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JackBush

Never enough fuel ...

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I've been experimenting with ships with 2 and 3 Science Jrs in the pod that carries 3 scientists. (I always get rid of the pilot and engineer. I don't need them since I'm playing science mode (1.05)). And with ships that have almost no science or, in the case of the last one, none. No matter how simple I make them, I always end up getting into my lander fuel to complete my orbit and make the Hohman Transfer, etc. This of course leaves no fuel to get back. If I add more fuel and engines in stages, the same thing happens. It seems a vicious circle. And for those of you  who have been following my painful attempts to garner science from Mun, I must seem an idiot. I have no idea how people manage to get 3 Science labs up there and then hop around the biomes. Now and then I can get to one and bring back a few science points but nothing substantial. I despair.

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So, first of all, if you've got scientists, why the dickens are you carrying more than one Science Jr.?  Just re-use the same one over and over again.  And for that matter, why do you need to have three scientists?  There's no point in having more than one scientist unless you've got a science lab, in which case you only need 2.  And you certainly wouldn't want to go biome-hopping with a lab.

But the real mass hog is that 3-kerbal pod.  It's crazy-stupid heavy.  The dang thing weighs over four tons, i.e. nearly 1400 kilograms per kerbal, compared with just 500 kg/kerbal for the Mk1 crew cabin, 600kg for the Mk1 lander can, or 800kg for the Mk1 command pod.  It really ought to have its mass seriously reduced, IMHO.  Yes, it "looks cool", and maybe it's okay for use on great big massive ships where the command pod is only a small fraction of the total ship mass.  But for landers, it's just incredibly un-economical.

So I'd say that likely you have two problems:  1. your payload's too heavy, and 2. you may be suffering problems from mathematically inefficient staging.  However, it's hard to give concrete advice unless we know what it is you're trying to accomplish.

Could you describe exactly what you're trying to accomplish (i.e. the purpose of the mission, and your assumed parameters), perhaps accompanied with a screenshot?

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Yup, you only need the one scientist so you really only need the 1-man pod or lander can.  You'll have to do an EVA to collect the data from the Science Jr. and other instruments. 

Here's a basic "standard model" 1-man ship/lander combo (the pod and science package separates for re-entry) using the Mk 1 pod:

JuyFLJL.png

As you can see from the Kerbal Engineer Redux readout (a must-have mod if you get nothing else), it has over 4200 m/s of delta-V.  That's enough to get to the Mun and orbit, land, do a short hop or two to another biome, get back into oribit and return to Kerbin.  Build a rocket to get it into orbit; if you have the 2.5m parts in the tech tree then it will be easy, just use the orange tank as a core and add appropiate engines and radial boosters/SRBs.  You should be able to send the ship to the Mun and even into Munar orbit without using any of its own fuel, thus extending your surface time.

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Ok.  I don't think I've ever played science, except back when it was called career, but what do you need 3 science jr.s for?  A single scientist can collect the data and reset a science jr making it able to be reused.  There is no need to have more than one with a scientist aboard.  

It sounds like you're confronting the tyranny of the rocket equation- needing more fuel which requires more fuel to lift, requiring more fuel and so on..  Perhaps you could post a screenshot so we can help you out.

Edited by Aethon

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38 minutes ago, Snark said:

The dang thing weighs over four tons, i.e. nearly 1400 kilograms per kerbal, compared with just 500 kg/kerbal for the Mk1 crew cabin, 600kg for the Mk1 lander can, or 800kg for the Mk1 command pod.

Wow, I never realized it was that bad. I need to rethink my landers....

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1 hour ago, Snark said:

So, first of all, if you've got scientists, why the dickens are you carrying more than one Science Jr.?  Just re-use the same one over and over again.  And for that matter, why do you need to have three scientists?  There's no point in having more than one scientist unless you've got a science lab, in which case you only need 2.  And you certainly wouldn't want to go biome-hopping with a lab.

