Close Sun-orbiting mirrors for beamed propulsion and space solar power.

[Robert Clark]

NASA just announced a solar probe to travel quite close to the Sun, about
3.7 million miles from the solar surface:

Nasa’s hotly anticipated solar mission renamed to honour astrophysicist
Eugene Parker.
Renamed the Parker Solar Probe to honour solar astrophysicist who predicted
high speed solar wind, the spacecraft will attempt to get close to sun’s
surface.
Wednesday 31 May 2017 07.08 EDT
https://www.theguardian.com/science/2017/may/31/nasa-to-announce-details-of-hotly-anticipated-mission-to-the-sun-solar-probe-plus

Spacecraft able to get this close to the Sun could potentially allow beamed
interstellar propulsion. For a spacecraft of any size, you would need huge
amounts of beamed power. Where to get it? If you make the beam be
solar-powered then can just use space-borne mirrors to focus the Suns rays.
But the mirror(s) would have to be impractically large if they were in Earth
orbit.

But what if we placed them close to the Sun? At the distance quoted of 3.7
million miles away from the Sun a mirror 1 km on a side could collect a
terawatt worth of power.

Note this could also be used for space solar power when beamed towards
Earth.

Bob Clark

----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Phil Hobbs]

Post by Robert Clark
NASA just announced a solar probe to travel quite close to the Sun,
Nasa’s hotly anticipated solar mission renamed to honour astrophysicist
Eugene Parker.
Renamed the Parker Solar Probe to honour solar astrophysicist who
predicted high speed solar wind, the spacecraft will attempt to get
close to sun’s surface.
Wednesday 31 May 2017 07.08 EDT
https://www.theguardian.com/science/2017/may/31/nasa-to-announce-details-of-hotly-anticipated-mission-to-the-sun-solar-probe-plus
Spacecraft able to get this close to the Sun could potentially allow
beamed interstellar propulsion. For a spacecraft of any size, you would
need huge amounts of beamed power. Where to get it? If you make the beam
be solar-powered then can just use space-borne mirrors to focus the Suns
rays. But the mirror(s) would have to be impractically large if they
were in Earth orbit.
But what if we placed them close to the Sun? At the distance quoted of
3.7 million miles away from the Sun a mirror 1 km on a side could
collect a terawatt worth of power.
Note this could also be used for space solar power when beamed towards
Earth.
Bob Clark

Gee, what could go wrong?

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

[Robert Clark]

"Robert Clark" wrote in message news:ogpm91$ob6$***@dont-email.me...
=================================================================
NASA just announced a solar probe to travel quite close to the Sun, about
3.7 million miles from the solar surface:

Nasa’s hotly anticipated solar mission renamed to honour astrophysicist
Eugene Parker.
Renamed the Parker Solar Probe to honour solar astrophysicist who predicted
high speed solar wind, the spacecraft will attempt to get close to sun’s
surface.
Wednesday 31 May 2017 07.08 EDT
https://www.theguardian.com/science/2017/may/31/nasa-to-announce-details-of-hotly-anticipated-mission-to-the-sun-solar-probe-plus

Spacecraft able to get this close to the Sun could potentially allow beamed
interstellar propulsion. For a spacecraft of any size, you would need huge
amounts of beamed power. Where to get it? If you make the beam be
solar-powered then can just use space-borne mirrors to focus the Suns rays.
But the mirror(s) would have to be impractically large if they were in Earth
orbit.

But what if we placed them close to the Sun? At the distance quoted of 3.7
million miles away from the Sun a mirror 1 km on a side could collect a
terawatt worth of power.

Note this could also be used for space solar power when beamed towards
Earth.
=================================================================

What would be the size of the collector array at Earth to capture most of
the light focused from the 1 km wide mirror located at the Sun, i.e., the
size of the Airy disk at the Earth? How large at Proxima Centauri?

Bob Clark


----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Niels Jørgen Kruse]

Post by Robert Clark
What would be the size of the collector array at Earth to capture most of
the light focused from the 1 km wide mirror located at the Sun, i.e., the
size of the Airy disk at the Earth? How large at Proxima Centauri?

The sun is not a point source, which means you can't focus it at any
significant distance.

[Robert Clark]

"0something0" wrote in message news:bb72a40c-398a-4c89-8c47-***@googlegroups.com...
====================================================================
Its also going to need to have YUUGE radiators and be able to operate at
high temperatures. The radiator needs to stay inside the shadow of the solar
array, which will limit how big it can be.

Assuming that in that distance, you get 55800 watts/square meter(from a
figure on Wikipedia and Space.com), and we use the equation

A = P / (ε * σ * T^4)

From Here: http://www.projectrho.com/public_html/rocket/basicdesign.php

Few assumptions: We use the alloy with the highest known melting point with
a max emissivity. That is 4488 degrees kelvin. We also assume a 1km^2 square
array. So, it collects 44,800,000,000 watts, or 44 gigawatts of heat. So,
the equation substituted is

A = 44,800,000,000 watts/(1*5.670367(13)*10^−8*W* 1 m^−2*1 K^−4*4488 k) =

https://www.wolframalpha.com/input/?i=Stefan-Boltzmann+law&rawformassumption=%7B%22FS%22%7D+-%3E+%7B%7B%22StefanBoltzmannLaw%22,+%22eps%22%7D%7D&rawformassumption=%7B%22F%22,+%22StefanBoltzmannLaw%22,+%22Phi%22%7D+-%3E%2244,800,000,000+W%2Fkm%5E2%22&rawformassumption=%7B%22F%22,+%22StefanBoltzmannLaw%22,+%22T%22%7D+-%3E%224488.15+K%22

Umm... did I do it right? If I did, Its not that bad!
====================================================================

What's the area you conclude is required for the radiators?

