Sextant MFD

Licensed under LGPL v3

Sextant MFD in action

Project home: Sextant MFD at Orbit Hangar Author: Tim 'tblaxland' Blaxland Current version: Unknown Compatibility: Unknown

Sextant MFD is an MFD that simulates a sextant and rendezvous radar for use in semi-optical orbital rendezvous. The intent is to simulate the environment presented to the pilots of Gemini-era spacecraft in the event of a flight computer failure. For more information on the technique refer to the thread on the Orbiter-Forum and Sam Enkidu's tutorial on Orbit-Hangar.

A beta version of the MFD is available on BitBucket.

Operation

Loading

Load the MFD by pressing the MFD "SEL" button and selecting "Sextant".

Information Displayed

The display is broken into three distinct parts.

Reference

The upper section of the display shows reference information including the MFD title, the current reference body (used for determining the local horizon) and the current target.

Sextant

The middle section displays information about the target based on measurements from a virtual sextant.

• Timer - the time starts when the the MRK button is pressed and stops when it is pressed again. The units are minutes and seconds.
• Local hor. angle - the angle between the target and the local horizontal plane.
• In-plane angle - the amount of angular motion of the target in the orbital plane, relative to an inertial frame, since the timer was started.
• Off-plane angle - the amount of angular motion of the target perpendicular to the orbital plane, relative to an inertial frame, since the timer was started.

The units for all angles are decimal degrees.

Rendezvous Radar

The lower section displays information about the target based on measurements from a virtual rendezvous radar.

• Range - Range to the target. Units are metres (m) or feet (').
• Range Rate - Rate of change of the range. A negative value indicates that the range is decreasing. Units are metres/second or feet/second (fps).
• Pitch and Yaw - Position of target relative to the local vessel frame.

Buttons

The function of each of the buttons is described below.

REF

Changes the reference body used for determing the local vertical. The reference body defaults to the major gravitational influence on the vessel when the scenario is started. Pressing this button opens a dialog box allowing the reference body to be selected.

TGT

Changes the target vessel. Pressing this button opens a dialog box allowing the target vessel's name to be entered.

UNT

Switch between metric and imperial units.

MRK

Take a mark on the target, reset the timer to zero and start it counting. Press again to take another mark and halt the timer.

Changing Vessel Focus

When you change vessel focus, the MFD will remember the settings for each vessel and MFD position. This includes sextant mark information, so that a mark may be started, focus switched, and the mark completed after switching back.

Saving/Loading Scenarios

This MFD saves its state to the scenario file so all settings will be restored when restarting the scenario. Also included is saving/restoring the settings for any other vessels that have been used with Sextant MFD in the scenario even though those vessels do not have the focus at the time of scenario being saved.

Configuration

A configuration file (SextantMFD.cfg) in located in OrbiterDirectory\Config\SextantMFD and contains the settings for the MFD. The following items can be configured.

Colours

TEXT_COLOUR - colour for general text items.

POS_COLOUR - colour for positive measurement values.

NEG_COLOUR - colour for negative measurement values.

See the config file for valid colour values.

Defaults

UNITS - the default units. See the config file for valid values.

Limits

SEXTANT_MAX_ANGLE - the maximum angular measurement range of the sextant, in degrees.

RADAR_MAX_RANGE - the maximum range of the radar, in metres.

RADAR_MAX_ANGLE - the maximum angular range of the radar, in degrees.

Credits

This MFD uses the built-in Orbiter pop-up menus for selecting the reference body. Thanks to CJ Plooy for his work in making this functionality available.

Two functions from FreeOrbitMFD by CJ Plooy were used for formatting the SI prefixes. See source code for details.

Copyright Notice

Copyright 2009 by Tim Blaxland (tblaxland@gmail.com)

Sextant MFD is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Sextant MFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with StateVectorMFD. If not, see <http://www.gnu.org/licenses/>.