Abstract: Methods of recirculating clean air in an atmosphere of an enclosure comprise directing an input air stream from the atmosphere of the enclosure through a coiled duct at a rate sufficient to stratify the input air stream within the coiled duct according to a molecular weight of components of the input air stream and to form a heavy fraction stream and a light fraction stream, wherein the heavy fraction stream is relatively enriched in carbon dioxide as compared to the light fraction stream; withdrawing the heavy fraction stream from the coiled duct; and returning the light fraction stream from the coiled duct to the atmosphere of the enclosure.

Abstract: Atmospheric thrust stages, multi-stage launch systems including the same, and related methods. A multi-stage launch system includes a launch vehicle configured to transport a payload to a payload destination. The launch vehicle includes an atmospheric thrust stage (ATS) with a plurality of airbreathing engines configured to provide thrust to the launch vehicle for a vertical launch of the launch vehicle The ATS is configured to be retrieved and reused subsequent to returning to Earth. A method of transporting a payload to a payload destination includes powering a launch vehicle that includes an ATS and a second stage by providing thrust with a plurality of airbreathing engines of the ATS to propel the launch vehicle, decoupling the second stage from the ATS, powering the second stage to transport the payload to the payload destination, and returning the ATS to Earth.

Abstract: Methods of recirculating clean air in an atmosphere of an enclosure comprise directing an input air stream from the atmosphere of the enclosure through a coiled duct at a rate sufficient to stratify the input air stream within the coiled duct according to a molecular weight of components of the input air stream and to form a heavy fraction stream and a light fraction stream, wherein the heavy fraction stream is relatively enriched in carbon dioxide as compared to the light fraction stream; withdrawing the heavy fraction stream from the coiled duct; and returning the light fraction stream from the coiled duct to the atmosphere of the enclosure.

Abstract: Centrifugal air separators, systems including the same, and methods of separating gas are disclosed. Centrifugal air separators include a separation section configured to separate an input air stream into a clean air stream emitted from an exit port of the separation section and a waste stream emitted from a waste port of the separation section. The separation section includes a coiled duct and is configured to transmit through a duct entrance port a duct input air stream that is at least a portion of the input air stream and to at least partially separate the duct input air stream according to a molecular weight of gaseous components of the duct input air stream into a duct clean air stream that is at least a portion of the clean air stream and a duct waste stream that is at least a portion of the waste stream.

Abstract: Centrifugal air separators, systems including the same, and methods of separating gas are disclosed. Centrifugal air separators include a separation section configured to separate an input air stream into a clean air stream emitted from an exit port of the separation section and a waste stream emitted from a waste port of the separation section. The separation section includes a coiled duct and is configured to transmit through a duct entrance port a duct input air stream that is at least a portion of the input air stream and to at least partially separate the duct input air stream according to a molecular weight of gaseous components of the duct input air stream into a duct clean air stream that is at least a portion of the clean air stream and a duct waste stream that is at least a portion of the waste stream.

Abstract: Centrifugal air separators, systems including the same, and methods of separating gas are disclosed. Centrifugal air separators include a separation section configured to separate an input air stream into a clean air stream emitted from an exit port of the separation section and a waste stream emitted from a waste port of the separation section. The separation section includes a coiled duct and is configured to transmit through a duct entrance port a duct input air stream that is at least a portion of the input air stream and to at least partially separate the duct input air stream according to a molecular weight of components of the duct input air stream into a duct clean air stream that is at least a portion of the clean air stream and a duct waste stream that is at least a portion of the waste stream.

Abstract: Centrifugal air separators, systems including the same, and methods of separating gas are disclosed. Centrifugal air separators include a separation section configured to separate an input air stream into a clean air stream emitted from an exit port of the separation section and a waste stream emitted from a waste port of the separation section. The separation section includes a coiled duct and is configured to transmit through a duct entrance port a duct input air stream that is at least a portion of the input air stream and to at least partially separate the duct input air stream according to a molecular weight of components of the duct input air stream into a duct clean air stream that is at least a portion of the clean air stream and a duct waste stream that is at least a portion of the waste stream.