Omuamua is an asteroid discovered by scientist in the last year which had an strange behaviour as it accelerated during its close orbit on the sun doing a gravitational assist. It hit the news so many times that I guess everyone knows about it.
There’s a lot of people still believing this has to be an alien spaceship or probe, because, what else? Scientist have debunked each one of the alien theories one by one and seems pretty clear that it is just a rock, and we just got lucky.
But let’s go crazy, because it’s fun! Repeat with me: it’s aliens. It has to be aliens and there’s no other option!
So to prove those scientist wrong, let’s build our own version of Omuamua in Kerbal Space Program. I have been posting some entries lately about this game, it’s a game and a space exploration simulator at the same time. It contains a Solar System scaled down, with its own planets and so, but it resembles a lot to our own.
I’m going to make use of different mods to emulate futuristic technologies, and also I’m not going to fly most of them, as launching thousands of tons is really hard and time consuming. Instead I’m going to defer to the numbers reported by Kerbal Engineer Redux. Also, I’ll oversimplify the maths involved because it should be enough for our purposes.
We want a spaceship or probe that is capable of leaving our Solar System, reach a near star and slow down to be able to do a gravitational assist. It has to be done in a time-frame that is meaningful for our species.
The nearest stars are about 1.5 light-years away. This number will be our target. We want to get there in 200 years or less; mainly because in that time another better technology could overtake the craft, and anyone living in here will probably no longer remember how to communicate with it.
The required speed to reach that star in time we can just do:
v = c / 200 * 1.5 = 2248 km/s
In KSP terms, this means we need a DeltaV of 2248000m/s to get that velocity. But then we need to slow down! so we need the same DeltaV again before reaching the star. This, of course assumes that the destination star moves at the same speed and direction over the space as the Sun.
So the desired DeltaV we’re looking for is 4497000m/s, but I’ll round it to 4.5 Million meters per second. Also this does not take into account the time required for accelerating or deccelerating; in the ships I’ll be building they will be accelerating for years, so the end result will be higher than 200 years.
So, the mission in short is: Build a KSP probe that has 4.5 million m/s DeltaV. I don’t care on launching.
First try with almost no mods
We will need something to communicate, so let’s add a big antenna. And obviously huge batteries and solar panels to get the energy…. Wait a second! There’s almost no sunlight when we’re outside of the Solar System! so I’ll need to add a nuclear reactor instead. Sadly the NUK is not enough to power anything, so I’ll go with solar panels for now. Add reaction wheels, and a huge bunch of Xenon tanks, and the Ion Thruster. Ready to go!
We got around 36km/s of DeltaV! not bad at all. But this is only a 0.8% of the speed required to get there on time. Let’s go the Kerbal way and BUILD BIGGER
Let me now use the Rescale Everything Mod to scale those silly Xenon tanks up, add some staging, and change the engine design so we don’t lose the engines on staging.
We reached now 163km/s! This will take around 7-8 months of acceleration to deplete the Xenon tanks. Looks like a lot, but this is only 3.6% of the DeltaV required. Still far from there.
Adding more stages and bigger tanks will be ridiculous here and it will give us around 40km/s extra. So no point on even trying it. This beast is already 3 thousand tons and it would need to be assembled in orbit and fuelled in orbit, requiring around 8 trips at least and I bet that these launches would look insanely huge and expensive.
Near Future Propulsion
So this was not enough. Clearly we need a better ISP in our engines so I’ll install Nertea Near Future mods. In fairness, the Ion Thruster in stock has only 4200 in ISP, which is what we have ready now, but in the upcoming years this may change drastically. Aliens have better technology for sure!
Near Future Propulsion adds an Ion engine with an ISP of 19200s. Before any of you scream “that’s cheating!”, please let me refer you to this Wikipedia page: https://en.wikipedia.org/wiki/Dual-Stage_4-Grid
There you can see this engine is capable of an ISP of 19300s. It is not ready yet. Those two ISP numbers are pretty close, so from here comes the inspiration for the Jewel-4 from Near Future Propulsion.
OK, let’s build now! With nuclear reactor, please!
Now I got 229km/s! We’re getting there… or are we? This is still just 5.1%. But remember in Kerbal we can BUILD BIGGER!
560km/s, still 12.4% of our target. Wonder if I can add more fuel without exceeding the hangar…
I got 897km/s, awesome! Probably the most ridiculous DeltaV reported in Kerbal that most players has seen, ever. 19.9% of our target. There is 36,000 tons on Xenon fuel to deplete. How much it takes? 12 years for the four tiny engines that are hidden behind the tanks.
The first stage is composed of 6 tanks of 20 meters each, 39,000 tons of weight.
