Mitsubishi Heavy Industries Technical Review Vol. 58 No. 4 (December 2021)
1Development Status and Future Prospects ofH3 Japanese Flagship Launch Vehicle

TOKIO NARA*1

TADAOKI ONGA*2MAYUKI NIITSU*1

TAKASHI TAMURA*3OSAMU KITAYAMA*3YORICHIKA MIHARA*3

The H3 launch vehicle is currently under development as Japan’s next flagship launchvehicle that will replace the H-IIA/H-IIB. The objectives of the H3 launch vehicle are to ensure"competitiveness in the global commercial market" and "assured access to space", as well as tomaintain and strengthen the Japanese industrial base by obtaining orders for commercial satellite
launches. Mitsubishi Heavy Industries Ltd. (MHI) has organized the vehicle development as theprimary contractor and taken charge of the development of the engine system. The development iscurrently in the final stage of the test and verification phase. System tests and LE-9 engine firing
tests are underway toward the launch of the first vehicle in JFY2021. This report provides
overviews the current development status of the H3 launch vehicle and outlines the future
prospects.

|1. Introduction
The development of the H3 launch vehicle, as Japan’s next flagship launch vehicle replacing
the H-IIA/H-IIB, started in 2014. MHI have organized the vehicle development as the primarycontractor and is proceeding with the development of the engine system in cooperation with theJapan Aerospace Exploration Agency (JAXA).
The primary objectives of the H3 launch vehicle are to ensure "assured access to space" and"competitiveness in the global commercial market." It is intended that the aerospace industrial baseis maintained and strengthened by ensuring sales for a constant number of vehicles includingcommercial satellite launches. To this end, in addition to "high reliability," which is the advantageof the H-IIA/H-IIB, the following three points were reflected in the development specifications
based on the results of interviews with customers: (1) competitive launch capability and price, (2)operational improvement at launch site and ensuring launch on desired date and (3) a comfortablevehicle with less vibration(1).
The development is currently in the final stage of the test and verification phase. System tests
and LE-9 engine firing tests are underway toward the launch of the first vehicle in JFY2021. This
report overviews the current development status of the H3 launch vehicle and outlines the future
prospects.

|2. Overview of H3 launch vehicle(1)

Vehicle system
Figure 1 shows the vehicle configuration of the H3 launch vehicle. The H3 launchvehicle has a launch capability of about 2 to 7 tons to a geostationary orbit (with the conditionof ΔV to GSO =1500 m/sec). To seamlessly respond to a wide range of required launchcapabilities, the number of solid rocket boosters and the number of main engines for the first*1Chief Staff Manager, Space Systems Division, Integrated Defense & Space Systems, Mitsubishi Heavy Industries, Ltd.

*2Deputy Director, Space Systems Division, Integrated Defense & Space Systems, Engineering Department, Mitsubishi HeavyIndustries, Ltd.

*3

Chief Staff Manager, Engineering Department, Space Systems Division, Integrated Defense & Space Systems, Mitsubishi
Heavy Industries, Ltd. Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 58 No. 4 (December 2021)
2stage can be selected. The vehicle configuration is represented as H3-abc, with a) the number ofmain engines for the first stage (2/3), b) the number of solid rocket boosters (0/2/4) and c)fairing size (W:Wide, L:Long, S:Short). Fairing size W has a total length of approximately 16.4m, which is the same level as fairing size L, and the diameter has been expanded from 5.2 m to
5.4 m to accommodate larger payloads. The minimum configuration, which is H3-30S, isintended to be applied mainly to institutional missions and H3-22L/H3-24L/H3-24W areintended to be applied to commercial missions.
For the satellite interface structure, payload adapters with standard clamp-band sizes(937/1194/1666 mm) will be provided. To flexibly respond to the demand for the launch ofmultiple small satellites, which has been increasing in recent years, a special payload adapter
will be provided.

