TransX Transx from parking orbit / ISS to Mars

[Mister Mxyzptlk]

Whew! I am so relieved you made it off plane. A two plane transfer is the best, I usually plan to have the node halfway there.

 

[cessnapilot]

Here is a screen shot using the excellent Videnie utility, of an offplane transfer to Mars from the stock DG in orbit scenario. As you can see it is way out of plane, about 6.5 degrees relative inclination, and I have marked the orbit intersection points. Is this what you are trying to do?

Cool. I use Videnie as well. :thumbup: Neat little utility.

And yes, that's what I'm wanting to do, and can do as long as I don't use outward or plane change velocity in Transx while in parking orbit around earth. When I do, Transx will often orient the little x in maneuver mode in a retrograde direction. As long as I leave plane change velocity and outward at 0 during that stage of planning, I'm ok. But, I have to replan later, usually when I leave earth's SOI, since the trajectory it is on is usually way off, at least from the standpoint of the "Encounter stage".

What I've decided best to do is escape, then plan, that way I don't have to do it twice.

 

[Mister Mxyzptlk]

At the risk of offending you I have to say that you don't know what you are doing then because the plan I used ONLY used prograde vel. and outward vel. to set up the trajectory you saw in the screenshot. I didn't use manuver mode, I used escape mode, so just what are you doing? Used properly transx should never indicate retrograde direction. You don't even use the bullseye view for the ejection. You just set it prograde in the standard DG auto pilot. Manuver mode is just confusing you, don't use it til you are more familiar with transx.

 

[cessnapilot]

Precisely... As long as you leave "plane change" alone during orbit, it works fine and dandy. But, add plane change and watch what happens. Sometimes it does and sometimes it doesn't go retrograde. But it never goes purely retrograde - Just enough to lower the orbit significantly enough to cause a crash. Additionally, it happens sometimes with an ISS intercept out of plane. Same thing happens often when you add "plane change" velocity. What it amounts to is transx is best used outside orbit, or like default Orbiter MFD functions, best used in-plane while in orbit. In that sense, transx is no more useful than TransferMFD as both will get you there easily. The only real benefit for transx over TransferMFD is the ability to do off-plane transfers well away from interfering gravitational forces, and to plan slingshots.

I'm not confused with maneuver mode. I was simply experimenting with it in order to achieve my goal, just as I experiment with other functions in Orbiter. Some work, some don't. Bullseye doesn't, but I was hoping I was doing something wrong rather than it being a limitation.

Outside my experiments, I am handling maneuver mode exactly as all the tutorials, the manual, and Flytandem's videos explain. I never, ever have a problem with it in sun orbit, or from the ground for that matter. The only time I ever have a problem with it is in orbit and it almost always comes from planning a plane change, and using the bullseye, of course. My hopes, when I started using transx, was that it could do the plane changes during ejection. But, as you stated, just set it in prograde with the autopilot - that, in itself, eliminates the need for transx until escape. I can do prograde ap without transx.

And, that's what I had deduced, that bullseye view is a waste of time in orbit, and therefore transx is NOT capable of off-plane transfers directly from orbit, at least not easily. I had hoped by this post that someone would tell me what I was doing wrong rather than confirming what I had already deduced: It's a waste of time. The off-plane transfer has to happen either at liftoff or after escape. Otherwise, the plane change will have to occur while in orbit before ejection, not during. Both you and Flytandem have confirmed this.

However, I had watched several tutorials centered around the "eject orientation" in transx, and thought that I might be able to use it to eject if already in parking orbit out of plane - another one of my experiments. However, this doesn't seem to be the case, as confirmed by Flytandem and yourself, and it is just best to initiate the plane change and use ejection orientation during launch, which is easy enough to do. And that was my primary issue. So, my suspicions are confirmed via this thread: A) tranx can't do off-plane transfers in every situation. B) Certain functions of transx can't or shouldn't be used in orbit.

