Has anyone successfully rendezvoused with the ISS?

Tim13

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Just a curiosity question. With the SSU has anyone successfully rendezvoused with the ISS?

Been thinking a lot about this lately, but can't wrap my brain around how to do the burns. I can shoot from the hip, but my experience with the old shuttle fleet tells me that won't be good enough. I remember a lot of orbital massaging with the OMS engines in real time using the velocity vectors and deltaV information, that won't be available with the SSU.

So, has anyone actually done it?

Any tips?

Tim
 

Urwumpe

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Sure, pretty often... but since we have no mission control center, I cheated with IMFD and a slide rule...
 

Tim13

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Sure, pretty often... but since we have no mission control center, I cheated with IMFD and a slide rule...

I'm sorry, you do not count. You are too smart. :thumbup: :lol: :tiphat:
 

Urwumpe

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I'm sorry, you do not count. You are too smart. :thumbup: :lol: :tiphat:


You would be shocked, if you would really know the truth.... :tiphat:



If I can do it, anybody can.
 

Wolf

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As Urwumpe said the use of some generic MFDs can surely help. In the past I used Align Planes and Sync Orbit MFD to assist in Rendezvous targeting. Unfortunately SSU misses the full phasing and rendezvous capability; on top of that I believe OMS burns targeting need some tuning as it is not accurate. We have some good data available from NASA but only for a few missions:I tried to rendezvous STS-114 since for that mission we have all the burn targets detailed in section 4 (Attitude Timeline) of the Flight Plan but with no luck, don't know how much is due to my mistakes and how much is Orbiter and or SSU inaccuracy (we also have to consider we have no STS-114 payloads for SSU so the Orbiter mass is not matching the real one hence the OMS targets are probably off when you use them with SSU. I do not know if someone else has used those official data and did succesfully rendezvous with the ISS..

It looks like Gingin did a great job simulating STS-88, still he had to cheat a bit on the numbers (in relation to the actual mission ones).

Here it is: you might find it useful

https://www.orbiter-forum.com/showthread.php?t=40283
 

Thorsten

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May I shamelessly advertize and suggest giving LEO targeting a try for your mission design needs? It's intended as a lightweight tool to provide MCC-like computation capabilities.

It's a multi-platform commandline tool.

I'd be interested in getting some feedback from the Orbiter side as well - so far most users are from the FG community, but from what I hear, it handles things like AOA abort burn calculations rather well.
 

Donamy

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I don't think Orbiter has all the gravitational anomalies, the real Earth has. So there has to be some "cheating". But, It can still be fun.:thumbup:
 

Tim13

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You would be shocked, if you would really know the truth.... :tiphat:



If I can do it, anybody can.


Hahahahaha.....I'm pretty sure I had it right the first time. Anybody that still has a slide rule, and can use it....

Tim

---------- Post added at 11:15 PM ---------- Previous post was at 11:13 PM ----------

@thorsten I will look over your program tonight, and see if I have the grey matter to use it. Thanks for pointing it out!


I've been thinking of using a bunch of phasing orbits to sneak up on the ISS. Probably more than they did in real life, but even in real time, I feel rushed programming the onboard computer for a burn.....LOL. I figure if I bite off small chunks, then I can only make small mistakes? :rofl:

Tim
 
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Urwumpe

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Anybody that still has a slide rule, and can use it....

I just inherited the family slide rule. :lol:

My mother used it in school, before her my aunt, long before pocket calculators had been invented. Every student used such a tool at that time. Do you still think it requires special intelligence to use it? Next you might want to tell me that you need a PhD in engineering and physics to start a steam engine....

Don't make things harder than they actually are, same applies to docking to the ISS.

Of course the STS is a overly complicated beast.
Of course orbital mechanics is not easy. But there are tools created by smarter people than I am and those tools make it possible that even a German grunt like me can do this. So can you. :tiphat:



---------- Post added at 00:41 ---------- Previous post was at 00:39 ----------

I've been thinking of using a bunch of phasing orbits to sneak up on the ISS. Probably more than they did in real life, but even in real time, I feel rushed programming the onboard computer for a burn.....LOL. I figure if I bite off small chunks, then I can only make small mistakes? :rofl:


Considering that the Rendezvous checklist does the same, you are obviously on the right track. :thumbup:

https://www.nasa.gov/centers/johnson/pdf/567076main_RNDZ_135_F.pdf

Also, you have about 20 minutes for programming it and you can pause the simulation... well, that maybe unrealistic, but smart.
 

DaveS

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Don't be rushed entering the burn data. Remember, the burn can be scheduled hours in advance. It doesn't have to be entered at the last minute. AFAIK, only things you have to do is to maneuver to the burn attitude and ARM/PRESS both engines and the EXEC the burn at TIG-15 seconds. That is if you pre-enter the burn data ahead of time.
 

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Hey Tim,
nice to see you back :)

Indeed, it is very feasible to do some Rendez Vous with SSU.
The trick is really to planify what you want to do step by step.

First thing is to be already confident with standard Rendez Vous with powerful Spacecraft like the deltaglider.
Also, a good knowledge of Orbit , Align plane, and Sync Orbit MFD is a big plus.


These MFD are really the bread and butter of a virtual MCC center, plus a calculator to convert Metric data from MFD into Imperial one from the Shuttle.


