Worlds for Man - Part 2 - Venus

"Worlds For Man - Part 2 - Venus"

(c) 2007, 2011 by Jordan S. Bassior

Venus is in many ways a disappointment. The cllosest separate planet to the Earth, with almost the size and mass of the Earth, with the gravity to retain a thick atmosphere, Venus should be a prime choice for colonization. But the planet's proximity to the Sun and lack of a moon, coupled with a denser crust and resultant feebler tectonic action, have caused her to suffer a runaway greenhouse effect (the atmosphere is mainly composed of carbon dioxide) that has resulted in surface temperatures averaging over 400 degrees Celsius -- hotter than Mercury, and owing to atmospheric convection experienced globally rather than merely on the dayside.  To put more simply, Venus is everywhere, at every latitude, even in the shade or underground, at temperatures sufficient to melt lead (1).


With such high temperatures, and a surface pressure of 90 atmospheres coupled with clouds of sulfuric acid vapor, Venus is an extraordinarily hostile environment. Even robot probes can only endure a matter of hours on the Venusian surface, and vehicles capable of protecting organic life forms from such conditions would have be extraordinarily well-armored and thus bulky. Any permanent habitations would require powerful heat pumps to maintain survivable conditions within for prolonged periods (vehicles could operate for shorter periods using heat sinks) (2). Thus, the colonization of the Venusian surface would be very expensive, dangerous (3) and difficult.

Near-Term,  there is fortunately another option. 50 km above the Venusian surface, the pressure and temperatures are Earth-like (1 atmosphere and 0-50 degrees Celsius). In addition, at this altitude solar energy is abundant -- 1.9 times per square meter the amount available on Earth. Consequently, the early colonization of Venus might involve the construction of blimp or dirigible-like floating stations ("aerostat habitats," in Geoffrey Landis' terms), in which the provision of life support would not be unusually difficult. From these stations, human crews could supervise robots and conduct excursions onto the surface. The stations might float freely, blown by the winds around the planet every 100 hours or less; or they might be tethered to the ground (4).

One thing that would ease their design is that ordinary Earth air (a 21:79 oxygen-nitrogen mix) is a lifting gas under Venusian atmospheric conditions -- consequently, the aerostats' gas bags could be used as combination air reservoirs and large common areas (5). Thus, life in such a hab might not be unduly claustrophic; provided that the total load was not increased too much the gas bags could be formed as parkland, complete with soil, plants, and water lakes whose aqueous contents could double as droppable ballast (6).

Ground stations might also exist, but would be used as bases for surface operations rather than long-term habs. The ground stations would be mostly robot-manned, and most actual scouting work would probably be done by fleets tele-operable semi-independent robot robers, with humans remaining within the safety of the thick-walled ground habs rather than risking their lives in bulky, probably mecha-like Venus Suits (7). Conditions within the ground stations would certainly be spartan and claustrophobic, especially during this early phase of colonization.

Venus offers some useful resources. The planet is probably metal rich, though not as much so as the Earth (8), and certainly contains volatiles, especially carbon, oxygen and nitrogen. Unlike most terrestrial worlds, it lacks ice, but with the available solar energy and hydrogen-containing minerals, enough water could be obtained for colonial purposes. Venus also has a moderate gravity which would be better for health purposes than the lower gravities obtaining on the other terrestrials. Unfortunately, none of these advantages are particularly dramatic (Venus is outcompeted by Mercury as a source of minerals and by Earth and Mars as a source of volatiles) and hence Venusian colonization will probably be a slow process (9).

Middle-term colonization will see this slow process yield significant growth. The aerostat habs will have grown into genuine "floating cities" (again using Landis' terms); on the surface, the ground stations will have time to grow into immense warrens.

Load will be a major problem in the floating cities: every effort will be made to build things out of light but strong substances, such as the nanoformed carbon-filament polymers which will be then be spinnable kilometers long (10). Here will live many humans and organic artificials, in a sort of floating fairyland.

