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Eyes Turned Skywards

I think it's indicative of how bonkers awesome TTL has become when you have to discuss replacing comsats at EML2 because people have been regularly going to the Moon for over a decade. It's also amazing how much the depot/tug architecture opens things up. At this point it seems the only thing stopping a mini-Discovery class station at EML2 is money. Maybe that could be pushed once Oasis is spun up to provide a transfer/fueling station and, eventually, a construction hub for Mars craft.

That said, I do have a concern. You've referred to Orion missions as being "only two launch" in a couple of posts, but what about the logistics lander? Does the one sent initially really have enough supplies to support three or four years of missions? Also, where did the pressurized rover sit on the ride down? The cabin had to be a bulky piece of hardware.
I believe that after the Orion base modules only a single Artemis lander is used per crew rotation. That carries some of the supplies for the mission, with the Russian Luna-Pe providing extra supplies.

I'm also fairly sure only the one rover was sent, again with the base modules.
Looking at the discussion after the part II finale (because I too found an interest in the Mars Direct plan)... I don't remember seeing these two renders by nixonshead in the wiki gallery...

(they also seem to be his first for this timeline as well...)

Probably because they're not "canon" - they were Nixon's first stabs at artwork for the timeline, and e of pi and Goblin had to correct some things on them, like the size of the mission modules.
I think part of the problem is that it's very hard to get an accurate fix on just what the Chinese have spent on space, and that would be true in this timeline as well. I'll roll with the butterflies.
Besides what e of pi said, as I explained a long time ago I was working under the assumption that the Chinese have had three human spaceflight programs when I wrote their initial post; the well-known late 1960s and early 1970s program that was cancelled due to the Cultural Revolution and insufficient funding; a brief program in the late 1970s and early 1980s that was cancelled for being too ambitious; and, of course, the current Shenzhou program, which traces back to 1985 (the program itself began in 1992, but there was earlier preliminary work involving the vehicle design and other aspects).

I did not think that the PoD was likely to cause their first program to survive much, if at all, longer, but the second program is said to have involved plans to build a Chinese space shuttle, probably more like the proposed HOPE or Hermes than the Space Shuttle or Buran. This, obviously, would be affected, and my assumption was that the Chinese would be much more likely to go for a capsule at this point than a space shuttle, since shuttles wouldn't be en vogue the way they were IOTL, and one could get the core propaganda effects I read the Chinese as looking for just as well as with a capsule (viz., "We are on par with the Western powers!" as I more wordily explained in my initial post) given that space shuttles don't actually exist. I also used author fiat and the butterfly effect to delay the start of their second program to the early 1980s, when they're a little bit richer and more politically stable than they were in the 1970s.

Together, these mean that when they do start a space program, they have a clearer idea of what to do and a bit more to do it with, so they begin what is essentially an equivalent of the Shenzhou program (that is a crewed capsule and launcher) in 1985, when historically they began studying crewed spacecraft leading up to Project 921-1 (i.e., Shenzhou) at that time, with no actual program start until 1992. Historically, they got a boost early on in their actual program by buying Russian technical expertise; here, that happens later, when they're more developed, but they get a lot more because the Russians are more desperate and don't have many other options, allowing them to get a part of the Mir station and a lot of experience in station operations on the cheap. At the same time, though, it takes time to integrate these things into their program and they get a little bit distracted by having most of what they were aiming for basically handed to them on a silver platter. So if you compare the amount of time it's taken them since various milestones to achieve the next milestone, it's not actually that much faster or even in some cases slower than OTL--for instance, Longxing actually first launched two years later relative to its program start than Shenzhou did (nine years after 1985, in 1994, compared to seven years after 1992, in 1999). (Of course, they also pushed it flying crewed sooner after this milestone--the first crewed Longxing flight is in 1995, whereas Yang Liwei didn't fly until 2003)
Nixonshead has so many possibilities to choose from for renders:

1) The new Chinese station; or
2) The new Russian station; or
3) A Hope-C "mooring" with Freedom.

My money is on (3), but I'm sure whatever he's come up with will be worth the wait.

