JAXA+ | What if Japan had an unlimited space budget? | 2060-02-18 - Massive crewed missions to Jupiter, Venus, Mars, and more! [VIDEO]

Please don’t think that lack of in-thread engagement means people don’t care. I love this. My rapt fascination with virtually every timeline like these is merely being tempered by my unbridled lividity and deep depression that OTL didn’t even try to keep space in our grasp. Speculative human spaceflight is far and away my second favorite alternate history thought experiment. It’s just painful to even think about anymore.

Cheers, man.
Please don’t think that lack of in-thread engagement means people don’t care. I love this. My rapt fascination with virtually every timeline like these is merely being tempered by my unbridled lividity and deep depression that OTL didn’t even try to keep space in our grasp. Speculative human spaceflight is far and away my second favorite alternate history thought experiment. It’s just painful to even think about anymore.

Cheers, man.
Thank you. Another thing is that I just don't have the skills or time to write several paragraphs about all the details, or the "human element" like in Proxima: A Human Exploration of Mars (or Eyes Turned Skyward).
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Thank you. Another thing is that I just don't have the skills or time to write several paragraphs about all the details, or the "human element" like in Proxima: A Human Exploration of Mars.
Thats okay, any output you provide will be severely appreciated nonethless
Just have fun, your work is pretty great already
The reason I made this was because the Japanese space program tends to be neglected (or barely acknowledged) most of the time in media coverage or alternate history scenarios, because of "economic stagnation."

Last year, I rebooted the Hatsunese Space Program. But some people thought that its focus on probes (and not catching up with [and leapfrogging] the superpowers until the 21st century) wasn't exciting enough, and there was a demand for a scenario that actually involved Japan.
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2037-10 - Ame-no-Uzume Venus habitat assembly (and comsats)
The Ame-no-Uzume Venus Mission was named after the Japanese goddess associated with dawn and merriment, as a successor to the Akatsuki ("Dawn") Venus orbiter mission. It would involve a total of 6 (2 + 4) launches. In 2037, the Venus Habitat Module and Venus Ascent Vehicle would depart Earth to enter a 300 km orbit around their destination. The crew would launch in 2039 and ride on the Venus Transport Vehicle. Several transfer stages, heavier and longer compared to their Mars-bound predecessors, would be launched by the H-Z 222L. The crew would then transfer from the VTV to the VHM/VAV, which would deploy an inflatable heat shield and enter the atmosphere of Venus, releasing parachutes and a large balloon* that would allow the vehicle to float over 50 km above the extreme conditions on the surface. Two astronauts would enter the Venusian atmosphere while one would stay in orbit. After about 30 days, the two-stage VAV would drop from the VHM and launch back to orbit, meeting up with the VTV. Once returning to Earth in 2040, Earth Arrival Vehicle would then slow down to reduce G-forces upon re-entry.

* from KerBalloons with modified configs



2037-09-25 - The first launch (H-Z 204L) carried the Venus Habitat/Ascent Vehicle with the Venus Orbit Stage (3x LE-7-R, 3x LE-5B-3), which had a mass of over 400 tonnes and entered a 400 km parking orbit. The VAV had a Raptor engine on the first stage, with 3x methane RL10s on the second stage. The solar arrays were slightly smaller than the Mars mission due to Venus being closer to the Sun; however, the Venus Transfer Vehicle (2039-2040) would need to go as far as the orbit of Mars during the return trip.


2037-10-16 - A Zeta rocket launched from Uchinoura Space Center with three Kodama-X Data Relay and Tracking Satellites to Venus.



2037-10-19 - An H-Z 222L launched the Earth Departure Stage (8x LE-7-R) for the Ame-no-Uzume Venus Habitat/Ascent Vehicle, docking just a few hours later. The total mass of the stack was about 1180 t.




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2038-04 - Ame-no-Uzume Venus habitat arrival
2037-10-24 - The eight LE-7-R engines of the Earth Departure Stage ignited, pushing the Ame-no-Uzume balloon habitat and ascent vehicle towards Venus, which it would reach in just over 5 months.


