Mun landing attempt

[KrisKelvin]

Ok, pretty pleased with myself. Managed to get to Mun, but damn this landing stuff is tricky! Do any of you use joysticks? I'm thinking it might be easier than this damn S, D, W key nonsense!

https://drive.google.com/file/d/1EYixSj4R8o5tQ6XSxLaAncYGUAlY-eWA/view?usp=sharing

 

Edited June 21, 2020 by KrisKelvin

[bewing]

You need to think a little more about what "retrograde" means in Surface mode. You don't need to fly it by hand.

[king of nowhere]

never considered using a joystick. i suppose it might be easier, though by now i'm used to the keyboard.

however, landing is not so tricky if you take a few measures:

- have an experienced pilot or a module that can point directions on board. automatically lock on retrograde, then you just need to burn retrograe and you will cancel all your speed. no need to ever press the SDWA keys, ever!

- have a ship with enough manueverability that you can quickly and reliably point in any direction. adding reaction wheels help.

- have a ship with a large base, so it will be more stable against capsizing on the ground

- do things slowly, have enogh extra fuel to not be rushed.

 

still, landing is not trivial. it's just routine enough that i can't bring myself to do it as slowly and carefully as i should; plus, going down like a stone and only braking at the last moment saves fuel, giving me a dangerous incentive to do things the dangerous way. finally, capsizing the ship is always a danger if you don't land on flat terrain. if you happen to fall down on one of the most cratery parts of mun, it can be hard to find a spot - and fuel-consuming.

and especially at the beginning of a career, a major problem is that you often don't have the pieces to make a proper lander with a wide base. my first lander was a very tall and narrow thing that could only land, with difficulty, on the most flat of the terrains. my second lander is quite stable and i'm still using the same model today, but it required unlocking new pieces.

[KrisKelvin]

1 hour ago, bewing said:

You need to think a little more about what "retrograde" means in Surface mode. You don't need to fly it by hand.

aha! so use the retrograde target thingy. Good idea! Why didn't I think of that!

Still.. I'm finding I can't get the engine throttled right, I try to slow down and end up going back up again!

22 minutes ago, king of nowhere said:

- have an experienced pilot or a module that can point directions on board.

and especially at the beginning of a career, a major problem is that you often don't have the pieces to make a proper lander with a wide base. my first lander was a very tall and narrow thing that could only land, with difficulty, on the most flat of the terrains. my second lander is quite stable and i'm still using the same model today, but it required unlocking new pieces.

A pilot or a module? What's that?

I haven't tried career mode yet (don't really see the point). I am just using sandbox. This ship is Kerbal X (one of the pre-built ones, so I am assuming it has the right parts for a landing)

[Laie]

3 hours ago, KrisKelvin said:

Still.. I'm finding I can't get the engine throttled right, I try to slow down and end up going back up again!

If your engine is way overpowered, even a little bit of throttling up will make a huge difference. In that case, try using the tweakables to reduce your engine's power setting.

[Vanamonde]

One thing you can do to make landing easier is click on the left side of the altimeter numerical display to switch from 'height above sea level' to 'height above local terrain." And do not try to land at more than 10m/s vertical speed. For whatever reason, that seems to be the magic number for just about any build in the gravity of most worlds. Faster than 10m/s is almost certain disaster. 

[Fraktal]

3 hours ago, KrisKelvin said:

A pilot or a module? What's that?

He means either a Pilot-class kerbal who leveled up at least once (have him fly a stable orbit around Kerbin and come back alive), or any probe core except Stayputnik or OKTO. This will allow you to set SAS to hold  during descent. If you do this, you don't have to do any steering, just throttle control. Don't forget, however, to set the probe core to auto-hibernate during warp!

Despite the name, probe cores are actually a useful addition to crewed ships. If you put any probe core that isn't a Stayputnik into a crewed vessel, that probe core basically becomes a navigational computer that lets non-pilot kerbals use SAS as if they were pilots themselves without an unmanned vessel's disadvantage of losing control if it drops out of radio contact with Kerbin. This is the simplest and most lightweight way to get a Scientist kerbal to the Mun for reusing single-use experiments while you only have single-seat command pods.

[KrisKelvin]

2 hours ago, Laie said:

If your engine is way overpowered, even a little bit of throttling up will make a huge difference. In that case, try using the tweakables to reduce your engine's power setting.

good tip! Thanks

2 hours ago, Vanamonde said:

One thing you can do to make landing easier is click on the left side of the altimeter numerical display to switch from 'height above sea level' to 'height above local terrain." And do not try to land at more than 10m/s vertical speed. For whatever reason, that seems to be the magic number for just about any build in the gravity of most worlds. Faster than 10m/s is almost certain disaster. 

now that's cool! I did wonder how I was supposed to know what height the surface is! duhh!

