The Rocket Equation: Mathematician vs Astronaut

You can go and watch Lucie Green's first two video with Chris Hadfield right now, the third one with 'aurora surfing' is out in a week.

Here is my previous video with Chris where we talk about Orbital Mechanics.

Our trip to NASA was organised by the fantastic folks over at Cosmic Shambles.

Free resources for teachers!
We have a complete guide to the mathematics in this video as well as some student worksheets and activities.

CORRECTIONS
- One fantastic correction from Dogan Erbahar which I will paste a copy of here:
"When equating the momenta you already put the minus sign in front of v_e. But then at the end you are again substituting on the equation. The resulting equation is correct but that minus sign is there not because of v_e. It is there because your dm is negative that your rocket is losing mass. So should be placed in derivation."
- Let me know if you spot any other mistakes!

Thanks to my Patreons whose generous funding I used for a vacation to Cocoa Beech Florida NO REFUNDS.

(Or maybe everyone involved donated their time, covered their own expenses and my Patreons only had to pay for that flip-chart. True story: I bought that flip-chart in the USA as it seemed silly to fly one over from the UK and afterwards the NASA outreach team kept it, which I think means it officially 'works at NASA'. That flip-chart now has a cooler job than me.)

Here is a random subset of those fine Patreon People:

Baadrix
Stephen Tierney
Erin Eldridge
Christian Gruber
David Wagner
Richard Fourie
Nicholas Koceja
Kristian Joensen
Andy B
Jordan Scales

Filming and editing by Trunkman Productions
Extra help during the shoot thanks to Melinda Burton and Joanna Gostling
Flipchart by Matt Parker
Audio by Peter Doggart
Music by Howard Carter
Design by Simon Wright and Adam Robinson

MATT PARKER: Stand-up Mathematician

[oslier]

Engineers: let’s add 30% for rounding error.

[alperenerol]

Me trying to sleep...
My brain at 3am: inaudible maths noise while Chris talks about rocketry

[yeeterdeleeter]

"8000/3500 ... that's about 2" "and e is 2.7 ish"
As a physics student, the amount of rounding going on in this video was just perfect

[jackeea_]

Finally, I've seen a "e is more or less 3" in the wild!

[neonblack]

I like how "Oiled Cement" is the best analogy he could come up with for near frictionless space flight

[DonutFlameFPS]

"Let's say 8..."
"8 is an easy number"
"...thousand"

[andrewbergspage]

"and you're just a bit of metal and flesh…"
Chris Hadfield, bionic man

"That's actually what astronauts fly on.
- Maths."

Should be a t-shirt.

[EmanuelsWorkbench]

Chris is one of the nicest guys. So approachable and friendly. I pleasure to work with when I did work with him a decade or more ago!

[tparadox]

I had a late night and an early morning and I was watching this on the bed after work so I dozed off for a moment and then I opened my eyes and saw Chris looking directly at the camera saying "you're lying on your back." and I had a bit of a panic moment.

[BeardyBaldyBob]

For anyone who is interested... given it cost approx $54, 500 per kilo for the space shuttle (once you add in the R&D, vehicle & program costs etc.), that's $54.50 per gram.
The mass of a righteous moustache like that sported by Chris is approx a third of a gram, thus, it cost NASA about $18.17 to fire that bristly lip warmer into the void each trip 👍

[kennethbatstone]

I'm deaf in one ear. I had to watch this twice and wear my headphones the wrong way round. It was worth it.

[daniele_]

Sad fact: that 10-15% of "payload" is actually about 90% structural components of the stages. Only about 1-2% of the total initial mass is the real final payload.

[georgplaz]

3:25
I love how Chris takes the battle by pushing the camera too far from the whiteboard, making it impossible to read 😂

[ranseus]

"When your 'F' is steady and your 'M' is going down, your 'A' is going up." -- Chris Hadfield tells an astronaut dad joke.

[DoganErbahar]

Ok one technical detail. When equating the momenta you already put the minus sign in front of v_e. But then at the end you are again substituting on the equation. The resulting equation is correct but That minus sign is there not because of v_e. It is there because your dm is negative that your rocket is losing mass. So should be placed in derivation. That's how books derive it. (Confuses me also everytime I try to derive in class...) very good video, thank you anyway...

[umchoyka]

"Your F is steady and your m is going down... your a is going up"

It really is

[Ennar]

Matt: "I am an SI unit kind of individual."
Chris: "Yes, you are."

[aiboffin]

And here I was thinking I’d never understand poetry, thank you Chris.

[Simio_Da_Tundra]

Nobody:
Matt Parker: e^-(8/3.5)≈e^-2≈1/9
I wonder why they say he does math like a physicist