[stock .14] Munficiency II

[grovest4life]

The Munficiency II gets you to mun and back on the equivalent of 4 full size tanks and includes the luxury of being able to take your landing legs along for the ride no need to take off on your side. This craft has a tight fuel budget and requires a skilled pilot to pull off or if your like me and lack the skills you will want to strap your trusty AR-202 Mechjeb unit to the side.

I have only had one successful trip so far with the Munficiency II and the fuel budget was tight to the point I could only return to Kerbin using a Bi-elliptic transfer maneuver that brought me out to 40 million meters from Kerbin at apoapsis so I could cheaply bring my periapsis down to 31k above Kerbin. After this maneuver i had little more than a whisper of fuel left to set the valiant Kerbins down in the ocean which was just enough that the capsule and all that where aboard survived. All previous attempts using a Hohmann transfer maneuver to return from the moon only allowed me to get within 800k of Kerbin before fuel exhaustion. As an aside I have not yet been successful at getting back from Mun with the fine Koalemos II by kosmo-not so a better pilot than myself may be able to get back from Mun more directly since both ships have very close to the same delta V left in the tank once reaching a 70K Kerbin orbit when I used the AR-202.

Heres some pics of the Munficiency II

Just before stage 2 separation and prep for final stage

Final stage not my most efficient orbital insertion since this was a mechjeb free attempt

Attached is the craft file for your enjoyment

Edit: don\'t know how to post pics in spoiler tags properly so here is the link to the album. http://imgur.com/a/reIT7 Added craft file for Munficiency III removed landing legs added fins went from 374 units of fuel in LKO to 382 units of fuel thanks sal for the suggestion.

[sal_vager]

Hi grovest, you need to put the direct link in the img tags, not the links from the album or they don\'t show up.

Nice tiny ship, can you show us the full flight to the Mun and back? I hope you remembered to take pics

[grovest4life]

I unfortunately did not get any pics from my successful run there was a lot of quick saving and reloading due to the many failed mun to Kerbin return orbits and I wasn\'t sure it was possible to achieve but now that I know it is possible I will be making another trip again in a day or so and will fully document it with pics now that i know how to do it. Total MET from departure to splash down was around 5 days due to not having enough delta V to take the direct Hohmann transfer and having to use a Bi-eliptic transfer. I\'m also going to try and work on getting better at hand flying it and am considering doing my next attempt by hand without the aid of Mechjeb.

[sal_vager]

Ok maybe I can help a bit, I have been getting better at hand flying and have managed better fuel economy recently than I though was possible, at least with my flying skills.

I expect you know the following already though

I will have to try your ship myself, but watch your speed as you ascend, you may need to throttle back a bit once you get to 100m/s, accelerating too quickly after that loses you efficiency as you push against the atmosphere.

I like to pitch over at 12k to 45 degrees east, then again at 24k to 68 degrees, then level off when my apoapsis hits about 45k, I shut down the engines at an apoapsis of just over 70k, I usually have quite a bit of speed at this point so finishing the orbit is easier.

I\'d lose the mechjeb, on such a small ship it\'s not really needed, and the weight penalty, though small, is still having an effect, use capslock for fine control.

It\'s possible to land on the engine, but it\'s hard as it requires zero sideways movement, and the legs seem a bit lardy at 0.1kilo so maybe wings are an option on a mk2, you\'d save 0.06kilo and you might get a boost from atmospheric lift as well, they are also less draggy.

Hope this helps and I\'m looking forwards to seeing your flight.

[grovest4life]

My Mechjeb unit weights .00001 and with or without it my power to weight on the final stage is still 11.23596 I\'m sure it has an impact but its fairly insignificant compared to the legs. Part of my design criteria was to see if I could match the performance of the other ships I have seen that use one and a half tanks that lack legs I wanted to match their performance and range while keeping the legs. Also another efficiency in my design is that all engines are in use during all stages so that I am not carrying dead weight its also one of the reasons I went with the LV-909 over the LV-T35 during the launch stage.

At launch the ship makes 250 thrust the ship i originally set my goal on beating the benchmark for performance I set which was the Koalemos II which makes 600 thrust at launch but also has a 50 thrust engine hiding behind a coupler contributing nothing to the launch but adding payload to to the launch. When launching the Koalemos II it gets off the pad very well but for efficiency the Mechjeb auto dials back the power to about 80 percent throttle and from that point on your carrying more power than you need and the added weight of the big powerful engine not being fully utilized which adds to the mass that you have to carry to orbit expending more fuel to do it. Its a fine line ideally you want the perfect engine that has only as much power as you need assuming equal power to weight ratios of course but none of the engines quite match that criteria Koalamos II falls on the side of to much power and mine falls to the other side of the line being under powered such that at 100 percent utilization I\'m not able to reach an ideal climb out speed so have to waste fuel fighting gravity for longer but my final design seems to be closer to that line. The II designator in the Munficiency name is my 4 tank model that i revised from a 5 tank version when I discovered that others had created 4 tank moon rockets.

