| ALIGN PLANES & PERIAPSIS |
ALIGN ORBIT!
You are in orbit but still have much to do to meet up with and dock to the space station.
Instructions from this point forward will be geared a bit more towards theory rather than actual
number-by-number procedures. This is because your ascent trajectory may have been quite
different than the authors. Orbiter is a rich and robust sim. No two space flights have ever
been exactly the same in reality and so too in this sim. Not to worry! We will still get you to that
station!
Onward!
==
50 - Ensure that you are in 'cockpit' view and that the sim is not paused.
51 - Click on the 'DST' button of your left MFD. Now that we are in orbit we want to deal with
radius numbers as opposed to altitude numbers.
52 - Click on the 'TGT' button of your left MFD. We will now select a target.
-Arrow key down to 'spacecraft'
-Right arrow
-Use arrows to select 'ISS'
-Hit 'Enter' key
53 - Your left MFD should now reflect orbit data for the ISS in the right hand (yellow) column.
Your orbit is quite different from the orbit of the ISS. We will now systematically alter our orbit
until it matches the orbit of the ISS.
First, we must align our orbital plane with that of the ISS. Huh?
54 - Click on the 'SEL' button under the right MFD. Select 'Align Planes'.
55 - Click on the 'TGT' button. Just like in step 52, Use the arrow keys to select the ISS. Your
right MFD should now look something like this.
Don't be alarmed if it doesn't look exactly like this. Your ascent may have been slightly different
than the author's. You may have taken more time to look around in space at the end of the last
list. It may have taken you more time to taxi to the runway at the beginning of the tutorial. As
mentioned earlier, we will proceed with actions that cover all contingencies.
The graph on the right ('align planes' MFD) shows you the two places where your orbital plane
intersects your target's orbital plane. It is at these two locations that changes must be made to
align the two planes.
57 - Look at this image for a rundown of what the readouts mean:
58 - Burn initiation times must be computed and your ship must be aligned correctly prior to
reaching intersections. Read thru this step and step 59 BEFORE making alignment burn.
BURN TIME
A proper burn will actually straddle the intersection point and therefore needs to be initiated
prior to intersection. Here is how to compute when to start an alignment burn:
SHIP ALIGNMENT
If you are approaching DN or Descending Node, align ship to Orbit Normal
If you are approaching AN or Ascending Node, align ship to Orbit Anti-Normal
You now have what you need to perform your first Alignment burn. You know which direction to
turn your ship and when to fire the main engines. Usually it takes two, sometimes three burns to
bring RInc down under 1 degree.
Now would be a good time to discuss Linear Thrusters as they will come in handy for fine tuning
your orbital burns.
59 - Here is where time acceleration comes in handy. It may be a long time to the next planar
intersection. Instead of twiddling your thumbs, you may want to use the 't' key to accelerate
time. Remember that you are in orbit and that means you don't want to accelerate time beyond
100x. It is also a must to turn off all engines and thrusters prior to time acceleration. Failure to
do so could put you into an unrecoverable spin. This will ruin your day.
SAVE FIRST! Until you get the hang of it, I can guarantee that you will make mistakes during
time acceleration. Save your scene first or suffer the consequences. A quick save 'control' + 's'
will work fine.
Be sure to return to time normal far enough ahead of your burn time so that you can align your
ship and/or make other preparations.
NOTE: A burn to reduce a 40 degree difference will take approx 400 seconds. Thats 6.6
minutes. Hang with it and monitor RInc. If you get close to zero and RInc starts to go up, kill
engines immediately! Wait for the next intersection to finish the alignment.
60 - Using what you just learnd about orbital alignment in steps 57 thru 59, perform as many
burns as necessary to get RInc as close to zero as possible. Your orbit is stable and there
are no time constraints so take your time.
This is what the 'Align Planes' MFD should look like when the orbital planes are aligned.
NOTE: The 'Align Planes' MFD has a feature that informs you when to start your burn. It is still
a good idea to compute this info so you can anticipate and be ready with proper ship alignment.
==
ALIGN PERIAPSIS OF BOTH ORBITS
These steps don't appear in many procedure checklists. However, for this author it means the
difference between success and failure in rendezvous. It may take a bit of extra time but its
benefits in stabilizing the procedure are well worth it.
