The problem of space debris proliferation is one that by most estimates will get worse at an increasing rate. Private launch companies are decreasing the cost to launch for private organizations and governments. This is lowering the barrier to launch satellites (including microsatellites) into orbit (especially those satellites belonging to new satellite-based internet providers). Each launch increases the number of distinct objects in space and therefore adds to the space debris problem because, according to the ESA, the current end of life mitigation compliance is much less than 100%.

Some models, such as those of the ESA, predict that even if launches were to halt, the number of orbital collisions would still increase over time, eventually and inevitably leading to Kessler Syndrome. Since our current and future prospects at space-based science, communications, exploration, and potential settlement depends on the ability to safely achieve orbit, it is clear that steps must be taken immediately to actively reduce the amount of space debris in orbit.

Project Amoeba describes a space station architecture that follows many of the recommendations set forth in the paper ORDER: Space Station for Orbital Debris Recycling (albeit a scaled-up version), in addition to adding a few novel features that could benefit the mission and the people working aboard. The name Amoeba is a metaphor for the station, as the station can be seen as a singular, contiguous-membraned entity that maneuvers through space and swallows up nutrients and subsequently digests them.

Propulsion

A space station that swallows up debris needs to be able to chase after the debris; that is to say, modify it's orbit such that it can rendezvous with the target debris. Such a space station needs much more propulsive capability than the ISS as the orbital maneuvers of a roving station are more frequent and of a greater magnitude than one that merely keeps its altitude. This means that the station requires its own dedicated propulsion system(s) (in contrast to the ISS). I add the plural to "system" as there are benefits to employing multiple types of propulsion.

A space station of this sort would likely need propulsion for three different purposes: orientation modification, orbit modification, and evasive maneuvers. While there could be some overlap between these purposes, they can generally correspond to three different types of propulsion: thrusters, high-efficiency engine(s), and high-thrust engine(s). Project Amoeba employs at least (2) of these categories to fulfill the required purposes.

Thrusters

In this context, thrusters — whether hypergolic or hot/cold air — are generally used for modifying the orientation of a spacecraft (with the exception of thrusters such as the SpaceX Super Dracos). These adjustments are made to one or more of the pitch, yaw, and roll of the spacecraft. They are not meant to substantially change the velocity or the orbit of the spacecraft, but rather to position the spacecraft for further maneuvers or to acutely change the velocity and orientation when performing a rendezvous.

Thrusters of some description are a necessary component of any crewed spacecraft, especially one that needs to perform rendezvous maneuvers. As such, they are included in this station design.

High-Efficiency Engines

This category represents electric propulsion in general, wherein small amounts of propellant are ejected at extremely high velocities via electromagnetic acceleration. As this form of propulsion can function with a comparatively low mass of propellant and with photovoltaics can be powered by the sun, this type of propulsion is commonly used on satellites to maintain orbit or for un-crewed exploratory missions operating over many years. In recent years, advances in hall-effect technology has increased the maximum achievable thrust to the point where it is now feasible for interplanetary human space flight.

For long-duration crewed missions in Earth's orbit with the need to constantly perform orbital transfers in order to rendezvous with space debris, this sort of propulsion would definitely be advantageous. Due to the nature of the mission and the relatively few annual captures needed, a single maneuver can last as long as a month without negatively impacting the mission.

Since this station will effectively act as a nomad — "stopping" briefly to capture objects and rendezvous with other spacecraft — it will need a way to efficiently travel from one orbit to another orbit. The high-efficiency of electric propulsion seems ideal for this need and is therefore included in this design.

High-Thrust Engines

This category is largely represented by chemical engines using a propellant and an oxidizer. This type of engine is usually used to escape from Earth's gravity well, to achieve a stable orbit around Earth, or to escape Earth's orbit. These chemical engines are the best choice when maximum thrust is needed, but they have drawbacks in mass-efficiency, throttling, and longevity. Chemical engines are not as mass-efficient as electric propulsion because the propellant they use is ejected at much lower speeds. They are also less able to throttle up or down than the other types of propulsion listed here. Lastly, since either the propellant or oxidizer are liquid and volatile they will evaporate over time, thus reducing their longevity.

SpaceX's Super Draco thrusters would also fit into this category; though they are hypergolic, they stand out from other orientation/rendezvous thrusters in that they are designed to apply an appreciable force to a spacecraft such that the velocity is changed relatively quickly.

In the event that the station must perform an evasive maneuver (to evade space debris, for instance), it would be helpful to have an engine that can quickly change the velocity of the station. Since neither orientation thrusters nor electric engines can fill this need to great satisfaction, a high-thrust engine would be beneficial. As such an engine would need to be responsive and reliable, a hypergolic system such as an array of Super Dracos would be ideal for this purpose.

Program of Modules

The station is separated into two basic programmatic hubs: the human-oriented area and the mission-oriented area. Each of these areas has an anchor module from which the secondary modules are connected (up to eight modules per anchor). These anchor modules are oriented perpendicularly to both the station's axis of travel and also to the other anchor module. These anchor modules are oriented perpendicularly to each other because the hexagonal profile of the anchor modules allows for the secondary modules to be angled at 60 degrees off of the long axis of the anchor module; more approach space and clearance can be afforded to docking vehicles and modules by rotating one of the anchor modules 90 degrees about the station's axis of travel. In addition, since each anchor module should be outfitted with a window system at each end, more view coverage is gained by rotating one of the anchor modules 90 degrees with respect to the other. This would benefit docking procedures, maintenance procedures, EVA Safety, as well as the human experience.