But the real mass hog is that 3-kerbal pod.  It's crazy-stupid heavy.  The dang thing weighs over four tons, i.e. nearly 1400 kilograms per kerbal, compared with just 500 kg/kerbal for the Mk1 crew cabin, 600kg for the Mk1 lander can, or 800kg for the Mk1 command pod.  It really ought to have its mass seriously reduced, IMHO.  Yes, it "looks cool", and maybe it's okay for use on great big massive ships where the command pod is only a small fraction of the total ship mass.  But for landers, it's just incredibly un-economical.

So I'd say that likely you have two problems:  1. your payload's too heavy, and 2. you may be suffering problems from mathematically inefficient staging.  However, it's hard to give concrete advice unless we know what it is you're trying to accomplish.

Could you describe exactly what you're trying to accomplish (i.e. the purpose of the mission, and your assumed parameters), perhaps accompanied with a screenshot?

I didn't realise I could get away with the Mk-1 pod and one scientist. I won't post  a screen because I don't  have one I'm even close to satisfied with (as you can guess from the initial post). BUT I can tell you precisely what I want to accomplish. I want to orbit Kerbin, first of all, then go to Mun. I want a lander that will get me down so my scientist (I will never again take more than one, nor more than one Science Jr; you guys have gotten that through to me) can gather up as much science as possible. As others have talked about hitting more than one biome on a mission, I thought that would be good. So I'd need sufficient fuel to land, get science, take off and go, say 25 kms away, gather up some more, and have enough fuel to get into a Munar orbit and come home. So: how do I do that?

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F296894B0B875014B01488CB0E88DE1E82F7A897

 

Don't rule out a small science rover.  If landed in a spot near several biomes (and the boundary between them, which usually turns out to be an exotic biome) you can get quite a science haul, more than a single manned lander.  This one still has the skycrane attached for reasons, but it has Tarsier technologies Chemcam on it, and all the stock science experiments that will work landed without an atmosphere, except the Science Jr.  It also a has a mystery goo which is good for one shot only.  Sure it only gets transmission value, but it's small, light, easy to ship through space, and can rove to different biomes.  I think this one returned over 3000 science.

Edited by Aethon

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39 minutes ago, JackBush said:

I didn't realise I could get away with the Mk-1 pod and one scientist. I won't post  a screen because I don't  have one I'm even close to satisfied with (as you can guess from the initial post). BUT I can tell you precisely what I want to accomplish. I want to orbit Kerbin, first of all, then go to Mun. I want a lander that will get me down so my scientist (I will never again take more than one, nor more than one Science Jr; you guys have gotten that through to me) can gather up as much science as possible. As others have talked about hitting more than one biome on a mission, I thought that would be good. So I'd need sufficient fuel to land, get science, take off and go, say 25 kms away, gather up some more, and have enough fuel to get into a Munar orbit and come home. So: how do I do that?

That shouldn't be too hard.  I'll assume you have a reasonable tech level (specifically:  you have probe cores available, and batteries, and solar panels, and fuel ducts, and a reasonable assortment of fuel tanks).

Short biome hops on the order of 25 km aren't too bad, just pack an extra few hundred dV.  For short hops (where you can approximate the surface as being flat, and gravity as constant), the distance traveled in a hop is (v2sin2θ)/g, where v is the burn amount, θ is your angle above horizontal, and g is local gravity.  Greatest distance traveled is for θ = 45 degrees, where the distance will just be v2/g.  So for a 25 km hop on the Mun where g = 1.63 m/s2, you'd need a burn of 200 m/s.  And you have to do that twice, of course (once to takeoff and once to land), so that's 400 m/s for the hop.

@Laguna's post shows a pretty decent lander, though if I'm reading that correctly there's no probe core on it so you'd have trouble flying it with a scientist.

Here's another example of a fairly flexible go-to-the-Mun, do-one-biome-hop, fly-home lander:

VmFjlFB.png

This little guy packs a bit over 3100 m/s of dV in a 5.6-ton package.  Munar escape velocity is 800 m/s, so that's enough to arrive at the Mun, circularize in low munar orbit, land, do a short hop, take off, and head home again with a reasonable amount of dV to spare.  So all you need is a booster stage that can get it to LKO, plus 850 m/s to send it Munwards from LKO, and you're good to go.

