Duna to Ike Shuttles

[AtomicTech]

I'm currently planning two space stations with one around Duna and the other around Ike. I'm also planning to make shuttles like the title suggests. I'm torn between using either Ion or Liquid Fuel/Oxidizer propulsion for the four shuttle craft. Can I please get some pros and cons about engine types or something else entirely. (I do not use modded parts save for reserve electricity from AmpYear.)

[Gargamel]

Question moved to Gameplay questions. 

[Guest]

Ions are only really any good for tiny probes/satellites IMO as TWR is so low (not to mention constant need for electricity). Therefore I'd go LF/O myself.  With Duna part of the equation maybe the Aerospike or Rapier could be a viable option.

[jost]

If you are not using any mods for adding radiation I would use nervs for efficiency. If you use a mod with added radiation you could shield the shuttle so they are not an issue.

[18Watt]

With ISRU (mining fuel), you can get all the LF and O you need on either Duna or Ike.   I would not bother with high-ISP engines if all you want to do is go between Duna and Ike.  I suspect you will find that frustrating.

Personally, I would use a conventional LFO engine.  I personally like the Vector.  The Vector has a lot of power, and is heavy and expensive.  If you don’t need that much thrust, pick a smaller LFO engine- even Terriers work well on Duna.

Your description is too vague to give a better answer.  Is your shuttle just carrying a single Kerbal in a lawn chair?  If that’s the case, one or two Terriers are probably overkill.  On the other hand, if your shuttle carries 30 Kerbals and a lot of fuel, you need a bigger engine.

Is it possible to use Ion engines?  Probably, but why bother?  In stock KSP all your Xenon needs to be shipped from Kerbin, but you can get all the LFO you need anywhere with ISRU.

I’ve used nuke-powered landers on Ike, but the performance was marginal.  Personally, I wouldn’t bother using nukes on a vessel which only had to go between Duna and Ike.

[jimmymcgoochie]

If you want to go from orbit of Duna to orbit of Ike, try the Poodle- high ISP even landed on Duna, decent thrust for a moderately sized vessel and it isn’t too big or heavy either. You can even land on Duna’s surface and fly back again with a Poodle engine, depending on the mass and fuel of the vessel it’s attached to. Other similar engines are the Terrier at 1.25m or the Cheetah (from Making History) at 1.875m, but you won’t need anything bigger than that just to shuffle crew between Duna and Ike and I’d recommend going for the smaller, lighter engine to i prove your delta-V even if that makes it have a lower TWR, which is less important in this use case.

Ion thrusters are only good if you’re flying a small probe over very long distances; they can’t be refuelled by ISRU in stock and their thrust is weak (though still ten thousand times higher than in reality!) so are poorly suited to crewed vessels.

While the NERV does offer good ISP it’s also heavy, expensive and the fuel tank options are limited- either you use normal tanks and waste the majority of their capacity by emptying the oxidiser, or have to use the few fuel-only tanks available which can cause their own problems.

Regarding your ISRU setup- I’m firmly in the “refine where you mine” camp as ore is incredibly heavy and not that easy to bulk transport, especially trying to fly it into orbit. Put your IRSUs on the same craft as your drills and make the fuel/oxidiser on site, then carry those in a dedicated tanker craft to the waiting orbital crafts/stations instead of hauling that heavy ore into space and wasting a good chunk of the fuel you make in orbit just filling up the ore hauler for its next trip.

[AtomicTech]

To give y'all more specs, before I made this post the spacecraft shuttles were a Onion Command Pod with a PB-X750 Xenon Container, 80 units of monoprop, 4 Z-400 Rechargeable Batteries, 4 Dawn Thrusters, and two large solar panels. It has a small docking port, an Advanced Inline Stabilizer, and 4 RV-105 RCS Thruster Blocks.

[18Watt]

It sounds like you are just going from orbit to orbit then, and not actually landing your shuttle on either Duna or Ike?   In that case, Ion engines are obviously a workable solution.  However, I still would go for LFO engines, for the same reasons mentioned previously.  

[AtomicTech]

5 hours ago, 18Watt said:

It sounds like you are just going from orbit to orbit then, and not actually landing your shuttle on either Duna or Ike?   In that case, Ion engines are obviously a workable solution.  However, I still would go for LFO engines, for the same reasons mentioned previously.  

Awesome, thanks!