Ad Astra — A History of Daitōjin Spaceflight -NO LONGER CANON-

[Daitō]

Ad Astra: Chapter One — Early Days

1945. The War to End All Wars, the Great War, is over. In the aftermath of the conflict, missile technology, once developed to bombard enemy cities, was repurposed for scientific advancement. Using the Shūkei ballistic missile as a sounding rocket, the Imperial Air Forces (IAF) began launching a series of payloads into the upper atmosphere and to the edge of space, performing a number of valuable experiments from their launch site in Western Tsukishima, the former Shiroi Sakyū Missile Range.

A Shūkei Sounding Rocket at Shiroi Shakyū Missile Range

Of course, Daitō was not alone in this endeavor, with many foreign powers also taking part in this early period of space exploration. However, as that is largely not the purview of this series, further detail will prove unnecessary.[1] Indeed, there were early proposals to use a Shūkei as a launch vehicle for a basic capsule in what was known as the Karura proposal. Such a plan was ignored owing to concerns that, at the time, the crew wouldn't be able to safely return to Mundus. However, while no man would fly into space in the late 40s, in 1947 a Shūkei Sounding Rocket would bring a bit of space back to Mundus, with the first photograph of the planet from beyond the atmosphere being released.

The Sky above Tsukishima, Shūkei No.17

As the 40s turned to the 50s, interest in the exploration of spaceflight seemed relegated to a niche community of scientists and military officers, with no truly groundbreaking changes coming for nearly a decade. However, in 1957, everything changed. With the launch of the first ICBM and later in the same year, the first satellite, paranoia gripped many a nation, Daitō included. If a foreign power could launch a satellite into orbit, then it was possible that they could launch nuclear weapons into orbit and leave them, allowing for them to strike at a moment's notice without any forewarning. With a burgeoning nuclear program (later to be cancelled in the early 70s), many within the Empire felt that it was necessary to match this feat. And so, on December 16th, 1957, the Daitō National Space Agency, or DNSA, was born. Their first mission? Put a satellite into orbit, which was no simple task. While the IDAF and IDN had programs to put a satellite into orbit as early as 1956, they were, by the end of 1957, still nearly a year away from completion.

It would be a tough call to make, but in April of 1958, the Navy's design, the Taimatsu, would be selected, with the IDAF's own Mori being put on the backburner until after its launch. And on the 11th of October, 1958, Daitō would join a growing number of nations to put an artificial moon in orbit. It would be joined by Mori-1 in November to much applause by the populace. But while the DNSA had proven itself capable, it had a long way to go before it was no longer hanging in the balance. After all, while from a strategic perspective such feats were important, many in the Diet saw it as an unnecessary expense that the IDAF or IDN could manage better.

Launch of Taimatsu-1, 11 October, 1958

1.	Owing to the fluid nature of the world, it is largely pointless to even try and chronicle such early flights by foreign powers.

[Daitō]

Ad Astra: Chapter Two — Suzaku Rising

In the years immediately following the launch of the first satellites, the DNSA was given a second, albeit less important, task to accomplish. The reigning Emperor in those days, Emperor Kunan, wished for a feat which had not been done before. He sought to put the first man into space, one not born on foreign soil, but a son of the Empire. And so, in late 1958, while Daitō was coming fresh off the heels of its first orbital launches, the DNSA announced its first class of spacefarers, the first ūchunauts. These were to be the best of the best, military test pilots who already put their lives on the line to evaluate new, experimental aircraft. In total, five would be picked, those being Kanji Akasaki, Akira Sagara, Banri Wakata, Iehiro Fujie, and Fumio Rinzaki. These five, the Suzaku Five as foreign media referred to them, stood a good shot of making it to space first, or so it was believed. After all, there were others working on the same goal.

Project Suzaku was, compared to future programs, rather simple. The task was to put a single man into orbit and return them safely to Mundus, using a converted Sekidō ICBM as a launch vehicle and a ballistic capsule as the crew vehicle. It was accompanied the IDAF's JT-16 rocket-plane program, with both aiming to put man into space. The JT-16 was a hypersonic rocket-powered aircraft that first flew in 1959 and continued flying until the late 60s, however it only made it past the Karman line during two flights in 1963. The Suzaku spacecraft, on the other hand, was far simpler, but would fly into orbit, with its first crewed flight planned August 1961. Many in the Empire thought they would reach space first, but once again, they were surpassed.

Suzaku and the JT-16

With pressure now on the DNSA to match the achievements of the outside world, the first crewed launch of the Suzaku spacecraft was set for the 19th of August. However, for nearly a week, the weather at Artsiv Cosmodrome proved unstable, and attempt after attempt was scrubbed. Finally, on the 26th of August, the first orbital flight by a Daitōjin ūchunaut would take place with the flight of Suzaku II, piloted by Kanji Akasaki. The flight lasted for six hours, completing six orbits in that timeframe. Like with the Taimatsu back in '58, the DNSA would be on par with the foremost powers of that day. Suzaku III, IV, V, and VI would, over the course of the next two-and-a-half years, push the limits of the spacecraft as far as possible, with the final flight, piloted by Fumio Rinzaki, lasting for just over a day.

Suzaku II in flight

With the conclusion of the Suzaku program, the DNSA now looked beyond Low Mundus Orbit, to the moon. Gone was the time of the Suzaku, now came the time of the Taka.

[Daitō]

Ad Astra: Chapter Three — Taka, Washi, and the Race to the Moon
I. Decisions

Following the success of the Suzaku program, the DNSA found itself uncertain of its future. While its neighbor, the Federal Republic of Rokkenjima, had declared its intent to land a crew on the surface of Luna, many in Daitō's aerospace community believed such a goal was, while worthy of great prestige, ultimately a fool's errand in the grand scheme of things. Rather, they believed that the DNSA should work to establish a long-term presence in Low Mundus Orbit by constructing a space station, however, Emperor Kunan saw the moon as a prize worthy of closing out his era. As such, the DNSA was directed to focus on landing upon the lunar surface in 1962, aiming to do so in late 1969. In spite of this, the space station program was also allowed to exist, albeit as a military-led program.

As part of the goal of landing on the moon, the Taka (Hawk) and Washi (Eagle) programs were approved, with Taka developing technologies necessary for landing on the moon and Washi actually achieving them. In 1962, the second group of Daitōjin ūchunauts, nine in total, were chosen for the Taka program, with some also taking part in the Washi program.II. The Taka Program

Early on in the development of the Taka spacecraft, many proposals were made for how to get the capsule into orbit and how to recover it. These ranged from the standard to, from the perspective of a modern observer, the downright strange. For launch, there were two front-runners, those being to launch it aboard a Sekidō-B ICBM or to launch it from beneath a B-81 Yoichi. Likewise, there were three major proposals for landing. These ranged from the standard spherical section heatshield seen on the Suzaku to a winged variant and even one that would land under a "rogallo wing", with the latter two landing at alternatively a runway or dry lakebed.

Illustration of a Taka spacecraft launched from a B-81

Ultimately, for the sake of safety, the Taka spacecraft would launch aboard the Sekidō-B and reenter the atmosphere much like its Suzaku predecessor. The first flight, Taka I, launched on the 8th of August, 1964, with the "spacecraft" being little more than a boilerplate, a mass simulator. The first crewed flight would not occur until April 1965, where a crew of two, led by Daitō's first ūchunaut, Kanji Akasaki, would spend a mere five hours in orbit. This would be Akasaki's only mission of the program, with many anticipating at the time he would be on one of the missions of the Washi Program. The mission would be followed up in July with Taka IV, which would see the first EVA by a Daitōjin spacefarer. Taka V would, by comparison, be considered far more boring, instead seeing the crew spend a week in orbit. Taka VI, by comparison, would be more significant, marking both the first major instance of cooperation between the DNSA and Tytor's own space program. It would see a Taka spacecraft rendezvous with a Tytorian micrometeoroid detection satellite, marking the first rendezvous by a Daitōjin spacecraft. The next two flights, Taka VII-A and VII-B, would likewise prove important, demonstrating rendezvous between two crewed spacecraft as well as an EVA by two individuals. It would likewise be followed by Taka VIII, which saw the first docking by the DNSA and by Taka VIX, which would have the spacecraft be boosted to a highly eccentric orbit with an apogee of 1,100 km. With its completion, the Taka program would come to an end and the Washi program would begin.

Taka VI launch

III. The Washi Program

The Washi Program dates back to roughly the same time as the Taka Program, owing to them being approved in the same year. The Washi Program was intended to be Daitō's effort to put a man on the surface of the moon by the end of the decade, however, delays led put such a goal into doubt. Originally, it was hoped that the first manned flight of the program could occur in 1966, immediately after the end of the Taka program. However, owing to these delays, the first launch of the program would only occur in 1967. The first crewed mission of the program, Washi II, was meant to occur in march of that year, with the crew lifting off the pad on the 21st. However, the mission would fail shortly after liftoff with the loss of the booster, forcing an abort. The crew of three was badly injured, with all of them save the commander, Iehiro Fujie, retiring later that year. It was determined that the issue was caused by a faulty pump in one of the rocket's thrusters, with this fault being corrected in the others. However, as a result of this, as well as the DNSA wishing to change course, negotiations began behind closed doors to license the Atlas spacecraft and rocket for Daitōjin use.

Washi III on the pad

In spite of efforts by the DNSA to move away from the Washi spacecraft and by extension, the program which spawned it, the agency found itself under political pressure to move forwards. As a result, while they would quietly cancel further orders of the spacecraft, they would proceed with the lunar program for seven additional flights, starting with, after yet more delays, Washi III. Unlike its predecessor, the third mission of the program would be a total success, with the crew spending a week in orbit before returning safely home on the 10th of April. it would be followed by Washi IV, which would test the lunar lander in Low Mundus Orbit before, in early 1969, the crew of Washi V would orbit the lunar surface. Akira Sagara, who had been on this mission, is quoted as saying the following:

As I looked up upon our fair world from afar, I felt a distinct sense of unity with all of humanity. As though every life that had been lived had led up to this moment, where we three intrepid explorers could see where all of mankind had been born."

