Lunar Spaceport Architectures Jeffrey Montes, Fellow, Open Lunar Foundation
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Lunar Spaceport Architectures Jeffrey Montes, Fellow, Open Lunar Foundation Background / Motivation Lunar spaceports (a.k.a.. launch/ profit organization working on policy and landing pads) will be a cornerstone of partnerships that support a sustainable all but the most anemic lunar futures. lunar settlement driven by open values. Undoubtedly they are critical to any Consistent with this spirit, this is a working sustainable presence. The central problem document for designers, engineers, and spaceports address is the detrimental policy-makers interested in understanding effects of ejecta, the global dispersal of this problem or applying the approach to lunar surface material (rocks, dust, etc.), other problems. caused by landing on and launching atop unprotected lunar ground. Because the This isn't an engineering trade study, Moon has no atmosphere, ejecta goes it isn't built on previously unpublished fast and far—potentially blanketing the information, and it isn't intended as a set globe at velocities that could damage of ready-made designs to choose from. infrastructure and undermine science, It is an architectural and conceptual and reaching altitudes where satellites exploration through geometry, and orbital habitats live. This document mechanism, and concept of operation is the output of a research fellowship (CONOPS). taking a new look at lunar spaceports with Open Lunar Foundation, a non- Fig. 1: Stages of rocket exhaust ejecta beneath an Apollo Lunar Module (Metzger et al., 2011). 1 Design Spaces Lunar Spaceport Architecture In The Theoretical Minimum Susskind and bounded by four designs as four corners A spaceport is a kind of armor for the There is increasing attention on in-Space Hrabovsky define a concept called a state define a square room. Each design lunar surface in that it protects the ground resources as they relate to the hopeful space: represents a corner of that space, an from the destructive force of rocket cis-lunar economy and to lunar surface extreme value. None of the designs engine exhaust and prevents the ground infrastructure. Among that infrastructure, "...the collection of all states occupied by a from becoming a spray of high-velocity spaceports stand out. For the "vibrant system is its ...state space. The state space is ought to be taken as the solution; instead not ordinary space; it's a mathematical set they should aid designers in inventing projectiles. In the absence of this surface Earth-Moon future" NASA has outlined whose elements label the possible states of the unexpected hybrids. armor, everything around the landing with the Artemis program, shuttling to and system. [p.3] site would need to be armored and thus from the surface will be foundational and Design spaces are useful for early stage more massive, indiscriminately driving commonplace. A spaceport might itself be Similar to a state space, a design space problems. For a technology that does engineering margins. While many surface a product of an indigenous lunar material is a solution domain defined by relatively not yet exist a design space paints the assets will need to be engineered against economy, or it might, like a spacecraft, detailed designs aimed at a common scene and sets the ground for informed the likelihood of micrometeorite impact be a product of Earth and imported to problem. The one-dimensional space scrutiny. For problems without real-world and other incidental damage, the risk of the Moon. The structural, material and between 0 and 1 is a continuum with an solution precedents a design space ejecta damage will result in unnecessarily production differences between in situ infinite number of values. For difficult and can guide debates. It can be helpful for large margins that levy substantial and imported artifacts has a fundamental important problems at an early stage of problems where a design framework has penalties felt at the system level. For this effect on their design and is the first of two development (such as lunar spaceports), not been established. Designers flourish on reason, investing in spaceports early is axes of the design space. fleshing out the extreme cases (the 0 and constraints because they need a working critical for asset longevity, risk reduction, the 1) can more be effective at moving a model of a problem and its boundaries to coordination and policy, human safety, In Pad for Humanity: Lunar Spaceports as community of designers towards discovery understand which of those boundaries to and programmatic durability. Critical Shared Infrastructure, Montes et al. and invention than prescribing an push, which to bend or break, and which inevitably wrong goldilocks. to respect. Finally, when open-sourcing a problem, a design space leaves room for This document maps a two-dimensional future work to build upon. design space, which is by definition RD DS Fig. 2: One-dimensional reference design (left); multi-dimensional design space (right) Fig. 3: A map of spaceport design considerations. (Montes, et al., 2020). 