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Direct Ascent, Kerbin Rendezvous, or Target Rendezvous?


Jestersage
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I think I finally got my Lunex like ship working (no, it's not for that Lunex Challenge), but I couldn't help but to wonder: would it have been more efficient if I go with the two other methods?

Direct Ascent obviously is most simple in operation, but I ended up with what I considered to be a Nova rocket (AKA: Mammoth with 4x Liquid Booster running with Asparagus Staging, along with an orbiting stage AND a Translunar stage). Had I not run it in sandbox, it would have costed me 350k dollar units!

So what does everyone do for their Mun landing - in career and Sandbox?

Edited by Jestersage
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Moving to Gameplay Questions.

Two comments:

First, they all work pretty well.  There are a lot of ways to design a Mun mission.

Second, if your Mun mission is costing 350K funds or more... holy cow, that's a big ship.  What sort of payload are you landing on the Mun?  Something huge?

I ask because it's not unheard of for a fairly new player to end up designing rockets in a really inefficient way that ends up costing 20 times more than it needs to.  (I'm not exaggerating, I mean literally 20 times.)  A simple land-one-kerbal-on-the-Mun-and-return is doable for a tiny, tiny fraction of that cost.

Can you post a screenshot of your ship?

That said:  When I go to the Mun, it's generally for science, so I'm sending a very small, lightweight science lander.  I have two types of missions.

The first mission (or two) are simple one-shots, done when I'm really early in the tech tree and have tight limits on part count and launchpad mass.  The purpose is to pick up science to boost the tech tree up to the middle tiers.  These missions are typically very cheap four-stage rockets.  Stage 1 is SRB.  Stage 2 is sustainer stage that gets it up to a suborbital trajectory.  Stage 3 circularizes, and gives a decent kick on the way to the Mun.  Stage 4 completes the ejection burn, then lands on the Mun and comes back.  The Mun lander is generally a Mk1 pod, a 2-ton LFO tank, Terrier engine, micro legs, and whatever science instruments I have available.

A little later in the game, when I've got the middle tier of the tech tree reasonably fleshed out and need serious science points to get to the upper tiers, that's when it's time to strip-mine the Mun for science.  That's when I send a bigger mission, which is a science lander with docking port that sits on top of a big orbiting fuel tank.  Put the whole shebang into orbit around the Mun, then the science lander goes down to the surface to a new biome, grabs science, and launches back to orbit to refuel.  Can hit pretty much every biome on the Mun in one shot this way.  I still launch the whole thing in one piece.  When done, the orbiting gas tank stays around the Mun, and only the science lander comes home.

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As usual, Snark has a lot covered but allow me to pipe in really quick:

Mun is actually quite an easy target, fuel-wise. Because of that, leaving an orbiter in space while you go down to land and come back up adds a lot of complications for very little gain. It is extremely likely that the ship that you sent down to land and come back up actually has enough fuel in it to get home, so you could pretty easily redesign the entire mission to just leave out the orbiter, which saves a LOT of money and fuel and logistical thinking.

Now when it comes to going to Duna or other planets, then yes leaving a return ship in orbit becomes a lot better of an idea. But for Mun and Minmus the savings is just not worth the effort. And frequently the savings is so poor it's not a savings at all.

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Jestersage,

 I run a complicated munar rendezvous scheme in career. I use 2 landers, 1 manned and 1 unmanned. These are reset and refuelled between missions. I use a single fuel tank with docking ports (barely qualifies as a station) in munar orbit, and a disposable stack to get me from Kerbin to the Mun and back. This allows me to scour the Mun for surface science very rapidly, keeps my launches small, and allows me to operate cheaply by reusing as much hardware as possible.

 When messing around in sandbox, I usually just go direct ascent. A one shot trip to the Mun doesn't require much.

Best,
-Slashy

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As snark said, it sounds like your ship is vastly overbuilt. Are you using any mods that make launching harder -- RSS or FAR or anything?

The Mun is a sentimental target, but it really is easier to get to Minmus in the early game. It takes a little longer, but it's easier.

Munar landing depends a lot on what tech level you have achieved. A nuke engine can get you there and landed very efficiently. A poodle engine can get you there with lots and lots of fuel left. Lesser tech than that makes for a touchier trip.

In the early game, you want to get science from the Mun. Later, I always go back because I want to mine it for ore and fuel.

