If needed I will try to explain further.
The escape velocity for the Earth is 11.2 km/s. If you shoot a cannonball upward at that speed, it’ll have enough energy to completely leave Earth and never come back.
Would shooting it at that speed work? Wouldn’t it need to maintain that speed?
The Tyranny of the Rocket Equation
And, if your curiosity goes beyond that basic explanation, check out this NASA page on rocket launches:
If a spacecraft is launched from a site near Earth’s equator, it can take optimum advantage of the Earth’s substantial rotational speed. Sitting on the launch pad near the equator, it is already moving at a speed of over 1650 km per hour relative to Earth’s center. This can be applied to the speed required to orbit the Earth (approximately 28,000 km per hour).
Getting into orbit doesn’t just require overcoming the force of gravity pulling down. In order to stay up, you basically have to put yourself on a path that allows you to go around the Earth faster (or as fast as) you fall back towards it. When your movement around the Earth is balanced with the rate that you’re falling, you are in orbit. This means you have to go really fucking fast, not just up but sideways.
Kind of off topic. But people who came up with superheros and such who fly. You always see them going out at an angle and going in at an angle. Do you think they did this much studying or is it just coincidence?
I think it has more to do with representation of the character in visual media (comic books, television, movies). Showing the character from the side is better than showing just their feet. Also, flying sideways is visually distinct from simply jumping upward, which is important when you’re trying to show the action in the context of two or three comic frames.
Also, that’s how Superman took off, so that’s how a lot of superheroes designed after him took off.
I have a sense of what you’re saying. So other comments have already pointed out the escape velocity, and those are true. But I think I can expand upon this a bit.
So the weird thing about rocketry is that distances are insane. Like, whatever you think the distance is between 2 astronomical objects, the actual distance is probably at least 10 times that.
This, coupled with the fact that there’s no friction in space, leads to a very unusual way of traveling. In space, if you want to go somewhere, you point your rocket in the direction that you want to go, fire the rocket up to get up to the correct speed, then just drift the rest of the way to your destination. The fact that you can just drift to different locations means that you don’t actually need to keep using up fuel for the entire trip. You only need to use fuel once, at the beginning to get to the right speed.
In physics, this type of motion, where an object (a rocket in this case) drifts for most of the time, and suddenly changes direction in a relatively short span of time, is called impulse. So when we talk about rockets and how much “force” we need to get to places, what we’re really asking is how much impulse we need to get to the correct speed that’ll take us to where we want to go. Impulse is measured in what’s called delta-v, which is essentially a measure of “how much can we speed up.”
There’s actually delta-v maps for the solar system. So if you want to go to this location, you need to spend this amount of delta-v to get up to the correct speed that’ll take you there. It’s an approximate map - you’ll need to do per-mission simulations to get the exact delta-v values - but it’s a good enough estimate for general usage. To use it, you start at your current location, then trace a path to where you want to go. And you just add up all the numbers that you see along the way.
The escape velocity number is the delta-v required to leave Earth’s orbit (earth -> low earth orbit -> earth intercept)
If you want to go to the moon, you do the same thing. Earth -> low earth orbit -> moon intercept -> low moon orbit -> moon
You need to move at a speed of 4km/s.
Right idea, wrong number. Satellites in low Earth orbit are typically moving at about 7-8 km/s, depending on the exact altitude. The speed required to get from the surface to deep space (i.e., the “escape velocity”) is 11.2 km/s.
Another question. You always hear and see jets break the sound barrier but when they put their “boost” is there a point where they can’t break the speed barrier traveling upwards? Or can you only break sound barrier within the confines of the earth.
Speed of sound changes with altitude
