Vessel I have an idea for a new add-on (XR2 - DGIV)

[MessiGamer]

imagine how cool it would DG - IV or XR2 ravenstar with fuel tanks, like Atlantis or Buran :thumbup:
But it is possible? and if it's because nobody has done yet? I know nothing of making addons but it would be cool!

sorry for my english xD

 

[Loru]

[ame="http://www.youtube.com/watch?v=FrNUHxO-hMo"]http://www.youtube.com/watch?v=FrNUHxO-hMo[/ame]

and rocket in question: [ame="http://www.orbithangar.com/searchid.php?ID=6216"]http://www.orbithangar.com/searchid.php?ID=6216[/ame]

Works with XR1, XR2, DG-IV and stock Delta glider.

 

[birdmanmike]

Oh gosh, seek and ye shall find - much more of this and I'll end up going back to Orbiter 2010 to do things properly . . . cheating, too much use of unlimited fuel in DG IV at moment :blush: (keep running out of fuel when trying get to ISS)

 

[Urwumpe]

Oh gosh, seek and ye shall find - much more of this and I'll end up going back to Orbiter 2010 to do things properly . . . cheating, too much use of unlimited fuel in DG IV at moment :blush: (keep running out of fuel when trying get to ISS)

Just take it slow with the ISS - the faster you try to dock, the more fuel you waste along the way. The Space Shuttle does the docking with a few 100 m/s, that is way less than what you have in a nearly empty DG IV.

 

[birdmanmike]

Trouble is, I keep ending up thousand clicks or (much) more away after align and synch - even using the checklist flight. When I'm lucky enought to get a little closer, the ISS is always ahead of me in the orbit and moving faster. Can't catch up using linear thrusters and main engine just busts me out of circular orbit. Part is not paying enough attention to launch time - guess I ought to launch before the ISS overhead and keep better control of the heading - too much drift or even yaw spin sometimes means effectively thrusting retrograde before while still reaching orbit

 

[Urwumpe]

Trouble is, I keep ending up thousand clicks or (much) more away after align and synch - even using the checklist flight. When I'm lucky enought to get a little closer, the ISS is always ahead of me in the orbit and moving faster. Can't catch up using linear thrusters and main engine just busts me out of circular orbit. Part is not paying enough attention to launch time - guess I ought to launch before the ISS overhead and keep better control of the heading - too much drift or even yaw spin sometimes means going backwards

That is no problem. The checklist in the manual is just for getting you close, but it still requires you to pilot the spacecraft.

And you don't need the ISS to be overhead of you. You need to launch when you are in the same orbit plane as the ISS, when the ground track of the ISS is passing over your launch site.

Finally: Don't use linear thrusters, when the distance is larger than 100 meters. You can still use the synch orbit MFD at larger distances to approach the ISS. The trick is passing the intersection with the orbit of the ISS at the same time as the ISS.

And remember that spaceflight is not really intuitive if you are using relative navigation between two spacecraft:

If you are far behind the ISS, just slow down a bit with RCS, so you catch the ISS on the next orbit.
If you are far ahead of the ISS, just accelerate away from the ISS, so the ISS catches up with you.

Here is a small article in OrbiterWiki (with cute little graphics I had made )

http://www.orbiterwiki.org/wiki/Rendezvous

 

[SolarLiner]

Rendezvous and docking is a tough skill to learn. There is work to do to a successful rendezvous alone. I always found the actual docking part quite easy, thanks to the useful Docking MFD.

 

[birdmanmike]

Thanks guys, more practice (and patience). I had most of this couple of years back, now it's re-learn. Yes, the actual docking is easy enough - I'm fairly OK with thrusters - but it's the Synch Orbit just bugging me. Can get right orbit but too far way - or when trying to Synch by pushing Apo out and then resynching, it's a lottery - and I never get the numbers. The manual gets me - one place it says get matching on one orbit and wait, elsewhere ship on orbit 0 and target on 1. Oh well.

 

[Urwumpe]

Thanks guys, more practice (and patience). I had most of this couple of years back, now it's re-learn. Yes, the actual docking is easy enough - I'm fairly OK with thrusters - but it's the Synch Orbit just bugging me. Can get right orbit but too far way - or when trying to Synch by pushing Apo out and then resynching, it's a lottery - and I never get the numbers. The manual gets me - one place it says get matching on one orbit and wait, elsewhere ship on orbit 0 and target on 1. Oh well.

Well, the MFD is simple in its function, but correctly interpreting it is an art. Sorry to say it that way.