Separation from Earth Departure Stage


2038-03-26 - The three Kodama-X relay satellites arrived at Venus simultaneously, executing their maneuvers within minutes of each other* to enter a high elliptical orbit (with a period of about 20 days). As Venus spins clockwise instead of counter-clockwise like most planets, so did the satellites' orbits. Afterwards, they would make plane changes then finally enter a 24-hour circular equatorial orbit (33400 km) on 2038-04-18.

* This was made possible in KSP by the Physics Range Extender mod, which can prevent craft from unloading even if they are hundreds of kilometers apart. Also, plotting an encounter that required the periapsis (low point in the orbit) to be at the same time as the point where the orbit crosses the equator required me to use HyperEdit to place a temporary "dummy" satellite in an equatorial orbit for the purpose of better targeting.


Simultaneous Venus orbit insertion


Trajectories of the relay satellites after orbital insertion (with imaginary "dummy" satellite)


Final orbits of the relay satellites and the Venus habitat

2038-04-02 - The Venus Orbit Stage of the Ame-no-Uzume balloon habitat performed its multi-phase orbital insertion: first to an elliptical orbit, then a plane change, then finally to a 300 km equatorial orbit on 2038-04-06. The transfer stage was almost identical to the Kagutsuchi Mars Orbit Stage, with its three LE-7-R main engines and three auxiliary LE-5 engines. The vehicle would wait in orbit for about one and a half years for the crew to arrive in the Venus Transport Vehicle. The equatorial orbit would ensure that the ascent vehicle could return to rendezvous with the transport vehicle at any time.

2038-04-06 - Final orbit insertion



2038-04-02 - Initial orbit insertion


2038-04-04 - Plane change


A burn pointing away from the surface equalized the orbit to 300 km.

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2039-05 - Ame-no-Uzume Venus transport assembly
2039-03-09 - An H-Z 222L launched the first module of the Ame-no-Uzume Venus Transport Vehicle, the Venus Orbit Stage (6x LE-7-R engines) and Earth Return Stage (3x LE-7-R, 3x LE-5B-3). At 800 tonnes, they were larger than the Kagutsuchi Mars mission stages because of Venus's deeper gravity well. Like its predecessor probe, Akatsuki, the public relations campaign involved engraving some of the metallic portions of the spacecraft with thousands of names from the public and images of a certain virtual singer.





2039-03-31 - Another H-Z 222L launched the first of two Earth Departure Stages (8x LE-7-R), identical to the one launched for the Venus balloon habitat and ascent vehicle, docking to the rear of the VOS/ERS almost two and a half days later. Total mass: 1570 t.




2039-04-22 - As a duplicate of the previous launch, the second Earth Departure Stage appended itself to the end of the VTV. Total mass: 2350 t.




2039-05-14 - An H-Z 102S launched the crew of three on the Earth Arrival Vehicle, on top of the VTV's habitation module. These astronauts were Misora Kaneko, Asuka Tanoue, and Kasumi Aimoto. After transposition and docking, the EAV used its LE-5B-3 engine and small RCS thrusters to rendezvous and dock with the Venus Transport Vehicle. A saddle truss was located between the hab and the Earth Return Stage, to serve as a docking point for the Venus Ascent Vehicle once it had returned to orbit. The total mass of the VTV once assembled was 2420 tonnes, 40 percent heavier than the Kagutsuchi Mars Transport Vehicle.



Transposition and docking



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2039-10 - Ame-no-Uzume crew - Earth to Venus
2039-05-21 - On the 29th anniversary of the launch of the Akatsuki Venus probe, the Ame-no-Uzume Venus Transport Vehicle began its journey from Earth. The eight LE-7-R engines of the first Earth Departure Stage burned to raise the orbit's high point by about 10,000 kilometers, before stage separation. Three-and-a-half hours later, the second EDS burned and separated, leaving the remaining vehicle on a course for Venus. Total change in velocity (delta-v): ~3400 m/s

