Small Mun lander that can land and relaunch to dock in Mun orbit

[keyscapeunit]

Hi, I'm looking for advice on a small fuel efficient Mun lander that can make trips from an orbiting lab down to the surface and back.  I have one (screenshots below) but it seems rather large and uses up quite a bit of fuel to get down and back (over half of the three tanks).  Any advice appreciated!!

 

[FlyingPete]

That lander is huge! You don't need anything like that size to get from Munar orbit, to the surface, and back again.

Here's one I built a while ago that works well:

For clarification, that's a materials bay experiment under the Mk1 Lander Can. The engine beneath it is a LV-909, and it's fed by three FL-200 tanks, attached radially and connected by fuel lines to the engine. Under each fuel tank is a small battery. I think I just used the lander can's internal supply of monopropellant, but some extra is always useful and gives you more leeway for rendezvous and docking with the space station.

[Plusck]

I wonder if it is actually possible to be much more efficient.

I have a tiny lander - with half that much fuel and just chairs to sit in - but it can only just go down and back up with about a third of the fuel left. No dotting around possible.

The other option is to go really heavy - LV-N and 6 or 8 mk1 fuel tanks to act as legs and put some distance between the ground and the top of the engine. That lets you stop in several places but it is slow, sluggish and not much fun.

 

edit: oh wait no - I didn't look closely enough at your pic - so I thought it was mk1 size. I use a fraction of that fuel - but it doesn't really improve efficiency greatly.

Edited December 18, 2015 by Plusck

[Fisk02]

Try making a lander with multiple stages, similar to the Apollo lander or the Lunniy Korabl lander. Or is that a multiple staged lander? hard to see, but i don´t think so.

Dont forget to leave any empty tanks on the mun surface. 

[keyscapeunit]

3 minutes ago, Fisk02 said:

Try making a lander with multiple stages, similar to the Apollo lander or the Lunniy Korabl lander. Or is that a multiple staged lander? hard to see, but i don´t think so.

Dont forget to leave any empty tanks on the mun surface. 

Only problem is I need this for repeat trips as I go back up to my orbital platform to start processing science, thus I don't want to go Apollo style.  Thanks for the help though!

 

Thanks also for the other suggestions

[Snark]

Hopping around on the Mun is really expensive.  You generally need a few hundred  m/s of velocity to go any appreciable distance... and you need it twice (one for takeoff, another for landing).

Since you need to pack a lot of dV for munar operations, keeping things small is key.  I find that for a Mk1 command pod, having around 2 to 2.5 tons of fuel works well for something that can make one round trip from orbit to the surface and back again, with enough margin to do one short-range hop on the surface.

My typical early Mun lander looks like this:

• Mk1 command pod (even better, Mk1 lander can if it's unlocked)
• Science Jr. (if I have a lander can rather than Mk1 pod, I put this on top of the pod, to keep lower CoM)
• 1-ton LFO tank
• Terrier engine
• Eight Oscar tanks.  These are attached as four radial stacks of 2 around the central LFO.
• Micro landing legs attached to the Oscars for a nice wide stance.
• Assorted science instruments attached as convenient

I deliberately leave off fuel ducts, no point in wasting 200 kg of mass on them.  The one-ton tank packs enough dV for a single big burn (e.g. from surface to orbit), so I just manually transfer fuel from the Oscars to the central tank when I have the leisure to do so (i.e. not during a burn).

If you're willing to go in a command chair rather than an enclosed pod, you can go even tinier than this, but you'll forego the ability to send a crew report, and you won't be able to top off your EVA propellant.  (Plus, of course, the command chair becomes available quite a bit later in the tech tree.  I find that by the time I have unlocked command chairs, I'm generally done with the Mun.)

Note that if you want a repeated lander that can shuttle between surface and orbit repeatedly, hop around, etc., then Minmus is much friendlier than the Mun for that.  It requires only a small fraction of the dV each time.

