Many years before that, my father had Theremin's spy gadget in his office in the Pentagon when he was chief of the scientific section of G2. It was dead simple, a resonate cavity with a diaphragm to pick up sound and modulate the outgoing signal.
The chronicler Robert the Monk put this into the mouth of Urban II:... this land which you inhabit, shut in on all sides by the seas and surrounded by the mountain peaks, is too narrow for your large population; nor does it abound in wealth; and it furnishes scarcely food enough for its cultivators. Hence it is that you murder one another, that you wage war, and that frequently you perish by mutual wounds. Let therefore hatred depart from among you, let your quarrels end, let wars cease, and let all dissensions and controversies slumber. Enter upon the road to the Holy Sepulchre; wrest that land from the wicked race, and subject it to yourselves... https://en.wikipedia.org/wiki/...
The problem is "large population" in relation to resources.
This is more or less standard human response far back into the stone age. You can always fix the problem of not enough resources by killing the neighbors, and humans are wired to respond that way when they sense things are getting tight.
If someone is using them to build power satellites, the fleet size is in the thousands. And they only fly perhaps a 1000 times before they have to be replaced.
Thanks for the compliment, AC. Perhaps I can do the same for you some day.
But let's analyze the case (if any) for power satellites. Electricity is a commodity; like all commodities you have to be competitive on price if you want a significant market share. That means you want to undercut electricity from coal at around 4 cents per kWh. If you set 75% of coal (3 cents per kWh) as the target, then you can back calculate how much you can spend for a levelized cost of electricity of three cents. For generally accepted life and discount rates that's about $2400/kW.
The mass for ground based solar power is around 500 kg/kW. This article, http://spacejournal.ohio.edu/i..., make a case for 6.5 kg/kW. Not having to support the collectors against gravity and wind, plus the near 24 hr sunlight cuts the mass to about 1%. Parts and the rectenna are currently estimated at around $1100/kW, leaving $1300/kW for transport cost. If we can't get the mass lower than 6.5 kg/kW, then the cost of lifting the power sats to GEO can't exceed $200/kg. At high flight rates, Reaction Engines thinks the cost will get to $120/kg. Electric propulsion from GEO to LEO powered by 25 GHz microwave beams in the hundreds of MW, looks like it will cost under $80/kg.
As important, Skylon is at 26 km, which is to say 96% or so of the atmosphere is below it. Also, you *start* with 150 untouched tons of LOX and enough hydrogen to burn all of it in about a 6 to one ratio. The 15 ton payload is only 5% of the 300 ton takeoff mass, but the design goal is to fly it every other day or perhaps every day with a low turn around cost. The heat exchangers are not that big a piece of the mass budget.
To solve the carbon/energy problem in 7 or 8 years would take a construction rate of 400 five GW power sats a year. This takes around a million Skylon flights. That's a reasonable number considering that we get a million commercial aircraft flights in ten days.
It's not even close to reasonable if you try to do it with rockets.
I have spent a lot of time with the spreadsheets that define a Skylon atmospheric ascent. It's not complicated at all. What they do is fly up the constant pressure line. By the time they switch to rocket mode, they are above atmosphere thick enough to cause Qmax problems. Forces on the vehicle are really mild.
I have followed Skylon for several years now. The engines are very interesting, in fact, the whole design, including the wings is very cool. The wings take the gravity load off, which for something that takes that long to get to orbit is quite an advantage.
They actually get more energy out of the hydrogen than they would get from just burning it. The reason is that they run the compressor on the temperature difference between ram air and the LH2 flowing to the engines. Burning hydrogen gives about 50 kWh/kg, it takes 20 kWh/kg to make it into a liquid.
You might note that everyone who has been given the full inside information, including the USAF, agrees that it will work as a SSTO. If anyone wants to build power satellites, Skylon is the only thing that is likely to get the cost to where power satellites could undercut coal.
I have been signed up with Alcor for 30 years. Was on the board of directors for several years and have known the major people for a long time. They now pay reasonable wages to the people who work there, but that's relatively new. In the long run, cryonics may not work, but the people who are involved are as sincere as you can find, with most of them being members as well.
