abject plea for help--iMFD

[canadave]

Hi all,

After years of being a loyal TransX user, I've finally decided to bite the bullet and try iMFD, which looks superior as a
tool to me at this point.

I've read the manual, I've read tutorials from jarmo's webpage, and I still can't get the hang of this thing.  The
tutorials all deal with launching from Earth into orbit, then going to a different planet; or they involve going from one
Jupiter moon to another.  All I want to do is go from ISS to Mars in a stock DG.  How hard can this be?

Very hard, it turns out  I'll be the first to admit my spatial pilotage skills are far from being top of the line, but I feel
like it shouldn't be quite this hard.  My first request: does anyone have a good SIMPLE tutorial that I might refer to,
one that my five-year-old brain might have a hope in hell of comprehending?

A specific question I have, aside from my more general plea for something that describes in simple terms the
functions of iMFD:

I cannot for the life of me understand the implementation of how to change planes in iMFD.  Obviously ISS and Mars
are in different orbital planes; how does do I resolve this when trying to make the trip using iMFD?  Am I supposed to
do some sort of align-plane maneuver PRIOR to ejection from Earth orbit?  But wait--I see there's an "Off-Plane Intercept" concept; am I supposed to just directly eject in a trajectory that will eventually resolve the planar difference?  And what's that Plane Change function I see in the Orbital menu, with the crosshairs?  It's not in the documentation as far as I can see.  I'm basically completely stumped.



Post Edited ( 08-25-05 08:58 )

[SiberianTiger]

canadave wrote:
I cannot for the life of me understand the implementation of how to change planes in iMFD.  Obviously ISS and Mars
are in different orbital planes; how does do I resolve this when trying to make the trip using iMFD?  Am I supposed to
do some sort of align-plane maneuver PRIOR to ejection from Earth orbit?  But wait--I see there's an "Off-Plane
Intercept" concept; am I supposed to just directly eject in a trajectory that will eventually resolve the planar
difference?

Yes, you are. And it's quite simple to accomplish in IMFD. There's major difference between TransX and IMFD: in the
prior, you define a sequence of stages. Each one of them deals with certain gravity center, for example, Earth, Sun
and Mars sequentially for each stage. In IMFD, you can have only "one stage" in the MFD. But how, do you ask,
should I move from LEO to interplanetary trajectory? The trick is on the Program selection page of the IMFD, where
you can select shared mode in the left-hand bunch of buttons. When enabled, two instances of IMFD opened in
left and right screens, pass common data from one to another considering certain rules. They are well described
in IMFD manual (page 4): Course mode feeds data to Silngshot, which, in turn, provides info for Orbit
eject, and all of them supply input to Crosshair control, Autoburning feature and the Map. You can skip studying
the Slingshot for a while, what you need now are both Course and Orbit Eject. I will explain 4.2 version here. Do this:

1. Show Course Program in the left MFD.
2. Ensure shared mode and show Orbit Eject in the right MFD.
3. Select Off-plane intercept program in the left. It prompts you for a target object.
4. Press TGT, type MARS, it will show you Mars transfer path. Src will be automatically set to Earth. This means, the
source orbit is the Earth's.
5. Available variables here are:
    -  TEj - setup time to eject in seconds (better leave here 0 for now)
    -  MJD - setup date to eject to Mars (play with this if you want to hit a node for saving fuel)
    -  TIn - time to insertion setup - how long you will travel to the target (determines eccentricity of your trajectory)
    -  MJD (another) - this is just reference for the previous value to check how long it will take in days.
6. Once you have done with the Course, move on to the right MFD.
7. By default, it's in Higher orbit mode, switch this to Course. Now you'll see you hypothetic transfer
trajectory in geocentric frame.
8. Click PRJ so that the word Self appears in the lower left corner - you are looking in the current orbit's plane
now.
9. Play with TEj (time to eject) and Tra (some sort of eject orientation) to meet the following conditions:
    -  Blue hypothetic trajectory is roughly plane-aligned with your current orbit, don't cross Earth's surface anywhere
(at least, in the ascending part)
    -  And your BT (burn time) is minimum.
10. Click MOD (in 4.0 and earlier) version or PG and then BV (in 4.2) to bring up the crosshairs.
11. TEj is the time to eject, when is counts down to five minutes, begin mavoeuvering crosshairs in the center (or just
hit AB to enable Auto-burning). When alignment is okay, they turn grey.
12. When burn time comes, engage main thrusters and watch BT counting down, steering crosshairs in the center at
the same time (if you didn't do autoburn).
13. With 5 seconds of burning left i usually desrease throttle, because crosshairs become very sensitive. Do you final
adjustments with the RSCs.

Congratulations, you are going to Mars!

canadave wrote:
And what's that Plane Change function I see in the Orbital menu, with the crosshairs?  It's not in the documentation
as far as I can see.  I'm basically completely stumped.

