Question Trip to Venus - Page 2 - Orbiter-Forum

greyrogue715 · 05-30-2012, 10:03 AM

Here's my MFD procedure. It is from a tutorial that I am not sure who wrote it. I use IMFD 5.5

EJECTION:

LEFT MFD
Course >Target Intercept> Tgt=Venus

RIGHT MFD
Op Mode Share with '0' left MFD
Orbit Eject >Course>Proj=Self

LEFT MFD
Tgt Int >decrease Tin to minimize burn time in Orbit Eject

(Not sure, but I have been setting ejection time here. The tutorial doesn't clarify about this. I wait until I am at the noon position on the daylight side or slightly before and set the ejection time for about 450 seconds.

RIGHT MFD
Orbit Eject MOD>TEj to get blue line over green dotted line.

Set Autoburn

(Also, the MFD don't seem to be syncing up with each other. I notice contradictory burn times on the tgt int screen L mfd and the orbit eject page R mfd. I manually type in ejection time on the R MFD and hit enter when it matches the LEFT MFD.)

MID COURSE CORRECTION
LEFT MFD
TGT INT >Source enter 'X' for vessel

RIGHT MFD
MAP >Ref=SUN, Tgt=VENUS, Cnt=Sun, Sel >Dsp >PG >Soi >Int >Plan >PG .Sel to get PeRef Venus
Read PeT and Warp 1000X wait until 1/2 initial PeT and WARP 1X

LEFT MFD
AUTOBURN

It is at this point that I realize something is wrong. I haven't made it as far as planet approach yet. I got the PeA down to 200km last attempt setting the IMFD, but still missed by quite a ways upon actual attempt. I am going to try it again here shortly.

EDIT - I just tried again and I can't remember how I got the PeA down. Everything I try and it won't change. How is the PeA adjusted? I will search.

Thanks again.

**Goth** · 05-30-2012, 10:29 AM

Autoburn must be clicked on the Orbit eject program (right MFD).
Just in case.

Quote:

Tgt Int >decrease Tin to minimize burn time in Orbit Eject

Decreasing TIn the burn time increase, because if you want to arrive soon, you will need more speed.
TIn small => more speed required => more elliptic orbit => longer burn time
TIn big => less speed required => more circular orbit => less burn time => generally less fine approach;
As I said, the key is watching the PeA value.

greyrogue715 · 05-30-2012, 11:09 AM

Thanks Goth. I can't get the PeA down any less than about 600M. It flips immediately to -600M range. I also noticed I was getting a "no burn vector' message on the burn screen. I'm trying now to get a screenshot for you.

---------- Post added at 07:09 AM ---------- Previous post was at 06:54 AM ----------

A million questions...

Does the Left MFD have to also be set to shared with the right. I set the right for left, but do they both have to be set? And should the Tin be in the 22M range, because that is what I am getting. I tried once again and it gave me a Tej that occurred on the sunset side of the planet and it launched me out past the orbit of Mars.

**Goth** · 05-30-2012, 11:18 AM

Quote:

Originally Posted by greyrogue715

Does the Left MFD have to also be set to shared with the right. I set the right for left, but do they both have to be set?

No. Generally nothing bad happens if you set both, but the correct procedure is to set only one of them. Anyway, when in the orbit eject program, selecting Course, the graph actually appears, you know you did it right. Otherwise a yellow error message appears.

Quote:

Originally Posted by greyrogue715

And should the Tin be in the 22M range, because that is what I am getting.

Yes, sounds fine.

Instead of screenshots/scenarios, just tell us your scenario MJD date, so we can try the plan.

greyrogue715 · 05-30-2012, 12:03 PM

MJD 56578.3588

I start at sunrise using the Oct. 13 2013 window.

---------- Post added at 08:00 AM ---------- Previous post was at 07:26 AM ----------

It keeps pointing me straight at the Earth and burning me straight into it. I also am getting a 1300sec burn time again. I wish this could be more difficult.

---------- Post added at 08:03 AM ---------- Previous post was at 08:00 AM ----------

And do I just ignore Ejection time on the left MFD? It shows zero.