Note that I haven't bothered putting fuel ducts on it.  That saves 200 kg of mass.  The 1-ton tank is plenty for doing any of the burns you'll need on this mission, so all you need to do is transfer fuel from the Oscars to top off the central tank each time.

I also haven't bothered putting a decoupler below the heatshield.  More unnecessary mass.  Just head home and enter atmosphere engine-first, and let the engine & fuel tanks explode when they overheat.  I've reduced the ablator on the heatshield to just 25% of a full load, that should be plenty.  I've shown it with an OKTO assuming low tech level; if you can manage to swap out a HECS instead, it'll be nicer for landing since you can just tell it to hold retrograde.

It's not aerodynamic at all, but it is fairly compact radially, so it's pretty easy to put a fairing around it.

Make sure you have good landing and takeoff technique on the Mun-- efficient vacuum landings take some practice, it's easy to be wasteful of dV.  So if you haven't done a lot of Mun landings before, be sure to quicksave in Mun orbit before you try landing, so you can practice.  And if you need advice on the topic, just ask.  :)  (Or search this forum for the term "suicide burn.")

Edited by Snark

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I've built Laguna's lander and, because I'm in science mode, I can fly it with a scientist rather than a pilot. what I really need help with is what goes below the lander. What gets the whole shebang into K orbit, then through the Hohman transfer, and then into a Munar orbit. From there, I know what needs to be done. I'll just F5 a lot!

But if you could spell out or show me a launcher for this thing, I'd be a happy person. 

As an aside, Snark, you use the term LFO tanks and I'm not sure which they are. Is that what Laguna's using in his lander?

Your lander looks neat. I'll try it one day.

1 hour ago, Laguna said:

Yup, you only need the one scientist so you really only need the 1-man pod or lander can.  You'll have to do an EVA to collect the data from the Science Jr. and other instruments. 

Here's a basic "standard model" 1-man ship/lander combo (the pod and science package separates for re-entry) using the Mk 1 pod:

JuyFLJL.png

As you can see from the Kerbal Engineer Redux readout (a must-have mod if you get nothing else), it has over 4200 m/s of delta-V.  That's enough to get to the Mun and orbit, land, do a short hop or two to another biome, get back into oribit and return to Kerbin.  Build a rocket to get it into orbit; if you have the 2.5m parts in the tech tree then it will be easy, just use the orange tank as a core and add appropiate engines and radial boosters/SRBs.  You should be able to send the ship to the Mun and even into Munar orbit without using any of its own fuel, thus extending your surface time.

Thanks for the lander, Laguna. I'll try it. You have a couple of science things on the front of the Science Jr I don't have. I have the barometer and thermometer and of course the Mystery Goo. But the other two little gizmos I don't recognise.

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Biome hopping on the Mun can be pretty tough- You need quite a bit of fuel to do more than a couple (unlike Minmus, you can stay there all day).

I second using 2.5m parts to get there, they make it pretty easy. I find using a beasty rocket to get into orbit, a poodle powered second stage to get to the Mun and Mun orbit, then the lander on top works well- sometimes the poodle stage has enough juice left to help with the first landing. Also a 1-star pilot can be pretty handy for holding retrograde during landing, my crew early on is almost always a pilot and scientist.

Edited by Waxing_Kibbous

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2 hours ago, Snark said:

But the real mass hog is that 3-kerbal pod.  It's crazy-stupid heavy.  The dang thing weighs over four tons, i.e. nearly 1400 kilograms per kerbal, compared with just 500 kg/kerbal for the Mk1 crew cabin, 600kg for the Mk1 lander can, or 800kg for the Mk1 command pod.

Nothing to really contribute, but it's horribly embarrassing how long it took me to realize this myself - like 6 months or so. I just though it looked so dang cool that I plopped it on everything and wondered why my fuel bill was so high. Sigh.