Washi VI launched in April of 1969, carrying ūchunauts Fumio Rinzaki, Hiroji Fukai, and Goro Haku to lunar orbit alongside their lander for what was meant to be a final test before a prospective landing in July. While the mission itself was a success, with the lander coming as close as 15.6km of the surface before returning to the command module. Everything seemed nominal from the moon to reentry, however, it was far from normal. It started with a failure by the crew to regain communications, however, soon the carrier that was set to recover the spacecraft saw a grisly sight. As one sailor aboard the carrier, the IDN Hidaka, remembered,

"There was much abuzz on the bridge as we fought desperately to find the spacecraft. Then, a fellow sailor shouted something, 'By the Spirits, she's burning.'

What the crew saw was the capsule breaking up over the Kynean Sea, the result of a flaw in the heatshield which extended to the remaining batch. There was no hope for the crew of three to survive. Practically overnight, the Washi Program was as dead in the water as the crew which had lost its life. With this outcome, for two years, Daitō was back to being a purely satellite-based space agency while the Ryū Program began to gain traction.

[Daitō]

Ad Astra: Chapter Four — The Dragon and the Heavenly Palace
I. The Ryū Program and LEM-Lab

The Ryū program was a six-year program lasting from 1971 until 1976. Making use of licensed technology from Tytor, it allowed for the DNSA to maintain a presence in Low Mundus Orbit into the 1970s, even as the UHS Program kicked off in development. Key to this program was the Ryū spacecraft and the Tenjin rocket family, which were iterations of the Tytorian Atlas spacecraft and rocket family. Despite this, the Ryū spacecraft had a number of differences from its Tytorian counterpart, most notably the usage of a Nitrogen-Oxygen mix instead of a pure oxygen environment inside the spacecraft. The first manned flight of the program occurred in 1971, when a crew of three performed a flyby of Luna, even as Rokkenjiman astronauts walked upon its surface. Apocryphal stories tell of how the crews greeted each other, however no record on either flight backs this up. A further two flybys occurred in late 1971 and early 1972, after which the Daitōjin lunar program, at least for the moment, came to an end. But though the first half of the Ryū program was at its close, the program as a whole was not.

Artist's conception of the Ryū Solar Telescope

Moving its focus to Low Mundus Orbit once more, the DNSA saw fit to figure out how to live in Space. While Emperor Kunan had sought prestige, his successor, Emperor Daiwa, instead allowed the DNSA to focus on this goal which they viewed as more important, after all, more could be learned from six months in orbit than a few hours on the lunar surface. As a start, the DNSA contracted the manufacturer of the Atlas lunar lander to make a modified lander that would serve as a basic space station or a man-tended Space Telescope. The Ryū Solar Telescope, often known outside of Daitō as LEM-Lab, was born. The RST was, by comparison to later stations, quite small, being only slightly bigger than the standard Lunar Module. In many ways, it straddled the line between a docking target and a proper space station, as it allowed the crew to access it, but their tasks aboard were rather limited beyond operating the telescope. For a period over the course of late 1973 and early 1974, the RST would be operated by the DNSA prior to the launch of Kyuden, the Palace in the Sky.II. Kyuden, our Home in Space

Compared to the Ryū Solar Telescope, Kyuden was a veritable mansion. Made of a converted Tenjin V upper stage, it featured a derivative of the RST as one of many experiments to be used onboard. With a pressurized volume of 361 cubic meters,  it was nearly 54 times as massive as its predecessor and was capable of, at the time, hosting crews for up to three months at a time. However, it would have to be launched before it could actually be used, and so, Kyuden was set to launch in June of 1975. Delays did occur due to Tropical Storm William affecting the east coast of Tsukishima, however, and it would instead launch on the 6th of July, 1975, drawing crowds from across the Empire and many people from beyond as well.

Launch of Kyuden

Although the launch seemed to have gone well, in reality, as soon became apparent, something had gone wrong with the station. Now, the crew of Kyuden II, ūchunauts Haruto Adachi, Ginji Yabuta, and Takauji Yanagida would essentially have to race to rescue the stricken vessel, which meant a much harder mission than previously anticipated.
IIa. Kyuden II

Kyuden during a flyaround inspection, 11 July, 1975

As crews on the ground practiced a variety of methods to repair the stricken space station, the crew of Kyuden II arrived on the scene. There, they found that one of the "Solar Wings", as well as the micrometeorite shield, had been ripped off during flight, and that the interior of the station was much warmer than was safe for extended habitation, reaching up to around 52°C.  This was a problem that had been anticipated following the launch of the station, so prior to the crew's launch they were given a sort of parasol to cool the station. Working in turns over several hours in the station's searing heat, eventually, the crew would successfully deploy the parasol through the station's upper science airlock. Slowly but surely, the temperature would drop from such a high to about 28°, allowing for the crew to comfortably work in the station. With the temperature now under control, the crew had a much bigger issue to solve, that being the second solar wing, which had failed to fully deploy.

Haruto Adachi and Takauji Yanagida work to free Kyuden's solar wing, 1975

This task, unlike the previous one, was much more difficult given that the solar panel was in a place which had no railing, no lighting, essentially where no crew member was ever meant to go. And yet, they had no choice but to do so. It was this task that crew and its backup found themselves working on in the DNSA's neutral buoyancy tank prior to launch, trying to find a way to release the solar panel without risking the loss of the station. The solution they came up was unprecedented. For the first time, a crew would have to perform repairs in orbit, something that had, up until that point, not been done before. The solar panel had become jammed by a small piece of metal which had to be cut so that it would open. Taking a tool that looked essentially like a tree limb cutter, they would free the solar panel, which opened with enough force to fling them off the hull. This did little but test their nerves and the strength of their tethers, and after regaining their composure, the duo would return to the inside of the station.

Space Station Kyuden in early 1976

With the solar array deployed, Kyuden was finally open for business, with the first crew, Kyuden II, returning home in late August. Following this, the station would be visited by three more crews, those being as Kyuden III, commanded by Kanji Akasaki, Kyuden IV, which was commanded by Takatsugu Konishi, and Kyuden V, whose commander, Hayao Suyama, would be the last to enter the station for many years. With the departure of this final crew, the station would go dormant, awaiting its next crew which would bring it into a new era. But that was something that would come in many years, for with the end of the Kyuden V mission, the Ryū program had come to a close. Gone was the Ryū capsule, closing another chapter in the long march of progress. Now, the page turned on the UHS program, which was soon to enter flight testing.

[Daitō]

Ad Astra: Chapter Five — Probes of the 1970s
I. Lunar Missions
The 1970s saw, alongside a shift in the focus of the DNSA's manned program from lunar exploration towards a sustainable Low-Mundus Orbit presence, a number of robotic missions that explored the Solar System. These included probes to Luna, Ishtar, Nergal, and the Outer Planets. Starting out, we will discuss the continuation of the DNSA's Tsukuyomi program which started in the mid-1960s. In 1970, Daitō launched the Tabibito rover, which, as part of the Tsukuyomi program, would land near the limb of the moon, that is, the edge of the light side of the lunar surface. The Tabibito rover would remain online for just shy of a year, travelling some 10.5 kilometers while it could. To this day, Tabibito, while unable to conduct experiments or drive on its own, provides valuable data through Mundus-based Lunar Laser-based Rangefinding experiments.

Artist's conception of the Tabibito rover

The Tsukuyomi program reached its peak with the Tsukuyomi-11 mission, which successfully returned samples to Mundus after landing on the lunar surface in 1974.II. Missions to Nergal
Perhaps one of the more obvious targets for robotic exploration in those days was Nergal, which, being one of the closest planets to Mundus as well as the easiest, at least compared to Ishtar, proved a tempting target. While flybys had been performed in the 1960s, it was in the 1970s that exploration of its surface really kicked off. Most notably, in 1975, the final Tenjin V rocket lifted off from LC-17A at Artsiv Cosmodrome, carrying the twin Kirin probes and an orbiter into LMO. Using a Misaki upper stage, it would then be injected into orbit around Nergal, arriving in 1976. The probes would land a month later, operating for roughly five years before loss of signal in 1982.

Artist's conception of a probe in the Kirin Mission to Nergal

III. Missions to Ishtar

Photo of Ishtar's surface, Kinsei 8, c.1975

Compared to Nergal, Ishtar proved a more challenging destination owing to its dense atmosphere, extreme pressure, and heat. This meant, for the most part, that the DNSA's exploration of the planet was done from orbit, however, three spacecraft would attempt to land on the planet, those being Kinsei 7, 8, and 9. Of these probes, only Kinsei 8 would be able to take photos, as 7's lens cap didn't deploy and 9's camera melted through due to a flaw in its construction. As for the orbiters, they would perform a number of survey missions from 1974 until 1978, assisting in mapping the planet's surface, although to a very limited degree.IV. The Grand Tour, Part One

Kōkaisha-1 flies by Marduk, c.1979

As early as 1964, there were proposals for missions which would extensively explore the outer solar system. Such missions would, in theory, see a series of four spacecraft perform flybys of Marduk, Ninurta, Anshar, and Kishar. However, due to the enormous cost at the time, such a proposal was declined, and instead, two spacecraft would fly in what became known as the Kōkaisha program, however, the name "Grand Tour" stuck outside of Daitō. The program was approved in 1972, being built by the DNSA's Yuzawa facility for longevity, allowing it to accomplish the same goals as the older Grand Tour proposal with only the two spacecraft. The first of these spacecraft, Kōkaisha-1, would only fly by Marduk, Ninurta, and one of Ninurta's moons, while the second, Kōkaisha-2, would preserve the Grand Tour Mission Plan, visiting Anshar and Kishar as well as Marduk and Ninurta. Kōkaisha-2 would launch in September of 1977 while its successor and also predecessor, Kōkaisha-1, would launch the next month. The two probes would fly past Marduk in 1979, after which they continued on their way towards a flyby of Ninurta in 1980. However, that is a story for another time.

