Propulsion Efficiency - Sixty Symbols

[MrJepcats]

I tried to do this when I was little. I couldn't get a good seal though so it didn't work *sigh*

[UmlautBanana]

I'm building a bottle rocket for physics class... this video helped a lot.

[HWGuyEG]

I want to make a huge multistage water rocket...

[damianpaz]

5:34 "WATTA .. COCKF WRIM PWAHAHAHA! " XD

Lovely video!

[danthemanzizzle]

Isn't the efficiency of rocket engines directly related to how fast the propellant leaves the nozzle? ex, the shuttles exhaust at something like 2000mph thus making it much less efficient than an ion drive that can eject ions at something along the lines of 40 miles per second. and wouldn't the most efficient rocket possible have an exhaust velocity of c?

[disorganizedorg]

@danthemanzizzle I was going to ask the likely related question "what's the relationship between eta and specific impulse?"

[ytmoog]

@danthemanzizzle

Depends if you are talking about fuel efficiency or energy efficiency.

The rocket with a high exhaust velocity would be more fuel efficient but much less energy efficient, and would need far more energy to accelerate the rocket to the same velocity.

Which is why ion drives used in space missions need nuclear or solar power to supply enough power.

Google the Tsiolkovsky rocket equation which allows these to be calculated.

[godlyking3]

@danthemanzizzle getting any mass to c is impossible when it has restmass, explained with the equation: mrel=(mrest)/(sqrt1-(v^2/c^2))­. DIVIDING BY ZERO?!

[danthemanzizzle]

@godlyking3 sigh, ok, (c /1.01)

[mpdp85]

i remember doing this exact same thing at high school... had to find the optimal ammount of water to get maximum height, and we calculated the height using basic kinematic equations and assuming a symmetrical trajectory and timing how long it was in the air.. good days.

[handiest1]

Well, the camera did see that he could use some weed N' feed on the lawn!

[Jacnas]

Wait a minute. The propulsion is not more efficient. It's just that water is a much denser propellant and so it gives rocket a much better mass ratio. The air, being lighter, is more efficient, i.e. it gives more delta v per unit weight but because it has such low density, there's not much of it in the rocket. So the difference in mass ratio between water and air filled rocket more than makes up for the difference in exhaust velocity.

[AntiProtonBoy]

Nearly dropped the F-bomb there. :P

[soapy05]

Completely random and off topic, but I love how the sun registered as pure black in the rocket cam at 5:47

[danthemanzizzle]

@soapy05 black hole sun.

[calv1nchang]

Wanna try it again?

.......Yea.

[HiAdrian]

1:45 Great explanation of modern jet engines. I always admired them for their aesthetic complexity, but never exactly understood the necessity for them being that way.

There's a special kind of satisfaction one gets when grasping the clever/elegant mechanics of a machine. I have a great respect for the ingenuity of people who come up with these designs, from basic plumbing to rocket science.

[pawningcity]

@sixtysymbols how did u make the launch pad for the rocket? thanks

[vashthefunker]

I wish I could get my hands on a jet engine - could learn a lot

[LiiMuRi]

Nice day at work. :)

[lejink]

love this channel...oh so much

[WHAtMakesMedrEam]

Thankyou for the lesson.

[benkettle]

but would the added thrust the mercury provides be enough to counter its higher density

[archaedemos]

Great Vid ... So Much of the math is counter-intuitive  we should really focus on this for the next Generation.

[blades392]

star trek?

[TheKturner05]

@archaedemos As a physics major I have to agree, if you flip through a modern physics textbook without a desire to do math you will have a hell of a time trying to convince yourself you can or want to learn physics.

I really think it start in high schools getting across the importance of math and sceince.

[arachnipope]

I built a water rocket in 1991 using 1.5 liter coke bottle and a modified air chuck for a release mechanism. It flew quite far on 180 psi !! Its hard to imagine, but the plastic withstood that pressure. Never too old for toys!!

[Repelsteel2004]

At slow speeds motors work efficient when they accelerate a big mass by a small amount. As the vehicle goes faster, efficiency goes up when a smaller mass is accelerated by a bigger amount.

In Ion propulsion engines, the spacecraft go very fast. Thus very small amounts are accelerated by very large values to make them go.

[hippopopotomus]

Don't ion propulsion engines accelerate very low mass particles to very high speeds? Are they inefficient or just... different

[THExSAUCE]

lol...good thing he was using water rather than experimenting with a burning fuel when he sprayed himself

[Arlemagne]

If you put mercury into the coke bottle, would it go higher still? Mercury being heavier than water, so I guess you would say the propulsion efficiency would be higher.

(Incidentally, would the viscosity of mercury vis-a-vis water have an effect on how it could be used as a propellant?)

[cookiecamp]

that was pretty cool

[RichardsxGirl]

Such a cute start to the video

"good grief"

XD

[TeamVacaville]

Vid started out pretty slow, but got much better towards the end. Nice!

[Envergure]

Wow, Rollsroyce makes jet engines? whodathunkit

For any Greeks out there, is the British way to pronounce Greek letters right, or the American way? (of course, we're probably both wrong)

[icovada]

I'm not Greek but I'm studying it. And both ways are wrong. The "e" is open

[pinkdave747]

You have probably seen a Rolls Royce engine in person before if you are an aviation enthusiast. The AV-8B Harrier is powered by the Rolls Royce "Pegasus" engine. I think that it was in it's day the most beautiful engine design both esthetically and from an engineering perspective. Also many commercial jets are powered by Rolls Royce powerplants.

Regarding the pronunciation of the Greek alphabet, ... the Canadians are obviously right!

XD

[ProfWithTheHair]

really good and you can see how close the School of Chemistry is to Physics!

[nolongerlong]

That's not Physics, it's the Coates Building, which is one of the School of Engineering's buildings. Physics is actually closer to Chemistry than Coates is though.

[itsabomberscope]

fantastic stuff, looks like good fun.