1. Simulation of Space Habitat

1.1. Mass Flow Analysis of Controlled Ecological Life Support Systems (CELSS) 

A Controlled Ecological Life Support System (CELSS) is a self-supporting life support system for space stations and colonies based on physicochemical and biological systems. It consists of humans, animals, plants, and a controlled recycling system. Plants supply food to the humans or reproduce water and gases by photosynthesis, while controlled recycling systems recycle waste from humans and plants physicochemically. We developed a dynamic simulation model for analyzing the mass flow of a CELSS. We applied the modeling method to mass flow analysis and designed a control system for a Closed Ecological Experiment System (CEEF) at the Institute for Environmental Sciences (IES).

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Fig. 1 Closed Ecological Experiment System (CEEF) cited from the IES web page

1.2. Habitation Experiment at Mars Desert Research Station

The Mars Desert Research Station (MDRS), owned and operated by the Mars Society, is a full-scale analog facility in Utah that supports Earth-based research in pursuit of the technology, operations, and science required for human space exploration. (http://mdrs.marssociety.org/home/about-mdrs accessed Nov. 29, 2015)

In 2013, Mars Society Japan selected the members for Team Nippon, which I served as commander. The team consisted of six crewmembers and conducted a two-week habitation experiment regarding space habitat, space food, and extravehicular activity (EVA) on Mars surface in 2014.

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Fig. 2 Crewmembers on Crew 137 at MDRS

1.3. Thermo-fluid Analysis in Habitat

The first cylinder-shaped space colony was proposed by G. O’Neill in 1974 and named “Island Three”. It measured 6.2 km in diameter and 30 km in length. It was designed for up to ten million people to live in it. The cylinder rotated 0.55 rpm to create an artificial gravity of 1 g.

The inside wall of the cylinder was divided into six equal-area sections that ran the length of the cylinder. The sections alternated between habitable land surfaces and transparent windows with three of each in total. Each window had a movable mirror installed to reflect sun light. It could artificially create days, nights, and seasons. Matsuda’s research on the space colony predicted that the temperature difference between the habitable land sections and window sections caused air to circulate by window-wind that originated from the window sections and blew towards to the land sections.

I developed a Computer Fluid Dynamics (CFD) model for the Island Three space colony using OpenFoam, an open source CFD software package. I verified and validated the numerical model and analyzed ideal environmental conditions for humans and crops by changing the heat flux from outside sunlight. The model could trace air transfer, heat transfer, and carbon dioxide diffusion under artificial gravity.

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Fig. 3 Carbon dioxide diffusion in Island Three


2. Design and Control of Space Habitat System 

We developed a design support tool and scheduling method for an Environment Control and Life Support System (ECLSS). The latest version of the tool, named SICLE (Simulator of Material Circulation Control System), was developed by Space Systems Development Corporation (SSD). Mass flow analysis of food production, food supply, and recycling of water, air, and waste was conducted using the SICLE. It can be applied to design research and control research for an ECLSS.

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Fig. 4 Snapshot of SICLE provided by SSD

3. Planetary Surface Exploration 

I developed a rover routing method using Dijkstra algorithm. I applied it to a rover routing problem on the lunar surface based on KAGUYA’s laser altitude data. In addition, we are developing a planetary surface exploration system to support extravehicular activity (EVA) on Mars’s surface based on lessons learned from results obtained from Crew 137 in 2014. The system will consist of unmanned rovers, manned rovers, crew, and reconnaissance aircraft. A part of this system will be tested by Crew 165 at MDRS in 2016
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Fig. 5 Rover route on lunar surface calculated using Dijkstra algorithm

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Fig. 6 Extravehicular activity using an All Terrain Vehicle (ATV) by Crew 137 at MDRS

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Fig. 7 Altitude and speed changes of crew expedition

 
現在、Mars Society International Gemini Mars Design Competitionのための準備をしています。
前回のコンテストでは2018年のHigh energy trajectoryを利用する必要がありましたが、
次回のコンテストでは、2024年までに打ち上げればよいので、複数回の打ち上げウィンドウの利用が可能です。Low energy trajectoryの利用も可能です。火星探査の打ち上げウィンドウを考えていると、ポークチョッププロットとい用語が出てきます。

ポークチョッププロットは、特定の惑星間飛行において、出発日(x軸)と到着日(y軸)に対する出発エネルギーC3を等高線で表したものです。打ち上げウィンドウの検討に利用します。

地球から火星への惑星間軌道について、
L.E. George and L.D. Kos,
Interplanetary Mission Design Handbook:
Earth-to-Mars Mission Opportunities and
Mars-to-Earth Return Opportunities 2009-2024,
July 1998, NASA/TM-1998-208533
に2009年から2024年まで詳細な結果が出ています。

例えば2014年のクルーミッション(High energy trajectory)の例を示します。
180日で火星へ移動し、約535-651日間、火星に滞在する軌道です。

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 2014 primary piloted opportunity

次の図がポークチョッププロットになります。
上が貨物ミッション、下がクルーミッションです。
有人仕様の宇宙船をHigh energy trajectoryで火星へ投入できる打ち上げシステムは現在はありません。
無人探査機は急ぐ必要がないので、既存の打ち上げシステムでたくさん投入されていますが。
次は、いつ地球を出発しようか?

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 Earth-Mars Trajectories
 2013/14 Conjunction Class
 C3 (Departure Energy) km2/sec2

インターネット上には C3 Planner もあるんですね。

 

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