Kill Relative Velocity?

[SWAFO]

It seems that in about 1/5 tries I can approach and dock at the ISS.  The other times, the relative velocity keeps
running away.  I've downloaded REDSHIFT, and I've got the same problem with it.  It seems that It will first get rid of
the relative velocity to the ISS, then travel towards it (and occasionally go all the way to it), othertimes it will
continuously realign itself to the velocity marker, and keep trying to "Kill relative velocity".  

Why am I having these issues? Is there any foolproof way to dock on the first time, every time using REDSHIFT?  All
help is appreciated.

Thanks,
Brad

[She_Da_Lier]

Attitude MFD

[SWAFO]

What?  What does this mean?

[SWAFO]

I downloaded the attitude MFD, but for some reason it doesn't work.  When I activate the module it gives me a DLL
error in orbiter.exe.  

Also, I've already got my MFD selection screen full of entries.  How can I hold more?

Thanks,
Brad

[SWAFO]

I tried to install the rendezvous MFD, and it gave the same error as well... wonder what it is

[SWAFO]

It seems that I'm normally about 500KM away from the station when I start my approach.  I've read about getting
into 50KM... how would you do this in synchronization?

[Demosthanese]

I usually try to launch behind the station into LEO about 50-150 KM below the station I want to get to, depending on how far
away it is. The lower the orbit, the faster I will catch up, but the greater the requirement for a prograde burn. If I'm far
below the target, I wait untill I am nearly caught up, and then I perform a prograde burn to raise my altitude up to it's
level. I keep an eye on the sync orbit MFD and try to keep the DeltaMin as low as possible. a DTMin of 0.00 means that you
will hit the station when your orbits cross. Now, just wait for when you are close to the station, kill your relative
velocity, and line up to dock.

Try out trever's guide. It will give you the basics on how to rendeavous with distant objects

[SWAFO]

I didn't see anything in his guide on docking... I'll take a second look.

[SWAFO]

I finally figured out that I had to download a patch for Orbiter... lol.  Now the Rzendevouz MFD and Attitude MFD work
just fine... how do I use them to dock with the ISS though?

[SWAFO]

Damn REDSHIFT won't stop chasing the relative velocity.  I've searched ALL the forums, and everywhere else I can
find, and I've got no luck.  How can I get the relative velocity to stop running away, and simply dock with the ISS?  It
happens a good one out of 10 times now!  VERY FRUSTRATING!

[SWAFO]

The planes are aligned, the orbit is synched... yet I'm always 500KM or so away from the station, and the relative
velocity won't DIE!!! What am I doing wrong!

[SiberianTiger]

SWAFO wrote:
The planes are aligned, the orbit is synched... yet I'm always 500KM or so away from the station, and the relative
velocity won't DIE!!! What am I doing wrong!

I'm not sure I can help you to do transfer using Redshift, I never used this utility. When I fly a Delta Glider, I always
do such transfers manually. The possible cause for your not being able to kill relative velocity may be that you and ISS
have different altitudes. Let me illustrate this:



Here you can see your ship orbiting Earth in a lower orbit than ISS. If both orbits are circles, you always will go faster
than ISS, because of lesser period. Look, the angle covered by ISS is less than the angle, covered by the ship. This
means, it's angular speed is smaller, as well as a ground speed. Use this effect to catch up with ISS, in most cases,
when you do orbit insertion, you are well behind. Spending several orbits in the chase orbit helps to arrive in the
point where you can start your transfer. Here is the scheme for a Hohmann transfer manoevre:



Hohmann trajectory is an ellipse tangetial to source and target orbits. ISS has higher enegry than your ship, so in
order to do a transfer, you must apply some force. You do it twice: first burn ejects you into transfer trajectory,
second one you do in the vicinity of the ISS to eliminate relative speed (by doing this, you insert yourself precisely into
ISS's orbit). The most important thing is timing of the manoevre, which can be achieved ising many different
instruments: Transfer MFD + Synchronize MFD (followind procedure described in the manual), Rendez-Vous MFD,
Interplanetary MFD (those I know how to use). Study the pictures. If you need additional instructions, let me know.

[Demosthanese]

SWAFO wrote:
I didn't see anything in his guide on docking... I'll take a second look.

It doesn't, but it teaches yyyou how to get close to an object in orbit. Same rules apply for getting to the ISS that you
used to get to Phobos.

[SWAFO]

Thanks for the info. It's still a lot for me to wrap my brain around (as I previously mentioned, I'm used to flight in our
atmosphere).  I downloaded the Rendezvous MFD, but it's a little difficult for me to understand.  Fact is, I hardly
understand any of it! It's all a bunch of lines to me!  If you'd describe a rendezvous using the rendezvous MFD in
terms that the average idiot could understand, it'd be much appreciate.

I understand what you're saying about altitude, and that's probably my problem.  When I'm within range of the ISS
(500KM), should I adjust my PeD or AeD to be at the level of the ISS?  Would that help at all with killing the relative
velocity later on?

[SiberianTiger]

SWAFO wrote:
Thanks for the info. It's still a lot for me to wrap my brain around (as I previously mentioned, I'm used to flight in our
atmosphere). I downloaded the Rendezvous MFD, but it's a little difficult for me to understand. Fact is, I hardly
understand any of it! It's all a bunch of lines to me! If you'd describe a rendezvous using the rendezvous MFD in
terms that the average idiot could understand, it'd be much appreciate.