It's like plane alignment MFD, but has one big advantage: your burn moment is calculated precisely using integration.
Just hit TGT, enter your orbital target there. Then wait for the Tb to drop down to 0, align with crosshairs (or engade
normal or anti-normal autopilot) and do your burn until BT decreases to 0. 0.000 precision available!

[canadave]

Hey there Tiger (wow...THAT sounds weird coming from a guy to--presumably--a guy),

Thanks a lot!!  That clears up a bunch of questions I had.  I knew what the TEj and MJD acronyms stood for, and I
knew about how Shared mode shares the data between the MFD's, and I knew which "programs" in iMFD were
available, but I had no idea which programs to switch to and how to get them to work together to get out of LEO
toward a target.  

I haven't had a chance to try your procedure yet, but I'll give it a go a little later when I get a block of free time.  From
reading it, it sounds a lot clearer than the manual/tutorials, so I suspect I'll be successful on this go-round.

Thanks again!
Dave

[SiberianTiger]

canadave wrote:
Hey there Tiger (wow...THAT sounds weird coming from a guy to--presumably--a guy),

Excuse me, weird WHAT? That I'm a guy?

canadave wrote:
I haven't had a chance to try your procedure yet, but I'll give it a go a little later when I get a block of free time.  From
reading it, it sounds a lot clearer than the manual/tutorials, so I suspect I'll be successful on this go-round.

I don't regard myself an IMFD expert, I even didn't use all its capabilities to the full extent yet. But I just have a habit
of using it on every occassion and I think it's well suited for routine navigation. I haven't told you about the map
(which is a numerical predictor in fact), mid-course corrections, planet approaches and syncing... So, if you feel like,
you can always contact me - see my profile for info. I'll be happy to respond.

[canadave]

Excuse me, weird WHAT? That I'm a guy?

Maybe this is a cultural thing (I don't know where you're from), but where I come from, one guy saying "hey there,
tiger" to another guy would be considered a sexual invitation

Getting back to iMFD...I tried your suggestions and it worked a *lot* better this time around...thanks.  I still found
myself well short of Mars though.  Now, I didn't do any mid-course corrections, and I was definitely headed in the
correct general direction, so I'm happy with that....my only question is, does extreme 100000x time acceleration
throw iMFD off significantly?  I wasn't sure if I needed to be going at a slower time acceleration rate.

Cheers,
Dave

[SiberianTiger]

canadave wrote:
Maybe this is a cultural thing (I don't know where you're from),

From Siberia, of course. That's somewhere between Atlantic and Pacific. And you?

canadave wrote:
but where I come from, one guy saying "hey there,
tiger" to another guy would be considered a sexual invitation

Wow, really? TIGER as a symbol of sexuality? Oh, I'm proud...
(just skip the homosexual implication )

canadave wrote:
Getting back to iMFD...I tried your suggestions and it worked a *lot* better this time around...thanks.  I still found
myself well short of Mars though.  Now, I didn't do any mid-course corrections, and I was definitely headed in the
correct general direction, so I'm happy with that....my only question is, does extreme 100000x time acceleration
throw iMFD off significantly?  I wasn't sure if I needed to be going at a slower time acceleration rate.

I don't think any time acceleration may influence IMFD, since you only do course setup burns with it. The rest is done
by sir Isaac Newton with a little help of Dr. Martin Schweiger. There are two possible causes for your problem.
Firtsly, your ejection burn might not be perfect, so overshooting several billion kilometers at the finish is quite possible
if, say, you skipped RSC correction. Second cause is that IMFD course program solves just a pure three-body problem
in analytic way, it does not count influence of Moon, Jupiter and other minor bodies, which may distort your way
significantly.

Either way, there is a solution. This is Map mode, which incorporates numerical predictor. It's best used to estimate
your periapsis distance when you are already under way. To use it properly, select reference body, and target. You'll
see Mars orbit highlighted. Then click CNT button and input "p-Mars". This will centre you viewing over the PERIAPSIS
(or the closest passage) point on your trajectory. Note the PeD value and switch PRJ modes to observe what your
Martian passage looks like.

If you are not happy with it, do a mid-course correction. It's just like ejection burn you did, but with two differences:
first, you work solely with Off-plane intercept program, where you should select your ship as SRC and setup
MJD of arrival as close as that you've used for ejection; second, you do your burn right off this screen, by switching to
BV mode.

Now look at the map again... There's good change you'll see your predicted trajectory curving around future position
of Mars.

[canadave]

Yeah, that's what I figured.  Perfect....I have a much better idea of what to do now, thanks very much.  Gee....I was
playing around with that Map mode last night a bit....that alone is worth the price of admission  I see jarmo is
planning a 3D OpenGL version of it....I can't even begin to imagine how cool THAT is going to be.