In any case, what you want is most of the power to be reflected away by the
mirrors.

BTW, I estimate the power per square meter is 862,000 watts/square meter
based on the fact the light power goes inversely by the square of the
distance and 3.7 million miles is 25 times closer than the Earth's distance
of 93 million miles.

Bob Clark

----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Robert Clark]

"Robert Clark" wrote in message news:ogpm91$ob6$***@dont-email.me...
=======================================================================
NASA just announced a solar probe to travel quite close to the Sun, about
3.7 million miles from the solar surface:

Nasa’s hotly anticipated solar mission renamed to honour astrophysicist
Eugene Parker.
Renamed the Parker Solar Probe to honour solar astrophysicist who predicted
high speed solar wind, the spacecraft will attempt to get close to sun’s
surface.
Wednesday 31 May 2017 07.08 EDT
https://www.theguardian.com/science/2017/may/31/nasa-to-announce-details-of-hotly-anticipated-mission-to-the-sun-solar-probe-plus

Spacecraft able to get this close to the Sun could potentially allow beamed
interstellar propulsion. For a spacecraft of any size, you would need huge
amounts of beamed power. Where to get it? If you make the beam be
solar-powered then can just use space-borne mirrors to focus the Suns rays.
But the mirror(s) would have to be impractically large if they were in Earth
orbit.

But what if we placed them close to the Sun? At the distance quoted of 3.7
million miles away from the Sun a mirror 1 km on a side could collect a
terawatt worth of power.

Note this could also be used for space solar power when beamed towards
Earth.

Bob Clark

---
=======================================================================

At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.

But could we put the mirror actually on the surface of the Sun? The Sun puts
out 3.86X10^26 watts of power,
http://m.wolframalpha.com/input/?i=solar+luminosity&x=0&y=0.

Given its 700,000 km radius, this amounts to over 60 terawatts per sq. km.
This is 3 times the total energy usage of humans on Earth from all sources.

Could we have a station on the Sun’s surface that would persist long term?
The Sun’s surface is at about 5,500 C. The highest temperature ceramic we
have is at about 4,000 C:

Rediscovered ceramic Hafnium Carbide can withstand temperatures three times
hotter than lava at 4050 celsius and could help enable hypersonic planes.
brian wang | September 17, 2014
https://www.nextbigfuture.com/2014/09/rediscovered-ceramic-hafnium-carbine.html

However, there are cases such as with rocket engine combustion chambers
where the operating temperature is well above the melting point of the
material composing the engine. The reason this is possible is that in order
for a material to undergo a phase change from solid to liquid not only does
it have to be at the melting point but a sufficient quantity of heat known
as the heat of fusion has to be supplied to it.

So with high performance rocket engines such as the SSME’s a cooling
techniques known as regenerative cooling is used that circulates cool fuel
around the engine to draw off adequate heat to prevent melting from
occurring.

However, with rocket engines this cooling fuel is burned or dispensed with
after being used for the cooling. So this wouldn’t work for a power station
existing long term on the surface of the Sun. You would need something like
a refrigeration system.

The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

Still, we might not want the extra difficulty of landing on the Sun. If we
make the distance to the Sun of our beaming station about 1/3rd that of the
Parker probe we would be at 10 terawatts per sq. km. Two of these would
provide the entire energy requirements for the entire human population, and
the surrounding temperatures wouldn’t be so extreme.

Bob Clark


----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Sегgi о]

Post by Robert Clark
The Parker probe will use a refrigeration system to lower the
temperature of the components of the spacecraft from 1,400 C to room
temperature. This is about the same temperature drop as the temperature
drop from the Sun’s surface to the maximum temperature of our high
temperature ceramics. So it should be possible to do this temperature
drop on the surface of the Sun using our highest temperature ceramics.

the major constraint is; the limited amount of heat can the probe get
rid of by radiate it out into cold space on the back side. This is only
a few hundred watts. (do the calculation)
[hint http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html ]

this means the solar shield *must be* a wideband optical and heat reflector

[Phil Hobbs]

Post by Sегgi о

Post by Robert Clark
The Parker probe will use a refrigeration system to lower the
temperature of the components of the spacecraft from 1,400 C to room
temperature. This is about the same temperature drop as the
temperature drop from the Sun’s surface to the maximum temperature of
our high temperature ceramics. So it should be possible to do this
temperature drop on the surface of the Sun using our highest
temperature ceramics.

the major constraint is; the limited amount of heat can the probe get
rid of by radiate it out into cold space on the back side. This is only
a few hundred watts. (do the calculation)
[hint http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html ]
this means the solar shield *must be* a wideband optical and heat reflector

And of course that the Sun does not have a solid surface.

Of course you could visit it at night. ;)


Cheers

Phil Hobbs

[Sегgi о]

Post by Phil Hobbs

Post by Sегgi о

Post by Robert Clark
The Parker probe will use a refrigeration system to lower the
temperature of the components of the spacecraft from 1,400 C to room
temperature. This is about the same temperature drop as the
temperature drop from the Sun’s surface to the maximum temperature of
our high temperature ceramics. So it should be possible to do this
temperature drop on the surface of the Sun using our highest
temperature ceramics.

the major constraint is; the limited amount of heat can the probe get
rid of by radiate it out into cold space on the back side. This is only
a few hundred watts. (do the calculation)
[hint http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html ]
this means the solar shield *must be* a wideband optical and heat reflector

And of course that the Sun does not have a solid surface.
Of course you could visit it at night. ;)
Cheers
Phil Hobbs

another problem, intense gamma radiation from the sun, that will screw
up computers,

Earth atmosphere stops much of it here, the equivelent of 12 feet of
Aluimium, at Earths distance, 90,000,000 miles.