[Daitō]

Ad Astra: Chapter Six — Enter the Mizuchi
I. A Matter of Design
The UHS spacecraft, which came to define the DNSA for the last 40 years, finds its origins in the 1960s as a reusable crew and cargo resupply vehicle for orbital space stations. Due to the relative cost of it compared to the rest of the proposal, it was the only part which would actually receive funding. Approved in 1971 as an eventual replacement of the Ryū spacecraft, development would quickly begin. There were many proposals for it, from what we got, the Tenjin-UHS system, to the different, such as Thrust-Augmented Orbital Vehicle (TAOV), to the more insane such as an SSTO and a two-stage-to-orbit vehicle which would've been, at least in theory, usable as a passenger vehicle allowing point-to-point travel across the globe. Initially, the DNSA wanted something resembling two aircraft attached to one another, with the spacecraft hanging off the side while both would be fully reusable. However, when the State Ministry of Defense (SMoD) became involved, due to its desire for a spacecraft with higher cross-range (polar missions would've ultimately meant that otherwise, the spaceplane would land in the sea) and higher cargo capacity, that proposal was dropped and Tenjin-UHS and TAOV became the frontrunners.

The original UHS proposal

The Thrust-Augmented Orbital Vehicle concept, which closely resembled the modern Tytorian Space Shuttle, would've involved the DNSA making use of Liquid Rocket Boosters (LRBs) and firing the UHS's main engines from liftoff. This would've required the development of an entirely new launcher alongside the orbiter, as well as completely new infrastructure to go alongside it. By comparison, the Tenjin-UHS proposal would've only required the development of the external fuel tank and the orbiter, would've allowed the DNSA to maintain, at least on paper, super-heavy lift capability, and would've, at least in terms of the costs for infrastructure, been cheaper. The problem with that design being that the Tenjin first stage was comparatively expensive, although there had long been proposals for reuse of it. Ultimately, the Tenjin-UHS concept won out, with TAOV being tossed aside.

TAOV

With the Tenjin-UHS concept winning out, was given the name Mizuchi, or Sea Dragon, in a way hearkening back to the older Ryū program that it was replacing. Having been selected, the Mizuchi concept would evolve, featuring two phases, those being an early period where it would launch on simply a refurbishable Tenjin first stage and a second where it would fly aboard a variant of it which would be capable of flying back to the launch site. This decision was made as it was not expected that the flyback booster would be ready at the same time as the shuttle, which would mean that unless they flew on a more simple version of the Tenjin first stage, it would be able to fly until 1986, well after Kyuden, which was deemed a priority target for continued habitation, would've deorbited. And so, the DNSA went on its way, preparing for the first launch nearly a decade ahead.
II. Approach and Landing Tests
By 1972, the design of the Mizuchi-class orbiter had pretty much been worked out, the funding had been granted to actually start building it, and the DNSA got to work. But there was a problem, and a pretty glaring one too: The DNSA hadn't actually built a spaceplane before. Sure, they had built a few spacecraft, but flying was new to them. Sure, part of their task was aeronautical research and they had run or participated in numerous studies of exotic aircraft, such as the JT-16, but it remained a fact that the DNSA nor anyone else had ever flown a winged vehicle down from orbit to a runway landing. When it was time for the orbital test flights, planned for 1979, nobody was wanting any surprises when it came to the actual flight characteristics of the orbiter. Enter the Approach and Landing Tests, or "YCT" program (YCT being the acronym for Approach and Landing Test in Onishic languages). Mizuchi, despite being arguably among the most beautiful flying machines to ever take to the air, wasn't noted for flying nearly as well as most. One pilot remarked that it "was like flying a brick with wings", owing to the delta wing being poor at generating lift at low altitudes while being great at higher altitudes. The vehicle's glide-slope angle was 20°, as compared to a modern passenger jet which has a glide-slope angle of around 3°. In effect, it was as though the vehicle was flying straight down. Adding in input lag and a few other unique (for the time) characteristics owing to its delta wing, and it proved to be a difficult bird to fly, and because of that, there was absolutely no margin for failure. Without any engines, there was only one chance to land, and it would only be at 584 meters that the commander would pull back on the control stick, flaring the spacecraft and bringing it in for a gentle landing, for a spacecraft anyways, which is to say about 90 meters per second. Because of this, the DNSA needed a way to test the orbiter, and in a safe, controlled environment closer to home, and for that, it needed an orbiter ahead of schedule: KS-101

US-101 is the official designation of Shirotsuru. "KS" is an acronym for "Kidō Sharyō", or in English, Orbital Vehicle, while the "101" informs of its intended purpose. As the first number is a 1, that designates it as being intended for orbital spaceflight, while a 0 would mark it as a test article. The "-01" means that it was the first vehicle, owing to the orbiters being one-indexed instead of zero-indexed. Before it could earn its designation as an orbiter, however, it would be put through its paces in a mundus-bound configuration. The plan was to make a vehicle that looked like an orbiter and worked like one, albeit only in the final part of its mission, that being the roughly five minutes before landing when the vehicle would fly around, line up its approach, and land at the runway with precision. This meant, in lieu of actual ET-21 MMEs (Mizuchi Main Engines), wooden replicas would be used alongside ballasts to make up the weight. Instead of heat-resistant tiles, there were basic tiles that simply looked like the real ones. And of course, instead of reinforced carbon-carbon for the nose and leading edges of the wings, fiberglass was used. Though it may not have looked it, however, US-101 was very much a real orbiter, running the latest available software on its computers, used fuel cells to provide power, and had functioning control surfaces and landing gear.

When US-101 rolled out on the 19th of August, 1976, it was the public's first glimpse of at the DNSA's future, and by February 18th of the next year, said future would take to the skies. This initial period of testing would last through February until early March, during which time it first completed three taxi tests, that is to say, rolling it out to the runway aboard its carrier aircraft, then a series of captive flights during which time it would remain uncrewed and inert, concluding on the 6th of March. In May, it would enter its captive-active flight testing, being piloted by two crews. These crews were made of two ūchunauts, the first having Daisuke Abeno and Katsushi Odagiri, the second Satoru Daigo and Eita Fuyuki. And then, finally, it would come time for the White Crane spread its wings and flew on its own.

Shirotsuru performs its first free flight, 12 July, 1977

Flown by Crew 1, Shirotsuru soared through the skies over Shiroi Shakyū Air Force Base independent of its carrier plane for the first time on the 12th of July, 1977. Beginning at 9:41 in the morning, local time, the orbiter, spent nearly fifty-four minutes in flight, still mated to the carrier plane as it climbed to an altitude of 7,364 meters before releasing from it at 10:34 AM. Upon separating, it spent another five or so minutes gliding back to the surface, landing at a dry lakebed at 10:39 AM. This flight, YCT-12, alongside YCT-13 and 14, would make use of an aerodynamic tail-cone, which was designed to lower drag aboard the MCA (Mizuchi Carrier Aircraft). The next two flights would lack this, with the final YCT flight, YCT-15, also being the first to land on a runway. With the completion of the Approach and Landing Tests, Shirotsuru would be packed up and delivered first to the Dynamic Structural Test Facility on the mainland, where it was mated to a mockup of the launch configuration and underwent vertical ground vibration tests. Following this, it was delivered back to Tsukishima, this time to Artsiv Space Center, in order to test the procedures of assembling a stack inside the Vehicle Assembly Building (VAB). Once stacked, it would undergo fit-checks before being rolled out to LC-17A for a wet dress rehearsal. Once this was finally complete, the vehicle would be rolled back to the VAB, destacked, and US-101 sent to be inspected and considered for retrofit into a fully operational orbiter.