Thanks again,
Dave

[AndyMc]

Hi,

This quick Imfd tutorial was posted on M6 a few days ago and it workd a treat. I was in the same situation as you a few days
ago and am now using it to go to Mars and the Moon. Give it a go - thats if you haven't already tried it.

http://orbit.m6.net/v2/read.asp?id=26176

Cheers,

Andy

[Me]

I have had problems using imfd in the latest version of orbiter. Help Please

[canadave]

Thanks, Andy, I'll go have a look.  Already, with SiberianTiger's help, I've done a successful trip to Mars, and to
Uranus (boy, THAT took a while!).  But I'm intrigued enough with iMFD now to really try to sit down and learn it, so
any tutorials I can lay my hands on will be a great help.

Cheers,
Dave

[StarLost]

A suggestion on the M6 forums was to take a look at what they're doing on the French Forum here. It appears that the
Europeans are using IMFD more than TransX (strange, afterall duncan is a European, too) and have developed a series of very
good tutorials with exercise scenarios. M. Garibaldi gave this link:

http://orbiter.dansteph.com/forum/index.php?topic=28.msg217#msg217

You might need to pass it through a translator. Use  this one:

http://www.freetranslation.com/

I find it better than BabelFish when I need it.

And hey, SiberianTiger, Siberia is a very big place. I'm sure most of us know where Irkutsk and Lake Baykal are. Where's home
for you (and have you placed it on the Obinauts Map, yet?). Siberia, Canada ... just like neighbours, eh? Same seasons, lots
of forest and lakes, beautiful women wrapped in parkas six months of the year ...

The tiger analogy: a male tiger is big, powerful cat, and covers his female like a hawk mantles his, doesn't give a damn
about his female's responses. Growls a lot. Unfortunately the real tiger only lasts about 30 secs. in the clinch but is ready
to repeat in about five minutes, repeating the cycle over about two hours (hmmm.... they must all be teenagers). Many women use the term as a sexual, teasing endearment.

But for a guy to call another guy tiger (other than on the golf course), well ... make sure he only puts ONE hand on your
shoulder when doing a prostate check.

(there's a great story here from my military days .... if you want me to share ...)



Post Edited ( 08-29-05 04:31 )

[SiberianTiger]

StarLost wrote:
And hey, SiberianTiger, Siberia is a very big place. I'm sure most of us know where Irkutsk and Lake Baykal are.
Where's home
for you (and have you placed it on the Obinauts Map, yet?). Siberia, Canada ... just like neighbours, eh? Same
seasons, lots
of forest and lakes, beautiful women wrapped in parkas six months of the year ...

That "hey" interjection will be my permanent attribute from now and on?..

Currently, I live in Barnaul (53°22' North, 83°45' East), on the Ob' river, poputaion is about 600k people I have it
marked on the Orbinaults map, in Asia. To be honest, I don't have much rights to call myself a Siberian Tiger,
because I originate from Volgograd (a city more widely known by its former name Stalingrad), but heck, there are
tigers in far eastern Siberia, and I like how it sounds.

StarLost wrote:
The tiger analogy: a male tiger is big, powerful cat, and covers his female like a hawk mantles his, doesn't give a damn
about his female's responses. Growls a lot. Unfortunately the real tiger only lasts about 30 secs. in the clinch but is
ready
to repeat in about five minutes, repeating the cycle over about two hours (hmmm.... they must all be teenagers).
Many women use the term as a sexual, teasing endearment.

But for a guy to call another guy tiger (other than on the golf course), well ... make sure he only puts ONE hand on
your
shoulder when doing a prostate check.

(there's a great story here from my military days .... if you want me to share ...)

Growling is fine, being big, furry and ready cover a female, eat a lot and sleep a lot is fine too. The rest is not
obligatory, I suppose.

So what's about your military days?

[StarLost]

Ooookkkayy. Ladies please depart for this one. It is waaaayyyy off-topic.

As with most military people, we had to have a mandatory medical checkup each year. All you males know what this means. One
of my friends was scheduled for his annual. The medical officer was doing a most thorough checkup. As the medical officer was
performing a prostate check (rubber glove, lubricating jelly, now cough) he had one hand on my friend's shoulder and his
other hand was performing the prostate examination. Another friend of ours, a medical technician had come in at the same
time, and being a bit of a comedian, laid his hand on my friend's other shoulder.

My buddy, being examined, feeling a hand on each shoulder, spun around so fast that he broke a finger on the hand of the
medical doctor.

For the rest of us, it was sooooo funny. Cost a couple of rounds at the wet mess for the medical officer, too. If I hadn't
have been there at the time, I would have been convinced it was a myth.

To this day, whenever I see the British actor Brian Blessed, performing as the King in Rowan Atkinson's BlackAdder, I am
reminded of the incident and always crack up.  For those not familiar with BlackAdder, the King always wore upper body
armour. His epaulets were a pair of gauntlets.

[SiberianTiger]