Refrigeration will be the major problem on the ground: where ever possible labor will be done by inorganic artificals, so that as little space as possible needs to be conditioned to Earth norms. Thus the surface will be the realm of robots -- specifically, ones designed to survive Venusian temperatures and pressures.

By this time, the work of terraforming may have begun. The main problems are the heat, and the lack of water. The heat could be reduced by orbiting sunshields (which could double as solar power stations) (11), as proposed by Robert Zubrin. Water (on the scale needed to terraform a moderate-sized terrestrial planet) would be a more difficult problem: iceteroid bombardment would take a very long time to deliver enough to make a difference.

Paul Birch has suggested crashing one of Saturn's small ice moons onto Venus to deliver a lot of water at once: of course, if colonization has already begun, this would be a very dangerous technique. Perhaps an ice moon could be pushed into Venus orbit, behind a sunshield, and then the moon sliced up and dropped onto Venus in smaller, more manageable pieces?

Landis has pointed out that the floating cities could also serve as sunshields and atmosphere converters. While a single floating city would not be able to achieve much in this regard, as they spread (especially if linked by large areas of artifical floating "wilderness") a lot of floating cities could perform considerable terraforming over time.

Because of the division of Venus into two main environments -- the soaring sky-world and the sweltering surface -- there is an obvious social conflict likely to develop. Especially where terraforming issues are concerned, the interests of the organic sapients in the cloud-cities and the inorganic sapients in the surface-habs may not be compatible. Skydwelling humans, cosmopolitan in outlook, might take for granted that Venus would be improved by becoming more Earthlike; but robots already optimized to Venusian surface conditions may see no need to introduce corrosive free oxygen and salt water into their world.

Long-Term

In the end, Venus is likely to be terraformed, if only because by doing so the Venusians would be joining a community of Earth-like worlds in the Inner System, including Earth, Luna, Mars and Mercury. This process may or may not involve a war between Sky and Surface, or some degree of accommodation to the needs of the surface-dwellers (12).

Venus will become Earth-like, but it will not be Earth. Two great continents will stand amidst shallow salty seas, but these continents lack the rugged mountains and these oceans the abyssal depths of the Earth's, because of the much simpler Venusian geological history (which involved complete crustal recycling every several hundred millions years rather than Earth's tectonic dance of eruption, merging and subduction) (13). The air will be breathable, but also thicker -- the process of carbon-sequestration will reduce its density but not down to that of the Earth, and a thicker atmosphere will be beneficial as protection from solar radiation, especially given the weaker magnetic field.

Venusian populations, fauna and flora will be more slender than those of Earth, both because of the lower gravity and because ectomorphy is adaptive to hot environments. With thick air and low gravity, flight will be easier. Humans won't be able to fly with simple strap-on wings, but the minimum practical airplane or glider will be much smaller and more manageable than is the case on Earth (14). It is possible that a Venusian subrace may emerge which is engineered for flight with hollow bones and improved respiration -- shades of Olaf Stapledon! This flying culture might develop from the old floating cities, and use them as homes (15).

Likewise, in the extensive shallow seas, there might develop a marine sapient culture. This might be based around cetaceans, and it might also include marine-modified humans like the "selkies" of Earth (see Part 3), who might also participate in Venusian colonization.

A terraformed Venus might resemble the Venus of the old pulps in several ways. With shallow seas and low-lying lands, there would be much marine life and wide marshes. Extensive forests and jungles would be an obvious ecological component stablizing the terraforming and keeping carbon dioxide sequestered. If there was political disunity, possibly stemming from the terraforming disputes, there might be all sorts of exotic adventures and intrigue. With the ruins of earlier colonization stages and failed projects littering the landscape, it might even be a place that an Eric John Stark or a Northwest Smith might find not wholly unfamiliar. Heck, at least one zoology enthusiast might create a safari park stocked with dinosaurs, and some might later escape and go feral ...

