Jool and beyond without docking

[Synapse]

Hey I've just established my first Jool manned orbiter, using a large X3-200 fuel tank, a nuclear engine and 2 electric engines. I ran out of liquid fuel pretty much exactly as I circularised orbit. So what strategies can I use to get further out without docking, or to plan a return mission? Just more fuel and more nuclear engines? Should I asparagus in space? Turn gimbal off? tips please.

[Skorpychan]

Trim out EVERYTHING you don't need. Use one engine only for your burns, make maneuvers early to use less fuel, and so forth.

Practice the hell out of your ascents. I've gone from running clean out of fuel on my mun landings to having a good third of a tank left.

Don't pack RCS. Or if you do, don't use it much to make a small tank last. Engine gimbal can do a surprising amount.

[AlexanderB]

Aerobraking at Jool into orbit saves a bunch of fuel..

Aim for a PE of +/- 115 km when you come in from Kerbin and it should make a nice orbit that needs much less fuel to correct into something thats stable and round.

Don't timewarp too fast, or it will change your PE again after you correct it.

quicksave at the SOI change point so you can re-do it if it was too low or too high.

and otherwise, what Skorpychan said, strip everything off you don't need.

Edited July 12, 2013 by AlexanderB

[Synapse]

So is RCS essentially defunct? What about my 2 Ion engines and solar panels, are they worth their weight?

Also I don't understand the aerobraking, won't I crash into the surface?

Also is there any efficiency at burning full throttle in space?

[AlexanderB]

So is RCS essentially defunct?

for small enough crafts, pod torque and engine gimball is enough, especially if you don't need docking, or if the docking ship is small engouh that you can just rotate it around to use the engine for corrections. (that takes some practice)

What about my 2 Ion engines and solar panels, are they worth their weight?

for like a probe body, a battery and maybe some science gear, yes, otherwise, no. They output so little thrust, that it would be very useless on anything heavier.

Also I don't understand the aerobraking, won't I crash into the surface?

no, the idea is to fly into the atmosphere, but not into the surface, if you pick the correct height, the air drag will slow you down a lot, but not enough to drag you to the ground, so you'll skip back out, but after slowing down, you're in a big oval orbit, not on the escape trajectory you were..

(If you pick too low an orbit, you will get dragged down and hit the surface.. It takes a little practice.)

Also is there any efficiency at burning full throttle in space?

Yes. efficiency bonus for:

-burning as horizontally to the surface of whatever you're orbitting as possible

-burning as much as possible along the prograde vector (if it isn't horizontal anymore)

-burning full power with the engines you have.

I'm not too great at explaining why, but thats how it works in real life too..

[Synapse]

Okay thanks. Can you provide me with some ideas of fun things to do at these kind of long distances?

[Landge]

Aerobraking at Jool into orbit saves a bunch of fuel..

Aim for a PE of +/- 115 km when you come in from Kerbin and it should make a nice orbit that needs much less fuel to correct into something thats stable and round.

Don't timewarp too fast, or it will change your PE again after you correct it.

quicksave at the SOI change point so you can re-do it if it was too low or too high.

and otherwise, what Skorpychan said, strip everything off you don't need.

I've had the Kraken attack my ships that go any lower than 116,000m above Jool. You have to account for atmospheric drag when plotting your periapsis as you're approaching Jool. I wouldn't set Pe any lower that 119,000m myself. You'll descend lower than that when you've entered Jool's atmosphere. Once free of Jool's atmosphere, if your apoapsis is still too high you can always adjust and do another aerobrake at a higher altitude to get your final orbit where you want it. Definitely save right after entering Jool's SOI so you can make adjustments before getting too close to Jool.

I'd send fuel tankers out ahead of my main ships so you can refuel once you've arrived at your destination.

See my Moons of Jool Missions for an example. Mostly stock parts, using only ISA MapSat and Iannic's Chatterer. No other mods used.

When you are approach an airless planet or moon it's best to set your periapsis as close to the surface as possible 5,000m to 6,000m. Plan to fire retrograde halfway ahead of periapsis manuever node. That is if your burn time is 10 minutes start firing 5 minutes ahead. Watch your Pe. You don't want to be clipping any mountain tops.

Edited July 12, 2013 by Landge

[Skorpychan]

So is RCS essentially defunct?

Not defunct; it's useful for adjustments when you're not under thrust, and for correcting large rockets on ascent once you've dumped the aero controls.

But for my mun landers, I've mostly been using it for precise corrections on the final descent, and holding the lander steady as it gets settled.

[Xaiier]

Where did you launch from with this ship you have? Was that in Kerbin orbit as-is?

[Synapse]

I launched from KSC with 5 mainsails. So yes, Kerbin orbit with the full nuclear tank.

[Xaiier]

Your ship design isn't bad (though idk what the tank you meant was, the one you said doesn't exist) if its what I think it is (aside from ION engines, you don't want those).

Depending on how fancy you want to get you can decently improve the DV of that craft through various methods, but a simple solution to give you tons more DV would be to include a transfer stage designed to boost you to Jool and help initial maneuvers there.

On my personal super optimized ship, I have a transfer stage with an X200-32 tank and three nuclear engines. It gives me the ability to boost from Kerbin orbit to anywhere in the solar system, and still have a good bit left to slow down at the target. It runs out somewhere in orbit of the target body and I drop it, now left with my minimalist lander craft (something similar to your ship I think).

Also, do everything you can to reduce weight (down to command pod choice) and simplify your ship. Even an extra parachute can use up 50-100 DV.

Edited July 12, 2013 by Xaiier

[Xiphos]

I would suggest using a single more powerful engine than lots of smaller, more efficient ones. I think the weight for thrust ratio isn't the greatest. Your craft will be more simple, and stable. Also, about 3/4 of the way through your flight to jool, put a maneuver node down and get your PE within 200km. Shouldn't take very much Dv at all. (100 or so depends on your accuracy on the initial burn) Then when you first get into the SOI of jool, correct it again (this should need only very tiny movements) and definitely aerobrake. Correcting your insertion path early will save you so much fuel it will make your head spin!