Parker is going to 3,700,000 and would need 50 feet of Alu or more for a
shield ? [1/r^2]

[g***@gmail.com]

Post by Phil Hobbs

Post by Sегgi о

Post by Robert Clark
The Parker probe will use a refrigeration system to lower the
temperature of the components of the spacecraft from 1,400 C to room
temperature. This is about the same temperature drop as the
temperature drop from the Sun’s surface to the maximum temperature of
our high temperature ceramics. So it should be possible to do this
temperature drop on the surface of the Sun using our highest
temperature ceramics.

the major constraint is; the limited amount of heat can the probe get
rid of by radiate it out into cold space on the back side. This is only
a few hundred watts. (do the calculation)
[hint http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html ]
this means the solar shield *must be* a wideband optical and heat reflector

And of course that the Sun does not have a solid surface.
Of course you could visit it at night. ;)
Cheers
Phil Hobbs

Did you ever read the sci-fi novel "Sundiver" by D. Brin?
A refrigerator, runs a laser (High power!) that dumps the heat
into the sun.. or into space.

George H.

[Phil Hobbs]

Post by g***@gmail.com

Post by Phil Hobbs

Post by Sегgi о

Post by Robert Clark
The Parker probe will use a refrigeration system to lower the
temperature of the components of the spacecraft from 1,400 C to room
temperature. This is about the same temperature drop as the
temperature drop from the Sun’s surface to the maximum temperature of
our high temperature ceramics. So it should be possible to do this
temperature drop on the surface of the Sun using our highest
temperature ceramics.

the major constraint is; the limited amount of heat can the probe get
rid of by radiate it out into cold space on the back side. This is only
a few hundred watts. (do the calculation)
[hint http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html ]
this means the solar shield *must be* a wideband optical and heat reflector

And of course that the Sun does not have a solid surface.
Of course you could visit it at night. ;)
Cheers
Phil Hobbs

Did you ever read the sci-fi novel "Sundiver" by D. Brin?
A refrigerator, runs a laser (High power!) that dumps the heat
into the sun.. or into space.
George H.

Long, long ago. I liked his "Startide Rising" better, iirc.
Water-filled spaceships crewed by dolphins, why not?

(I've hardly read any SF in 30 years, except the occasional Helliconia.)

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

[benj]

Post by Sегgi о

Post by Robert Clark
The Parker probe will use a refrigeration system to lower the
temperature of the components of the spacecraft from 1,400 C to room
temperature. This is about the same temperature drop as the
temperature drop from the Sun’s surface to the maximum temperature of
our high temperature ceramics. So it should be possible to do this
temperature drop on the surface of the Sun using our highest
temperature ceramics.

the major constraint is; the limited amount of heat can the probe get
rid of by radiate it out into cold space on the back side. This is only
a few hundred watts. (do the calculation)
[hint http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html ]
this means the solar shield *must be* a wideband optical and heat reflector

Don't you know that directing energy back into the sun could overload it
and cause it to explode? This is science.

[Robert Clark]

"Robert Clark" wrote in message news:oi3a88$nck$***@dont-email.me...
=======================================================================
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.

But could we put the mirror actually on the surface of the Sun? The Sun puts
out 3.86X10^26 watts of power,
http://m.wolframalpha.com/input/?i=solar+luminosity&x=0&y=0.

Given its 700,000 km radius, this amounts to over 60 terawatts per sq. km.
This is 3 times the total energy usage of humans on Earth from all sources.

Could we have a station on the Sun’s surface that would persist long term?
The Sun’s surface is at about 5,500 C. The highest temperature ceramic we
have is at about 4,000 C:

Rediscovered ceramic Hafnium Carbide can withstand temperatures three times
hotter than lava at 4050 celsius and could help enable hypersonic planes.
brian wang | September 17, 2014
https://www.nextbigfuture.com/2014/09/rediscovered-ceramic-hafnium-carbine.html

However, there are cases such as with rocket engine combustion chambers
where the operating temperature is well above the melting point of the
material composing the engine. The reason this is possible is that in order
for a material to undergo a phase change from solid to liquid not only does
it have to be at the melting point but a sufficient quantity of heat known
as the heat of fusion has to be supplied to it.

So with high performance rocket engines such as the SSME’s a cooling
techniques known as regenerative cooling is used that circulates cool fuel
around the engine to draw off adequate heat to prevent melting from
occurring.

However, with rocket engines this cooling fuel is burned or dispensed with
after being used for the cooling. So this wouldn’t work for a power station
existing long term on the surface of the Sun. You would need something like
a refrigeration system.

The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

Still, we might not want the extra difficulty of landing on the Sun. If we
make the distance to the Sun of our beaming station about 1/3rd that of the
Parker probe we would be at 10 terawatts per sq. km. Two of these would
provide the entire energy requirements for the entire human population, and
the surrounding temperatures wouldn’t be so extreme.

Bob Clark

---
=====================================================================

Just saw this mentioned in the comments to an article on the Parker Solar
Probe on Centauri-dreams.org:

April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

At a solar radius of 700,000 km away from the Sun, based on the light
intensity going inversely by the square of the distance, and with 1,360
watts per sq. meter (in space) at the Earth’s distance, or 1.36 gigawatts
per sq. km., I estimate this should give 60 terawatts per sq. km. at only a
solar radius away from the Sun.

But in the post above, I had estimated that fully *on* the Sun’s surface we
could collect 60 terawatts per sq. km. of power. Anyone have an explanation
of this discrepancy?