The Mizuchi spacecraft was ready, at least, for the final five minutes of a flight.
III. The Road to UHS-1
For as difficult as the Approach and Landing Tests were, the final landing was among the easiest parts of any UHS mission. An unflyable brick was something that most skilled test pilots could handle, usually. But the rest of the mission was something entirely new. If an orbital UHS mission was to be successfully completed, there were numerous mechanisms, input devices, and subroutines that had to always perform flawlessly. But more than any other, there were three parts that stood out. One was a challenge that any rocket scientist or engineer was acutely aware of. Another was familiar, but cranked up to eleven, both in regards to its complexity and its central role in the mission. And one was new, exotic territory that the DNSA only hoped they could figure out in time. These were, in that order, the engines, the tiles, and the computers. Compared with some spacecraft, the UHS had a relatively trouble-free development, but that is not to say it was perfect all the way. When work began in 1972, the plan was to fly the first orbital missions sometime in 1979. But since UHS-1 didn't fly until March of 1981, it would be clear to any observer that there were some notable bumps that were encountered on the road. Of course, these were resolved before the orbital flight test, however, a more literal bump occurred when, in 1979, the first orbiter set to fly into orbit, Tenryū (US-102), lost nearly 5,000 tiles during delivery to Artsiv. As a result, these would have to be reapplied, leading to a delay until 1981, when at long last, the UHS program saw its first flight.
IV. UHS-1, the Greatest Test Flight
Finally, on the 16th of March, 1981, the first orbital flight test of the Mizuchi spacecraft was to be performed. While any first flight of a spacecraft is notable, UHS-1 was even mores so, given that, unlike most any others, it flew with its crew aboard. Typically, a new spacecraft would be flown without its crew at least on its first flight, if not its first two. However, the DNSA ruled, owing to its complexity, that it would be more likely to succeed if it had the crew aboard. Another reason that the vehicle flew with people aboard was because, simply put, the ūchunauts lobbied hard for it. Finally, if it launched without a crew on a test flight, many in the DNSA believed it would only be a matter of time before it would fly an operational mission without one, making the idea of putting crew aboard the vehicle entirely redundant. With the ūchunaut office not liking the precedent it may set, they wanted a crew aboard it from day one. And a final reason, although more speculative, may be that the DNSA wished to compare it to similar winged vehicles. After all, nobody would bat an eye if a fighter jet flew with a crew on its first mission, same with a passenger liner. In many ways, the DNSA wished to frame the Mizuchi less as a limited, experimental run and more as something routine. As such, UHS-1 would have a crew. But if something went wrong, it was only logical to have a backup, so for it and the three other test flights, the crew would have ejection seats, at least so that they could survive if the orbiter couldn't. And if it could survive, then the first stage could be throttled down, the Shuttle could then separate from the first stage, then perform a return to launch site (RTLS) abort. If that wasn't possible, then a Trans-Oceanic Abort (TAO), Abort Once Around (AOA), or Abort To Orbit (ATO) could be performed as well. Of these, an Abort to Orbit was the most desirable, followed by Abort Once Around, followed by Trans-Oceanic Abort, then finally a Return to Launch Site owing to how absolutely insane it was. In an RTLS abort, the crew would, as previously mentioned, separate from the first stage, after which they would, while the main engines were still running, slowly pitch over, essentially going vertical and then facing completely backwards in order to cancel out their horizontal velocity, allowing them to shut down the engines and ditch the external fuel tank. But given that normally you wouldn't ditch the fuel tank in the atmosphere, the crew would have to be more dynamic. They would have to pitch down, punch the ET SEP button, then pitch back up, essentially throwing the external tank off of them. And to briefly mention it, during all of this ordeal, they would be firing the OMS (Orbital Maneuvering System) in order to try and burn off fuel and lower their landing weight. Once the ET was gone, the crew would glide back to Tsukishima for a nominal landing. There were some tentative proposals to do an RTLS abort as a test, however, Kanji Akasaki, the commander of UHS-1, flat-out refused that option. As he was quoted about how he felt about the maneuver, he called it "Six miracles followed by an act of god." Another quote had a technician asking Akasaki what displays he wanted during an RTLS abort. Akasaki said he "didn't care" since he'd, and I quote, "be covering my eyes and going 'Ahhhhhh!'". One might ask why Akasaki had any say in this matter, which can be answered quite simply. Since his previous flight, back in the 1970s, he had moved up in the ranks, becoming the chief of the ūchunaut office and was commanding UHS-1.

And so, with every option considered, UHS-1 would lift off to much fanfare on the 16th of March, 1981. The spacecraft would spend two days, four hours, and sixteen minutes in flight, landing at Shiroi Shakyū AFB on the 18th. The greatest test flight had come and gone, and the door to the future had opened.

View of Tenryū's Payload Bay, UHS-1

Landing of UHS-1, 18 March, 1981

[Daitō]

Ad Astra: Chapter Seven — Golden Age of the Mizuchi Program, Part One — Early Days
I. Stationkeeping and further testing
Following the success of the UHS-1 mission in 1981, preparations were quickly underway for the second test flight, UHS-2. Launched just over eight months after UHS-1, its target was Daitō's old space station, Kyuden, with the goal being a simple rendezvous as well as a test of the vehicle's Remote Manipulator System, or RMS. UHS-2 had a secondary purpose, that being to deploy the Teleoperator Retrieval System (TRS), an uncrewed robotic space tug designed to be capable of remote payload observation and boosting or de-orbiting of other spacecraft. While its primary mission would come to be to reboost the station, the TRS would, after completing this task, be maintained at the station for once crews started inhabiting it once more, where it might serve to aid crews aboard with repairs, allowing ground control a view of spacewalks. Thus, the mission would launch on the 18th of November, 1981 with a crew of two, with the mission lasting for five days and six hours, after which the vehicle landed at Shiroi Shakyū AFB.

The TRS deployed from Tenryū.

The following test flights, UHS-3 and UHS-4, would in comparison be overshadowed by their predecessors. The former, UHS-3, would test the orbital endurance of Tenryū, launching on the 11th of March, 1982 and landing eight days later on March 19, 1982. Other primary objectives included further testing of the vehicle's Remote Manipulator System (RMS) and carrying out extensive thermal testing of Tenryū by exposing its tail, nose, and top to the sun for varying periods of time. The crew found that prolonged exposure to the sun caused the cargo bay doors to warp slightly, preventing them from closing fully. Rolling the orbiter to balance temperatures around the vehicle resolved this issue.

In addition to thermal testing, Tenryū carried a Development Flight Instrumentation (DFI) package and a number of instruments mounted onboard a Chiheisen pallet, intended to obtain data on the near-Mundus environment and the extent of contamination caused by the orbiter itself. This pallet also contained an X-ray detector for measuring the polarization of X-rays emitted by solar flares. For the first time, a number of experiments were also carried in the orbiter's mid-deck lockers. These included an Electrophoresis Equipment Verification Test experiment to study the separation of biological components and a Mono-disperse Latex Reactor experiment, meant to produce uniform micrometer-sized latex particles. The first Mizuchi Student Involvement Project (MSIP) - a study of insect motion - was also carried aboard.

Although the mission was planned originally for seven days, bad weather at the vehicle's landing site meant that reentry had to be postponed for almost a day. By comparison, UHS-4 was more mundane, performing the first "Getaway Special" payloads, which included nine scientific experiments provided by students at the University of Tenkyō, as well as a classified Imperial Daitōjin Air Force payload of two missile launch-detection systems, although said IDAF payload failed to operate. The payload carried within the orbiter's mid-deck lockers was largely the same as onboard UHS-3, although the crew performed a lightning survey with hand-held cameras and performed medical experiments on themselves for a pair of student projects. The crew also operated the RMS with an instrument called the Induced Environment Contamination Monitor mounted on its end, designed to obtain information on gasses or particles released by the orbiter in flight. The mission, which launched on the 16th of July, 1982, remained in orbit for seven days and sixteen hours, landing Shiroi Shakyū AFB on the 23rd of July, 1982. With the completion of this mission, the UHS program was declared ready, the ejection seats aboard Tenryū were deactivated, and plans went forwards with a greater launch schedule than seen before.

Tenryū lands at Shiroi Shakyū AFB, 16 July, 1982

II. A most beautiful undertaking
With the successful completion of the testing phase of the UHS program, a number of missions opened up. Due to the volume of such flights, however, only the most notable of these flights will be mentioned. In spite of this, as a result of the large number of missions in the 1980s, many have come to refer to the decade as the golden age of the program. With 56 missions launched between 1981 and 1990, roughly 1,852 hours were spent by Mizuchi vehicles in orbit in the year 1987 alone. Nonetheless, with that out of the way, we can move on to discussing individual missions.
IIa. UHS-5, 6, & 7
The first officially "operational" mission of the UHS program, UHS-5 was launched on the 6th of November, 1982. UHS-5 was the first Mizuchi mission to deploy communications satellites into orbit as well as the first to have an attempt at an EVA performed from the vehicle, although due to technical issues with the suits, they were later called off. UHS-5 carried a Vanoran-sponsored microgravity Getaway Special experiment cannister in the payload bay, and the crew also conducted three student-designed experiments during the flight. As for the EVA, it was originally delayed by one day due to an ūchunaut suffering from motion sickness. A poorly functioning oxygen regulator in one member of the EVA team's suit and a broken recirculation fan in the other's caused them to cancel the EVA entirely, marking the first time that an EVA was cancelled due to issues with a space suit. UHS-5 landed on Runway 22 at Shiroi Shakyū on the 11th of November, 1982.

UHS-6 was the maiden flight of Sōryū (US-103), originally scheduled to launch on the 12th of January, 1983. However, due to issues with the MMEs, its launch was delayed until 3 April 1983. UHS-6 was the first mission to deploy a Tracking and Data Relay Satellite (TDRS), part of the larger Tracking and Data Relay Satellite System (TDRSS), which is a network of Daitōjin communication satellites and ground stations used by the DNSA for space communications. While primarily used by the DNSA, its international partners also have the option of making use of such networks. UHS-6 was also the first time a Mizuchi spacecraft launched from Launch Complex 17B, as well as the first mission to see an EVA performed from the orbiter following the incidents aboard Tenryū during UHS-5. TDRS-I, the payload on this mission, was deployed on flight day two, making use of its Inertial Upper Stage (IUS) to put it into a geosynchronous orbit, while on flight days three and four, the crew undertook the first EVA from the orbiter.

TDRS-I is deployed

First EVA from a Mizuchi orbiter

UHS-7 was notable for a different milestone, not a particularly important one from a scientific perspective but from a social perspective, remarkably important. For the first time, a female ūchunaut from Daitō, Haruka Sadanaga, would fly into space. Of course, UHS-7 also featured the first deployment and recovery of a Mizuchi pallet satellite (MPS), as well as the first time a crew larger than four would fly into orbit aboard a Mizuchi spacecraft. A crew of five would go on to become the standard compliment, featuring a commander, pilot, and three mission specialists, although there would be many missions which would exceed that number and some that would be lower. UHS-7 would also see the deployment of a pair of communications satellites, one for the Allied States of Ardia and one for Daitō. The mission would last six days, launching on the 15th of June, 1983 and landing on the 21st.

