Jool Mission Planning – Lander Design

Blaugust 2015 Day 23

Last night should have been my return to my multitasking experiment, and playing anything other than KSP which is what I’d played on Wednesday. But I had just watched the latest trailer for The Martian again and was in a space mood that Star Trek Online doesn’t really fulfill as it is more science fantasy and hard science.

Instead I headed back into the Vehicle Assembly Building to work on the next stage of my Jool exploration mission. My previous design work had been all about building a craft which would take three Kerbals from Kerbin to Jool and allow for refueling at an automated refinery I’d already place at one of Jool’s moons. But I still needed to build a landing craft to take along. After all it would be a waste for three Kerbalnauts to spend years traveling out to Jool and not get a chance to plant flags on at least one of the moons.

I’m actually planning something more ambitious than that, which is called a Jool 5 expedition. Basically, landing on all five moons with a single mission. Something that was much more challenging before Squad added ISRU (in-situ resource utilization) equipment to the game, so now it’s possible to set up refueling locations.

Even knowing I can refuel though, I needed to design a lander that could handle landing and taking off from all five of Jool’s moons. Some like Bop and Pol are relatively easy. Both are small, low gravity satellites, and have no atmosphere. Vall is bigger but not too difficult. Laythe is more of a challenge. Its gravity is 0.8 that of Kerbin and has an atmosphere like Kerbin does which will help with landing since I can plan to use parachutes not burn a ton of fuel to land. The real challenge of the five will be Tylo. It also has a gravity 0.8 times Kerbin, but it has no atmosphere so the entire landing will require fuel, which means twice as much as will be needed for Laythe.

I had a basic stage for the Tylo descent, but was trying to put together an ascent module that would also work for Laythe and the other moons. This is my first design. To take off from Tylo I need better than 1.0 TWR (thrust to weight ratio) and at least 3070 delta-V. The only problem is I don’t like the look of the big tank sticking out.

KSP 2015-08-23 21-01-05-75

 

I started over and played around with some other ideas. The problem was that using more smaller tanks meant more weight for basically the same amount of fuel, which meant a bigger engine or more engines. Which is not horrible, but anything that could take off from Tylo would be way over engineered for the other moons. And I’m expecting to reuse the craft for Bop quite often after completing the exploration mission. I finally settled on the following design. Not only do I like the look of this craft better, it actually has better TWR and a 1 more meters per second in delta-V.

KSP 2015-08-23 21-01-45-48

 

So now that I have my landing craft, I need to revisit my exploration ship. The current ship uses nuclear engines which run on liquid fuel only, whereas the motor on my landing craft requires LFO (liquid fuel and oxidier). So I’ll need to add a tank to the ship to allow refueling of the lander after it leaves a moon an docks. That will of course mean I need to adjust the fuel and motors on the exploration ship as well. It’s a lot of planning but that’s part of the fun of the game for me.

Here’s the completed lander with the Tylo descent module.

KSP 2015-08-23 21-03-18-84

 

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