First Earth Departure Stage burn - 1470 m/s


First EDS separation

Second EDS burn -1961 m/s


Second EDS separation




2039-10-26 - After five months in interplanetary space, the Venus Transport Vehicle arrived at its destination. The six LE-7-R engines of the Venus Orbit Stage ignited to insert the craft into a 2-day elliptical orbit. On the next day, a plane change maneuver near the high point would align the orbit with the equatorial Venus (balloon) Habitation Module that arrived in April 2038. Two more orbital insertion burns would set up a relatively slow rendezvous with the VHM on October 28. Observing the relatively featureless (aside from a few ripples) cloud layer blanketing the entire Venusian surface, Asuka Tanoue would stay in orbit as Misora Kaneko and Kasumi Aimoto prepared to undock from the VTV in the Earth Arrival Vehicle to transfer and re-dock to the Venus balloon habitat. Total delta-v used: ~3650 m/s (and ~150 for plane change)



First orbital insertion burn - 939 m/s


Plane change (to an equatorial orbit) - 149 m/s


Second orbital insertion burn - 1987 m/s


Third orbital insertion burn - 712 m/s

2039-10 - Ame-no-Uzume crewed Venus balloon
2039-10-28 - Six years after the Kagutsuchi Mars landing, two crewmembers (Misora Kaneko and Kasumi Aimoto) undocked in the Earth Arrival Vehicle to make a short relocation from the Venus Transport Vehicle to the Venus Habitation Module. Once docked, the crew entered the small habitat, pressurized the cabin, and made preparations to de-orbit. The EAV undocked once again to make it back to the VTV, where Asuka Tanoue would remain in orbit.

The Earth Arrival Vehicle docked with the Venus Habitation Module in the foreground, with the Venus Transport Vehicle in the background


EAV undocking

A short trip of a few hundred meters


The EAV making an automated return to the Venus transport


The Venus habitat/ascent vehicle before de-orbit


A couple hours later, the three LE-5B-3 engines of the VHM's orbital stage would light for one last time before being discarded and burnt up in the atmosphere. The VHM separated from the stage and inflated its 25 m heat shield, beginning its descent into the thick atmosphere. Large reaction control thrusters were needed to stabilize the vehicle, otherwise it would end up aerodynamically flipping with the heat shield in the rear and the less-resistant habitat and ascent vehicle in the front. During ballistic deceleration, the people onboard experienced high G-forces, up to 9 times that of Earth. This lead to momentary loss of consciousness, but they soon recovered after a few seconds. Much exercise was needed on the outbound journey to prepare the crew for this harrowing moment, which would be followed by wonder. At 75 km above the surface, the parachutes released, gradually slowing down the vehicle from hundreds to tens of m/s. At 60 km, the heat shield was jettisoned with slightly imbalanced solid fuel separation motors, to prevent the drag of the shield from causing a re-collision.

55 km was the suitable attitude for the parachutes to cut and the large balloon to inflate. The balloon itself had a mass of 23 t [ballast mass added based on the HAVOC concept], making up about one-quarter of the habitat + ascent vehicle (90 t). The hab descended as low as 49 km before it began to rise again, ultimately settling in at an altitude between 52.8 and 53.8 km. At this altitude, the pressures are relatively Earth-like (90-100 kPa) compared to the surface (over 9000 kPa), while the temperatures are around 50 °C instead of the lead-melting 460 °C. The gravity of Venus was also 90% that of Earth. The crew would stay in the atmospheric habitat, powered by four RTGs, for 30 days before returning to orbit in the Venus Ascent Vehicle.

[note: The KSP mods KerBalloons and AirPark (to suspend the vehicle in the air) were used. The KerBalloons part is only 15 kg and has a bug in which it explodes (if inflated) when loading a save file, so the file had to be edited to have the balloon uninflated when loading with AirPark.]