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9E8F6B220C9A1F91554C3B28964D0BF9C5079302

 

I have a similar lander.  A three legged stool never wobbles.  Note the probe core in the service bay

 

95064589AAA4B8F65EDF167B9270F723241C14A1

 

Here's the lifter with the fairing removed.  Standard stock solids all around.  The main stack is powered by a skipper.

 

LFO means Liquid fuel and oxidizer tanks, as opposed to just Liquid fuel (LF).

Edited by Aethon

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31 minutes ago, JackBush said:

As an aside, Snark, you use the term LFO tanks and I'm not sure which they are.

LFO (Liquid Fuel & Oxidizer) are the rocket fuel tanks, as opposed to LF which are the 'jet fuel' tanks packing only Liquid Fuel.

1 hour ago, Snark said:

Here's another example of a fairly flexible go-to-the-Mun, do-one-biome-hop, fly-home lander:

Just one comment, Snark: it's a tad on the high side and prone to tip over, especially for someone still practicing landings in vacuum on bodies that may have very sloped ground. A bit wider at the base may be advisable for extra stability (and will still fit in a fairing).

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59 minutes ago, JackBush said:

I've built Laguna's lander and, because I'm in science mode, I can fly it with a scientist rather than a pilot. what I really need help with is what goes below the lander. What gets the whole shebang into K orbit, then through the Hohman transfer, and then into a Munar orbit. From there, I know what needs to be done. I'll just F5 a lot!

Ah, gotcha.

Booster needs to be tuned to the payload mass, obviously.  For example, Laguna's lander is 14 tons, whereas mine is just 5.6 tons, so you'd need more rocket to launch Laguna's lander than you would mine.  (Not 2.5 times more, since Laguna's lander packs a lot more dV than mine does.)

If you play KSP a lot, you'll get into the habit of developing a family of "standard" booster assemblies in various sizes, i.e. "this is my standard booster for 30-ton payloads to LKO", etc.

There are a lot of options here.  Which makes the most sense depends on what you've got unlocked thus far.  For example, do you have the Skipper yet (and the 16-ton LFO tank to go with it), or do you need a solution built on Swivels?

If you have the Skipper, then here's a reasonable booster for the little 5.6 ton lander I posted earlier:

by1XPmy.png

(This puts the lander in a fairing).  Actually, for the sake of aero stability, you should probably mount the SRBs quite a bit lower down on the center tank than I've shown here, but it's flyable as shown.

From the top down, the core booster is:  a 1.25m decoupler (hidden inside fairing); a 1.25m fairing base; reaction wheel; 1.25m-to-2.5m adapter; 16-ton LFO tank; Skipper.  Eight Thumper SRBs radially attached in two groups of four.  SRB group A is set to 80% thrust; group B is set to 50%.  Total mass on the pad, 89.3 tons. TWR is 1.5.  Total cost, 42K funds.

Staging setup is:

  1. activate all eight SRBs
  2. jettison SRB group A
  3. jettison SRB group B, activate Skipper
  4. pop fairing
  5. fire the stack decoupler & activate lander's Terrier
  6. parachute

The above setup has enough dV to get to LKO and do the 850 m/s Munar transfer burn, with about 120 m/s of dV left in the big Skipper tank, which you can use towards circularizing upon arrival at the Mun.

Note that this is for my little lander-- if you want to launch Laguna's, you'd need more oomph.

 

59 minutes ago, JackBush said:

As an aside, Snark, you use the term LFO tanks and I'm not sure which they are. Is that what Laguna's using in his lander?

Whoops, sorry about the jargon.  You'll see the term come up a lot in the forums.  LFO means "liquid fuel + oxidizer", i.e. all the "rocket" tanks.  As distinguished from the fuel tanks that hold liquid fuel only (with no oxidizer), i.e. "LF tanks" as opposed to "LFO"; those are the ones you use for jet engines and nukes.

 

59 minutes ago, JackBush said:

I have the barometer and thermometer and of course the Mystery Goo. But the other two little gizmos I don't recognise.

