JerseyChris

An update for those who helped (I always like it when people do that): tankers rendezvoused with the capsule. One with extra monoprop which was used at first opportunity (thanks Kryxal for the “burn the worst fuel first”) and one without extra monoprop launched after this thread (thanks everyone). Tankers linked up with each other approx half full and one was deorbited, the other was topped up with LF and docked with the capsule, and everyone is on the way home with plenty of dV. My first return from Moho. My plan for this mission was basically one of “launch them first and figure out how to get them home later.” Second part accomplished. Fun fact: This was briefly considered as an Apollo mission mode. VERY BRIEFLY.

Made much harder by the fact that I’ve got to squeeze KSP in with two kids and a third on the way, a full time job, and all the problems that come along with maintaining a house. I’m lucky if I can get in two hours a week. And given my current mission schedule most of THAT is loading screens and correction burns...

I actually thought about that but I run parallel missions and don’t use any mods (even alarm clock) and my Jool station flotilla is arriving right about now so I’ve got a bit too much on my plate to launch another station project. After the Jool station gets put together I’ll probably do that. Right now I’m running 5 separate major missions composed of maybe 20 individual spacecraft so... yeah. I’m like, “OH! Right! The Duna Rover is entering atmosphere today! I forgot all about that!”

My first space station was hilarious. In a horrible orbit 100x400km, parts stuck on every which way willy nilly and way too many docking ports if you could get to them through the forest of solar panels and engines and whatnot poking out. It looked like an angry porcupine.

Gotcha. I’m convinced now. Thanks for the explanation and your time. Happy travels, I’ll leave the monoprop at home and off we go to rescue the poor guy and gal (at least I hope there’s only two of them, who knows, they’ve been unattended for a while) who have been orbiting Moho for a year and a half or so.

“Better to have more delta v and burn it slightly inefficiently than try to make up TWR by burning monoprop.” THIS is the answer I was looking for. Also Kryxal is right, I didn’t really consider how small Moho’s gravity well is either. Extra monoprop goes out the window then. Thanks everyone. I am still curious where the “tipping point” is though. There has to be some point (which would of course vary by body, isp, TWR, etc) where a lower efficiency is compensated for by the TWR. To put it another way, there’s a place for engines other than ions, nukes, and ants for certain capture burns, I am sure. I just don’t know where it is. The monoprop would be coming from Kerbin. I don’t want to add another nuke engine because they’re so heavy. The existing monoprop is budgeted for RCS maneuvers. “Burn the worst fuel first” please explain.

So, you’re saying the weight of the monoprop costs more than the benefit I’d get from having a higher TWR? The quicker I can complete my burn at Moho periapsis, the more efficient it will be because of Oberth effect. Additional monoprop would help me complete that burn more quickly. And it weighs a lot less than strapping on an additional nuclear engine. Yes but we are ignoring the Oberth effect which is what generated the question. I get that nukes are more efficient. See my above reply to see what I mean. It’s an Oberth effect question. I get that’s it’s less efficient. But does the increased Oberth effect from being able to complete my burn in a shorter period of time outweigh the decrease in efficiency and increased mass? Remember I’m coming into Moho like a bat out of hell so TWR is important. To put it another way, if you’ve got a 20 minute capture burn on a fast hyperbolic trajectory, that sucks from an efficiency standpoint. You’re hardly doing any of that burn at periapsis. A say 0.1 ton weight penalty or say a 5% hit to ISP would probably be well worth it to cut that burn time to 1 minute. A 10 ton weight penalty or a 50% hit to ISP probably wouldn’t be worth it. Where is that point in the middle is my question. The craft is simple. One large Mk3 fuel tank with adapters on either end. Chock full of LF only, no ox. Two nukes. Probe core and docking port. Associated normal RCS and four O-10s. The craft hasn’t been launched. Would adding monoprop to add to my TWR at a critical point (capture PE) be worth the weight penalty of additional low efficiency propellant? Or should I add another heavy AF nuke? Or do nothing? Remember Moho has such a small SOI and the capture burn is so long that TWR actually matters here. How much does it matter?

LF tanks topped up. But I’m trying to deliver as much LF as possible to low Moho. My two nuclear engines can only deliver so much thrust. Is the mass cost of additional monoprop to increase my TWR at periapsis by burning the O-10s worth it? Lighting up the O-10s at periapsis to assist with the capture would be terribly inefficient from an ISP standpoint but excellent from an Oberth effect standpoint. My question is, at 40km above Moho, which effect rules?

I’ve got a tanker that needs to insert into low Moho orbit from Kerbin. Simple craft. Giant fuel tank or two, probe core, docking port, two nuclear engines, and an RCS system. The craft has four O-10 Puff engines to assist with orbital rendezvous and docking. My question is: when doing my insertion burn from Kerbin, is it worth it to include some extra monoprop for those engines and burn them at periapsis? Is the added weight of a lower efficiency propellant worth the gain I get from being able to complete my burn in a shorter time? For reference I’m trying to insert into a 40km orbit around Moho. Note that the four monoprop engines are not added weight, they were already there.

Agreed re: stats being swapped for the Wolfhound and Skiff. I was curious about how they modeled the AJ10 so the first engine I looked at was the Wolfhound (the “10” in the name gave it away) and was like “the heck is with the Isp?” Then I checked out the skiff (the RE-I2 made me figure in game analog for the J-2) and thought “Wow, they clearly got those backwards.”

Placed my first kerballed interplanetary craft into Duna orbit! It's a lander only, the return ship is following way behind it. Way more behind than I had planned. It seems that on the first ship SOMEONE had neglected to put a decoupler below the transfer stage so it got stranded in a highly elliptical KO. So another ship had to be launched with the correct part (thankfully we don't have taxpayers to answer to) and link up with the first defective return ship to haul Traski on board before setting out for Duna. So Traski and what's his face in the second ship are going to rendezvous eventually with Valentina in the lander after she gets back into low Duna orbit, but she's probably going to be annoyed they're not three days behind her, more like three months.

It's quite compelling how we can get attached to some of those little green guys hahaha! Great story so far, I want to see if Seeald makes it home.

Yikes. Havent experienced that gem myself yet. Does the craft have a fairing?

Delete all EAS-4 struts on payload and use autostrut instead. Worked like a charm for me. Read somewhere that in 1.3 fairings don't like struts on the payload for some reason.