Venus would have a rich future, possibly with as much change and history and brilliant culture as has the Earth.
===
Notes:

(1) - The Venusian crust has had more than enough time to equalize itself to atmospheric temperatures.  Unlike Earthly caverns, Venusian ones won't have cooled during the night and retained the lower temperatures, because the Venusian night isn't that much cooler than the Venusian day.  Furthermore, since Venus is still geologically active, temperature probably increases with depth as one descends, just as is the case on Earth below a certain level.  This factor, coupled with the lack of plate tectonics, is one big reason why the Venusian crust melts every several hundred million years, renewing its own surface.

(2) - This would necessitate nuclear reactors as the only practical means of powering the air conditioning.  Fortunately, Venus is probably almost as rich in radioactives as is the Earth, since it is still geologically active and hence probably has a uranium-thorium core just like our own planet.

Furthermore, given the extreme deadliness of the Venusian heat, each base would probably require multiple reactors and backup air conditioning systems for safety purposes.  Most Solar worlds will kill you slowly on a life support failure:  Venus would kill you relatively quickly.  One backup system that would help would be to maintain a "cold room" containing ice or liquid nitrogen, which could be used as a heat sink should the air conditioning temporarily fail.

(3) - Any significant breach in a compartment would be instantly fatal to the occupants:  90 atmospheres of 400 degree Centigrade carbon dioxide liberally laced with sulfuric acid would pulp, bake and dissolve the unfortunates therein, leaving only thready black goo in roughly humanoid shape.  Some large bones and the teeth might survive for a while.  One would be wise to design habs and large vehicles with multiple hulls and sealable compartments to limit the consequences of such a penetration:  given the extreme atmospheric pressure, however, this solution would be more than minimally expensive, meaning that some would be tempted to cut corners, resulting in the occasional disaster.

(4) - An airhab might be designed to do both:  it might be an airship which docked for long periods at a time to provide services to ground habs, much like crane-ships and drill-ships do in the seas and harbors of our Earth.  Docking would not necessarily require descending to the surface:  with the carbon- and silicon-fiber cabling already under development, the airhab could remain at a cooler and lower-pressure altitude, communicating by cable-car with the groundhab.  The cable-car could mate with an airlock at the groundhab, so that the passengers could travel from airhab to groundhab in a shirtsleeves environment.

(5) - This is a somewhat counter-intuitive design, because Earthly airships (which use hydrogen or helium as lifting gas) keep their passenger gondolas or decks below their lifting gas bags, so that gas leaks will have no effect on equipment or personnel.  However, on Venus, breathing and lifting gas can be the same, so the design works just fine.

(6) - Safety gratings could ensure that the airhab didn't jettison livestock or (worse) passengers while ensuring an emergency ballast drop.

(7) - The main problem in spacesuit design is combining protection with flexibility. In the Venusian environment, any sizable suit breach would be instantly fatal, and even a pinhole puncture would cause severe injury to the wearer. Consequently, the best design for a Venus suit is a spherical or ellipsoid, heavily armored life support capsule, with the head turret, arms and legs being remotely operated from within that capsule: rather like the "Fat Man" deep-sea diving suits from Tom Swift, Jr.

(8) - Venus is smaller, less dense, and (unlike most terrestrial worlds) hotter and under greater pressure than the Earth, which complicates mining operations.

(9) - I see Venus as the location of hardship stations, and possibly even penal colonies.  Escape from a Venusian penal colony would be considerably more difficult than from a Lunar or Martian one:  even technically-competent prisoners with access to the machine shops would have trouble cobbling together a Venus Suit.

(10) - Carbon-filament nanofibers would probably be destroyed by the conditions pertaining on the Venusian surface, but then the aerohabs aren't meant to descend to the surface, and probably couldn't survive such a descent even if they were made of more refractory materials.