In any case if this research team succeeds in producing this ultra high
reflective, high temperature material, then a mirror smaller than a
kilometer across a solar radius away from the Sun could collect enough
energy for the total energy usage for the entire human population of the
Earth.

Also, interesting is 16 solar collectors a kilometer across could provide a
petawatt of power. But these are power levels long about dreamed in science
fiction for doing beamed propulsion of large-scale, *manned* spacecraft on
relativistic, interstellar flights.

Bob Clark


----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Sегgi о]

Post by Robert Clark
=======================================================================
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the
temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??

also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?

[Robert Clark]

"Sегgi о" wrote in message news:oibn46$tjp$***@gioia.aioe.org...
========================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??

also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?

---
========================================================================

Look at it in terms of how much needs to be radiated per unit area. This
research project expects to reflect 99.9% of the light energy away:

April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

At that distance, the solar radiance is 60 megawatts per square meter. So
1/1,000 of this would have to be radiated away, this is 60,000 watts. That
is not a lot over a square meter.

Bob Clark

----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[g***@gmail.com]

Post by Robert Clark
========================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??
also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?
---
========================================================================
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

Seems like a pipe dream to me. We pay decent money for mirrors with
~99.7% reflectance over some limited wavelength range.

George H.

Post by Robert Clark
At that distance, the solar radiance is 60 megawatts per square meter. So
1/1,000 of this would have to be radiated away, this is 60,000 watts. That
is not a lot over a square meter.
Bob Clark
----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Robert Clark]

wrote in message news:f79403db-6f34-4c6a-b04f-***@googlegroups.com...

=============================================================

Post by Robert Clark
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this
modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

Seems like a pipe dream to me. We pay decent money for mirrors with
~99.7% reflectance over some limited wavelength range.

George H.

---
=========================================================

A reflectivity of 99.7% is probably good enough for the purpose. But this
new research is to make it over the entire optical and infrared range.

For the existing materials with high reflectivity over limited wavelengths I
wonder if it would be possible to stack
them to get the high reflectivity over a larger wavelength range.

Also, instead of a high reflectivity mirror could we use a ultra low
absorption lens?

Bob Clark

----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Sегgi о]

Post by Robert Clark
=============================================================

Post by Robert Clark
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this
modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

Seems like a pipe dream to me. We pay decent money for mirrors with
~99.7% reflectance over some limited wavelength range.
George H.

wow much does that extra 0.2% actually help ? 99.9 - 99.7 and in what
bands ?

ionizing radiation is also a huge problem

[Sегgi о]

Post by Sегgi о

Post by Robert Clark
=============================================================

Post by Robert Clark
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]

Description

Post by Sегgi о

Post by Robert Clark

Post by Robert Clark
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this
modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

Seems like a pipe dream to me. We pay decent money for mirrors with
~99.7% reflectance over some limited wavelength range.
George H.

wow much does that extra 0.2% actually help ? 99.9 - 99.7 and in what
bands ?
ionizing radiation is also a huge problem

that extra 0.2% will not help.

[Andrew Swallow]

Post by Robert Clark

Post by Sегgi о

Post by Robert Clark
=============================================================

Post by Robert Clark
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]

Description

Post by Sегgi о

Post by Robert Clark

Post by Robert Clark
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this
modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

Seems like a pipe dream to me. We pay decent money for mirrors with
~99.7% reflectance over some limited wavelength range.
George H.

wow much does that extra 0.2% actually help ? 99.9 - 99.7 and in
what bands ?
ionizing radiation is also a huge problem

that extra 0.2% will not help.

This definitely sounds like a place where the 80:20 rule can be used. If
we want more energy it will probably be cheaper to build a second mirror.

If the mirror melts at 4000K put it in an orbit where it is heated to
3500K.

[Sегgi о]

Post by Andrew Swallow

Post by Robert Clark

Post by Sегgi о

Post by Robert Clark
=============================================================

Post by Robert Clark
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]

Description

Post by Sегgi о

Post by Robert Clark

Post by Robert Clark
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this
modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing

Seems like a pipe dream to me. We pay decent money for mirrors with
~99.7% reflectance over some limited wavelength range.
George H.

wow much does that extra 0.2% actually help ? 99.9 - 99.7 and in
what bands ?
ionizing radiation is also a huge problem

that extra 0.2% will not help.

This definitely sounds like a place where the 80:20 rule can be used. If
we want more energy it will probably be cheaper to build a second mirror.
If the mirror melts at 4000K put it in an orbit where it is heated to
3500K.

could have one main excellent mirror,
then after that a stack of 10 aluminized milar sheets of plastic, like
the space suits.

[JF Mezei]

newbie question:

If you require "mirrors" that reflect all that the sun is throwing at
the probe to prevent it from frying, how can sensors within the probe
look at the sun?

And if the goal is to filter out 99.9999% so that sensors within the
probe still have something to measure, can one really have truly neutral
filters that will apply the 99.9999% equally to every type of
wavelength, particle and whatever radiation the sun is throwing at it?

[Crowell, Jeff]

Post by Robert Clark
A reflectivity of 99.7% is probably good enough for the purpose. But
this new research is to make it over the entire optical and infrared range.
For the existing materials with high reflectivity over limited
wavelengths I wonder if it would be possible to stack
them to get the high reflectivity over a larger wavelength range.
Also, instead of a high reflectivity mirror could we use a ultra low
absorption lens?

Sundiver, anyone?

Jeff

[Fred J. McCall]

Post by Robert Clark
========================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??

He wasn't speculating, Bob. That is what the Parker Probe is going to
do.

Post by Robert Clark
also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?

If you don't know the gamma ray levels, how can you say gamma will
cook it?

