aligning orbits whit the iss in the mission sts-123

[Vipers]

Hi, I need help whit mission StS-123 i read more tutorial but this mission is difficult.

Someone can list to me all passages necessary to aligning orbits whit the iss in the mission sts-123


After get the Earth Orbit my situstion is like that in the photo

 

[ar81]

You should take off when ISS orbit is almost above you. Earth rotates, so it should happen twice every 24 hours.

If you use Align MFD, Tn (time to node) should be less than 8 minutes (480 sec). Unfortunately I can't tell you an exact number, for my experience with STS is limited.
You should launch with the proper azimuth so your trajectory is aligned with station.

STS does not have enough fuel for the very fuel consuming orbit align maneuver, so you take off and you are already aligned upon reaching orbit.

 

[rocketman768]

Hi, I need help whit mission StS-123 i read more tutorial but this mission is difficult.

Someone can list to me all passages necessary to aligning orbits whit the iss in the mission sts-123


After get the Earth Orbit my situstion is like that in the photo

Since your relative inclination (RInc) in the align MFD is only 0.35 degrees, it looks like you did a pretty good job of getting into orbit. Since your plane of orbit doesn't have the exact same inclination (tilt) as the ISS' plane, your ship will cross the ISS' plane twice every orbit. These places are called nodes. On one node, you are ascending upward through the plane when you cross it, and the other time you are descending through it. These are called "ascending node" and "descending node" respectively, and they are labelled "AN" and "DN" on your align plane MFD.

You have to thrust in either the "normal" or "antinormal" attitudes at the nodes to make your RInc go to zero. At the AN, you must thrust antinormal, and at the DN, you must thrust normal (you can use the autopilot to put you in these attitudes). Both of these attitudes place your ship's nose-tail axis perpendicular to the plane of your orbit. If you're in prograde autopilot, "normal" will be 90 degrees up and "antinormal" will be 90 degrees down. So, now you should understand why you have to thrust antinormal at the AN. If you do so, you would be pushing your prograde velocity vector down to be in-plane with the ISS.

Notice that your "TthA" (or time of required thrust at the AN) says 84.36 seconds, and your "Tn" (or time until next node) says 628.1 seconds. This means that you will be at the AN in that amount of time. However, since you can't apply all that thrust EXACTLY when you reach the AN, you have to pretend you cross the AN at the middle of your burn so that the burn is centered on the AN. To do this, orient yourself antinormal and wait until the Tn reads exactly half the burn time (in this case 42.18), and hold full thrust. Now watch the "Rate" line which tells your how fast you are closing in on the other plane. Stop burning when it switches from negative to positive. You should now be within 0.01 degrees of the ISS' plane of orbit.

 

[rocketman768]

Now that you are in the same plane, it's time to let the ISS catch up with you since you are ahead of it according to Orbit MFD.

Well, I take it back...first circularize your orbit by burning prograde when the ApT gets close to zero. Burn until your Ecc gets as close to zero as it's going to get.

Now, we want to rotate your perigee point to match that of the ISS so that we can more accurately control your approach to the ISS. In Orbit MFD, your perigee point is denoted by a filled-in green circle and the apogee is denoted by an empty green circle. When your ship is halfway between the two, burn a tiny amount in the prograde direction until your perigee point is right under the ISS' perigee point. The amount of thrust required will be small if you are in a very circular orbit, so you can switch the RCS thrusters to linear mode by pressing / and then pressing numpad 6 for thrust.

Now you will thrust prograde at perigee to raise your apogee to match that of the ISS. Just like before, try to time your burn so that half the thrust comes before and after the perigee so that you don't rotate the perigee/apogee points. Do the same thing at apogee to raise your perigee. You can use the linear thrusters again to fine tune.

Alright NOW it's time to let the ISS catch up to you. If you did a good job with matching the apogee/perigee points. You should notice that your "T" (or time to complete a full orbit) line reads the exact same as the ISS' at 5,476 seconds. This means it will never catch up to you. So, next time you come up on perigee, burn until your T is 20-40 seconds more than the ISS'. Since your "T" or orbital period is longer, the ISS will gain 20-40 seconds of orbit time every orbit on you.