(11) - As has been pointed out already in reference to terraforming Mercury.

(12) - The air-dwellers would have better access to space and hence the commercial advantage, but their large low-density cities would be terribly vulnerable to nuclear weapons; the surface-dwellers would have ready access to all sorts of metals and would be living in habs equivalent to massively-strong bomb shelters, but would have difficulty reaching space against the opposition of the air-dwellers.  It would be an interesting conflict for wargaming purposes.

Of course, it would be better for both sides if they didn't fight, as each would have things the other would need, and hence good grounds for mutually-beneficial trade.  However, because they would probably be culturally-divergent, this might not be enough to keep them from engaging in open warfare.

(13) - It might be a good idea for the terraformers to deliberately open some volcanic rifts, even though this would add to their gas sequestration problems, if only to relieve the internal heat and pressure and hence postpone the Big Melt.  Not that the Melt would be likely to happen any time soon, but I would imagine that some pretty big faulting and rifting occurs naturally on Venus from time to time well before the Melt -- better to have this occur at times and places of the terraformers' choosing, rather than right under a city!

(14) - We've already developed man-portable single-user jetwing vehicles:  these would work even more efficiently on Venus than they do on Earth.  Jet-powered aircycles might become a common mode of personal transportation up among the airhabs.

(15) - Once Venus was fully terraformed, there would be no particular need of the old-fashioned airhabs, but traditions die hard, and hence the culture might continue, finding new economic occupations.

Worlds For Man - Part 1 - Mercury

"Worlds for Man - Mercury"

(c) 2007, 2011 by Jordan S. Bassior

Little Mercury, the smallest of the currently-official eight planets, is notable for her density (second densest world in the Solar System) and proximity to the Sun. Mercury is an airless rockball, superficially similar to Luna, which has been stripped of her volatiles by heating and of some of her lighter solids by impacts. The result is a dense and refractory planet, rich in heavy elements but poor in many lighter ones.

Mercury is primarily of economic interest for three reasons. The first is that it is probably the richest of all Solar worlds in terms of readily accessible metals, radioactives and other heavy elements (1). The second is that it (like Luna) probably has significant deposits of tri-helium on its surface (2). The third is that Mercury is bathed in solar energy, and is furthermore a good base from which to construct and deploy close-in orbiting Solar energy collectors (3): energy may also be drawn from Mercury's passage through the Sun's magnetic field.

In the Near-Term, colonization of Mercury will focus on prospecting and mining. Mercurian ores can be easily (4) refined  using the abundant energy, launched up the shallow gravitational well, and then dispatched elsewhere in the System. Though Mercury is deep within the Sun's gravity well, the total delta vee required to get elsewhere in the system from the surface of Mercury is still smaller than that required to do so from the surface of the Earth (5). One disadvantage is that a space elevator isn't practical: Mercury rotates on its axis far too slowly for that.

Despite Mercury's proximity to the Sun, it is in some ways a surprisingly friendly target for early colonization. To begin with, Mercury has a magnetic field strong enough to ward off the Solar wind, so colonists need not worry about being bombarded with charged particles. There are four good sources of energy: solar radiation, solar magnetic, fissionables, and fusibles. Though the dayside is hot, some polar regions are in perpetual shade, and the rotation is slow enough that ground vehicles could easily remain in the night side or twilight zone (important for prospectors!).

Like Luna, there are probably ice deposits at the poles, providing a small but vital source of water, hydrogen and oxygen for a starting colony.  Unlike Luna, the ice deposits probably exist only at the poles, so at some point water would need to be imported.  Hydrogen might also be extracted by magnetic scoop from the solar wind, providing a source of fuel for fusion reactors.

