What am I doing wrong when landing on the Mun?

[Spaceweezle]

Here are some!

Matt

Good lord I've died and gone to picture heaven.

That looks like a definite improvement over your first lander, and I see you have the shiny Orange tanks, I can't wait to unlock those! Oh and congratz on saving Jeb, I know rendezvous missions are a pain in the butt, probably the most complex task I have ever performed in a video game. Good luck and godspeed on your next mission.

[Andersenman]

I have also had a look at your launch craft per your provided .craft file, and seen more issues.

Your second stage is humongously overpowered, and thus unnecessarily heavy with 3 Mainsails and the corresponding 3 Rockomax Decouplers; the latters of which are a surprise to me because I wonder whether and how you got them connected since the vehicle tree branches twice (the radial decouplers in first and second stage) and the branches then merge; at least it looks that way ... Oh, nevermind, I've just discovered that the radial decouplers in the first stage don't even hold the Jumbos, those are merely held by the rather beautiful strutting.)

Solution:

1. Pull off Jumbos and put them aside for later.
   
2. Launch Support; ditto.
   
3. Grab the second-stage side tanks and toss them and everything attached away.
   
4. Attach Jumbos to so far unused first-stage radial decouplers.
   
5. Attach Launch Support to Jumbos.
   
6. Pull off second-stage Mainsail with everything attached and put it aside.
   
7. Add another X200-32 (or replace both by one Jumbo).
   
8. Reattach first stage.
   
9. Check that staging has added all the Mainsails back in the right place.
   

Note, at this stage of fixing, this will be a heavy load on the second stage, sudden movements or wobbling must be avoided. I had the rocket break apart on the launchpad and during ascent multiple times. So, this advice will only help if you cannot reduce the weight of the payload. Also note that this will still use about 1:30 min of your 7 minutes final-stage burn time just to insert into Kerbin orbit.

The payload, your lander, was covered in the previous posts, so here are just the key points:

1. Ditch the X200-32 and any RCS-related items. If you don't want to dock, let other crafts do the approach work. If you want to just meet, two Roundifieds (for symmetry) and the group of 4-Way RCS blocks, together with the Poodle, will be enough.
   
2. Ditch Inline Reaction Wheels ring. The shorter, lighter craft will be nimble enough with the capsule's torque alone. However, if you do want to meet another craft in space while having the injection stage still attached, put the ring UNDER the decoupler to that stage, so once you ditch it you don't have to lug it around anymore.
   
3. Regarding electrics: If getting to the Mun without fuss is all you want, all you really need is an OX-STAT and a Z-100 to get around, maybe a Z-400, tops, so ditch as much battery power and solar panels as you can without hurting what desire to "realistically mimic" some sort of power supply you have.
   
4. Reduce count of legs to 4.
   

Basically, recreate Kerbal X minus all the ladders.

However, while you can descend, land, ascend, circularise/escape and return with that amount of fuel, you will need more help for your trans-munar leg and circularisation after capture, a problem you had with the old design already:

[...] had to use the lander to circularise the orbit at Kerbin and fly the Munar injection phase. If you can incorporate a more fuel efficient middle stage to perform these tasks, I am sure your lander will have more than enough fuel to perform a Mun landing and return to Kerbin.

Combining the advice above, let's find a rocket powerful enough to cater the needs. We have our Kerbal X derivative, the slimmed-down second stage and the fixed first stage.

[table=width: 0]

[tr]

[td][/td]

[td]

1. Remove the second X200-32 that was added.
   
2. Replace the second-stage Mainsail with a Skipper.
   
3. Since the first stage is now overpowered, add more weight and thus duration: one Jumbo each (!) on top of both first-stage outrigger tank to bring down that TWR from 2.77.
   
4. Employ the power of the asparagus: Draw fuel lines inwards and put the radial decouplers in a separate stage before the current second stage.
   
5. Check staging.
   

Nice flat ascent profile:

1. Launch full throttle until 110 m/s.
   
2. Reduce throttle by about 3 notches.
   
3. Start tipping over at 6000 m, passing 45 ° between 10 and 15 km.
   
4. Keep following along prograde.
   
5. Go to full throttle after decoupling the side boosters until Ap reaches 70 km.
   
6. Circularise as usual. This shouldn't take too much effort as you're coming in relatively flat already.
   

This leaves you plenty of fuel in the second stage to reach the Mun, about 1350 m/s dv.[/td]

[/tr]

[/table]

[table=width: 0]

[tr]

[td]

Next, plan and execute your transfer to use a minimum of fuel while touching the Mun, around 860 m/s dv. Those node planning gizmo mods (Precisenode, Maneuver Node Improvement) are really handy for this. dv remaining: about 500 m/s.

