New Space Terminology: Simple explanations of complex things

New Space: How does it all work? Simple explanations of complex things

When we write about new space companies and all the people and technologies involved, it can get a bit confusing – trust us, because we get confused frequently when we research and write… There are so many different abbreviations and concepts that are part of each and every article. that we thought it makes sense to write them down and explain them in simple terms. So without further ado, here are some abbreviations, concepts and things that are helpful to understand “new space”:

Actually sending stuff up to space: Rockets, payloads, propellants etc.

Rockets and stages:

  • Most rockets have “stages”, meaning first stage, second stage or even third stage. Those are basically individual rockets that are put together to launch the rocket. Once a rocket ascends and has reached a certain height, the stages are dropped one-by-one to make the rocket lighter. A lighter rocket makes it easier to continue, cause you need to fight gravity a little less (just like a 50 kilo deadlift is easier than a 100 kilo deadlift – gravity can be a bitch). These “stages” are kind of required for overall better performance of rockets (though single-stage rockets exist, abbreviated “SSTO”).

Rockets and propellant: Chemical rockets or nuclear rockets?

  • First of all, all rockets we use to get to space from Earth are chemical rockets, meaning they use chemical reactions to produce thrust, the force that makes things move (thanks for pointing that out, Newton!). There are also nuclear rockets or rockets using ion engines, but they can’t bring us up to space because our gravity is too strong. So, chemical rockets need a propellant (things that can react to produce force), and the propellant is generally always a fuel and an oxidizer. You might ask: why two? After all, cars only have gas, airplanes only use kerosene. Well, that’s correct, but they technically also use two, but the oxidizer (like oxygen) is already in the air. Remember, rockets go very high, and the higher you go, the less O2 (an oxidizer) is there (at some point: 0%), so rockets have to bring their own! That’s why there are all these different combinations of propellant, which of course are always abbreviated and sound confusing, like “LOX” and “RP1” or “LOX” and liquid methane, or N2O4 and Hydrazine.
    • LOX = Liquid Oxygen, generally supercooled and at very low temperature because oxygen becomes liquid only at cryogenic temperatures of -219° C
    • RP1 = Rocket Propellant 1 (I mean, that’s not that difficult right?) which is a refined kerosene
    • Liquid methane = Methane (CH4) is a main component of natural gas, and refined liquid methane has good properties as a rocket fuel. It can also be produced in places like Mars through ISRU (”In-Situ-Resource-Utilization”), which is why SpaceX’s Starship engines (”Raptor”) will use methane
    • Hydrazine = Nasty stuff, chemically N2H4, and also a “hypergollic” propellant, which means they “spontaneously ignite” when they come in contact with certain other components. That’s nice cause you don’t need a complex mechanism to ignite it, but it’s pretty bad when it happens, well, “spontaneously”…

Rockets and propellant: Solid, liquid or hybrid

  • There are basically three types of states of the propellant that you can use:
    • Liquid fuel rockets (we call them “engines“) are the main choice for space-bound rockets and almost everyone uses it (SpaceX for Falcon and Starship, Europe for the Ariane, Russia for the Soyuz, China for the Long March). This is because liquid fuel rockets have properties you want for launch rockets, such as high “specific impulse” (how efficient is the engine with its propellants, because you need to measure “thrust” in relation to the weight of the propellants themselves – a higher Isp is always better), the ability to turn them off and on again (for aerodynamical pressure, for dropping the different stages, correcting trajectories) and making sure they’re reusable. The downside of liquid fuel rockets is that they’re quite dangerous and they like to spontaneously combust (think huge explosions) and engines tend to be rather complex and fickle – though once they work, they work (hello, Spacex). That makes liquid fuel rockets the “star of the rocket family”: Good fundamentals, high potential, but needs constant training and always has to be treated exactly how they want to be treated – or they’ll explode and take you down with them.
    • Solid fuel rockets (they have “motors“ instead of engines) are mostly used for missiles used by the military, such as air-to-air missiles, short-to-mid range missiles and even ICBMs (Intercontinental Ballistic Missiles like nuclear rockets), though a few use liquid fuels. Solid fuel has low efficiency and lower specific impulse, but they still give good thrust and they’re pretty safe to handle. However, once you light a solid fuel rocket, it’s hard to turn them off. And also forget about full reusability, because they cannot land themselves once they’re spent, so you’d need parachutes or something, which is not that efficient (and things break), and the combustion chambers are usually spent and pretty dirty or almost impossible to clean up and reuse. That makes solid fuel rockets sort of the “reliable and likeable but also kind of a simpleton” of the rocket family.
    • Hybrid fuel rockets (they also have “motors“) have so far been primarily used for research, teaching and experimenting. They combine some of the advantages from solid and liquid rockets by using solid fuel and liquid oxidizers. You can therefore turn them off (and on) again with the right equipment, you can still get a pretty good specific impulse and they’re much safer to handle than liquid rockets. Unfortunately, hybrids still have several disadvantages: they require a fairly complex motor, expensive structures to handle temperatures (such as carbon composites which are very expensive), your Isp is never going to be as good as that of a liquid fuel rocket – forget sending heavy stuff up to space – and full reusability is considered to be pretty difficult (see solid fuel rockets). Basically, a hybrid fuel rocket is the “nerd of the family” who equates “scientifically complex” with “good”, who has worked very hard all their life, but who just doesn’t have that natural genius that his sibling liquid-fuel-rocket was born with, and who isn’t as likeable and understandable as his other sibling solid-fuel-rocket.