Extraplanetary construction is no joke. I have been been working on this thing for over a month. It is the most ambitious project I’ve undertaken in KSP so far. And it has been immensely rewarding. My goal was to build a modular moon base on the surface of Minmus that included several major modules: Command, Communications, Science and ISRU. This is Shelley Base. It’s named after the romantic poet Percy Bysshe Shelley. For those keeping track, Keats Station was named after John Keats.
I looked at a number of approaches for moon bases. The simplest would be to just settle a collection of landers roughly near each other and call it a base. Fair, as far as it goes, but not really a construction project. Another solution would be to utilize some of the base-specific mod part packs. These are appealing, and I may look into this in the future. But this time around, I wanted to work with parts I was already familiar with. I wanted a station that was contiguous, where my kerbonauts could move from section to section without needing to go outside. I wanted it to stand on its own legs above the surface. And I wanted it to look cool.
This left me with the third choice. I could try to adapt the orbital construction techniques I practiced with Keats Station and Atlantis 1 to microgravity. I looked at Kerbal Planetary Base Systems, USI Kolonization Systems (MKS/OKS) and the Stockalike Station Parts Expansion before deciding on a combination of parts from the Stockalike Station Parts Expansion and Near Future Construction. I was familiar with these parts from the Atlantis project and I’ve really grown to like the aesthetic of them when used together.
I met a traveller from an antique land
Who said: “Two vast and trunkless legs of stone
Stand in the desert. Near them, on the sand,
Half sunk, a shattered visage lies, whose frown,
And wrinkled lip, and sneer of cold command,
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them and the heart that fed:
And on the pedestal these words appear:
‘My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!’
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.”
The next step was coming up with a design. I knew the features that I wanted to include. I wanted a generally horizontal layout– like my early Minmus station design. I tried out a number of configurations until I settled on something I liked. The next step was more challenging. It’s easy to just click parts together in the Vehicle Assembly Building or the Spaceplane Hanger. The difficult part is breaking the design up into modular pieces. I had to ensure that the pieces could been lifted into orbit independently, had appropriate connection points for construction, and didn’t make a rocket overwhelmingly unwieldy.
In parallel, I worked on designs for two construction vehicles: a skycrane and a crawler. The skycrane lifts modules from orbit to the surface. The crawler moves modules into the required positions on the ground.
The crawler design was straightforward. I needed something low and flat that could fit underneath my modules to attach. Modules need just enough clearance for the crawler and then the docking modules would lock them together. The modules permanent landing legs serve double purpose as a jack. When the legs are retracted the entire piece settles onto the wheels on the ground and can be driven into correct position. When the legs are deployed, the docking port just barely clears the port on the crawler. I experimented with various wheel configurations. I used different wheel types and placements to make standard, high- and low-riding crawlers. I even designed a crawler using Infernal Robotics that allowed for a form of variable clearance. In the end the small mid-range crawler functioned most consistently– but introduced the requirement that all the base modules must have almost exactly the same clearance underneath. That affected the overall base design.
The skycrane design was more complicated. I knew rough dimensions required for the skycrane’s engines to clear the expected cargo. I estimated my requirements to include safely landing 15-25 metric tons of cargo from orbit, return to orbit and rendezvous with orbital spacecraft. How to find the proper balance of thrust, loaded weight, unloaded weight, control and fuel reserves to handle the specific tasks? I anticipated staging a fuel depot in orbit to allow for multiple surface trips; it was the capacity testing that was challenging. The intended sphere of operation was Minmus orbit. My testing grounds were on Kerbin. Minmus has no atmosphere and minimal gravity (0.05g). Light engines with low-thrust and high-ISP engines are ideal. Except those don’t work well at all on Kerbin. Kerbin’s gravity is twenty times greater than Minmus. Kerbin also has a thick atmosphere. A skycrane that tests successfully on Kerbin will be considerably over-powered for Minmus operations.
I could always boost various designs to Minmus and test each one there. I rejected that approach. Too slow; too expensive. Too wasteful. Instead I mocked up a rough design, flew it on Kerbin and revised it a number of times– checking my current capabilities against what I anticipated on Minmus. Kerbal Engineer was particular useful for calculating available delta-V and thrust-to-weight ratios for various designs. The result was a practical, if somewhat overpowered skycrane. It carries far more fuel than it needs, and not enough RCS monopropellant for my liking. But it’s close enough, and capable of operating on Minmus and I hope the Mun and Ike.
With these constraints in mind, I finally completed an acceptable base design. It included a central control tower, a huge communications mast, a science laboratory, a habitation module, and a giant nuclear reactor to power it all. I laid it all out in the Spaceplane hanger, then cut it apart into modular pieces and reconstructed it on the green space beside the KSC runway. A bit of tinkering with parts placement and a lot of learning how to drive a little tractor with tons of moonbase strapped to the roof and only a few unfortunate accidents before I felt I was ready. Patience, always patience. Patience is key. All of this took over two weeks of serious gameplay.
