Creating a manned ion propelled interplanetary vessel

[Uberdude9001]

I've been trying to create an ion propelled interplanetary ship for some time now. I can't seem to get them to work in a satisfactory manner. Should I use a large amount of batteries for energy storage and a single PB-NUK to perform my maneuvers or should I attempt to power them the entire time using solar panels? I've tested both concepts using small probes and can't decide which method is better for a manned vessel that is being sent on an interplanetary mission. Not being able to fire your engines on the dark side of a planet is unacceptable because that may be needed to transfer between planets. At the same time being unable to achieve the required delta V due to low charge is also unacceptable.

[tavert]

The solar panels have a much better power-to-weight ratio, but require careful planning of your maneuvers to not be on the dark side of any planets/moons. You would need about 20 RTG's to sustain one ion engine at full throttle, which would be quite heavy.

[Shrike42]

Well... once you're into Kerbol (the sun's) sphere of influence, you won't need to worry about being blocked by other planets. But while you're orbiting, you are at the mercy of the planet's umbra.

Given that ion engines are extremely hungry for power, you'll want to have all of the above. Solar panels, huge stacks of batteries, and reactors. Ion engines are for burning for LONG periods of time with low output, so you'll probably want to make a girder structure for the body, add a lot of engines and xenon, and cover everything with solar panels. You can hide the reactors inside the girders, too, if you're interested in it looking good.

You'll be spending a lot of time looping around Kerbin and burning at the periapsis, but once you've escaped, you'll be good to go whereever. Very slowly.

[Uberdude9001]

The solar panels have a much better power-to-weight ratio, but require careful planning of your maneuvers to not be on the dark side of any planets/moons. You would need about 20 RTG's to sustain one ion engine at full throttle, which would be quite heavy.

I hadn't considered using multiple PB-NUKs. Using my current designs I can achieve 300m/s of delta V per battery charge on my current probes which carry a single PB-NUK, however I'm not sure how well this will scale up to a manned craft. Another problem I encountered was placing the large solar arrays in a way that would allow all of come into contact with the sun's light.

[DMagic]

I agree that solar panels are the way to go. I put some batteries on ion probes, but just enough to give me a little leeway for times when I'm behind a planet or a I can't orient the solar panels in the right direction. They burn through energy so fast that batteries would almost never be an effective way to power them. You just have to be careful with timing your maneuvers and it will take many short burns to build up enough velocity.

My ion engine landers thread has lots of different examples of the types of crafts that work well. They can't be used long in the shadow of a planet or moon, but through careful timing that was never really an issue.