Figure 1 Vehicle configuration of H3 launch vehicle(2)

Vehicle subsystem
For the vehicle subsystem, consideration was given to the balance between following theheritage of the H-IIA/H-IIB technologies and making changes and/or incorporating newtechnologies to achieve a competitive price. Simplification, commonality and generalizationwere considered as common policies to both the system and subsystem and automatedassembly, processing and inspection were incorporated.
For the liquid rocket engine as one of the major subsystems, the "expander bleed cycle",which is Japanese proprietary technology and has been used successfully in the second stageengines of the H-IIA/H-IIB, was adopted for both the first and the second stages. This engine
system offers simple construction, low cost, easy control and high reliability. In terms of themanufacturing of complex components such as injectors, 3D printing technology is used toreduce costs and shorten the manufacturing period.
For the solid rocket booster, the flight-proven technologies and design adopted in theH-IIA/H-IIB/Epsilon are used, securing both reliability and low cost. For the motor case size
and materials, nozzle, etc., the flight-proven design is followed, while cost reduction ispromoted through the reduction of functions (fixed nozzle), simplification of joint structure, etc.
The structural system and propulsion system of the vehicle are based on the existing
design while cost reduction is realized through the simplification of the shape, reduction of
special materials and the automation of processes. Examples include the reduction of thenumber of structural parts comprising propellant tank by using an integrally formed deep
spinning dome, the application of an automatic drilling and riveting machine to the assembly ofmain structures and the use of off-the-shelf commodities (aircraft and automobile parts) forMitsubishi Heavy Industries Technical Review Vol. 58 No. 4 (December 2021)
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avionics components to the maximum extent possible.
Figure 2 gives examples of cost reduction for the H3 launch vehicle. For detail featuresof the vehicle subsystem, refer to the previous report(2).

Figure 2

Examples of cost reduction for H3 launch vehicle|3. Progress of H3 development
3.1(1)Development of LE-9 engine
Progress of development
Figure 3 presents the overall development schedule of the H3. The development iscurrently in the final stage of the test and verification phase and is progressing with the goal oflaunching the first flight (TF1) in JFY2021. Although the first flight was initially scheduled inJFY2020, issues were identified during the LE-9 engine qualification test (QT) in May 2020
and the flight was delayed from JFY2020 to JFY2021 in order to address these issues.
In February 2020, the qualification firing tests of an LE-9 engine in the flight
configuration commenced. After the 8th firing test conducted on May 26, 2020, openings on
the combustion chamber internal wall surface and cracking on the rotor blade of the liquidhydrogen turbine pump (FTP: fuel turbine pump) were found through the inspection. Both ofthese issues became apparent after the 8th combustion test.

Figure 3(2)Overall H3 development Schedule

Issues and corrective measure - Openings on combustion chamber
Figure 4 is an overview of openings on the combustion chamber. Fourteen openings witha maximum width of about 0.5 mm and a maximum length of about 10 mm were found along
the liquid hydrogen flow path (cooling channel) that cools the combustion chamber. This test

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was conducted under the operating conditions where the heat load on the combustion chamber
was the harshest. As a result of investigating the cause, it was determined that the inner wall
became hot and deformed due to the local heat inflow during steady combustion and the surface
layer was melted or thinned, which led to the openings
As a corrective measure, the operating conditions of the engine are set so that thetemperature of the inner wall surface of the combustion chamber would not exceed theallowable value. In order to define the allowable temperature value, firing tests were conductedwith temperature sensors attached to the inner wall surface and the correlation data between theinner wall surface deformation that leads to openings and the wall temperature were acquired
and the validity of the analysis prediction of the wall temperature was verified.

Figure 4 Overview of combustion chamber of LE-9 engine and cause of openings on wallsurface(3)

Issues and corrective measure - Cracking on FTP rotor blade
Figure 5 is an overview of cracking on the FTP second-stage rotor blade. Fatigue
fracture surfaces were found on two of the seventy-six second-stage rotor blades. In order toinvestigate the cause, detailed analysis of the actual fracture surface was performed and inparticular, the correlation between the fracture origin and the high stress point on the vibration
mode and the correlation between beach mark and striation characteristics and load history
during QT test were organized to identify the vibration mode involved. The stress generated inthat mode was verified by a blade vibration measurement during turbine pump stand-alone testin addition to detailed analysis. In this test, the turbine pump was actually operated and thevibration response (strain) on the turbine blade was directly measured and evaluated. As a resultof this cause investigation, it was determined that fatigue accumulated and progressed due toresonance of natural vibration mode, which was initially regarded as having a none-criticaleffect.

Figure 5 Overview of liquid hydrogen turbine pump (FTP) of LE-9 engine and cause ofcracking

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As a corrective measure, the turbine blade design (the number of blades and blade shape)
was changed to exclude all natural vibration modes from the turbine pump operating range. Inaddition, although the issue was found in FTP this time, the design of the liquid oxygen turbine
pump (OTP) was also changed with the same policy as much as possible.