Sōryū as viewed from MPAS-1

IIb. Kyuden-VI
Following the successful re-boost of Kyuden during the UHS-2 mission, it was planned that the station would, at least initially, serve as a man-tended orbital workshop, much like it was in the 1970s. However, in order to facilitate this, it was deemed necessary that a docking adapter of some form would be necessary, owing to a lack of clearance between the two buildings. Said adapter would open up the possibility of two or more vehicles to be docked to the station at a time, thereby making it possible to both maintain a permanent presence in LMO and to further expand the already large station. Therefore, it was planned to initially use the station in order to extend the shuttle's capabilities, originally up to 1985 but later delayed until 1987. However, on the 23rd of August, 1983, the first docking of the UHS program, UHS-8, occurred, beginning the Kyuden-VI mission. Lasting for seven days from the 21st of August, the crew would inspect the station's condition, both from the interior and the exterior, determining what would require refurbishment before performing what experiments they could with the Ryū Telescope Mount.

UHS-8 docked to Kyuden

With the success of the UHS-8 mission, the door was open to maintaining a permanent presence in orbit. But now, it was necessary to develop a way of getting home, should something happen.(Author's note: Names and Abbreviations are translated into English for your sake)

[Daitō]

Ad Astra: Chapter Eight — Golden Age of the Mizuchi Program, Part Two — Making spaceflight routine
I. Friends in High Places
When discussing the Mizuchi program, it would be a disservice to everyone involved to refer to it as a purely Daitōjin program. Hundreds of thousands of people from many nations around the globe worked on it, and many more were affected by the discoveries that were made during its long lifespan. But notably, as far as this series is concerned, there were many from these nations who flew aboard an orbiter, starting in 1983 with UHS-9, the flight of Ardian Astronaut Michel Lémieux. Future flights included crews from Tytor, Vanora, Volhynia (after 2006), and Heyra, among many others. As such, it only seems fitting to begin by discussing UHS-9, the first flight of the Chiheisen laboratory. The Chiheisen module was essentially a miniaturized space station mounted within the orbiter's payload bay. The Mizuchi spacecraft was more than capable of playing host to such a complex payload, and Chiheisen was able to focus less on basic infrastructure that just kept its hardware alive and more on the science experiments inside. However, more information on the module will be provided when it becomes relevant on its first flight.

The scope of the UHS-9 mission was one that is quite familiar for those steeped in early Mizuchi history. While there were dozens of experiments to perform, the real objective was essentially a shakedown test-flight. This spacecraft inside of a spacecraft, which sometimes got compared to a matryoshka doll by Volhynian crews that flew aboard, was a complicated machine, featuring a number of different mechanisms, interfaces, and procedures to check. Due to it being its first flight, the DNSA and its foreign partners didn't want to commit too many resources to critical experiments that could be blown out of the water by a simple problem. It was better instead to shake out the bugs beforehand, they figured. But this wasn't the only bit of new hardware that was flying on this mission.

Having flown five missions in a row, Tenryū was taken out of the flight rotation for a brief period of time in order to undergo some modifications. Given that the list of modifications could go on for ages, only a few highlights will be mentioned. The three MMEs used were taken out and replaced with new, improved ones that were rated to run at 104% of the normal rated thrust levels. The engines that they replaced would not go to waste, however, and would instead be upgraded and installed on another orbiter. Extra seats, headsets, and emergency oxygen supplies were added to support larger crews. The upper windows in the flight deck were modified for emergency crew egress while on the ground, including some devices affectionately referred to in foreign press as "sky genies", which would essentially be put on a rope to allow someone to slowly winch themselves down to the ground. A sleeping station was added to the starboard side of the mid-deck, allowing further space for a crew of three to rest in while the rest of the crew was on duty. A galley and a hygiene station were also installed on the mid-deck, providing further amenities for the crew. Finally, a ku-band antenna was installed in the payload bay, allowing the orbiter to "talk" to TDRSS.

The crew of UHS-9 marked a few spaceflight firsts. Firstly, although perhaps the most mundane, was the crew size, which was bumped up to six, up from the previous record of five set on UHS-7. Another first was that this was the first Mizuchi mission to fly with payload specialists. On that note, a brief bit of information on roles of crewmembers aboard a UHS spaceplane proves itself necessary, owing to said roles essentially remaining the same into the modern day. Up at the front, you have the pilot ūchunauts, the commander and pilot. Somewhat counterintuitively, the commander flies the spacecraft while the pilot is essentially a co-pilot, but given that ūchunauts typically don't like being called co-pilots, the name stuck. These are DNSA-employed career ūchunauts, with their role being to get the vehicle safely to and from orbit, as well as keep an eye on all systems aboard in the meantime. The second type of ūchunaut aboard the spacecraft is the mission specialist. These are also DNSA-employed career ūchunauts who are particularly focused on the specifics of the mission at hand. Some may have sub-specialties, such as operating the RMS, performing EVAs, or working on specific types of experiments, but essentially they are intelligent and capable people who have completed the years of basic ūchunaut training as well as have trained for every detail of the mission at hand. When they land, both the pilots and mission specialists will typically go back into the general pool and serve in support roles while they await another flight assignment. The third type is the type that we see for the first time on UHS-9: Payload Specialists. These are non-ūchunauts who do not work for the DNSA, and are instead brought in because they have some form of special expertise with a very specific aspect of the mission, with many only flying once. It was this role that allowed foreigners, at least initially, to fly aboard the spacecraft, although in time seats would also be purchased.

On UHS-9, the commander was the one and only Kanji Akasaki, Daitō's very first ūchunaut. Having flown on four separate types of spacecraft and six missions over the course of his career, this was his last mission before "retiring" back to his old job as the head of the DNSA's ūchunaut office, after which he would truly retire in 1990. Still alive to this day, Kanji now spends his twilight years as an author and motivational speaker. Flying alongside Akasaki and serving as pilot was fellow Ryū veteran Takauji Yanagida, who had, prior to his selection in 1968, served in the Imperial Daitōjin Air Force out of Volhynia. This was to also be his final flight. Joining them were the two mission specialists, Dairoku Arisawa and Daitō's second female ūchunaut, Michie Sekizuka. Down on the mid-deck were two payload specialists. The first of these was Michel Lémieux, the first Ardian astronaut to fly aboard a Daitōjin spacecraft, but certainly not the last. Joining him on the mid-deck was  Yasuji Shimotsuki. Due to the nature of the flight, the crew as in many regards actually two crews, being divided into "Red Team" and "Blue Team", with the two working in twelve hour shifts so that work could continue around the clock for the mission. Each team had a pilot, a mission specialist, and a payload specialist assigned to them, with Akasaki, Arisawa, and Lémieux making up Red Team while Yanagida, Sekizuka, and Shimotsuki made up Blue Team.

On the 22nd of November, 1983, the crew of UHS-9 lifted off from Launch Complex 17A, reaching an orbit of approximately 253km at its highest and 240km at its lowest. The crew would spend just over ten days in orbit, during which time they would put the Chiheisen module through its paces. As promised, an explanation of how the Chiheisen module worked will now be provided. Chiheisen was made up of two to three structures. First were pressurized modules, second were unpressurized pallets, and the third, which depended on if you would consider it its own thing, was the pressurized tunnel stretching between the middeck and the module. These components were configurable, leading to long or short arrangements in the payload bay depending on the needs of the mission. For this mission, there was both a pressurized module and an unpressurized pallet. The pressurized module, which was the part the crew could actually inhabit, was around 5.5 meters long and 4 meters wide, although most of the space inside was taken up by experiments mounted along the walls. The pressurized part was made of two segments: the core segment and the experiment segment. The core segment handled much of the infrastructure, such as data processing, while the experiment segment focused more on, as the name implies, experiments. Behind the pressurized module was a 3 meter long pallet which contained a number of experiments that would be left exposed to space. The crew was able to keep an eye on this pallet by a window at the back of the module. This complex was connected to the middeck airlock via a long, pressurized tunnel that was nearly six meters long. The reasoning behind this was that the complex was actually quite massive, meaning they couldn't exactly put it on the back of the airlock as it would make the orbiter front-heavy, thus making reentry all the much harder.

Cutaway of the Chiheisen pressurized module

Over the course of ten days, the crews split up into their teams and kept Chiheisen running around the clock. Commander Akasaki and Pilot Yanagida performed over 200 attitude maneuvers and a few orbit trim maneuvers in support of the science being performed in the payload bay, and for 32 percent of each orbit, the crew was able to take advantage of a stable and high bandwidth connection with the ground thanks to TDRSS. According to documentation on the mission, seventy-two experiments were performed that fell into the categories of materials science, atmospheric physics, space plasma physics, astronomy, solar physics, mundus observations, technology, and life sciences. One of the experiments onboard was different from the others. The mission's pilot, Takauji Yanagida, was a ham radio enthusiast, and with the permission of the DNSA, he brought radio equipment onboard the orbiter and began a tradition of communicating with fellow enthusiasts on the ground, making several transmissions throughout the flight.

Finally, on December 2, 1983, the spacecraft returned to Mundus, landing at Shiroi Shakyū AFB at 9:56 AM local time.
II. Restoring Kyuden
Starting on the fifth of June, 1984, the DNSA began undertaking a series of three missions to bring the aging Kyuden space station back into fully functional condition. As part of this mission, the "Pressurized Cargo Carrier", essentially a modified
and simplified Chiheisen module filled to the brim with supplies, was constructed, designed to ferry supplies to the station and return with whatever waste was left aboard. Owing to Daitō lacking a resupply vehicle during the original run of the Kyuden program, they instead made use of a second pressurized volume within what would've been the station's LOX tank, were it still a third stage of the Tenjin V rocket. While it was not a priority compared to replacing components of the main part of the station including some experiments, wiring, and lighting, the module would be used to return what waste the crew produced during their stays instead, at least until a proper resupply vehicle could be made as part of the agency's plans for the station in the latter half of the 1980s.

