Methods and apparatus to methods and apparatus for performing propulsion operations using electric propulsion system are disclosed. An example launch vehicle includes a first space vehicle including a first core structure and a first electric propulsion system, and a second space vehicle including a second core structure and a second electric propulsion system, the second core structure releasably attached to the first space vehicle in a stacked configuration.

The present disclosure relates to a maritime communication system based on low earth orbit satellites and an unmanned aerial vehicle. The maritime communication system according to one embodiment may include one or more maritime users, one or more satellites connected to a network operator, and an unmanned aerial vehicle (UAV) for relaying communication between the maritime users and the satellites.

A method for transferring a spacecraft (10), such as an artificial satellite, from an initial elliptical orbit (30) to a final geostationary orbit (50), the spacecraft taking at least one intermediate elliptical orbit (40) propelled by electric propulsion means (12, 13), the method includes: when the spacecraft is in an intermediate orbit, a nominal thrust step (410) in which the propulsion means generate nominal thrust while the spacecraft is on at least part of a first orbital arc (41) passing through the apogee A of the intermediate orbit, and a minimum thrust step (420), in which the propulsion means are partly stopped or slowed while the spacecraft is on at least part (43) of a second orbital arc (42) passing through the perigee P of the intermediate orbit, the two orbital arcs being complementary.

A system for positioning at least one satellite in working orbit, characterized in that the system for positioning satellites in working orbit comprises: a first attachment device configured to attach a first satellite to the system for positioning satellites in working orbit; a main propulsion device with solid propulsion comprising a plurality of parallel solid-propellant cartridges; a secondary propulsion device which is re-ignitable; at least one position sensor configured to measure the position of said system; a monitoring unit connected to said at least one position sensor and which is configured to control a firing of the cartridges of the main propulsion device to move said system from a transfer orbit to a working orbit of the first satellite, said monitoring unit being further configured to control an opening of the first attachment device to separate said system from the first satellite.

A method and system for activating thrusters of a vehicle for trajectory-tracking control of the vehicle. A transfer orbit generator to generate a transfer orbit for the vehicle from an initial orbit to a target orbit, and a feedback stabilization controller. Compute the target orbit for the vehicle about the celestial body. Compute a free trajectory with patch points along the free trajectory using a free trajectory module, each patch point includes a position and a velocity. Determine a feedback gain at each patch point using a feedback gain module, wherein a state penalty function at each patch point is set to match a state uncertainty function at the same patch point. Apply the feedback gain at each patch point to map the position and the velocity at each patch point to delta v commands, to maintain the target orbit using a feedback stabilization controller.

In an orbital attitude control device (1150), an ideal thrust axis direction calculator (1505) calculates an ideal thrust axis direction based on information of a predetermined orbit, an ideal attitude calculator (1506) calculates an ideal attitude of the satellite based on the ideal thrust axis direction and a solar direction, and a control torque calculator (1510) calculates an ideal control torque that makes the attitude of the satellite follow the ideal attitude and a torque restraint plane in which the solar direction is orthogonal to a rotational axis of the solar array panel, defines an evaluation function obtained by weighting a distance from the ideal control torque and a distance from the torque restraint plane and then summing the weighted distances, and calculates the control torque that allows the drive constraint to be satisfied and the evaluation function to be minimized.