Space Elevator A New Way To Gain Orbit Adil Oubou 5/3/2014 Abstract After 56 years of great space exploration, the space flight program found itself asking an intriguing question: What’s next? Should humans constrain the space program to low Earth orbit, revisit the moon, or simply go beyond anything they have done before? No matter what the next step is, there is a great need for a reliable, safe, affordable and easy method of gaining orbit. The space elevator concept discussed in this report, based on the design provided in Peter Swan’s book “Space Elevators: An Assessment of the Technological Feasibility and the Way Forward“, shines the light on an economically and technologically feasible solution within the next two decades that will lift payloads including humans from the earth’s surface into space at a greater capacity than current rockets while significantly lowering cost to $500/kg. The system design includes a tether line that extends from the Earth’s surface to an altitude of 100,000 km that utilizes electrical motor driven climbers to gain orbit. The success feasibility of this space flight system is highly dependent on the development of Carbon Nanotube (CNT) material, which will provide high strength and low mass properties for the space elevator system components to withstand environmental and operational stresses. Table of Contents 1.0 The New Way to Orbit ....................................................................................................... 4 2.0 Why Space Elevator? ......................................................................................................... 4 2.1 Purpose ...................................................................................................................................... 4 2.2 Advantages ................................................................................................................................ 4 3.0 System Architecture .......................................................................................................... 5 3.1 System Overview ....................................................................................................................... 5 3.2 Climbers .................................................................................................................................... 6 3.2.1 Mass Budget ............................................................................................................................... 7 3.2.2 Motor Drive Apparatus ............................................................................................................... 7 3.2.3 Power Requirements ................................................................................................................... 7 3.3 Tether ........................................................................................................................................ 8 3.3.1 Design Requirements .................................................................................................................. 8 3.3.2 Tether Material ........................................................................................................................... 8 3.4 GEO Node Spacecraft ................................................................................................................ 10 3.5 Marine Node ............................................................................................................................ 10 3.6 Apex Anchor ............................................................................................................................. 11 4.0 Concept of Operation ...................................................................................................... 11 4.1 Pre-mission .............................................................................................................................. 11 4.2 Flight .................................................................................................................................... 12 5.0 Cost Estimates ................................................................................................................ 12 6.0 Conclusion ...................................................................................................................... 13 ReFerences ............................................................................................................................ 14 2 List of Figures Figure 1. System Diagram of the Space Elevator ........................................................................................ 5 Figure 2. Space Elevator Orbital Dynamics ................................................................................................ 6 Figure 3. Climber Design Model ................................................................................................................. 6 List of Tables Table 1. Climber Subsystem Mass Breakdown [kg] .................................................................................... 7 Table 2. Forces Experienced for the 7 Climbers Operation ......................................................................... 8 Table 3. Tether Carbon Nanotube Characteristics ....................................................................................... 9 Table 4. Design Requirements for the Marine Node ................................................................................. 11 Table 5. Climb Phase Breakdown ............................................................................................................. 12 Table 6. Initial Capital Cost for Space Elevator .......................................................................................... 12 Table 7. Operational Cost of Space Elevator ............................................................................................. 12 3 1.0 The New Way to Orbit The unknown drives humans. Space exploration was essentially derived from that concept. However, beyond our natural curiosity, new concepts such as energy shortage, atmospheric pollution and the chance of high impact global catastrophe are driving humans to extend our existence beyond Earth. Although we have experienced significant advancements in space flight technologies over the last four decades, they are just not up to par for us humans to achieve our ambitious space travel goals. Current rockets are expensive, time-heavy and environmentally harmful. There is a great need for a method to gain orbit that will open up the solar system for exploration and take humans to heights never before reached, while having minimum environmental impact. Could this be a space elevator? Over the past decade, the space elevator concept has moved from a fictional Star Treck point of view, to a feasible megaproject that will lift payloads and eventually people from the Earth’s surface into space at much lower costs. This report explores the popular space elevator tether design concept and its technical feasibility within the near future. 2.0 Why Space Elevator? 2.1 Purpose The space elevator system will lift payload as well as humans from the earth’s surface into space at a greater capacity than current rockets, in a safe, reliable and routine manner for an estimated low cost of $500/kg. Achieving a method to reach the GEO altitude will open the doors for the following important missions: Ø Space transportation station Ø Assembly station for spacecrafts Ø Space tourism & colonization 2.2 Advantages § Low cost to GEO § Easy delivery to GEO within a week § Reliable and routine operations § Access to orbiting satellites (daily launches) § Low g’s (human spaceflight) § Safe § Environmentally friendly § Permanent infrastructure § No consumption of fuel § High cargo capacity § No space Debris § Allow for space systems to be § Floating launch facility designed and constructed 4 3.0 System Architecture 3.1 System Overview The system consists of a 100,000km long tether balanced about a node in geosynchronous orbit (GEO) and extending down to an anchor point on Earth, and up to an apex anchor at an altitude of 100,000km. Tether climbers, which are electrically powered spacecrafts, will serve as the elevator cabins that will travel up or down the tether from earth’s surface to the apex anchor, where their speed is sufficient enough for interplanetary travel. Figure 1 shows the space elevator system nodal layout along the tether line. Figure 1. System Diagram of the Space Elevator It is important to consider the system dynamics of the tether elevator from Earth’s surface to the 100,000 km altitude in space. Close to the Earth’s surface, the gravitational forces are strong, decreasing as a function of altitude as the elevator climbs to space. On the other hand, the centrifugal forces acting on the space elevator, which point away from Earth are weaker near Earth’s surface and get stronger as the elevator goes up in altitude. In order to have a balanced tether line for the elevator, the forces acting on the elevator above the GEO point, must be balanced with the forces acting below the GEO node. On the other hand, the angular momentum must also be balanced around the GEO node, to keep the elevator stable. Considering the mass below the GEO would be significantly heavy, the apex anchor will serve as a counterweight to keep the dynamics of the elevator balanced and stable. Since the GEO will be the center of mass, it will experience the highest magnitudes of stress, therefore requiring a thicker tether compared to near the