But the devil is in the details. How many kerbals do you want to land? My science missions are always for one scientist, and that's it. I use nuclear biome hoppers often -- they are OK. I've tried doing electric powered Mun science rovers. I hated driving the rovers for many reasons.

My current fetish is rocket powered rovers. They can climb the 40 degree slopes that are common on the Mun. They don't need immense solar arrays. They can roll around to visit three or four closely-spaced biomes and then do a suborbital hop to another rich spot for biomes. If they miss a biome by a few meters, they can just roll over to it -- a much more difficult problem for a hopper.

I generally use a direct ascent for my launches. They are easy, save calendar time, and according to me the fuel usage is nearly identical -- and I can use much lighter and less-controllable rockets when launching vertically than if I have to steer and control my speed in atmosphere. If I have a desire to leave a big empty fuel tank in LKO then I do something that looks a little like a gravity turn. But the only rendezvous I ever do is at the very end, when I've come back to LKO. My Mun landers are not built to reenter. I launch an LKO passenger ship and EVA the scientist over to it with all the experiments.

A nuclear science hopper (my latest design):

vWsAmEe.jpg

Edited by bewing
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8 hours ago, Jestersage said:

So what does everyone do for their Mun landing - in career and Sandbox?

In career, as @bewing says, it's a lot easier to pillage Minmus of all science before worrying too much about Mun.  However, various contracts will want you to do a Mun landing before going to Minmus.  So I get that out of the way as quickly and simply as possible, then go right into strip-mining Minmus.  For the initial, obligatory Mun landing, I build a small, light lander that can get itself back home from the Munar suface, and whatever lifter and transfer stage it needs to get it to Mun.  This goes up in 1 piece.  Then it's off to Minmus with another 1-piece lander that's intended to have about 3500m/s left in the tanks when it 1st reaches the surface.  This will allow it to hop to every Minmus biome and get itself home.  It will return with thousands of Science! points, which will put a big dent in the tech tree, and this enables me to design more ambitious stuff.  Then it's a question of whether I finish the tech tree by pillaging Mun or going to Duna.  I don't like Mun very much so I usually go to Duna instead.

In sandbox, I never go to either Mun or Minmus.  It's all about interplanetary, or staying at KSC and blowing stuff up.

Edited by Geschosskopf
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For those who are using refuelling ships and hopping Mun/Minimus, what kind of orbit are you using for the refueller? I've been starting out in a polar orbit so that if I wait long enough, the lander can match inclination easily from biomes that are further away from the equator. After the last or second last refuelling, I put that ship in an equatorial orbit, so that it's easier to rendezvous when I send more fuel from Kerbin. I've been wondering if that's worth the hassle and if I should just work from an equatorial orbit from the beginning.

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21 minutes ago, ClamBoy said:

For those who are using refuelling ships and hopping Mun/Minimus, what kind of orbit are you using for the refueller? I've been starting out in a polar orbit so that if I wait long enough, the lander can match inclination easily from biomes that are further away from the equator. After the last or second last refuelling, I put that ship in an equatorial orbit, so that it's easier to rendezvous when I send more fuel from Kerbin. I've been wondering if that's worth the hassle and if I should just work from an equatorial orbit from the beginning.

I use an equatorial orbit for both, though for different reasons.

For the Mun, it's a big dV saver.  The large majority of the Mun's biomes are either available right smack dab on the equator, or else not far removed from it.  If you're willing to skip the few biomes that are way off the equator, you can get about 80% of the Mun's science value without ever having to do much of an inclination change on your lander.

And actually, I end up not even having to skip 'em.  I like to design my Mun science lander so that it has a few hundred m/s of extra dV buffer, over-and-above what it needs just to get down to the surface and back.  That way, for the easy equatorial landings, it can do a surface-to-surface hop and hit two equatorial biomes before going back to orbit... or instead of doing a hop, it can handle a significant inclination change and hit one of the near-polar biomes.

As for Minmus:  I put it equatorial there, too, but mainly just for convenience.  The dV requirements around Minmus are so low that it really doesn't matter much where you put the thing; a simple science lander can hop all over the place (including the poles, including doing really "punishing" inclination changes) without having to worry much.  So I just put the orbiting tank in an equatorial orbit for the sake of convenience-- it's simpler to do a rendezvous that way, I never have to wait more than one orbit to launch for rendezvous.