Now one might ask why not just do this from launch? Simple. I'm using a spacecraft that is a deep space craft and not suitable for landing on the surface of planets. Therefore, the ability to do an off-plane transfer from orbit was enticing to me. However, through this thread and experimentation, I've learned that Transx is not the solution, and it may be impracticable to do any way.

So, I'm back to square one. Eject from orbit, then plan. Otherwise, I'm wasting time.

 

[flytandem]

I'm so confused.

---------- Post added at 12:38 PM ---------- Previous post was at 12:29 PM ----------

don't confuse inefficiency with impossibility. transx can be used to plan any direction and strength of speed change at any time, including doing plane changes. if you wish to combine a plane change into an eject burn as a single burn that's fine, you are best to do it by means of a maneuver, not as a plan because the plan only tells you that you are out of plane and requires you to fix that first. not sure what you mean by target not working. it is always used in maneuver and never used outside of maneuver.

 

[cessnapilot]

I'm so confused.

---------- Post added at 12:38 PM ---------- Previous post was at 12:29 PM ----------

don't confuse inefficiency with impossibility. transx can be used to plan any direction and strength of speed change at any time, including doing plane changes. if you wish to combine a plane change into an eject burn as a single burn that's fine, you are best to do it by means of a maneuver, not as a plan because the plan only tells you that you are out of plane and requires you to fix that first. not sure what you mean by target not working. it is always used in maneuver and never used outside of maneuver.

Right. Which is what I found. A plane change in orbit is best done first, before planning. I can plan the plane changes no problem. But, in orbit, if I try to plan via transx while in orbit, then the maneuver mode many times will put point the bullseye down into the surface or into a retrograde direction. That usually happens when I try to add plane change velocity as part of the plan. I'm hoping I'm just doing something wrong, but I am experimenting here.

I tend to agree with Mr Mxyzptlk that the maneuver mode bullseye view shouldn't be used during ejection. It was a fun experiment, to say the least, as was trying to use the ejection orientation out of plane while in orbit. Not necessarily impossible, but as you said, inefficient, and in my opinion, a royal pain in the rear.

The bullseye, however, does work like a charm as long as I don't do it in orbit. Maybe I'm just adding too much plane change velocity, whereby Tranx wants to do the plane change by a retrograde burn, flipping the orbit. I played with this some around the sun, retrograding until the orbit flipped. (unlimited fuel on, of course) Retrograde then becomes prograde and your new orbit is 180 degrees opposite your old orbit, reversing your direction.

I love experimenting with Orbiter, trying new things, and using utilities to perform tasks they weren't necessarily intended to do. It's part of what makes it fun.

 

[dgatsoulis]

@cessnapilot and @Mister Mxyzptlk;

When you want to make interplanetary voyages, try not to just "picture" your orbit in relation to the Earth... try to picture it, in relation to the Sun.

As far as the Earth is concerned, you're going around it in a nice circular/elliptical orbit.

But, from the Sun's perspective, you're look like you're making S-turns! As you orbit the Earth; Earth moves in the prograde direction, relative to the Sun. So you're constantly moving "ahead" and your orientation-relative to the Sun- is constantly changing.
(hope this crude illustration helps)

I understand that picturing it in 4D (3D+time) is difficult... but if you manage to do it, the whole solar system and the orbital mechanics that govern it, will "open-up" like a flower for you.

I'm currently working on an illustrated pamplet, that shows these things in 3D+time.
I know, that different minds think in different ways, (this next vid shows an excellent example):

[ame="http://www.youtube.com/watch?v=Cj4y0EUlU-Y&feature=related"]YouTube - Feynman 'Fun to Imagine' 11: Ways of Thinking (Part One of Two)[/ame]


But i hope to be able- at least - to share with you, what goes on on my mind, when i'm thinking of orbits, and what can be done with them.

Have fun, happy orbiting!

