IMFD From Europa to Earth

Max Pain

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Hello,

I have my spaceship landed on Europa, now I want to fly to Earth using IMFD 5.5.

The problem is, that for the Target Intercept program the source Body is Jupiter. When I do the Orbit Eject program, I eject from Europa. Therefore, I am still in Jupiters gravity and Orbit Eject doesn't work. Setting the reference in Orbit Eject to Jupiter is also not the best idea because of the gravitational influence of Europa.

I know that a hackish would be to simply get first in Jupiter orbit and then eject, but I would prefer to eject with only one burn from Europa. I'm playing with the thought that maybe the Slingshot program provides an solution? And I want to do this with IMFD, I know that Transx is better suited for this task.

Thanks and Regards,

Georg
 

dgatsoulis

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I would prefer to eject with only one burn from Europa. I'm playing with the thought that maybe the Slingshot program provides an solution? And I want to do this with IMFD, I know that Transx is better suited for this task.

Thanks and Regards,

Georg
You are right to think that the slingshot program is the solution. I recorded a quick video showing you how to do it, but my mic was on "mute" :facepalm: (Not the first time this happens).

Still you will be able to see the setup. Try it and come back with any questions you might have.


Perform the first correction when you are outside of Jupiter's SOI.
 
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statickid

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I would also use TransX, but I never use the other mfd's mentioned, so I can't say if one works better than the other
 

dgatsoulis

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For a direct "landed on moon of a planet to another planet" journey, IMFD provides a solution without the need for surrogate ships.

You can do it with TransX, but you need either a surrogate ship already in orbit around the moon or two separate instances of TransX.

I always have this setup on my Orbiter installation, so I can choose which one suits me best.

A combination of TransX for the intial setup and then IMFD's Delta Velocity and Map programs provide the best results for almost any situation in Orbiter.
 

Max Pain

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Thanks a lot for your support :thumbup:! Tried it now and it spared me a lot of fuel. I see that it is not as exact as a direct ejection (when Jupiters gravitational influence was zero, I had to do a correction burn with a dV of 500 m/s), but for now I am happy.

Regards
Georg
 

statickid

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Here's a TransX plan from LEO (Low Europa Orbit) that has a pretty good Earth Encounter for about 5.9kDV. In practice I'd make this burn then just make a course correction once I got out of Jupiter's area.

---------- Post added at 12:53 PM ---------- Previous post was at 12:50 PM ----------

I don't know what people use surrogate ships for. I've heard of people using them, but never figured out exactly why. It is required to start from a moon surface? :hmm:
 

dgatsoulis

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You cannot setup a TransX plan from a moon to another planet without already being in orbit first. So you either need a surrogate ship or two separate instances of TransX to do it.

1.Surrogate ship method:
You place one ship in orbit around the moon you are landed and use it to setup the plan. Then you go to the landed ship and launch to be in plane with the surrogate. Once in orbit, you inherit the plan from the surrogate and continue with the rest of the flight normally.

2. Using two instances of TransX:
You start the plan from stage3 where you have to use the Cruise Plan: Eject. Then you go to stage2 and setup the Initial plan: Escape.
Now you need the second TransX- stage1 escape , stage2 Plan: None
You match the trajectory of stage2 of the first TransX and now you have a launch heading in stage1 of the second TransX. (Confused yet?)
After you get in orbit, you can close the second TransX and continue as usual with the first one.
 

Cras

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or, use IMFD.


Sorry for sounding like a broken record, but I really like IMFD. It is a wonderful tool.
 
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dgatsoulis

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or, use IMFD.


Sorry for sounding like a broken record, but I really like IMFD. It is a wonderful tool.
I like it too, it's great.
But i think it's always good to know at least two ways to solve a problem.

For example: how about a trip from Brighton beach to Olympus base, using minimum ΔV?
IMFD can provide a solution but it uses too much fuel. In this case TransX gives better results.
Or even better, use TransX for the initial setup, perform the burns and know when and where you are going to arrive with IMFD. ;)

EDIT:
In the example above, I'm talking about a solution that utilizes the Oberth effect.
 