I've been trying to get it down to 15 m/s or less. Sometimes I think I've just managed it and the damn thing bounces and tips over!

1 hour ago, Fraktal said:

He means either a Pilot-class kerbal who leveled up at least once (have him fly a stable orbit around Kerbin and come back alive), or any probe core except Stayputnik or OKTO. This will allow you to set SAS to hold  during descent. If you do this, you don't have to do any steering, just throttle control. Don't forget, however, to set the probe core to auto-hibernate during warp!

Despite the name, probe cores are actually a useful addition to crewed ships. If you put any probe core that isn't a Stayputnik into a crewed vessel, that probe core basically becomes a navigational computer that lets non-pilot kerbals use SAS as if they were pilots themselves without an unmanned vessel's disadvantage of losing control if it drops out of radio contact with Kerbin. This is the simplest and most lightweight way to get a Scientist kerbal to the Mun for reusing single-use experiments while you only have single-seat command pods.

Ah.. I just have the two pilots who are already in the ship at launch. Didn't realise you could pick your own pilots. But surely it's me who's flying the ship, not them anyway? Aren't they just for show?

[king of nowhere]

4 hours ago, KrisKelvin said:

now that's cool! I did wonder how I was supposed to know what height the surface is! duhh!

yes, that's a good trick. before i discovered it, i tried to use my shadow to figure out my altitude. and of course i could only land with daylight.
 

Quote

 

I've been trying to get it down to 15 m/s or less. Sometimes I think I've just managed it and the damn thing bounces and tips over!

 

 

are you throttling your engine carefully with shift and ctrl? go easy on your engine. brusque manuevers result in disaster.

once you are close to land, you want to keep your thrust to exactly cancel gravity, so you float down gently. for most landers on mun, that's between 20 and 15% of max thrust. look your speed; if your speed is increasing, you decrease your thrust, and viceversa. you must be very delicate in your commands to avoid overcompensating.

10 m/s is slow enough that your ship won't break up and explode, but still, the slower the better. especially on low gravity worlds; you can get away with 10 m/s on mun because there is decent gravity, but on minmus 10 m/s will make you bounce and capsize for sure, and even 5 m/s is risky. on the plus side, gravity on minmus is so low, it's easy to keep a lower speed. also, the more stable your ship is, the more you can be careless before capsizing. my aforementioned first lander could have never landed at 10 m/s without capsizing, not even at 5 m/s.

 

Quote

Ah.. I just have the two pilots who are already in the ship at launch. Didn't realise you could pick your own pilots. But surely it's me who's flying the ship, not them anyway? Aren't they just for show?

yes and no. yes, you are flying the ship, you are giving commands. but the pilots can enable some additional functions. the first is SAS, stability assistance system. it keeps your ship standing still. i guarantee, it's almost impossible to do a good job of it without autopilot. once your pilot gets some experience (or you get a module past the basic ones) you can also point automatically in certain direction. in this specific case, you can keep the ship pointed retrograde, so it will always fire against its current movement. it makes landing much easier, because while keeping the ship poiinted correctly can be done with a bit of skill, pointing the ship correctly while also checking and adjusting the speed, and checking the altitude at the same time, while keeping an eye also on your fuel level... doing that all together would require an ace. good thing you can autopilot your attitude and just focus on the engine.

Edited June 21, 2020 by king of nowhere

[Spricigo]

14 hours ago, KrisKelvin said:

I haven't tried career mode yet (don't really see the point).

One of the points of career is that you have less option at the start and more will be presented as you progress, thus preventing you to be with lots of stuff  available but no idea how to start to figure out what is for.

It's largely a question of preference if you play career, science or sandbox. But it seems to me that new players often fall for the illusion that in sandbox all option are available when in fact there is nothing they know how it works. 

[Orc]

Hi all

Mun landings, the learning curve can be quite brutal, but the end result is extremely rewarding. Learn to save a lot, but especially before you start your descent.

Try to give your lander a low center of gravity with widely spaced landing legs. I recommend 4 or 6 legs. 3 should work but it seems to just invite disaster when you find yourself landing on anything less than absolutely flat. When I was learning to land I would frequently add 4 x FL-T200 Fuel Tank to the sides of my central FL-T400 fuel tank and used those to mount the landing legs on. Hellva a drag on Launch from KSC but also nifty for helping slow you down when return to Kerbol. Helps with the stability on landing big time.

Remember to make sure your landing legs extend well passed the bottom of rocket engine's bell. Getting to the Mun in one piece sucks so much if you can't get back home because your landing  gear let your engine hit the Mun too hard.

How big a lander are you trying to land? The OP mentioned two crew. Which ever way you do that it is probably easier to go with a single pilot in a MK 1 capsule. 