The gamma ray flux outside the surface of the Sun is essentially zero.
It all gets converted to visible photons from 170,000 years of
collisions inside the Sun on its way to the surface.

[Sегgi о]

Post by Fred J. McCall

Post by Robert Clark
========================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??

He wasn't speculating, Bob. That is what the Parker Probe is going to
do.

Post by Robert Clark
also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?

If you don't know the gamma ray levels, how can you say gamma will
cook it?
The gamma ray flux outside the surface of the Sun is essentially zero.
It all gets converted to visible photons from 170,000 years of
collisions inside the Sun on its way to the surface.

that wiki is out of context.
it seems zero if you compare it to levels within the sun.

another radiation issue - our south atlantic anomoly cooks electronics
in low orbit sattilites, (earth), an area of trapped radioactive
particals from the sun.

It would be nice if NASA would publish the engeneering aspects of this
and the sun probe, very interesting areas

[Fred J. McCall]

Post by Sегgi о

Post by Fred J. McCall

Post by Robert Clark
========================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??

He wasn't speculating, Bob. That is what the Parker Probe is going to
do.

Post by Robert Clark
also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?

If you don't know the gamma ray levels, how can you say gamma will
cook it?
The gamma ray flux outside the surface of the Sun is essentially zero.
It all gets converted to visible photons from 170,000 years of
collisions inside the Sun on its way to the surface.

that wiki is out of context.
it seems zero if you compare it to levels within the sun.

Zero. Remember, we're just talking gamma here.

Post by Sегgi о
another radiation issue - our south atlantic anomoly cooks electronics
in low orbit sattilites, (earth), an area of trapped radioactive
particals from the sun.

Not gamma.

[Sегgi о]

Post by Robert Clark
========================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the
temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??
also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?
========================================================================
Look at it in terms of how much needs to be radiated per unit area. This
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times better
than the current state-of-the-art. This will be accomplished by leveraging
off of our low temperature coating, currently being developed under NIAC
funding. We will modify our existing models to determine an optimal high
temperature solar reflector, predict its performance, and construct a
prototype version of this coating. This prototype will be sent to our
partner at the Johns Hopkins Applied Physics Laboratory where it will be
tested in an 11 times solar simulator. The results of this modeling/testing
will be used to design a mission to the Sun, where we hope to come to within
one solar radius of the Sun’s surface, 8 times closer than the closest
distance planned for the upcoming Solar Probe Plus. This project will
substantially advance the current capabilities of solar thermal protection
systems, not only potentially allowing “Solar Surfing”, but allowing better
thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing
At that distance, the solar radiance is 60 megawatts per square meter.
So 1/1,000 of this would have to be radiated away, this is 60,000 watts.
That is not a lot over a square meter.

I think you can figure out the temperature rise from that, 60,000 watts
out of a sq meter (too busy right now) to cold space, could be glowing red.

but that mirror is not real yet, 80 times is huge. and I think Gamma
rays will be a larger factor.

[Robert Clark]

"Sегgi о" wrote in message news:oibn46$tjp$***@gioia.aioe.org...
=======================================================================

Post by Robert Clark
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.

refrigeration wont work. if reflectivity is 99.9% you still ave to move
how many terrawatts(?) from front to back of the spacecraft, AND radiate
that out to cold space on the backside ??

also Gamma rays are going to cook it, +fry electonics.
what are the gamma ray radiation levels close to the sun ?

---
=======================================================================

This page describes the Parker Solar Probe's cooling system:

Cool Power
Posted on 06/21/2017 09:00:23
http://parkersolarprobe.jhuapl.edu/News-Center/Show-Article.php?articleID=30

Also, I've found NASA scientists are very helpful in responding to questions
from the public if you have more questions on the topic. Contact info for
the Parker Probe scientists is available here:

May 26, 2017
MEDIA ADVISORY M17-061
NASA to Make Announcement About First Mission to Touch Sun.
https://www.nasa.gov/press-release/nasa-to-make-announcement-about-first-mission-to-touch-sun


Bob Clark

----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Robert Clark]

"***@bid.nes" wrote in message news:c73990ab-7bef-4d14-b26c-***@googlegroups.com...

===================================================================

Post by Robert Clark
At a solar radius of 700,000 km away from the Sun, based on the light
intensity going inversely by the square of the distance, and with 1,360
watts per sq. meter (in space) at the Earth’s distance, or 1.36 gigawatts
per sq. km., I estimate this should give 60 terawatts per sq. km. at only a
solar radius away from the Sun.
But in the post above, I had estimated that fully *on* the Sun’s surface we
could collect 60 terawatts per sq. km. of power. Anyone have an explanation
of this discrepancy?

I'm not going to go through the math for you, but think about how much of
the Sun your hypothetical power-collector can "see" from a radius away as
opposed to "on the surface" (which I take to mean just above the
photosphere).

Also, how do you plan to keep it there? It can't orbit, and it can't
float. I'm pretty sure radiation/solar wind pressure won't cut it.

Post by Robert Clark
In any case if this research team succeeds in producing this ultra high
reflective, high temperature material, then a mirror smaller than a
kilometer across a solar radius away from the Sun could collect enough
energy for the total energy usage for the entire human population of the
Earth.

I still want to know how the refrigeration system is going to get rid of
the heat. At the photosphere's surface the radiator is going to "see" the
corona no matter how the photosphere is shaded from it.

At a radius out it will "see" much colder interplanetary space.

Mark L. Fergerson

---
===================================================================

The suggestion that close in to the surface at a solar radius away this will
limit the amount of the Sun's surface it can see is a good one. But if this
was the issue we would expect the solar radiance would be reduced even
further below what was available directly on the surface, not equal to it.