We may thus envision Near-Term colonies being placed in the polar regions, with a webbing of solar-magnetism power receptors and electric train lines running from pole to pole. Prospectors would venture forth from the polar colonies, probably in large tracked or balloon-tired wheeled all terrain vehicles, endeavoring to remain near the Terminator or Twilight Zone. To maximize their exploration in the limited available time, each sapient prospector (6) would command a fleet of roving drones. Almost all of this infrastructure would be easily constructable from local materials.

The poles themselves would become increasingly crowded, owing to the difficulties of permanent settlements elsewhere on the planet. Direct launches and landings might well be made at the poles, because Mercury is small and very slow-rotating, and hence the delta vee advantages of equatorial operations would be small compared to the disadvantages of the extreme temperature variations. To the poles would come imports of volatiles and lighter solids; from the poles would depart shipments of heavy metals, radioactives and rare earths for the Outer System.

Mercury is also, as I mentioned in the previous chapter, ideally positioned as a base for operations designed to extract Solar energy. Eventually, there would be frequent launches of material to construct close-in Solar power satellites.

There would in general be a high proportion of robots to organics, because the cost of constructing robots would be relatively low. Mercury would be one of the first worlds in the System to have a large robotic population (another such world would be Venus, considered in the next part). By the end of this period some of them would be sapient.

Mid-Term development would largely continue on the same terms. The web of rail and power stations would spread over the Mercurian surface. Permanent settlement of the temperate and equatorial zones would begin, fed by growing population and new technologies that would enable excess dayside heat to be conducted to and radiated from the nightside. These new towns would be mostly underground, to avoid the thermal stresses at the surface, and would be connected by ultrafast underground maglev railways.

Most of the prospecting work would have been completed and most of the surface resources taken. Mines would now burrow deep into the crust, and begin tapping the mantle. Hermeothermal (6) energy might be employed as a cheap alternative to nuclear reactors.

The initial work of Solar materials extraction would be based from Mercury: the first vast electromagnetic coils would have been drawn from Mercurian metals, though in time that operation would become self-supporting. Almost certainly a lot of the plant would be owned by Mercurians.

The Mercurians themselves, both organic and inorganic, might have engineered themselves to better suit their world. Thermal and hard-radiation tolerance would be obvious design goals. For humaniform organics, part of this might take the classic pulp SF approach of extremely dark skin, and possibly third eyelids to protect against glare (7).

Terraforming is also a possibility. Sunshades could be deployed to lower the insolation on the dayside (this implies that solar power production moves offworld) and mirrors used to provide it to the nightside; iceteroids crashed to supply volatiles, including both atmosphere and hydrosphere. Mercury would probably always be a hot desert world by human standards, but in this period it might become shirtsleeves-habitable, especially to the Mercurians themselves.

Long-Term development would probably see core-tapping to extract rich concentrations of heavy elements. Mercurian geology (hermeology) would be brought completely under sapient control. Specialized races of animals or even sapients might be created to swim in the core and seek out especially valuable swirls of metals (8).

Solar operations would have long since become independent of Mercury, and with the availability of vast amounts of hydrogen, deuterium, tritium and trihelium from the Sun and the gas giants, the heyday of Mercury's importance as an energy-production center would be past. But Mercury would still make a good base for spacecraft construction, and despite its depth in the Sun's gravity well might become a launching station for the faster kinds of koopcruisers (9), oortcruisers (10), and starships.

Thus, the smallest terrestrial planet of the Solar System would be firmly connected to the longest-term future of Mankind.

===

Notes:

(1) - Earth is slightly denser and eighteen times more massive than Mercury, so Earth has in absolute terms far more heavy metals.  But Earth has also two and half times the gravity of Mercury, meaning that a mine of given structural strength can sink two and a half times as deep into Mercury as Earth.  Our deepest Earthly mines are about 4 miles down:  we could sink shafts 10 miles deep into Mercury.

The area-volume relationship also helps.  Mercury has a full one-seventh the surface area, and almost half the land surface area of the Earth, which means that the volume of accessible crust is roughly the same barring seafloor mining on Earth, and even with seafloor mining, a much larger percentage of Mercury's mass is within 10 miles of the surface than the percentage of Earth's mass within 2.5 miles of the surface.