The capture burn at lowest altitude turns out to be only about 270 m/s worth of dv, and descent+landing costs another 550 m/s ... let's say 600 for hovering, sneezes or cats on the keyboard. You now have the choice: adjust Pe and circularise first, or brake for landing without orbit - the second stage is going down in any case. Remember, Kerbal X can do anything from descent on, and the second stage has already helped half-way. Plus, it has a higher TWR than the second stage, so you can brake even better after separation, meaning you won't have to worry about not having enough burntime left to brake. However, you will have little time to plan the braking burn with the Lander stage. I my first attempt I had less than 20 seconds to start the second braking burn which took about 10 seconds.[/td]

[td][/td]

[/tr]

[tr]

[td][/td]

[td]Braking and landing in one go - If you wish to keep your space clean from debris, planning for a surface-grazing trajectory helps with getting rid of the second stage. Perform the capture burn with the second stage as long as possible, then raise periapsis and complete circularisation with the next stage – or simply land right away.[/td]

[/tr]

[/table]

So there you go. I'm sure there are more efficient designs (like Skippers in the side boosters instead of Mainsails, with just a little bit of extra fuel instead of an entire Jumbo each, or some such), but this one was the quickest adaptation of your existing launcher I found without too much mucking about.

Happy Landings!

Edited December 13, 2013 by Andersenman

[DrMonte]

Muns escape dV is quite low, so building separate lander is not always efficient. Especially if you are bad at rendezvous and docking. I'm not sure it it's efficient at all in KSP? :+/

[capi3101]

Muns escape dV is quite low, so building separate lander is not always efficient. Especially if you are bad at rendezvous and docking. I'm not sure it it's efficient at all in KSP? :+/

Well, there are advantages - the main one being that you can get away with a lighter lander (you're not hauling all that fuel you've set aside for the return trip down to the surface just to haul it back up again). It's also safer; if something goes wrong, you can still send somebody back. That was the rationale used by the Apollo program for the LM design anyway.

[KSK]

Are you saying you don't kill your velocity separately but do one long velocity kill and descent burn? Is this any harder to balance?

I think so.

It's never quite a single burn because I normally kill my horizontal velocity whilst I'm still a kilometre or so from the surface, switch off the engine briefly to orient myself and then do a vertical descent from there. In principle you could do it in one but you'd need to be a better pilot than me.

I don't find it that much harder to balance and it can be helpful for changing your landing site on the fly. Heading onto a crater rim? No problem, just throttle back a bit and overshoot it. Spotted a good landing site on the way in? Again no problem - throttle up and kill your horizontal velocity a bit earlier.

[photogineer]

Hey everyone, just letting you know I haven't forgotten about you, KSP is generally a weekend activity for me, so my progress has slowed, but I'll be back, the bugs are pretty much out of the new launcher/lander set, just practicing ascent profiles to reliably get in to orbit!

Still have two Kerbals in Kerbin orbit to rescue, I consider that practice, and then I'll go get the guys on the Mun.

Matt

[Andersenman]

Best of success, keep us posted!

[photogineer]

Best of success, keep us posted!

I shall, I expect to finish this adventure this weekend. Just earlier this week I had a successful orbital rendezvous between an early A3 prototype and the latest to recover some crew stuck in orbit with no LF and no parachutes. I had to use the stricken ships RCS thrusters to circularize their very elliptical orbit. I of course got some photos:

Two ships next to each other: https://www.dropbox.com/s/xaneipg8hfb67n6/screenshot373.png

Another angle, you can see that the one is lacking parachutes: https://www.dropbox.com/s/beda0kh762a264c/screenshot375.png

Bob about to get aboard the rescue ship: https://www.dropbox.com/s/iqu8oyq7pkess18/screenshot380.png

Leaving the stricken ship behind (it's still in orbit!): https://www.dropbox.com/s/2ds4phx4teuxpon/screenshot403.png

Hitting the hot part of re-entry passing over the space center (I'm getting much better at targeted landings!): https://www.dropbox.com/s/vtxm9lgmwfy11sg/screenshot407.png

The boys are home: https://www.dropbox.com/s/lskswd10yljo565/screenshot412.png

Pretty close to KSC in fact: https://www.dropbox.com/s/fbkpc51vnbebybk/screenshot413.png

The design is coming along well, though it has a slight flaw... the landing legs aren't long enough, so during a parachute landing to Kerbin land to test them..... well, this happened:

Right before touchdown: https://www.dropbox.com/s/ipn85odjsvie5ec/screenshot303.png

Touchdown: https://www.dropbox.com/s/wpx5smsea9w1u1g/screenshot304.png

Right after: https://www.dropbox.com/s/gicdch28n5xn7jx/screenshot305.png

Oh well, it's progress!