About the solar collector remaining on the surface, it may be that it's
unnecessary anyway if you can get the same amount of power a solar radius
away. But still there is solar outward gas pressure that might allow it to
float there especially for a large area, but lightweight, solar mirror.

The corona is quite hot at millions of degrees but is quite diffuse which
will limit the amount of heat it will transmit to spacecraft. Also since the
temperature of the corona is variable with altitude we might be able to
place it at an altitude to limit the heating.

Bob Clark


----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Robert Clark]

"Robert Clark" wrote in message news:oijgdb$alb$***@dont-email.me...
==================================================================
==================================================================
"***@bid.nes" wrote in message news:c73990ab-7bef-4d14-b26c-***@googlegroups.com...
==================================================================

Post by Robert Clark
At a solar radius of 700,000 km away from the Sun, based on the light
intensity going inversely by the square of the distance, and with 1,360
watts per sq. meter (in space) at the Earth’s distance, or 1.36 gigawatts
per sq. km., I estimate this should give 60 terawatts per sq. km. at only a
solar radius away from the Sun.
But in the post above, I had estimated that fully *on* the Sun’s surface we
could collect 60 terawatts per sq. km. of power. Anyone have an explanation
of this discrepancy?

I'm not going to go through the math for you, but think about how much of
the Sun your hypothetical power-collector can "see" from a radius away as
opposed to "on the surface" (which I take to mean just above the
photosphere).

...
Mark L. Fergerson

---
===================================================================

The suggestion that close in to the surface at a solar radius away this will
limit the amount of the Sun's surface it can see is a good one. But if this
was the issue we would expect the solar radiance would be reduced even
further below what was available directly on the surface, not equal to it.

---
=================================================================
=================================================================

OK. I think I understand your argument now:

From the Earth's distance the lightrays are nearly parallel and you receive
the light from the entire solar disk. But when you make a comparison to a
much closer distance by just increasing the solar radiance according to the
closer distance you are *assuming* the illumination will be to the same
extent at that distance. In actuality though, a significant portion of the
solar disk will not be observable. See the image here:

https://ibb.co/hionF5

That angle at center calculates to be 60° because its cosine is r/2r = 1/2.
So you see only 60°/90° = 2/3rds of the solar disk will be observable at
that distance.

I might estimate the radiance at that distance then as 40 terawatts instead
of 60 terawatts. However, because not all the rays are parallel at this
distance I'm not sure all portions of the Sun would make the same
contribution to the total so the answer might not be proportional.

Perhaps someone can calculate this.

Bob Clark



----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

[Robert Clark]

Post by Robert Clark
=======================================================================
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
But could we put the mirror actually on the surface of the Sun? The Sun puts
out 3.86X10^26 watts of power,
http://m.wolframalpha.com/input/?i=solar+luminosity&x=0&y=0.
Given its 700,000 km radius, this amounts to over 60 terawatts per sq. km.
This is 3 times the total energy usage of humans on Earth from all sources.
Could we have a station on the Sun’s surface that would persist long term?
The Sun’s surface is at about 5,500 C. The highest temperature ceramic we
Rediscovered ceramic Hafnium Carbide can withstand temperatures three times
hotter than lava at 4050 celsius and could help enable hypersonic planes.
brian wang | September 17, 2014
https://www.nextbigfuture.com/2014/09/rediscovered-ceramic-hafnium-carbine.html
However, there are cases such as with rocket engine combustion chambers
where the operating temperature is well above the melting point of the
material composing the engine. The reason this is possible is that in order
for a material to undergo a phase change from solid to liquid not only does
it have to be at the melting point but a sufficient quantity of heat known
as the heat of fusion has to be supplied to it.
So with high performance rocket engines such as the SSME’s a cooling
techniques known as regenerative cooling is used that circulates cool fuel
around the engine to draw off adequate heat to prevent melting from
occurring.
However, with rocket engines this cooling fuel is burned or dispensed with
after being used for the cooling. So this wouldn’t work for a power station
existing long term on the surface of the Sun. You would need something like
a refrigeration system.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.
Still, we might not want the extra difficulty of landing on the Sun. If we
make the distance to the Sun of our beaming station about 1/3rd that of the
Parker probe we would be at 10 terawatts per sq. km. Two of these would
provide the entire energy requirements for the entire human population, and
the surrounding temperatures wouldn’t be so extreme.
Bob Clark
---
=====================================================================
Just saw this mentioned in the comments to an article on the Parker Solar
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times
better than the current state-of-the-art. This will be accomplished by
leveraging off of our low temperature coating, currently being developed
under NIAC funding. We will modify our existing models to determine an
optimal high temperature solar reflector, predict its performance, and
construct a prototype version of this coating. This prototype will be sent
to our partner at the Johns Hopkins Applied Physics Laboratory where it
will be tested in an 11 times solar simulator. The results of this
modeling/testing will be used to design a mission to the Sun, where we hope
to come to within one solar radius of the Sun’s surface, 8 times closer
than the closest distance planned for the upcoming Solar Probe Plus. This
project will substantially advance the current capabilities of solar
thermal protection systems, not only potentially allowing “Solar Surfing”,
but allowing better thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing
At a solar radius of 700,000 km away from the Sun, based on the light
intensity going inversely by the square of the distance, and with 1,360
watts per sq. meter (in space) at the Earth’s distance, or 1.36 gigawatts
per sq. km., I estimate this should give 60 terawatts per sq. km. at only a
solar radius away from the Sun.
But in the post above, I had estimated that fully *on* the Sun’s surface
we could collect 60 terawatts per sq. km. of power. Anyone have an
explanation of this discrepancy?
In any case if this research team succeeds in producing this ultra high
reflective, high temperature material, then a mirror smaller than a
kilometer across a solar radius away from the Sun could collect enough
energy for the total energy usage for the entire human population of the
Earth.
Also, interesting is 16 solar collectors a kilometer across could provide a
petawatt of power. But these are power levels long about dreamed in science
fiction for doing beamed propulsion of large-scale, *manned* spacecraft on
relativistic, interstellar flights.
Bob Clark
----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