Switch the MFD to Sync MFD, press "TGT" and enter "ISS", and press its "MOD" button until it says "Ref: Sh periapsis". Now disengage all autopilots and crank up the time to 1000x. Watch carefully until "DTmin" (the minimum difference between the time when the ship crosses the reference point and when the ISS crosses the reference point) is less than 20-40 seconds and put the time at 1x. Now, the highlighted yellow line indicates on which orbit you will come close to the ISS. Turn on the prograde autopilot and wait until perigee, and use the linear thrusters (numpad 6 or numpad 9) to thrust forward or aft and reduce the DTmin to zero seconds. This means that you and the ISS will get to the same point at the same time. Now you just have to wait how many orbits are indicated by the highlighted line (0: or 1: or 2: ...) until you meet up.

Once the highlighted line changes to 0: , then orient retrograde and wait for perigee where you will meet the ISS. When you get close to perigee, burn until you return your ApA to the same value as the ISS. You should now be within only a few kilometers!

 

[ar81]

For a graphical explanation of alignment see this tutorial
[ame="http://www.orbithangar.com/searchid.php?ID=3074"]Tutorial: DG to ISS[/ame]

 

[Vipers]

For have the ISS orbit almost above me, I have to
wait 24 hours, but so the launch launch time does not happen at really time (11 Mar 2008 06:28:12 UTC)

is normal this?

 

[rocketman768]

For have the ISS orbit almost above me, I have to
wait 24 hours, but so the launch launch time does not happen at really time (11 Mar 2008 06:28:12 UTC)

is normal this?

If you are talking about [ame="http://www.orbithangar.com/searchid.php?ID=3263"]Search[/ame] and you are using the "STS-123 FD1 Launch 11 Mar" scenario, then you should launch immediately after starting it. The orbit of the ISS passes almost directly ahead at the very beginning of this scenario.

 

[Vipers]

This is the situation at the beginning of the mission "STS-123 FD1 Launch 11 Mar" , the ISS is not above me.

why?

 

[DaveS]

This is the situation at the beginning of the mission "STS-123 FD1 Launch 11 Mar" , the ISS is not above me.

why?

It isn't supposed to either! All that matters is the ground track of ISS, which is over the launch site which is when you want to launch.

 

[C3PO]

It isn't supposed to either! All that matters is the ground track of ISS, which is over the launch site which is when you want to launch.

Correctemundo. As long as your Sma is shorter then the target Sma, you will catch up to it eventually. As you can see on OrbitMFD, your orbital time (T) is 5,225 s compared to ISS's 5,476 s.

Your ApA is a bit high for an initial orbit. I usually aim for somewhere around 150 km. That way you can catch up much sooner. You should gradually raise your orbit as you get closer, to minimize the encounter velocity. On the last orbit should be around 10-20 km below your target. You can use the RendezvousMFD for the... er.... rendezvous.

 

[Vipers]

I was having problems in aligning orbits whit the iss becauseI was using the "Nonspherical gravity sources", without it is more simple:woohoo:.

Some of you succeeded to aligning orbits whit this options enabled?

 

[darian]

The best time to launch is when "time to node" is 310s, using launch mfd this is the time it takes the Shuttle to reach half orbital velocity, the time you will be achieving a speed suitable to align planes. Once your in orbit, hopefully if you launch with correct time and azimuth you can get a rinc of 0.0x. If so wait to catch up with ISS. It could take anywhwere from few orbits to many orbits.
Using the synch mfd once your distance in longitude is down to only a few degrees its time to raise your orbit to match exact with the iss. Thats with rinc 0.00 and ecc ~0.0000. Now once you get all orbital elements as close as possible with ISS wait till you catch up with a distance in longitude to be either -0.00 or +0.00. This means you can either be coming from infront or behind. Once iss is within a few km then you can use trans thrusters to close relv and use docking procedures to dock with the module. Hope this helps. I just docked last week with ISS using SSU.

 

[Quick_Nick]

If you're new to rendezvous and docking, I recommend starting with the DG using these tutorials.
http://www.eharm.net/shop/freeware/orbiter/tutorials/tutorials.html
Mainly the Align Orbital Plane, Sync with Station, and Docking with Station tutorials, though you may need the launch tutorial as well.