So I had my two construction vehicles. I had my basic base modules. Time to put some stuff in orbit! All of the vehicles are robots; no kerbals. The crawler, the skycrane, the orbital fuel depot and all the booster rockets were designed to be remotely operated. Earlier this year I had completed my RemoteTech communications network around Kerbin, the Mun and Minmus. I was able to leverage that infrastructure for almost the entire construction project. Once I had the major pieces in place and connected, I planned to deliver some enterprising kerbonauts to turn the lights on and put on some of the finishing touches.
The orbital fuel depot went up quickly: two major fuel tank sections connected end-to-end, and then a cluster of RCS fuel tanks around the center spine. The RCS fuel tanks provided a variety of docking ports as well as a bit of separation from the central spine and any vehicles that might rendezvous with the depot. About this time is when I learned a valuable lesson about large construction projects. I was individually boosting each module from Kerbin directly to Minmus orbit. In hindsight, I think it would have been better to boost all the components to Kerbin orbit, connect them together in a temporary configuration for the trans-Minmus injection. Once the collection was safely in Minmus orbit, I could disassemble each piece and lift them down to the surface. With the exception of disassembly, that’s exactly how I’d moved Keats Station around the solar system– first from Kerbin to Minmus orbit, and then to Duna and finally to Ike.
But I didn’t. I also began to see the value of SSTO lifters like the Space Shuttle program. A reusable low-Kerbin orbit vehicle would have significantly reduced the launch costs. I just have not had much luck flying SSTO vehicles. So I continued to employ my fleet of single-use boosters built with the beautiful parts in KW Rocketry.
The Phase 1 launches, in sequence:
- Base Tower
- 4x Connection Tube Cluster
- 2x Base Crawler Cluster
- Communications Mast
- Science Module
- Hab Module
The communications mast included a small amount of solar panels and sufficient batteries to power the station through the night. This allowed for the first kerbonauts to descend with the Hab in launch 6 and board the station.
Phase 2 of the station construction comprised of the delivery of the powerful fission reactor from Near Future Electrical, and appropriate radiator fins. Additional kerbonaut engineers descended with the reactor and oversaw its connection to the station. Connection tubes set the reactor far from the Hab on the opposite side of the communications mast.
The reactor is a prerequisite for Phase 3: ISRU. The reactor provides ample power for the science laboratory and deep space communication antennas on the mast, as well as sufficient power to sustain twin ISRU converters. These two converters were lifted down from orbit and carefully– oh very carefully– installed on branches from the reactor.
The final phase, Phase 4, was the delivery of the Minmus mining truck and a huge fuel tank to store the output of the ISRU converters. With support of SCANsat satellites, the mining truck is able to explore the surface of Minmus, mine for resources and truck them back to the base for conversion into rocket fuel and monopropellant. The base can support four mining or tanker trucks and two fuel tanks, but is now a complete extraplanetary outpost.
Between each phase kerbonaut engineers removed unnecessary parts using Kerbal Inventory System (KIS) and Kerbal Attachment System (KAS). I did this for technical and aesthetic reasons. I wanted to keep the part count on my base low. Game performance decreases as part counts increase. Aesthetically I wanted to remove single-use docking ports and legs once pieces were connected in their final configuration. I’d never worked with KIS/KAS before. They’re very powerful mods, and the sort of functionality that I would love to see in the base game.
I kept a rough journal of the amount of time I’d spent working on each phase of this construction. Pre-planning, base design and construction vehicle experimentation totaled about 50 hours of gameplay over two weeks– not counting all the time I’d spent building the RemoteTech communication satellite network, or practicing the various orbital construction maneuvers.
Phase 1 took about eight hours over three nights. I thought delivering the reactor in Phase 2 would be simple. It was just one piece, but designing a booster for that payload took some time, and then I forgot to include an antennae and lost radio contact during the Minmus transfer. And then the first time I fired up the reactor, I forgot to deploy the radiators and the reactor overheated and exploded while I was working on delivering the ISRU converters in Phase 3. So, about six more hours and two more nights. By the time Phase 3 began, part count was growing and causing some game instability. It took ten more hours over four more days to get those converters attached. Designing them on the fly after I had decommissioned the Kerbinside model to save on part count didn’t help matters.
Abort, retry, fail.
Similar problems plagued Phase 4, compounded by designing a light booster that had to contend with a huge drag force on the nose. Eight more hours, at least. So, altogether eighty- to eighty-five hours over the course of at least a month.