Sciency Words: Delta-v

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:

DELTA-V

Okay, it might be a bit foolhardy of me to try to tackle this term. This is actual rocket science, and I’m nowhere close to being an actual rocket scientist. But this is still far too important of a concept for me to ignore, so I’ll do my best.

The simplest definition of delta-v (often represented mathematically as ∆v) is that it equals your total change in velocity. So if you’re driving along at 25 miles per hour and then accelerate to 65 mph, your delta-v equals 40 mph. And if you decelerate from 65 to 25 mph, your delta-v once again equals 40 mph.

Things start getting interesting when you consider delta-v to be cumulative. So if you start off at 25 mph, accelerate to 65 and then drop back down to 25, your total delta-v equals 80 mph (40 mph + 40 mph).

In rocket ship design, the term delta-v is used as a sort of proxy for how much thrust your engines are capable of and how much fuel you’re carrying. You might also consider the kinds of gravity assists or aerobraking maneuvers you can use to augment your delta-v without expending additional fuel.

This is where the math starts to get complicated, but if you can calculate how much delta-v your spacecraft is capable of, then you’ll know where you can go in space. And if you know where you want to go in space, you can figure out how much delta-v it’ll take to get there and build your spaceship accordingly.

I first learned about delta-v from a video game called Kerbal Space Program. It’s a fun and sometimes frustrating spaceflight simulator that does a reasonably good job approximating how real life space exploration works. Unfortunately I was never very good at it. The scenario in the comic strip above… I made that mistake a lot.

But hopefully I’ve learned my lesson well. I’d hate to run short of fuel during my upcoming totally-for-real, I’m-not-making-this-up trip to Mars (stay tuned!).

Links

The Tyranny of the Rocket Equation from NASA.

Can Kerbal Space Program Really Teach Rocket Science? from Scott Manley (well known for his YouTube tutorials on K.S.P.)

How to Use Kerbal Space Program to Teach Rocket Science from Digital Media Academy.

Six Words You Never Say at NASA from xkcd.