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Cras

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That is a good point, and one I have often thought about. I do need to learn TransX a bit better and just use IMFDs dV program for the burns.
 

statickid

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You cannot setup a TransX plan from a moon to another planet without already being in orbit first. So you either need a surrogate ship or two separate instances of TransX to do it.

1.Surrogate ship method:
You place one ship in orbit around the moon you are landed and use it to setup the plan. Then you go to the landed ship and launch to be in plane with the surrogate. Once in orbit, you inherit the plan from the surrogate and continue with the rest of the flight normally.

2. Using two instances of TransX:
You start the plan from stage3 where you have to use the Cruise Plan: Eject. Then you go to stage2 and setup the Initial plan: Escape.
Now you need the second TransX- stage1 escape , stage2 Plan: None
You match the trajectory of stage2 of the first TransX and now you have a launch heading in stage1 of the second TransX. (Confused yet?)
After you get in orbit, you can close the second TransX and continue as usual with the first one.
I think i'd just launch into a nice orbit, then plan. My Europa-Earth transfer was easy enough to build for my tastes, lol!
 

Tommy

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I like it too, it's great.
But i think it's always good to know at least two ways to solve a problem.

For example: how about a trip from Brighton beach to Olympus base, using minimum ΔV?
IMFD can provide a solution but it uses too much fuel. In this case TransX gives better results.
Or even better, use TransX for the initial setup, perform the burns and know when and where you are going to arrive with IMFD. ;)

EDIT:
In the example above, I'm talking about a solution that utilizes the Oberth effect.
In the above case, the Oberth Effect doesn't come in to play anyway - the energy required to escape the moon will provide all the dVf you need, so you won't need a prograde burn at Earth. Any burn you do make there will be an alignment burn - and that's the worst time for alignment burns.

If your IMFD solution is using too much fuel, you haven't set it up correctly - this flight should only require one main burn - the Moon Ejection. After that it's just MCC's.
 

dgatsoulis

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In the above case, the Oberth Effect doesn't come in to play anyway - the energy required to escape the moon will provide all the dVf you need, so you won't need a prograde burn at Earth. Any burn you do make there will be an alignment burn - and that's the worst time for alignment burns.

If your IMFD solution is using too much fuel, you haven't set it up correctly - this flight should only require one main burn - the Moon Ejection. After that it's just MCC's.

I thought that by mentioning the Oberth effect, a two burn solution was already implied. Perhaps I should have clarified:

I'm talking about a two burn solution, in which the Oberth effect does come into play. One burn to drop from the moon to Earth and a second one at periapsis.
 
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Tommy

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What I am saying is that simply escaping the Moon in a manner that would give you a suitiably low Earth Pe, you will already have enough velocity to leave Earth and get to Mars. To drop your Perigee to anywhere low enough to matter, you will need to escape the Moon with more than enough residual energy to make the Mars transfer.

It's not an easy set-up, and you'll have to choose your launchtime a bit carefully - Brighton's got a fair bit of Latitude so you are limited to what parking orbit you can launch into. You want set the values in Target Intercept(SRC= Earth, TGT = Mars) to minimize the dV in Orbit Eject while watching the dVp value and node location in Slingshot and Map. Look for a date when the dvF values in both Orbit Eject and Slingshot are low, keep an eye on the RInc in Slingshot, and the node is at or near the Earth's SOI. This allows you to make the final alignment to the sling plane quite cheaply since velocity is low, but accuracy is high (can be iffy much farther out than SOI).

This is only true for the Earth-Moon pair, and due to the large relative size of the Moon. If you were leaving Io, for Earth, the Oberth Effect would be more more important and TransX would be easier to use. There is, actually, a way to use IMFD for this using two burns (a hohman transfer to LJO, then use the Oberth Effect during the sling) but it is far too complicated to describe in a post! In that case, I'd go with TransX as being simpler!

For most slingshots, TransX is better because it let's you plan several stages, where IMFD is much more "one step at a time". IMFD can't, for instance, be used to plan an EJS sling unless you luck onto a window or use something else to find one. IMFD is more accurate, but TransX's system of multiple stages let's you plan much more complex trajectories.
 
