Kerbal Space Program

[Burning Bridges]

I went solar orbit>eve slingshot at 400 km periapsis (IIRC)>solar orbit>moho. Which is an inefficient way of doing things apart from the slingshot. Although I wonder how good the oberth effect really is as far as delta-v saving is concerned.

Good tips. The problem is it's still hard to understand without an image or something. ("solar orbit>eve slingshot" must certainly be done in an exact way)

If you're doing that and still not getting shit protractor is bugged (because you can always plan a close as possible surface grazing encounter regardless of the trajectory, it's just that it may require an unrealistic amount of delta-v) so I recommend double clicking on the moho encounter periapsis which you will get from a planned maneuver (so it's distance displays all the time even as the cursor is not hovering over it) and adjust the maneuver using that.

That's, what I thought as well. That there is a trajectory to get anywhere any time, but using a launch window helps me to save fuel. I could never clarify if there is really any reason to use tools like Adam KSP, or if I can rely on maneuvre nodes right away. I do hardly any interplanetary flying, got so much used to how easy it is to go to the Moon, that this encounter stuff still freaks me out (it's not much fun either).

And yes I am sure it was like 5000 m/s. The trajectory must have been pretty bad, my speed was too high, over 12.000 m/s


P.S. I remember that I have asked the exact same question some months ago, and you may have answered it Perhaps you could just point me to the answer.

 

[Absalom]

You're making this much harder on yourself than it needs to be Bro. Like hellraiser said you need to be pretty goddamn accurate to get an encounter, but if you use the kerbal phase angle calculator you shouldn't have any problems. 2k m/s sounds about right to slow down, tho. Early on that was my biggest problem actually. Use http://ksp.olex.biz/ too

 

[Hellraiser]

Burning Bridges I think I actually quoted or replied to that. But that's deep within one of the LPs.

What I did last time was basically I did a regular eve flyby, I adjusted my trajectory to take me very close above Eve's surface, so close in fact that it's gravity bent my trajectory backwards towards it's retrograde and thus into a low solar orbit (although not near Moho). The probe coasted in Solar Orbit until I could do a hohmann transfer to Moho. Still wasted a ton of fuel as I did a 1 km/s inclination burn and another burn for the transfer. The delta-v map says it's just 730 m/s for an encounter after you escape from Kerbin's SoI so overall it was a fuck up:

In short I would say that while protractor and other tools aren't needed to get anywhere they're useful if only so you don't miss the launch window. Easiest way to do proper interplanetary transfer burns from LKO is this (I only recently got the hang of these instead of going from Solar Orbit which is wasteful):

1) Wait for the right phase angle first, this is really the only thing you need ingame tools for since the closer to the right angle the burn is the more accurate it will be.

2) Set the your target planet as a target in orbital map view.

3) Plan a prograde burn at the right spot in your orbit, you can use this online calculator here although simply dragging the maneuver node around your orbit should make you find it eventually. The calculator takes out the guessing and allows you to go 4) ASAP.

4) Once the node is in the right place adjust it from a zoomed out orbital view until you get the closest and most efficient encounter you can. Just remember inclination differences do influence how close you are able to get with just one burn. Oh and double click the predicted periapsis so that it's distance stays displayed as you adjust the node.

5) Burn as planned.

6) Check your trajectory after the burn. If it went as planned and there were no error skip to 8) otherwise go to 7).

7) Plan a course correction burn to adjust your trajectory. Remember: the closer to your target you are the more delta-v you need to do correction burns but the more accurate they become. That's why NASA always does a mid-course correction burn (it assumes every transfer will require at least two), because there is always some error and you'll make less of an error due to burning too little or too much the closer your are. Still if you can plan and correct it accurately sooner the less delta-v you spend.

8) Burn normal/anti-normal to match orbital inclination at the ascent/descent node before you reach your target. Unless you want to park in a highly inclined or polar orbit.

9) Once inclination is matched you can start planning a closer encounter if you want to aerobrake or just do a low altitude insertion burn utilizing the target's oberth effect if it has no atmosphere. Also adjust the encounter's periapsis so you enter on an "eastwards/counterclockwise" orbit, that makes getting to the Moons or return from the surface more easier and more efficient.

10) If you were aerobraking into orbit raise your periapsis above the atmosphere. Or redo aerobraking at a different altitude if you crashed or were still traveling at escape velocity.

 

[Burning Bridges]

Just that I get this right, do you guys plot all transfers from Sun Orbit, or from Kerbin Orbit? Even with any of the tools I can not imagine getting the ejection angle from Kerbin orbit could ever be easy.

I only tried solar orbit with outer planets and Jool / Duna was in fact not hard, because I could just move the node along the orbit until I got close enough, then fine tune for an encounter.