3.2
(1)

Development of system and subsystems
Subsystem test
As shown in Figure 3, the development of the subsystem is almost complete except for
the qualification test of the LE-9 engine. The qualification firing test of the LE-9 engine will beconducted after October 2021 using one that reflects the design changes and corrective
measures shown in Section 3.1. It is planned that in the first half of the qualification firing test
the strain response on the turbine rotor blade will be measured with an FTP/OTP vibration
measurement device to verify the validity of the corrective measures.
The status of development and testing of other major subsystems, namely structural,propulsion and electrical subsystems, is summarized as follows. With regard to the structuralsubsystem, the strength and stiffness tests of each structure have been completed. As for thepayload fairing, in addition to the strength and stiffness test, a separation test under anon-ground and atmospheric-pressure environment where the gravitational acceleration is 1G
was conducted and it was confirmed that the behavior at the time of separation was as designed(Figure 6).

Figure 6

Overview of the H3 launch vehicle structure and fairing separation test

With regard to the propulsion subsystem, a battleship firing test (BFT) of the first stage
and a captive firing test (CFT) of the second stage have been conducted to complete verificationof the first stage and the second stage including the structural and electrical systems in addition
to the propulsion system and engines (Figure 7). The BFT of the first stage was conducted in
two configurations. i.e. two engine-configuration and three engine-configuration. Eight firing
tests in total were conducted with a cumulative time period of about 250 seconds. The CFT ofthe second stage was conducted using an actual flight hardware. Three firing tests in total wereconducted with a cumulative time period of about 1500 seconds. Through these tests, theignition and shut-off characteristics of the engine, the supply of propellant, the control of tankpressure, the control of engine steering, and the vibration and thermal environment of thevehicle and equipment were verified.

Figure 7

BFT of 1st stage (left) and CFT of 2nd stage (right)

Mitsubishi Heavy Industries Technical Review Vol. 58 No. 4 (December 2021)
6With regard to the electrical subsystem, in addition to the development and testing of theavionics components alone, the electrical subsystem test to verify the functional performance ofthe entire vehicle with all the avionics components connected through a network has been
completed (Figure 8). Some avionics components were modified in response to the issues
found in the latter phase of the development and have undergone additional verification.

Figure 8 Electrical subsystem test(2)System test
The first test flight vehicle (TF#1: Test Flight No. 1) i.e. the first- and second-stage
vehicles was shipped from MHI Tobishima Plant in January 2021 and the entire vehicle wasassembled at the Tanegashima Space Center (Figure 9). After that, full-vehicle system tests andverification tests with the vehicle combined with ground facilities have been conducted.
In March 2021, wet dress rehearsal (cryogenic test) was conducted (Figure 10). In thistest, the vehicle was moved from the assembly building to the launch pad and the all sameprocedures as the actual launch, from propellant loading, checkout of the functions of each partof the vehicle and the automatic countdown sequence until sending the main engine ignitioncommand, was confirmed. All planned data was successfully obtained and a couple of items
were identified which need modification of hardware and operation for flight.
After the wet dress rehearsal, a full-vehicle modal survey, attitude control system test,
EMC test and umbilical carrier separation test were conducted as system tests. As for theattitude control system test, the engine steering signal output was measured when the vehicle
was excited by a shaker and it was confirmed that the characteristics of the entire attitudecontrol system from input to output were as designed. In addition, as part of the EMC test, it
was confirmed that the battery startup and the first stage engine steering operate normally using
270-volt thermal batteries. The first stage engine actuator of the H3 launch vehicle was changed
from hydraulic powered to electric powered, so the feasibility of a high-powered control system
was one of the important matters to be confirmed.
After this, the full-vehicle system will undergo a CFT of the first stage while standing atthe launch pad after the completion of the qualification test of the LE-9 engine. This test is not
only the verification of the first stage, but also the pre-flight final verification of the full-vehicle
system combined with the ground system.