Personally, I signed up after reviewing and commenting on several drafts of Eric Drexler's first work, _Engines of Creation_. It just seemed like a rational thing to do. Still does. Drexler is signed up, and so is Marvin Minsky and Ray Kurzweil plus a bunch of major players in Silicon Valley. Hal Finney was frozen a year ago. If it works, there will be some interesting company on the far end.
I have been a fan of Nuclear Thermal Rockets since before L5 Society. But good as they are, they don't give the exhaust velocity of electric rockets and you have to lug around the considerable mass of a reactor. For where you can reach with microwave power transmission beams, that seems to be a more cost effective solution. For way out where it's too dark for solar electric propulsion, they don't give as high an exhaust velocity as you really need for missions out there. After having done a lot of work with low mass condensing radiators for thermal power satellites, I think it might be more effective to make electric power from reactors and use that for arcjets.
Where a NTR would really shine is Earth to LEO, but the political problems of flying reactors are too much.
Depending on how you do it, the tug (small change) and a ground based power plant (big bucks) could run to $20 B or more. But that's not excessive considering it about doubles the fraction of cargo delivered to GEO by a $50 B fleet of Skylons. (100 or more at half a billion each.)
Almost all the dense space junk is below 2000 km, so you could deploy a power sat at that altitude and self power out to GEO. But if the power sat is not deployed, how do you power the arcjets from 300 km LEO out to 2000 km?
The secondary problems of a power sat being hit 40 times on the way out may be worst then the damage to the satellite because it makes a lot more space junk.
At the moment I am working through the numbers on a 400 MW power plant in space to take the place of the ground power plant. It may be less expensive and do the same job. But it has the same problem of getting hit below 2000 km. Current thought is to use chemical propulsion for a fast trip out to 2000 km, unfold there and self power to either GEO or half way to GEO. Lots of math.
If you know of a case which is convincing, please point me to it.
In simple terms, microwaves that will get through the atmosphere can't be focused tight enough to deliver the small blocks of power needed for military and niche markets. Lasers will deliver small blocks of power, but are blocked by clouds. The scale/frequency problem is in one of the graphs here:
It's called design to cost. If you can't get the parts cost plus the kg/kW times the $/kg down to $2400 or less, then the project doesn't happen because you don't get the market for it to make any sense. You just can't sell power for less than it cost to make it.
Lots of people have thought long and hard about military and other niche markets. The physics (and economics) is so against you that even the really smart guys have not figured out how to makehttp://interviews.slashdot.org/story/15/08/26/1644228/interviews-l5-society-cofounder-keith-henson-answers-your-questions# it work. If you can make a case for it, please do. You will be the first.
Indeed, a conventional upper stage increases the cost to GEO by a factor of at least 2.5 to one. That makes the power more expensive than coal and there goes the market.
The only reasonable thing I could figure out to hold down the amount of reaction mass is to use high exhaust velocity electric engines (20-25 km/s). Unfortunately you can't power them from sunlight or they take so long climbing through the space junk bands that the vehicle gets above 2000 km shot full of holes (average of 39 hits for something the size of a power satellite).
But electric rockets are power hogs, in the hundreds of MW at least, and you have to make them large for the same microwave optics physics that make power satellites so large. At least for space to space transmission you don't have to worry about the atmosphere or rain storms attenuating the beam.
Heard a rumor tonight about Donald Trump ranting that the US should claim the moon since we were there first. I suppose we could do that if we gave a year's notice on the 1987 Outer Space Treaty, but does he have any interest in space whatsoever? Seems really unlikely to me.
Musk, i.e., SpaceX is correct to be down on power satellites. His stated reason, low efficiency from sunlight to electric power is bogus though. Efficiency isn't a concern, cost is. Think about it. What would be lower efficiency than sunlight to hydro power? But hydro power is the cheapest kind of electricity we have.
Using what amounts to V2, or Saturn V technology (at the most), I think SpaceX will get a full ten to one reduction on the cost of cargo to GEO. But as I put in another post, that's not close to enough to undercut power from coal.
The other problem is that the peak construction rate is around two TW per year. We have to construct power satellites at that rate for 7 or 8 years to get off fossil fuels. With Skylon, it takes around a million flights per year. I can see that being possible after a considerable built up. Commercial airlines fly about 100,000 times a day, so a million flight is about ten days of airline flights.