Ehen I try to do it from Kerbin orbit I have to zoom in / out like mad and in the end one wrong click fucks everything up.

 

[Hellraiser]

I go from Low Kerbin Orbit nowadays, the ejection angle does get fucked up often since most of the burns using the nuclear thermal engines are long but I manage to plan the maneuver easily. After that I just do correction burns ASAP to get a rendezvous if that happens. I adjust the trajectory again and how close the encounter is after matching inclination somewhere in the middle of the transit, wherever the ascent or descent node pops up. Getting a perfect trajectory with just one burn is simply unlikely unless you are using a high thrust engine, but even then you are likely to overburn.

You still waste some delta-v on corrections depending on how far off you were but the oberth effect's boost should be bigger than those.

 

[Absalom]

You don't really need to worry about the ejection angles if you have the correct phase angle. Honestly bro it's not even difficult, wait until the window opens, and burn prop grade until you get an encounter.

I used to do it from solar orbit as well but that was much more time consuming (and difficult.)

 

[Burning Bridges]

Another thing, in previous version I kept reading it was necessary to edit a cfg file, something with how encounters are shown on the map. Is this still recommended? I always forget what it was.

 

[Burning Bridges]

In short I would say that while protractor and other tools aren't needed to get anywhere they're useful if only so you don't miss the launch window. Easiest way to do proper interplanetary transfer burns from LKO is this (I only recently got the hang of these instead of going from Solar Orbit which is wasteful):

Isn't it much less wasteful if I use a Munar gravity assist? This does not appear very hard either.

I will try to figure out the rest you wrote piece by piece. But anything that only mounts to tricks which alleviate the complexities of the maneuvre planning system does not sound practical.

I figured out as much (the most basic things):

- launch window is the best time to launch, but can be ignored at a cost in deltaV
- setting maneuvre node from solar orbit is much easier (because node can simply be moved along the orbit to get right ejection angle), but deltaV for getting into solar orbit is wasted
- phase angle is more important than ejection angle

 

[Burning Bridges]

Tonight I got a Dres encounter, the trick was to first make a solar orbit with the same inclination as Dres. From there it was rather easy. I am getting more confident that this should work with Moho as well, and begin to understand what you guys are talking about

 

[Burning Bridges]

Probably it's better to simply practice the effects. Began with a Munar gravity assist.

I got as close to the surface as I could risk (6000m). The final speed on my solar orbit (after Lunar and Kerbin escape) was 9485 m/s / Kerbin moves at 9284m/s. If I subtract the two values there is a difference of (only) 200 m/s. Is it correct that the effect is so small?

If so, it would not be worth it. I propably used up more for the exact course corrections than I gain in total.

It totally makes sense because Mun is such a small object, and afaik NASA does not use Lunar gravity assists either.

But I'm not sure if I did it it right, perhaps someone can comment on my screenshots.

 

[Absalom]

Nah man, gravity assists are not worth the effort. In Jool they are worth it, but it's hard to compute it without doing actual math so I usually don't bother. If you want burning bridges, I can upload some screenshots later of a mission to Moho

 

[Burning Bridges]

Sure, that's what the thread is for.

I may also make another attempt. I have improved my rocket (deltaV is now 17.000 m/s), and I hope aligned solar orbit to Moho inclination will do the trick.

 

[Absalom]

17000 Δv ? That could do the trip 2 times over! (If you managed everything perfectly with a landing and return to earth, which I could never hope to do it.)

Anyway, this is a failed attempt, but as it's main function is to show how phase angles and LKOs' are your friend, it doesn't matter.

The interplanetary calculator (linked before in thread) tells us the phase angle for a Moho transfer from LKO is -251 degrees. As mechjeb lists phase angles only in the positives, we have to subtract 251 from 360 to get 109. Theres a geometry theorem that proofs this but I forget the technical term.

Looking at the Δv map before, I see it's 1680ish m/s to get an moho intercept. I make a manuever node for that much m/s, then move it around the crafts LKO to find one that looks right-ish.

We begin burning at that phase angle and ejection angle. KSP decided to delete my maneuver node when I wasn't looking, but I make do anyway.

Mid-course corrections to bring us onto the same plane. You'll notice that I had gotten pretty close while half assing it. The bigger planets don't really require this.

Anyway, I missed an encounter by 500,000 meters but this only took me 15 minutes. Moho is in my opinion the hardest encounter to get but I hoped I helped in some way.

Later today will be the 2nd half of the Jool mission

 

[Burning Bridges]

17000 Δv ? That could do the trip 2 times over! (If you managed everything perfectly with a landing and return to earth, which I could never hope to do it.)

