Hello! And questions about NEAR/FAR and flight windows :)

[eddiew]

Hey guys and girls,

Ten days with KSP now, all of them deeply engaging, and seven of them running NEAR, Fine Print, RemoteTech, KW Rocketry, TweakScale, and a few others because they're clearly too good to ignore. Mostly going well; probes to the inner solar system, 'fast enough' jet planes for Kerbin flyover missions, and an unmanned Munar rover that can run just as well either side up, as inspired by those little radio controlled cars.

Gone career mode because I'm that kind of guy who doesn't like everything handed to him up front and loves the long discovery process with lots of use of intermediate tech levels. Indeed, I restarted after two days because I'd taken the Outsourced R&D policy, and discovered it is hideously overpowered and ruining the whole point of having a tech tree. Technically 'legit' but obviously a sploit... Much happier now that I'm grubbing around for science while battling a budget.

I wanted to make it an iron man play, but truth is I feel like the game engine is a bit too likely to 'splode my stuff for absolutely no reason. One accidental tap of time warp and my planes fall apart in flight, so I guess it'll be an honor-system iron man, where I'll take losses if they feel fair, rather than like the result of dodgy coding or lack of information at the point of commitment. I know it is rocket science, but I don't have the head for the mathematics and I have to go on what the orbital predictions say will happen - even when that's really vague and stops at 'Kerbin escape'

If y'all could spare a little wisdom, I do have a couple of questions however

1) Is using NEAR (and later FAR when I know the game better) going to make me struggle with later missions? I like the aerodynamics a lot better than stock, but it does make getting big things into orbit really hard. So far I've been focussing on unmanned flights, and have been shrinking my components to 50-70% normal size in order to wedge them into a 2.5m fairing, but I have absolutely no idea how I'm going to get kerbonauts past Minmus. They'll need better comms, which will need to be shielded in a fairing, which will not fit around a big capsule; rovers for a crew will need to be bigger than my scaled down mini-rover, and yet I had to think really hard about how to fit a skycrane and lander into a fairing, just to land on Mun; etc.

In short, does FAR or any other mod, provide any solutions to the (realistic) problems that FAR brings to the table, or is it something nice to play with for a while, but an obstruction later on?

2) I've been looking at Transfer Window Planner and MechJeb to help me find the right times to get to places. The first just gives me angles and delta-v's that I have no real idea how to implement, and while MechJeb will create a manoeuvre node, it has a habit of not arriving in a very good place for getting into orbit around my destination. Example, my recent Moho probe just barely achieved a wonky orbit with 12 m/s left in it's fuel tank. According to TWP I should have arrived with a thousand times that to spare, transferring orbit-to-orbit, which was to my mind 'plenty'.

The question then is whether TWP is providing a fair calculation of delta-v, and if it is, how can I go from what it's showing me on screen to a set of manoeuvre nodes that I can execute? Otherwise, how can I get MechJeb to tell me what the other half of the transfer will be, before I launch, so that I don't try this with a crewed vessel and have to abandon it and return home?

Thanks for your advice!

[NathanKell]

Welcome!

1. NEAR is FAR without the mach effects and the wing interaction and the GUI. It's not really easier or harder (it's easier to go fast, but that's not always a good thing, like on reentry) and while it doesn't provide lots of info, that means you don't have info to look at as to what needs fixing in your design. If you're using Procedural Fairings, there is currently an issue with larger-than-1.25m fairings and FAR not detecting parts as shielded; you might need to use (non-procedural) KW fairings for now. However, you should not need to fair pods or the like, only very unaerodynamic things like probes with lots of solar panels and wheels for rovers and the like.

What are you running where you need comms? RemoteTech? That only kills antennae that are deployed, which you need not do when launching a crewed mission since you don't need a connection to mission control. For probes, you will need to have an antenna, but there is one that does not rip off.

If you're finding things rip off if you're not hiding them in fairings, then you're probably ascending too fast. Try lowering your launch TWR to about 1.5, and using a low-thrust second stage for the final 1000 or so m/s to orbit (i.e. starting TWR about 1).

2. For a transfer, you can use the MJ transfer-to-another-planet autopilot, then once in the Sun's sphere of influence use "fine-tune closest approach to target" and set the periapsis as desired. Do another fine-tune when you get in the destination SOI.

You will always want the lowest periapsis possible that is not inside your destination's atmosphere for the cheapest circularization, IIRC.

[eddiew]

NEAR is FAR without the mach effects and the wing interaction and the GUI.

Tbh, it's exactly that which was scaring me off FAR. Being quite new to KSP, I'm not really sure what will get me to what speed - it was a total surprise that my ram/turbojet fighter goes as fast as it does Might give it a shot, though, since I think I now understand how to design planes that don't fall apart. Although I did try a 15G turn at 1500 m/s yesterday. Even with just NEAR, it didn't go well, but hey, that's why I always put a radial parachute on the pod

If you're finding things rip off if you're not hiding them in fairings, then you're probably ascending too fast.

