Feasibility Study of the Implementation of a Space Sunshade Near the First Lagrangian Point

DEGREE PROJECT IN MECHANICAL ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2020 Feasibility study of the implementation of a space sunshade near the first Lagrangian point MARÍA GARCÍA DE HERREROS MICIANO KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES Feasibility study of the implementation of a space sunshade near the first Lagrangian point MARÍA GARCÍA DE HERREROS MICIANO Master in Aerospace Engineering Date: July 15, 2020 Supervisor: Christer Fuglesang Examiner: Christer Fuglesang School of Engineering Sciences Swedish title: Möjlighetsstudie av solparasoll i rymden nära Lagrangepunt L1 III Abstract The lack of strong measures to avoid the possible fatal consequences of global warming is pushing researchers to look for other alternatives such as geoengineering. Within geoengineering, this study focuses on the space based solar radiation management methods. More precisely, the project evaluates the feasibility of implementing a space sun shade near the first Lagrangian point in the Sun-Earth system within a thirty year period time from now. The study is structured in three main blocks: spacecraft configuration, trajectory definition and launch. An analysis looking at the minimum cost system was carried out, starting with the definition of the mass and size of spacecraft. Furthermore, an optimization of the trajectory was developed in order to minimize the travel time to the vicinity of the Lagrangian point. The shades will be formed by swarms of 10 000 m2 solar sails that will cover an area of 6:3 × 1012 m2 with a total mass of around 5:7 × 1010 kg. The sails will be injected into a LEO and will start a trajectory to the vicinity of the first Lagrangian point that will take around 2.3 years. The total cost of the project is approximated to be 10 trillion dollars. The mission appears to be feasible from a technological point of view, with some development needed in the attitude control subsystem. The main challenge will be the launch of all the spacecraft. A space mission of this dimensions has never been attempted before so it will require a big advance from the launch vehicle industry. IV Sammanfattning Bristen på åtgärder för att undvika de konsekvenser som den globala uppvär- mingen leder till, har drivit forskare att leta efter alternativa lösningar, varav geoengineering är en av dem. Denna studie fokuserar på rymdbaserade strål- hanteringsmetoder, mer specifikt på hur huruvida implementationer av solpa- rasoller nära Lagrangepunkten L1 i sol-jord-systemet är möjlig eller ej. Studi- en är strukturerad i tre huvudsakliga block: rymdskeppskonfiguration, banade- finition och uppskjutning. Med målet att minimera kostnaderna, definierades rymdskeppets utforming, massa och storlek. Vidare så, optimerades vägen till närheten av L1 med avseende på att minimera tiden. Solparasollerna kommer vara placerade i svärmar med en area på 10 000 m2 vardera, totalt kommer solparasollerna att täcka en yta av 6:3 × 1012 m2 med en total massa på 5:7 × 1010 kg. Solparasollerna kommer skjutas upp till LEO och därefter star- ta sin resa till närheten av L1, vilket kommer ta cirka 2.3 år. Totala kostanden för projektet uppskattas till 10 billioner dollar. Efter genomförd studie visades projektet vara genomförbart sett från en teknisk synvinkel, men vidare studi- er behövs göras för att utveckla och fastställa styrsystemet. Huvudutmaningen kommer att vara uppskjutningen av rymdskeppen, då det kräver stora framsteg och utveckling inom rymdindustrin. Contents 1 Introduction 1 1.1 Current Climate Situation and Policies . .1 1.2 Geoengineering the Climate . .3 1.3 Literature Review on Space Sun Shades . .4 1.4 Present Work . .5 2 Methodology 7 2.1 Initial Assumptions . .7 2.2 Launch . .8 2.2.1 Launcher Selection and Assumptions . .8 2.2.2 Target orbit . .9 2.3 Trajectory . 11 2.3.1 Reference Frames . 11 2.3.2 Solar Sail Dynamics . 12 2.3.3 New Equilibrium Point . 15 2.3.4 Escape Trajectory Optimization . 15 2.3.5 Trajectory to Sub-L1 Optimization . 16 2.4 Spacecraft Configuration . 18 2.4.1 Total Mass and Size Study . 19 2.4.2 Mass Budget . 20 2.4.3 Control . 21 3 Results 24 3.1 Spacecraft Configuration . 24 3.1.1 Total Mass and Size . 24 3.1.2 Mass Budget . 28 3.1.3 Control . 29 3.2 Launch . 31 3.2.1 Launcher Selection . 31 V VI CONTENTS 3.2.2 Launch in Numbers . 32 3.2.3 Target Orbit Definition . 33 3.3 Final Trajectory . 33 3.3.1 Escape Trajectory . 34 3.3.2 Travel to Sub-L1 . 35 4 Cost Analysis 40 4.1 Launch Cost . 40 4.2 Spacecraft Cost . 41 5 Discussion 43 5.1 Spacecraft . 43 5.2 Launch . 46 5.2.1 Launch in Numbers . 46 5.2.2 Environmental Impact . 47 5.3 Trajectory Results . 49 5.4 Cost . 