 

[flytandem]

Right. Which is what I found. A plane change in orbit is best done first, before planning. I can plan the plane changes no problem. But, in orbit, if I try to plan via transx while in orbit, then the maneuver mode many times will put point the bullseye down into the surface or into a retrograde direction.

I wonder if you are doing the maneuver at the correct time (date). Please do something like what you describe and make a save and post the scenario.

That usually happens when I try to add plane change velocity as part of the plan. I'm hoping I'm just doing something wrong, but I am experimenting here.

see above

I tend to agree with Mr Mxyzptlk that the maneuver mode bullseye view shouldn't be used during ejection. It was a fun experiment, to say the least, as was trying to use the ejection orientation out of plane while in orbit. Not necessarily impossible, but as you said, inefficient, and in my opinion, a royal pain in the rear.

when leaving Earth I almost always use the plan just to get a proper parking orbit and date of ejection burn plus estimated burn amount. Then I set up a maneuver using the information from then Plan and then kill the plan with eject done via the maneuver and target.

The bullseye, however, does work like a charm as long as I don't do it in orbit.

has worked like a charm in something like 5000 out of the last 5000 times I've used it

Maybe I'm just adding too much plane change velocity, whereby Tranx wants to do the plane change by a retrograde burn, flipping the orbit.

another case of me wanting to see a scenario

I played with this some around the sun, retrograding until the orbit flipped. (unlimited fuel on, of course) Retrograde then becomes prograde and your new orbit is 180 degrees opposite your old orbit, reversing your direction.

I love experimenting with Orbiter, trying new things, and using utilities to perform tasks they weren't necessarily intended to do. It's part of what makes it fun.

 

[cessnapilot]

Hmmm... Funny, I had always pictured figure 8's when thinking about an orbital path along the sun. Again, thinking of things in different ways. Great video.

I love mind challenges... Ever tried to figure out a tesseract in your head? That'll keep you awake for hours.

---------- Post added at 10:38 PM ---------- Previous post was at 10:23 PM ----------

I wonder if you are doing the maneuver at the correct time (date). Please do something like what you describe and make a save and post the scenario.
see abovewhen leaving Earth I almost always use the plan just to get a proper parking orbit and date of ejection burn plus estimated burn amount. Then I set up a maneuver using the information from then Plan and then kill the plan with eject done via the maneuver and target.has worked like a charm in something like 5000 out of the last 5000 times I've used itanother case of me wanting to see a scenario

Hmmmm.... The right time. Now that is a very good possibility. I never really think about what "time" to eject other than the timer countdown based on the date I enter in transx. I will set one up tonight and post a screenshot plus the parameters I use for planning.

I'm thinking that maybe I'm doing something wrong with plane change, or the wrong time or a combination of both. I mean, if you've done it numerous times, then it is possible. And, even though transx shows me encountering the planet within say a few hundred thousand kilometers, I may be over adjusting something during planning that sets me into a retrograde direction. Oh, and it's not ever exactly retrograde. For example, it may want me to rotate 120 degrees left of prograde.

And, when I launch, I will use the plan, or at least MapMFD or LaunchMFD to get a proper parking orbit as well. It's just starting from orbit that has me baffled, when the ejection orientation won't line up, or when Transx wants to send me into the side of the planet.

 

[dgatsoulis]

Ever tried to figure out a tesseract in your head? That'll keep you awake for hours.

You mean something like this?

 

[cessnapilot]

You mean something like this? YouTube - TESARACT 12 09 2009

Yup... That's it... Before the days of Google, though, you were on your on. But it's still hard to think about it in the 4th dimension.

 

[cessnapilot]

I wonder if you are doing the maneuver at the correct time (date). Please do something like what you describe and make a save and post the scenario.

Ok, here it is. I think I see what's wrong. It's the negative plane change, which would certainly flip the orbit as I explained earlier. When planning, I usually add a small amount of prograde first, then I adjust plane change to move closer to the yellow lines, then I move on to date and outward velocity to get everything lined up to the plane change. I'm beginning to see this isn't such a good idea and transx doesn't take the planet into account. I've attached the screenshot where you can clearly see the retrograde direction transx puts this in, and you see also that I have a good fairly close encounter with Mars with this setup.