Well, your shortlist pretty much matched ours, but I'm afraid you guessed wrong for the final image. Instead, and in a different format than usual, may I present China's Tianjia-1 space station:

It looks absolutely magnificent!
Though I was hoping for Russian Partly-Commercial(!) Mir-2. Not to mention the irony of it geting the general outline of OTL Mir.
Part IV, Post 25: Asian space exploration
Eyes Turned Skyward, Part IV: Post #25

By the late 1990s, the caution that had led the People’s Republic of China to reject ambitious plans for expansion into space a decade earlier in favor of a more measured and Earth-centered approach was quickly dissipating. Not only had the Chinese economy continued its rapid growth in the intervening years, giving the Chinese government more resources and a considerably improved manufacturing base to tap for space exploration, but the collapse of the Soviet Union had been a vast windfall, allowing the Chinese to acquire considerable experience in space operations for almost nothing. Between these two factors, the idea of launching Chinese spacecraft to other worlds no longer seemed as impractical or expensive as it had been the last time that the question of greater Chinese involvement in space exploration had arisen.

Beyond merely financial factors, the irresistible movement of the Artemis program towards the Moon had made starting some type of Chinese program to go beyond low Earth orbit appear to be a national imperative. The immature Chinese human spaceflight program was necessarily still focused on establishing an entirely indigenous space station program like the Americans and Russians had maintained for decades. Chinese manned spaceflight beyond low orbit could not practically be expected for years, but robotic probes offered an immediate response. They were, perhaps, not as exciting as astronauts and cosmonauts walking on the Moon, but nevertheless the Politburo would be able to say that China was out there exploring the universe just like the Americans, and even robotic successes would showcase Chinese developments in science and technology.

As with Russia and America before, China opted to begin its exploration of space by demonstrating the technology that would be needed for later, more scientifically sophisticated missions. These first missions, although they would carry a few instruments, would mostly be focused on showing that Chinese deep-space navigation techniques, communications stations, injection stages, and other equipment would function properly over the gulfs of time and space that separate the Earth from the other planets. Also as with Russia and America, there were bitter internal debates about where Chinese spacecraft should travel, at least for these early missions. The Moon was nearby and easy to reach, but any Chinese probe sent there would be completely overshadowed by Artemis and follow-up programs. Conversely, Mars and Venus were more distant and offered more complications, but also a field free of any overpowering competition, for good or ill. Given the prestige rationale for the program, the Moon was quickly eliminated from the competition, leaving it merely an argument between Mars and Venus. Like the Japanese at the same time, the Chinese realized that Venus was the easier of the two destinations to reach in both time and energy, and could offer more benign operating conditions once reached provided the toxic and crushing atmosphere was avoided. And, of course, Venus was also the less-explored of the two nearest neighbors to Earth, so even engineering spacecraft could be expected to make discoveries there.

The public result of this deliberation came in early 2000, when the Chinese announced that they had begun a “Chinese Venus Exploration Program.” This long-term effort to uncover the mysteries of Earth’s closest sister saw the first two orbiters scheduled for launch in 2004. Chinese spokespeople suggested that the technological developments needed for exploring Venus could be applied to “other” exploration efforts, vaguely alluding to possible lunar or Mars exploration efforts. Some American sources picked this up and made a minor furor over Chinese plans to “leapfrog” “Moon-obsessed” NASA by heading for Mars, but they made little impact in the face of demonstrated NASA successes and public disinterest in “racing” China, and the storm, such as it was, soon died down.

Meanwhile, the Chinese were working hard to pave the way for their orbiters to Venus. Besides designing and building the actual spacecraft, a considerable amount of ground infrastructure and equipment would be needed before the missions could launch. Even before they announced their Venus Exploration Program, the Chinese had begun working on deep-space communications complexes in Xinjiang in the west of the country and on the Shandong peninsula in the east. Together, these two complexes would provide a greater field of view than a single site like the Japanese Usuda complex, but were still far short of allowing continuous communication and tracking like NASA’s Deep Space Network. The Chinese began to angle to build a third center in South America or southern Africa to fill the gap. In the interim, mission operations would be timed so that they could be seen from China if at all possible, and contingency arrangements were made to with the European Space Agency to make use of their deep-space communications facilities if necessary in exchange for other, future considerations. Aside from these communications facilities, the Chinese also constructed several tracking and navigation observatories between the main complexes, creating a great belt of facilities along their country’s centerline and augmenting their power to support distant missions.

