Any tips for going interplanetary?

[KerbalChamp2006]

Does anyone have any tips for going interplanetary? Im preparing to do minmus and mun landings very soon and wanted to know how to go to other planets so im not just sitting arround trying to do whatever

[Snark]

Moving to Gameplay Questions.

35 minutes ago, KerbalChamp2006 said:

Does anyone have any tips for going interplanetary? Im preparing to do minmus and mun landings very soon and wanted to know how to go to other planets so im not just sitting arround trying to do whatever

1. Pick your destination.  (I'd recommend Duna for starters, since it's pretty much the easiest to get to, but it can be wherever you like.)
2. Make sure you have a good launch window (i.e. the relative positions of Kerbin and your target planet are "right").
   • There are various online planners that can help you with this-- my personal favorite is http://ksp.olex.biz, just because it's so easy to use.  Just put in your origin planet (Kerbin, in your case) and your destination, and it provides all the information in an easy-to-read graphical display.
   • TL;DR:  if you're going to Duna, you want to launch when Kerbin's about 43 degrees behind Duna.
3. Make sure your ship has enough dV to get where you're going.
   • Going to Duna doesn't require much more than going to the Mun, and a Duna landing needs less dV than a Mun landing if you aerobrake and use parachutes.  Going somewhere else, such as Moho, can require a lot more.
   • The launch planner from step #2 above will tell you how big a burn you'll need when leaving LKO.
4. Get to LKO.
5. Plop down a maneuver node of the right size and approximate direction to go where you need to.  (The launch planner, mentioned in step 2, will tell you the size and direction you want.)
6. Unless you got really lucky in step 5, you won't have hit the bullseye on your first try-- probably you don't have an encounter yet.  So zoom out to solar system view and tweak the maneuver node slightly until you have an encounter.

 

[KerbalChamp2006]

Wow, thanks. thats some really helpful info right there.

Edited July 16, 2018 by KerbalChamp2006
Typo

[Jack5.exe]

This site can help https://alexmoon.github.io/ksp/

[KerbalChamp2006]

Ok, thanks for the help. So around 2500m/s dv will be sufficient?

(Just in case i make some errors)

[PrvDancer85]

Snark nailed it, in addition to what he said here is the KSPcheatsheet, it has an dvMap if scroll down a bit. 

Ps: i'm one if those consoleguys 

[KerbalChamp2006]

Alright, i get it now. Thanks for the help.

[Snark]

1 hour ago, KerbalChamp2006 said:

Ok, thanks for the help. So around 2500m/s dv will be sufficient?

Depends on,

1. where you're going, and
2. what you plan on doing when you get there, and
3. are you planning on coming back or not,
4. where you're measuring from (e.g. Kerbin surface?  LKO?).

Can you describe the mission you have in mind?  2500 m/s from LKO would be massive overkill for some missions, and nowhere near enough for others. 

[KerbalChamp2006]

My mission in mind is a basic land on duna via aerobraking, biome hop a bit, and head home.

And im measuring from LKO

[DoctorDavinci]

3 minutes ago, KerbalChamp2006 said:

My mission in mind is a basic land on duna via aerobraking, biome hop a bit, and head home.

And im measuring from LKO

Check your staging ... many a player including myself have designed perfect craft for a given mission only to end up borking the whole deal because of a parachute or decoupler in the wrong stage

Lets have a moment of silence for all the Kerbs lost in this manner 

[KerbalChamp2006]

Ya i always check my staging in the vab

[StrandedonEarth]

I would not call 2500 m/s massive overkill. Lots of margin is always nice as you can at least orbit Ike as well. As long as getting it to LKO isn’t getting too difficult or expensive, more margin never hurts. It beats ‘get out and push’

Edited July 16, 2018 by StrandedonEarth

[Kryxal]

I'd call that too little delta-v for the mission.  It's enough for Duna orbit and return, but you'll be well short if you land.  I'd budget around 3500 m/s for the mission for a good margin, and that's going to mean aerobraking to a landing (or at least capturing on the first pass).

[Snark]

4 hours ago, StrandedonEarth said:

I would not call 2500 m/s massive overkill.

Again, depends on the mission.  For example, if the mission was "land a probe on Duna and leave it there," then yes, it would be massive overkill, more than double the necessary dV.

As it happens, that's not what the OP had in mind, but that's the point:  it matters to the mission.

4 hours ago, KerbalChamp2006 said:

My mission in mind is a basic land on duna via aerobraking, biome hop a bit, and head home.

Okay then.  Note that biome hopping can be pretty expensive in dV on Duna, just something to be aware of.

