Best nuclear engine setup for Kerbin - Mun/Minmus trips?

[OscarJade]

I just built a ship designed to take four untrained kerbals from my LKO station and land them on both the Mun and Minmus for the XP

It is built around the 4 man mk2 crew cabin, some of the MK2 liquid fuel tanks and a single LV-N with about 5000m/s delta-v

It is right on the cusp where a chemical engine might have been cheaper and easier over a single flight, but by the time it has done several trips the cheaper refueling costs will have easily made up for it.

I now have a prototype in orbit with the Mk2 2-man pod, a 4-man Mk2 crew cabin, two Mk2 LF tanks and 4 LVNs. After work I'm going to shake it down in LKO, rendezvous and dock with my station in LKO...and then take it to the Mun if all goes well I'm curious about what my fuel usage will be; total LF on board is 1600 gal. We shall see! In any event, it's massively cool looking

Edited June 4, 2015 by OscarJade

[Falconer]

One of the problems I've run into experimenting with the LV-N's is a severe shortage of LF only fuel tanks. You'd think that'd be low hanging fruit... no need to change the part model... just duplicate it and increase LF capacity and remove the oxidizer capacity. The only good thing about having a little oxidizer is being able to use verniers for RCS.

It might even be a good idea to split up the fuel tanks section of the menu... have one for RCS/exotic (xenon), ore tanks etc... put all the oddballs in one spot. Another for normal rockets, another for LF only.

Good example is the Mk2 fuselage adapters... the short and long to single ends both are stuffed with oxidizer... same goes for the short to double adapter. Even many of the size adapters that double as fuel tanks are rocket only.. leaving you with an inefficient fuel tank. I was experimenting with a LF only ramjet plus nuke space plane and this was a constant annoyance... either sacrifice the aerodynamics or the mass efficiency of the tanks.

Even the Mk3 Liquid fuel fuselage... great... except the Mk3 to large/extra large adapters all pack you got it... extra oxidizer tanks....

[moronwrocket]

Dang, I guess I should have paid more attention. I created a "standard" orange tank with 2 4 port docking "rings" around it to use as tankers/pushers, and recently swapped the Poodle on them for a Nuke. I guess I should have used LF only MK 2 tanks. But they aren't nice and symmetrical.

I'm sending a fleet to capture a Class E right now, with 1 ISRU with 2 of the nuke/orange pushers, and a separate 'tug' that is a nuke/orange with a Klaw. The plan is to move the 2 extra pushers from the ISRU and dock them with the tug. I also brought along 4 reaction wheel drones - each has 4 of the large reaction wheels and 1 Klaw, to separate my torqueing forces from the pushing forces. They'll be spread around the 'roid in a ring 90* from the tug.

[davidpsummers]

Unless I got it wrong, you need to leave your tanks 1/2 full (only fuel, not oxidizer, since it won't use oxidzer) which is a hit on how much fuel you have for a given based (empty) weight of the tank?

It sort of leaves them too heavy for small craft and too low thrust for big ones. I will probably go to reusable craft launched from orbit before I have a use for this.

These things were suppose to be the center of manned mission to Mars (before budget cuts). Ie, the next big thing. They feel like now they are a niche curiosity.

[Edit]

I guess there are the fuel only ones for the planes. I played with them, but they are large in size for the amount of fuel. I end up stacking them up to a point where I wouldn't try and launch anything that wobbly.

Edited June 5, 2015 by davidpsummers

[Randazzo]

Since I see a lot of suffering due to lack of proper fuel tank availability, I'll just leave this here.

[Acet]

Thanks all! What I would like to use is a 3-man command pod plus the 4-person hitchhiker container...I'm sure that means larger fuel tanks for four LVNs. I built this with 2 LVNs and a 2880-gal red tank, and it used up most of the fuel just getting to the Mun My chemical option would be a red tank with a Poodle. Either way I can refuel them at any of my three orbital stations, the main expense of course being station refueling runs (I'm not drilling/making my own fuel yet).

My bulk kerbal training vessel is a bit like that, with the 3-man command pod and 1 hitchhicker. It was used to train kerbals up to 3 starts, which means landing in Minmus and planting flag, flight to just outside Kerbin SOI and then return to Kerbin passing through the Mun's SOI (no landing on the Mun, not even orbiting).

For propulsion and fuel it had a Poodle, one of those 1/2 orange tank fuel things and 4x FLT-400.

I did refuel it on the surface of Minmus (since I have a mining op there) but I don't think it was needed since I had a lot of fuel left when I got back to Kerbin. However, this setup would not have had enough dV to land in both the Mun and Minmus on the same trip without refuelling.

I'm finding it strange that you managed to burn a whole orange tank just to get to the Mun. With LV-Ns you only need Liquid Fuel. Did you emptied all the oxidiser from that tank?

By the way Mk1, Mk2 and Mk3 liquid fuel tanks offer a better dry mass to full mass ratio for carrying liquid fuel around than any of the normal tanks.

[OscarJade]

My bulk kerbal training vessel is a bit like that, with the 3-man command pod and 1 hitchhicker. It was used to train kerbals up to 3 starts, which means landing in Minmus and planting flag, flight to just outside Kerbin SOI and then return to Kerbin passing through the Mun's SOI (no landing on the Mun, not even orbiting).

For propulsion and fuel it had a Poodle, one of those 1/2 orange tank fuel things and 4x FLT-400.

I did refuel it on the surface of Minmus (since I have a mining op there) but I don't think it was needed since I had a lot of fuel left when I got back to Kerbin. However, this setup would not have had enough dV to land in both the Mun and Minmus on the same trip without refuelling.

I'm finding it strange that you managed to burn a whole orange tank just to get to the Mun. With LV-Ns you only need Liquid Fuel. Did you emptied all the oxidiser from that tank?

By the way Mk1, Mk2 and Mk3 liquid fuel tanks offer a better dry mass to full mass ratio for carrying liquid fuel around than any of the normal tanks.

No, I foolishly left the oxidizer in, so I was hauling a lot of dead weight i did end up going with 2 Mk2 LF-only tanks (see post that will follow this one) and got much better results.

- - - Updated - - -

I now have a prototype in orbit with the Mk2 2-man pod, a 4-man Mk2 crew cabin, two Mk2 LF tanks and 4 LVNs. After work I'm going to shake it down in LKO, rendezvous and dock with my station in LKO...and then take it to the Mun if all goes well I'm curious about what my fuel usage will be; total LF on board is 1600 gal. We shall see! In any event, it's massively cool looking

UPDATE: Got home last night and did the shakedown/docking with my station, which orbits Kerbin at 200k. Only then did I consult Kerbal Engineer (too late) and found that the vessel's total Delta-V, with 4 LVNs, was a disappointing 2400-ish

So...back to the drawing board (thank you, quicksave before launch!)

So the new version of my reusable transport spacecraft, dubbed Falcon, carries only 2 LVNs...and I gained another 1000 Delta-V, for a new total of 3400 or so, with 510 gal of monopropellant on board. Not spectacular, but serviceable for runs to Mun and Minmus