Sure, but I'll better describe it in detail tomorrow (it's time to go sleeping for me now). Rendez-Vous MFD is a handy
instrument which helps you to do free-trajectory approaches, like real space ships do.

I understand what you're saying about altitude, and that's probably my problem. When I'm within range of
the ISS
(500KM), should I adjust my PeD or AeD to be at the level of the ISS? Would that help at all with killing the relative
velocity later on?

This is roughly the time you should start setuping your transfer burn. Needless to say, your orbital plane must
already be aligned with the ISS'. Let's use Transfer MFD to do transfer (I find it more handy to use than Sync MFD).
Select the ISS as target by TGT button. Click HTO to show a hypothetical transfer orbit. Click DV+ until it touches the
ISS' orbit. A grey radial line should appear. Now look closely at MFD. Your current position is green solid line, the ISS'
position is solid orange line, its future (post-transfer) position is denoted by the dashed orange line. Grey line is
where orbits intersect. Now, click EJ+ until you superpose the grey line over the orange dashed one. Note that a
green dashed line appears. If you lose the grey line because of the ISS' orbit eccentrisity, increase DV once again (or
decrease if your HTO gets too high over a target orbit).

Understand what you did? Now, once you arrive in the point where dashed green line is (DTe value drops to zero),
you start propagade burn and watch as your orbit becomes matching with the HTO. Cut your engine as Dv value
reaches zero. Now, if everything done correctly, just coast until rendez-vous which is likely to occur about 50 minutes
later, half-orbit away. Switch your HUD to the docking mode, tune it to the ISS XPDR (Shift+Ctrl+R, or Alt+Ctrl+R or
some of the sort key combo). Wait until relative distance becomes minimum (for using Transfer MFD below 5 km is
fine) align with relative speed vector (a circled cross) and fire your thrusters until killing all relative velocity.
Congratulations, you are in station keeping position now!

Tomorrow I'll cover the Rendez-vous MFD.

[SWAFO]

I'm going to try the methods you recommended with the Transfer MFD here in just a minute.  I've been able to
succesfully use the Align and Sync MFD's to appropriately set-up orbit with the ISS, however as I mentioned the
relative velocity won't stay near zero.  I'll try with the Transfer MFD following your methods, and let you know how it
works!

Thanks!

[SWAFO]

Ok, I printed out your suggestion, and tried it!  No luck!  Everytime I get the "Dv" value near zero, I've burned so
much in retrograde that I burnup in the atmosphere!  

The sync orbit MFD is MUCH easier for me to use (however it doesn't seem to be getting me to dock with the ISS).  
I'm frustrated to the point of almost giving up!  Perhaps when you explain the Rzendevous MFD, I'll understand that
better (although I've already noticed that the Rzendevous MFD doesn't work when you're as far away from the ISS
as I normally am!!!)

[SWAFO]

Alright, I also tried having a LOWER orbit altitude than the ISS (as you had suggested also).  I prefer to use
REDSHIFT for my docking (it allows automatic docking), and it's the only thing I've had success with thusfar.  
Unfortunately, the damn thing still chases the relative velocity!  Orbits are aligned and synced, and I STILL CAN'T
CATCH THE DAMN ISS!

I'm really beginning to thing Orbiter's not for me!  I'd like to use it, but it's so goddamn hard!  Where's my EASY
BUTTON?

[Atom]

In a low orbit you will have a higher velocity than you would in a high orbit. You can use this to either slow down or speed
up. If you need to catch something up, lower your orbit, if you want your target object to catch up with you, you give
yourself a larger orbit.

It's all quite confusing. Which is probably why only I understood it fully quite a while after starting playing Orbiter.

[SiberianTiger]

SWAFO wrote:
Alright, I also tried having a LOWER orbit altitude than the ISS (as you had suggested also).  I prefer to use
REDSHIFT for my docking (it allows automatic docking), and it's the only thing I've had success with thusfar.  
Unfortunately, the damn thing still chases the relative velocity!  Orbits are aligned and synced, and I STILL CAN'T
CATCH THE DAMN ISS!

I'm really beginning to thing Orbiter's not for me!  I'd like to use it, but it's so goddamn hard!  Where's my EASY
BUTTON?

Don't give up! The problem is, I don't see the situation you are talking about and it's hard to decide by your words
what your position in relation to the ISS is, what is that relative velocity and how it's directed... So I must have given
you wrong advice based on wrong assumption of your whereabouts. If you don't mind, please, contact me by mail or
ICQ (both may be found in my profile), send me a JPEG-cmporessed screen shot of your orbit MFD with ISS selected
as a terget so I could have a glimpse of it. Remember, while you're in orbit, you can always intercept your target.

[SWAFO]

I just downloaded a guide: http://smithplanet.com/stuff/orbiter/orbitaloperations.htm

I'm going to follow the steps in this, and see if it helps.  I have a feeling it might.  I'll let you know

[SWAFO]

The methods described at that manual WORKED!!!! I now approach the ship within 10KM each and every time, then
activate the REDSHIFT program to head to an auto-dock!  EXCELLENT!