What's your "YES!" moment when you research a part in career?

[Sesni]

I have 2. First is solar panels, but my latest one is

ALL HAIL LORD FUEL EFFICIENT NERVA

[Derpy Pigs]

Docking ports.

[Odo]

NERVA. I didnt land on any celestial body until the NERVA. First mun missions lander had one, and it was so efficient I landed on minmus on the way back too.

[XenonSpark]

Batteries, then struts. I can predict that the next one will be NERVA.

[Richy teh space man]

Unlocking science parts, because you can never do enough science..

[TheDataMiner]

Solar panels and the science stuff.

[Wallace]

Solar panels and docking ports.

[fatfluffycat]

Probes and solar panels

[Epthelyn]

I've yet to have a "Yes" moment on the tech tree. I get "YES!" moments when something completely underpowered (or apparently not) does what physics says it probably shouldn't do.

[astropapi1]

RTG. I hate begging the sun for electricity.

[Eric S]

Solar Panels and fuel lines. Once I have those, I'll cap science before I need any of the other stuff I've unlocked.

[doggie015]

Solar Panels and the Mainsail engine. I can get to Duna with skippers but that's just a one-way trip

[BuddhistPotato]

Docking ports for me. I could finally harness the power of attaching fifty crafts together and going on a science expedition.

[SunJumper]

The small solar panel usually revolutionises my crafts. The ion engines also normally make it trivial to unlock the rest of the tree. As you can see, I'm relatively patient.

[Xacktar]

Solar panels! The limits of batteries scare me.

[Scotius]

Solar panels, fuel lines and docking ports With these i can get science from anywhere in the system.

[Zaryulenko]

Bigger SRBs! Im not kidding, those things boost my suborbitals to the success/Failure!

[Galileo Kerbonaut]

First I desperately went for batteries and solar panels; if you don't have those, you're going nowhere.

[doggie015]

First I desperately went for batteries and solar panels; if you don't have those, you're going nowhere.

Unless you want to add more single-man cabins to your orbiter to get extra power

[Galileo Kerbonaut]

Unless you want to add more single-man cabins to your orbiter to get extra power

I restrict myself from doing things like that. I like to keep things "real".

[RocketPilot573]

The one with all the structural parts, such as I-beams, panels, trusses, etc. I was like YESSS, I can build things now!

[Vanamonde]

Unless you want to add more single-man cabins to your orbiter to get extra power

The Mk1 command pod has 160 times the mass of the first battery type, but only stores 1/2 the electrical power. I think you're better advised spending the research points on batteries.

[TTurchan1]

48-7s

Batteries and Solar

Struts

Mainsail

Using those i could go to tylo and back. personally i have a burning hatred of the nerva. It's too heavy, and its isp makes it vastly overused.

[User Unrelated]

batteries for me...

before I got batteries, I'd strap a medium fuel tank horizontally with 2 opposing liquid fuel rockets on top of every craft I flew, just to create enough power to send one or two more experiments of data once the main boosters had run out, or I landed somewhere on Kerbin.

Next, I'm gunning for struts...

Edited November 11, 2013 by User Unrelated

[Luis]

When I first began my career save, I was cursing the lack of bigger engines, struts, fuel lines, batteries, solar panels, docking ports, ladders and asas. But I've found that by the time I've unlocked each one, I'd figured out better designs so that I could manage without. I do still use all of those things, of course, and they make my ships better and easier to fly, but they feel like luxuries, rather than necessities now. For example, I'll extend my solar panels out of a sense of good practice, but the four small battery packs I carry would be perfectly adequate for my whole mission to the Mun since I now return almost all my data, rather than transmitting.

The parts that I've been most pleased to unlock are the extra scientific instruments. In fairness though, I haven't been further than Minmus yet.