At the same time, they were confronting the challenges of building spacecraft designed to operate not just a few hundred or even a few thousand kilometers above Earth, as Chinese satellites had been doing for years, but tens of millions of millions of kilometers away, so far that commands would take entire minutes to travel from transmission stations on Earth to the spacecraft. More than that, spacecraft near Venus would have to contend with a Sun twice as bright as back home, and with solar wind more than twice as intense, thanks to the lack of a Cytherean magnetic field. Ironically, generating power was another challenge; although the Sun was twice as bright, this meant that solar panels would have to operate at a higher temperature, reducing their efficiency and requiring special design and construction to ensure they provided the required amount of power. Careful design and testing would be needed, and entirely new kinds of testing facilities were built to ensure that the Jinxing, or “golden star” probes, named after their destination, would succeed. Even then, though, there was always the possibility of an unforeseen problem, a simple statistical fluctuation, so the Chinese opted to adopt the strategy that had once been used by the Soviets and Americans in their exploration of space, by sending two spacecraft. Even if one failed, the other might succeed, after all.

Constructing this network of ground facilities and developing a giant leap in space technology did not come easily, or quickly, and the Chinese were forced to slip the planned launch date twice--first from 2004 to 2005, then from 2005 to 2007. It was also expensive, with the cost of the spacecraft and their ground facilities more than trebling from initial projections in 2000 by the time they were actually launched. Nevertheless, they proceeded, and by mid-2007 their Jinxing 1 and 2 spacecraft were being rolled out to the launch pad atop the Long March 3As that China had designed to launch spacecraft to geostationary orbit, and which were now being repurposed to launch others beyond Earth’s influence. As the launch window opened early that May, Jinxing 1 soared into the skies above the launch pad in Sichuan. Only a few minutes into the flight, however, launch controllers began receiving increasingly worrying telemetry data from the rocket, showing it drastically underperforming after first-stage separation. Performance only worsened as the second stage continued to burn, and within seconds the spacecraft appeared to be drifting irrevocably towards impact in Taiwan. Range safety immediately intervened and triggered the rocket’s destruct charges, sending a hail of debris down into the Taiwan Strait.

With Jinxing 2’s launch scheduled for just a few days later, mission designers immediately put it on hold plunged into a frenzy of activity intended to identify and cure the failure’s cause as quickly as possible, hopefully before the launch window closed. Careful inspection of launch telemetry and launch vehicle modeling soon showed that the second stage’s underperformance could be entirely explained if the fairing used to protect the probe from atmospheric loads had failed to eject after first stage separation, as planned, but had instead remained attached throughout the second stage burn. Disassembly of Jinxing 2’s fairing and inspection of its parts showed that several of the explosive bolts intended to force the two halves of the fairing apart as part of the separation sequence were faulty; although they appeared to be ordinary explosive bolts externally and to simple tests, they would not detonate on command, apparently due to a bad explosive filling. Later investigation determined that many explosive bolts from the lot that had been used for the two Jinxing fairings had originated in a batch whose whose quality control inspections had been faked, leading to the arrest of several officials at the plant that had manufactured that lot on corruption charges, and the suicide of the plant’s manager.

In the short run, however, launch managers scurried to replace the fake bolts with real bolts, carefully testing each component for proper function. Just days before the launch window closed, they were able to roll Jinxing 2 out to the launch pad, and it rocketed into the air only hours before they would have been forced to roll it back after a series of last-minuted launch delays. Controllers breathed a sigh of relief when the spacecraft and its trans-planetary injection stage made it to orbit in good condition, and cheered when that stage successfully placed Jinxing 2 on a trans-Venus trajectory a few hours later. Unlike their Japanese counterparts earlier in the decade, Chinese mission controllers saw an uneventful cruise phase over the next several months, ending with Jinxing 2’s insertion into Venus orbit in early November 2007. Over the next several years, it carried out observations of the upper atmosphere, corroborating several results from Japan’s Akatsuki probe in the process. After just over three years of operation in Venus orbit, Jinxing 2 failed in late November of 2010, mysteriously shutting down between its daily communications sessions.

While Jinxing 2 was quietly studying Venus, work was already well underway on its successors. It and its sister probe had always been intended as pathfinders, more technological experiments than full-fledged spacecraft, and with confirmation that they worked the next phase of the Chinese Venus program began. The next two spacecraft, Jinxing 3 and 4, would take the basic spacecraft design developed for Jinxing and scale it up, creating a platform more than four times as heavy and much more capable. They would also be taking another major technological leap by carrying a synthetic aperture radar, or SAR, to Venus, instead of another crop of atmospheric instruments, allowing them to peer through the all-covering clouds of the planet for a glimpse of her surface. The last spacecraft to carry a radar to Venus had been NASA’s VOIR in the late 1980s, and since then many technological advances had allowed for smaller, light, yet higher-resolution radar instruments that would enable even better maps of the planet’s surface to be made.

