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/
>----------------------------------------------------------------------------------------------------------------------------------
> --
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/
>----------------------------------------------------------------------------------------------------------------------------------
>
>---
>
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