JAXA still continuing investigation on failure of Hitomi X-ray satellite mission, but times goes on and Agency still works on multiple different projects. Sometimes time and hard work is best remedy for wounded proud.
H-II rocket is proven launch vehicle but it was clear that intensification of Japanese participation in space exploration (engagement in International Space Station which was confirmed until 2024, various independent space projects like Hitomi or Akatsuki, increasing number of reconnaissance satellites and planned establishing own infrared early warning system) will ultimately resulted in increased number of flights contracted for government. JAXA and Japanese authorities are also still considering increasing presence on commercial market - good example is South Korea which is potentially ally (and customer) for creating early warning system which could detect rockets launched from North Korea which are usually targeted into South Korea or Japanese territorial waters. First commercial launch of the H-IIA rocket was performed on 24 November, 2015, after 14 years of service, from Launch Pad 1 in Tanegashima Space Center for Canadian broadcasting operator Telesat. Payload was Telstar-12V satellite which was successfully put into orbit. It became pretty clear that JAXA would like to offer their launch services commercially for larger number of customers. In the end of March 2016 United Arab Emirates Space Agency announced that chose H-IIA as a lunch vehicle for their "Hope" Mars probe which launch is scheduled for 2020. This seriously confirmed that JAXA is considered worldwide as reliable partner even in case of difficult and ambitious space projects.
In 2013 Japanese authorities gave agreement for starting developing new rocket named later H3. On 27 March 2016 it was officially announced by NHK that Mitsubishi Heavy Industries was chosen as main contractor (MHI was only company which was applying) for H3 rocket with 2020 as date of maiden flight of the rocket without boosters and 2021 as maiden flight with boosters. On May 18 2016, JAXA announced more details about their future rocket. As primary objective JAXA put (according to website announcement):
"Our aim of the H3 is to have a launch vehicle that launches a payload “quicker” and “easier” with “high reliability” while securing flexibility to answer the voices of customers. We have set a target for launch capability and price while focusing on the flexibility of launch services to cope with worldwide payload launch needs."
It seems that it is clearly stated that H3 will be rocket developed as commercial launch vehicle; it should not be surprising - previous modifications of the H-II rocket were performed to improve rocket's ability of lifting different payloads to orbit. Good example was upgrading H-IIA rocket to be used during 29th flight when Telstar-12V was launched. Rocket was combined with upgraded upper stage for better "User Friendliness" as JAXA described modifications on their website. JAXA proved that they are able to modify their rocket for one customer and still keep launch price on reasonable level. H3 should be consider as flexible solution for customers which could be easily adopted payload weight by using different number of solid boosters. Without boosters rocket will be able to lift up to 4 t to SSO for $45.69 million. In most advanced configuration with four SRB-A boosters and second stage rocket will be able to reach GTO with 6.5 t of payload. As main feature, which will cause low cost of the launch, will be swapping from "build-to-order" technology (case of the H-IIA modified for Telstar-12V) technology will be changed for "flow line manufacturing seen in general industrial productions" as JAXA stated on their website. Part of the cost cutting design will be also new LE-9 engine for first stage of the H3. With more reliable LH2/LOX fueling, decreased number of parts for better reliability (still H-II during 30 missions had only one failure). LE-9 started to be developed earlier then decision about starting H3 project was made. In 2006 Mitsubishi and IHI decided about joining efforts for creating new Expander Bleed Cycle rocket engine which would be highest thrust EBC engine ever developed. Expander Bleed Cycle is technology based on using hydrogen from turbopumps to cooling main combustion chamber and after heating same hydrogen is used for driving turbines. Advantages of this solution are: lower temperature of the fuel in turbine what gives possibility of using same engine multiple times because turbines are not working in extreme temperatures; better tolerance in operating what means that even if any small object will get into fueling system it will not destroy its components; engine itself is more robust and can easily work with maximum thrust for a period of time. Rocket will be two stage fueled with LH2/LOX with 0, 2 or 4 solid fueled boosters. First stage will be fueled with 209 t of propellant and powered by two or three LE-9 engines with 432 s thrust impulse of 2900 kN. It will be height for 36 m with diameter at 5.2 m with total mass of 238 t. Second stage will be equipped with one or two LE-5B engines fueled with LH2/LOX with 137 kN of thrust during 442 s specific impulse. It will be height for 9 m with diameter at 5.2m. Total rocket height will be 63 m (compering to H-IIA 53 m) and total mass probably under 300 t (comparing to H-IIA ~345 t). Solid fueled boosters will be SRB-A boosters with 65 t of propellant and thrust at 2260 kN. Boosters are long for 15 m with diameter at 2.5 m.
Rocket will be launched from Tanegashima Space Center Launch Pad 2, presently used for H-IIA, after modifications of launch facilities.