Spacecraft to Remove Orbital Debris
An approach to mitigating the creation of additional orbital debris is to remove the sources of future medium debris by actively removing large spent objects from congested orbits. NASA has introduced the ADRV, an efficient and effective solution to remove large debris from LEO such as spent rocket bodies and non-functional satellites. The concept yields a single use, low-cost, lightweight, high mass fraction vehicle that enables the specific removal of large orbital debris (1000 - 4000 kg mass, 200 - 2000 km altitude, and 20 98-degree inclination). The ADRV performs rendezvous, approach, and capture of non-cooperative tumbling debris objects, maneuvering of the mated vehicle, and controlled, targeted reposition or deorbit of the mated vehicle. Due to its small form factor, up to eight ADRVs can be launched in a single payload, enabling high impact orbital debris removal missions within the same inclination group. Three key technologies were developed to enable the ADRV: - 1) The spacecraft control system (SCS) is a guidance, navigation, and control system that provides vehicle control during all phases of a mission; - (2) The debris object characterization system (DOCS) characterizes movement and capture of non-cooperative targets; and - (3) The capture and release system (CARS) allows the vehicle to capture and mate with orbital debris targets. These technologies can improve the current state-of-the-art capabilities of automated rendezvous and docking technology significantly for debris objects with tumbling rates up to 25 degrees per second. This approach leverages decades of spaceflight experience while automating key mission areas to reduce cost and improve the likelihood of success.
Air Revitalization for Vacuum Environments
The NASA life support system uses a regenerable vacuum swing adsorption process, known as Sorbent-Based Air Revitalization (SBAR), to separate water and carbon dioxide for disposal. The SBAR system is an adsorbent-based swing bed system that has been optimized to provide both humidity and carbon dioxide control for a spacecraft cabin atmosphere. The system comprises composite silica gel and zeolite-packed beds for adsorption and a bypass system for flow control. Under normal operating conditions, the disposal system would require a high-quality vacuum environment to operate. Improvements to the SBAR system include an enhanced inherent capacitance that extends the operation time within a non-vacuum environment for up to 4.5 hours. Flight time can be further expanded with multiple SBAR systems to allow for system regeneration. By scheduling periodic thermal regenerations&#151nominally during sleep periods&#151the SBAR technology may be suitable for missions of unlimited duration.
mechanical and fluid systems
Spacecraft Atmosphere Carbon Dioxide (CO<sub>2</sub>) Capture via Deposition
Spacecraft Atmosphere Carbon Dioxide (CO<sub>2</sub>) Capture via Deposition is an air revitalization architecture that utilizes the different physical phase-change properties of International Space Station (ISS) cabin-like constituents (nitrogen, oxygen, carbon dioxide, water vapor, and various trace contaminants) to selectively separate constituents of interest, such as carbon dioxide and trace contaminants. As the main target constituent is CO<sub>2</sub>, which does not condense in atmospheric conditions, this architecture is referred to as CO<sub>2</sub> deposition, or CDep. The technology addresses future CO<sub>2</sub> removal and life support system needs using a completely different technical approach than currently employed on the ISS. Instead of using a sorbent, this technology utilizes cooling to directly freeze CO<sub>2</sub> out of the atmosphere. Specifically, it involves forcing a phase change of CO<sub>2</sub> from the cabin atmosphere by solidifying it onto a cold surface. The technology for spacecraft atmosphere CO<sub>2</sub> capture uses sequential heat exchangers to cool airflow from the spacecraft atmosphere, and uses deposition coolers that can operate in a deposition mode, in which CO<sub>2</sub> from the airflow is deposited to generate said CO<sub>2</sub> depleted air, and a sublimation mode in which deposited CO<sub>2</sub> is sublimated into CO<sub>2</sub> gas. The system can alternately cycle between the deposition mode and the sublimation mode. A deposition system can also remove humidity in addition to CO<sub>2</sub> via a multi-stage process, and can also significantly assist in controlling the trace contaminants.
mechanical and fluid systems
ISS as seen by STS-124; Photo Credit: NASA on the Commons,
Liquid Sorbent Carbon Dioxide Removal System
NASA's Liquid Sorbent Carbon Dioxide Removal System was designed as an alternative to the current CO2 removal technology used on the International Space Station (ISS), which uses solid zeolite media that is prone to dusting, has a low absorption capacity, and requires high regeneration temperatures and frequent maintenance. Motivated by CO2 removal systems on submarines, NASA innovators began investigating the use of liquid sorbents. Liquid sorbents have a capacity four times greater than solid zeolites, require low regeneration temperature, and need fewer unreliable moving mechanical parts than solid based systems. While submarine CO2 scrubbers spray an adsorbing chemical directly into the air stream and allow the liquid to settle, NASA's new system uses a capillary driven 3D printed microchannel direct air/liquid contactor in a closed loop system. The Liquid Sorbent Carbon Dioxide Removal System is robust and reliable, while being low in weight, volume, and power requirements. The system is capable of reaching equilibrium when the liquid sorbent surface is being regenerated at a rate equal to the rate of absorption into the liquid.
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