The other two gizmos are the seismograph and the gravioli detector-- you'll get those higher up the tech tree.

 

By the way... if you have patched conics unlocked, have you considered going to Minmus first instead of the Mun?  Even without biome hopping, it's considerably cheaper in terms of dV... and once you start biome hopping, it's a lot cheaper.  You need only a tiny fraction of the fuel to do a hop; the same lander that would let you do one biome hop on the Mun could do many such hops on Minmus.  Also, if you're new to vacuum landing, Minmus' lower gravity is a lot more forgiving-- things happen more slowly, you have a lot more time to correct mistakes.  It's good practice for going to the Mun later.  Plus Minmus has lots of nice flat areas to land on.

Edited by Snark

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1 hour ago, JackBush said:

Thanks for the lander, Laguna. I'll try it. You have a couple of science things on the front of the Science Jr I don't have. I have the barometer and thermometer and of course the Mystery Goo. But the other two little gizmos I don't recognise.

Yeah, I guess it's a bit more than a "basic" model, it's the higher trim level with more options. :)  The other two instruments are the negative gravioli detector and the seismic accelerometer.

All the really huge craters on the Mun are a separate biome and they're surrounded by Highlands and/or Midlands biomes. So all you have to do is land in one of those big craters then jump outside it, then maybe to another big crater, and you'll have visited three biomes just like that.

1 hour ago, Aethon said:

95064589AAA4B8F65EDF167B9270F723241C14A1

 

Here's the lifter with the fairing removed.  Standard stock solids all around.  The main stack is powered by a skipper.

 

LFO means Liquid fuel and oxidizer tanks, as opposed to just Liquid fuel (LF).

Heh, I quickly built something similiar for a lifter. :)

ptI2uEP.png

https://imgur.com/a/KLkl6

(For some reason inserting the Imgur album here was resulting in low-res versions of the pictures, so here's the direct link to the album with launch pictures)

Also uses a Skipper, Poodle and 4 Thumper SRBs.  Probably could of put a larger tank with the Poodle to send the lander all the way to the Mun, now it just gets into Kerbin orbit with about 160 DV left.

Edited by Laguna
Pictures in the album got downgraded to low-res.

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35 minutes ago, swjr-swis said:

Just one comment, Snark: it's a tad on the high side and prone to tip over, especially for someone still practicing landings in vacuum on bodies that may have very sloped ground. A bit wider at the base may be advisable for extra stability (and will still fit in a fairing).

Yeah, a bit.  However, it's better than it looks; the CoM is lower than you'd think.  Most of the mass is down in the fuel tanks (those Oscars are a lot heavier than they look; that's 2.4 tons of fuel mass down there), so it's actually not too bad.  If you're willing to spend a bit of extra mass on a bigger fairing, you can mount the legs on the radial fuel tanks instead of the central tank to give it a wider stance.

The point about beginners at vacuum landings is well taken.  It's why I usually recommend folks to start with Minmus first: makes much more sense than the Mun.  Lots of nice flat places to land.  Much more forgiving dV requirements.  Everything happens in super slow motion so you have plenty of chances to tinker with your landing.  And if worst comes to worst and you crash your ship, a kerbal in a spacesuit can go all the way home to Kerbin from the surface using only EVA thrusters.  (Though they'd need someone to come up and rescue them before they hit atmosphere and fry.)

Edited by Snark

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11 hours ago, JackBush said:

... As others have talked about hitting more than one biome on a mission, I thought that would be good. So I'd need sufficient fuel to land, get science, take off and go, say 25 kms away, gather up some more, and have enough fuel to get into a Munar orbit and come home. So: how do I do that?

As others have mentioned, if you're not very experienced (at landings, anyway), you may want to consider a minmus mission instead.  There are some different challenges - you'll need to launch into a different plane, and your injection burn will be much, much bigger... 