Here, notice the that the maneuver mode target is centered, but my orientation is nearly all retrograde. I've never had it that close. Usually, it orients me around 300 degrees or so. In this case, I'm at 191. And crap...It's never suggested that much DV. :rofl: Most of the time, it's between 7k and 10k.

Here are the settings for this scenario.

DGIV in Orbit Scenario

Transx parameters
Eject date: 52020.8928
Prograde: 1,405
Outward: 806.8
Plane Change: -8,815

 

[orbekler]

Not necessarily impossible, but as you said, inefficient, and in my opinion, a royal pain in the rear.

I don't know about inefficiency, but I actually found really difficult to keep centered the cross of the burn. Using the standard prograde autopilot, the cross was not centered, revealing that Trans-X was using an additional inward component, maybe due to sun gravity calculation. However the autopilot worked the same (just for moon, I dunno about other planets, I'm a beginner).:lol:

And for the tesseract... Gosh, that is just a 3D projection (or shadow) of a 4D cube, we can't really see the hypercube, but I would really like...:facepalm:

 

[cessnapilot]

I don't know about inefficiency, but I actually found really difficult to keep centered the cross of the burn. Using the standard prograde autopilot, the cross was not centered, revealing that Trans-X was using an additional inward component, maybe due to sun gravity calculation. However the autopilot worked the same (just for moon, I dunno about other planets, I'm a beginner).:lol:

And for the tesseract... Gosh, that is just a 3D projection (or shadow) of a 4D cube, we can't really see the hypercube, but I would really like...:facepalm:

I too have noticed that the crosshairs are never centered even when burning purely prograde.

As for the tesseract, it caused me many sleepless nights. And still does when I revisit it. :facepalm:

---------- Post added at 01:07 AM ---------- Previous post was at 01:01 AM ----------

And crap...It's never suggested that much DV. :rofl: Most of the time, it's between 7k and 10k.5

FlyTandem,

I just realized why the DV was so high. I inadvertently plugged the Encounter DV from stage 2 into stage 1 during the maneuver portion. :facepalm:

In some of your videos, you set up the plan in stage 2, then you look at the Delta V in stage 1. Then you enable maneuver mode in stage one and plug that number in, which is what I do. I also set the date in the stage 1 maneuver to match that of the date in the stage 2 plan. Should I also enter the values for outward velocity and plane change, or am I correct in assuming that the DV calculation read from stage 1 after planning accounts for that? That number is different than the number in the stage 2 plan, so that's why I'm assuming it does account for it.

 

[flytandem]

I too have noticed that the crosshairs are never centered even when burning purely prograde.

As for the tesseract, it caused me many sleepless nights. And still does when I revisit it. :facepalm:

---------- Post added at 01:07 AM ---------- Previous post was at 01:01 AM ----------



FlyTandem,

I just realized why the DV was so high. I inadvertently plugged the Encounter DV from stage 2 into stage 1 during the maneuver portion. :facepalm:

In some of your videos, you set up the plan in stage 2, then you look at the Delta V in stage 1. Then you enable maneuver mode in stage one and plug that number in, which is what I do. I also set the date in the stage 1 maneuver to match that of the date in the stage 2 plan. Should I also enter the values for outward velocity and plane change, or am I correct in assuming that the DV calculation read from stage 1 after planning accounts for that? That number is different than the number in the stage 2 plan, so that's why I'm assuming it does account for it.

I was thinking that we are 2 blind men in a dark room. You can't find the door and I can't find you to show you the door. Now I have a glimmer of light.

You said you set the date of the maneuver as being the date from the stage 2 plan. There's the problem.