The dV budget for going to Duna and back, without biome hopping, looks like this:

1. Ejection burn from LKO:  1050 m/s
2. Aerocapture at Duna and land with parachutes:  free
3. Launch from surface to low Duna orbit: 1200 m/s
4. Ejection burn from low Duna orbit:  610 m/s
5. Reentry at Kerbin with heat shield: free

So, altogether, that's an absolute bare minimum of 2860 m/s from LKO, without biome hopping, and with zero safety margin assuming you do everything exactly perfectly.

I'd suggest allowing at least a 10% safety margin, i.e. at least 3200 m/s of dV after getting to LKO.

Then, if you want to do biome-hopping at Duna, add many hundreds of m/s onto that (how much depends on how many biomes you want to visit, and also how accurate you are at landing near biome boundaries so as to minimize needed hop distance).

Note that there are some additional design options for a Duna mission-- for example, are you going to do a simple land-and-return as one ship, or will you do it more Apollo-style where you leave your Kerbin-return stage in Duna orbit and rendezvous with it after going back up to orbit.  The former is simpler to design and fly, but is less "efficient" and will need a bigger rocket on the pad.  Both can work quite well, it's a question of your personal tastes and the degree of KSP skills.

[KerbalChamp2006]

Ok, im planning to do 1 or 2 biome hops on a direct ascent style mission. So, 4000m/is sufficient?

[katateochi]

As other have said these two sites are great; http://ksp.olex.biz | https://alexmoon.github.io/ksp/. I recently found this mod (Transfer Window Planner) which is based on alexmoon's website, but provides the same thing in game AND it's built by @TriggerAu so of course it integrates with Kerbal Alarm Clock (which is must have if you've got more than one thing going on).   Lets you pick the optimal times to depart, or choose a less optimal but maybe faster travel time and see the dV requirements, travel time, arrival date etc, and then you can just click to add that as an alert into KAC.  AND the really cool thing is it can draw the phase and ejection angles over the map view. highly recommend! 

[Snark]

1 minute ago, KerbalChamp2006 said:

Ok, im planning to do 1 or 2 biome hops on a direct ascent style mission. So, 4000m/is sufficient?

Completely depends on how accurate you can be at picking your landing spot.  If you can manage to bring it down right near a biome boundary, then yeah, that ought to suffice.  Land in the middle of a big biome patch, with the nearest boundary a hundred km away or more?  Marginal.

And if you're aerobraking to land, it can be pretty hard to control exactly where you land.

I guess a lot depends on your balance of "ambition" versus "caution".  For example, if you're feeling that you're already kinda pushing the envelope of your skills, and you'd rather "play it safe" with something more predictable that you can be more confident with, then perhaps just forego the biome-hopping and just do a simple land-and-return.  On the other hand, if you like "living on the edge" and want to go for the gusto and don't mind some risk, then absolutely go for it.

Note that an Apollo-style mission is friendlier to biome-hopping than direct ascent is, since you're not schlepping all of your go-home-to-Kerbin hardware and fuel with you on each hop.  So if your ambition extends to "design a complex mission with a complex flight profile", that's an option, too. 

The main thing that gets harder for Apollo-style is not just "launch to orbit and dock with something" (since I'm guessing you already know how to do that), but rather precision aerobraking.  It's a lot more challenging at Duna to aerobrake to orbit than it is to just go down to the surface.  That's because there's very little margin for error-- the difference between "Pe too low, go down to the surface" and "Pe too high, go flying off into space at high speed" can literally be only a few hundred meters of altitude.  So it almost certainly requires a bunch of trial-and-error fine tuning (i.e. quicksave when you enter SoI, try it, then quickload and adjust Pe slightly and try again, etc.)

Another scenario that Apollo-style can enable is refueling.  For example, you could launch an unmanned fuel tanker as well as your crewed return vehicle.  Leave the unmanned tanker in orbit.  If you do your mission with the crewed vehicle and you run into trouble, you have the option of refueling from the tanker before coming home.  If you don't run into trouble, then you can leave the tanker in place to assist future missions.

[KerbalChamp2006]

Alright, i won't go for the biome hop now since you mention the high difficulty. I'll just send more missions and hope they land in different biomes.

[Snark]

20 minutes ago, KerbalChamp2006 said:

Alright, i won't go for the biome hop now since you mention the high difficulty. I'll just send more missions and hope they land in different biomes.

Well, one thing you could do:  go ahead and build in the extra dV, and then just hope you get lucky.    You might!  That way, if you land on Duna with extra safety margin, and you happen to be near a biome boundary, you can give the biome hop a try.  Just quicksave before you do the hop, so in case it turns out that you don't quite have enough dV, you can revert and then just go home without the hop.

By the way.  If your vehicle that's returning to Kerbin is the same one that's landing on Duna, and you're using parachutes, it can be handy to have an engineer along so you can repack the chutes and then re-use them for landing on Kerbin.  (And if you do try a biome hop, you'll want the chutes re-packed so you can use them to land after the hop.)