Figure 9

Full-vehicle assembly of first test vehicle at Tanegashima Space CenterMitsubishi Heavy Industries Technical Review Vol. 58 No. 4 (December 2021)
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Figure 10

Wet dress rehearsal (cryogenic test)|4. Future prospects
It is planned that two test vehicles (TF1 and TF2) of the H3 will be launched by 2022 andthen the H3 will be brought into the commercial market. We have already received a large numberof quotations from our customers, which shows high expectation to the H3. On the other hand, inthe commercial market, price destruction by SpaceX has progressed and competition has intensified
compared to that at the time when the development of the H3 launch vehicle commenced. Newlaunch vehicles developed by other countries such as Ariane 6 of Ariane Space in Europe, New
Glenn of Blue Origin in the U.S. and Vulcan of ULA in the U.S. are expected to be brought tomarket at the same timing as the H3 launch vehicle and further low-price competition is predicted.
Demand for launch vehicles is also diversifying, such as the launch of many small satellites formissions of the Constellation program, deep space missions (the Moon and Mars), etc. and is
expected to change further due to reduction in launch cost and increase in launch capability.
In order to respond to these changes in the environment and maintain the industry base forthe flagship Japanese launch vehicle, the H3 launch vehicle needs to be evolved and enhancedcontinuously. Figure 11 presents one example of the future evolution plans. In this plan, the H3 isused to deliver cargo to the Gateway (multi-purpose outpost orbiting the Moon) as an international
contribution to the crewed lunar exploration program (Artemis program) planned by the UnitedStates. In this plan, the launch capability will be greatly improved by clustering the first stagevehicle.

Figure 11

One of the H3 evolution plans

In order to drastically reduce the launch cost, "partial or complete reuse" of the vehicle,
which has been put into practical use by SpaceX and has been worked on for launch vehicles
developed by various countries, is considered essential. Future plans for flagship launch vehicles
and the roadmap for the realization of an innovative future transport system have been examined byMitsubishi Heavy Industries Technical Review Vol. 58 No. 4 (December 2021)
8a subcommittee established in the Space Development and Utilization Division of the Ministry ofEducation, Culture, Sports, Science and Technology and an interim report(3) was released in June
2021. In this report, it is planned as the first step that a subscale demonstration vehicle will belaunched around 2026 and an actual-operational vehicle will be launched around 2030, in order torealize the reuse of the first-stage vehicle. As the next step, the promotion of complete reuse
including the second-stage vehicle is planned, aiming to reduce the launch cost to about 1/10 of thatof the H3 by the first half of 2040.
MHI will work on technological development in collaboration with JAXA and related
ministries and agencies in order to realize an innovative future transport system in parallel with theshort- and medium-term continuous improvement of the H3.

|5. Conclusion
The concept design of the H3 launch vehicle commenced in April 2014 and its development
is currently in the final stage of the test and verification phase. The development of subsystems has
been completed except for the LE-9 engine. The first test vehicle has already been shipped to theTanegashima Space Center and launch preparations are underway. At the Tanegashima Space
Center, the system tests including the wet dress rehearsal using the first test vehicle have been
conducted and verification of the full-vehicle system and the combination of the vehicle and theground facilities has proceeded.
Although the LE-9 engine was found to have issues in the qualification firing test. the design
was changed and preparation for another qualification firing test of the engine for which thecorrective measure has been taken is underway. It is planned that the first test vehicle will belaunched after the completion of the qualification test of the LE-9 and the CFT of the first stage at
the launch site. We will cooperate with internal and external parties to conduct the remaining
development tests and the launch of test vehicles (first and second vehicle) and complete a reliablevehicle, aiming at bringing the H3 launch vehicle to the commercial market as soon as possible.
With the intensifying price competition and diversifying missions, the commercial market
has been changing rapidly compared to that at the beginning of the H3 development. In order to
respond to such changes in the market environment, continuous evolution and enhancement of theH3 launch vehicle is essential. In particular, the key to cost reduction is the reuse of the vehicle. We
will work on technological development for its realization in collaboration with JAXA and related
ministries and agencies.

References
(1)
(2)
(3)

Atsutoshi Tamura, et al., Development of Japan’s Next Flagship Launch Vehicle, Mitsubishi Heavy
Industries Technical Review, Vol.51, No.4 (2014), p38～43
Tokio Nara, et al., Development Status of H3 Launch Vehicle, Mitsubishi Heavy Industries Technical
Review, Vol. 54, No. 4 (2017), p30～37
The Interim Report of the Roadmap Study Group for Realization of an Innovative Future SpaceTransportation System
https://www.mext.go.jp/b_menu/shingi/chousa/kaihatu/024/toushin/mext_00823.html