Aircraft engine shotgun start details

[Scout26]

No one would be into them if they had shitty, unrealistic graphics  

Ahem, from the mid 1970's to the early 1980's, I, and my buddies, put a lot of quarters into video arcade games that had some pretty shitty and unrealistic graphics...Tempest and Galaga...

[AmbulanceDriver]

https://youtu.be/5xO3lYa1bEc?t=44s

B-52 cartridge start.

ETA...  Make that *multiple* B-52 cartridge starts.

[230RN]

https://youtu.be/5xO3lYa1bEc?t=44s

B-52 cartridge start.

ETA...  Make that *multiple* B-52 cartridge starts.

Looks fake to me.














 

[AmbulanceDriver]

One of the things I thought was interesting was as the engines spooled up, you could see just how much air those engines suck in as the smoke was pulled in from quite a ways away.

[230RN]

I noticed that too.

A "typical" engine pulls in about 100 lb of air a second, according to NASA.

https://www.grc.nasa.gov/www/k-12/airplane/Animation/turbtyp/ettp.html

That's a cube of air of about 11 feet on a side.  Per second.

Terry

[RocketMan]

https://youtu.be/5xO3lYa1bEc?t=44s

B-52 cartridge start.

ETA...  Make that *multiple* B-52 cartridge starts.

That's got to be some of the best CGI I have ever seen!     

[230RN]

Re B-52 video:

That's got to be some of the best CGI I have ever seen!      

 

Jes' fer grins, I did some rough numbers as to how much "pull" on a jet engine the partial vacuum it's creating in front of it might be if the plane were standing still but spooled up.

Assuming a 6 foot diameter intake and a 1 psi pressure drop in front of it and neglecting everything else, there would be a pull of about 4000 lbs just due to the vacuum (partial pressure, technically) created by the compressor.

Assume a 6' diameter disc with 14.7 psi on one side and 13.7 psi on the other side.

6' = 72" diameter
(72/2)² X pi = 4072 square inches of engine inlet opening.

Times 1 psi of "suction" (pressure differential)  = 4072 lbs of "pull."

A pressure drop of only 1 psi seems kind of light, but it's scalable, that is, a 2 psi drop would yield an 8000 lb pull on the engine.

And neglecting everything else.

Jes' noodling it around.

Some folks do pushups before their coffee in the morning. :D

Terry, 230RN

[AmbulanceDriver]

Re B-52 video:

 

Jes' fer grins, I did some rough numbers as to how much "pull" on a jet engine the partial vacuum it's creating in front of it might be if the plane were standing still but spooled up.

Assuming a 6 foot diameter intake and a 1 psi pressure drop in front of it and neglecting everything else, there would be a pull of about 4000 lbs just due to the vacuum (partial pressure, technically) created by the compressor.

Assume a 6' diameter disc with 14.7 psi on one side and 13.7 psi on the other side.

6' = 72" diameter
(72/2)² X pi = 4072 square inches of engine inlet opening.

Times 1 psi of "suction" (pressure differential)  = 4072 lbs of "pull."

A pressure drop of only 1 psi seems kind of light, but it's scalable, that is, a 2 psi drop would yield an 8000 lb pull on the engine.

And neglecting everything else.

Jes' noodling it around.

Some folks do pushups before their coffee in the morning. :D

Terry, 230RN

Hrm.  Now you got me thinkin'.....  I wonder what fraction of a jet (or turbofan) engine's thrust is due to "blow" (air and exhaust gases being blown out the rear) and how much is due to "suck" (as Terry so nicely calculated for us). 

(insert obligatory Spaceballs reference here)

[230RN]

Yeah, I started to think about those high-bypass engines, and then how thrust is developed in the combustion chambers of the engine.  I personally think jet planes are actually just propeller planes, with the "propeller" being just a big-assed many-bladed ducted fan up front.    

Then I started to think about how afterburners and ramjet engines worked thrust-wise and I decided to just have breakfast and let it go.  

Rockets?  Hey, simple.  You've got a hole in one side of a pressurized chamber, and no hole in the other side.

Voila !  Thrust !

https://youtu.be/9-f5zfMH7QI

(CGIed, but effective.)

Just hacking at it, figuring a 1/2" hole with the valve busted off and 2400 psi in the tank, that's about 471.23889803846898576939650749193 lb of thrust for the first instant of the valve breaking off if my arithmetic is correct.

NAP TIME !

Terry, 230RN

[AmbulanceDriver]

which begs the question.  Does a prop push or pull?

[Andiron]

Ahem, from the mid 1970's to the early 1980's, I, and my buddies, put a lot of quarters into video arcade games that had some pretty shitty and unrealistic graphics...Tempest and Galaga...

Unfair comparison,  Galaga was awesome and cutting edge then.  Now it's just awesome.