**Goth** · 05-30-2012, 12:12 PM

Quote:

Originally Posted by greyrogue715

It keeps pointing me straight at the Earth and burning me straight into it.

That's just because you have to wait a bit. The graph on Orbit eject shows you pretty well if you're going to hit the Earth or not (if you're in Self PRJ). If you are hitting it, just wait (time warping) and fire the autoburn again. If you're not sure when is the right moment, just point the nose in the direction told by the burn vector and time warp untill your nose point far enough from the Earth.

Quote:

Originally Posted by greyrogue715

And do I just ignore Ejection time on the left MFD? It shows zero.

Yes because you already are in the right launch window.

greyrogue715 · 05-30-2012, 12:15 PM

Another attempt. It seems to insist on ejecting me on the night side of the planet. It autoburns for about 10 seconds, changes attitude straight at Earth. And refires engines. Idk what's going on, but I thinking I may be better sticking with Earth orbit operations, which is getting boring after 5 years of attempted interplanetary flight.

**Goth** · 05-30-2012, 12:22 PM

I tried that date and I get weird results as well. I suppose we both have to wait an IMFD expert. ^^

greyrogue715 · 05-30-2012, 12:53 PM

I'll try what you said and also another date.

---------- Post added at 08:53 AM ---------- Previous post was at 08:28 AM ----------

Same result. I don;t know if there are IMFD experts on here. Maybe a few ten year olds. lol

**Ripley** · 05-30-2012, 01:25 PM

You are not in an external view while AB takes place, are you??

**Goth** · 05-30-2012, 01:54 PM

Ok the PeA was not the thing to watch out.
I've attached a scenario. You will reach Venus close enough and using no midcourse corrections.
I just incremented TIn a bit so that the trajectory became circular enough to save fuel.
Since you're already in a nice launch window there was nothing else to worry about.

Now the question is:
why IMFD shows that the PeA is 0.702AU when I actually encounter Venus at something like 500k and so my plan is actually good?

This is one thing I've never understood about the IMFD.
Especially since I'm used to the "Close approach" variable in TransX.

EDIT
Bad scenario. See the new one:
http://www.orbiter-forum.com/showthr...8&postcount=37

greyrogue715 · 05-30-2012, 04:25 PM

I made it at least to the orbit of Venus. I applied MCCs and then shot in front of Venus and ended up with a PeA back in the Ms. I kept trying autoburn to correct and it made it worse. I'll make attempt number 904 sometime today and not make any corrections until Planet Approach.

I did notice a major thing with your scenario that obviously is a problem. When I switched to burn view, both MFDs changed to burn view. I wasn't getting that before. Like I said, I don't think the two are syncing up for some reason.

Linguofreak · 05-30-2012, 05:42 PM

Quote:

Originally Posted by Goth

Now the question is:
why IMFD shows that the PeA is 0.702AU when I actually encounter Venus at something like 500k and so my plan is actually good?

I'm thinking it's probably a Sun-relative PeA. Venus is 0.72 AU from the Sun.

**Goth** · 05-30-2012, 07:00 PM

Yeah that's why.

@greyrogue715
For the midcourse corrections you have to be sure you still have the same plan open in the IMFD, and then change the source. If for some reason you lost it, you have to target again Venus and manually adjust TIn to save dV (the starting plan will be too fuel expensive).

Quote:

Originally Posted by greyrogue715

When I switched to burn view, both MFDs changed to burn view.

Doesn't happen to me.

In my scenario they are connected, if for any reason they aren't when you run it, just manually share one of them.
If you meant it happens in your scenario, then yes, you have not correctly shared them. Go to the Menu with both and see what's written in OpMode.

greyrogue715 · 05-30-2012, 08:38 PM

Yeah, your scenario they were connected, mine no. OK I will do so.

---------- Post added at 04:38 PM ---------- Previous post was at 04:26 PM ----------

Well I managed to screw up the scenario you sent me. I load it now and go to the burn view page and it tells me 'no burn vector'. I wanted to send the scenario back to you to see if you can see what I did to it, but I don't see any 'attach file' button here.