Believe me it's needed to offset my poor flying skills. I never get anywhere near the figures people consider as optimal. For example slowing down to Moho was still 3700m/s this time.

The spacraft is actually pretty good, 17.000 m/s for just 136 tons. That's because I spend more time designing than flying. I weight optimize everything in the upper stages, using Excel sheets.

There is something in my LP about Micro propulsion drive. For such craft every part / kilogram counts, with heavier craft it works completely different I think. However I ditched the Assberger staging, a great idea by Ulminati which I used to get even more deltaV from the nuclear drive.

17.000 is of course in vacuum, the actual figure from Kerbin orbit is like 11.500 I believe, but that's still enough for every planet I think. I also still waste some potential by carrying an additional orbiter with RCS fuel, a Thermonuclear reactor, and some unecessary stuff that is needed for stability.

I first allerated I out of Kerbin orbit towards the sun.

Then burn at the point where Protractor said there is a launch window. It worked.

But the encounter is minimal, lasting only 40 minutes and at breakneck speed.

ca 3700 m/s to slow down into a polar orbit, because the inclination was of course way off

Then some 300 more for a proper eccliptic orbit.

Several maneuvres to get closer and closer to the surface.

Separation of the orbiter, which fucked up my weight consideration with 600 kilogram extra, but ASAS, RCS and thermonuclear power are very helful on the trip. Plus it's always nice to have an orbiter that can stay for good.

Another probe of the exact same design made it to Dres orbit. There is still enough fuel for a landing I think, which should work the same way as on the Moon (Dres gravity is even a bit less).

I actually like Dres even more than Moho, it looks like a real moon. But both are the most interesting places I have seen in the Kerbol system. Not like the cheesy stuff in the Jool system (Tylo is great though). And it feels great to finally have reached them. I might do Eeloo too.

 

[Absalom]

I actually like Dres even more than Moho, it looks like a real moon. But both are the most interesting places I have seen in the Kerbol system. Not like the cheesy stuff in the Jool system (Tylo is great though). And it feels great to finally have reached them. I might do Eeloo too.

Ah you got there. Good job. What do you find cheesy in Jool? It being green? Laythe, the moon that has no business having an ocean? Dres is ok for what it is (I put a Deloreon on it) but I'm more interested in the asteroid belt that Dres is going to be the sheperd moon of.

I don't know if I am even going to post the screenshots of my Jool mothership mission. It went to shit, and not in a funny way either. Just poor planning and bone headed decisions on my parts. I really should keep a checklist so I don't forget shit

 

[Hellraiser]

IIRC his gripe with Jool is that the moons are a bit half-assed in execution, Vall not being particularly original and laythe being 4/5 of kerbin in everything but ocean coverage. Vall could use a facelift (it will from what one of the devs said) but I kind of like that ball of ice anyway, laythe needs one as well which is also planned. There's supposed to be volcanism on laythe, lot's of it in fact, a few pools of lava and overall it's supposed to sit within Jool's radiation zone if/when those get added. Overall surface hazards are something they need to add, some minor stuff like geysers got prototyped but it's not a priority yet so before they add that it will be a while.

BTW they're fixing ASAS/SAS, getting rid off free torque on command pods and adding it to new reaction wheel parts which use electricity. Which is good because making automated tugs was a bit annoying when you had to add a manned pod and EVA the kerbals or else see the thing rotating too slowly.

 

[Absalom]

Hmm. Really. I wonder if/when life support will be added? Reaction wheel parts sounds cool, but I wonder if they're ever going to add an "emergency" system. Like apollo 13. We already have the kerbals fixing wheels and repacking parachutes.

Honestly though Im excited at all the stuff they're gonna add.

Joolian moons are a bit silly but I think of all the celestial bodies in the game as works in progress anyway.

 

[Burning Bridges]

The problem is not that Jool is green. The problem is that it's texture and athmosphere are absolutely primitive. Whatever they use to texture Jool it must be ancient.

The other problem is that I spent a lot of time looking at NASA images and most objects around Jool have little resemblance to real objects.

Wtf were they thinking when they created stuff like this? It looks like pistachio icecream, not like any substance found in the solar system.

It does not only look shit compared to other engines, it looks shit compared to some good stuff they did themselves, like Tylo, or the Mun.

It does not have to look photorealistic, but they should either use a more natural color palette, or allow users to mod the planets. For comparison, the colors on the gallilean moons. Tylo / Dres / Moho are not far off.

Umbriel, another typical object in the solar system.

Triton, shows that moons don't have to be only grey or brown (we now know there are hundreds of such objects in the Kuiper belt).

It's time that they should make clouds and thick athmosphere. Some objects are quite good.

Tylo looks like a moon
Dres looks like a moon
Mun looks like The Moon
Moho looks a bit like Mercury
Duna, well it is ok, but should have small clouds and the ice caps look totally wrong

A lot of other stuff is shit imo.