Edited December 18, 2015 by Snark

[ForScience6686]

I go with a similar idea as above but I avoid oscars on craft that I need to move fuel around.  My design uses mk1, utility bay or other science gear, small lfo tank and then 3 or 4 radially mounted tanks with legs for wide stance and a terrier.  I use decouplers to attach the radial tanks and enable fuel flow to avoid fuel lines.  

depending on mass and tank selection you should be able to get a couple hops before having to return and refuel.

 

[Plusck]

A few samples of light landers.
 They virtually all use either 3 Twitches or 2 or 3 Sparks.

Of course, only the heaviest one has a pod and so can store samples and do crew reports. The heavy one also has an outside seat for picking up passangers.

They all have a docking port underneath, and the heavy one on top too.

Edited December 18, 2015 by Plusck

[Pecan]

Did someone say small?

It's always good to start small.  When you get to adding a couple of extra pieces you end up with something bigger, like this:

It's 580m/s each way for Mun so you have plenty of fuel here.  Probably too much thrust though, might want to turn those powerful engines down.

[Scarecrow]

Not the smallest lander out there, but when Jeb, Bob and Bill retired from the KSC to set up their own Munar Tour business for wealthy tourists, this is the lander they used for ferrying said tourists from the Munar station down to the surface and back again.

 

Edited December 19, 2015 by Scarecrow

[Venusgate]

I'm gonna guess your TWR on the mun is at least over 5, closer to ten. First order of business: don't use poodles for a one-man lander! XD shouldn't need more than a single terrier for even a 2man with all your science needs and RCS to boot.

 

Edited December 18, 2015 by Venusgate

[keyscapeunit]

1 hour ago, Scarecrow said:

Not the smallest lander out there, but when Jeb, Bob and Bill retired from the KSC to set up their own Munar Tour business for wealthy tourists, this is th elander they used for ferrying said tourists from the Munar station down to the surface and back again.

 

What fuel tanks do you have on that?  I should add I'm playing Science Mode so don't have every little thing unlocked but probably about 60 - 70%

[Dafni]

Have a look at this one

http://forum.kerbalspaceprogram.com/index.php?/topic/124272-puff-puff-mk2-ultralight-rcs-dropship/

[Snark]

1 hour ago, Pecan said:

Did someone say small?

It's always good to start small.  When you get to adding a couple of extra pieces you end up with something bigger, like this:

...

It's 580m/s each way for Mun so you have plenty of fuel here.  Probably too much thrust though, might want to turn those powerful engines down.

Love the itty-bitty lander, but... how does that even fly?  I don't see any reaction torque ability anywhere. The OKTO2 doesn't have 'em.  Or am I missing something?  How do you steer the thing?

[GoSlash27]

keyscapeunit,

This Munar lander has 150% the required DV for a round trip to the surface, not counting the additional DV from the RCS system.

The trick is to design it from the outset for the DV budget and t/w using the reverse rocket equation.

Math is your friend!

Best,

-Slashy

Edited December 19, 2015 by GoSlash27

[Plusck]

7 hours ago, ForScience6686 said:

I go with a similar idea as above but I avoid oscars on craft that I need to move fuel around.

Hah! Yes. I made some prettier landers with toroidal tanks in addition to the larger ones. After the first refill I gave up and shut the tanks off. Emergency rations only.

[Plusck]

4 hours ago, Snark said:

Love the itty-bitty lander, but... how does that even fly?  I don't see any reaction torque ability anywhere. The OKTO2 doesn't have 'em.  Or am I missing something?  How do you steer the thing?

8° gimbal .... shame there is no coloured smoke option in KSP because it would make terribly pretty pictures getting from A to B.

I tried something similar - with reaction wheels and without a core, using two Puffs. Pressed Z by mistake above Minmus and used almost all the fuel just trying to get back to the surface without accidentally leaving Kerbin SOI...

[Temstar]

Did someone say small mun lander?

With landers this small you can design them to just be one use and throw away and carry one as part of your instrument on your big lander:


So you just land somewhere interesting, climb into the little flyer, do a suborbital hop to somewhere else interesting, fly back to your landing site, ditch the little lander and return to orbit with the big lander.