05-30-2012, 10:03 AM	#16
greyrogue715 Orbinaut	Here's my MFD procedure. It is from a tutorial that I am not sure who wrote it. I use IMFD 5.5 EJECTION: LEFT MFD Course >Target Intercept> Tgt=Venus RIGHT MFD Op Mode Share with '0' left MFD Orbit Eject >Course>Proj=Self LEFT MFD Tgt Int >decrease Tin to minimize burn time in Orbit Eject (Not sure, but I have been setting ejection time here. The tutorial doesn't clarify about this. I wait until I am at the noon position on the daylight side or slightly before and set the ejection time for about 450 seconds. RIGHT MFD Orbit Eject MOD>TEj to get blue line over green dotted line. Set Autoburn (Also, the MFD don't seem to be syncing up with each other. I notice contradictory burn times on the tgt int screen L mfd and the orbit eject page R mfd. I manually type in ejection time on the R MFD and hit enter when it matches the LEFT MFD.) MID COURSE CORRECTION LEFT MFD TGT INT >Source enter 'X' for vessel RIGHT MFD MAP >Ref=SUN, Tgt=VENUS, Cnt=Sun, Sel >Dsp >PG >Soi >Int >Plan >PG .Sel to get PeRef Venus Read PeT and Warp 1000X wait until 1/2 initial PeT and WARP 1X LEFT MFD AUTOBURN It is at this point that I realize something is wrong. I haven't made it as far as planet approach yet. I got the PeA down to 200km last attempt setting the IMFD, but still missed by quite a ways upon actual attempt. I am going to try it again here shortly. EDIT - I just tried again and I can't remember how I got the PeA down. Everything I try and it won't change. How is the PeA adjusted? I will search. Thanks again. Last edited by greyrogue715; 05-30-2012 at 10:28 AM.

05-30-2012, 01:54 PM	#26
Goth Occasional orbinaut	Ok the PeA was not the thing to watch out. I've attached a scenario. You will reach Venus close enough and using no midcourse corrections. I just incremented TIn a bit so that the trajectory became circular enough to save fuel. Since you're already in a nice launch window there was nothing else to worry about. Now the question is: why IMFD shows that the PeA is 0.702AU when I actually encounter Venus at something like 500k and so my plan is actually good? This is one thing I've never understood about the IMFD. Especially since I'm used to the "Close approach" variable in TransX. EDIT Bad scenario. See the new one: http://www.orbiter-forum.com/showthr...8&postcount=37 Last edited by Goth; 06-01-2012 at 11:57 AM.

05-30-2012, 07:00 PM	#29
Goth Occasional orbinaut	Yeah that's why. @greyrogue715 For the midcourse corrections you have to be sure you still have the same plan open in the IMFD, and then change the source. If for some reason you lost it, you have to target again Venus and manually adjust TIn to save dV (the starting plan will be too fuel expensive). Quote: Originally Posted by greyrogue715 When I switched to burn view, both MFDs changed to burn view. Doesn't happen to me. In my scenario they are connected, if for any reason they aren't when you run it, just manually share one of them. If you meant it happens in your scenario, then yes, you have not correctly shared them. Go to the Menu with both and see what's written in OpMode. Last edited by Goth; 05-30-2012 at 07:03 PM.

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05-30-2012, 10:29 AM	#17
Goth Occasional orbinaut	Autoburn must be clicked on the Orbit eject program (right MFD). Just in case. Quote: Tgt Int >decrease Tin to minimize burn time in Orbit Eject Decreasing TIn the burn time increase, because if you want to arrive soon, you will need more speed. TIn small => more speed required => more elliptic orbit => longer burn time TIn big => less speed required => more circular orbit => less burn time => generally less fine approach; As I said, the key is watching the PeA value.

05-30-2012, 11:09 AM	#18
greyrogue715 Orbinaut	Thanks Goth. I can't get the PeA down any less than about 600M. It flips immediately to -600M range. I also noticed I was getting a "no burn vector' message on the burn screen. I'm trying now to get a screenshot for you. ---------- Post added at 07:09 AM ---------- Previous post was at 06:54 AM ---------- A million questions... Does the Left MFD have to also be set to shared with the right. I set the right for left, but do they both have to be set? And should the Tin be in the 22M range, because that is what I am getting. I tried once again and it gave me a Tej that occurred on the sunset side of the planet and it launched me out past the orbit of Mars.

