The Raketti (Finnish for “rocket”) is a really fascinating puzzle; rather than direct spatial reasoning like a dissection puzzle, or the working memory involved in letter or number based puzzles, the Raketti encourages lateral thinking as a means of problem solving. And it can be really interesting and amusing to watch people try and come up with the solution. Which is, of course, to blow on or across the top with the strongest gust of breath you can muster.
So how does the Raketti work? That’s a matter of some debate among puzzlers and physics enthusiasts, but it appears to be a combination of two factors: Bernoulli’s principle and a sort of “air piston” effect. Both of these are at work when the center pops out of the block, but which one is more important seems to be based on the angle at which you puff at the puzzle: if it’s from more to the side or from above.
The conical top, which has some relation to the shape of an airplane wing, gives you the clue that part of what is happening is due to the Bernoulli effect; you’re basically making the interior piece into a wing by increasing the speed of the airflow over it. Bernoulli’s principle tells you that an increase in the speed of a gas occurs simultaneously with a decrease in pressure. When you blow across the Raketti, you’re decreasing the pressure in the area right above it – and since the bottom of the block is still at atmospheric pressure (the air there isn’t really moving), the center rocket pops up.
If it was just Bernoulli at work, how fast would you have to get that air moving? Atmospheric pressure is 101 kiloPascals (kPa), and given the mass of the rocket, the pressure needed to raise the rocket is probably about 200 Pascals. Using Bernoulli's equation to get that pressure difference, you’ll need the air on top to be moving around 18 meters per second. That’s pretty fast, about 40 mph! (for reference, a cough is around 50 mph/80 kph, and a sneeze around 100 mph/160 kph). No wonder you really need to puff quickly and with as much force as you can muster.
But here’s the thing: the puzzle works even if the rocket piece is upside down (conical side inside the cylinder), and it works if you blow directly down, instead of just across, so the Bernoulli effect can’t be the only force in play here.
That’s the second piece of the puzzle – no pun intended. And it’s due to the gap between the rocket and the sides of the block. There’s not much space there, as you can see, which means there’s only a small volume of air. If you remember the ideal gas law, PV=nRT, pressure is an important part of how gasses act; especially since in this case the volume (V) and temperature (T) are essentially remaining the same (R is the ideal gas constant, which also isn’t changing). Once you blow into the Raketti, you’re increasing the pressure of the air in that little gap. The pressure around the rocket – and more importantly, of some of the air that’s on the bottom, which isn’t an airtight seal – will increase above the normal atmospheric 101 kPa, and the rocket lifts off!
Which of these two is the primary force? As we said, it’s still a matter of intense, if friendly, debate, and if you’ve got additional ideas, we’d love to hear them!
Okay, so what about that little irony in the name? Well, “Raketti,” as mentioned, is the Finnish word for rocket. Except that Finland has never, to our knowledge, actually built its own rockets for either civilian or military use. The rocket you see laser-etched into the front of your puzzle is the Titan-Centaur, an iconic NASA rocket that lifted some of the most important planetary probes into space, including the Voyager and Viking missions – you may also remember it as the handle of your Curiosity Box Golden Record Pizza Cutter.
Now go out and huff, and puff, and BLOW that Raketti into the air!