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dgatsoulis

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What I am saying is that simply escaping the Moon in a manner that would give you a suitiably low Earth Pe, you will already have enough velocity to leave Earth and get to Mars. To drop your Perigee to anywhere low enough to matter, you will need to escape the Moon with more than enough residual energy to make the Mars transfer.

It's not an easy set-up, and you'll have to choose your launchtime a bit carefully - Brighton's got a fair bit of Latitude so you are limited to what parking orbit you can launch into. You want set the values in Target Intercept(SRC= Earth, TGT = Mars) to minimize the dV in Orbit Eject while watching the dVp value and node location in Slingshot and Map. Look for a date when the dvF values in both Orbit Eject and Slingshot are low, keep an eye on the RInc in Slingshot, and the node is at or near the Earth's SOI. This allows you to make the final alignment to the sling plane quite cheaply since velocity is low, but accuracy is high (can be iffy much farther out than SOI).
Would you mind posting a screenshot of the Target Intercept and Slingshot programs, so I can understand a little bit better about what kind of trajectory you are talking about?
Just the initial setup. What I would like to see is the escape vector oV and the shape of the trajectory in the Slingshot program and the escape vector oV in the Course\Target Intercept program.

Is the trajectory similar to your Moon to Mars tutorial, in the IMFD manual tutorials and playbacks?
 

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You should set Src=Jupiter Tgt=Earth in Target Intercept and optimize your delta-v.

Now open slingshot program an set Src=Europa and Ref=Jupiter, minimize PeT (some seconds is Ok) as shown on my screenshot changing TEj. Now copy Tej to Target Intercept. You should now reoptimize PeT in Slingshot Program. Repeat this procedure until PeT is minimum and both TEj are equal.

In my experience Jupiter is too much massive to tray slingshoting around it at low altitude. So in my arrangement you will optimize your delta-v taking profit of the velocity of Europa.

 

dgatsoulis

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You should set Src=Jupiter Tgt=Earth in Target Intercept and optimize your delta-v.

Now open slingshot program an set Src=Europa and Ref=Jupiter, minimize PeT (some seconds is Ok) as shown on my screenshot changing TEj. Now copy Tej to Target Intercept. You should now reoptimize PeT in Slingshot Program. Repeat this procedure until PeT is minimum and both TEj are equal.

Yeah, this solution has already been demonstrated in the video of post #5 in this thread. This is the most fuel-efficient method for a single burn solution of a Europa→Earth journey.

In my experience Jupiter is too much massive to tray slingshoting around it at low altitude. So in my arrangement you will optimize your delta-v taking profit of the velocity of Europa.
You are right about that. Even for a 2 burn solution (1st burn to drop from Europa to a low Perijovion and 2nd burn at perijovion), it takes more ΔV to leave Europa and drop to a low perijovion than to simply to wait until Europa is in the right point of it's orbit and take advantage of it's orbital speed by leaving in the same direction. (As demonstrated in the video and in your post).

You can see why in the calculation I made here, when something similar was discussed.

The only thing cheaper than the single burn solution is a 3 burn solution:
1st burn:Europa→ high apojovion.
2nd burn: High apojovion→ low perijovion (combined with whatever plane-change is needed for the transfer)
3d burn: low perijovion→Earth.

My disagreement with Tommy is about a single burn solution for a Moon→Mars journey, where I claim that using one burn to drop to low perigee and escape wastes fuel.

It is far better to wait until the moon is in the correct position and take advantage of it's orbital speed and direction. Similar to the single burn solution for the Europa→Earth journey.

It is not clear to me what type of single burn solution Tommy is suggesting, that's why I asked him to clarify on post #18. After all we could be talking about the same thing and I simply misunderstood.

@ Tommy:

If you are suggesting that this type of single burn solution:



doesn't waste fuel, then I disagree.

It would be far better to do this:



which takes advantage of the moon's orbital speed and direction and is the most efficient single burn solution.

There are even cheaper solutions but require more than one burn.
 
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