First let's go over Periapsis and Apoapsis. On your left MFD click on 'MOD' until you see this
Periapsis (PeR) is the lowest point on an orbit. It is represented graphically in the MFD as a
CLOSED dot on the orbit.
Apoapsis (ApR) is the highest point on an orbit. It is represented graphically in the MFD as an
OPEN dot on the orbit.
Orbits can be rotated so that the location of either Periapsis or Apoapsis can be moved. We
want to align our Periapsis with the Periapsis of our target the ISS.
60.5 - Click 'MOD' on your left MFD until the graph AND data appear together on the graph.
Click on 'PROJ' until 'SHP' appears in the upper right of the MFD.
61 - Change the right MFD to 'orbit' but do not select ISS as the target. The left MFD is loaded
down with a lot of info and sometimes the graph is hard to read. By setting the right MFD to
'orbit' you can reference them both and sort out what's going on.
62- Determine where your Periapsis is located. Determine where your target's periapsis is
located.
63 - When your position reaches halfway between your Apoapsis and Periapsis (This can be an
approximate measurement. Just eyeball it.), turn your ship prograde.
64 - Set RCS to Linear using keyboard keys 'num pad' + '/' .
64.5 - Use either the 'num pad 6' or 'num pad 9' key to perform thruster burns to rotate your
Periapsis towards your target's periapsis. If your Periapsis moves the wrong way, switch quickly
to the other key.
Note: Don't burn for more than a few seconds. If the Periapsis' did not line up, re-figure the
next halfway point and do another burn.
65 - Repeat steps 62-64.5 as needed to get your periapsis aligned as close as possible to your
target's Periapsis. If your Periapsis' are far apart, it may take several burns to align them.
When aligned it should look like this.
Just so you know
==
Now we must match the altitudes of both Periapsis.
66 - In the 'Orbit' MFD reference the ISS's PeR or Periapsis. Jot this number down. Read
steps 67 & 67.5 before performing a burn.
NOTE: To raise/lower your Periapsis you must burn at your Apoapsis and vice versa.
These are the best places to make burns that won't disrupt your orbit.
67 - Monitor your ApT value. This is the time, in seconds, to reach Apoapsis. Conversely, PeT
is a value for the number of seconds until you reach your Periapsis. For what we are doing
now, you need to monitor your ApT as it counts down.
If your periapsis is lower than the ISS's you will need to perform a prograde burn at your
Apoapsis.
If your periapsis is higher than the ISS's you will need to perform a retrograde burn at your
Apoapsis.
67.5 - Perform a burn that straddles your Apoasis to raise/lower your periapsis to match the
ISS's periapsis that you wrote down in step 66.
Use linear thrusters to fine tune the burn.
Sometimes this will take more than one attempt. If they didn't match up, go around another orbit
and try again. Don't worry, you've got the time!
IMPORTANT NOTE: All remaining burns (except for docking) need to happen as close as
possible to Apoapsis or Periapsis. Burning anywhere else will tend to undo the Periapsis
alignment we just made!
ANOTHER IMPORTANT NOTE: Ideally, all burns will STRADDLE either Periapsis or Apoapsis.
Meaning if a burn is estimated to take 10 seconds, then initiate the burn 5 seconds prior to
reaching Apoapsis or Periapsis. Burn duration isn't always computed for you. You'll just have
to make your best guess and learn from the results. Save first and try again.
YET ANOTHER IMPORTANT NOTE: If something goes wrong with the burn (ie, burn time was
estimated wrong, pointing prograde instead of retro, etc.) it will be best to cut your losses and
go around for another try. Continuing to burn way after your burn point because of an error is
going to throw your orbit out of whack. You will dis-align your periapsis and in extreme
situations you can accidentally de-orbit. Better to grumble to yourself for another orbit than
burn up in re-entry!
68 - Matching your PeR value to the ISS's may have dis-aligned the two periapsis. A small
variance is OK but if they are quite a ways apart, go back to steps 61-65 to line them up again.
This, in turn, may change your PeR so it doesn't match the ISS's. If so, go back to steps 66 &
67. Keep at it! Eventually they will settle down.
BEFORE MOVING ON: Ensure your Periapsis is the same as the ISS's. This means that:
A. The PeR values for both orbits are the same.
B. Visually the filled dots of both orbits are on top of each other.
If not, go back to step 61 and work them some more.
