Thank you

[ivan_w]

I just picked up on Orbiter again after a few years hiatus.. By then I had only managed to try to fire the thing up and maybe get a couple of times in orbit...

Got the latest version a couple of days ago..

Watched a couple of the instructional scenarios (scenarii ?)..

Decided to try it myself.. Dock with the ISS..

2 attempts failed miserably.. (Always funny zooming past your target at 150 m/s after a couple of hours of tweaking orbits & whatnot - Nice Oh dear moments)..

Then finally managed to get it right (well.. to get what I intended to do : Dock with the ISS).

I know, it was only the DG, spherical gravity source..

But on my 3rd try - having downloaded the sound package and after a couple of hours of orbit readjusting, Fighting to nullify Delta V to my target, scratching my head on how to use RCS in linear mode, getting frustrated at aligning the dang thing, slowly approaching Docking port 1.. I finally heard a series of 'clank clank clank'... Taking a peek at the exterior view - Yeap - I was docked.

And for one fleeting brief instant, I was no longer in front of my computer.. I was *REALLY* in command of a space ship.

Priceless.

Thanks !

--Ivan

PS : I'm not there yet though - and I hope I'll get more moments like this.. Will eventually try using the non-spherical gravity, gravity torque & whatnot - dock with the rotating Lunar Orbiter and interplanetary travel.. But the learning experience is great

-- To me, it's not to be there that counts, is HOW you get there that's important.

 

[fireballs619]

Sounds sorta like my Orbiter experience- except I still zoom past my target at 100s of m/s :lol:. Seriously though, if you need some tutorials, there is a whole section of them here that is often overlooked. Personally, I would say to go with Go Play in Space- it is truly invaluable.

Of course, if you have any questions, feel free to ask the in the 'General Questions and Help' Forum (just make sure you have read the manual ). Happy Orbiting!

:hail:

 

[ivan_w]

But when you think about it..

Being able to connect with an object traveling in circles at more than 4500 Mph with less than 1 inch precision (and you starting at ~1000 Mph (earth rotation)).. And knowing they ACTUALLY do this for real (it's not just a game - it happens for REAL) - and being able to reproduce (some) of the mechanics involved...

Have to say.. The 'inboard computers' (the MFDs) help a lot.. The calculations involved aren't trivial!

Knowing they did this in the 60s (hat was the 1st In-Orbit Rendez Vous ? The Agena Target ?) with rulers ?..Phew !

And knowing we can reproduce this today on a desktop computer just for fun..

Amazing...

--Ivan

 

[garyw]

Knowing they did this in the 60s (hat was the 1st In-Orbit Rendez Vous ? The Agena Target ?) with rulers ?..Phew !

Didn't they have sextant on board Gemini as well?

I also recall that Buzz Aldrin had to manually calculate their intercept vectors when the new rendevous computer system utterly failed on him.

Amazing stuff.

This book is interesting reading -> http://www.amazon.co.uk/How-NASA-Le...=sr_1_2?ie=UTF8&s=books&qid=1284859548&sr=8-2

 

[ivan_w]

Ah..

That'd be an interesting add-on I think (IF not already done) : Star navigation !

Or like the Apollo 13 return.. When (according to the flick - don't know about what really happened) used the sun as a ref point for the re-entry interface burn.

 

[Izack]

That'd be an interesting add-on I think (IF not already done) : Star navigation !

Well, there is a Sextant MFD. Also, I heard that the NASSP Apollo spacecraft contains a replica of the software they used to navigate (although I really can't confirm that, having never used that addon.) Orbiter's core contains a display of the stars used by the Apollo missions for navigation.

 

[ivan_w]

Ah ! Thanks!

But gracious.. I'm already having troubles with all the modern tech computerized nav helps

But it's nice to know I can eventually (pretend to) turn myself into one of those early explorers and pioneers.

No doubt, trying to perform a rendez vous using star maps, Ephemeris & a sextant sure must have been quite a challenge ! (And I'll try it.. When I'm up to it.. But it may require a few year of College - But then again - That's what Orbiter is about right ?)

--Ivan

 

[statickid]

i believe there is a sextant mfd.

just a thought here...

If I were you i'd just go ahead and turn on the gravity torque and non-spherical blah blah etc etc... IMO they don't make it any harder to use orbiter, but it will be more realistic! These are subtleties and you might not even notice the difference unless you know what to look for.

also its good to use limited fuel, coz some of the vessels can't fly unless they get lighter

---------- Post added at 07:14 PM ---------- Previous post was at 07:13 PM ----------

oops izack beat me to it lol

 

[ivan_w]

If I were you i'd just go ahead and turn on the gravity torque and non-spherical blah blah etc etc... IMO they don't make it any harder to use orbiter, but it will be more realistic!