It is the sum up I made, with all the different phase of a Rendez Vous like it is written in Nasa documents
https://www.orbiter-forum.com/showthread.php?t=40283


First, you phase. Chaser has a lower orbit than the target.
Here a table to help you to do that

http://imagizer.imageshack.us/a/img924/2806/Fekgrf.jpg


To know what is the difference of angle between the chaser and target , you can use the ship apoapsis fonction of the Sync MFD
It will give you the Dlng which corresponds to how many degrees you have to catch up the reach the target.
Hence, you adapt the shape of the orbit to adjust the catch up rate with table above


Here the Sync MFD, DLng is zero as we are on the final rendez vous phase

http://imagizer.imageshack.us/a/img924/1151/3qB4py.jpg






Second, you want to null the Relative Inclination between the two objects.
Align plane MFD and you do a burn on Y axis at node.
0.1° of Rinc= 100 ft/s ish of Shuttle DV ( 10 % of total)


Third, once you are close enough ( couple of degrees from Target), you start to reduce the catch up rate by increasing your orbit.


Finally, 2 or 3 orbit before the rendez vous, you match both apogee altitude, with a slightly lower perigee ( 6 Nm less than target) to have a shallow catch up rate and you can start using the Spec 34 GNC page to pinpoint the rendez vous ( less than 100 km from ISS)
You could have a look in the DPS pictionnary page 110 ( and we can provide you more info when you will get there of course)

https://www.nasa.gov/centers/johnson/pdf/359895main_DPS_G_K_7.pdf

Then Proximity operations etc


I would say , just try it phase by phase.
Start to well understand phasing first, then move to next step etc.
Finally, you will be able to do all the different part in one flight for a full rendez vous :)

It takes quite a lot of papers to write all the burn data and keep a track of where I want to go, but it is very feasible, no science rocket there
 
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Tim13

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@Urwumpe I guess I could go back to my early flying days, and see if I still have my E6-B flight computer, which is nothing more than a circular slide rule. Hmmmmmm.

@Gingin Thanks for the welcome. I lurk regularly, just don't post much.

Your tips and write-up will be most helpful....thanks for taking the time to do that.
I am proficient with the old shuttle fleet, and other craft, when it comes to rendezvous, but it's a bit easier to do with the number pad thruster control, without having to program a computer to make the burn at a specific time.

I like your idea of biting off smaller chunks, and then putting it all together at some point.

I appreciate the helpful discussion on this topic from all....

Tim
 

Thorsten

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I am proficient with the old shuttle fleet, and other craft, when it comes to rendezvous, but it's a bit easier to do with the number pad thruster control, without having to program a computer to make the burn at a specific time.

Actually, I don't think it is unless you have a good visual on the renderzvous target.

If you know what you want, the computer will give it to you exactly, the number pad thruster will not. And if you do not know what you want, the Shuttle is the wrong craft - then you need to sit down and work it out beforehand.

(A corollary is that there is no single situation known to me in which you would have to hurry up to program a burn - even launch aborts (which go quite a way in being exciting) are mostly a sedate affair in which nothing happens for minutes)).
 

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Very interesting discussion going on here. It brings up something I've been thinking about for a while--which Orbiter MFDs are not technically cheating, and what would it take to do anything without the ones that are cheating?

I can already imagine Surface MFD would be okay, and the radio and VOR MFDs. TransX basically allows you to calculate the data that MCC would give you, so maybe the only realistic way to get to Mars or something would be to have someone else draw up the plan for you in TransX, and then you fly it using only Maneuver Mode.

It would probably be a nightmare, but I'd like to try flying like that just once :D
 

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which Orbiter MFDs are not technically cheating, and what would it take to do anything without the ones that are cheating?

It really depends on what you want to simulate.

Assuming you're 'just' a spacecraft entering Earth system, you'd have only sensor information available - so there'd have to be a simulation of radar, which could track objects only for a while and would give imprecise information, from that you could reconstruct the orbits of contacts fully or partially, so rendezvous would have to be iterative affairs with intercept info being refined as you approach...

Assuming you're an Earth-orbit spacecraft, it matters what technology level you assume. Inertial navigation in the early Shuttle era is kind of blurring quickly, so you rely on radar tracking from the ground and state vector uplinks, and during approach to a site you need TACAN and altimeter. The advant of GPS basically wiped that need clean - now you have a navigation precision of meter-scale anywhere in low and mid Earth orbit - if you're used to the procedures before, it seems to go on magic.

So I guess given enough knowledge (a catalogue of orbiting objects) and technology (precise, drift-free inertial navigation), any MFD can be realistic.

You really have to consider a specific scenario to decide.
 

TMac3000

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Well, that's certainly one way to look at it--Ground can send you any sort of data your ship is equipped to receive. But can they actually see your periapsis/apoapsis/whatever change in real time? Or are they in a Heisenberg situation, where they can only estimate?
 

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Well, that's certainly one way to look at it--Ground can send you any sort of data your ship is equipped to receive. But can they actually see your periapsis/apoapsis/whatever change in real time? Or are they in a Heisenberg situation, where they can only estimate?


Lets say a salomonic: Both is true.



The accurate calculations require radar fixes and calculations = Even today, there is a tiny delay in the data. That is why spacecraft have the navigation and guidance for rendezvous onboard.



But with modern technology, the delay has become small enough that Doppler data from the communication system is good enough to get better orbit estimates with some radar fixes than in the past by radar fixes alone. Its almost real time now.




Also, even after some orbits, the calculated orbit is still within meters of the real orbit. Not enough for docking, but good enough for calculating long-range maneuvers.
 

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Very interesting. So...could one say that Orbiter is already realistic in terms of the kind of data you would have available? I'm pretty sure the Dragon capsule doesn't have anything like TransX :lol:

So what would be the best restrictions to put on myself in Orbiter to get the most realistic experience, if, say I want to go to Mars?
 

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I'm pretty sure the Dragon capsule doesn't have anything like TransX

TransX is not very sophisticated or accurate compared with what a normal laptop can run these days (you can install GMAT if you like, that's NASA's mission planning software). A spacecraft can be equipped with much better tools than that.
 
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