The plan is very rough when it comes to date. Let's say you have a plan and you get into a nice parking orbit, nicely aligned with the plan. The problem is that as you are doing your orbits you will surely find that yhou are part way around an orbit at the exact time of the planned departure date. This is a reason to set up a maneuver instead of trusting the plan. Especially if the plan is date sensitive. Sometimes they are not too bad to be 45 minutes early or late. But to set up a maneuver then use the date of the plan shows you don't understand the importance of the precision of the maneuver with respect to date.

Here's what you need to do....
As you said you do,... grab the required deltav from Stage 1 for the stage 1 maneuver that you are turning on. Make sure you are aligned well (within .1 degrees of the plan). When you turn on the maneuver and add the required prograde you will now see 2 separate dashed yellow trajectories. One of them is for your plan from stage 2 and the other is for the maneuver you have just set up. Now for date swing the date forward and you'll see the yellow dashed yellow line start rotating around the Earth. Adjust the date forward until it lays perfectly on top of the other yellow dashed line. Use hyper and do short clicks of the mouse to be precise. Then go to stage 2 and make all the velocity values of your plan = zero. When the last velocity value is reset to zero the stage 1 will only show the maneuver trajectory and stage 2 and 3 will now be showing what the maneuver will cause if burned as planned. Now tweak the velocity (prograde) and date (hyper with short clicks) to find the best solution for the trip you are making. The turn to face the x and burn.

In summary, I think you have 2 errors. 1 is using the date of the plan and not making the date according to what the maneuver will show, and the 2nd error is (just guessing since you aren't showing me a full scenario) that you are leaving the plan in place meaning that stage 3 is working from the plan not the maneuver.

---------- Post added at 08:04 PM ---------- Previous post was at 07:46 PM ----------

This is the part of the youtube tutorial that deals with the details explained above
Earth to Mars Part 3:

see from 40 seconds thru about 2:20.
:hello:

 

[orbekler]

Off-Topic:

As for the tesseract, it caused me many sleepless nights. And still does when I revisit it. :facepalm:

See this, maybe you'll sleep a bit better::lol:

 

[cessnapilot]

You can't find the door and I can't find you to show you the door.

Lol.. That reminds me of the Joe Walsch song, "Life's Been Good" - "I go to parties sometimes until 4. It's hard to leave when you can't find the door."

In summary, I think you have 2 errors. 1 is using the date of the plan and not making the date according to what the maneuver will show, and the 2nd error is (just guessing since you aren't showing me a full scenario) that you are leaving the plan in place meaning that stage 3 is working from the plan not the maneuver.

You are correct, sir, in both errors - guilty of both.

Make sure you are aligned well (within .1 degrees of the plan).

Are you talking about the eject orientation function here, or are you talking about a plane alignment burn first? If the former, that was the one we had such a tough time lining up because the planes wouldn't match. I think I got it within 8 degrees relative inclination once with the DG in Orbit scenario.

---------- Post added at 08:41 PM ---------- Previous post was at 08:37 PM ----------

Off-Topic:

See this, maybe you'll sleep a bit better::lol:

:speakcool:

Good video! Thanks... Problem is, once I figure that one in my head, something else will pop in to keep me awake - Such is the nature of the insatiable thirst for knowledge.

 

[Mister Mxyzptlk]

Flytandem, When I plug in the prograde Deltav quantity into the maneuver program, my hypothetical orbit comes up way short. It doesn't even leave Earth's SOI. What is up with that?

 

[cessnapilot]

Flytandem, When I plug in the prograde Deltav quantity into the maneuver program, my hypothetical orbit comes up way short. It doesn't even leave Earth's SOI. What is up with that?

Lol... That was one of the original problems I had, which prompted my first post in this thread. But, I'm trying to do it from existing orbit rather than launch. At launch, I have no problems with it based on the way he does it in his videos. Are you trying it from orbit too?

 

[flytandem]

Flytandem, When I plug in the prograde Deltav quantity into the maneuver program, my hypothetical orbit comes up way short. It doesn't even leave Earth's SOI. What is up with that?

show the scenario text and I'll take a look at what you have.