"Best" engine for Mun landing...

[Fearless Son]

5 hours ago, RizzoTheRat said:

As for base building I was thinking of putting a refuel/resupply base on Minimus (or the Mun but probably Minimus) and a relatively cheap crew transport craft between there and Kerbin, so a lot of fairly heavy payloads going in and out of at least one moon.

I have heard people swear by Nervas for reusable lifters to ferry cargo like raw ore between Minmus and an orbital fuel depot.  

[NeoMorph]

I tend to use Terriers for one shot Mun missions where the engine will be thrown away. For reusable missions like a space crane that can take stuff from orbit, hover about to get the right spot, land, take off again and head for orbit, refuel, and go right back again... well that is nuke time for sure. The LV-N has the most efficient fuel usage for missions like that. Once you add up the lost Terriers for all the one shot missions where the engine and tank for the lander are lost, well, it then makes the expensive LV-N's well worth the cost.

I still think the LV-N should get more inefficient as it gets older due to damage to the nozzle AND it would get "hot" as in radiation hot due to leaks of fissionable material.

[Fearless Son]

26 minutes ago, NeoMorph said:

I still think the LV-N should get more inefficient as it gets older due to damage to the nozzle AND it would get "hot" as in radiation hot due to leaks of fissionable material.

That would make for an interesting design consideration and player-driven missions.  I imagine people would start deploying LV-Ns in detachable "blocks" that they can remove and replace with a follow up mission, returning the worn engines to Kerbin and giving the reusable vessel fresh ones.  

[stenole]

Regardless of engine choice(s), I favour splitting the lander into two stages. There is always lots of equipment that you brought down that you don't really need to bring back up. It also makes it less of a crisis if something is damaged during landing because the damage usually does not affect the ascent stage. If I need to land several places, I just bring several landers.

I usually only use nervas for transfers. The size of the terrier makes it more convenient as a lander engine because of how well it works together with lander legs.

[RizzoTheRat]

2 hours ago, MrOsterman said:

I may have to give up on the belly landing though.. it's proving to be really hard to manage.

 

The advantage of tail landers is they're usually symmetric, I'm guessing your problem is the CoT isn't centered on the CoM. Having the engines above the CoM like a sky crane can help a lot too.

 

I love that everyone has thier own wildly different approaches. 

[Hcube]

On 21/1/2016 at 6:04 PM, Nich said:

Why has no one mentioned the ion?

Because even on the Mun the TWR sucks. I'm not even sure the ion can lift it's own weight on the Mun. It probably can on minmus and totally can on Gilly, but the Mun... I don't think so

[suicidejunkie]

Speaking of descent damage, my mun landers lately have all been belly landers, but not intentionally.  The one time it did land vertically, I came back from an EVA walk to find it face down again.

The 909 is great since it has enough thrust to avoid most of the gravity losses at mun while still being very light.  That ship got back to Kerbin for only about 800m/s (direct ascent to munar retrograde) after I managed to get it tipped back up.

[LordKael]

11 hours ago, MrOsterman said:

What's odd for me is that I'm trying to engineer a multitask mobile base and lander so for me, the Thud is percolating out as the engine to use to finalize the landing.  Main engines to slow and then Thuds along the mainline of the ship to flip it belly down and land.  I had a design that layered the bottom of the ship with Aerospikes but I couldn't keep it level, and I'm not sure I can do the same with the required number of Terriers to keep the ISRU, drills, and passenger compartments from turning into a crater.

I may have to give up on the belly landing though.. it's proving to be really hard to manage.

 

My solution for landing a USI Karibou rover on Duna and Mun was to bring it in nose first with a skycrane assembly attached to the rear, so that the nose pointed down. On my Mun landing, I used a sepratron attached to the nose (which i later recycled using KAS) to flip it belly up, and used the rover's RCS/VTOL to land it. On duna, I just deployed chutes in sequence to spin it and bring it level before slowing down to land.

[Skorpychan]

22 hours ago, MrOsterman said:

What's odd for me is that I'm trying to engineer a multitask mobile base and lander so for me, the Thud is percolating out as the engine to use to finalize the landing.  Main engines to slow and then Thuds along the mainline of the ship to flip it belly down and land.  I had a design that layered the bottom of the ship with Aerospikes but I couldn't keep it level, and I'm not sure I can do the same with the required number of Terriers to keep the ISRU, drills, and passenger compartments from turning into a crater.

I may have to give up on the belly landing though.. it's proving to be really hard to manage.

 

Care to link your work on that? I'm interested in making belly landers, because my munshots keep falling the frak over. My last attempt was admittedly taped together on the pad to show off to friends while tipsy, but it refused to turn back over when on the mun, and took off like a belly lander when Jeb hit the 'frak it' limit and ran out of patience.

As for the topic, my ~10t landers get by just fine with a Poodle. Good ISP, good TWR for my landings, and more efficient than quad terriers.

[cantab]

I've tended to use the Spark on light landers. If I want to land "sideways" the radial engines are convenient, though a suitably mounted Spark also does well.

I've never thought of the NERVA for a Mun landing. I almost always do Munar orbit rendezvous, which cuts the dV needed for the lander, so maybe it wouldn't work out so well. Form factor is a challenge (though I've flown tall landers anyway) and the NERVA also lacks a gimbal, not a problem on a small ship where pod torque is enough but on a larger one it means spending mass on other means of control.

If I'm making a lander that lands sideways, I make it that flies sideways too. No point having separate engines facing in different directions.