Oh.. I'll do it

Hey.. I started a couple days ago - Don't expect me to become an accomplished space pilot in 2 days

But I'm working on it !

(The thing I was trying to say is that I appreciate the work of those who did this - because it helps me understand things better.. I know I only have an incomplete view, but hey.. 1 thing at a time, So next : No spherical grav fields.. and Next Grav torque[1]).

--Ivan

[1] Question.. Besides non spherical grav sources & grav torque.. Does Orbiter simulate more than a 2 body system ? (that is, does the moon, the sun, jupiter, and any other grav source alter my motion - when I'm orbiting the most influencal grav source : earth (when orbiting earth) ?)

 

[statickid]

hmmm... there are lagrange points, i believe this would be evidence of this,

 

[ivan_w]

Well..

I didn't know the Lagrange points where in it..

(I'm discovering this as I go..)

But for some reason, I wasn't really doubting it

Thanks!

--Ivan

(Still learning)..

---------- Post added at 02:47 AM ---------- Previous post was at 02:35 AM ----------

(Posting to myself.. I know bad form. but anyway)..

I realize my question about n-body system for LEO is moot.. The influence of any of the other objects would probably throw me what.. A couple meters off when dealing with KM distances ?

In interplanetary trajectories, you DO count on them.. But not in LEO. Because the influence of earth gravitational field is multiple magnitudes higher than any other grav source.. (You know.. Inverse of square rule)..

So I apologize for my remark which was quite rhetorical..

The thing is I though that earth non spherical nature was in that order too.. But I know I was wrong there now too..

As I told you - just learning !

--Ivan

 

[statickid]

this is orbiter-forum, nobody's gonna call you a nOOb for asking questions and learning. this is a real forum for asking questions and discussion, not an elitist snob-fest where people make fun of you for not knowing something! :lol::tiphat: also i don't worry about posting to yourself alot of people do it all the time and there is no need to apologize for asking questions

 

[Tommy]

The Orbiter core does use a multi-body solver to calculate a vessels position, but most MFD's use a simplified 2 body solution for their predictions.

Non-spherical Gravity sources doesn't make rendezvous harder as much as it makes it more confusing. It's not a bad idea to leave that option off until you can rendezvous repeatably. Once it's on, there are a couple slight "tricks" to make it less of a problem. The target's Pe will be moving - but if you watch it will tend to swing back and forth on one side of the orbit. When raising your Ap, aim for the middle of that "swing". Then, raise your ApA to a couple kilometers higher than the ISS's PeA, and use SyncMFD set to "Ship-Ap" or Intersect, not Target-Pe.

As for Gravity Gradient Torque, about the only time you'll notice it is during the final docking approach. It will cause your vessel to slowly drift out of rotational alignment with the dock, so you'll have to toggle the RCS back and forth between Translation and Rotation quite a few times. More of an annoyance than it is a problem.

And yes, questions are welcome here. It's clear you've taken the time to try to figure this out, and have read the docs and other threads. You ask sensible, intelligent, and specific questions, and we like answering that kind of question.

Of course, if one were to ask "How do I raise the landing gear in a DG" we will tell you "You can raise the gear by reading the manual".

 

[ivan_w]

The Orbiter core does use a multi-body solver to calculate a vessels position, but most MFD's use a simplified 2 body solution for their predictions.

Actually, I'm pretty sure I could have read this in the documentation

As far as the physics is concerned, I'm pretty sure it's quite accurate (at least as far as newtonian physics is concerned (including an n-body system).. As far as non-newtonian physics are concerned (What the heck ? effect of negative energy? Effect of traveling at 10E-9 of the speed of light), I believe Dr Shwieger decided to leave them out (as far as I read anyway).

Well.. That's at least accurate enough for me trying to dock with a moving object in orbit. even with the current MFDs that don't into account everything (basically assumes a static frame of reference - that's my experience with the docking MFD which doesn't take into account I'm actually moving in orbit - and keeps drifting - and that's expected!)

And it still makes i an enjoyable experience. (Yes.. You still have to hand-correct drifts while docking.. At first I was a bit surprised about the drift I was experiencing, then I realized - Hey, I'm in orbit - our orbits won't match until we're docked, so there is going to be some drifting).

I am at awe on how realistic this simulation is (as far as I can understand)! No, It doesn't make it easy - And that's suppose to be that way. And I'm also amazed how some people seemed to have found some very low energy docking solutions - although not very safe.)

--Ivan