Ok. I looked up the method of calculating the solar radiance per unit area
according to distance. For the Earth's distance away from the Sun, it's
calculated by taking the total radiance of the Sun and dividing that by the
total surface area of a sphere at the Earth's distance away. The total solar
radiance is 3.86X10^26 watts. The distance of the Earth away is
150,000,000,000 meters. So the solar radiance per square meter at the
Earth's distance is 3.86x10^26/(4*Pi*150,000,000,000^2) = 1,365 watts per
sq. meter, matching the cited amount.

So for the proposed solar probe only 700,000 km away from the solar surface,
this is for a sphere of radius 1,400,000 km. And the solar radiance per
square kilometer there is: 3.86x10^26/(4*Pi*1,400,000^2) = 15.7 terawatts
per square km. This is close to the entire energy usage from all sources for
the entire human population of Earth.


Bob Clark
--

[Robert Clark]

Post by Robert Clark
=======================================================================
At the distance of the Parker probe, a 1 km sq. mirror could collect a
terawatt of power for beamed propulsion or space solar power beamed to
Earth.
But could we put the mirror actually on the surface of the Sun? The Sun puts
out 3.86X10^26 watts of power,
http://m.wolframalpha.com/input/?i=solar+luminosity&x=0&y=0.
Given its 700,000 km radius, this amounts to over 60 terawatts per sq. km.
This is 3 times the total energy usage of humans on Earth from all sources.
Could we have a station on the Sun’s surface that would persist long term?
The Sun’s surface is at about 5,500 C. The highest temperature ceramic we
Rediscovered ceramic Hafnium Carbide can withstand temperatures three times
hotter than lava at 4050 celsius and could help enable hypersonic planes.
brian wang | September 17, 2014
https://www.nextbigfuture.com/2014/09/rediscovered-ceramic-hafnium-carbine.html
However, there are cases such as with rocket engine combustion chambers
where the operating temperature is well above the melting point of the
material composing the engine. The reason this is possible is that in order
for a material to undergo a phase change from solid to liquid not only does
it have to be at the melting point but a sufficient quantity of heat known
as the heat of fusion has to be supplied to it.
So with high performance rocket engines such as the SSME’s a cooling
techniques known as regenerative cooling is used that circulates cool fuel
around the engine to draw off adequate heat to prevent melting from
occurring.
However, with rocket engines this cooling fuel is burned or dispensed with
after being used for the cooling. So this wouldn’t work for a power station
existing long term on the surface of the Sun. You would need something like
a refrigeration system.
The Parker probe will use a refrigeration system to lower the temperature of
the components of the spacecraft from 1,400 C to room temperature. This is
about the same temperature drop as the temperature drop from the Sun’s
surface to the maximum temperature of our high temperature ceramics. So it
should be possible to do this temperature drop on the surface of the Sun
using our highest temperature ceramics.
Still, we might not want the extra difficulty of landing on the Sun. If we
make the distance to the Sun of our beaming station about 1/3rd that of the
Parker probe we would be at 10 terawatts per sq. km. Two of these would
provide the entire energy requirements for the entire human population, and
the surrounding temperatures wouldn’t be so extreme.
---
=====================================================================
Just saw this mentioned in the comments to an article on the Parker Solar
April 6, 2017
Solar Surfing
Robert Youngquist
NASA Kennedy Space Center
[quote]
Description
We propose to develop a novel high temperature coating that will reflect up
to 99.9 % of the Sun’s total irradiance, roughly a factor of 80 times
better than the current state-of-the-art. This will be accomplished by
leveraging off of our low temperature coating, currently being developed
under NIAC funding. We will modify our existing models to determine an
optimal high temperature solar reflector, predict its performance, and
construct a prototype version of this coating. This prototype will be sent
to our partner at the Johns Hopkins Applied Physics Laboratory where it
will be tested in an 11 times solar simulator. The results of this
modeling/testing will be used to design a mission to the Sun, where we hope
to come to within one solar radius of the Sun’s surface, 8 times closer
than the closest distance planned for the upcoming Solar Probe Plus. This
project will substantially advance the current capabilities of solar
thermal protection systems, not only potentially allowing “Solar Surfing”,
but allowing better thermal control of a future mission to Mercury.[/quote]
https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Surfing
At a solar radius of 700,000 km away from the Sun, based on the light
intensity going inversely by the square of the distance, and with 1,360
watts per sq. meter (in space) at the Earth’s distance, or 1.36 gigawatts
per sq. km., I estimate this should give 60 terawatts per sq. km. at only a
solar radius away from the Sun.
But in the post above, I had estimated that fully *on* the Sun’s surface
we could collect 60 terawatts per sq. km. of power. Anyone have an
explanation of this discrepancy?
In any case if this research team succeeds in producing this ultra high
reflective, high temperature material, then a mirror smaller than a
kilometer across a solar radius away from the Sun could collect enough
energy for the total energy usage for the entire human population of the
Earth.
Also, interesting is 16 solar collectors a kilometer across could provide a
petawatt of power. But these are power levels long about dreamed in science
fiction for doing beamed propulsion of large-scale, *manned* spacecraft on
relativistic, interstellar flights.
----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------
---

It has been theorized planetary-scale lasers might be detectable at galactic
distances:

http://www.popularmechanics.com/space/a25609/fast-radio-bursts-alien-space-travel/

I wonder if the effects of lightsail propulsion through the interstellar
medium might be detectable in our own galaxy. A kilometer scale lightsail
moving at relativistic speeds should accelerate the interstellar plasma.
This should generate EM waves that might be detectable by us. This EM
radiation being detected away from a star system may make it identifiable.