Besides taking advantage of technological advances, the Chinese had another trick up their sleeves to reduce their spacecraft’s weight. Unlike VOIR, which had propulsively put itself into a low, circular orbit, their Jinxing spacecraft would use aerobraking, as had several of NASA’s Mars orbiters since the Mars Pioneer. The technique had been considered but rejected for VOIR due to uncertainties in the Cytherean atmosphere, but improved data from Jinxing 2 and Akatsuki, and the fact that they had two probes, convinced the Chinese that they could afford to risk a problem. Even so, their aerobraking maneuver would be careful and conservative, favoring “doing it right” over “doing it fast”. Without this gamble, Jinxing 3 and 4 would have been much more massive, and impossible to launch on Chinese launch vehicles.

Initially targeted for launch in 2010, delays in testing their complex radar systems pushed them to the next launch window in 2012. After careful testing of the fairing separation mechanisms, both were lofted towards Venus successfully by their Long March 3B boosters in early March, to reach the planet in August of that year. A long, careful program of aerobraking followed for both spacecraft, taking nearly a year and a half to put them into their operational orbits. Data collection is ongoing, but the Chinese have recently released preliminary maps of parts of the Cytherean surface, on which Doumu, the Queen of Heaven, has joined her sister Hera of the Greeks in naming the planet’s surface features, in accordance with IAU conventions. Many other famous Chinese women and goddesses are also awaiting formal acceptance by the IAU of China’s naming proposals.

As Jinxing 3 and 4 continue to gather data and build the best map yet of the Cytherean surface, the Chinese are working on Jinxing 5 and 6, which they say are planned to duplicate the balloon mission proposed to NASA as VEIL and implemented by the French and Soviets as Eos, but on a much larger scale. Between them, the two orbiters will deliver a dozen balloons to Venus, then serve as relays while the balloons drift through the atmosphere, tracking wind movement and exploring its deeper reaches. Although ambitious, Chinese mission planners have good reason to hope for success, given their successful history with the planet.

While the Chinese had been developing Jinxing 3 and 4, their neighbors to the south had begun to contemplate a planetary science program of their own. Although India’s space program is one of the oldest in the world, dating back to the establishment of ISRO in 1969, it has always been focused more on the practical, day-to-day benefits that space technology can provide than the more far-flung and inspirational flights of fancy that most other programs have indulged in, as befits the program of a nation so wracked by poverty as India. Nevertheless, Indian aerospace engineers had always had the same dreams as their counterparts throughout the world, and never stopped thinking about where India could go in space, whether or not it could afford to do so at the time. By the later parts of the 2000s, their efforts began to bear fruit as India developed and became increasingly wealthy and able to look outwards. As with the Chinese a decade earlier, Indian leaders felt that a more vigorous space program would be an effective and relatively inexpensive method of showing off India’s technical prowess, and that a planetary science program would be a particularly visible and yet cheap method of making the space program more vigorous. Thus, even as ISRO began studying an indigenous Indian human space program, they also began traveling along the same well-trod path of analyzing robotic missions beyond Earth orbit.

Just as with their predecessors, Indian mission planners quickly came to the conclusion that only missions to Venus, Mars, or the near-Earth asteroids and comets could effectively fulfill their geopolitical goals. Mercury, the asteroid belt, and the outer planets would be too difficult, risky, and expensive to reach for a new country just starting to venture beyond Earth orbit, like India, while the Moon was too well-trodden and too heavily occupied by NASA for it to be very attractive a target. Compared to the asteroids, Mars and Venus offered more prominent destinations and a greater link with the cultural zeitgeist, especially in the West. Of the two, Mars offered a somewhat more open playing field: while ongoing JAXA and NASA missions at the Red Planet meant that ISRO’s efforts would inevitably be compared to their more developed capabilities, Venus had shaken off its traditional neglect and its selection would now mean comparisons to Japanese, Chinese, and American missions, with relatively little ability for an Indian mission with a necessarily limited budget to make any significant impact. As the Chinese and Japanese had before them, the Indians chose the more open playing field, electing to begin serious conceptual studies of a Mars orbiter in late 2007. Over the next several years, they continued to refine their mission plans, developed prototype hardware for several instruments, and performed limited tests of instrument and spacecraft hardware while awaiting the government’s decision to proceed with the mission.