Matt

[Scarecrow88]

For ease of viewing, you should embed your images in your post. With so many to look at, I can't be bothered to follow all the links, and I daresay there are a few like me that won't follow them either. If you embed the images, everyone gets to see them.

[capi3101]

Tags for images are img and /img, in brackets; you put the url of the image in the center.

[photogineer]

Alright everyone, there's good news, and there's bad news....

Good news

The landing legs were switched out and realigned and now keep the engine bell from impacting. A number of tests involving ditching the first stages of Avenger III in Booster Bay and doing parachute/powered landings at KSC proved that even with a simple solution, Kerbals can waste a lot of rockets and money. Oh, and the new landing legs solved the problem.

Avenger III successfully made orbit with it's crew of three to test a land and return mission from the Munar surface in anticipation of their rescue mission. The team successful made Munar orbit and began a powered descent, ultimately landing on not quite perfectly level terrain. The crew were all EVA'd and planted the first Kerbal flag on another world. Then they got back in and started preparing for liftoff and return to Kerbin, which leads us to....

Bad news

The team has computed that they have insufficient fuel remaining, with a remaining dV estimated at 733 m/s by the computer, they can't break Munar orbit. A number of simulations have been run using the industry standard QUIKSAV simulator and they were unable to find a viable launch solution. The team is currently awaiting instructions.

I've tried to use an imgur album this time to share the triumphs and downfalls, let's see if this works:

Javascript is disabled. View full album

So... definitely progress! Now how to rescue my rescue team... (this is sort of like rocket fuel, the more fuel you carry, the more you need, the more Kerbals you send to rescue, the more that need rescuing!)

Any advice guys?

Matt

[SRV Ron]

One mistake made in landing is being able to kill all horizontal drift. After several tries, I got down the mechanics of using the Navball marker to kill drift. When sufficient horizontal drift is eliminated, the retrograde marker will stay under the craft ad vertical speed is cut to the desired landing rate. If not, things break or you tip over. Example;

When done right, even tall craft, (and unguided boosters,) will land properly.

Edited November 16, 2013 by SRV Ron

[photogineer]

Success! Sort of. I rescued the rescue team. I realized this morning that the A3 had enough fuel to orbit Mun, so I sent up a modified version of the rocket, the Avenger III-P with some minor refinements to the staging, a probe core, and two smaller engines to help boost the weak middle stages. During launch there was a problem with the first stage separation that destroyed the second stage, but I just spaced right through them and continued on, making a lower orbit than planned, but otherwise fine. My very own ATO! I sent the A3-P on a shot in to Munar orbit and met up with the stricken A3 to transfer the crew and brought them home to Kerbin, I have pictures:

Javascript is disabled. View full album

So, I am getting pretty good at rendezvous, maybe I should putting docking ports on these things! The Avenger program has two different versions of derelict Avenger III spacecraft orbiting two bodies now, and there is still one team left on the Mun. However, I can now land on the Mun, so retrieving them is a matter of practice/time so I can not use as much fuel when I land. So, thanks for the help everyone, I'm marking this one answered! I may feel compelled to do a mission write up once the last team is home, if there might be interest in that.

Thanks again,

Matt

[capi3101]

Go for it, I wouldn't mind hearing about your exploits.

I'd stick a couple of roundified RCS tanks on your CSM - the extra push from RCS thrust would've been enough to get that last ship home under its own power. Always sucks to be 100 m/s shy......

[Andersenman]

I'd stick a couple of roundified RCS tanks on your CSM - the extra push from RCS thrust would've been enough to get that last ship home under its own power. Always sucks to be 100 m/s shy......

Mind, though, that you should use up Mono as early as your mission allows due to the lower Isp. Simply put: After spending a certain mass of LiquidFuel+Oxidizer you will end up at a higher speed than after spending an equal mass of Mono, so you should aim to stretch the Liquid stuff as far as possible by not lugging around the inefficient Mono, only their now-empty tanks. (In all fairness, this is not the fuel type's fault but the engines' that are using it.)

Edited December 13, 2013 by Andersenman

[Dogface]

for something that tall, put eight lander legs. I have landed bases that tall.

[Curiosity7907]

It is impossible to land on the mun because if you start you burn to low you will crash if you start it to high you would be wasting fuel.

[linuxgurugamer]

6 minutes ago, Curiosity7907 said:

It is impossible to land on the mun because if you start you burn to low you will crash if you start it to high you would be wasting fuel.

Strange.  I wonder what I've been doing all these months, landing on the Mun.  and all the other players who land as well.

[sal_vager]

Blimey, this is from 2013, what a vintage!

Also if landing on the Mun was impossible I think it'd be more widely known by now, if you're having trouble with your Mun landing then I suggest you take a look in the Gameplay Questions and Tutorials forum.

Closed!