I can't imagine the rocket traffic hauling that much cargo into space, though launching several huge rockets an hour would certainly be an awesome sight.
Earth is where the market for gold is so you have to bring it back if you want to sell it. Mind you, I don't think anyone will be mining asteroids for gold until second generation power satellites have been made with space mined nickel and iron for some time. But I think it can be done, profitably, with enough bootstrapping in space.
The precooler heat exchanger is the only unique part of Skylon engines, the rest is regular turbomachinery. It enable an engine cycle that produces thrust at far higher altitudes and velocity than anything we have known before and it does it on a remarkably small amount of light weight hydrogen.
The AFRL decided recently that the engine would work as advertized, Airbus wants to build the airframe.
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"that people wouldn't sacrifice for their strongly held beliefs?"
In an evolutionary context, why would people ever have beliefs strong enough they would die for them? Genes that contribute to such behavior should quickly vanish from the gene pool! But they clearly don't. The key to this is that the suicide bombers (or in times gone by tribal warriors) were not the only ones to carry the "die for the cause" genes. Their children did and if you work out the math, it turns out that genes for getting so wrapped up in a cause as to kill and be killed for it did better under reoccurring situations of ecological crisis than doing nothing. The main reason is that the young women who carried copies of the genes of defeated warriors were taken into the victorious tribe as wives and the warrior's genes marched on. Statistically, the effect was about 37% better survival for genes to get hyped up to kill neighbors--under some circumstances. If you work the model the other way, where circumstances did not favor this behavior, the bias was 45% against. So both the tendency to sacrifice and judging when it was effective were strongly selected over the past few million years.
It's weird, but it looks like both wars and religions (i.e., strongly held beliefs) are closely related and both stem from young women being booty in past human environment of evolutionary adaptedness.
I met Theremin about a year before he died. It was at Stanford, at an electronic music celebration for him. Just about all of the big names in electronic music were there. I went because my wife is a big fan of radical music.
Many years before that, my father had Theremin's spy gadget in his office in the Pentagon when he was chief of the scientific section of G2. It was dead simple, a resonate cavity with a diaphragm to pick up sound and modulate the outgoing signal.
Due to the efforts of the (long gone) L5 Society, the US never ratified the Moon Treaty . . . which is somewhat worse than the Outer Space Treaty.
I was personally involved.
That close.
The chronicler Robert the Monk put this into the mouth of Urban II: ... this land which you inhabit, shut in on all sides by the seas and surrounded by the mountain peaks, is too narrow for your large population; nor does it abound in wealth; and it furnishes scarcely food enough for its cultivators. Hence it is that you murder one another, that you wage war, and that frequently you perish by mutual wounds. Let therefore hatred depart from among you, let your quarrels end, let wars cease, and let all dissensions and controversies slumber. Enter upon the road to the Holy Sepulchre; wrest that land from the wicked race, and subject it to yourselves ... https://en.wikipedia.org/wiki/...
The problem is "large population" in relation to resources.
This is more or less standard human response far back into the stone age. You can always fix the problem of not enough resources by killing the neighbors, and humans are wired to respond that way when they sense things are getting tight.
If someone is using them to build power satellites, the fleet size is in the thousands. And they only fly perhaps a 1000 times before they have to be replaced.
Thanks for the compliment, AC. Perhaps I can do the same for you some day.
But let's analyze the case (if any) for power satellites. Electricity is a commodity; like all commodities you have to be competitive on price if you want a significant market share. That means you want to undercut electricity from coal at around 4 cents per kWh. If you set 75% of coal (3 cents per kWh) as the target, then you can back calculate how much you can spend for a levelized cost of electricity of three cents. For generally accepted life and discount rates that's about $2400/kW.
The mass for ground based solar power is around 500 kg/kW. This article, http://spacejournal.ohio.edu/i..., make a case for 6.5 kg/kW. Not having to support the collectors against gravity and wind, plus the near 24 hr sunlight cuts the mass to about 1%. Parts and the rectenna are currently estimated at around $1100/kW, leaving $1300/kW for transport cost. If we can't get the mass lower than 6.5 kg/kW, then the cost of lifting the power sats to GEO can't exceed $200/kg. At high flight rates, Reaction Engines thinks the cost will get to $120/kg. Electric propulsion from GEO to LEO powered by 25 GHz microwave beams in the hundreds of MW, looks like it will cost under $80/kg.