It starts out with helping you making sure you pass the same "finish line" as the ISS at the same time. And ends with you also matching the place, where you pass this "finish line".

The problem is not the MFD but knowing where you are on the route to the ISS. That is much harder. The times converge at the intersection (which means "same place at the same time"), but still you have no idea: Am I close enough now to trust the numbers, or will I have to correct in the next orbit? And in which direction do I have to burn?

 

[Lmoy]

Like Urwumpe said, if you're behind the ISS, slow down to lower your orbit. This will speed you up relative to the station. Similarly, speed up to raise your orbit and slow down relative to the station, if you're ahead of it. Do this once your planes are matched, and you'll gradually drift towards it. Fine tune your orbit as you get closer to lower the difference in your orbit sizes, watching your intersect distances as you do this, and it ends up being quite easy to put yourself with ~1 km from the station, then you simply match ve‎locity with it, then  point yourself at it and use your RCS to slowly drift in to a successful docking.

 

[birdmanmike]

So I aligned (.009), synched, and got to 94 k away and relative velocity of 56. Long period of playing with thrusters versus velocity markers, I could not reduce the rel V whatever I tried, following the manual, aligned HUD on the marker, tried lowered orbit to speed, then raised, all I got was mismatching elipses, by the time I corrected those waiting for Apo and Peri, was even farther apart. Gonna go EVA and do a Gravity . . .

I'll sort out what I'm doing wrong - as said, used to be able to. Now rubbish. Thanks for the tips though . . .

 

[Ripley]

SyncMFD also tells you your RInc.
Do you arrive at rendezvous on the same plane as your target?

 

[birdmanmike]

that .009 was RInc, after DN then AN - second thrust time 1.43 secs

 

[Urwumpe]

So I aligned (.009), synched, and got to 94 k away and relative velocity of 56. Long period of playing with thrusters versus velocity markers, I could not reduce the rel V whatever I tried, following the manual, aligned HUD on the marker, tried lowered orbit to speed, then raised, all I got was mismatching elipses, by the time I corrected those waiting for Apo and Peri, was even farther apart. Gonna go EVA and do a Gravity . . .

I'll sort out what I'm doing wrong - as said, used to be able to. Now rubbish. Thanks for the tips though . . .

Can you make a screenshot of your sync orbit MFD when you are approaching your target? Maybe it is easier to describe the "dark arts" to you, if we go through the data with you.

 

[birdmanmike]

had a crash and lost that one now taken off again. currently RInc of .05 very close orbit parameters but about 7.702M away from ISS and RVel 8.779k a long way off! screenshot attached, save done. will now try for a bit closer

 

[Urwumpe]

had a crash and lost that one now taken off again. currently RInc of .05 very close orbit parameters but about 7.702M away from ISS and RVel 8.779k a long way off! screenshot attached, save done. will now try for a bit closer

Yes, DTMin is the interesting value there. You need it to be 0.0 seconds and stay there. 1800 seconds is one of you or the ISS is arriving half a hour late.

 

[birdmanmike]

OK see again, now 7.799m behind DTM zero using RCS, currently peri lower than ISS seems to me orbit 3 will give intersect, when I should prograde to match velocity? (as will be at Apo and need to raise peri also to match?

 

[Urwumpe]

OK see again, now 7.799m behind DTM zero using RCS, currently peri lower than ISS seems to me orbit 3 will give intersect, when I should prograde to match velocity? (as will be at Apo and need to raise peri also to match?

I would wait for intersection in Orbit 3 and decide shortly before the intersection then how you need to correct. From Orbit 3 on you should be able to switch to intersection #2 for example and correct for DTMin=0.0 on the next passage of this one, by remembering the old Gemini Pilot rule:

Up means Aft, Aft means Down, Down means Forward, Forwards means Aft.


Don't correct too much! Let Newton have a bit of fun as well.

 

[birdmanmike]

Well sadly my peri was too low, few minutes later hit the atmosphere, so will try raising a bit with retro now? and refine again . . huh - put synch back to orbit 4

 

[Urwumpe]

Well sadly my peri was too low, few minutes later hit the atmosphere, so will try raising a bit with retro now? and refine again . .

Oh my fault. I should also have looked at the PeR :facepalm: Just keep your perigee out of the atmosphere, but a bit lower. You only need a good difference in T (which depends on Sma) to catch up with the ISS. It can take a few orbits to catch up if you have only a few dozen kilometers between ISS and atmosphere... unless you try something wild, like putting your apogee high into the sky, at the costs of a lot of fuel. But we want to conserve propellant, yes?