With budgetary estimates, construction timelines, and reliability figures changing from best guesses into firm numbers, that approval came in late 2011, giving ISRO’s engineers two years before the next launch window to build their probe. As with Jinxing 1 and 2, it would primarily be a technology demonstrator, but like those spacecraft it also carried a modest scientific payload, mostly focused on aeronomy, or the study of the upper atmosphere, although a wide-angle camera would also be carried for public relations and to study Martian weather. The last aeronomy-focused spacecraft to visit Mars had been Pioneer Mars thirty years earlier, so there was great opportunity for new discoveries, or at least solid refinements even with the kind of spacecraft India could afford.

Despite some controversy in the Indian press over the cost of the spacecraft, which although much cheaper than spacecraft from other countries still had a price tag of tens of millions of dollars, work proceeded without interruption from approval until it rode into orbit atop one of ISRO’s new PSLV Mk. III/GSLV launch vehicles in late 2013, with injection into a Mars-crossing orbit following shortly. The success was a much-needed boost for the PSLV Mk. III program, which had seen many problems with the solids that had been added to the PSLV core to boost geosynchronous transfer payload, but it was an even bigger one for the Mangalyaan, or “Mars Vehicle” team, and for ISRO as a whole. Despite competition from larger, more capable, and more expensive spacecraft from Europe, Japan, and the United States, Mangalyaan quickly captured world attention as the “underdog,” the little, cheap craft that was going to explore Mars despite the odds and despite the competition. The long cruise period diminished public interest somewhat, but as Mars Orbit Insertion approached, it began to rise back to what it had been just after launch, and in fact increased even further. The coincidence of a very close cometary flyby occurring soon after orbit insertion doubtlessly accounted for some of this interest, but much of it stemmed from the not altogether deserved reputation of Mars as a “spaceship killer,” a “flying graveyard” that had been eating probes for decades. While it was true that many probes had failed, most of those had been rush jobs from the early days of spaceflight, with little money, time, or experience for quality control. More recent spacecraft had been more successful in proportion to the care and expense lavished on them, and while Mangalyaan was cheap, it was certainly well cared for, and serenely glided into orbit without breaking a sweat. Since then it has been quietly accumulating data on the upper Martian atmosphere, complementing the array of other probes in Martian orbit.

Even as the Indians were launching their first interplanetary probe, another newcomer was trying their hand at sending spacecraft beyond Earth orbit. Unlike India or China, though, South Korea’s space program could at best be described as “nascent”; Korea had been too small and too poor for a space program to be an affordable proposition for many years. Moreover, unlike the equally poor China and India earlier in their histories, national security tended to tilt them away from a military rocket program which could possibly destabilize relations with China (and North Korea) instead of towards one. Nevertheless, in the last decade of the twentieth century they had started a modest program to develop observation and communications satellites and send a handful of astronauts to Freedom and Mir, a mix of practical applications and public relations-friendly activities, all conducted at low cost. By the late 2000s, their ambitions were growing, fueled by success in their earlier endeavours and reinforced by the boom in partially reusable vehicles overseas, a trend which was making it cheaper and cheaper for them to reach a little farther.

Of particular note to the Korean Institute for Aerospace Research and the Korean government was the fact that while ambitious probes like the Jinxing series or Japan’s efforts served as proud symbols of technical capability, their launch vehicles--the one element of a space program that Korea lacked--were rarely imbued with the same interest. Few Chinese citizens cared that each and every Jinxing probe had been launched on a Chinese rocket; they only cared that there were Chinese spacecraft out there, exploring Venus. Similarly, while many Koreans were proud of the handful of astronauts that had been launched to Mir and Freedom, few cared that they had hitched rides on American Apollos and Russian TKS spacecraft to get there. The obvious lesson, and one which KIAR assimilated, was that even a modest probe launched by a foreign rocket would be an attractive, and possibly cheap, method of demonstrating Korean technical prowess to the world, just as it had been for many other countries.

