China's Space Program News Thread
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My Merriam-Webster app says "billow. verb. to rise or roll in waves or surges", which is rather close to what I meant. I should have explained my meaning precisely in anticipation of nitpickers like you, but as I said, I was in a hurry.
"Very close to being flat" is not perfectly flat. Unless your orbital mirror is improbably rigid (and massive) the radiation pressure of sunlight will distort it over time.
A solar power satellite's panel farm works even when it is not completely flat. A slightly distorted farm may not be optimally efficient, but we can compensate by making the farm larger. And we can eliminate distortions at our leisure by sending teleoperated robots to push whichever spots are out of true (with ion engines for example).
I think I have given good reason to think that SPSs will work, will be cheap, and could save our planet from global warming. In addition, a large collection of the satellites could potentially generate several times more energy than all of Earth is using now. The SPS idea (not original with me) is good.
Then refute my statements on their merits -- if you can. You have not been able to do so, which is why you have gone ad hominem, the last refuge of a bad loser.
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Which vehicle is this engine intended for?
It occurs to me that some people might be sceptical of my statement that solar power satellites (SPSs) could satisfy Earth's total energy needs many times over. Here's a quickie calculation that proves the possibility -- in principle. In practice of course, we would scale it way down, at least at first.
Imagine a band of solar panels completely encircling the Earth in geosynchronous orbit. The band is 10 km wide. This is a mind-bogglingly enormous structure of course. But we're just doing a back-of-the-envelope design, so bear with me.
The surface area of this band is easy to compute:
A = 2 * pi * r * w
where A is the surface area, pi is the mathematical constant, r is the radius, and w is the width of the band. Geosynchronous altitude is roughly 42,000 km from the center of the earth, so r = 42,000,000 m. Our imaginary band is 10 km wide, so w = 10,000 m.
Hence A = 2 * pi * 42e6 m * 10e3 m = 2.6e12 m^2.
Solar irradiance on Earth is roughly 1400 W/m^2. But our cheap solar panels (manufactured on the Moon) might have only 15% efficiency. Plus not all parts of the band will be facing the Sun at the same time; however, both sides of each panel would catch sunlight. As a rough guess, we can cut the average efficency in half again. So the power would be
P = (2.6e12 m^2) * (1400 W/m^2) * 0.15 * (1/2) = 277 terawatts.
Currently Earth is consuming 18 terawatts; this includes every source of energy like coal, oil, etc. So our orbiting solar power band would be producing 15 times more power than all of Earth is presently using.
We won't need this much power, not at first. So let's scale it down: let's cut the continuous band into 10 km x 10 km squares, and space them 60 km apart along the circumference of GEO. So only 1/7 of GEO's circumference would be occupied by solar panels. This scaled-down system would produce merely twice as much power as all of Earth is using now.
How many satellites would be necessary? This is easy too: the circumference of GEO divided by 10 km + 60 km = 70 km, or
2 * pi * (42,000 km) / (70 km) = 3800 satellites
This seems feasible.
A single orbiting 10 km x 10 km solar farm seems massive; wouldn't it block our view of the stars? No, not at all. At geosynchronous altitide (35,000 km), a farm 10 km wide would subtend
arctan(10/35000) = 0.016 degrees
The full Moon is half a degree wide. From the surface of the Earth, each solar farm would seem less than 1/60 as wide as the full Moon; if you looked up at night, these farms would form a dotted line of tiny shining pinpoints from horizon to horizon. The glare could upset some astronomers, but by the time we can build the SPSs, my hope is that the forefront of astronomy will have moved to giant telescopes in space, beyond the Moon (or on it).
Imagine a band of solar panels completely encircling the Earth in geosynchronous orbit. The band is 10 km wide. This is a mind-bogglingly enormous structure of course. But we're just doing a back-of-the-envelope design, so bear with me.
The surface area of this band is easy to compute:
A = 2 * pi * r * w
where A is the surface area, pi is the mathematical constant, r is the radius, and w is the width of the band. Geosynchronous altitude is roughly 42,000 km from the center of the earth, so r = 42,000,000 m. Our imaginary band is 10 km wide, so w = 10,000 m.
Hence A = 2 * pi * 42e6 m * 10e3 m = 2.6e12 m^2.
Solar irradiance on Earth is roughly 1400 W/m^2. But our cheap solar panels (manufactured on the Moon) might have only 15% efficiency. Plus not all parts of the band will be facing the Sun at the same time; however, both sides of each panel would catch sunlight. As a rough guess, we can cut the average efficency in half again. So the power would be
P = (2.6e12 m^2) * (1400 W/m^2) * 0.15 * (1/2) = 277 terawatts.
Currently Earth is consuming 18 terawatts; this includes every source of energy like coal, oil, etc. So our orbiting solar power band would be producing 15 times more power than all of Earth is presently using.
We won't need this much power, not at first. So let's scale it down: let's cut the continuous band into 10 km x 10 km squares, and space them 60 km apart along the circumference of GEO. So only 1/7 of GEO's circumference would be occupied by solar panels. This scaled-down system would produce merely twice as much power as all of Earth is using now.
How many satellites would be necessary? This is easy too: the circumference of GEO divided by 10 km + 60 km = 70 km, or
2 * pi * (42,000 km) / (70 km) = 3800 satellites
This seems feasible.
A single orbiting 10 km x 10 km solar farm seems massive; wouldn't it block our view of the stars? No, not at all. At geosynchronous altitide (35,000 km), a farm 10 km wide would subtend
arctan(10/35000) = 0.016 degrees
The full Moon is half a degree wide. From the surface of the Earth, each solar farm would seem less than 1/60 as wide as the full Moon; if you looked up at night, these farms would form a dotted line of tiny shining pinpoints from horizon to horizon. The glare could upset some astronomers, but by the time we can build the SPSs, my hope is that the forefront of astronomy will have moved to giant telescopes in space, beyond the Moon (or on it).
