Since the beginning of the space age, engineers have banged their heads over and over again against the same problem: the technical impossibility of building an engine that would be both efficient in the atmosphere and in a vacuum.
So much so, that we only managed to fix it by mounting two-stage rockets: one with nozzles for the atmospheric phase and another optimized for outer space. The “middle” thing is a matter of brute force.
Is it inefficient? Yes Do we have another option? Not at the beginning.
“In principle”? Well yes, because for more than 70 years there has been no shortage of experts who thought that the solution lay in something very simple: form. As Darren Orf pointed out a few months ago, “whether it’s the German V-2 rocket, NASA’s legendary Saturn V or SpaceX’s Falcon Heavy, all rocket engines share a common attribute: their exhaust nozzles are bell-shaped. “. But what if they didn’t have it?
Essentially, the function of a nozzle is to direct the flow of gases in the direction that interests us. It seems obvious, but it’s key. Above all, because the mixture of propellants at very high temperatures generates a lot of force, but the movement of the gases is (to a large extent) random. The conventional nozzle has proven very effective in converting all that randomness into a “jet” efficient enough to put the rocket into the air. The question is, then, how do we do without it.
That’s where the ‘aerospike’ comes in: a type of engine that “would maintain its aerodynamic efficiency over a wide range of altitudes” by changing precisely the shape in question. That is, the gases are launched “along the outer face of a wedge-shaped solid volume” (the spike) and the result would also efficiently reduce this randomness.
It sounds good, very good. At the end of the day, all of this that we have explained would translate into being able to reduce the total weight of the ship and, in the process, increase the useful load. The problem? That doesn’t work.
The eternal promise of space exploration. It is true that NASA tested a prototype in the 1990s, but the result has always been the same: the different companies or agencies that have opted for the aerospike have ended up signing checks that they have not been able to pay.
And what has changed that we are talking about this? Germany has passed. In April, Berlin awarded a military contract to Polaris, a start-up dedicated to this type of technology, to investigate the possibilities of using such an engine in a space plane. The news now is that Polaris has just completed the first series of test flights of one of the key prototypes.
We are talking about 15 tests between the end of August and the beginning of September. And it is true that the MIRA-light (which is what the prototype is called) measures only two and a half meters long and is very far from what we are looking for; but the sensations are good and that has caught the attention of many people.
Does that mean we will (finally!) have an aerospike engine? At this point in the game, the most reasonable thing is to think that no, that there is a lot of work ahead and that, even in the best of all possible worlds, its effects are not going to be immediate. However, innovation in the world of engines is excellent news (and even more so if the tests go well)