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2 hours ago, ClamBoy said:

For those who are using refuelling ships and hopping Mun/Minimus, what kind of orbit are you using for the refueller? I've been starting out in a polar orbit so that if I wait long enough, the lander can match inclination easily from biomes that are further away from the equator. After the last or second last refuelling, I put that ship in an equatorial orbit, so that it's easier to rendezvous when I send more fuel from Kerbin. I've been wondering if that's worth the hassle and if I should just work from an equatorial orbit from the beginning.

For Minmus, I have found that a simple rocket powered rover (with airplane wheels) can do an Elcano (start in the greater flats, go west, and visit every single biome) in half a Minmus day, on half the fuel it takes to do one suborbital hop. This is such a vast improvement that I've completely dropped the concept of hoppers on Minmus. It's easy to get all the way to Minmus, do the complete tour, and get all the way back to LKO on one tank of gas -- no refueling. (I do it twice -- once with a low-tech/minimum-science rover, and then again when I have a full set of science instruments.)

For the Mun, I don't tend to hop around on it until I've got a drill landed. So one or two of my hops are over to the drill to refuel. With an extremely capable rover, I'm pretty sure that every biome is available at the edges of the craters, within 10 degrees of the equator. So equatorial is the way to go with a refueling tanker -- no wasted fuel for inclination changes, and easy to access.

 

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4 minutes ago, bewing said:

For Minmus, I have found that a simple rocket powered rover (with airplane wheels) can do an Elcano (start in the greater flats, go west, and visit every single biome) in half a Minmus day, on half the fuel it takes to do one suborbital hop. This is such a vast improvement that I've completely dropped the concept of hoppers on Minmus. It's easy to get all the way to Minmus, do the complete tour, and get all the way back to LKO on one tank of gas -- no refueling. (I do it twice -- once with a low-tech/minimum-science rover, and then again when I have a full set of science instruments.)

For the Mun, I don't tend to hop around on it until I've got a drill landed. So one or two of my hops are over to the drill to refuel. With an extremely capable rover, I'm pretty sure that every biome is available at the edges of the craters, within 10 degrees of the equator. So equatorial is the way to go with a refueling tanker -- no wasted fuel for inclination changes, and easy to access.

 

Cool approach. Do you have a screenshot or example of that kind of rover? Rovers on Minimus have been more frustrating than helpful for me.

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53 minutes ago, ClamBoy said:

Cool approach. Do you have a screenshot or example of that kind of rover? Rovers on Minimus have been more frustrating than helpful for me.

The low-tech rover: http://www.virtualrealitytoursllc.com/pix/puddle_lt.craft

The high-tech version: http://www.virtualrealitytoursllc.com/pix/nuke_rover.craft

They are fairly easy to launch by hand, but something like MechJeb may give you trouble, perhaps. Puddle is for direct ascent (pure vertical launch) only.

(Woops, I initially posted the wrong version of puddle -- the link has been updated now.)

Edited by bewing
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16 hours ago, Jestersage said:

Direct Ascent obviously is most simple in operation, but I ended up with what I considered to be a Nova rocket (AKA: Mammoth with 4x Liquid Booster running with Asparagus Staging, along with an orbiting stage AND a Translunar stage). Had I not run it in sandbox, it would have costed me 350k dollar units!

As mentioned by others, it sounds like you're over-engineering things a bit. I did my first Mun mission with the .18 demo version; to get a Kerbal on the Mun and back you really don't need more than a handful of FLT-400 and -800 tanks. Actually I do recommend trying that out, as building these bare-bone contraptions can be very educational*.

16 hours ago, Jestersage said:

So what does everyone do for their Mun landing - in career and Sandbox?

I'm really bad at Mun hopping so I usually work from an Orbital station with the lightest lander I can build. For Minmus I work from a orbital station (I'll need that for refueling anyway) but you can easily cover all biomes in one or two landings and hopping around.

 

* And I'm sure someone will now point out that they went to the Mun and back on nothing more than a pilot command seat, FLT-200, an Ant engine and a Flea booster. After the obligatory Eve landing of course.

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In early career, I just send the bare minimum for completing the first contracts. If I need science, I go to Minmus, or other celestial bodies (you can get an enormous amount of science with Surface samples or the Science Jr.)

However around the end of career I like to gather all the available science, so I send a ionic hoper to, Mun, Minmus, Gilly, Ike, Bop and Pol.