These engines above are so lame… real Aliens have much MUCH better technology. They would go all-in nuclear for sure!
We have available in Kerbal one Mod called KSP Interstellar Extended which includes all kind of crazy nuclear and antimatter designs that never leaved the paper. If you want to explore other stars in Kerbal, this is the mod to go! (spoiler alert: there aren’t any)
Let’s get on and start building. What do we need? A working fusion reactor, a converter to get that energy back to electricity and a VASIMIR-500. Also a pair of huge hydrogen tanks:
VASIMIR-500 has a maximum ISP of 29560 in the game, given that is fed with liquid hydrogen and the thrust is 5% or lower. One of the key features of a VASIMIR (they’re real) is that better trust to weight ratios can be reached at expenses of lowering the ISP.
But, this particular engine is way far off from reality. Usually they have an ISP of 5000s while using Xenon. Using Hydrogen, they are going to be much more efficient, but I cannot find any resource proposing more than 10000s of ISP. So without any paper or research giving support for this, I would say that this one is pretty cheaty and purely fictional.
Anyway, easily I could get a DeltaV of 388km/s, and should be possible to increase it scaling up. The problem though is, Hydrogen is really low density and those huge tanks only hold 67 tons of hydrogen together. So the problem now is going to be the required space to fit the enormous tanks.
This setup only gave 825km/s, which is roughly the same as with the Grid Thruster from Nertea’s mod despite having almost double ISP (29650s). This contains 17,000 tons of hydrogen.
There are two reasons on why it failed short. First, Hydrogen is so light that even for the biggest tanks, a big part of the weight is still the container. The second reason is there is no staging, so the tanks cannot be dumped as it goes. It is really difficult to design stages when a single stage already takes the whole VAB.
We could build some stages and use Helium instead. Being slightly denser, it will pack more, will be better for fuel mass to container ratio and will make me able to build some stages.
Now this thing has even less DeltaV. The ISP lowered to 20977s due to the usage of helium instead.
As we can see, we’re going backwards. This is even worse than ever. This interstellar mod, doesn’t have anything really good?
Well, it has the so called Magnetic nozzle. Something really huge that takes ionized hydrogen and magnetically pushes that to a 26% of the speed of light. If this is not science fiction, please let me know what classifies.
This is only using 113 tons of hydrogen and I got an astounding 8067km/s of deltaV. The Trust to Weight ratio is zero. On the other hand, this is 179% of what we needed, so almost doubles the needed. Good, right?
Well, no. Despite I had to add a Stellarator Fusion Reactor of 40 tons generating 65 Megawatts of energy, even if that is real someday (I doubt it), I don’t think that is enough to accelerate Hydrogen ions to 26% of the speed of light. Or if it is, the magnetic forces could rip the spacecraft apart easily.
Back to reality. There was something called Orion project, the idea is simple and it was proven to be working at a really small scale: shot nuclear bombs behind the vehicle and use pistons to receive the blast and accelerate by “surfing” on top of those.
There’s a Kerbal mod for this, simply called “Project Orion” Nuclear pulse engine. It worked well, but I updated recently my KSP and I’m not going to bother with it for now. They’re really powerful and the ISP is off charts.
The wikipedia article about Project Orion is enlightening. Ships with it could reach Alpha Centauri in 44 years. And this technology is doable currently. Amazing!
But well, no one wants to put 300,000 tons of atomic bombs into orbit and even with that, no one will agree to start those engines unless is really, really, far away.
But we’re talking about building Omuamua. Did we see any nuclear explosion? Scientist were confused because they didn’t see the typical jets from comets (gases), so we can assume there was no nuclear detonation for sure, as that would be alarmingly easy to be seen.
A few scientist proposed that Omuamua could be a Solar Sail, and that would explain the acceleration we saw. But even SETI researchers have laughed at that option. Why?
Well, a Solar sail has to be accelerated using lasers in order to get good speeds. This is called beam-powered propulsion and currently is the most probable technology that will be used to send probes to other stars in the future. This is also one of the “alien” explanations as well for the FRB phenomena.
But this technology has a pitfall when you compare it to Omuamua. The so called asteroid was entering our Solar System around 25km/s (I don’t recall the correct number now). If it was a sail coming at more than 1% of the speed of light, how did it slow down? That’s simply not possible.
Also, scientists describe Omuamua as having a cigar-alike shape. Does this have a cigar-alike shape?
So it seems pretty clear that IS NOT a solar sail. So?
Omuamua is an alien spaceship and Kerbal Space Program is not powerful enough to emulate it. They came, saw our lame television programs and ran as fast as they could.
Why? Because I said at the beginning that there was no other option than aliens and I had to stick with it until the end.
Have fun playing Kerbal!