Proof That Nasa Is Possible.

[exchemist]

No, scientists did not make that claim.  The most famous example of that claim came from the editor of the New York Times:

 

"That Professor Goddard with his 'chair' in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to something better than a vacuum against which to react—to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high schools."

 

People then repeated that over and over.

Aha. Now that I can readily believe. :) 

[Maine farmer]

Sadly, there are such people.

I blame it on high school not teaching physics correctly.

They don't really go into the details of how balloon or rocket thrust occurs, they just take it as a given.

Actually, I remember learning Newton's laws of motion in grade 6.  Specifically applicable here is that "every action has an equal and opposite reaction.:"  Then the lesson was repeated with many examples in high school. Did they stop teaching that since then?

Edited April 24, 2017 by Farming guy

[quickquestion]

Actually, I remember learning Newton's laws of motion in grade 6.  Specifically applicable here is that "every action has an equal and opposite reaction.:"  Then the lesson was repeated with many examples in high school. Did they stop teaching that since then?

They say that, but they do not go into the fine detail of how rocket thrust works.

 

It's like how kid's books give kids an innaccurate idea of sound. They say a musical instrument has a very specific frequency. So kids are shocked when they learn about timber and how instruments do not produce single sine waves, but are a broad spectrum of different frequencies...which is a direct contradiction of what they were taught in schools.

 

The reason my example provides thrust, is because the random motion of the molecules on average hits the sidewall and does not hit the exit hole. This pushes the body forward. It is a particle statistics on average causing the motion. With millions of particles you are guaranteed the forward motion, air is not needed to push against.

[Maine farmer]

They say that, but they do not go into the fine detail of how rocket thrust works.

 

It's like how kid's books give kids an innaccurate idea of sound. They say a musical instrument has a very specific frequency. So kids are shocked when they learn about timber and how instruments do not produce single sine waves, but are a broad spectrum of different frequencies...which is a direct contradiction of what they were taught in schools.

 

The reason my example provides thrust, is because the random motion of the molecules on average hits the sidewall and does not hit the exit hole. This pushes the body forward. It is a particle statistics on average causing the motion. With millions of particles you are guaranteed the forward motion, air is not needed to push against.

Your example need not be that complicated.  I recall one teacher using the example of an astronaut throwing a ball, some jokes were made by students of using bodily fluids under pressure to provide thrust, and we had a lab with masses riding on pressurized air to reduce friction, and we bounced the masses off each other.  It was a lot of fun.

[Super Polymath]

Actually, I remember learning Newton's laws of motion in grade 6.  Specifically applicable here is that "every action has an equal and opposite reaction.:"  Then the lesson was repeated with many examples in high school. Did they stop teaching that since then?

The only things I can remember from the 6th grade was how much I hated everyone in middle school. Also remember copying my papers off the internet and getting caught. 

 

Yet by then I could tell you about fusion, fission, anti-matter, supernovae, zoology, number theory, the space age, etc. In part because my mom worked in computers and I lived a secret life using the internet as my library, was into scy fy, and learned most everything I knew about astrophysics from Carl Sagan watching re-runs of Cosmos.

 

Grade School is unnecessary. If you want people who are actually smart you have to pick people who can't learn anything unless they're genuinely interested in it. 

Edited April 24, 2017 by Super Polymath

[exchemist]

They say that, but they do not go into the fine detail of how rocket thrust works.

 

It's like how kid's books give kids an innaccurate idea of sound. They say a musical instrument has a very specific frequency. So kids are shocked when they learn about timber and how instruments do not produce single sine waves, but are a broad spectrum of different frequencies...which is a direct contradiction of what they were taught in schools.

 

The reason my example provides thrust, is because the random motion of the molecules on average hits the sidewall and does not hit the exit hole. This pushes the body forward. It is a particle statistics on average causing the motion. With millions of particles you are guaranteed the forward motion, air is not needed to push against.

I rather agree with Farming Guy. Bringing in the kinetic theory of gases, while perfectly accurate, is not strictly necessary. You can simply think of the combustion chamber as containing high pressure gas, with a segment of the wall missing at the exhaust side, so that there is a net force opposite to it.

 

Or you can think purely in terms of change of momentum and impulse, as Farming Guy does. This is actually more elegant and instructive, I think, as it lends itself to quantitative calculation of the thrust from a given rate of expulsion of mass at a given speed, etc.  

Edited April 25, 2017 by exchemist

[spartan45]

No, scientists did not make that claim.  The most famous example of that claim came from the editor of the New York Times:

 

"That Professor Goddard with his 'chair' in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to something better than a vacuum against which to react—to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high schools."

 

People then repeated that over and over.

Here’s regarding reference to popular misconception Newton’s Third law in the early 1900’s. Few scientific reference works would admit their fellow scientists got it wrong; much easier to blame some newspaper editor. However, let’s assume the editor of the NY times started this popular belief. Where were all the eminent scientists of the day lining up to correct this layman’s error?  In 1909 the American Dr Robert H. Goddard was starting an extensive theoretical investigation of rocket dynamics leading to an experiment circa 1912-1914 which would dispose of popular misconceptions of Newton’s Third law. It was widely believed (all the fault of the editor of the NY Times!?) that rocket thrust would be sucked out into the near perfect vacuum of space so would not give any propulsion. Goddard fired and measured the thrust of a solid-fuel rocket which he had placed inside an evacuated glass tank proving rockets would give thrust in a vacuum. In fact it was found rocket thrust works more efficiently in a vacuum because air actually has a damping effect, slowing the exhaust gases. Although there are a few text book references, the bottom of the first page under ‘Rocketry’ of this reference from the internet seems good.  http://n4trb.com/Publications/The%20Rocket%20Experiments%20of%20Robert%20H%20Goddard%201911%20to%201930.pdf    

[billvon]

Here’s regarding reference to popular misconception Newton’s Third law in the early 1900’s. Few scientific reference works would admit their fellow scientists got it wrong; much easier to blame some newspaper editor. However, let’s assume the editor of the NY times started this popular belief. Where were all the eminent scientists of the day lining up to correct this layman’s error?

In the Letters to the Editor section of later papers.

 In 1909 the American Dr Robert H. Goddard was starting an extensive theoretical investigation of rocket dynamics leading to an experiment circa 1912-1914 which would dispose of popular misconceptions of Newton’s Third law. It was widely believed (all the fault of the editor of the NY Times!?) that rocket thrust would be sucked out into the near perfect vacuum of space so would not give any propulsion.

 

 

Was the entire misconception the editor's fault?  No.  Was it his fault that he published misinformation without verifying it?  Yes.