... But Minmus's gravity is sooo low, that assuming you can get there, you'll have a much easier time of it - for a start you don't even need a traditionally shaped (e.g. with legs) to safely land on minmus, and even if you do topple over on landing, depending on your ship, you may find you can right it with the reaction wheels alone. Finally, and the kicker, is that the gravity is so low, you'll be able to hit much more than just two biomes.   Minmus is so easy to land and return from, that, eventually, it's well worth sending a mothership/lander combo to it - I think my 'grasshopper' lander can land (or take off, can't remember which, it's been a while) entirely on the RCS thrusters it uses for docking, and barely uses the 'spark' engine it has except for circularising it's orbit and the deorbit burn arround minmus.

Wemb

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12 hours ago, Laguna said:

[...]

Here's a basic "standard model" 1-man ship/lander combo (the pod and science package separates for re-entry) using the Mk 1 pod:

[pic of 4,200 m/s dv lander weighing 14.4 tons]

Just for fun, I decided to recreate something with the same capabilities using the 3-man command pod.

Spoiler

 

2UwOz1D.png

Although I hadn't noticed that there was a ladder on the original, so that's one mistake. You have to jet-pack off this one, while avoiding the solar panels.

So from 14.4 tons the total goes up to 44 tons. Although the thrust-to-weight ratio is listed at 0.58 (compared to the original's 2.6), that's because I didn't change the setting from Kerbin to the Mun, so it is actually higher (more like 3.5).

It isn't that much more expensive, but that's because the main cost of the lander itself comes from all the experiments it is carrying. The cost of the lifter to get it up to orbit, on the other hand, will be significant.

 

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1 hour ago, Wemb said:

As others have mentioned, if you're not very experienced (at landings, anyway), you may want to consider a minmus mission instead.  There are some different challenges - you'll need to launch into a different plane, and your injection burn will be much, much bigger...

Actually, the injection burn is almost the same size.  From LKO, it only takes about 50 m/s more to raise your apoapsis to Minmus as it does to the Mun.  And it requires considerably less dV to circularize on arrival.  The fact is, from LKO, it's actually around 200 m/s cheaper to get to low Minmus orbit than it is to get to low Mun orbit!  And that's just to orbit-- once you consider landing, then hopping etc., the savings just keep mounting up.

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10 hours ago, Laguna said:

Yeah, I guess it's a bit more than a "basic" model, it's the higher trim level with more options. :)  The other two instruments are the negative gravioli detector and the seismic accelerometer.

All the really huge craters on the Mun are a separate biome and they're surrounded by Highlands and/or Midlands biomes. So all you have to do is land in one of those big craters then jump outside it, then maybe to another big crater, and you'll have visited three biomes just like that.

Heh, I quickly built something similiar for a lifter. :)

ptI2uEP.png

https://imgur.com/a/KLkl6

(For some reason inserting the Imgur album here was resulting in low-res versions of the pictures, so here's the direct link to the album with launch pictures)

Also uses a Skipper, Poodle and 4 Thumper SRBs.  Probably could of put a larger tank with the Poodle to send the lander all the way to the Mun, now it just gets into Kerbin orbit with about 160 DV left.

 

10 hours ago, Laguna said:

Yeah, I guess it's a bit more than a "basic" model, it's the higher trim level with more options. :)  The other two instruments are the negative gravioli detector and the seismic accelerometer.

All the really huge craters on the Mun are a separate biome and they're surrounded by Highlands and/or Midlands biomes. So all you have to do is land in one of those big craters then jump outside it, then maybe to another big crater, and you'll have visited three biomes just like that.

Heh, I quickly built something similiar for a lifter. :)

 

https://imgur.com/a/KLkl6

(For some reason inserting the Imgur album here was resulting in low-res versions of the pictures, so here's the direct link to the album with launch pictures)

Also uses a Skipper, Poodle and 4 Thumper SRBs.  Probably could of put a larger tank with the Poodle to send the lander all the way to the Mun, now it just gets into Kerbin orbit with about 160 DV left.

Thanks Laguna and Aethon for your helpful suggestions. Much appreciated.

