Question Soyuz TMA Mass & Fuel accuracy?

[EliNaut]

One thing I've noticed when i've taken the Soyuz TMA (cvel) up in orbit on a mission to the ISS, I never have enough fuel to get there. Most of it is exhausted on orbit synchronization. So.. if this is an accurate model, how the do they get to the ISS in real life? Either somethings off, or theres another method of orbit synching that i'm not aware of out there that uses less fuel. :huh:

Anyone?

 

[Zatnikitelman]

What's the procedure you use to synchronize to the ISS?

 

[clive bradbury]

It can be done. Take a look at my 'soyuz to iss' tutorial on OH. Scenerio included.

 

[Urwumpe]

It should be easily done. You should NEVER forget: Soyuz needs 1.5-2 days for traveling to the ISS. Maybe there is a deeper reason behind why it is traveling slow and careful.

You don't get to the ISS with shedding your fuel all over the place. That especially applies to the RCS: You can waste a lot of propellant for meaningless orientation changes. You don't need to rotate fast and you often don't need to rotate at all.

The fuel inside the Soyuz TMA should be equal to 900 kg. That is a ΔV of only 390 m/s. You could have about 50-80 m/s left if you are very accurate.

So, if you reach the ISS with just barely enough fuel for deorbit: You have done it! Applause!

 

[EliNaut]

Yeah I got your tutorial, Clive.

I was performing my synchronization in a manner that I performed my synchronization burn at my apogee, as I was used to doing with a few other vessels. Never really thought about the fuel usage differences in the two methods.

Can't wait for a new Soyuz model to come out!

Cheers guys,
-Elinaut

 

[MajorTom]

Yeah I got your tutorial, Clive.

I was performing my synchronization in a manner that I performed my synchronization burn at my apogee, as I was used to doing with a few other vessels. Never really thought about the fuel usage differences in the two methods.

Can't wait for a new Soyuz model to come out!

Cheers guys,
-Elinaut

I was playing with Clive's tutorial all weekend, so I have it fresh in my mind.

I managed to get to ISS (or the Salyut 6 I'm working on) with plenty of fuel left over, with fuel percentage numbers similar to what Clive provided as examples throughout the tutorial.

The biggest possible fuel waste that I can see it trying to change the plane of your orbit. I steer my launch vehicle as carefully as possible to get my Rinc (between my orbit and the target orbit) as close to zero as I can. Then I save tons of fuel by not having to burn it all in aligning planes.

MT