Stage separation and heat shield inflation


Atmospheric entry


Parachute deployment


Heat shield jettison


A close-up of the habitat and ascent vehicle

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2039-11 - Ame-no-Uzume Venus ascent
Misora Kaneko and Kasumi Aimoto stayed in the upper Venusian atmosphere for one month, above a vast majority of the thick carbon-dioxide-filled atmosphere which trapped heat to an excessive degree. However, the balloon habitat also had to be able to withstand clouds of sulfuric acid. The scientific mission was mainly to observe the weather and climate of Venus, including wind patterns and lightning, as well as how the atmosphere interacted with the surface. In a phenomenon known as super-rotation [not simulated in KSP], winds in the upper atmosphere circle the planet in only four Earth days while the ground takes 243 days to rotate. Another goal was to search for the possibility of life in the form of extremophile microorganisms floating in the upper atmosphere.

2039-11-27 - The Venus Ascent Vehicle was a two-stage "rockoon," 4 meters wide. A cylindrical crew cabin was surrounded by an aerodynamic shell, with methane/liquid oxygen rocket stages underneath. After the crew climbed down into the VAV, it detached and fell from the balloon habitat (at an altitude of 53.9 km), firing ullage motors (to settle the propellant) and igniting its single Raptor engine (borrowed from SpaceX). This methalox engine was chosen for its relative storability and high thrust compared to hydrogen, and efficiency compared to hypergolic fuels. As it began to rise again, the ascent vehicle was programmed to automatically tilt and avoid a collision, while being stabilized by vector thrust and four fins. The first stage burnt out at about 100 km, and was jettisoned. The second stage used three RL10 CECE methalox engines to reach an orbit of 220 km. Approximately 9200 m/s of delta-v was needed to reach orbit from 54 km, similar to the requirements for launching from Earth at sea level. Only one engine was used for orbital maneuvers. Several hours later, the VAV made a rendezvous with the Venus Transport Vehicle, docking at the saddle truss behind the VTV's habitation section. Misora and Kasumi had rejoined Asuka Tanoue, and were preparing to make it back to Earth.



Initial drop



Second stage separation



In orbit


Approaching the VTV

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2040-11 - Ame-no-Uzume Earth return [VIDEO]

2039 -11-29 - Once the crew were all inside the Venus Transport Vehicle, the Ascent Vehicle undocked and was de-orbited. Like the Mars mission, departure from Venus happened in multiple phases, with a burn into an elliptical orbit (lasting 4 days), an inclination change near the high point, and a final escape burn on 2039-12-03. However, the remaining propellant on the Venus Orbit Stage was also used for one last boost (300 m/s) before the Earth Return Stage took over and used up over 4200 m/s of delta-v. The ERS had two LE-7-R and two LE-5B-3 engines.

Third and final phase of Trans-Earth Injection (1495 m/s)


Venus Ascent Vehicle undocking


Trajectory planning needed the use of the KSP Trajectory Optimization Tool and another "dummy" object placed with HyperEdit.
The orbital maneuvers had to take place where the orbit crossed the equator, so that the plane change (green, Node 3) could be performed at the orbit's high point (apoapsis), reducing the change in velocity required.


First Trans-Earth Injection burn, and the final burn of the Venus Orbit Stage (300 m/s)



Second TEI burn (2500 m/s)


Plane change (229 m/s)


2040-11-03 - Because this mission was a short-stay (opposition class), Earth was not in an optimal position for a minimum-energy (Hohmann) transfer. Thus, the journey back to Earth ended up taking 11 months instead of 5 months, going as far as Mars's orbit around the Sun, so that the Earth could catch up in its orbit. Upon arrival, the VTV was travelling with over several km/s in excess velocity. The crew undocked in the Earth Arrival Vehicle, which was designed to propulsively brake using its LE-5B-3 engine (4400 m/s) approximately 10 minutes before entering the atmosphere, to reduce heating and G-forces during re-entry. Splashdown occurred in the Atlantic Ocean west of Africa.


Interplanetary orbit, going as far as Mars


Earth Arrival Vehicle - propulsive deceleration (4400 m/s)




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2043-01 - Koujin Vesta habitat launch (and comsats)
In the 2040s, JAXA+ planned to send two crewed missions to the Asteroid Belt between Mars and Jupiter. The Koujin mission (named after the Japanese god of the hearth and kitchen) would go to Vesta, while the Inari mission (named after the Japanese god of rice, agriculture, and prosperity) would go to Ceres. Both missions would use identical hardware, the habitats and landers sent first in 2043, followed by the crewed transports in 2044 and 2045.

