Working design test

[Hikaru]

It\'s been a while since I posted any new ship designs. I\'ve been slowly learning how to lower the amount of fuel required for my ship while also making the lander it launches lighter and stronger.

This version of the ship is all stock except for mechjeb, which you can find on these forums.

This particular variant of the ship was able to launch, orbit kerbin, orbit the mun, land on the mun, launch off the mun, orbit the mun, and then aerobrake and land on kerbin with about 10% fuel left in the last tank.

While this is a perfectly good and working ship, if you have any suggestions on reducing the fuel or weight required further, I\'d love to hear from you.

[purple100]

Some things I used to drop the weight of my lander:

1. Ditch the landing legs. MechJeb 1.7.3\'s landing computer can bring you to a safe touchdown on the engines themselves.

2. Avoid using radial decouplers on the last stage. Gravity on Mun is so low that you don\'t need to jettison those radial fuel tanks. Of course, if you\'re doing a powered landing on Kerbin, it might be worth keeping the decouplers.

3. Switch to the MechJeb radial model, the flat one.

4. Replace each radial full-size tank with 1 mini-tank and 1 mini-engine. You sacrifice only a 1/2 tank of fuel but gain a better thrust/weight ratio.

The setup I\'m using easily shaves 3 units of weight off of your lander design. I found out that lighter landers with more thrust/weight tend to do better than ones loaded up with more fuel. Feel free to disagree with any of my design choices, I just hope you can make use of some of these ideas.

[Hikaru]

Hmm. Interesting ideas. I\'ve also had people suggest other things, such as simply replacing the lander\'s engine on the current design with the smaller variant; turns out that the fuel efficiency of the smaller engine is about the same as the larger one, and the weight difference matters not a bit due to my design having the lander\'s engine lit for the entire flight after the solid boosters drop. Replacing the 1m mechjeb with the radial one is something I hadn\'t thought of, and I\'ll be trying it out on my next redesign.

I deliberately have \'too much\' fuel radially coupled to the lander along with landing legs for a variety of different reasons. Primarily it\'s so that I have a wider base with which to add stability when I\'m landing things manually - mechjeb is nice, but I always like to have the ability to land the thing myself if something goes wrong. There are other reasons - due to the lander *having* too much fuel, I deliberately use it to do the munar insertion orbit from kerbin and decelleration from munar orbit to landing using the fuel on the side coupled tanks. The three side coupled engines and tanks are dumped shortly after achieving initial orbit around kerbin, and so are obviously unavailable for the rest of the flight. The radial decouplers are there so when the lander\'s side tanks are empty and I want to take off from the mun, I can easily drop the unnecessary weight and conserve whatever fuel is remaining in the last tank.

One thing I *have* decided is a bit redundant is the rcs fuel tank and thrusters; I\'m simply not using the things as much as I used to. It\'s possible I may not get rid of them though, it\'s always nice to use to manually change your orbit height in very small amounts rather than having to use the main engine.

Thank you for your suggestions.

[Hikaru]

Decided to fiddle around with trying to make as small a lander as possible that was mechjeb certified. I had mixed success; it\'s not possible for me to land this manually, and mechjeb seemed to have serious doubts about its ability to land while the side tanks were attached. However, it\'s perfectly possible to land this without them if mechjeb is active.

... Unfortunately, I then neglected to realize I was launching in a clockwise orbit and wound up in an orbit around kerbin with insufficient fuel to either slow down enough to miss the mun as it approached me, nor speed up enough to avoid it. Hilarity ensued as the mun recaptured me and I was gravity assisted into an ejection from both munar and kerbin orbit. The poor fools are now orbiting kerbol with no way to return home.

The design has many pluses to it due to the reduced weight of the lander; since I removed the rcs tank, the 1m mechjeb and replaced the lander\'s lfe and lft with the smaller variants, to orbit had slightly more fuel remaining in the launch tanks. Unfortunately due to it\'s much lower thrust, the lander has to do a much longer burn to get it into munar orbit, and although it\'s slightly more fuel efficient I don\'t particularly like its handling, especially since there is very little leeway once you land on the mun to get back to kerbin, as well as the very obvious fact that I am incapable of landing this by myself.

I think the next redesign I do will reequip the larger lft and lfe and keep the rcs fuel. There\'s a big difference having the extra thrust of that engine, and having the rcs fuel makes correcting bad orbits easier. (and gives you one last method to return to kerbin if you really screw things up.)

[Hikaru]

This is the fourth revision of this design generation. I think I\'m pretty comfortable with the end result; mostly this is the same ship as in V1 except that I removed the 1m mechjeb and replaced it with a side mounted one.

There seems to have been some confusion in discussions I\'ve had with others about how the lander\'s engine is able to fire during launch without using the fuel on the lander; more or less this is due to me chaining fuel lines from the lowest tanks on the outer ring to the innermost tank on the lander.

If people had actually tried launching my ship they would have noticed the tanks on the lander weren\'t being used until orbit, but very obviously some people aren\'t doing that, and this video I made is for them.

You can easily see the fuel lines (and struts) in this video, as well as the fuel levels.