50 6 Conclusions 52 Chapter 1 Introduction The emissions of greenhouse gases (GHG) have been changing the planet for decades but it was not until fifteen years ago, with the Kyoto Protocol, that climate change started to get attention from governments. Since then, the im- portance of it has been growing. However, up to now actions against it have not been taken with the urgency that the problem requires in order to avoid possible fatal consequences [1] [2]. This is pushing researchers to look for alternatives away from the reduction of greenhouse gases emissions, which as time passes seems harder to achieve on time and requires the commitment of the whole world [3] [4]. 1.1 Current Climate Situation and Policies Since the pre-industrial age, the world’s climate has changed significantly be- cause of the emission of GHG, but there has been a great acceleration of these changes in the past fifty years. The main contribution to the emissions is fossil carbon dioxide (CO2), which mainly comes form energy and industrial use. This explains the acceleration during the industrial era and specially in the last decades. After 2010, GHG emissions have been growing at a rate of 1.5 per cent per year and the peak of these emissions does not seem like it is going to take place any time soon [2]. Every year that this peak is delayed translates into a larger rise of the global mean temperature by the end of the century. Different scenarios are considered by the United Nations–sponsored Intergovernmental Panel on Climate Change concluding that in order to stabilize the mean global temperature around 2◦C above pre-industrial levels by 2100, this peak should 1 2 CHAPTER 1. INTRODUCTION take place between 2020 and 2050 [5]. By 2017 temperature had already risen 1◦C [5] and as a consequence global warming effects are already observable on the planet, although these will be more intense in the following decades [6]. Some of the most important are the rise of sea level as a result of the melting ice, the increase of extreme weather events such as droughts, heavy rainfalls or heatwaves, the extinction of plant and animal species, the reduction of crop fields and the increase of wildfires [7]. All these phenomena translate in large costs for society (increase in mor- tality, consequences in human health) and economy (damage of infrastructure, agriculture, tourism and energy sectors). The most recent international agreement regarding climate change was the Paris Agreement (2016), ratified by 187 countries as of 2019. Here, all signa- tories compromised to: “holding the increase in the global average temperature to well below 2◦C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5◦C" [8]. Therefore, the upper limit that should not be trespassed is nowadays set to 2◦C. It must be kept in mind that the 0.5◦C difference between both limits means a significant increase in the intensity of the global warming effects mentioned above [5]. With the current climate policies and the ones expected to be implemented in the following years, by the end of the century temperature is predicted to rise between 2.6◦C and 3.7◦C, depending on the compliance with these policies [1]. Thus, it seems clear that stronger measures need to be taken to reduce GHG emissions in order to achieve the defined goals. To meet the 1.5◦C limit, global CO2 emissions would need to reach zero by 2050 and keep decreasing afterwards. This means that emissions would need to start dropping immedi- ately at a faster rate than ever and once zero emissions were reached, carbon removal techniques would have to be implemented [9]. The chances of achiev- ing these objectives seem remote, specially keeping in mind that, in order to do so, an international response needs to be coordinated on a global level. Oth- erwise, despite all the climate policies that are being implemented in a lot of countries, the decrease of emissions in these will not be enough to offset the increase in others [2]. CHAPTER 1. INTRODUCTION 3 1.2 Geoengineering the Climate As it has been described before, historically the dominant approach to fight climate change has been the reduction of GHG emissions. While the achieve- ment of the necessary levels of emissions in time is each year further away from reaching the goal, other alternatives are being considered in addition to these reductions. One of the options is so-called geoengineering, which consists on deliberately modifying Earth’s environment in order to counteract climate change. As addressed in Geoengineering the climate. Science, governance and uncertainty [3], these measures are still highly controversial but they are alternatives that can provide help, mitigating both short-term and long-term global warming effects.

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