Rendezvous and Docking

Some General Information

Eagle Lander 3D (EL3D) features rendezvous and docking capabilities for the terminal phase, “putting it in the garage”, as Buzz Aldrin describes.  The difference between EL3D and an actual Apollo flight is that the LM remains the active docking platform throughout the procedure.  Normally the LM would chase the CSM and then the Command Module Pilot (CMP) would do the actual docking procedure from the Command Module.  However as a backup the LM was perfectly capable of doing the active docking.  In EL3D you will perform that procedure. 

There are two Orbital scenarios: Orbital Descent, Orbital Ascent.  To actually practice docking from the ascent stage you would select Orbital Ascent.  However, you might find it useful the first time to use the descent scenario just to see the alignment between the two spacecraft. 

An important instrument utilized for docking is called the Crewman Optical Alignment Site (COAS).  This device is mounted in the overhead docking window and projects a docking target on a reticule that the Commander (CDR) looks through.  The optics of the site creates an image projected at a distance away from the LM.  The CDR then maneuvers the LM until the projected image aligns with the docking target mounted on the right forward facing window of the Command Module (CM). 

If you start with the descent scenario you can look through the COAS mounted on the overhead window (Virtual View 2) and see the proper alignment.  You can then press CTRL+D to undock.  As the spacecraft separate you can watch this alignment.  If you like you can make a few minor RCS or translations and then ‘practice’ realigning the target.  Now ease toward the CSM and try to re-dock.

A docking consists of a capture of the probe inside the docking tunnel – sometimes referred to as a ‘soft dock’, followed by the retraction of the probe and the final ‘hard dock’.  In EL3D you will hear the docking probe sliding down the tunnel and then hear the capture.  The retraction of the probe takes several seconds and then you will hear the latches engage and a message “Hard Dock” will appear. 


An Actual Docking

Selecting the Ascent Orbital scenario puts you in the ascent stage of the LM about a mile away and slightly below the CSM.  You are approaching the CSM at about 15 fps.

You can use the Rendezvous Radar (RR) to track the CSM and help you null your relative velocities.

·       The X-Pointer displays relative angle rates from the CSM in mRads/sec (milli-radians per second) for horizontal and vertical alignment. 

·       The Altitude Tape displays range in feet.

·       The Altitude Rate Tape displays range rate in ft/s

·       You can also hit the space bar in any display to show similar information on the bottom info bar.

Glancing at the DSKY you will notice the active program is P20 and the two upper registers have numbers representing the Trunnion Angle (Register 1) and the Shaft Angle (Register 2) of the RR.  Since the RR is automatically tracking the LM you can adjust the orientation of the LM until those values are reading zero.  That means the LM is pointing directly at the CSM.  If you look through the CDR window you should see the CSM way out there (a small dot) near the zero line of the LPD.  By pointing the LM directly at the CSM you can also make translations in plane with the relative velocity corrections necessary shown on the X-Pointer.

Start slowing down using Z translation.  A series of relatively long RCS burns will start to bring your velocity down.

As you get close to the CSM you will need to decide on final alignment translations.  The X-Pointer will show your relative angular velocity from the CSM.  If you are below you might need to use some X translation to bring the LM up a little.  You can then use the X-Pointer to stop the relative movement.

Once you are about 60 feet from the CSM and are holding station it is time to pitch over for the final docking phase.  As you pitch over you should switch your view to Virtual View 2 and begin looking through the reticule for the docking target on the CSM.  You will need to yaw the LM to the correct orientation with the CSM.  You will also notice that the translations and some attitude RCS commands are now 90 degrees different then when you were looking out the front window.  Get used to it! 

Now it is up to you to make final translations and attitude corrections to dock.  You should do the actual docking at about .1fps.

Just like landing it takes some practice!


Other Orbital Flight Information

Try different modes of RCS.  (See Switch Positions). In normal Attitude Hold you can select minimum and maximum Deadband.  This means that the calculated attitude will be held within the Deadband.  At Max Deadband the attitude is held within 5 degrees.  In minimum Deadband it is .5 degrees.  Of course the accuracy is less in Max, but RCS fires less too.

Select Minimum Impulse Mode.  Enter V76E through the DSKY (Learn how to use the computer).  Now every time you move the controller a short burst of 14ms occurs.  This is used for star sightings and very small and precise maneuvers.  To return to normal enter V77E.

You can manually stage the LM.  Hit CTRL+A and the two stages separate and drift apart.  Watch the LM descent stage tumble slowly beneath you. Of course you just blew any chance of landing…..



The DSKY display can be changed by pressing PRO and then entering in V16N78E.  This shows basic velocity information that is similar to what you are already seeing on the tapes / info bar.  Select F2 for more detailed information about P20 DSKY functions.