You are in orbit but still have much to do to meet up with and dock to the space station.
Instructions from this point forward will be geared a bit more towards theory rather than actual
number-by-number procedures. This is because your ascent trajectory may have been quite
different than the authors. Orbiter is a rich and robust sim. No two space flights have ever
been exactly the same in reality and so too in this sim. Not to worry! We will still get you to that
station!
Onward!
==
50 - Ensure that you are in 'cockpit' view and that the sim is not paused.
51 - Click on the 'DST' button of your left MFD. Now that we are in orbit we want to deal with
radius numbers as opposed to altitude numbers.
52 - Click on the 'TGT' button of your left MFD. We will now select a target.
-Arrow key down to 'spacecraft'
-Right arrow
-Use arrows to select 'ISS'
-Hit 'Enter' key
53 - Your left MFD should now reflect orbit data for the ISS in the right hand (yellow) column.
Your orbit is quite different from the orbit of the ISS. We will now systematically alter our orbit
until it matches the orbit of the ISS.
First, we must align our orbital plane with that of the ISS. Huh?
54 - Click on the 'SEL' button under the right MFD. Select 'Align Planes'.
55 - Click on the 'TGT' button. Just like in step 52, Use the arrow keys to select the ISS. Your
right MFD should now look something like this.
Don't be alarmed if it doesn't look exactly like this. Your ascent may have been slightly different
than the author's. You may have taken more time to look around in space at the end of the last
list. It may have taken you more time to taxi to the runway at the beginning of the tutorial. As
mentioned earlier, we will proceed with actions that cover all contingencies.
The graph on the right ('align planes' MFD) shows you the two places where your orbital plane
intersects your target's orbital plane. It is at these two locations that changes must be made to
align the two planes.
57 - Look at this image for a rundown of what the readouts mean:
58 - Burn initiation times must be computed and your ship must be aligned correctly prior to
reaching intersections. Read thru this step and step 59 BEFORE making alignment burn.
BURN TIME
A proper burn will actually straddle the intersection point and therefore needs to be initiated
prior to intersection. Here is how to compute when to start an alignment burn:
SHIP ALIGNMENT
If you are approaching DN or Descending Node, align ship to Orbit Normal
If you are approaching AN or Ascending Node, align ship to Orbit Anti-Normal
You now have what you need to perform your first Alignment burn. You know which direction to
turn your ship and when to fire the main engines. Usually it takes two, sometimes three burns to
bring RInc down under 1 degree.
Now would be a good time to discuss Linear Thrusters as they will come in handy for fine tuning
your orbital burns.
59 - Here is where time acceleration comes in handy. It may be a long time to the next planar
intersection. Instead of twiddling your thumbs, you may want to use the 't' key to accelerate
time. Remember that you are in orbit and that means you don't want to accelerate time beyond
100x. It is also a must to turn off all engines and thrusters prior to time acceleration. Failure to
do so could put you into an unrecoverable spin. This will ruin your day.
SAVE FIRST! Until you get the hang of it, I can guarantee that you will make mistakes during
time acceleration. Save your scene first or suffer the consequences. A quick save 'control' + 's'
will work fine.
Be sure to return to time normal far enough ahead of your burn time so that you can align your
ship and/or make other preparations.
NOTE: A burn to reduce a 40 degree difference will take approx 400 seconds. Thats 6.6
minutes. Hang with it and monitor RInc. If you get close to zero and RInc starts to go up, kill
engines immediately! Wait for the next intersection to finish the alignment.
60 - Using what you just learnd about orbital alignment in steps 57 thru 59, perform as many
burns as necessary to get RInc as close to zero as possible. Your orbit is stable and there
are no time constraints so take your time.
This is what the 'Align Planes' MFD should look like when the orbital planes are aligned.
NOTE: The 'Align Planes' MFD has a feature that informs you when to start your burn. It is still
a good idea to compute this info so you can anticipate and be ready with proper ship alignment.
==
ALIGN PERIAPSIS OF BOTH ORBITS
These steps don't appear in many procedure checklists. However, for this author it means the
difference between success and failure in rendezvous. It may take a bit of extra time but its
benefits in stabilizing the procedure are well worth it.