This realization dovetailed with ongoing research at KIAR into so-called “advanced propulsion” methods, particularly their relatively large and active solar sail program. Although solar sails had been relegated to science-fiction and small private efforts in the West, an influential KIAR research, Park Jong-Seok, had developed an interest in them during his education and had pushed for KIAR to develop the technology, arguing that it could allow Korea to “leapfrog” other countries technologically. While the resulting program was small compared to many other KIAR programs, it was still much larger than any effort anywhere else in the world, and by the middle of the decade had developed a variety of prototype sail materials and designs, along with exploring “multi-purpose” solar sails, like sails that would generate electricity in addition to thrust, and other aspects of sail deployment and control. All that was left was to actually deploy a sail in space and show that it would generate the expected thrust, a task admirably suited to a small interplanetary mission.

Together, these two strands of thought would lead to the beginning of the Korean Interplanetary Satellite program, aimed at sending a modest vehicle similar to the small spritesats proliferating in Earth orbit into interplanetary space, in the process testing solar sail technology. By hitching a ride on one of Northrop’s TransOrbital tug launches and taking advantage of spritesat-standardized hardware, KIAR could launch a spacecraft past the Moon at a cost that made even Mangalyaan look expensive, all while demonstrating a never-before used propulsion technology. iSat, as it became known, went from approval to launch in just under a year, being accelerated to escape velocity by one of Northrop’s tugs in late June of 2011. Solar sail deployment successfully followed, and the spacecraft has been cruising around the inner solar system since, maintaining intermittent contact with its Korean builders whenever it comes close to Earth. KIAR is currently studying follow-up missions that would use such solar sails to travel to Mars, Venus, or a near-Earth object of some kind, though nothing firm has yet been announced. Their success, however, has attracted a wave of study from other programs around the world, who themselves are attracted by the possibility of sending spacecraft beyond Earth orbit. It is possible that, by the end of the decade, every continent except Oceania will have launched at least one interplanetary probe, and it is even possible that the first private interplanetary spacecraft will have been sent beyond Earth orbit. Korea may have been the first to turn skywards because of reusability, but they do not look like they will be the last.
Ah, Venus! I was wondering, after the post a little bit back, how Venus could be neglected so long and by so many. Well, perhaps because it is a hell planet and landing a human being on its actual surface would require something like a submarine with a megawatt nuclear power plant just to run the air conditioner?:D

But still it seemed sadly neglected; easier to get to in terms of delta-V than Mars and much quicker too--though much harder to get something off of it again if anything goes down from orbit. Mars has two convenient moons that can serve as staging bases; Venus could sure use a moon but sadly has none.

I wonder if the Chinese would have considered, as I did when told the decades-before French-Soviet Eos probe used helium in its balloon (as did a similar craft OTL), that this was a puzzlement since in Venus's atmosphere, hydrogen would be an inert gas, with somewhat superior lift than helium, and despite the difficulties involved in keeping hydrogen liquid for the flight time from Earth to Venus it would be still harder to keep helium condensed for that same period. Hydrogen, as a light molecule, leaks out of any reasonably light gas cell--but again helium despite massing twice as much is, as a monatomic noble gas, even worse in this respect. Finally, using helium instead of hydrogen doubles the mass that has to be launched and sent to Venus and aerobraked into the atmosphere that serves as the lift gas too; for a space probe this may be the most damning argument against helium.

Another idea is to use some gas that can be shifted relatively easily between a liquid and gaseous state, back and forth, to achieve control of buoyancy. I'm not suggesting using such a substance as the main lift gas, but rather adding it on to serve as variable ballast. Water, which can be boiled into steam, is one example; in more or less Earthlike conditions (and there is a layer of Venus's atmosphere where temperatures and pressures correspond to Earth's surface conditions; above that of course the pressure and temperature drops much like on Earth except there would be no stratosphere layer of near-constant temperature since that is a result of UV forming ozone from Earth's oxygen) then lift from water is a function of power input to boil and maintain the steam in a vapor state. Ammonia, at almost the same molecular mass, is the reverse--it would require power to compress and cool it for liquid storage but would tend to form lifting vapor spontaneously. For second-stage Venus balloons, which would I suppose operate far above the surface, ammonia would be probably be best. (Note again that flammability, an issue in Earth's atmosphere though a relatively mild risk compared to hydrogen which is itself manageable, is on Venus no issue at all).

The neat thing about two-phase variable buoyancy is that while a light substance is desirable simply because it masses less, there is no need for the gas state to be actually lighter than the medium it floats in! What matters here is using a constant mass to fill a variable, controllable volume; the more of it is gas, the more atmospheric gas is displaced. One needs to be sure a major difference in density between gas and liquid state; substances near their critical temperature would not be very suitable. But if it turns out that the power requirements of compressing and maintaining as a liquid ammonia are high, perhaps some tailored chlorofluorcarbon might have better properties, even if the molecules are heavy.

