IMFD Closest approach in one burn.

[Mister Mxyzptlk]

For you IMFD experts: What is the closest flyby approach you have made/can make to Mars using IMFD and just the eject burn, no midcourse corrections?

I am interested in the comparative accuracy differences between IMFD and TransX.

This is not a contest or a challenge.

 

[orbekler]

This is not a contest or a challenge.

It's an interesting initiative, however factions will be inevitable...:lol:

 

[Grover]

It would depend on realism settings, but i suppose its down to luck, or good choice of launch date (some people have hit the moon on their trans mars ejection, its possible you could get near another SOI)

Heres a better one though, how accurate can you do it.by slinging around jupiter as well with only two burns (or the technical minimum for that flight)

 

[agentgonzo]

Imfd will be more accurate for a single burn as it uses a better model (numerical propagation rather than patched conics).

 

[orbekler]

Imfd will be more accurate for a single burn as it uses a better model (numerical propagation rather than patched conics).

But that is the description of Lunar Transfer, not IMFD... (Jarmonik anyway)

 

[Tommy]

IMFD uses numerical propogation as well, in fact you gave a couple choices as to what system it uses. However, all programs except Map us a two body solution - so there's a limit to the accuracy that can be achieved with Target Intercept, for instance.

Using IMFD's Delta-Velocity program, along with Map program, will give you the most accurate burn. TransX allows for finer adjustments when planning the delta-V, but accuracy of the projection is limited by the conic subsection method, and execution of the burn is dependent on the pilot's skill.

Target Intercept could be used to plan the flight, and the burn Info from Orbit Eject used as starting values for Delta-V, then adjusted using Map's Plan and Intercept modes.

 

[Evil_Onyx]

My experience with IMFD and mars intercepts, is that i have to do a MCC to fine tune the final approach to avoid hitting the planet anyway.

Although how accurate you are is dependent on how you plan a trip like that, rather than what you use to plan it with. As in, knowing the limitations of your tools and taking that in to account.

I'm one of those people who have had an unexpected visit the the moon when attempting the go the mars, now i almost always try to do a slingshot with the moon on my way out in the the rest of the system just to avoid hitting it by mistake.

 

[orbekler]

IMFD uses numerical propogation as well, in fact you gave a couple choices as to what system it uses.

Is that "Propagate TEj" option in Global Configuration?
Actually I read about the numerical propagation of Lunar Transfer from Jarmonik site, didn't know about IMFD's.

...TransX...but accuracy of the projection is limited by the conic subsection method, and execution of the burn is dependent on the pilot's skill.

Pilot's skill... That's the problem...:lol: Sincerely, with TransX I find difficult to stick the cross in the center of target, uncertainty grows as burn goes. That's why I prefer to leave to IMFD the duty of burn.

 

[Fabri91]

Is that "Propagate TEj" option in Global Configuration?
Actually I read about the numerical propagation of Lunar Transfer from Jarmonik site, didn't know about IMFD's.

Pilot's skill... That's the problem...:lol: Sincerely, with TransX I find difficult to stick the cross in the center of target, uncertainty grows as burn goes. That's why I prefer to leave to IMFD the duty of burn.

Lunar Transfer MFD should be a stripped-down version of IMFD specially taylored for Apollo-like transfers from Earth orbit to the Moon.

 

[Tommy]

Is that "Propagate TEj" option in Global Configuration?

I'm not at home so I can't fire up IMFD or read my notes, etc. That doesn't sound right - I think that has something to do with AMSO compatability - but could be wrong. Something that offers "RK-3" or somesuch as one of the options. Possibly only applies to Map program. Get back to you in a day or two after I check on that.

Lunar Transfer MFD should be a stripped-down version of IMFD specially taylored for Apollo-like transfers from Earth orbit to the Moon.

Not really. IMFD is designed as a "swiss-army knife" of nav tools. There is a blade - er, program - for every thing.

LTMFD is a much more focused toolset. You can plan a lunar trajectory (hohman, free-return, etc) much more accurately and easily in LTMFD. It is the "set of screwdrivers" of nav tools. Works better at turning screws than the swiss army knife, but not useful for anything except turning screws.

 

[orbekler]

@Tommy: I found in Map Configuration the parameter "Method", and available values are: RK4,RK6;RK7 as from the manual "The user can select the integration method fro Thir order RK3, RK4-Gill, Symplectic 4th Order and RK-Fehlberg methods. Also Adams-Multton method is under consideration."
I'll try different integration and see the differences compared to same start scenarios, but in someway I think that they won't affect Target Intercept burn, but just Map accuracy, is it?

@Fabri91: if you try Lunar Transfer MFD, you'll see that is very easy to setup, and VERY precise, and most often than not, the MCC is just a puff (even if you don't make the correction, the free-return will work in anyway):thumbup:

 

[Fabri91]

Thanks for the info to both of you!
I already used LTMFD many times, but to be honest I'm not really aware of it's inner workings, so I assumed it was a "IMFD with some settings locked", but the screwdriver-knife analogy makes perfect sense at explaining how the two programs are really related!

 

[Tommy]

@orbekler Yes, those are just for map. Now that I think about it, I think there's an option on the main config page, at the bottom - but the setting shouldn't be changed (not working correctly or something like that).

There are a couple variations of the AP solver, but that wouldn't affect trajectory planning - just execution.

 

[orbekler]

@orbekler Yes, those are just for map. Now that I think about it, I think there's an option on the main config page, at the bottom - but the setting shouldn't be changed (not working correctly or something like that).

There are a couple variations of the AP solver, but that wouldn't affect trajectory planning - just execution.

Yep, Lambert AP - P30 or IMFD, P30 using constant attitude for ejection burn.
BTW, P30 - isn't the same model used by TransX Target view (if not, we would constantly change pitch & yaw:download?

 

[HAL9001]

with a lot of luck you'll crash to mars surface. you'll just have to wait for right constallation, otherwise you'll have to d a long flight and that will increase the rate of correction you'll need...

 

[Mister Mxyzptlk]

Evil Onyx, you say you bullseye Mars with a single burn?

 

[Tommy]

BTW, P30 - isn't the same model used by TransX Target view

I can't say what method TransX uses. In IMFD, P-30 mode attempts to reproduce the behavior of the Apollo flight system and the burn had a fixed orientation throughout the burn. P-30 has the plan polarity reversed from the normal - a positive dVp is in the anti-normal direction, I don't think TransX does this.

 

[Evil_Onyx]

Evil Onyx, you say you bullseye Mars with a single burn?

not necessarily bullseye, but hit the planet yes.

1. make your escape trajectory opposite to the moon, to reduce its influence.
2. use more Dv then required for a hohmenn transfer, Quicker flight means less inaccuracy over time.
3. Tweek your planing tool until you are happy with the results.