Here's my Mun hoper :

1467767849-ionic-hoper.jpg

It does have a low TWR (1.7) so you need to know the constant-altitude landing technique, but it's super light (6 tons) and it have a lot of dV (10 000 m/s), so I only need to refuel it once. I leave my station in an equatorial orbit, and while I do my hops I keep an equatorial biome in stock so it is the last one I do before going back up to the station.

Edited by Tatonf
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This all depends on what you're lifting up there.  I'm assuming that since you need 350K dollar units to get up there... sheesh that thing must be heavy, or else you're just being excessive.  I approve of excessive but that takes it to a new level.

I normally use a small, simple lander with four thud engines and a small rockomax engine, gets 3 people on the mun and can get them back if you do it right.

second stage is a medium rockomax engine, used to supplement orbit and for munar injection.

First/Orbital stage is an orange tank with a medium rockomax beneath it, and 3-4 LVT 3-tank rocket boosters.

This works every time for me.  Good Luck!

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13 hours ago, ClamBoy said:

For those who are using refuelling ships and hopping Mun/Minimus, what kind of orbit are you using for the refueller? I've been starting out in a polar orbit so that if I wait long enough, the lander can match inclination easily from biomes that are further away from the equator. After the last or second last refuelling, I put that ship in an equatorial orbit, so that it's easier to rendezvous when I send more fuel from Kerbin. I've been wondering if that's worth the hassle and if I should just work from an equatorial orbit from the beginning.

With Minmus, you don't need a refueling ship.  Once you have 2.5m tanks, you can make a lander out of one of the mid-sized 2.5m tanks, maybe with the pancake as well, load it down with all your experiments and the 1-seat lander can, and power it all with a Poodle.  If you can get this to the surface with a minimal use of fuel (say by using a crasher stage for most of the descent), then it can hit all 9 biomes and get home by itself with a margin of safety.

For Mun, you have 2 choices, eirher orbital refueling or self-refueling.  Surface bases only work if you've got lots of them so you don't have to keep backtracking so much, and if you've got lots of them, then you probably have already pillaged Mun anyway.  And self-refueling landers require some fairly high tech themselves, so you might not have all that when you're heading out to pillage Mun.  And they're big and somewhat top-heavy.  But OTOH, they're cheaper and easier than flying a huge fuel tank out to Mun.  Still, odds are you'll probably need a big orbital fuel tank.

You want to put the orbital fuel tank in non-synchronous polar orbit so that eventually it will pass over every biome on Mun.  Then it's just a matter of dropping onto a biome ahead, quickly grabbing the Science!, and immediately coming right back up because the tank won't pass over that spot of ground again for many days.  The number of such hops you can do is limited by the size of the tank, but you can always fly more fuel out if you need it before bringing the data home.

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I've done it all three ways in different campaign games.  :D

I was pleased with myself when I finally cracked the code of how to do an Apollo-style single-launch LOR mission profile in my current campaign.  The solution was to have a decoupler/low-profile adapter/decoupler "interstage" with the lower decoupler facing "down" and linked up with the LM-analogue's docking port.  (It needs to be strutted to avoid significant flexing, of course).  It generally floats clear of the docking zone before I get the CSM flipped around to dock, but sometimes I need to bump a piece out of the way (I considered fitting Separatrons but decided that would be overkill).  You just have to be careful of the staging sequence, or use action groups to control it.

In my prior (1.0.5) campaign, I did multiple launches (LM in one, CSM in another) and docked them before Munar transfer.

The first time around, I did direct ascent, since basically all that needs is more boosters!  But not as elegant IMHO.

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I have almost always done a Munar orbit rendezvous. Indeed I've almost always done destination orbit rendezvous *where-ever* I am landing. It just to me felt obvious and natural, I suppose because that's how Apollo did it.

But in KSP Direct Ascent to the Mun is very possible, indeed maybe better.

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For Mun, I could heartily recommend combined technique: go for polar biomes with simple direct ascent missions, use the science gathered to build reusable lander and support station in equatorial orbit and harvest everything else. For orbit, I prefer 30x30km. It's low enough to not waste much fuel, high enough for 100x timewarp and transfer from 10x10km parking orbit can be done on rcs alone.  Downside is that "lower" orbits are not that much lower so phasing may take hours (on 50x timewarp) if you miss transfer window.

