Edit: I didn’t understand how a jet engine worked, but now that I do, the question has been amended to this…
“Why does a rocket have to travel faster and faster the higher up it goes? Shouldn’t it require less and less speed as it is further from the earth it gets because there is a non-zero number(very small) of negative gravity change the higher you are?”
Edit #2: I think I suck at asking this so I’ll ask it like a 5 year old.
We have all seen videos of rockets taking off. They start very slowly, and then build in speed. Although, at first, they build up in speed. It’s not as if they torque off the earth at 20,000mph, although that would be ASTOUNDING to see. So here’s my super drawn out really dumb question that I cannot wrap my head around the answer for the life of me.
Let’s say you have a rocket going 100mph going 90 degrees straight up from the surface of the earth. Why can’t it just keep going 100mph straight up. Just keep going and going. Up, straight up. Up up up and away? Why can it move up starting from zero miles an hour? If it can move up at 5mph even for an instant, why can’t it continue at that velocity all the way up.
All the answers have been wonderful if I was asking how to get something in orbit. I’m asking why 100mph 90 degrees going straight up works down here, but not up there? I cannot find a straight answer to this question no matter what I google. I appear to be bad at research or this is just a stupid ass question. I really just don’t understand the physics of this at all.
Let’s try this another way. Say I threw a magic baseball that whatever velocity it was tossed at, it maintained until it hit a object. It doesn’t disregard gravity. It just has a magic anaerobic motor that maintains the speed. Like cruise control. Say I throw it 90 degrees straight up at 35mph. Will it leave Earth? Why or why not?
In: Engineering
> We have all seen videos of rockets taking off. They start very slowly, and then build in speed. Although, at first, they build up in speed. It’s not as if they torque off the earth at 20,000mph, although that would be ASTOUNDING to see. So here’s my super drawn out really dumb question that I cannot wrap my head around the answer for the life of me.
I feel as if nobody had answered this yet. There are two reasons. One has been hinted at by Kerbal Space Program players already, and that is that going too fast in the lower atmosphere is really bad for your fuel mileage. If you ever held your hand out of a moving car, you have felt the wind pushing it towards the rear. That same wind is on the rocket, and while they try to build them very pointy to play nice with the air, they still feel the resistance of air. There is less air the higher you get, so you can go fast unimpeded once that air is out of the way.
But there is a second reason. They only go fast high up because they only *can* go fast after having gone slow for a while. For one, every engine from a car to a rocket can only do so much acceleration, that is to say that building up speed takes time. This is why car testers always give you the 0-60: How much time does the car need to get up to highway speeds.
The thing with 0-60 is that the heavier your car is, the longer it takes to get up to speed. Now for a car, most of that weight is the body, the engine, the cargo, the passengers and such. Not so much for a rocket. For the rocket, almost all the weight is in the fuel tank. So, when the rocket is almost out of fuel, it is very much faster than it would be with a full tank. Which is also why they carry so many engines that are just thrown away on the way up – from a Saturn V’s stages to the Space Shuttle boosters. Once you are high up, you have spent a lot of fuel, the rocket has become much lighter, you do not need such big engines anymore. And you are still gradually going faster and faster because up there, there is not much that slows you down, and you can keep accelerating.
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