Escape Velocity and the Atmosphere

[D H]

The Earth has two main lines of defense against particularly nasty radiation. One is our thick atmosphere. Your spaceship will be above that, so there is some concern. Then again, people living at high altitude have the same problem, and they have that problem for all their life. The incidence of cancer is a bit higher for people who live at very high altitude compared to sea level, but in general they get along just fine. That's because these people are still protected by our planet's first line of defense: The Earth's magnetic field. If you want to read more, google "aurora (astronomy)" and "Van Allen Belts".

Unless your spaceship goes far from Earth, you will still be inside that first line of defense. Radiation and proper shielding against it is a concern for astronauts who go to the Moon or beyond. It is a much lesser concern for people in low Earth orbit. Since you are young, you may be able to be a space tourist sometime in the future and have a spectacular view of the Earth below you through large viewing windows. (The company for I work for is helping with one such project right now.)

 

[D H]

Why would you want windows in space? Just use camras.

Warner von Braun initially thought to make the Mercury capsule windowless. The initial astronauts let von Braun know in no uncertain terms that he had another think coming. Every US human-rated spacecraft has had windows.

Even if we could display a camera view in ultra widescreen 1080-p (or whatever improved video technology we have when space tourism beomes real), it will not have the UMPH factor that looking out a window yields. Anyone can see the video. Only someone who is actually in the vehicle will be able to look out the window. Since those tourists will pay a lot of money to get into space (current rate: a cool $20 million to got to the Space Station), they most certainly will want and will get a window. A very big window.

DH, when you talked about the accelerometer, would the car be experiancing horizontal forces & gravitational forces, or just horizontal/gravitational forces? Also, for example, when I am in a jet and I am go at an extreame AOA [175 degress] and accelerating, would the forces exerted on my body be gravitatonal?

The gravitational acceleration induced by the Earth on any object on or near the Earth is more-or-less the same in magnitude. It doesn't matter if the object is planted firmly on the surface of the Earth, flying through the atmosphere, or just above the atmosphere. That car, and jet fighter, and even a spacecraft in low Earth orbit are all subject to Earth gravity. The object's velocity or angle of attack doesn't come into play. All that matters is proximity to the Earth. The difference in the gravitational acceleration for the car and the spacecraft is a mere 5 percent or so.

Regarding the car: Many forces are involved for a car accelerating down a road. Listed as third law pairs, gravity pulls it toward the Earth and gravity pulls the Earth toward to car; the Earth's surface pushes up on the car while the cars whiles push down on the surface of the Earth, the cars wheels push backwards on the road while the road pushes forward on the wheels, air drag pushes ... You get the picture.

 

[ghost02]

Thank you very much for the explanation.

 

[FredGarvin]

Sorry, I didn't explain what I meant by G-forces. My definition of G-forces was wrong! I thought it meant the power of gravity in space. Sorry about the confusion I didn't think about it. So, to clarify, I would feel G-forces in space when accelerating as if I am in a Jet on Earth? [I am only 14 and just got a book on Physics so I am trying to learn about this stuff.]

Ugh. Sorry if my post seemed a bit harsh. I didn't know you were only 14. I hope you are on the right track now.

BTW, it would help if people would fill out their profile information so we can avoid things like this!

 

[mheslep]

could someone please explain why the shuttle needs such a great velocity to exit our atmoshere? my son would like to know why we could not use a balloon to slowly rise out,I told him that a balloon would pop because of lack of preasure and that got me thinking, if we ever figure out how to beat gravity, could we just float out and avoid the heat from friction?my son is still young and he is asking questions that I have a hard time answering

I still like Newton's original thought experiment for the best intuitive feel for escape velocity: fhttp://astro.unl.edu/naap/atmosphere/gravity.html" at greater and greater velocity until finally the shell makes it over the horizon before it 'falls'.