Bob Clark

--

[Robert Clark]

NASA just announced a solar probe to travel quite close to the Sun, about

Post by Robert Clark
Nasa’s hotly anticipated solar mission renamed to honour astrophysicist
Eugene Parker.
Renamed the Parker Solar Probe to honour solar astrophysicist who predicted
high speed solar wind, the spacecraft will attempt to get close to sun’s
surface.
Wednesday 31 May 2017 07.08 EDT
https://www.theguardian.com/science/2017/may/31/nasa-to-announce-details-of-hotly-anticipated-mission-to-the-sun-solar-probe-plus
Spacecraft able to get this close to the Sun could potentially allow beamed
interstellar propulsion. For a spacecraft of any size, you would need huge
amounts of beamed power. Where to get it? If you make the beam be
solar-powered then can just use space-borne mirrors to focus the Suns rays.
But the mirror(s) would have to be impractically large if they were in
Earth orbit.
But what if we placed them close to the Sun? At the distance quoted of 3.7
million miles away from the Sun a mirror 1 km on a side could collect a
terawatt worth of power.
Note this could also be used for space solar power when beamed towards
Earth.
Bob Clark
----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------
--

NASA just announced a solar probe to travel quite close to the Sun, about

Post by Robert Clark
Nasa’s hotly anticipated solar mission renamed to honour astrophysicist
Eugene Parker.
Renamed the Parker Solar Probe to honour solar astrophysicist who predicted
high speed solar wind, the spacecraft will attempt to get close to sun’s
surface.
Wednesday 31 May 2017 07.08 EDT
https://www.theguardian.com/science/2017/may/31/nasa-to-announce-details-of-hotly-anticipated-mission-to-the-sun-solar-probe-plus
Spacecraft able to get this close to the Sun could potentially allow beamed
interstellar propulsion. For a spacecraft of any size, you would need huge
amounts of beamed power. Where to get it? If you make the beam be
solar-powered then can just use space-borne mirrors to focus the Suns rays.
But the mirror(s) would have to be impractically large if they were in
Earth orbit.
But what if we placed them close to the Sun? At the distance quoted of 3.7
million miles away from the Sun a mirror 1 km on a side could collect a
terawatt worth of power.
Note this could also be used for space solar power when beamed towards
Earth.
Bob Clark
----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
Nanotech: from air to space.
https://www.indiegogo.com/projects/nanotech-from-air-to-space/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------
---

For the mirror/lens at the Sun or the solar sail material I want to suggest
some adaptations of the transparent carbon nanotube sheets discussed here:

Saturday, April 19, 2014
Economical Space Solar Power Now Possible.
http://exoscientist.blogspot.com/2014/04/economical-space-solar-power-now_19.html

It refers to this research:

Researchers produce strong, transparent carbon nanotube sheets.
Aug 18, 2005
[quote]Strength normalized to weight is important for many applications,
especially in space and aerospace, and this property of the nanotube
sheets already exceeds that of the strongest steel sheets and the Mylar
and Kapton sheets used for ultralight air vehicles and proposed for
solar sails for space applications, according to the researchers. The
nanotube sheets can be made so thin that a square kilometer of solar
sail would weigh only 30 kilograms. While sheets normally have much
lower strength than fibers or yarns, the strength of the nanotube
sheets in the nanotube alignment direction already approaches the
highest reported values for polymer-free nanotube yarns. [/quote]
http://www.physorg.com/news5890.html

A 1 km square sail weighing only 30 kg, corresponds to 0.03 gm/sq.m. So for
the 4m x 4m sail discussed by the Starshot project, it would be a weight of
0.48 gm, which is likely sufficient for a 1 gm scale micro spacecraft.

However, these nanosheets are transparent. We could coat them with aluminum
but the 100 nm thick aluminum coating normally put on mirrors would make our
sail 4.4 gm. This would slow down our acceleration.

It would be cool if we could use or adapt the transparent nanotube sheets
themselves. One possibility is using the fact that nanotube's electronic
properties are highly tunable according to the arrangement of the carbon
atoms. See for instance:

https://en.wikipedia.org/wiki/Carbon_nanotube#Electrical

https://www.researchgate.net/publication/221922911_Carbon_Nanotube-_and_Graphene_Based_Devices_Circuits_and_Sensors_for_VLSI_Design/figures?lo=1

and:

Atomic structure and electronic properties of single-walled carbon
nanotubes.
Teri Wang Odom1, Jin-Lin Huang1, Philip Kim2 & Charles M. Lieber1,2
Nature 391, 62-64 (1 January 1998) | doi:10.1038/34145; Received 10 October
1997; Accepted 26 November 1997
http://www.nature.com/nature/journal/v391/n6662/full/391062a0.html

Then we might be able create lightweight sheets that are instead reflective
as a mirror.

Another possibility is that their electronic properties can also be changed
by doping. So we may thereby be able to make the sheets reflective.

A different possibility would use them in their transparent form. We would
shape the sheets so they act as a lens. Then the collecting area of the
sheet would focus the collected light down to a smaller mirror area, thus
having a smaller weight which would still have the effect of inducing an
acceleration on the spacecraft.

As for making such a large structure we might make it inflatable. For
instance Project Echo in the sixties used metalized balloons as satellites
40 meters across to bounce radio signals off of.

Bob Clark