[Red Iron Crown]

I think this tool can remove some ambiguity (though it doesn't factor cost in): http://firesurfer.de/gfrodo/ksp/engines/engines.html

 

[GoSlash27]

By my calculations for your original spec, I get the following (lightest, not necessarily cheapest) by payload for single engines:

<.20t Ant

.21-.31 Dawn*

.32- 2.3 Spark

2.4- 4.1 Terrier

4.2- 10 Nerv

11-26 Aerospike

27-36 Poodle

37-90 Skipper

91-290 Rhino

300-550 Mammoth.

*Does not include mass of solar panels or batteries

Best,

-Slashy

 

 

 

 

 

 

 

Edited January 23, 2016 by GoSlash27

[RizzoTheRat]

1 hour ago, Red Iron Crown said:

I think this tool can remove some ambiguity (though it doesn't factor cost in): http://firesurfer.de/gfrodo/ksp/engines/engines.html

 

Ooo, that's good

[NeoMorph]

On 22/01/2016 at 6:19 PM, Fearless Son said:

That would make for an interesting design consideration and player-driven missions.  I imagine people would start deploying LV-Ns in detachable "blocks" that they can remove and replace with a follow up mission, returning the worn engines to Kerbin and giving the reusable vessel fresh ones.  

Yeah... I love the immersion aspect of it. Whether anyone will work out how do do it is another question... I remember reading in SciFi novels how they discarded old nuke engines by dropping them into the sun... then I played KSP and realised what a load of old tat that was as the amount of Delta V needed to shove something into the sun is CRAZY high... even with slingshots. Oh and SciFi did teach me not to store old nuke stuff on the far side of the moon...

https://youtu.be/0cq7isloJj8?t=38m47s

Edited January 23, 2016 by NeoMorph

[Guest]

On 1/21/2016 at 3:04 PM, Nich said:

Why has no one mentioned the ion?

One does not simply land on the Mun with an Ion engine.

[Nich]

2 hours ago, Aperture Science said:

One does not simply land on the Mun with an Ion engine.

I have done it for light weight competitions.  It can be done and it can be done cheaply.   Most of your cost is getting it to orbit around Kerbal.  Only problem is by the time you have unlocked them the Mun is a thing of the past.

I believe I landed 1 kerbal on mun and miniums for 900 kerdits but I would have to look it up

Edited January 24, 2016 by Nich

[Kerbal101]

3 hours ago, Aperture Science said:

One does not simply land on the Mun with an Ion engine.

Oh, landing is not a problem.
"You took a toothbrush with you?"

[FleshJeb]

@Kerbal101 https://en.wikipedia.org/wiki/The_Cold_Equations

[Rune]

On 22/1/2016 at 8:44 PM, RizzoTheRat said:

The advantage of tail landers is they're usually symmetric, I'm guessing your problem is the CoT isn't centered on the CoM. Having the engines above the CoM like a sky crane can help a lot too.

 

I love that everyone has thier own wildly different approaches. 

You are falling into the pendulum fallacy there. Engines are much better at the bottom of the ship, where they bring the CoM down, and thus minimize any tipping momentum. As to belly landers, the difficult part is building them so the fuel is balanced around the CoM, and it drains balanced. But when you get that going, the low CoM and big footprint works wonders:

 

Rune. Really FUN™ to engineer!

Edited January 24, 2016 by Rune

[Frozen_Heart]

Though belly landers certainly look cooler, I still use tail landers as an extra set of engines is a waste.

[Kerbal101]

10 hours ago, FleshJeb said:

@Kerbal101 https://en.wikipedia.org/wiki/The_Cold_Equations

Since ship has at least one human on board, the story is inconsequent.
Humans are prone to errors and unexpectancies, so that should've been calculated.
There would be definitely at least 33% more fuel over the base line. Unless, its a pirate ship.

Edited January 24, 2016 by Kerbal101

[micr0wave]

this tiny thing can go from a 40x40km orbit to surface and back using a spark

[Kerbal101]

6 hours ago, micr0wave said:

this tiny thing can go from a 40x40km orbit to surface and back using a spark

This is a pretty cool lander!

Edited January 24, 2016 by Kerbal101

[Jouni]

Ion engines are perfectly fine for Mun landers. You use batteries as fuel tanks, and recharge them on surface. Six engines are enough for a lander based on the Mk2 lander can. Low-TWR landers can be a bit difficult to handle in the stock game, but it's definitely doable.

[MrOsterman]

I agree that Belly Landing is rough.  What draws me to it is that you can put more ~stuff~ there and not get too tall.  I've played around with some ideas to get more of a flat, Tail Landing design but all of them felt off.  I may revisit a few though because it feels like if I'm going keep going this way I need to learn how to build proper space plane rather than devising massive lift stages to get these beasts into space.

I'm not sure how to best show off what I've got but here goes...

First the KSP Athena SV2.  It's currently on it's way back from Duna and it seems to have had a successful mission there and back including landing on Minmus, Duna and Ike before coming home.  The MK3 passenger cabin sits, actually between two fuel tanks and holds not only all 4 tourists, but several crew members I had at Duna for other missions.  The main engines are the massive Mammoth lifters and a pair of Mainsails.  That's a lot of engine and a lot of fuel.  The belly engines are Thuds and there are a lot of Verners for RCS attitude control on descent.

 

Next is the KSP Aphrodite which is mostly built on a MK2 frame using 1.25m fuel tanks powered by a pair of Vectors and a pair of Reliants.  The Reliants are probably not needed but I liked the look.  Where the Athena has her drills forward, the Aphrodite mounts hers aft.  As a general rule it's a lot smaller than the Athena but does use an array of 8 Aerospikes as the belly engines.