Question How to fly a Soyuz from launch to the ISS?

[Cosmic Penguin]

The Soyuz is currently the only way of travelling to and from the ISS, so I would like to ask if there's a tutorial for setting up an approach and docking with Throton's Soyuz TMA (and the Soyuz launcher). To make things a bit easier, please use real historical orbit parameters for the ISS for a certain mission (they can be found if you have an account at Space Track) and real launch times/target orbit/fly plans for a certain mission (e.g. here). Apparently the limited fuel made approach very difficult. Thanks! :tiphat:

GPS

 

[N_Molson]

It isn't that difficult. I did it with 80% of fuel left. Avoid x1000 time acceleration, since precision is needed there. Also don't forget you have 3 engines modes (300N, 700N, 6000-ish N). The two first modes are very handy when you need to make precision burns. The RCS submodes are also a must-use to save fuel. "continuous" should be used only for final approach or contingency. I use the 0.05 sec impulse most of the time, and use the keyboard to manoeuver the spacecraft even though I have a joystick (when you use the joystick, RCS is always in continuous mode), that's very fuel efficient. Plan your manoeuvers, anticipate, and take the time.

The key is to launch right on time, and this is a matter of seconds. If your Rinc with the ISS is > 0.1° once in orbit, you know you've missed the launch window. It is really possible to achieve a < 0.03° Rinc at orbital insertion. LaunchMFD helps but isn't enough, you'll have to do some trial and error to find the exact right moment.

A 2-3 days typical orbit synchronisation requires little Dv. What you will have to do is to perform periodic plane corrections, because your orbit is disturbed by the usual factors (Earth non-spherical, Moon, traces of atmosphere...). Small and frequent corrections seem to work the best (since you keep your orbit close to the ideal 0° Rinc theorical path which is used by SyncOrbitMFD to make the calculations).

On final approach anything > 0.03° is unacceptable. You need to be really careful and fine-tune the Rinc on the last orbit before rendez-vous. I don't go over x10 time acceleration at this point.

Docking itself has nothing extraordinary about it. The SoyuzTMA is manoeuverable enough. I guess you should align with the docking port "corridor" and begin the docking run at 1.5 km from the station to make it realistic.

 

[Cosmic Penguin]

I have made a handy discovery of the typical Soyuz ISS flight profile: for a certain flight (e.g. here's data in Russian for the Soyuz TMA-04M flight), three burns are made during the first two days in orbit. The first two are always done during the third and/or fourth orbit, while the third burn is made in orbit 17. The approach procedures are always started at orbit 33, with docking aimed for the daylight part of orbit 34.

There's one problem: since there're no automatic docking/approach system in the add-on, I will have to determine how to make the approach burns at orbit 33. I remeber there's a way to do it using TransX, but I have already forgotten about it. So how can I determine how to do burns to slow down towards the ISS?

 

[N_Molson]

What do you mean by "slowing down" ?

If you want at some point to lower the relative velocity between your TMA and the ISS, you can use SyncOrbitMFD ; as you "slow down" the time to intersection will rise as additionnal orbits are added.

If you want to "brake" during the rendez-vous when you arrive in the 1.5 km range to prepare the final approach run, the standard technique is to use DockMFD and press "HUD" to get the vector.

 

[sorindafabico]

To get a good timing for automatic launch, you can use this tutorial.