This would be the first use of nuclear thermal propulsion (NTP) on a mission. Nuclear power was considered controversial in Japan after the 2011 Tohoku earthquake and tsunami, leading to the meltdown of the Fukushima power plant . However, by the 2020s, Japan was restarting its nuclear plants. There was still some reluctance to utilize nuclear power* unless it was necessary or practical, such as powering a base for long lunar nights. As JAXA+ started to aim beyond the inner solar system, nuclear energy would be needed for efficient engines (about twice the specific impulse of chemical propulsion) and powering spacecraft where sunlight was weak. Two engines were developed: the small LE-N engine (based on the SNTP-PFE100, 245.2 kN of thrust) and the massive LE-N2 (based on the NERVA II, 867 kN of thrust). The engine designs were modified to use low enriched uranium (LEU)**, which could not be used for nuclear weapons (the mythological deity Koujin also represented "violent forces that are turned toward the betterment of humankind").

*As a side note, sentiment against nuclear power after Fukushima led to the building of more coal plants instead of renewables (which are land-constrained)
**I do not know how that would affect performance

The NTP engines used pure liquid hydrogen instead of hydrolox, meaning less dense and much larger propellant tanks (from 10 to 13.9 m diameter). Each mission would launch 7 rockets mostly consisting of the H-Z 122XL, a variant using a single extended core stage, two liquid and two solid rocket boosters, and an extra large fairing (19 m diameter) to accommodate the larger stages. It would be able to lift between 750 to 800 tonnes to low Earth orbit.

The interplanetary transport habitat launched by the H-Z 102L had a larger 25 m centrifuge ring, able to generate 0.5 Gs. The crew would primarily live in the rigid sections comprising one-fourth of the inflatable ring, surrounded by a total of 50 tonnes of radiation shielding to reduce exposure to cosmic rays. The heavy shielding would result in the transport weighing over 3600 tonnes, while the surface habitat and transfer stages only weighed 760 tonnes.

(note: I had to change the Kerbalism config files to make the ring shieldable, and reduce the surface area for shielding)

edit 2023-01-23: I underestimated the amount of hydrogen needed for refueling, so I have revised the mission plan with one more tanker launch.



2042-12-29 - A Zeta rocket (with a 9 m wide fairing) launched from Uchinoura Space Center with three relay satellites to Vesta. Each had a mass of about 900 kg. The 5 m nuclear stage used a single LE-N engine and was almost 50 tonnes, and had drop tanks to increase maximum Delta-v. A distant flyby of the Moon occurred less than a day after launch.
Earth-Vesta transfer burn Delta-v (c. 2043): ~4300 m/s





Drop tank jettison


Fly-by of the Moon

2043-01-05 - An H-Z 122XL launched the Koujin surface habitat and lander to Vesta. The first nuclear stage used two LE-N2 engines, followed by a single LE-N2. Both the habitat and relay satellites would reach Vesta in January 2044.





Second in a series of two burns


Trajectory to Vesta

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Yay, it’s back. That’d obviously be the most ambitious mission ever undertaken in history. If we count the ISS, of course, that beats in in total amount of assembly launches by far, but this sucker’s the closest thing to Von Braun’s original Mars plan of anything else seen. Is this designed as a scientific testbed for outer solar system missions? Get the platform down and test the effects of longevity and exposure? Oh, and for the crew, too. Without torchships, that tether system is going to be vital for them on the outbound and inbound runs.
2043-05 - Inari Ceres habitat launch (and comsats)
2043-05-22 - Another trio of relay satellites was launched to Ceres. This time, launching in full daylight.
Earth-Ceres transfer burn Delta-v (in 2043): ~5000 m/s

[edit: Due to underestimations of fuel by MechJeb during orbital insertion at Ceres (it assumed that the satellites would detach prior to insertion), the mission was redesigned / retconned. The core diameter is now 6 m instead of 5, with a total mass of 68 t, and is launched by an H-Z 102L rocket instead of a Zeta.]