First let's go over Periapsis and Apoapsis. On your left MFD click on 'MOD' until you see this
Periapsis (PeR) is the lowest point on an orbit. It is represented graphically in the MFD as a
CLOSED dot on the orbit.
Apoapsis (ApR) is the highest point on an orbit. It is represented graphically in the MFD as an
OPEN dot on the orbit.
Orbits can be rotated so that the location of either Periapsis or Apoapsis can be moved. We
want to align our Periapsis with the Periapsis of our target the ISS.
60.5 - Click 'MOD' on your left MFD until the graph AND data appear together on the graph.
Click on 'PROJ' until 'SHP' appears in the upper right of the MFD.
61 - Change the right MFD to 'orbit' but do not select ISS as the target. The left MFD is loaded
down with a lot of info and sometimes the graph is hard to read. By setting the right MFD to
'orbit' you can reference them both and sort out what's going on.
62- Determine where your Periapsis is located. Determine where your target's periapsis is
located.
63 - When your position reaches halfway between your Apoapsis and Periapsis (This can be an
approximate measurement. Just eyeball it.), turn your ship prograde.
64 - Set RCS to Linear using keyboard keys 'num pad' + '/' .
64.5 - Use either the 'num pad 6' or 'num pad 9' key to perform thruster burns to rotate your
Periapsis towards your target's periapsis. If your Periapsis moves the wrong way, switch quickly
to the other key.
Note: Don't burn for more than a few seconds. If the Periapsis' did not line up, re-figure the
next halfway point and do another burn.
65 - Repeat steps 62-64.5 as needed to get your periapsis aligned as close as possible to your
target's Periapsis. If your Periapsis' are far apart, it may take several burns to align them.
When aligned it should look like this.
Just so you know
==
Now we must match the altitudes of both Periapsis.
66 - In the 'Orbit' MFD reference the ISS's PeR or Periapsis. Jot this number down. Read
steps 67 & 67.5 before performing a burn.
NOTE: To raise/lower your Periapsis you must burn at your Apoapsis and vice versa.
These are the best places to make burns that won't disrupt your orbit.
67 - Monitor your ApT value. This is the time, in seconds, to reach Apoapsis. Conversely, PeT
is a value for the number of seconds until you reach your Periapsis. For what we are doing
now, you need to monitor your ApT as it counts down.
If your periapsis is lower than the ISS's you will need to perform a prograde burn at your
Apoapsis.
If your periapsis is higher than the ISS's you will need to perform a retrograde burn at your
Apoapsis.
67.5 - Perform a burn that straddles your Apoasis to raise/lower your periapsis to match the
ISS's periapsis that you wrote down in step 66.
Use linear thrusters to fine tune the burn.
Sometimes this will take more than one attempt. If they didn't match up, go around another orbit
and try again. Don't worry, you've got the time!
IMPORTANT NOTE: All remaining burns (except for docking) need to happen as close as
possible to Apoapsis or Periapsis. Burning anywhere else will tend to undo the Periapsis
alignment we just made!
ANOTHER IMPORTANT NOTE: Ideally, all burns will STRADDLE either Periapsis or Apoapsis.
Meaning if a burn is estimated to take 10 seconds, then initiate the burn 5 seconds prior to
reaching Apoapsis or Periapsis. Burn duration isn't always computed for you. You'll just have
to make your best guess and learn from the results. Save first and try again.
YET ANOTHER IMPORTANT NOTE: If something goes wrong with the burn (ie, burn time was
estimated wrong, pointing prograde instead of retro, etc.) it will be best to cut your losses and
go around for another try. Continuing to burn way after your burn point because of an error is
going to throw your orbit out of whack. You will dis-align your periapsis and in extreme
situations you can accidentally de-orbit. Better to grumble to yourself for another orbit than
burn up in re-entry!
68 - Matching your PeR value to the ISS's may have dis-aligned the two periapsis. A small
variance is OK but if they are quite a ways apart, go back to steps 61-65 to line them up again.
This, in turn, may change your PeR so it doesn't match the ISS's. If so, go back to steps 66 &
67. Keep at it! Eventually they will settle down.
BEFORE MOVING ON: Ensure your Periapsis is the same as the ISS's. This means that:
A. The PeR values for both orbits are the same.
B. Visually the filled dots of both orbits are on top of each other.
If not, go back to step 61 and work them some more.