05-30-2012, 11:18 AM	#19
Goth Occasional orbinaut	Quote: Originally Posted by greyrogue715 Does the Left MFD have to also be set to shared with the right. I set the right for left, but do they both have to be set? No. Generally nothing bad happens if you set both, but the correct procedure is to set only one of them. Anyway, when in the orbit eject program, selecting Course, the graph actually appears, you know you did it right. Otherwise a yellow error message appears. Quote: Originally Posted by greyrogue715 And should the Tin be in the 22M range, because that is what I am getting. Yes, sounds fine. Instead of screenshots/scenarios, just tell us your scenario MJD date, so we can try the plan.

05-30-2012, 12:03 PM	#20
greyrogue715 Orbinaut	MJD 56578.3588 I start at sunrise using the Oct. 13 2013 window. ---------- Post added at 08:00 AM ---------- Previous post was at 07:26 AM ---------- It keeps pointing me straight at the Earth and burning me straight into it. I also am getting a 1300sec burn time again. I wish this could be more difficult. ---------- Post added at 08:03 AM ---------- Previous post was at 08:00 AM ---------- And do I just ignore Ejection time on the left MFD? It shows zero.

05-30-2012, 12:12 PM	#21
Goth Occasional orbinaut	Quote: Originally Posted by greyrogue715 It keeps pointing me straight at the Earth and burning me straight into it. That's just because you have to wait a bit. The graph on Orbit eject shows you pretty well if you're going to hit the Earth or not (if you're in Self PRJ). If you are hitting it, just wait (time warping) and fire the autoburn again. If you're not sure when is the right moment, just point the nose in the direction told by the burn vector and time warp untill your nose point far enough from the Earth. Quote: Originally Posted by greyrogue715 And do I just ignore Ejection time on the left MFD? It shows zero. Yes because you already are in the right launch window.

05-30-2012, 12:15 PM	#22
greyrogue715 Orbinaut	Another attempt. It seems to insist on ejecting me on the night side of the planet. It autoburns for about 10 seconds, changes attitude straight at Earth. And refires engines. Idk what's going on, but I thinking I may be better sticking with Earth orbit operations, which is getting boring after 5 years of attempted interplanetary flight.

05-30-2012, 12:22 PM	#23
Goth Occasional orbinaut	I tried that date and I get weird results as well. I suppose we both have to wait an IMFD expert. ^^

05-30-2012, 12:53 PM	#24
greyrogue715 Orbinaut	I'll try what you said and also another date. ---------- Post added at 08:53 AM ---------- Previous post was at 08:28 AM ---------- Same result. I don;t know if there are IMFD experts on here. Maybe a few ten year olds. lol

05-30-2012, 01:25 PM	#25
Ripley Tutorial translator	You are not in an external view while AB takes place, are you??

05-30-2012, 04:25 PM	#27
greyrogue715 Orbinaut	I made it at least to the orbit of Venus. I applied MCCs and then shot in front of Venus and ended up with a PeA back in the Ms. I kept trying autoburn to correct and it made it worse. I'll make attempt number 904 sometime today and not make any corrections until Planet Approach. I did notice a major thing with your scenario that obviously is a problem. When I switched to burn view, both MFDs changed to burn view. I wasn't getting that before. Like I said, I don't think the two are syncing up for some reason.

05-30-2012, 05:42 PM	#28
Linguofreak Orbinaut	Quote: Originally Posted by Goth Now the question is: why IMFD shows that the PeA is 0.702AU when I actually encounter Venus at something like 500k and so my plan is actually good? I'm thinking it's probably a Sun-relative PeA. Venus is 0.72 AU from the Sun.

05-30-2012, 08:38 PM	#30
greyrogue715 Orbinaut	Yeah, your scenario they were connected, mine no. OK I will do so. ---------- Post added at 04:38 PM ---------- Previous post was at 04:26 PM ---------- Well I managed to screw up the scenario you sent me. I load it now and go to the burn view page and it tells me 'no burn vector'. I wanted to send the scenario back to you to see if you can see what I did to it, but I don't see any 'attach file' button here.