Add to this that Mercury is, as far as we know, virgin for mining.  The easily-accessible surface deposits which, on Earth, were played-out decades, centuries or even millennia ago, would on Mercury be simply lying there for the exploitation.  The first century or two of Mercurian mining might hence be very profitable, as one wouldn't even need to go down that deep to strike rich lodes.

And Mercury has almost certainly been differentiated by geological processes, meaning that rich lodes would in fact be found.  Unlike smaller and colder bodies, Mercury had a molten core at least in the past, and possibly in the present, mixing, re-mixing, and thus concentrating valuable metals.  Mercury is likely to be the location of future metals rushes.

(2) - Both Mercurian and Lunarian tri-helium is sprayed into the regolith by the solar wind.  Logically Mercury, which is three times closer to the Sun than Luna, should have richer deposits of tri-helium than Luna.  On the other hand, that same Solar radiation might knock the tri-helium loose again, and once loose it would be lost due to the low Mercurian gravity.  On the gripping hand, Mercury's gravity is greater than Luna's.  So the issue is complex, but some tri-helium is almost certainly there.

(3) - Remember the close-in Solar power arrays proposed in the Near-Term for colonization of the Sun?  The materials needed to build these arrays need to come from somewhere.  Earth is relatively far away and Venus is a very hostile environment for factory and launcher construction and operations.  Mercury is the closest planet and will be, once we become accustomed to the extreme insolation and delve out underground bases for the crews, a relatively safe place from which to operate.

(4) - Assuming a background of experience in low-gravity, vacuum-environment, solar-flare endangered mining operations.  Obviously, the early decades of such operations might be plagued by fatal and costly accidents, as is the case in the early decades of any new resource extraction technology.

(5) - Though the Solar gravitational well is deeper than the Earth's, an object on the surface of Mercury is already in orbit around the Sun, and hence if it can achieve Mercury's escape velocity can then use a continuous low-thrust system such as an ion drive to spiral outward.  Mercury's escape velocity is only 4.25 km per sec, as opposed to the 11.2 km/sec required to escape from the Earth.

(6) - By analogy with "geothermal."

(7) - Barring at least Mercury-orbital sunshades, the surface of Mercury would obviously be too hot for our kind of life, even if such life were modified to be able to operate in vacuum without spacesuits.  On the other hand, orbital sunshades are not a very advanced technology, and the infrastructure to deploy such would be created in the process of creating the infrastructure to deploy Solar-orbital power collectors.  And, even if one is wearing a spacesuit or living in a hab, heat- and radiation-tolerance would allow one improved survival abilities in a crisis, where one might want to turn the air conditioning down or operate for extensive periods on the surface with no radiation shielding save that of one's suit.

(8) - Implying a high-temperature silicon or even exotic materials-based biochemistry, of course.

(9) - Koopcruisers ("Kuiper Belt Cruisers") would be longer-ranged ships than ordinary interplanetary vessels, designed and provisioned for flights across average distances of 10's of AU, rather than the AU's common in the System proper. The difference between an Outer System IPV and a Koopcruiser would be of course a vague one.

(10) - Oortcruisers ("Oort Cloud Cruisers") would be very long range space ships, designed and provisioned for flights across average distances of 100's of AU. Sufficiently long-range oortcruisers would essentially be short-ranged starships.

Worlds For Man - Part 0 - Introduction and The Sun

"Worlds For Man - Sol"

(c) 2007, 2011 by Jordan S. Bassior

Introduction

This is an overview of the colonization and economic potential of the Solar System. In general when I talk about "Near Term" possibilities I am referring to throroughly known engineering; "Middle Term" assumes the possibility of considerable engineering progress and some scientific progress; and "Long Term" of vast engineering progress and major scientific progress. Obviously, the longer the term, the greater the speculation involved.