Between June of 1984 and April of 1985, nineteen ūchunauts would visit the station, working around around the clock to bring it up to date with the latest technologies ahead of plans to expand the station beyond its adapter. Such missions would prove arduous, with a total of 681 hours being spent working on the station. However, with its completion, the station was once more open for business, with crews in the future being able to operate the station alongside the Chiheisen module starting with UHS-18 in July of 1985. On the note of missions to the station, UHS-12 was the maiden flight of Unryū (US-104), while UHS-18 was the first mission to feature a Tytorian cosmonaut aboard both a Daitōjin spacecraft and a Daitōjin space station.
III. Secrets and Satellites
While you can find information on most UHS missions, some remain fully classified to the modern day. These flights, undertaken by the DNSA on the behalf of the Imperial Government's State Ministry of Defense between 1984 and 1992, are widely known to have served for national security and are notable for having exclusively flown with purely Daitōjin crews. Due to the nature of these flights, what exactly the crews did is unknown. Perhaps they were studying new missile detection systems, or new ways of avoiding missile detection technology of foreign adversaries, or maybe listening in on certain communications. Of course, there is also a lot of mundane stuff that can be classified, such as deploying a large number of new reconnaissance satellite batteries into the space environment in order to see how they held up. As previously stated, it honestly could've been anything, and it was not guaranteed to be intriguing or mysterious simply because of it being classified.

One thing that could be guaranteed with these flights, however, was how much of a pain they could be for the DNSA. The DNSA, by its very nature as a civilian agency, really wasn't equipped to do things secretly. It simply wasn't in its blood. Going back to its first launches, both robotic and crewed, everything had been made public. As a result, they had to go far out of their way to accommodate the State Ministry of Defense and the requirements that come with performing such classified missions. For example, the crew had to train for both daytime and night-time launches, that way the training staff, or anyone else with access to the training plan, wouldn't know when the actual liftoff time would be. Another would be the need to build a new, secure room on the ūchunaut office floor, with a safe and a secret phone with an unlisted number so that the crew could securely coordinate with their SMoD customer. Yet another was stuff like having to craft intricate travel plans full of misleading destinations and last-second reroutes in order to attempt to mask where the crew was training, as routine visits to any site could give hints to the nature of their mission. This also means that, unfortunately, there is very little information on these flights, owing to minimal press coverage, minimal public documentation, and a very, very short mission report.

What is known is that on many of these flights, satellites were deployed. Notably, the first of these flights, UHS-15, deployed an unknown class of SIGINT satellite on the 24th of January, 1984 before returning to Mundus on the day after. Another notable flight, UHS-55, deployed the Satellite Data System, or SDS, whose details also remain classified to this day and are set to remain so until 2023. Ultimately, UHS-15 would land back on Mundus on the 25th of January, 1985, late in the evening. With the end of these SMoD flights, it is now known that the ministry moved to using other rockets due to the tasks performed aboard being deemed no longer important for the organization. However, one final notable flight remains to be briefly touched upon, that being UHS-31, launched on July 1st, 1987 with Akaryū (US-105). UHS-31 was the first flight of the UHS program to be launched on a high-inclination Polar trajectory, making use of the SMoD's desire for greater cross-range capability to land at Shiroi Shakyū air force base on the seventh of July, spending six days and 19 hours in orbit.

[Daitō]

Ad Astra: Chapter Nine — "Golden" Age of the Mizuchi Program, Part Three — Return to Launch Site
I. UHS-25
With twenty-four flights under its belt, the DNSA had begun to fall into complacency. While there were certainly risks to be found with launching any crew into orbit, with the Mizuchi spacecraft's safety record, many both within the agency and the media had convinced themselves of the program's invulnerability. And indeed, by that point it seemed as though such beliefs were well-founded, after all, no major incidents had occurred which jeopardized the mission and the safety of the crew. It was with this context that the UHS-25 disaster occurred.

The year 1986 had promised many things for the DNSA's manned spaceflight program. Save for early delays, the resumption of the Kyuden program was well-underway and on schedule to culminate with the beginning of a permanent presence in Low Mundus Orbit by year's end. The agency was also set to perform the first of two Mizuchi-Kirin missions, that is to say, missions to deploy probes using a modified Kirin upper stage mounted in the payload bay. The agency's fifth and final orbiter, Seiryū (US-106), was set to be launched in 1987 alongside the first fully reusable Tenjin booster. Previous missions, including the one at hand, had made use of previously flown components in their main boosters, of course, using a ballute to allow the booster to land softly in Kynean Sea. Such a fully reusable booster would cut down on costs significantly and make regular flights, previously constrained both by the heat-resistant tiles and the price of stacking boosters, more or less feasible.

The crew of UHS-25 was seven-fold, made up of four veterans and three rookies. They were pilot ūchunauts Dairoku Arisawa, the commander of the flight and a veteran of UHS-9 and 16, and Yorishige Ōsugi, who had flown on UHS-14, as well as mission specialists Makoto Sawamura, a veteran of the UHS-8 mission to Kyuden, and Toyoko Wakata, who had flown on UHS-16 alongside Dairoku Arasawa, as well as rookies Jiro Sadanaga, Mitsuki Hokinoue, and Kazuaki Saionji, the latter of whom were payload specialists. Kazuaki was notable as he was set to be Daitō's first journalist in space, documenting the deployment of a new weather satellite on behalf of the Ecclesiastical State. Lifting off at 10:21:36 AM, the vehicle flew southeast at a bearing of approximately 146 degrees, a path that would, if the need arose, allow the crew to land in Tytor during a Transkynean Abort. At 10:24:01, a loud thud was heard just prior to stage separation, and when the time came, it was found that the central main engine would not ignite. The crew would not reach orbit today, but a decision had to be made as to whether to attempt a return to launch site abort or transoceanic abort. The following exchange is the callout on that decision.

"Sōryu, Shinkyō, you are to proceed to Return to Launch Site, NO/GO for Transkynean Abort."

"Five-By, Shinkyō... RTLS abort confirmed, NO/GO for TKA"

"Happy landing."

As Sōryu rattled under the G-loading, and with the booster burning out and jettisoning, the crew was given a momentary respite. Now came the difficult part, where they began their pitchover maneuver, soon facing the direction they had launched from. Coming out of the roll, the coast of Tsukishima would come into sight and fainter still, the landing site at Artsiv could be made out on the Heads Up Display. The two remaining MMEs, cancelling out the velocity of the Tenjin first stage, would soon exhaust the fuel in the external tank. The vehicle pitched down to 40º, and the crew prepared to separate the now spent tank from the Orbiter. The pilot pulled the vehicle up and free from the external tank, but, in the tension inside the cabin, made an error. The rear of the vehicle recontacted the tank, scraping the aft heat shield and damaging the body flap, both crucial for entry and landing. The vehicle rolled a little, and the crew attempted to compensate with the reaction control system onboard. Ionized plasma began to build around the vehicle as they assumed the correct attitude for entry. For those on the ground, it became readily apparent what horror was about to happen next - but in the cabin, the crew, unaware of the extent of the damage to their vehicle, followed their procedures to the best of their ability. First optics from the spotter aircraft led the head of guidance at Shinkyō to deliver one of the most famous remarks in the history of the accident, echoing the words spoken on that dark day in April 1969: "By the Spirits, flight, the Orbiter... Sōryu's burning."

Sōryu began to descend through the quickly thickening atmosphere, and it soon became apparent to everyone, both aboard and on the ground, that she was not going to reach her landing site at Artsiv. The descent was too steep and too brutal, and they were losing crossrange velocity faster than they could've anticipated. The vehicle, leaking various fluids, was now experiencing intense heating, and exposed bits of the airframe were straining to stay intact as the thicker atmosphere buffeted the crew. The choice was made by the crew to try and level the orbiter out, with the intention to bail out once they had passed through the area of maximum heating. However, the vehicle would not remain intact long enough to prepare to abandon ship. Damage to the heat shield, caused by the impact with the external fuel tank, resulted in ionized plasma entering the airframe, straining the components of the vehicle as it bore the brunt of a steep re-entry. The body flap and engine section would be the first components to detach from the vehicle, and soon, the whole spacecraft began to tumble. The RCS did what it could to hold Sōryu steady, but it was too little too late as atmospheric forces began to take hold, and hard. The starboard wing separated shortly afterwards, only furthering the tumble, and causing the crew cabin to separate, torn to pieces by the aerodynamic forces. For those watching the launch, both from the launch site and from home, this was a moment of existential dread as what had previously been a single light turned to multiple, with pieces of the orbiter sent crashing into the Kyne below. Booster recovery ships, usually meant to transport the spent Tenjin IC stage back to Artsiv, reported pieces of the orbiter falling all around them, and the call was made at Shinkyō to lock the doors.

Recovery would prove difficult, with every available aircraft that could be immediately scrambled after the accident being made airborne, and military vehicles in the Goris metropolitan region soon joined in recovery efforts, searching for any sign that the crew might have survived. In the back of everyone's minds, they knew that this a death sentence, especially during an RTLS abort. As much as they hoped that some sort of miracle had occurred, they knew in the back of their head that there was no chance of survival, no chance of bailing out. Signs soon became clear that their worst fears had been true, as the first piece of the crew cabin were found. Hoisting the panel onto a recovery ship, a photographer would snap a picture that would haunt the program for many years — the Orbiter's name, positioned on the nose just below the flight deck windows, was scorched and waterlogged, a grim reminder of what had become of her crew. Sōryu lay just before them, bobbing in the waves and slowly sinking to the depths of the Kynean sea; once a vision of the future, now nothing more than tangled metal and thermal blankets. The first human remains were recovered by ship before the end of the day, and were brought back to Artsiv for identification. As the days went on, more and more pieces of the good ship would be pulled from the sea and stored in a hangar, beginning a painstaking post mortem on the vehicle.

