A liquid tank system comprises a main liquid tank, an outlet communicating between a fluid circuit and the main liquid tank, an inlet communicating between the fluid circuit and the main liquid tank, and an auxiliary cavity. First vent passage and second vent passage(s) communicate between the main liquid tank and the auxiliary cavity and allows liquid and gas to flow from the main liquid tank to the auxiliary cavity. The second vent passage has a flow control device regulating flow through the second vent passage and having a set point at which it allows liquid and gas to flow from the main liquid tank to the auxiliary cavity only when a pressure in the main liquid tank is beyond a threshold. The liquid tank system has an attitude envelope in which the liquid tank system is configured such that, in use, the flow control device blocks flow through the second vent passage when an end of the first vent passage in the main liquid tank is above a liquid level, and the flow control device allows gas and/or fluid flow through the second vent passage when main fluid tank pressure is above the threshold and the end of the first vent passage in the main liquid tank is below the liquid level.

A liquid tank system comprises a main liquid tank, an outlet communicating between a fluid circuit and the main liquid tank, an inlet communicating between the fluid circuit and the main liquid tank, and an auxiliary cavity. First vent passage and second vent passage(s) communicate between the main liquid tank and the auxiliary cavity and allows liquid and gas to flow from the main liquid tank to the auxiliary cavity. The second vent passage has a flow control device regulating flow through the second vent passage and having a set point at which it allows liquid and gas to flow from the main liquid tank to the auxiliary cavity only when a pressure in the main liquid tank is beyond a threshold. The liquid tank system has an attitude envelope in which the liquid tank system is configured such that, in use, the flow control device blocks flow through the second vent passage when an end of the first vent passage in the main liquid tank is above a liquid level, and the flow control device allows gas and/or fluid flow through the second vent passage when main fluid tank pressure is above the threshold and the end of the first vent passage in the main liquid tank is below the liquid level.

A system and method for the transfer of cryogenic fluid fuel includes a nozzle positionable with respect to fuel tank inlet, e.g., of an unmanned aerial vehicle (UAV), a seal to seal the area where the nozzle and inlet are connected, a collapsible and expandable bellows providing an isolation volume where the fluid is transferred from the nozzle into the inlet; a vacuum is provided in the volume to avoid accumulation of fuel or other species in the volume.

A system and method for the transfer of cryogenic fluid fuel includes a nozzle positionable with respect to fuel tank inlet, e.g., of an unmanned aerial vehicle (UAV), a seal to seal the area where the nozzle and inlet are connected, a collapsible and expandable bellows providing an isolation volume where the fluid is transferred from the nozzle into the inlet; a vacuum is provided in the volume to avoid accumulation of fuel or other species in the volume.

A system comprises a non-transitory machine readable storage medium storing instructions and a database identifying a plurality of assets and a state of each asset. The instructions configure a processor for receiving updates to a distributed electronic ledger managed by plural peer processors. Each update includes an event or change affecting one of the assets. The peer processors verify portions of the ledger describing each event or change. At least one of the updates has not yet been recorded in the ledger at a time of the receiving. The processor computes a state of each asset, based on the updates, receives a request for a state of one of the assets; and responds to the request, reflecting each event and change affecting that asset. The response is performed without waiting for the peer processors to verify an update that has not yet been recorded in the ledger.

A system comprises a non-transitory machine readable storage medium storing instructions and a database identifying a plurality of assets and a state of each asset. The instructions configure a processor for receiving updates to a distributed electronic ledger managed by plural peer processors. Each update includes an event or change affecting one of the assets. The peer processors verify portions of the ledger describing each event or change. At least one of the updates has not yet been recorded in the ledger at a time of the receiving. The processor computes a state of each asset, based on the updates, receives a request for a state of one of the assets; and responds to the request, reflecting each event and change affecting that asset. The response is performed without waiting for the peer processors to verify an update that has not yet been recorded in the ledger.

Fuel systems, apparatus and associated methods for preventing or hindering unwanted fuel transfer between fuel tanks of aircraft are described. An exemplary apparatus comprises a conduit portion disposed inside a fuel tank for receiving fuel in the first fuel tank. The conduit portion includes an orifice through a wall of the conduit. The orifice permits venting an interior of the conduit portion to an interior of the fuel tank to prevent unwanted fuel transfer due to siphoning. A deflector is disposed and configured to deflect a stream of fuel discharged from the orifice during fuel transfer.

A system comprises a non-transitory machine readable storage medium storing instructions and a database identifying a plurality of assets and a state of each asset. The instructions configure a processor for receiving updates to a distributed electronic ledger managed by plural peer processors. Each update includes an event or change affecting one of the assets. The peer processors verify portions of the ledger describing each event or change. At least one of the updates has not yet been recorded in the ledger at a time of the receiving. The processor computes a state of each asset, based on the updates, receives a request for a state of one of the assets; and responds to the request, reflecting each event and change affecting that asset. The response is performed without waiting for the peer processors to verify an update that has not yet been recorded in the ledger.

A metal air battery electrolyte replenishment system comprised of a base station with docking receptor apparatus and matching docking probe on a flying drone. The probe onboard the drone has a sensor that guides the drone to connect with the electrolyte docking receptor on the base station. The drone uses the probe to obtain fresh electrolyte and simultaneously expel spent electrolyte into the base station while still in flight or during a brief landing. Rapid exchange of the electrolyte allows for extended range and flight time without penalty of onboard electrolyte reconditioning system and its associated weight.

Aircraft hydrogen fuel systems and methods and systems of starting such systems are described. The aircraft hydrogen fuel systems include a hydrogen burning main engine, a main tank configured to contain liquid hydrogen to be supplied to the main engine during a normal operation, and a starter tank configured to contain gaseous hydrogen to be used during a startup operation of the main engine. Methods and processes for starting and/or restarting such systems are described.