If you are landing a MK 1 Capsule with a FL-T400 or even FL-T800 fuel tank you don't need anymore landing engine power than a single Terrier. 

If you are having trouble controlling the Terrier's output right click on the engine BEFORE starting your de-oribt burn and set the thrust limiter lower. I would not recommend reducing the thrust limiter below 50%. Remember to set it back to full power before lifting off again

You will need to use the LEFT SHIFT and CTRL keys for throttle control. Some times you can get away with LEFT SHIFT and X (Reduce Throttle to 0).

If you are playing on a Windows machine beware of the Sticky keys app which will try pop-up every time you press the LEFT SHIFT key too many times. If anyone knows how to get around this I'd love to know. I've tried to disable it but it keeps coming back.

Like everything else in Life and KSP keep at it and you will master the necessary skill set, and before you know it you'll be swamped under the relentless endless tide of contracts for tourists wanting to Land on the Mun, and for Science from the Surface of the Mun.

And then the mega-funds roll in. ;-)

 

Regards

Orc

[KrisKelvin]

Many thanks all. I have now managed to land safely. Yay! 

Orc - fyi, I didn't build my own ship yet. I was just using Kerbal X, but I followed Laie's advice and tweaked the engine's power setting down to 75% which made fine control easier.

[Spricigo]

13 hours ago, Orc said:

 I recommend 4 or 6 legs.

Personally I'm found of using 0 landing legs, since radially attached fuel tanks don't bounce the same way. Still, I agree that 4 can be considered "the right amount" for a lot of cases.

 

13 hours ago, Orc said:

If you are landing a MK 1 Capsule with a FL-T400 or even FL-T800 fuel tank you don't need anymore landing engine power than a single Terrier. 

There is quite a few reason that people often use Terriers for Mun Landers. Is often the lighter engine people will have unlocked when going from the Mun the first time in a typical career, and it can handle landing, taking of and boosting back to Kerbin drooping just a few fuel tanks and science instruments along the way (if that much). Is not expensive

But if what you really want/need is just landing one kerbal at the mun?  The Terrier is a Beastly Overpowered Engine! You can easily pack all TWR and deltaV necessary for landing and return a kerbal with a spark and still call your lander beefy.  If you really want the right tool to that specific task, less is more.  Take a look what those little gems can do:

https://imgur.com/a/STlUvdM

[KrisKelvin]

8 hours ago, Spricigo said:

Personally I'm found of using 0 landing legs, since radially attached fuel tanks don't bounce the same way. Still, I agree that 4 can be considered "the right amount" for a lot of cases.

 

There is quite a few reason that people often use Terriers for Mun Landers. Is often the lighter engine people will have unlocked when going from the Mun the first time in a typical career, and it can handle landing, taking of and boosting back to Kerbin drooping just a few fuel tanks and science instruments along the way (if that much). Is not expensive

But if what you really want/need is just landing one kerbal at the mun?  The Terrier is a Beastly Overpowered Engine! You can easily pack all TWR and deltaV necessary for landing and return a kerbal with a spark and still call your lander beefy.  If you really want the right tool to that specific task, less is more.  Take a look what those little gems can do:

https://imgur.com/a/STlUvdM

what's that blue line marking your landing trajectory? Is that a maneuver node set up for landing?

[Spricigo]

1 hour ago, KrisKelvin said:

what's that blue line marking your landing trajectory? Is that a maneuver node set up for landing?

nope, that is a mod

[Fraktal]

12 hours ago, Spricigo said:

But if what you really want/need is just landing one kerbal at the mun?  The Terrier is a Beastly Overpowered Engine! You can easily pack all TWR and deltaV necessary for landing and return a kerbal with a spark and still call your lander beefy.

The only issue with a Terrier as Mun landing engine is that it's too big to fit under a set of Micro Landing Struts unless you offset the legs downwards and use the shrouded variant of the Terrier to hide the fact that the lower attachment point for the legs is free-floating in the air.

Same problem with the Poodle and the LT-01 landing gear, except without being able to hide the offset with a shroud.

[Okhin]

Well, you can land on the bell of the terrier, it's kinda tough that way. Sure, landing legs are best, but they're not really necessary (for a touchdown at lowspeed though).

[Spricigo]

8 hours ago, Fraktal said:

The only issue with a Terrier as Mun landing engine is that it's too big.

Fixed that for you. 

[king of nowhere]

you can also attach lateral tanks to your lander to widen its base. of course, it will fly worse in the atmosphere.

regarding the terrier, it is bigger than the spark, but it is also much more efficient. what will give you greater savings will mostly depend on how big is your lander.

the terrier is also unlocked earlier. by the time you do your first mun landing, you are very likely to have the terrier, less so to have the spark.