By the way:  you don't need a heat shield for aerobraking at Duna, assuming you have a good transfer window.  It's really gentle, you won't fry anything.  You do, however, definitely need a heat shield for return to Kerbin.

Definitely put drogue chutes on the lander-- they're really needed on Duna, due to the thin atmosphere.

[KerbalChamp2006]

Alright, and thanks for all the help. Also, can't all kerbals repack chutes?

[Snark]

1 minute ago, KerbalChamp2006 said:

Alright, and thanks for all the help. Also, can't all kerbals repack chutes?

EVA chutes, sure.  But spacecraft chutes?  Nope, only engineers can.  And they have to be at least level 1 to do it.

By the way, regarding the lander.  There are many different ways to design a Duna lander (it's nicely flexible, there are a lot of different strategies), but for a simple "land with parachutes" one, here's what I like to do:

• Make sure there's at least one drogue chute.  Set it to open as high as possible.
• Then just put a bare minimum of regular parachutes on it to land with.  Don't try to add enough parachutes to land safely on chutes alone.

Rationale:  Duna's atmosphere is super thin.  Yes, it's absolutely possible to land safely on parachutes alone... but it means you'll have to spam a lot of parachutes, which means a lot of mass.

So what I like to do instead is to just put on a bare minimum, and don't even try to have enough chutes to land safely.  Even one parachute will do.  This won't slow you down enough to actually land... but at least it gets you to the general ballpark, so you'll be falling at something like 30-40 m/s.  Then, use a brief burst of thrust from the engines just before touchdown in order to soften the landing to something survivable.

Rationale:  the fuel you use for that one brief burst right at landing weighs a lot less than the mass of all the extra parachutes you'd need to land safely.

Like I said, you can totally land just by spamming the heck out of parachutes, I merely mention this as one of your options. 

 

[KerbalChamp2006]

Ok

Decoupling the excess parachutes would work too

[Snark]

2 minutes ago, KerbalChamp2006 said:

Decoupling the excess parachutes would work too

Well, that would save you from lugging them back into orbit and all the way home to Kerbin, sure.

But you'd still need to spend all the fuel to launch them to Kerbin orbit and send them on their way to Duna.  Plus more mass for the decouplers.  Plus (potentially) extra drag from the extra chutes and decouplers.

It's mass.  Skipping them saves mass and therefore fuel and therefore leaves you with more dV to play with.  It can come in handy, is all. 

If you don't mind the extra mass and have no troubles designing a craft with the dV you need for the mission, then there's nothing wrong with packing on the chutes if that's what you like!

 

By the way, one other thing to be aware of:  if you're landing with parachutes, it really matters a lot where you land.  Duna has lowlands, and highlands.  Both of them cover a pretty big swath of the surface, so you could end up on either one.  And the highlands are a lot higher than the lowlands.  And Duna's atmosphere loses pressure very rapidly with altitude.

The result is that your terminal-velocity-with-parachute will be considerably higher in the highlands than in the lowlands.  So, for example, if you're planning a chutes-only landing, then either you need to have the navigational skills to ensure you come down in lowlands, or else you need a lot more parachutes to be able to land safely in the highlands.

(That's one reason I like the "skimp on chutes, use engine to cushion landing" approach.  Engines work great wherever, so it doesn't matter much whether I end up in the lowlands or the highlands.)

Moral of the story:  If you do go with a chutes-only landing, and then if you get unlucky and discover "oh noes I was going too fast when I landed and it broke"... check your altitude.  If it's high (i.e. thousands of meters), it means you came down in the highlands-- you may be able to salvage the mission if you can revert to an earlier save (e.g. when you enter the SoI) and adjust your approach to land in a different (i.e. much lower) spot.  On the other hand, if you go with an engine-assisted landing, then you don't have to care much what altitude you land at.

 

[KerbalChamp2006]

Ok, ill just use the engine assisted landing. Thanks for all the help!

[StrandedonEarth]

51 minutes ago, katateochi said:

As other have said these two sites are great; http://ksp.olex.biz | https://alexmoon.github.io/ksp/. I recently found this mod (Transfer Window Planner) which is based on alexmoon's website, but provides the same thing in game AND it's built by @TriggerAu so of course it integrates with Kerbal Alarm Clock (which is must have if you've got more than one thing going on).   Lets you pick the optimal times to depart, or choose a less optimal but maybe faster travel time and see the dV requirements, travel time, arrival date etc, and then you can just click to add that as an alert into KAC.  AND the really cool thing is it can draw the phase and ejection angles over the map view. highly recommend! 

The other great thing about the TWP mod is that, if you have a mod like Precise Maneuver, you can use the "copy details" button in TWP and paste the maneuver into Precise Maneuver (there's a button for that; look for the tooltip to identify it). It might not be perfect, but it'll get you into the ballpark.