2 3 The Four Designs defined spaceports as “a facility providing visiting vehicles. Beyond that, spaceports Four designs, defining a two-dimensional carrier and a commercial airport differ in a site for vertical rocket transport to and can get more sophisticated; offering “drive design space, are explored. The differences performance and circumstance but share from the lunar surface and supporting thru” services to visiting vehicles such as between the four designs are essentialized the same essential function, the following services including but not limited to refueling, recharging and maintenance. in the design space plot diagram. All emerge designs do not perform equally but rather refueling, recharging and maintenance.” The impact feature-richness has on design from the same need to mitigate ejecta but are intended to embody the essence of their The most basic spaceport imaginable is and complexity make it the second design exist under distinct circumstances. As such, boundary-defining point in a shared design nothing more than ground armor - a flat space axis. all of the designs are structures that perform space. pad engineered to resist lunar weathering this basic function. Just as an aircraft and the thermal and mechanical loads of we are going feature-rich here The Machine The Works imported in-situ Apollo 12 Surveyor III LM plume center location (155m) The Skinny The Brute y = 0 y = -6m feature-poor we are Figure 3: A polar graph showing the size of particles blown (red dots, to scale) as a function of distance from the here center of the exhaust plume (concentric rings) for a 40 t lander. The dashed line marks the threshold beyond which 126 micron particles cease to be blown. Figure by author after Van Susante & Metzger (2014). Figure 4: The main “sheet” of ejecta (dust, sand, gravel and rocks) traveling upward at an approximately 1-3 degree slope and away from the Apollo 12 LM. Surveyor 3 was located beneath the main sheet so was only damaged by a fraction of the impacts that would have occurred if directly exposed. Figure following Tosh, et al., (2011). 4 5 The Skinny is a lightweight spaceport imported from Earth and deployed on the lunar surface. It performs only the essential function of a spaceport. Architecture CONOPS The Skinny has two zones - a central Delivered to the lunar surface as lander "bullseye" and an outer "apron". The payload, it is hoisted from the lander bullseye, which sit directly under the lander using a crane, which places it on prepared engines, must withstand the thermal and (leveled and flattened) ground. The mechanical loads of the rocket engine deployment sequence begins with the exhaust. This zone is made of metal panels expansion of the outer tube, which tensions that unfold from a stowed configuration the apron. The bullseye is then deployed by into an octagonal platform. The apron panel hinge actuation. A rover may be used borders the bullseye and extends out. It is to secure the apron rim to the ground using made of a heat-resistant textile deployed soil anchors. into shape by an expanding tube filled with gas or an expanding foam. While the The Skinny may alternatively be lowered apron will experience lesser loads than the to the surface by the maiden lander bullseye, the fringes of the engine exhaust while hovering above the altitude that retain enough energy to create ejecta of creates ejecta. This would require an smaller particles sizes (Fig. 3) unconventional engine configuration combined with a wire system to lower payloads. This may eliminate the need for a crane to pick and place the artifact from the payload bay of a lander onto the surface and may enable said vehicle to land on the pad it deploys. 7 The Machine is a feature-rich spaceport imported from Earth and deployed on the lunar surface. It offers visiting vehicles additional services and protection. Architecture CONOPS Featuring subsystems and landing gear, Delivered to the lunar surface as lander The Machine is a spacecraft onto itself. payload, it is hoisted from the lander using It is elevated above the ground on legs, a crane. The legs deploy from their stowed which earns it volume under the deck position prior to placement on an ideal for an exhaust duct. This duct captures or prepared (leveled and flattened) site. the exhaust gases in continuum and Once on the surface, the platforms open transitional flow and redirects them via panel hinge actuation. An existing utility down and laterally away from the vehicle connects power and fuel lines from lander, protecting it. A hatch on the main the base. deck conceals a robotic arm the offers automated refueling and/or recharging for The Machine may alternatively be lowered a visiting vehicle. Since it interfaces directly to the surface by the maiden lander with fuel and power lines, it removes the while hovering above the altitude that need and associated risk for other vehicles creates ejecta.