Captain’s Log, Stardate 1502.19: The ion engine continues to run smoothly. With its thrust, we should be able to exit the solar system at almost exactly 60 km/s. With less than 20% of our xenon remaining, the crew is becoming restless in anticipation of their time-warp hibernation.

Current distance from the sun: 0.0000003 lightyears

So, yes, 24 hours later, we’re still under thrust! The physics engine is running slightly below realtime; I assume because there are too many parts on my ship (I’m doing this mission without mods, but by gosh I wouldn’t mind having one huge xenon tank instead of 40 tiny ones). While we’re still close to the sun, we should take a closer look at the vessel that’s going to be keeping our Kerbals alive for the next several thousand years.

Starting from the back of the ship on the left side of the picture, we have the ion engine, the 4-person crew capsule, the fuel tanks and power systems, the overly-large RCS monopropellant tank, the reaction wheel, the battery, and finally the computerized guidance system. I could have gotten away without a number of these parts, notably the monoprop tank and the big truss down the middle. But what’s the point of even building spaceships if you can’t make them look at least a little bit cool, right? I stopped short of putting fins and a nosecone on it, at least, and believe me I was tempted.

In real life, radioisotope thermoelectric generators are a great way to make electricity for long voyages into the colder regions of space (i.e. farther from the sun, where solar panels are less effective). They work by capturing the heat from a decaying radioactive element, and using it to generate electrical energy. Such nuclear materials have a characteristic half-life, which is the time it takes for half of the atoms to decay. For example, the plutonium used in many real-world RTGs has a half-life of 87.7 years, meaning that any space probes launched in 1928 are still producing half as much power as they did initially. This makes it extremely practical for long-duration missions. (One may note that there were no space probes launched in 1928. And plutonium was still 12 years away from being discovered. But I digress.)

RTGs in Kerbal Space Program are magical, and they maintain a consistent power output indefinitely. This is good for us; we’ll be able to keep the lights on the whole way out.

Ion engines are totally sci-fi, right? Or, “f!#&ing electromagnetic thrusters, how do they work?”

Ion engines are real! They take ions – particles with an electric charge – and use electricity to accelerate them backwards. Ions go backwards, spaceship goes forwards, Newton is happy. Since the ions can be made to move very very fast, these engines are incredibly efficient compared to regular rockets. With the same amount of fuel you can achieve something like ten times as much delta-v. The drawback is they produce a very small amount of thrust. Now, I see all the KSP players nodding their heads and thinking “oh, yeah, it takes forever to get anywhere with an ion engine.” Oh, my sweet summer child, you have no idea. Kerbal ion engines, which max out at 2,000 Newtons, are THOUSANDS of times more powerful than real ones, which are typically measured in milliNewtons. It takes literal months of thrusting to achieve significant changes in velocity. But that hasn’t stopped them being used on various space probes, including the Dawn mission which is currently closing in on the dwarf planet Ceres.

However, the upside is that they really do have that sweet blue glow. Totally worth it.

It should, hopefully, be clear that this spaceship would never work in real life, for any number of reasons. Sure, if we had immortal astronauts who required no food, and a magical infinite energy source, we could (relatively) easily launch an interstellar mission. But with the constraints of the real world, it becomes quite a tricky engineering problem. It’s not impossible, by any means, just Hard with a capital H. In tomorrow’s post, I’ll go into some of the proposed technologies that could, some day, take humanity to the stars. (Project Orion fans stay tuned!)

Bonus cinematic-looking screenshot of the K.S.S. Polymakria (yes, I finally named the ship!):