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→RCS DAP schemes
| Line 197: | Line 197: | ||
; RCS TRANS ATT HLD | ; RCS TRANS ATT HLD | ||
: A translational DAP in which 'attitude hold' is commanded for all rotation channels. This makes this mode very stable and controllable at the expense of an increased propellant consumption - use e.g. for a precision approach to a docking. | : A translational DAP in which 'attitude hold' is commanded for all rotation channels. This makes this mode very stable and controllable at the expense of an increased propellant consumption - use e.g. for a precision approach to a docking. | ||
; RCS TRANS LOW-Z | |||
: To prevent thruster plume impingement on a docking target, say the ISS, in this mode all upward-firing thrusters are inhibited. To provide the deceleration force for a docking (which is needed in -Z direction), foreward and backward firing thrusters are used simultaneously - since they point about 10 degrees upward, this provides a downward acceleration without upward plume at the expense of 12 times higher than normal propellant consumption. There is strong cross-coupling to a pitching motion. | |||
; RCS TRANS LOW-Z ATT HLD | |||
: As in the previous mode, only an attitude hold is commanded in addition. For weak thrust this works well, for strong thrust the controller is, without using upward-pointing thrusters, unable to completely control the pitching motion. | |||