FAR + MechJeb + Deadly Reentry

[Lord Aurelius]

Hi Everyone,

I'm not sure if this question has been asked before, but I would like to know if there are any compatibility patches/hacks that I could do to get these three mods to play nice with each other. The aerodynamics from FAR are nice, but they break MechJeb's landing autopilot on anything with an atmosphere and also cause deadly reentry to apply way too much heat on reentry. Are there any fixes for this at this point?

[redteddy23]

I don't know about DR but I have an install with FAR and Mechjeb. When it comes to landings in atmosphere I just have to estimate based on experience. To get MJ to work out landings for FAR it would have to have all the calculations it uses redone to take into account FAR's more complicated model for drag and the forces applied to your ship, which is possible I guess but I know of no alternate MJ build. You can use the landing window to show target and estimated landing then burn retrograde until you are landing in behind your target from between 20 to 200km. The distance depends mainly on two things, how shallow your re-entry is and how aerodynamic your ship is. For a barely controlled rocket coming down end first there will be a lot of drag and the overshoot will have to be big, for a controllable plane a lot less as you can dive down into a horizontal landing approach. Obviously a steep re-entry will land closer to the target as the drag forces are not acting as much horizontally.

[m4ti140]

If sources are included on both you can try rewriting MJ2 landing guidance - would be mostly copypaste from FAR code I guess. But that's not the only problem MJ has with FAR

As for FAR + DR, they work even better when used togeather - when designing planes you get over-g damage and heat from overspeeding, making it even more realistic. As for reentries, deadly reentry 2.3 is not that deadly Only when you use it with FAR you can get some reasonable temperatures on reentry + skip reentry is possible with capsules with FAR.

[longhornchris]

Mechjeb doesn't do to well with FAR while in the atmosphere. Mechjeb is useful, however. The 'Prevent Flameout' works fairly well if you set the margin high enough; I use 10% with most designs. Additionally, the information tabs are quite useful for determining when you have a good apoapsis for the climb out. Just don't use Mechjeb to fly the ship when in the atmosphere for planes.

For rockets, ascent guidance works but you need to have a cleanly designed rocket. Additionally, I've found that any active fins should be set to 'roll' only or you risk having your rocket shake itself to pieces. Additionally, you need lots of gimbal authority to stay under control until you get up to speed where the vehicle becomes aerodynamically stable. That, and EVERYTHING needs to be in a fairing or the drag is going to be really high.

[Designer225]

FAR + MechJeb is much harder than I thought.

[Lord Aurelius]

Thanks for the responses, it looks like there isn't an easy fix at this point. With how popular FAR + MechJeb is hopefully someone can put together a MechJeb build that supports the FAR flight model (way beyond my limited programming skills). Deadly Reentry issues sound like its more an issue of me not being terribly good at designing/flying craft for atmospheric reentry. I probably should aim for a much gentler slope into the atmosphere instead of blasting straight down (like mechjeb sometimes likes to do) and hoping I put on enough heat shielding...

Random question: does anyone have any working designs for an Eve lander (would be nice if it was capable of returning to Eve orbit) that utilizes this combination of mods?

[Bloodbunny]

With DR and FAR, you should set your PE somewhere between 20 km and 29 km, depending on reentry speed. Any higher and you'll "skip" back out and land in some random place eventually, any lower and you'll either go boom, or you'll survive reentry heat only to still be traveling too fast for parachutes at 1-2 km and go boom when you hit the ground at 700 m/s.

As in real life, returning from LEO is much more forgiving than returning from Mun

Edited July 17, 2013 by Bloodbunny

[satcharna]

The simple solution is to just land it yourself. I've tried MechJeb's "auto-lander", and I found it a lot more difficult to do a good landing with that than just doing it manually. Set your periapsis to the top of the atmosphere to shed velocity in an aerobrake, and once your apoapsis is low enough, perform the deorbit burn. Aim to re-enter at a fairly shallow entry tunnel, and wait with deploying your parachutes until you're slow enough to not rip them off.

[birrhan]

With DR and FAR, you should set your PE somewhere between 20 km and 29 km, depending on reentry speed. Any higher and you'll "skip" back out and land in some random place eventually, any lower and you'll either go boom, or you'll survive reentry heat only to still be traveling too fast for parachutes at 1-2 km and go boom when you hit the ground at 700 m/s.

As in real life, returning from LEO is much more forgiving than returning from Mun

By "skipping" off the atmo, is it still possible to aerobrake with one or more passes prior to reentry (or even to establish an orbit) using FAR + DE?