This article goes into the transport cost analysis. http://ieeexplore.ieee.org/xpl...
It was peer reviewed.
If you don't have easy library access, there is a preprint here:
https://drive.google.com/file/...
AC, if you would like to be anything but a blowhard, go through the documents and see if you can find fault with them.
"and just for mach 5 seems a heavy cost'
As important, Skylon is at 26 km, which is to say 96% or so of the atmosphere is below it. Also, you *start* with 150 untouched tons of LOX and enough hydrogen to burn all of it in about a 6 to one ratio. The 15 ton payload is only 5% of the 300 ton takeoff mass, but the design goal is to fly it every other day or perhaps every day with a low turn around cost. The heat exchangers are not that big a piece of the mass budget.
To solve the carbon/energy problem in 7 or 8 years would take a construction rate of 400 five GW power sats a year. This takes around a million Skylon flights. That's a reasonable number considering that we get a million commercial aircraft flights in ten days.
It's not even close to reasonable if you try to do it with rockets.
" Exactly how low is a messy calculus problem"
I have spent a lot of time with the spreadsheets that define a Skylon atmospheric ascent. It's not complicated at all. What they do is fly up the constant pressure line. By the time they switch to rocket mode, they are above atmosphere thick enough to cause Qmax problems. Forces on the vehicle are really mild.
Edge, you have done your homework.
I think it would be fun to talk. I am not hard to find. Or you can sign on to the google group power satellite economics where I hang out.
I have followed Skylon for several years now. The engines are very interesting, in fact, the whole design, including the wings is very cool. The wings take the gravity load off, which for something that takes that long to get to orbit is quite an advantage.
They actually get more energy out of the hydrogen than they would get from just burning it. The reason is that they run the compressor on the temperature difference between ram air and the LH2 flowing to the engines. Burning hydrogen gives about 50 kWh/kg, it takes 20 kWh/kg to make it into a liquid.
You might note that everyone who has been given the full inside information, including the USAF, agrees that it will work as a SSTO. If anyone wants to build power satellites, Skylon is the only thing that is likely to get the cost to where power satellites could undercut coal.
I wonder what you have done that compares with what Minsky and Kurzweil have accomplished?
I have been signed up with Alcor for 30 years. Was on the board of directors for several years and have known the major people for a long time. They now pay reasonable wages to the people who work there, but that's relatively new. In the long run, cryonics may not work, but the people who are involved are as sincere as you can find, with most of them being members as well.
Personally, I signed up after reviewing and commenting on several drafts of Eric Drexler's first work, _Engines of Creation_. It just seemed like a rational thing to do. Still does. Drexler is signed up, and so is Marvin Minsky and Ray Kurzweil plus a bunch of major players in Silicon Valley. Hal Finney was frozen a year ago. If it works, there will be some interesting company on the far end.
What we need is for someone to invent an energy source that is cheaper than coal and can scale to tens of TW (current use is around 15 TW).
Power satellites will certainly scale to that size, and at a high rate of production it looks like they could undercut coal.
But the powers that be have forgotten what engineers are good for.
I have been a fan of Nuclear Thermal Rockets since before L5 Society. But good as they are, they don't give the exhaust velocity of electric rockets and you have to lug around the considerable mass of a reactor. For where you can reach with microwave power transmission beams, that seems to be a more cost effective solution. For way out where it's too dark for solar electric propulsion, they don't give as high an exhaust velocity as you really need for missions out there. After having done a lot of work with low mass condensing radiators for thermal power satellites, I think it might be more effective to make electric power from reactors and use that for arcjets.
Where a NTR would really shine is Earth to LEO, but the political problems of flying reactors are too much.
Depending on how you do it, the tug (small change) and a ground based power plant (big bucks) could run to $20 B or more. But that's not excessive considering it about doubles the fraction of cargo delivered to GEO by a $50 B fleet of Skylons. (100 or more at half a billion each.)
Almost all the dense space junk is below 2000 km, so you could deploy a power sat at that altitude and self power out to GEO. But if the power sat is not deployed, how do you power the arcjets from 300 km LEO out to 2000 km?