Edited June 24, 2020 by king of nowhere

[Spricigo]

1 hour ago, king of nowhere said:

regarding the terrier, it is bigger than the spark, but it is also much more efficient. 

 

No, the Terrier is not "much more Efficient" it just have a bit higher Isp. The most efficient engine is the one that do the job required for less cost, be it Funds, Weight, Player Time or whatever other metric we choose to measure cost. Often we use deltaV to measure the cost. As @Streetwind explained wonderfully here, deltaV=a*b*c. 

A trap players fall for so often is to think that the engine with higher Isp will provide most deltaV no matter what (or at least that  only in extreme circumstances it don't happen). Nope. Isp is just one factor. We need to consider mass fractions too. 

12 hours ago, king of nowhere said:

what will give you greater savings will mostly depend on how big is your lander.

Only if a big lander is necessary to begin with. Typical "lander equipment" ( crew space,science,...) for first visit weight less than 2t, landing+return to Kerbin requires about 1600m/s. With 2t of payload a FL-T400+Terrier will give 1,849m/s, while FL-T400+Spark gives 1,914m/s. It tend to be less about which one is better but if the spark is unlocked, which is not really a problem in normal setting but still.

 

 

[Streetwind]

My first Mun lander is typically in the 1.875m form factor, as I tend to want to level up multiple Kerbals per flight at that point, and multi-seat capsules are heavy. Those landers tend to use a Spark and four Ants (mounted on an engine plate). If I was flying 1.25m landers, a single spark would be plenty.

The Terrier meanwhile is ideal for 2.5m sized landers.

Downsizing the engine saves weight, which improves the dV of all the stages in the stack. This typically at least cancels out, if not exceeds, the loss of dV in the lander stage due to differences in Isp. And, at least in my case, i tend to be annoyed by the loss of precision that comes with having too much thrust while trying to land. I build all my landers so that the Mun-relative (!) TWR with completely full tanks is around 2.5. That means by the time I've deorbited and am coming in for a landing, it'll be slightly above 3, which is a perfectly comfortable amount of deceleration to land on.

[king of nowhere]

the first time i landed on mun, i didn't have the spark unlocked. afterwards, i always brought on some tourists, so bigger lander, so it needed a terrier.

the difference is minimal, though. as spricigo's calculation show, in most realistic cases it is within a few %. and then there is the engine cost, and both the terrier and the spark are cheap engines; maybe someone have some more efficient lander, but my mun missions tend to cost in the range of 40 to 60thousand. saving 150 on the engine is also not a big difference.

ultimately, regarding the spark vs terrier debate for a mun lander, i wouldn't worry too much.

[Orc]

Hi all and Spricigo,

 

I tested out Spricigo's little lander concept. Used a MK1 Capsule, four bagette tanks, a few science tools, and the Spark. Awesome! I over engineered the delivery vehicle, had enough fuel on the LKO-to-LMO stage to get to LMO and reduce the combined vehicle's surface speed to 0 a couple of times over.

Lift off and returning to Kerbin was the highlight of the mission. I pressed the wrong key at the wrong moment and ended up with a direct sub-orbital trajectory to Kerbin's surface. And then I mis-pressed the Warp control buttons and ended up with my Munar lander at 56KM altitude doing about 3100 m/s and everything glowing brightly. I thought I was going to plasma-rize Jeb for certain. Not happening today. Used the remaining fuel in the tanks to slow down a little, lost the solar panels and the 2HOT to overheating explosions but was still able to release the parachute safely just below 10KM and landed nicely in the desert highlands on the continent west of the KSC. Even managed to pick up a little extra Science there, hadn't used the barometer or finished with the highlands soil sample. 

Anyway, Spricigo, can you give us a look at the launch vehicle you used to get your lander to the Mun? I tend to use monsters that are over engineered in every way possible.

 

Take care all of you.

Regards

Orc

[Spricigo]

1 hour ago, Orc said:

Anyway, Spricigo, can you give us a look at the launch vehicle you used to get your lander to the Mun? I tend to use monsters that are over engineered in every way possible.

err...Since the purpose was only to demonstrate the little lander idea, "launch vehicle" was the cheat menu.  

But I can try to design something more along a proper mission(and I'm sure that others will help too). Just give  the parameters you want and what is available (more advanced tech node and building upgrades)

[Streetwind]

@Orc I can give you my early-career three-crew lander. It's admittedly a bit jury-rigged... you know, function over beauty and such. You'll also need at least the Making History DLC. And, do you have the seismometer unlocked yet? I usually rush for it on the tech tree, but I can take it off if you don't.

Otherwise you'll need half-size 2.5m and 1.875m tankage, the Skipper, the three-crew soviet capsule, 1.875m engine plate and aeroshell, and basic solar panels.

Edited June 25, 2020 by Streetwind