The DNSA immediately grounded the fleet and began investigating the cause of the issue. Faulty plumbing from servicing after the spacecraft's last successful flight had led to a rupture in the fuel lines on MME 1, preventing it from igniting alongside the rest of the trio. That led to the need for a return to launch site abort and it, mixed with stress-induced pilot error, led to catastrophic damage to the Orbiter's thermal protection system. The program would be set back by a year as techniques to address damage to the heat shield were developed and development on pressure suits compatible with the orbiter sped along. This would also allow for further testing of the UHS's reusable booster in the next year rather than being delayed further. And finally, in January 1987, nearly a year later, Tenryū would perform the return to flight mission, rising from the ashes like phoenix and showing that while a tragedy, the loss of her sister could serve as a springboard into the future, perhaps shaken, but not broken.

[Daitō]

Ad Astra: Chapter Ten — Golden Age of the Mizuchi Program, Part Four — Paradigm Shift
I. An Idea, however vague, takes shape
Even before the 1986 Sōryu disaster, there had been plans underway to replace the Tenjin IC first stage that lifted the UHS spaceplane and fuel tank to a high altitude with something reusable. While this T-IC stage was reusable to a degree, this mostly was down to post-flight refurbishment of parts. Indeed, the first stage that had flown on the ill-fated UHS-25 had featured parts that had flown as early as 1981 and as late as early 1985. Such a stage made use of a ballute to slow it enough for a soft landing in the Kynean Sea some 450 or so kilometers downrange. Following such a landing, they would be recovered by a specialized fleet of vessels before being towed back to Artsiv Space Center for processing. Such a method, while workable in the immediate years of the program, was deemed to be unviable after fifty missions, and as such, plans were made as soon as the program was approved to design a better system for use by the end of the 1980s.

There were effectively two ideas, both of which would have, when they were proposed, seemed downright insane to just about anyone who had proposed it. However, the DNSA, wishing to cut costs in the long run while taking advantage of a boost in funding owing to the UHS program's approval, was all ears. The first of these proposals, the one that was ultimately not chosen, was probably the more insane as well, as it would've involved constructing the world's largest helicopter simply to catch the plummeting booster midair and transport it back to the launch site. Despite being briefly contemplated by the DNSA, it must be understood that it was only considered so as to seem as though there were any real decision in this matter, after all, the DNSA had its collective mind set on one idea.

The infamous "Tenjin Helicopter" proposal

The second option was, by comparison, more simple, although calling it that was a stretch by any means. Instead of the largest helicopter to ever grace the skies of Mundus, the DNSA would construct a fleet of Tenjin-derived boosters capable of gliding back to the runway much like the Mizuchi spaceplane did following reentry. Instead of the largest helicopter, it would, when it first launched, be the largest aircraft to have ever flown, at least by wing area. However, by developing it, it would drastically cut down on both time between flights and on costs, given that it would be the first truly reusable first stage. It was no wonder therefore that it would be selected in 1973, however it would be hit with a number of delays over the course of over a decade, with the first booster, ZS-101, nicknamed "Ikazuchi", being ready only in late 1986 and scheduled to fly in early 1987. This was only mildly perturbed by the Sōryu disaster of the previous year, with the first launch set for second of January, 1987.

Early model of the UHS system with liquid flyback booster, c.1973

II. Rise of the Reusables

Launch of UHS-26, Daitō's Return to Flight

January 2nd, 1987. A day which marked the beginning of a new age, when the first fully reusable Tenjin booster lifted off, carrying the crew of UHS-26. Piloted by Rikugun-Tai-i (Captain) Haruto Kimura and Rikugun-Chūi Minato Yamori, the booster, Ikazuchi (ZS-101), performed its task admirably before gliding back to Artsiv Space Center, where it would be evaluated on its performance and undergo any necessary repairs. The orbiter, Tenryū, would, for its part, carry the first Crew Return Vehicle (CRV), into Low Mundus Orbit where the crew of six would put it through its paces. The age of reusable rockets had dawned, although it was certainly in a primitive state, owing to it still being piloted. Nonetheless, the Ikazuchi crew would be honoured by the public, although they would not fly into orbit until 1990 on UHS-61.

ZS-101 Ikazuchi undergoing servicing at Artsiv VAB, 3 January 1987

As crews on the ground performed servicing on Ikazuchi, the crew of UHS-26 began an important task of their own. Orbiting roughly at the same altitude as Kyuden, they would, making use of the shuttle's remote manipulator system, slowly and carefully extract the CRV from the payload bay before bringing it just a few centimeters above the docking port. Then, they would disable all of the braking motors on the arm, essentially making the arm go limp. At that moment, the commander of the spacecraft would fire six downward-facing RCS thrusters, making the orbiter jump up from their point of view. In actuality, this would bring the two spacecraft closer together, allowing for the crew to transfer in and out of the cabin of the new vehicle. Over the next few hours, the two spacecraft remained docked while the crew prepared for an orbital flight test before, on the 6th of January, the CRV undocked carrying a crew of two. In what was like a mission straight out of the 1960s, the CRV would perform stationkeeping on the orbiter for a few orbits, during which time Tenryū would perform the first "Rendezvous Pitch Maneuver", during which the orbiter would effectively do a "backflip", allowing the crew to inspect the heat shield for any damage, which thankfully proved unnecessary this time.

The first flight of the CRV, featuring the new APAS-87 docking system, undocks from Tenryu

A Rendezvous Pitch Maneuver being performed

After the first three orbits had been completed, the crew aboard the CRV would gently pull away from the orbiter, testing its rendezvous capabilities as it would, if deemed necessary, be capable of ferrying crew from a stricken orbiter in a coplanar orbit back to Kyuden, where an additional crew return vehicle could be launched independent of the Mizuchi spacecraft so as to ferry the crew back to mundus. This would last twenty hours, after which the vehicles docked, the crew entered the orbiter once more, and the CRV would be commanded to undock once more and perform a reentry burn, landing off the coast of Tsukishima. The orbiter would spend another day in orbit, after which it too would land back at Artsiv Space Center.

With the success of UHS-26, her flyback booster, and the CRV, a new era had suddenly begun for the DNSA, not a golden age for simply the UHS program, but for spaceflight as a whole.

[Daitō]

Ad Astra: Chapter Eleven — Into the 90s
I. Kyuden's twilight years
By mid-1987, the first operational flight of a Crew Return Vehicle would be performed onboard UHS-32, carrying it and the first long-duration crew to the Kyuden Space Station. Over the course of the previous months following the UHS-26 mission, a number of adapters had been launched to the station, converting its APAS-75 docking ports to support the new APAS-87 standard. This docking system, though not developed by Daitō, would come to be the standard among most spacefaring nations, with even the USR making limited use of it aboard its space station, Spetsnaz, prior to its collapse. However, the DNSA would be among the first to actually the docking system, owing to its necessity in operations going forwards.

Comparison of APAS-75 and 87 docking systems

The first crew to inhabit Kyuden long-term was, compared to crews aboard Kyokkō, relatively small, being made up of only three ūchunauts. Launched on the 31st of July, 1987, the crew would spend 217 days in orbit, a new endurance record for a Daitōjin crew, though one that would be broken well before the end of the 90s. They would ultimately return to Mundus on the fifth of March, 1988. During their stay, the Kyuden Power Module (KPM) would be launched and docked to the Shizukesa node module's zenith port. The following crew, also made up of three ūchunauts, would spend 222 days in orbit, breaking the previous record. Future "principle expeditions" would generally trend towards around half a year in orbit, although individual crew members would spend further time on missions, with the longest single flight by a Daitōjin crew member being the 1994-1995 flight of Einosuke Yagami, who spent a record of 437 days in flight. This record is, as of May 2022, the longest single flight by a spacefarer in history.

But more importantly for the station itself, it would see three additional modules launched over the course of the late 80s and 90s, all three of which were derived from the Chiheisen laboratory module that had seen service aboard the UHS spaceplane. These modules were, in order of their launch, Kōji, a materials science laboratory mounted on the port docking adapter, Seikatsu, a life sciences laboratory which provided room for an additional crew member and was docked opposite to Kōji, and Unmei, which served as both for Mundus science observation and as a new docking module, located at the bow of the station. The late 80s would also see the delivery of an object which, although not necessary for the mission, would cement its place within the psyche of many generations, that being an IMAX camera which was used most notably for the filming of the 1995 documentary Uchū kichi (Space Station), although it would see extra use for documenting some of the missions before it was returned on UHS-99 in 1998.

Ardian astronaut Anton Martel as seen in Uchū kichi, 1994

Over the course of the twelve years that it saw continuous habitation, Kyuden would also see members of foreign crews visit the station, most notably by Tytorian crews in 1992, 95, 96, and 99. A Heyran astronaut would fly to the station on OE-16 in 1995, while an Ardian crew member would visit the station 1994 as part of OE-13. These early flights would serve as the buildup towards further cooperation aboard Kyokkō in the 2000s, although said station would primarily remain a Daitōjin matter. Sadly, nothing could last forever, and in 1997, it was decided that the year 1999 would mark an end to the Kyuden program after nearly twenty-five years. The last crew would depart on the 20th of November, 1999, and the station would rotate 90 degrees to allow the Teleoperator Retrieval System, or TRS, to fire its thrusters, allowing for a controlled reentry over the Western Antalin. This occurred on the 11th of January, 2000.