Hangar

Airlock

Once the debris is dismantled into manageable pieces or fodder, it is transferred into one of a few "bins" that make up the airlock transfer system between the Hangar and the Workroom (since the Hangar is not pressurized, the fodder needs to come to station pressure). When the automated disassemblers (robots) have filled a bin with fodder, the Hangar side hatch is closed, the bin is pressurized, and then the Workroom-side hatch is opened by the crew. There are multiple bins so as to not interrupt the workflow on either side and to allow the turnover to be flexible; the crew can work quickly in sprints while the robots are working nonstop and it is unlikely that the crew and the robots would be working at the same pace, so some room for spillover is recommended.

This module would also have an EVA airlock for the crew to make any needed repairs to the exterior station surface or equipment.

Workroom

The Workroom is the anchor module for mission-related activities and spaces. All mission-related spaces that are accessible to the crew are adjacent to the Workroom module. In addition to the Airlock, the Workroom module is connected to the General Operations, Forge, and Special Ops modules. There is also space for an additional future expansion module and a transient cargo spacecraft.

The Workroom is used for many purposes that relate to the mission. Generous workbenches are outfitted with any and all needed storage, analytical and manipulative tools, attachment points, and data/power hookups. Temporary storage space (in the form of bins with attachment points) is allocated for interim storage/staging of any new material or feedstock before it is loaded, stored, or used in other processes. Long-term storage space is allocated for more-permanent storage of materials or tools/equipment that is only needed intermittently, which should be an automated storage management system to make efficient use of the space. A laboratory will consist of one or more contained cabinet environments for controlled testing of materials which will also contain among other things precise tools designed for use in null-G. Any additive manufacturing machines will be here and will accept feedstock from the dismantling process.

At each end of the Workroom is an exterior window system for EVA/ATV/Robot Arm/rendezvous monitoring as well as space/Earth viewing.

Forge

The Forge is an important part of the processing of the debris material and is connected directly to the Workroom module. The main purpose of the Forge is to melt the fodder into a processable molten mass. This is accomplished through a large, electronic induction forge system (IFS). The module is outfitted with the needed analytical tools, process information management system, power management system, heat radiation system, material cooling system, and any other secondary systems.

In null-G, the induction coils of the IFS should have an interesting affect on the metal fodder; by creatively wrapping the induction coils along the process tube, the fodder can be suspended in the center of the tube magnetically and should form a perfect molten sphere when melted. By modifying the power in the coil system, the molten sphere can be transported without physical contact. When melting is complete, the molten sphere can then be further processed/cooled into whatever form is needed and desired.

Special Ops

The primary focus of the Special Ops module is the capture of or otherwise interaction with target debris. This is where crew can monitor and command any and all deployed ATVs or drones (and by extension their onboard ADR systems) as well as operate the Robotic Arm. The exterior of this module is where the ATV and drones would be berthed and supplied with power/data/fuel. Any diagnostics, updates, or monitoring that would need to be performed on the ATVs or drones would be performed here. The control portion would consist of a workstation with ample controls and monitors for one or more crew to use during special operations. This same station would be used for the control of the Robotic Arm system.

Operations

This module is the control hub, the communications center, and the central organization and planning center of the station. This is where the crew will monitor the onboard systems: from the status of the power generation and radiation apparatus, the temperature of the Forge, the state of the {robots}, the environmental control settings, the battery levels, etc.

Located between the Wardroom and the Workroom, this module is the programmatic center of the station. As such, it should also act as a transition space between the human-focused part of the station and the mission-focused part of the station.

Structural Truss

Structural scaffolding built around the operations module will support the Solar/Radiator Array and the Robotic Arm, as well as any non-occupiable equipment needed in the future.

Solar Array

This component is not habitable, but its important features and worth speaking about. The goal is for the Solar Array to generate enough power to simultaneously feed the electric engines, the Forge, Hygiene - Life Support systems, and Operations systems, as well as a certain margin more so this energy can be stored in efficient batteries for use while the Earth is between the station and the sun. The design allows for the array to be rotated with respect to the station for more efficient solar insolation.

Radiator Array

In order to dissipate the heat generated by the station, the underside of the Solar Array will be fitted with a Radiator Array. The Radiator Array is located in this position so that the solar array can block the sun from contacting the radiating surfaces. When the Solar Array moves to be more-perpendicular to the sun, the radiator benefits from this by moving out of the incident sun as well.

Robotic Arm

The Robotic Arm is mounted to the operations module, as the central location allows the arm to reach the most places. This arm will be outfitted with both a clamp end and an electromagnet. The uses of the Robotic Arm are varied and include intercepting approaching spacecraft, capturing docile debris, and relocating modules/components.

Wardroom

The Wardroom is the anchor module for human-focused activities and spaces. All human-focused spaces are in and adjacent to the Wardroom module. The Wardroom module is connected to the Operations module, the Crew Quarters module, the Hygiene - Life Support module, and the Mechanical module. This is also where crewed vessels will dock/depart when receiving and sending off crew.

Crew Quarters

The crew quarters are where the crew sleeps and changes, as well as where a significant portion of the crew-sustaining supplies are stored. By combining the quarters with the storage function, the quarters are able to be kept separate from the rest of the crew area while the wardroom is kept relatively free of storage containers. Having the crew quarters in a separate area from the rest of the station adds to the ability for the crew to get sound sleep, which has been a common complaint by the crew members of previous space stations, especially since the work/sleep schedule is often not as predictable or consistent as on Earth.

Hygiene / Life Support

As far as the crew is concerned, the Hygiene - Life Support module is used for the purposes of personal hygiene, cleaning, and restroom facilities. The Hygiene - Life Support module also hosts the litany of systems that recycle water and air, dispose of waste, and manage the temperature of the station.

Mechanical

This module is a catchall module that will host any and all support systems that do not otherwise have a space allocated. This includes energy storage, fuel storage, and any needed engine system components, as this module is located at the stern of the station.

Process Images