I considered doing it in terms of the rough time frames, but realized that I have no good way to predict the speed of scientific and technological progress. If you believe the most fervent advocates of The Singularity, we might get to "Long Term" levels of progress by 2050 or so; otherwise, I would imagine it would take many centuries.

I'm doing the system from the inside out.

The Sun

We normally don't think of the Sun when we think of space colonization, but it does contain some 99% of all the mass in the Solar System. Of course, it's hardly an inviting environment: at its surface the temperature is 5500 K, high enough to vaporize any substance we know how to make. This temperature climbs to 13.6 million degrees Kelvin in the core, enough to fuse hydrogen, which is exactly what happens, and what produces most of the Sun's energy (the rest being produced by gravitational pressure).

The Near Term exploitation of the Sun, therefore, centers not around colonization but around energy extraction. The vast majority of the Sun's energy, of course, is wasted from our point of view, because it is merely emitted into space without striking the Earth or any other worlds in our system. So the first thing we might do would be to intercept that energy and convert it into a usable form.

A solar panel in orbit at 1 AU (the Earth's orbital distance) from the Sun will receive 1.366 kilowatts per square meter of energy. If it were at orbit at 0.5 AU it would thus receive 1.866 kilowatts per square meter; at 0.25 AU almost 3.5 kilowatts per square meter, and so on (following the Inverse Square law for radiation).

Therefore, it follows that if we had a mature interplanetary transport capability, it would make sense to station our solar energy panels as close to the Sun as possible. There are, of course, tradeoffs: the closer the panel is placed to the Sun,  the greater the drift imparted by radiation pressure and the more heat it must dissipate.  These are both serious issues, as the former complicates the task of beaming power to the receiving-stations, and the latter risks loss of one's collectors.

Getting the energy back to the Earth or other inhabited places is in principle easy: one would connect the solar panels to a maser emitter, and beam the energy as microwaves to a receiver near where the energy was to be employed. The details of such systems have been long explored in both science and science fiction:  basically, one uses the reflection from the transmission to keep the beam on track and safely shut the beam off should it wander off-target.

Such an endeavor, once begun, would be highly-profitable, making it a practical project for any civilization which has reached the point of routinely sending at least robotic devices to the vicinity of Mercury, the planet most logical as a source of mass for the project.  Obviously, placing a crewed station on Mercury itself would be the easiest way to manage the mining operations.  More on this in the next installment.

In the Middle Term, our engineering and our materials science might advance, enabling the solar panels to be placed closer and closer to the Sun. If we developed a really good energy absorption and retransmission system, this might work as a cooling device for a spacecraft, enabling manned exploration of the corona and unmanned exploration of the deep photosphere.

One exciting idea would be the remote manipulation of Solar substance by means of powerful electromagnetic fields. Such fields might be externally generated, or might be used as catalysts to reshape the exceedingly powerful electromagnetic fields which the Sun generates naturally. This might enable the direct mining of the Sun for matter (mostly hydrogen and helium, but truly vast quantities of both, and even the heavy elements become significant when you filter enough Solar matter). Another application might be the generation of extremely powerful energy beams ("Doc" Smith's "sunbeams"), for military or engineering purposes.

In the Long Term, we might develop materials science (possibly employing generated force fields, or exotic matters) to the point where we could maintain organized structures at the immense pressures and temperatures inside the Sun. This would enable actual colonization of the Sun itself, though probably not by organic life forms: such writers as Arthur C. Clarke, Stephen Baxter, and John C. Wright have imagined these sorts of operations.  Among the purposes might be colonization (by greatly-modified or uploaded humans in the form of exotic-mater machines) or the formation and extraction of exotic forms of matter creatable only under the extreme conditions prevailing within a star.  Another aim might be the direct  management of the Solar power cycle, to a variety of possible ends.

Next: Mercury