Kyuden burns up over the Western Antalin, 11 Jan, 2000

II. TDRS and Goryū
While the Kyuden program began to ramp up, the DNSA had continued to work on other missions for the UHS program. While it would, of course, be used to ferry cargo and crew to the station, it would also be used to launch a number of satellites into Low Mundus Orbit. Most notably was the continued launch of TDRS satellites, which had begun in 1983. The second satellite, TDRS-II, was meant to be deployed on the ill-fated UHS-25, however it was lost alongside the orbiter following a failed RTLS abort. 1987 would see TDRS-III launched, followed by TDRS-IV in 1988. A brief pause in launches of such satellites, resuming in 1991. This would, in turn, be followed by TDRS-VI in 1993 and finally, TDRS-VII in 1995. TDRS-VII was meant to take the spot of TDRS-II, and would be the final of the first generation TDRS satellites to be launched. It would also be the last to be launched aboard the UHS orbiter, with future ones being launched on unmanned Sekidō-C and Tenjin rockets instead, owing to their larger size. As of 2022, there are currently twelve of these satellites in orbit, although only eight remain in operation.

More notable than TDRS, the Goryū space telescope also launched in 1987. The GST was one of many of such telescopes to fly, with further telescopes following a similar design. Over the course of its 22 year mission, it would undergo seven servicing missions, each roughly three years apart, although the first occurred two years after its launch. GST would, during its operational lifespan, serve both as both a vital research tool and a boon to public relations for astronomy, although its mission would come to an end by 2009, when it was recovered on UHS-139. It is set to be replaced in 2023.

Goryū servicing, c.1998

III. UHS-Misaki
A somewhat less spoken about part of the UHS program was the UHS-Misaki program. Making use of a modified Misaki upper stage, known as the Misaki-Ka, it flew three times between 1987 and 1989, deploying a series of deep-space probes. These probes would visit Marduk, Nergal, and the sun, with the one sent to Nergal carrying a lander and orbiter, although unfortunately the lander lost contact during atmospheric entry. The Marduk probe, known as Hagihara in honour of the late astronomer, would explore the Mardukian system for roughly eleven years, ending in 1999.

[Daitō]

Ad Astra: Chapter Twelve — A New Century
I. Extended Duration Orbiter

EDO Pallet for UHS-94

As the Kyuden program wound down, other programs began to take shape that would fill in the gap between it and the Next-Generation Space Station Program, or NGSSP, later evolving into Space Station Kyokkō. Most notably among these was the Extended Duration Orbiter (EDO) program, which would make use of a specialized pallet known as the Extended Duration Orbiter Cryogenic kit, better known as the EDO-pallet or CRYO. CRYO was a 4.6-meter-diameter equipment assembly which attached vertically to the payload bay rear bulkhead of an orbiter, allowing it to support missions of up to 16 days. The equipment included cryogenic tanks, associated control panels, and avionics equipment. All four remaining orbiters were upgraded to accommodate the EDO. In 2004, Akaryū was given a second EDO pallet, giving it 13 pallets and allowing it to fly for up to 28 days in what was the longest independent flight of a UHS orbiter. Such modifications were undone when construction of Kyokkō kicked off.

The EDO program concluded in 2006 with the launch of the first modules of Kyokkō.
II. Assured Crew Return or Personnel Launch System
IIa. Assured Crew Return or Personnel Launch System
Although the DNSA already operated a crew return vehicle, it was felt following the end of the Kyuden program that a ballistic capsule was ill-suited for the role. After all, an oceanic landing would cost precious time during recovery, something which, in the event of a medical emergency, could prove fatal. As early as 1992, proposals were floated to replace it with a spaceplane capable of landing at commercial airports. Of these proposals, two front-runners would appear, both of which would in some form or another see "flight". Those were the XU15K and the XU16As, more commonly known as the Kasori X-15 and Aizawa-Shinoda X-16. Both were designed with the capability of launching on an unmanned rocket as cargo vehicles, which the X-16 was more capable of, as well as carrying crew. The X-15 would fly first, conducting a number of drop tests analogous to those flown for the UHS orbiter. The X-16 would follow shortly afterwards, and following issues with the X-15's development, the X-16 would be selected, being designated the Personnel Launch System, known by its english acronym: The PLS.

Left: X-15, Right: X-16

The Personnel Launch System, as a class of spacecraft, would be launched aboard a man-rated version of the Sekidō-C and later -D rockets. The Sekidō-C and -D were derivatives of the Sekidō-B rocket which had carried the Taka spacecraft into Low Mundus Orbit back in the 60s, which in turn was a derivative of the Sekidō ICBM of Suzaku fame. When launched aboard the Sekidō-C, it would lack a disposable "Orbital Mission Module", or OMM, which would first fly in 2007 on an uncrewed cargo resupply mission alongside the first flight of the spacecraft by a Sekidō-D rocket. Much like the UHS orbiter, the PLS would have a number of named vehicles, with three crew and cargo vehicles built, although the six could in theory alternate between these roles with minor conversion.

First Flight of PLS Taka (US-101), c.2004

Name	Type	Name	Type	Name	Type
Taka	Crewed Spaceplane	Karasu	Crewed Spaceplane	Fukurō	Crewed Spaceplane
Suzume	Cargo Spaceplane	Hato	Cargo Spaceplane	Hachidori	Cargo Spaceplane

List of PLS spaceplanes as of 2010

III. Cargo Resupply
During the Kyuden program, resupply was solely performed by UHS missions making use of the Pressurized Cargo Carrier (PCC), which was essentially a Chiheisen module filled to the brim with cargo. Missions to the station would, as a result, have to carry enough cargo to the station to hold it over for a month, after which two PCC flights would typically occur during an expedition. Going into the 21st century, such an option was deemed to be uneconomical and potentially risky, so it was decided that two additional resupply vehicles would be made. The first has already been mentioned, that being the cargo variant of the Personnel Launch System. However, the second, often overlooked but ultimately the workhorse of the Kyokkō program, was the Kōnotori resupply vehicle. Launching aboard the Sekidō-C/D rockets, it is officially designated as the Sekidō Transfer Vehicle, or STV. However, the name Kōnotori was selected by the DNSA because "a white stork carries an image of conveying an important thing (a baby, happiness, and other joyful things), therefore, it precisely expresses the STV's mission to transport essential materials to Kyokkō."

An STV in 2006

Kōnotori is comprised of four segments, those being as follows:

• Pressurized Logistics Carrier (PLC) — Located at the front of the vehicle, the Pressurized Logistics Carrier is attached to the station by a Common Berthing Mechanism (CBM), which allows for larger payloads to pass into the station. Using this passage, the crew of Kyokkō can enter and work within the PLC.
• Exposed Pallet (EP) — The Exposed pallet carries unpressurized payloads and other equipment.
• Avionics Module (AM) — The Avionics Module is essentially the "brains" of the vehicle, running commands while it is in flight and directing its trajectory to the propulsion module. It contains navigational and electrical equipment and is vital for the spacecraft's survival.
• Propulsion Module (PM) — The Propulsion Module contains the vehicle's main thrusters as well as fuel tanks. Without it, the vehicle is practically dead in the water, so to speak.

The spacecraft's upper half is covered in solar arrays, allowing it to collect power while it is in flight.

[Daitō]

Ad Astra: Chapter Thirteen — Shuttles Old and New
I. Getting an upgrade
Following the 1986 Sōryu disaster, Daitōjin engineers working on the UHS program immediately put into motion long-standing plans to upgrade the UHS orbiter or to create a new class which could compliment it. This vehicle, later dubbed the Hikōtsuru-class for its first production orbiter, would add a number of features both for safety and to upgrade its capabilities, ranging from stretching the cabin so that the entire crew could fit on the flight deck, thus allowing, with regards to safety, the potential reintroduction of ejection seats to, for added capabilities, stretching the payload bay to allow for larger payloads and removing the tailplane and replacing it with vertical winglets on the wings, giving the vehicle greater yaw authority with the tradeoff of adding slightly greater drag, thus necessitating a modified reentry trajectory, not to mention improvements to its heat shield to give it better protection against foam-strikes. Most notably, however, would be the vehicle's ability to fly autonomously, which would primarily be used during its test flights in the mid-1990s.

UHS Block II

The Block II orbiter would see just four vehicles built, the first of which, Hikōtsuru, would fly on the 19th of August, 1997, spending six days in orbit while uncrewed before landing at Shiroi Shakyū AFB. It would fly again in January 1998, visiting Kyūden, where the crew of Kyūden 98A would take their Crew Return Vehicle and dock to the orbiter, spending three days aboard before returning to the station. Hikōtsuru would return once more to Shiroi Shakyū AFB less than a week later, being cleared for full operation. The vehicle, as well as its siblings, would serve an important role in the construction of Daitō's next space station, as would a familiar face.
II. An old friend in all but name
The Zenshoen Program officially dates to 1992, however, in reality, plans for it had existed since the early days of the UHS program as a potential replacement for Kyūden. Sure, initially it was meant for a fully modular space station, however, a number of companies proposed designs that would take the Shirotsuru orbiter, now no longer in service since testing in the 70s, and converting it into a sort of "wet workshop", a space station whose habitable volume would partially be comprised of its fuel tanks, or at a bare minimum to use the orbiter as the core module for it. The design would evolve over the years until it would be selected in 1989, at which point Shirotsuru would start undergoing conversion, being renamed Zenshoen to fit with the program. The name Shirotsuru would later be possessed by Daitō's first Interplanetary Transfer Vehicle starting in 2021.

A preliminary design for Zenshoen, c.1985

Zenshoen would feature an early inflatable "module" nestled into the external tank's intertank structure. Known as the Intertank Crew Access Tunnel, or "ICAT" for short, this would provide access for the crew between the "lower" half of the station, the LOX and LH2 tanks, and the "upper" half of the station. It would prove troublesome initially to inflate, taking three attempts on the first mission to the station in 1998 before it could actually be used, however, since then, it has served the crews of the station admirably. What didn't, at least initially, do so was the LH2 tank, which took until 2017 to be completed. The LOX tank was far simpler, being fully outfitted for the first time in 2000, although it would undergo regular upgrades to its systems over the years. The same could be said for much of the equipment aboard throughout the spacecraft, as the station was designed to be internally heavily modular.

Zenshoen launched in August of 1998.