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A slightly revised comment. Bolded words have been added to reduce confusion...
It occurs to me that some people might be sceptical of my statement that solar power satellites (SPSs) could satisfy Earth's total energy needs many times over. Here's a quickie calculation that proves the possibility -- in principle. In practice of course, we would scale it way down, at least at first.
Imagine a band of solar panels completely encircling the Earth in geosynchronous orbit. The band is 10 km wide. This is a mind-bogglingly enormous structure of course. But we're just doing a back-of-the-envelope design, so bear with me.
The surface area of this band is easy to compute:
A = 2 * pi * r * w
where A is the surface area, pi is the mathematical constant, r is the radius, and w is the width of the band. Geosynchronous altitude is roughly 42,000 km from the center of the earth, so r = 42,000,000 m. Our imaginary band is 10 km wide, so w = 10,000 m.
Hence A = 2 * pi * 42e6 m * 10e3 m = 2.6e12 m^2.
Solar irradiance on Earth is roughly 1400 W/m^2. But our cheap solar panels (manufactured on the Moon) might have only 15% efficiency. Plus not all parts of the band will be facing the Sun squarely at the same time; however, both sides of each panel would have the ability to catch whatever sunlight is shining on it. As a rough guess, we need to cut the average efficency in half again. So the power would be
P = (2.6e12 m^2) * (1400 W/m^2) * 0.15 * (1/2) = 277 terawatts.
Currently Earth is consuming 18 terawatts; this includes every source of energy like coal, oil, etc. So our orbiting solar power band would be producing 15 times more power than all of Earth is presently using.
We won't need this much power, not at first. So let's scale it down: let's cut the continuous band into 10 km x 10 km squares, and space them 60 km apart along the circumference of GEO. So only 1/7 of GEO's circumference would be occupied by solar panels. This scaled-down system would produce merely twice as much power as all of Earth is using now.
How many satellites would be necessary? This is easy too: the circumference of GEO divided by 10 km + 60 km = 70 km, or
2 * pi * (42,000 km) / (70 km) = 3800 satellites
This seems feasible.
A single orbiting 10 km x 10 km solar farm seems massive; wouldn't it block our view of the stars? No, not at all. At geosynchronous altitide (35,000 km), a farm 10 km wide would subtend
arctan(10/35000) = 0.016 degrees
As seen from Earth, the full Moon is half a degree wide. From the surface of the Earth, each solar farm would seem less than 1/60 as wide as the full Moon; if you looked up at night, these farms would form a dotted line of tiny shining pinpoints from horizon to horizon. The glare could upset some astronomers, but by the time we can build the SPSs, my hope is that the forefront of astronomy will have moved to giant telescopes in space, beyond the Moon (or on it).
It occurs to me that some people might be sceptical of my statement that solar power satellites (SPSs) could satisfy Earth's total energy needs many times over. Here's a quickie calculation that proves the possibility -- in principle. In practice of course, we would scale it way down, at least at first.
Imagine a band of solar panels completely encircling the Earth in geosynchronous orbit. The band is 10 km wide. This is a mind-bogglingly enormous structure of course. But we're just doing a back-of-the-envelope design, so bear with me.
The surface area of this band is easy to compute:
A = 2 * pi * r * w
where A is the surface area, pi is the mathematical constant, r is the radius, and w is the width of the band. Geosynchronous altitude is roughly 42,000 km from the center of the earth, so r = 42,000,000 m. Our imaginary band is 10 km wide, so w = 10,000 m.
Hence A = 2 * pi * 42e6 m * 10e3 m = 2.6e12 m^2.
Solar irradiance on Earth is roughly 1400 W/m^2. But our cheap solar panels (manufactured on the Moon) might have only 15% efficiency. Plus not all parts of the band will be facing the Sun squarely at the same time; however, both sides of each panel would have the ability to catch whatever sunlight is shining on it. As a rough guess, we need to cut the average efficency in half again. So the power would be
P = (2.6e12 m^2) * (1400 W/m^2) * 0.15 * (1/2) = 277 terawatts.
Currently Earth is consuming 18 terawatts; this includes every source of energy like coal, oil, etc. So our orbiting solar power band would be producing 15 times more power than all of Earth is presently using.
We won't need this much power, not at first. So let's scale it down: let's cut the continuous band into 10 km x 10 km squares, and space them 60 km apart along the circumference of GEO. So only 1/7 of GEO's circumference would be occupied by solar panels. This scaled-down system would produce merely twice as much power as all of Earth is using now.
How many satellites would be necessary? This is easy too: the circumference of GEO divided by 10 km + 60 km = 70 km, or
2 * pi * (42,000 km) / (70 km) = 3800 satellites
This seems feasible.
A single orbiting 10 km x 10 km solar farm seems massive; wouldn't it block our view of the stars? No, not at all. At geosynchronous altitide (35,000 km), a farm 10 km wide would subtend
arctan(10/35000) = 0.016 degrees
As seen from Earth, the full Moon is half a degree wide. From the surface of the Earth, each solar farm would seem less than 1/60 as wide as the full Moon; if you looked up at night, these farms would form a dotted line of tiny shining pinpoints from horizon to horizon. The glare could upset some astronomers, but by the time we can build the SPSs, my hope is that the forefront of astronomy will have moved to giant telescopes in space, beyond the Moon (or on it).
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Me checking out moon rock sample from the ChangE 5 mission...
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