You may be on to something with substituting the legs with wings not only are the fixed wings lighter but i essentially am getting lift for free since they have the same amount of drag as the landing legs. Fitting the wings will be a challenge though since some of my legs are tucked behind tanks.

[sal_vager]

I see what you mean about the tanks obscuring the wings, they would have to be mounted higher, also on my install the legs have a drag of .2 while the wings are .02

As far as the underutilized engine is concerned, the extra power is helpful just to get your velocity over 100m/s as early as possible before throttling back, the penalty to your fuel budget from the poor acceleration at launch from using only the lander engine may be a factor, but as you said it\'s lighter in weight which is better over the full course of the flight, I base the above on closette\'s work on the goddard problem, rockets are too inefficient just after launch until they can build sufficient speed.

Shame the engines aren\'t radially attachable without a tank, they could be dropped earlier then.

[grovest4life]

You are correct I miss read the drag values for the wings seems amazing that they have a tenth the drag of the landing legs yet are creating lift something is a little off here not only do they have increased frontal area but they seem to be creating lift without the corresponding drag that is a product of lift creation either that or the drag value for the legs is to high seems like seems something needs an adjustment but then drag implementation in this game is a bit wonky at the moment anyway but when or if it is fixed my ships will loose a good deal of there efficiency advantage over the narrower stacked ships.

[sal_vager]

Yeah, and I\'m sure when I updated 0.14.2 to 0.14.3 on windows the leg gained a description and a weight of 0.075, it didn\'t work on linux and it\'s not there anymore in the fresh download of 0.14.4

The drag ratings are all likely to change at some point, making such efficient rockets a temporary thing, but we can enjoy it while it lasts, when re-entry heat is introduced any ship without a decoupler under the capsule is going to suffer.

Here\'s an idea I am toying with, have a large engine under the center of the rocket on a stack decoupler and drop it the moment your velocity reaches 100m/s, the boost above the critical speed may offset the weight penalty, you wouldn\'t need it attached for long on such a lightweight ship as yours

[grovest4life]

Gave it a try didn\'t get the improvement we were hoping for the persistent file says that the revised design has 372 units of fuel once the 70k orbit is reached as currently designed the ship is left over with 374 units of fuel once in an orbit of 70k so it appears that holding the big engine underneath even for that short time is and may actually harm performance but the difference is so small it may just be within the normal variation.

[sal_vager]

Ok I had to rebuild it as I don\'t have mechjeb installed on the memory stick, and I may have the legs wrong, so feel free to fix it up.

Launch at full power and don\'t throttle back

[Kosmo-not]

I look forward to testing this rocket when I get back home tomorrow (provided that my roommate has dealt with the internet and electricity being shut off).

[grovest4life]

Looks like a good revision I cant say I achieved orbit yet though unfortunately spent like an hour trying to move the landing leg de-couplers around in a way that they would not disassemble the ship on activation so far no luck on that.

[sal_vager]

Okay I have (kinda) fixed the landing leg issue and added a stack decoupler to the base as I want to avoid any possibility of sticking to the pad.

I experimented with the engines but you need all 6 running or you won\'t get close to 100m/s before the pop, after that though it\'s possible to throttle back a little to conserve fuel.

Also she\'s twitchy, I have noticed before that the game doesn\'t like having gimbaled engines above the center of gravity, I can hand fly her though.

Second tank release is not 100% guaranteed but is most likely with zero throttle, it can impart a lot of spin so watch for that.

groovest, I can\'t match your takeoff without a mechjeb, so you\'ll have to let me know if this works any better.

[Seyvern]

Had fun playing with this, but the second stage (landing leg decouplers) are still iffy as hell. I\'d say 50% of the time they destroyed the ship.

[grovest4life]

The accent profile looks promising but have not yet been able to have a successful second stage separation I guess thats to compromise of trying to use landing legs as couplers. For me the landing legs break off and fly away on activation and the tanks stay.

[sal_vager]

Hmmm yeah that happens to me, not as much if throttle is 0 though, maybe adding struts to the base of the landing legs would help but when I tried adding them the ship kept exploding on the launchpad.

Edit: Okay here we go, I managed to get the struts to work most of the time, and I had successful 2nd tank separation 4 out of 4 times, with a 5th attempt it exploded and on a 6th a tank fell on the wing ripping it off, that won\'t happen in free fall.

[grovest4life]

Stages reliably and has a record 387 units of fuel in orbit with the mcjeb. Now to refine my hand flying skills best orbit was 378 units by hand. I will start documenting my attempt to reach mun and return with the Munficiency proto 4.