Abbreviations CM: Command Module EDS: Earth Departure Stage ESAS: Exploration Systems Architecture Study LEO: Low Earth Orbit LLO: Low Lunar Orbit LM: Lunar Module LMa: Lunar Module -Ascent Stage LMd: Lunar Module -Descent Stage LOI: Lunar-Orbit Insertion SM: Service Module TEI: Trans-Earth Injection TEO: Trans-Earth Orbit TLI: Trans-Lunar Injection TLO: Trans-Lunar Orbit 1. Introduction In January 2004, George W Bush, the president of the United States, disclosed a new space exploration plan called gBush visionh, which includes greturn to the moonh policy. Following the Bush vision, a lot of countries such as China, India and Russia brought out their lunar exploration plan. In Japan, JAXA also made its vision, which aims to send Japanese astronauts to the moon. As the first step, the lunar orbiting explorer gKaguya h was sent to the lunar orbit in autumn, 2007. MHI has been studying transportation architecture for future lunar exploration in order to clarify its goal and roadmap, which will stimulate discussion about the exploration and promote launching program following Kaguya. This paper states (1) transportation architecture to send astronauts to the moon in the early phase, and (2) transportation options for unmanned lunar exploration, as a precursor of manned lunar exploration. 2. Manned Lunar Transportation 2.1 Mission Model The following mission model, for our study, is set by reference to the NASA ESAS report [1], RSC Energiafs lunar transportation concept [2] and Apollo. -Number of crew: 3 (2 for lunar surface) -Mission time: 21days, -7days: at LEO for Rendezvous and docking (considering 6-launch scheme, see Figure 2) -7days: at lunar surface -7days: at Earth-Lunar transfer orbit, go and back total -Cargo mass: 1000kg 2.2 Transportation Options for Tradeoff Two options are selected. One is g2-launch schemeh which is as almost same as ESAS. The other is g6-launch schemeh which is modified the RSC Energiafs concept. The 2-launch scheme uses one huge unmanned cargo launcher and one relatively small manned launcher. Figure 1 depicts the mission profile of the 2-launch scheme. In this scheme, a manned module and a cargo module rendezvous at LEO, and an Earth Departure Stage (EDS) performs TLI burn. When it arrives at the moon, a Lunar Module (LM) performs LOI burn. Astronauts transfer from a Command Module (CM) to the LM, and then the LM undocked and performs a descent to the lunar surface. After 7 days on the lunar surface, a Lunar Module Ascent Stage (LMa) lifts off from lunar surface, and the LMa and the CM combined with a Service Module (SM) rendezvous and dock at LLO. Astronauts transfer to CM, and SM performs TEI burn. The only CM comes back to the Earth while SM is disposed just before reentry. Figure 1 mission profile | 2-launch scheme Figure 2 mission profile | 6-launch scheme On the other hand, the 6-launch scheme uses some medium launchers compared to the huge launcher required for the 2-launch scheme. Figure 2 shows the mission profile of the 6-launch scheme. In this scheme, 1 manned module and 5 unmanned modules rendezvous and dock at LEO, and 2 transportation complexes are assembled as shown in Figure 3. These complexes depart to the moon Courtesy of NASA separately and then rendezvous at LLO. Figure 3 module description for 6-launch scheme 2.3 Comparison In order to compare two schemes, we estimate masses of each modules and required rocket launch capability of each launch scheme considering the mission model and required delta-V. The result is shown in Figure 4. The 2-launch scheme needs only 2 rendezvous-dockings, but requires huge launcher of about 200 tons launch capability for LEO. So the 2-launch scheme fits for one country that has technologies and budget to construct and operate such a huge launcher. On the other hand, the 6-launch scheme needs 6 rendezvous docking, but required launch capability is about 25 tons for LEO. For Japan, though itfs difficult to develop a new huge launcher with 200 tons launch capability considering our budget size, we could develop a launcher with about 25 tons launch capability with heritage of H-IIA/B launch vehicle family. In addition, considering international cooperation approach, the 6-launch scheme is preferable. For example, cooperative countries of the international cooperation for lunar exploration could share crews, development and launch of the necessary modules, depending on their technologies and strategies. Figure 4 Comparison of 2-launch scheme and 6-launch scheme 3. Unmanned Lunar Transportation 3.1 Mission Candidates Candidates of unmanned mission before manned mission is as follows. -Lunar orbiting exploration (such as Kaguya) -Lunar surface exploration -Lunar sample return -Lunar cargo transportation 3.2 Transportation Scheme and Transport Capability We studied transportation plan and transportation capability for each mission. In this study, we selected candidate launchers from current H-IIA/B family and future H-IIB+ or H-X launcher that has 25ton launch capability, required for manned lunar mission (see Figure 4). Figure 5 shows the launcher plan and Figure 6 shows each transportation capabilities. As shown in these figures, we can chose wide variety of launcher and fleet corresponding to mission requirements. EDS1 - A : Earth Departure Stage1-A, EDS2 -A : Earth Departure Stage2-A, CM : Command Module, SM : Service Module, for TEManned I Transportation Complex for TLI for TLI/ LOI EDS1 -L : Earth Departure Stage1-L, EDS2 -L : Earth Departure Stage2-L, LMd : Lunar Module Descent Stage, LMa : Lunar Module Ascent Stage, Lunar Lander Transportation Complex for TLI for TLI/ LOI for Ascend from Lunar Surface for Descend to Lunar Surface Re-entry Capsule Figure 5 Launcher and fleet plan for unmanned lunar exploration Figure 6 variety of launch capability 4. Conclusion For manned lunar exploration, we studied two types of launch scheme. The 6-launch scheme is preferable for Japan, considering launcher size and international cooperation approach. The 6-launch scheme requires a new heavy launcher carrying 25 tons class payload into LEO which launcher can be developed with heritage of H-IIA/B family. Major issues for our further study are 6-launch timing and LEO rendezvous (including backup planning), propellant management for long coast, emergency escape and abort scenario. For unmanned lunar exploration, we showed variety of launch capability of H-IIA/B family, future H-IIB+ (20 tons class), H-X (25 tons class), and combination of them corresponding to unmanned lunar exploration candidates. We will study and brush up our concept for manned and unmanned missions in order to make future lunar explorations a reality. Reference [1] gNASAfs Exploration Systems Architecture Study: Final Reporth, NASA-TM-2005-214062, November 2005 [2] gConcept of Russian Manned Space Navigation Developmenth, http://www.energia.ru/eng/news/news-2006/public_07-01.html, RSC ENERGIA Web Site 0 5 10 15 20 Mass[ton] Lunar Landing Lunar Cargo Transportation Lunar Manned Transportation Sample Return H-IIA2022 Around the Moon iSELENE) No Landing iLLO `2tonj P/L=290kg P/L=450kg Capsule =30kg FLLO Injection Mass FPayload Mass FLunar Lander Dry Mass H-IIB+ Capsule =50kg P/L=1ton SM Dry 0 5 10 15 20 H-IIA204 H-IIB H-IIB‚˜2 H-X‚˜3 H-X‚˜6 P/L=730kg P/L=5600kg Capsule=5700kg MasFCourtesy of JAXA