I haven't actually had anything rip off, because I've been wrapping every single probe in a fairing Although a couple of times I've screwed my staging up, the fairing has popped at the same time as my boosters detached, and then taken off a solar panel or dish because it's gotten caught in the airflow and dragged down the side of the rocket. Aside from that, my worry is things like the big reflector dishes, KR-14 and up, which I think don't survive a launch?

And then yeah, there's issues about how big a rover I can put on the end of a rocket, because they're not the most aerodynamic objects to put on the front of a rocket. That said, maybe I should actually try to launch something ridiculous - maybe it's not as much of a problem as I'm expecting it to be Been investigating the robotics mod too, the hinges in that look quite promising for giving some fold up options, if I design stuff cleverly.

2. For a transfer, you can use the MJ transfer-to-another-planet autopilot, then once in the Sun's sphere of influence use "fine-tune closest approach to target" and set the periapsis as desired. Do another fine-tune when you get in the destination SOI.

You will always want the lowest periapsis possible that is not inside your destination's atmosphere for the cheapest circularization, IIRC.

Ah, that sounds like the 2nd step that I've been missing, cheers The initial Hohmann transfer is pretty good at getting in roughly the right location at the right time (or at least it's better than guessing!), but fine tuning as early as possible is decidedly what it needs. I'll give it a go later tonight, thanks!

[NathanKell]

1500m/s is Mach 5. I certainly wouldn't want to pull more than a couple Gs at Mach 5.

As long as you build your planes to look like planes, and fly them like you'd fly real planes, they should behave fine in FAR. With the one caveat that most modern fighters are designed to be statically unstable for increased maneuverability (i.e. CoP [what KSP calls CoL] in front of CoM) which, since we don't have fly-by-wire in KSP, is a bad idea. But planes that look like real planes tend to fly fine.

If you've got lots of antennae/dishes, then yes you will need to fair them. I suggest placing them on the bottom of your service module, and using a smaller engine than the tank size (i.e. x16 tank with LV-909) and ringing the solar panels and antennas around it. Then you can use a procedural interstage to fair them all. If you're launching a probe or a rover, though, presumably you'll be fairing it all anyway, so no problem.

Though, do note that PF shielding bug right now...

You can literally launch *anything* in FAR, if you give it enough delta V and control authority. If necessary, limit acceleration to 1.5G max and burn lotsa fuel. That's the thing about the stock-sized planets--you really don't need to do much to get to orbit.

(Note that you shouldn't be having a launch TWR much above 1.5 anyway...)

How did the fine-tuning go?

[eddiew]

1500m/s is Mach 5. I certainly wouldn't want to pull more than a couple Gs at Mach 5.

Ohhhh... right, I see. In my head, the speed of sound was ~700 m/s, but it turns out I was thinking of miles per hour Ok, now I see why it fell apart - and why it glows so beautifully during night flights!

And yeah, one of the reasons I wanted FAR/NEAR from the outset was that I'd seen planes in it have a habit of looking realistic, which makes me feel better about the physics modelling overall My current jet resembles a Eurofighter Typhoon and (apart from the turning at mach 5 issue) handles really well for roll and pitch.

If you've got lots of antennae/dishes, then yes you will need to fair them. I suggest placing them on the bottom of your service module, and using a smaller engine than the tank size (i.e. x16 tank with LV-909) and ringing the solar panels and antennas around it. Then you can use a procedural interstage to fair them all. If you're launching a probe or a rover, though, presumably you'll be fairing it all anyway, so no problem.

Though, do note that PF shielding bug right now...

For the moment I'm getting away with KW Rocketry's fairings. Though it did look silly when I launched a fat but light satellite in a 2.5m extended case, on top of a 1.25 rocket! Made it to orbit though, amusingly. Biggest challenge is rovers, though using Infernal Robotics hinges, I've now got a pretty solid 6 wheeler that folds its legs underneath it so it can be turned on end and just fits in an 2.5 ext fairing, along with a skycrane on top of it holding 1200 delta-v. Comes with the handy bonus of being able to tweak the ride height if it's grounded out

The interstage idea is a nice one though, I'll look into that - might make my designs a bit less bulbous up top! If nothing else it sounds like a good place for mono propellant tanks.

How did the fine-tuning go?

Annoyingly I didn't get round to it; turns out I have 85 game-days until the best Jool window for the next ten years, so I'm scrambling to dredge up local science from Kerbin and Mun and Minmas so's to be able to get the best possible ship ready. New rover will definitely be in the fleet that goes out, the question is whether I can manage an orbiter with a return stage to get the best possible science back... Plenty of money, but I don't think I've unlocked the nuclear engine yet cos I went towards probes and spaceplanes instead of rocketry

I'll definitely use your MJ tip when I launch that lot though, thank you