>Kerbin looks nice, but should have clouds.
>Eve should have clouds and a thick athmosphere, then it would be super cool, because Venus / Titan analogues are completely missing.
>Jool should have a very thick athmosphere.

And as Hellraiser said, Laythe is but a refactored Kerbin, without clouds too, without any resemblance to anything in our solar system. I can simply not understand why 95% of people call it their favorite moon. If I could mod that part Laythe would be the first thing I'd throw out, and never look back.

 

[Burning Bridges]

Another question, related to the Jool system. I noticed that one of my probes which I had parked around Jool, was "flung out" of the solar system by gravity in persistence mode. So far I'd thought everything would move on rails while in persistence state??

I didn't know that I have to orbit around Jool orbit or one of its moons. I fact I thought an elliptical orbit that crosses many possible moons would be much better. Then I was actually surprised about the number of possible encounters with moons. Apparently either Tylo / Laythe or Jool quickly catapulted my probe out of the SS. That's something I had never considered and adds an interesting new challenge.

 

[Ulminati]

The reason people like Laythe is because you can make floating bases and fly jetplanes on it.

 

[Burning Bridges]

With all that said, there is still Tylo, which looks great imo. Like a more cratered version of the brownish moons of Neptune, e.g. Oberon.

I really like it. Appears quite challenging and costly in terms of fuel budget.

 

[Burning Bridges]

The reason people like Laythe is because you can make floating bases and fly jetplanes on it.

Do you know if there is now some sort of ballon mod, that can be used on probes too? Last year I was looking for an inflatable balloon, to fly over Duna / Eve.

 

[The Vanished One]

The reason people like Laythe is because you can make floating bases and fly jetplanes on it.

Do you know if there is now some sort of ballon mod, that can be used on probes too? Last year I was looking for an inflatable balloon, to fly over Duna / Eve.

Is this what you're after?

http://kerbalspaceport.com/hooligan-labs-airship-parts-and-plugin/

I haven't tried it personally though. (I haven't tried any mod actually.)

 

[Hellraiser]

Just noticed the procedural wings mod got released:

Basically you can shape a single seamless big pair of wings as you see fit in the VAB rather than stitch together giant wings from several wing parts.

I think I'll use it for my latest project which I have yet to start, the albatross kethane-electric duna plane. Basically a somewhat big plane with electric propellers powered by kethane electric generators. Not sure if the generator+kethane tanks aren't too heavy to lift though, however at the very least the part count will be lower than it usually is for electric planes since it won't need solar panels. Also I'm not quite sure how good of a range the thing will have, it may end up being more of a Dodo than an Albatross.

Also I discovered cupolas make for excellent rover command pods. Made a tanker and a "bus" rover using those. They look pretty nice and drive decently, IVA view is great. Only problem is the cupola is boarded from the top as they needed some ladders.

 

[Hellraiser]

It looks my kethane-electric plane concept works better than expected.

First I did a proof of concept prototype the Prometheus. Kethane is fairly heavy so 3 propellers are the bare minimum, fuel lines weren't needed as kethane is depleted globally by generators (like RCS fuel is drained by thrusters), surprisingly enough. The wings are the procedural wings, they're really great although take a while to get used to how you can shape them. Because the generator has variable output and automatically produces as much power as you need (with a delay so a buffer made of batteries is a good idea) kethane consumption is pretty good, needs about a generator per two propellers running at full power.

However there's a bug (or feature, depending how hard it would be to fix it) in the way power consumption is calculated for the electric propellers. It's based not on how much you throttle but how much thrust it actually generates and thrust is tied to atmospheric pressure for propellers. So at high altitudes and on Duna the power consumption is laughably low ridiculously increasing the range, probably making it capable of circling around duna on a full tank, twice. Nevertheless even at Kerbin sea-level kethane-electric propulsion is not far from jet fuel efficiency.

Upscaling the thing wasn't too difficult, I used nose-mounted propellers instead of the stack ones due ease of placement/aesthetics (they're about 20% less powerful though). Lands surprisingly well on Duna "sealevel", has drogue parachutes for landing in the highlands but I haven't been able to try that yet, I don't recommend trying to land higher than 1km with a duna plane. Takeoff isn't an issue, the altitude ceiling is lower than on the prototype, only about 4+ km so you're grazing mountains. Still it lands and takes off with 2000 kethane, the range is ridiculous due to the mentioned electricity-usage math issue. Even without it I think you could fly a quarter way around duna easily.

Oh and I do love that b9 cockpit, I hope they get the guy to remake spaceplane parts. After they hired him he's making visual fluff for the KSC and new facilities.