As for direct ascent efficiency, I don't see it as straightforward as others would have it. Direct ascent waste fuel by hauling stuff down and back up the well, so it depends on how much weight that is. For simple science mission with small pod, that would be small heatshield, tiny chute and little bit of fuel - negligible, yes. But if you take tourists on a ride in mk3, well, XL parachute and 160kg of ablator add up to almost a ton of dead weight, plus a lot more fuel.
 

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The reason for this insanity is that:

  1. While technically the 2nd Munar mission (doing the base is the first Munar mission), I am trying to do a rescue mission around orbit, land the thing near the First base, do a shift change (should I change the scientists?), and then take them back to Kerbin for experience and rewards.
  2. I was trying to launch a Lunex type ship (In fact someone actually created a challenge), aka using a direct ascend with lifting body return capsule. Due to point one, it actually have extra crew cabin for a total of six Kerbals. If it's just reaching the Mun, Technically you can do it with the stock PT Munsplorer
  3. Realized that having 2 Nuclear Battery and 2 NERVAs are expensive. My H2/LOX version using aerospike and poodle cost me only 250k
Edited by Jestersage
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12 hours ago, Jestersage said:

The reason for this insanity is that:

  1. While technically the 2nd Munar mission (doing the base is the first Munar mission), I am trying to do a rescue mission around orbit, land the thing near the First base, do a shift change (should I change the scientists?), and then take them back to Kerbin for experience and rewards.
  2. I was trying to launch a Lunex type ship (In fact someone actually created a challenge), aka using a direct ascend with lifting body return capsule. Due to point one, it actually have extra crew cabin for a total of six Kerbals. If it's just reaching the Mun, Technically you can do it with the stock PT Munsplorer
  3. Realized that having 2 Nuclear Battery and 2 NERVAs are expensive. My H2/LOX version using aerospike and poodle cost me only 250k

Still having trouble picturing why your mission needs to cost hundreds of thousands of funds, instead of a tenth of of that.  Could you post a screenshot of your ship?

Also, regarding point #3, you're using some non-standard KSP terminology ("NERVA" rather than "NERV"; "H2/LOX" rather than "LFO"; "Nuclear Battery" rather than "RTG").  Just to be clear:  are you running some mod?  Or are you talking about stock parts?  Just want to make sure we're not talking at cross-purposes here.  :)

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4 hours ago, Snark said:

Still having trouble picturing why your mission needs to cost hundreds of thousands of funds, instead of a tenth of of that.  Could you post a screenshot of your ship?

Also, regarding point #3, you're using some non-standard KSP terminology ("NERVA" rather than "NERV"; "H2/LOX" rather than "LFO"; "Nuclear Battery" rather than "RTG").  Just to be clear:  are you running some mod?  Or are you talking about stock parts?  Just want to make sure we're not talking at cross-purposes here.  :)

My Standard LF/O version. 216k Untested.
My NERV version. 350k Tested to be working

Both versions come with a Lunar Rover in Service Bay.

Not running any mods. I prefer to call them with the Earth Terms :P

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Sidenote: I managed to make my Saturn V analogue cost 405K o_O

My guess is that most of the cost is due to the Kerbodyne parts, which I considered to be the analogue to the Saturn V/Nova parts. I noticed that if I use Rockomax parts instead, my "saturn V" price dropped to 320k.

Anyway, You will notice I have change the title, because I want to expend this to the next logical step:

  1. Aside from Mun and Minmus, Can Direct Ascent allow me to land directly on them? What about just orbiting? (I assume I can do flyby with NERV only)
  2. For the other planets, when to use Kerbin Rendezvous (assemble ship in Kerbin orbit) only? Target rendezvous only? 
Edited by Jestersage
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Well, all my rockets are much smaller and less expensive than yours, but I always start out using direct ascent for landing on both Mun and Minmus. For Minmus, it's easy to do with just a Poodle engine. For the Mun, I use a single NERV engine.

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On 07.07.2016 at 10:43 PM, Jestersage said:

My Standard LF/O version. 216k Untested.
My NERV version. 350k Tested to be working

First link doesn't go anywhere.

For the second one, it's hard to tell from a picture, but my guesstimates is it's around 20 tons of a lander, that needs to go to low mun orbit and can go to the surface and home from there. If that's correct, than the entire ship should be around 100-150k(depending on contents of cargo/service bay). Your lifter looks like a huge overkill for that payload.

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