Space Terms 3: An Intermediate Guide to Jargon
Austin Morris, Director of Engineering
5 minute read
Dearly beloved, we are gathered here today to lay to rest any and all ignorance you may have ever had regarding jargon terms and acronyms used in the aerospace industry. Jokes aside, I intend for this installment to be a bit shorter than the previous, in the futile hope that it will make this one easier to digest. For those who read the entirety of the first two installments in the Space Terms series (found here and here), I salute you. For those who finished those columns, saw this column, and then had the audacity to open it up and give it a read, I thank you. Today we take another step on our journey of understanding the complex terms that define science and technology in the aerospace industry.
Radar
Radar is its own word nowadays, but it was originally an acronym for Radio Detection and Ranging. Fortunately, the name helps explain it, as Radar is the use of radio waves to detect objects and determine how far away they are at a given time by measuring how long it takes for the radio wave to reach the object, bounce back, and be detected when it returns to the source location. Radar is frequently used for tracking objects in space from the ground.
Lidar/Ladar
Lidar (sometimes referred to as Ladar) is similar to Radar in that it uses the same basic principles but uses a light or laser (hence Lidar or Ladar) in place of radio waves. It is still used for the purpose of detection and ranging, but has potential for different applications than those of Radar, such as use in autonomous vehicles, high-resolution mapping, and laser guidance.
Sonar (and why you won’t hear this one used in space)
Sonar is, yet again, a very similar concept to Radar. Sonar is sound navigation ranging and is a term that you won’t likely hear (pun intended) in conversations about space, as sound does not travel through the vacuum of space. As such, Sonar is typically used in applications underwater, as sound propagates very well through water. You may be wondering if I included this in the list solely for the purpose of making the above pun. If you were wondering that, you are absolutely correct.
Fuel
Fuel is a substance that has the capability to burn in the presence of an oxidizer, which is a source of oxygen. Most people are familiar with fuels, as we use them all the time down here on terra firma, in the form of gasoline, diesel fuel, natural gas, coal, wood, and many others.
Propellant
Many people, upon hearing the word propellant, liken it to the above-mentioned gasoline or diesel fuel. In fact, it is indeed similar, but not quite the same. Propellant is a chemical mixture that combines fuel and oxidizer, eliminating the need for external sources of oxygen. As there is not much oxygen available outside the atmosphere, knowing when you need to pack propellant instead of just fuel is an important distinction, like knowing when to also pack a can opener, instead of just a can of beans.
6DoF/6 Degrees of Freedom
In the first installment of the Space Terms series I described Attitude, which covers the three rotational axes of objects. If Attitude confused you, this should either make it much better or much worse. In 3-dimensional space (in which we all live), objects have 6 Degrees of Freedom: three rotational degrees (or axes) and three translational. For example, if you are standing on flat ground, you could: 1, walk forwards or backwards; 2, step left or right; or 3, jump up and down. Those are your translational motions. You could also: 4; turn to your left or your right; 5, lean forward or lean backward (careful not to fall); or 6, lean left or right (which is different from turning). These are your rotational motions. The translational axes are frequently denoted as X, Y, and Z, while rotational axes can usually be called out as Yaw, Pitch, and Roll. In orbit especially, all 6 Degrees need to be considered when making a movement.
Relative Velocity
I’ll try to explain this one without diving too deep into relativity (for now, but stay tuned). If you drive your car east at 60mph and pass a tree on the side of the road, it looks like it passed you pretty quickly. If there’s another car driving the opposite direction at the same speed as you, it passes you twice as quickly. That’s because you have a speed of 60mph relative to the ground, but 120mph relative to the car traveling in the opposite direction as you. Making sense so far? This gets a little trickier when you talk about objects that aren’t traveling in the same or opposite directions, and instead about satellites and debris which could be traveling in nearly any direction relative to each other, zipping by at 17,000mph. However, if you catch up to another object, traveling in the same direction, and have almost the same speed as each other, you may be traveling at 17,000mph relative to the surface of the Earth, but look like you are nearly standing still with each other. This is a low relative velocity, and this is what it looks like when spacecraft dock with the ISS, for example.
There you have it. You can now check off several more terms from the list of things that you maybe didn’t know. As we continue this journey, focusing more on terms pertaining to usage in space itself, I look forward to getting more into the details of how objects are distributed in the sky and how they move through their orbits. Likewise, I look forward to reaching the point at which I can begin sharing some of the niche terms that more often cross my mind and desk during the daily pursuit of KMI to develop a solution to the problem posed by space debris. Keep in touch with us, directly and through our social media, to follow our progress in that pursuit. I thank you again for reading and look forward to the next installment in the Space Terms series.
Recommended column to read next: Space Terms 2: LEO, MEO, GEO, and HEO