1 hour ago, Wemb said:

... But Minmus's gravity is sooo low, that assuming you can get there, you'll have a much easier time of it - for a start you don't even need a traditionally shaped (e.g. with legs) to safely land on minmus, and even if you do topple over on landing, depending on your ship, you may find you can right it with the reaction wheels alone. Finally, and the kicker, is that the gravity is so low, you'll be able to hit much more than just two biomes.   Minmus is so easy to land and return from, that, eventually, it's well worth sending a mothership/lander combo to it - I think my 'grasshopper' lander can land (or take off, can't remember which, it's been a while) entirely on the RCS thrusters it uses for docking, and barely uses the 'spark' engine it has except for circularising it's orbit and the deorbit burn arround minmus.

Wemb

I've landed  on Minmus and you might be right about it being a better place for awhile. I plan to do both now. Thanks.

8 minutes ago, Snark said:

Actually, the injection burn is almost the same size.  From LKO, it only takes about 50 m/s more to raise your apoapsis to Minmus as it does to the Mun.  And it requires considerably less dV to circularize on arrival.  The fact is, from LKO, it's actually around 200 m/s cheaper to get to low Minmus orbit than it is to get to low Mun orbit!  And that's just to orbit-- once you consider landing, then hopping etc., the savings just keep mounting up.

Okay, I think you guys have sold me on going to Minmus first, until I get really good. I thought the science was richer on Mun, though. 

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11 hours ago, Waxing_Kibbous said:

I second using 2.5m parts to get there, they make it pretty easy.

A number of people have mentioned 2.5m parts. I've looked pretty carefully at the parts I have available and don't find any reference to 2.5m. What is it, please?

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The Rockomax parts (the size of the bottom of the 3-man Mk1-2 pod) are 2.5m. The bottom of the single command pod, and the top of the 3-man pod, are 1.25m.

You should have the first two heatshields by now, in 1.25m and 2.5m sizes. Next up is (iirc) 3.75m.

From those diameters, you can see that a Kerbal is a very small creature, about 0.75m tall (2'5.5" according to the wiki).

Edited by Plusck

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As for Mun vs Minmus, there is more science to be had on the Mun (more biomes), and the multiplier is slightly higher too, but the ease of getting the science on Minmus means it's easier to pick up a given number of points from a single mission.

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17 minutes ago, JackBush said:

A number of people have mentioned 2.5m parts. I've looked pretty carefully at the parts I have available and don't find any reference to 2.5m. What is it, please?

The diameter.  KSP parts come in four sizes:

  • 0.625m.  These are the little bitty ones, like the Oscar tank, and the Spark engine.
  • 1.25m.  Lots of parts here, it's what you start out with.  The Mk1 command pod.  The first few fuel tanks you get.  The Swivel and Terrier engines.
  • 2.5m.  The 8, 16, and 32 ton tanks.  The Poodle, Skipper, and Mainsail engines.
  • 3.75m.  The big black-and-white Kerbodyne tanks.  The Mammoth and Rhino engines.
9 minutes ago, JackBush said:

Here are my pod, fuel tank, and engine availabilities:

http://imgur.com/a/dmc3p

Very nice and helpful screenshot!  Yes, you've got plenty of selection there, in both the 1.25m and 2.5m sizes.  Specifically, you have all the parts you need either for my booster or Laguna's.  You're good to go.

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1 hour ago, Snark said:

Actually, the injection burn is almost the same size.  From LKO, it only takes about 50 m/s more to raise your apoapsis to Minmus as it does to the Mun.  And it requires considerably less dV to circularize on arrival.  The fact is, from LKO, it's actually around 200 m/s cheaper to get to low Minmus orbit than it is to get to low Mun orbit!  And that's just to orbit-- once you consider landing, then hopping etc., the savings just keep mounting up.

Oh  - looking at the map - yes, you're quite right -  Okay - that's a surprise - It feels like it's a lot more - well, in that case, he should certaily go to minmus - he'll be able to do a lot more with the fuel once he gets there, though his lander's engine will probably be grossly overpowered

Wemb

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