2043-05-28 - The "Inari" mission to Ceres began with the launch of the surface habitat and landing modules. After Trans-Ceres Injection, the first nuclear transfer stage ran of fuel and was jettisoned early. It would arrive at Ceres in January 2045, about 1 year after the arrival of the Koujin habitat at Vesta.




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2044-01 - Koujin habitat lands on Vesta
2044-01-09 - Three DRTS relay satellites arrived at Vesta. The LE-N transfer stage braked into an elliptical orbit before transferring to a semi-synchronous equatorial orbit (almost 11 hours) with an altitude of 600 km and jettisoning the satellites, which moved into their triangular positions by January 12. Vesta took just over 5 hours to rotate, but a synchronous orbit of 280 km could not have line-of-sight communications for a trio of satellites.

Vesta capture burn Delta-v (in 2044): 5200-5300 m/s



2044-01-11 - The Koujin surface habitat and lander module arrived at Vesta. From an elliptical orbit, it lowered itself down to an 90 km orbit (36 degree inclination), aligned in such a way for the crew to depart to Earth with a minimal change in velocity. The habitat and lander modules deployed their solar panels and were released from the transfer stage. The lander module would remain in orbit for the crew to arrive by the end of 2045, while the habitat made its descent using two RL10 engines, touching down in the middle of Marcia Crater on January 13 (JST) and deploying drills to mine regolith for radiation shielding.






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2044-06 - Koujin Vesta crew transport assembly/departure
2044-02-14 - An H-Z 122XL rocket takes off with the first components of the Koujin Vesta crew transport, the Earth Return Stage and Asteroid Orbit Stage, to a 400 km parking orbit. The stages have a diameter of 13.9 m and are launched partially fueled.
2044-03-09 - (H-Z 122XL) The central Earth Departure Stage launches and docks to the rear of the AOS using a new annular docking ring.
2044-04-02 - (H-Z 122XL) The first Earth Departure Stage Booster, which docks to the side of the EDS. Two pairs of docking ports are used for stability.
2044-04-27 - (H-Z 122XL) The second Earth Departure Stage Booster, which docks to the other side. The boosters are designed to remain attached to the central EDS (and not separate).
2044-05-20 - (H-Z 122XL) The Tanker-L, which mostly refuels the transport vehicle with liquid hydrogen but not completely [as I discovered].
2044-06-01 - (H-Z 104XL) The Tanker-S, a shorter version which does the rest of the refueling. Undocking of the tankers is performed shortly after.
2044-06-14 - (H-Z 102L) The transport habitat (with 50 tonnes of radiation shielding) and Earth Arrival Vehicle launch with three astronauts: Heisuke Koishi, Rena Minase, and Takeshi Kakoi. Over a day later, it docks to the front of the ERS and inflates the 25 m centrifugal gravity ring.
2044-06-21 - Starting with a mass of 3650 tonnes, the Koujin Vesta transport leaves Earth over a series of two burns (total ~4800 m/s). It will reach Vesta in December 2045, coinciding with the Inari crew transport's departure for Ceres.



Earth Return Stage / Asteroid Orbit Stage (launch)


Earth Departure Stage docking (launch)



EDS booster 1 (launch)


EDS booster 2 (launch)


Tanker-L (launch)


Tanker-S (launch, undocking)


Transport hab, EAV, and crew (launch)



Second burn

2045-01 - Inari habitat lands on Ceres
2045-01-12 - Three relay satellites (DRTS-X13 to15) inserted into a 9-hour stationary orbit over 720 km above Ceres. They arrived in their final positions on January 15.

[Due to underestimations of fuel by MechJeb during orbital insertion at Ceres (it assumed that the satellites would detach prior to insertion), the mission was redesigned / retconned. The core diameter is now 6 m instead of 5, with a total mass of 68 t, and is launched by an H-Z 102L rocket instead of a Zeta.]



2045-01-18 - The Inari habitat and landing modules arrived at Ceres, entering a low orbit between 80 and 90 km on the next day and using up a total of 5900 m/s of Delta-v. The habitat landed in Occator Crater on January 20 while the crew lander would remain in orbit until 2047.




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