The secondary problems of a power sat being hit 40 times on the way out may be worst then the damage to the satellite because it makes a lot more space junk.
At the moment I am working through the numbers on a 400 MW power plant in space to take the place of the ground power plant. It may be less expensive and do the same job. But it has the same problem of getting hit below 2000 km. Current thought is to use chemical propulsion for a fast trip out to 2000 km, unfold there and self power to either GEO or half way to GEO. Lots of math.
If you know of a case which is convincing, please point me to it.
In simple terms, microwaves that will get through the atmosphere can't be focused tight enough to deliver the small blocks of power needed for military and niche markets. Lasers will deliver small blocks of power, but are blocked by clouds. The scale/frequency problem is in one of the graphs here:
http://www.sspi.gatech.edu/aia...
$145,000/kW translates into $1.80 per kWh.
It's called design to cost. If you can't get the parts cost plus the kg/kW times the $/kg down to $2400 or less, then the project doesn't happen because you don't get the market for it to make any sense. You just can't sell power for less than it cost to make it.
Lots of people have thought long and hard about military and other niche markets. The physics (and economics) is so against you that even the really smart guys have not figured out how to makehttp://interviews.slashdot.org/story/15/08/26/1644228/interviews-l5-society-cofounder-keith-henson-answers-your-questions# it work. If you can make a case for it, please do. You will be the first.
" requiring a conventional upper stage for GEO "
Indeed, a conventional upper stage increases the cost to GEO by a factor of at least 2.5 to one. That makes the power more expensive than coal and there goes the market.
The only reasonable thing I could figure out to hold down the amount of reaction mass is to use high exhaust velocity electric engines (20-25 km/s). Unfortunately you can't power them from sunlight or they take so long climbing through the space junk bands that the vehicle gets above 2000 km shot full of holes (average of 39 hits for something the size of a power satellite).
But electric rockets are power hogs, in the hundreds of MW at least, and you have to make them large for the same microwave optics physics that make power satellites so large. At least for space to space transmission you don't have to worry about the atmosphere or rain storms attenuating the beam.
Heard a rumor tonight about Donald Trump ranting that the US should claim the moon since we were there first. I suppose we could do that if we gave a year's notice on the 1987 Outer Space Treaty, but does he have any interest in space whatsoever? Seems really unlikely to me.
Reaction Engines has some government support, but isn't part of the UK government.
I don't think you appreciate the technical aspects of the project. They are remarkable.
Musk, i.e., SpaceX is correct to be down on power satellites. His stated reason, low efficiency from sunlight to electric power is bogus though. Efficiency isn't a concern, cost is. Think about it. What would be lower efficiency than sunlight to hydro power? But hydro power is the cheapest kind of electricity we have.
Using what amounts to V2, or Saturn V technology (at the most), I think SpaceX will get a full ten to one reduction on the cost of cargo to GEO. But as I put in another post, that's not close to enough to undercut power from coal.
The other problem is that the peak construction rate is around two TW per year. We have to construct power satellites at that rate for 7 or 8 years to get off fossil fuels. With Skylon, it takes around a million flights per year. I can see that being possible after a considerable built up. Commercial airlines fly about 100,000 times a day, so a million flight is about ten days of airline flights.
I can't imagine the rocket traffic hauling that much cargo into space, though launching several huge rockets an hour would certainly be an awesome sight.
Earth is where the market for gold is so you have to bring it back if you want to sell it. Mind you, I don't think anyone will be mining asteroids for gold until second generation power satellites have been made with space mined nickel and iron for some time. But I think it can be done, profitably, with enough bootstrapping in space.
I don't think the US is likely to lead the power satellite project. To much cheap shale gas.
But if it was to be done, something like TVA would be the a good organizational model.
The precooler heat exchanger is the only unique part of Skylon engines, the rest is regular turbomachinery. It enable an engine cycle that produces thrust at far higher altitudes and velocity than anything we have known before and it does it on a remarkably small amount of light weight hydrogen.
The AFRL decided recently that the engine would work as advertized, Airbus wants to build the airframe.
http://www.reactionengines.co....
Skylon, or something with similar performance is the only way economical power satellites can be made (that I know about).
Senior Life member IEEE.