Grant_

It should be more than one stage.... have it go to about 8-10 km then switch to something else like a poodle.

Well if you're just making a very light probe you can get away with RAPIER engines which have very high ISP

Isp = specific impulse = amount that the engine can change the craft's momentum per weight of fuel OR force applied per weight rate of fuel

Just updated based on your guys suggestions I did employ Asparagus staging to drop 2 of the 8 engines for the first stage due to excess thrust... but I got it to orbit nicely! The only thing I dislike with having this much fuel is that is takes almost two minutes to create a proper orbit once I cut engines at 70 km and I doubt adding more nuclear engines will help. If I cut back from 16k dV to 15k dV I could use LV-T45 engines instead of skipper.... which is probably better.

The thrust has been calculated to get 2.2 TWR for the first stage, 1.5 the second (@6300m-low orbit) and the third 0.2. What TWR values should I aim for?

After using a tri-coupler on the nuclear rockets, I made a gif to show how it's failing:

Hopefully Moho and the Sun, but right now I'm experimenting with maximizing my dV (16 000 atm). During failure the skipper fuel tanks (stage 2) seem to push inwards at the bottom and then everything seems to blow up at launch, which does seem to take place there. I'm not set on the fuel configuration, just on the amount of fuel and thrust. How would I make it smaller? Right now my staging is just based on engine efficiency and achieving a 16 000 dV. I definitely will consider boosters. Just haven't added it to my program yet. Yes All of my tanks are in fuel loops since I think I need all the thrust the entire time :/ ... I guess I should calculate at what point I can get away with less thrust. Right now the thing just explodes on the launch pad and I can't even take off... I'm just not sure how to move things in closer, while keeping all the engines. I haven't used asparagus staging yet... right now I'm just making sure all the engines get fuel for the entire stage. Thanks everyone. I definitely have a lot to think about.

Right now the rocket has 5 Mainsail, 4 Skipper and 3 Atomic Engine. Unfortunately the Atomic engine section is making it very unstable.... I tried some girders but it didn't fit perfectly and didn't seem to help. Is there a better way besides adding as many struts as possible? Thanks

Working on a Matlab program to determine how many engines and fuel I need.... Staging is pretty primitive since it's based on optimal ISP. Haven't considered Asparagus staging yet.