Edited December 19, 2015 by Temstar

[Plusck]

If ever KSP becomes multiplayer, I'll nominate that design for the first KSP (Top Gear style) football tournament.

[fourfa]

How about this one:

Stowable lander with all stock science parts that fits entirely in single-space Mk3 cargo bay.  Docking, you can thrust in directly, rather than have to translate in sideways.  2600m/s delta-V, enough TWR to fly on Moho or any smaller worlds.

[keyscapeunit]

5 hours ago, GoSlash27 said:

keyscapeunit,

This Munar lander has 150% the required DV for a round trip to the surface, not counting the additional DV from the RCS system.

The trick is to design it from the outset for the DV budget and t/w using the reverse rocket equation.

Math is your friend!

Best,

-Slashy

Dumb question, how do I know required DV?

[Reactordrone]

This is my usual. Has plenty of delta v so it can hit high latitudes from an equatorial station and easy enough to lift to the Mun and refuel for repeat trips.

 

[Wanderfound]

As others have suggested: a 1.25m based lander, a single Terrier for propulsion, no more than one of each science part (make sure to add a probe core somewhere so that it can be piloted by a Scientist, so the goo pod / Sci Jr can be reset) and around an FL-T800's worth of fuel (you can get away with half of that, but the big tank allows you to hit multiple biomes per trip).

Avoid heavy luxuries. Reaction wheels are not needed, keep RCS fuel to a minimum (if you're using RCS at all; it isn't necessary), go easy on lights and solar etc.

Put your refuelling station at 20km or so; not too expensive to get up to, but still enough room underneath if you need to rendezvous from behind. The highest point of the Mun is about 8,000m; anything above that is safe.

 

OTOH, I don't usually bother with Munar refuelling these days. A single 9,000m/s ΔV launch can hit three Munar biomes or every Minmus biome. Launch two of those and your tech tree is pretty much done. So instead, I tend to rush through the Munar stuff, then send a gigantic tank of LF to Jool. Once that's in place, I can send off a RAPIER/Nuke spaceplane to hit every Joolian moon in a single trip.

9,000m/s isn't hard to hit; I'd usually do it with a lander made of 1.25m parts, with a single Terrier in the middle (under a fuel tank, Sci Jr, service bay full of science gear and the probe core, decoupler/heatshield/Mk1Pod) and four onion-staged lateral tanks designed to be decoupled on the final liftoff from the Mun (centre tank is FL-T200, outer tanks are FL-T400).

Mounted on inline decouplers below those lateral tanks are a quartet of FL-T200s; these provide the fuel for the Kerbin->Mun transfer burn. Under the Terrier is a decoupler leading to a 1.25-2.5m adaptor tank, then two of the big red tanks. Under that is either a Mainsail or a Skipper and a few Thuds, and there are a few SRBs on radial decouplers for launchpad kick. Add a few struts and you're done; the main booster should run dry just as you hit Kerbin orbit.

To demonstrate:

 

 

Edited December 19, 2015 by Wanderfound

[GoSlash27]

5 hours ago, keyscapeunit said:

Dumb question, how do I know required DV?

keyscapeunit,

 That's not a dumb question at all. You can't mathematically design a stage without a DV requirement, so knowing how much DV is needed is critical.

 If you just want a good reference, it's here:

If you want to know the math behind it, I can explain that as well.

Since the DV from the munar surface to orbit is 580 m/sec, I multiply that by 3 for a round trip (landing in a precise spot is very wasteful of fuel). 1,740 m/sec DV is a comfortable amount for a round trip. 1,160 would be the theoretical minimum, but you won't manage to do it that perfectly. The more practice you have doing Mun landings, the closer you can shave it.

Best,

-Slashy

[Kraken1950]

From my experience, to deorbit and land you need between 580 and 750 Dv, getting back to orbit will cost you around 680 Dv. So the total cost of the maneuver si between 1260 Dv and 1430 Dv.

You can build almost anything as long as it has at least this much Dv. For example, something that ugly does the job (TWR is > 4 ; Mass : < 8t)