If we have such a controlled buoyancy system to tip the balance set by a fixed quantity of lifting hydrogen, we might also, with a reserve of water, use solar power to split water molecules. Note that not only can we store the hydrogen produced with the larger volume of lift gas, but that oxygen, stored in another gas cell, would also be a lift gas, albeit a weak one, in Venus's carbon dioxide atmosphere. Thus we'd be raising the lift, but we could offset this by using more of the excess power being stored to condense some ammonia into its pressurized storage tank. When extra power for other systems is needed, we can run the hydrogen and oxygen through a fuel cell while boiling off some ammonia and running that vapor through a turbine--the ammonia cycle would be quite inefficient, in fact I guess the power that goes into condensing it is far in excess of what could be got back by boiling it, but the outcome is still significant power storage capacity. And we have a system in place for holding a reserve of lift hydrogen to replace what leaks out; we gradually drain the water supply (because we have to vent the excess oxygen to maintain neutral buoyancy) and when that is gone, the power storage is limited to batteries while we gradually lose ammonia since we then have to keep vaporizing more than we condense to replace lost hydrogen lift.

But with such systems in place, I'd think an upper atmosphere balloon probe could last for many years, as long as Mars crawler probes or longer.

At any rate, as long as it has solar power! It may be that drifting over to the night side is inevitable sooner than it will reach other limits. And to be sure we'd like to probe the night side upper atmosphere too. Here I think we'd have to work within the constraints of RTGs or conceivably small fission power plants.

The Chinese would have less trouble launching such systems than Western nations or even Russia would; quite bluntly they'd just ignore environmentalist protests if it suited them and no one has much leverage to change their minds if they decide to go with such nuclear systems. Obviously such things are still some years ahead and won't be included in the TL.

Exploring the surface itself is a challenge even with nuclear power; the problem is that there is no good heat sink--thermal power of any kind would have to run its hot side very hot indeed to use the prevailing atmospheric conditions as a heat sink!:eek: And this assumes that Terran engineers can design materials and electronics and machinery that can operate at those ambient temperatures--trying to use materials suited for Earth conditions means actively cooling them, again with no good heat sink.

For the very reason that the conditions are so very unEarthlike, I suspect we could learn some very valuable lessons if only we could get some kind of sustainable probe to work down there. I can think of combinations of buoyant and aerodynamic craft that could shuttle between the surface and aerostatic bases in the upper atmosphere, but it would be pointless to do so until we have some robots that can operate down there for long periods of time, using Heaven only knows what sort of power supply.

I wonder if microwave beams from orbiting or buoyant upper atmosphere solar collectors (or nuke plants) could serve?
Venus was the easier of the two destinations to reach in both time and energy
I was under the distinct impression that Venus required more delta-v than Mars. I'm wrong, am I?

tens of millions of millions of kilometers
redundant 'of millions'

金星 or Venus, right? Edit: oh, right, you say named after its target.
Why gloss it as 'golden star' instead of 'Venus'?

Solar sails! Yay!
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First, greet update on Planetary program!

I was under the distinct impression that Venus required more delta-v than Mars. I'm wrong, am I?

Mars got problem do it eccentric orbit, each 21 month, it launch window need different Speed to reach Mars at certain Date
you need less energy and get faster to Venus every 19 months, because it's circular orbit.
while Mars probe need 7-8 months to get there A Venus probe need only 4 month

金星 or Venus, right? Edit: oh, right, you say named after its target.
Why gloss it as 'golden star' instead of 'Venus'?

Solar sails! Yay!

wiktionary give for planet Venus on Mandarin Chines = Jīnxīng.
while Russian Venera means "Venus"
Morning all! I'm glad you enjoyed last week's image, it was one I was quite proud of. Expect orthogonal views of China's space station in the near future.
For this week's image we stay with the Chinese space programme, taking a look at their plans for exploring Venus.

Thanks for the kind comments! As promised, here are the Tianjia-1 orthos:


(Hmm, maybe the centre module should be rotated 90 degrees on its long axis to reduce shadowing from the other modules' solar arrays...)

I'm also planning to add this to the big spacecraft evolution image - but I'll probably wait for at least one more model before updating that.