Why is it a rocket🚀 is used to go straight up into outer space and not just use an airplane ✈️ ? I’m sure there is a good reason but it seems that the gradual assent would be preferred over the straight up approach.
In: Engineering
>Why is it a rocket is used to go straight up into outer space and not just use an airplane ?
Going into orbit isn’t about going UP. It’s about going horizontally really fast. Rockets go up in order to get out of the thick, lower atmosphere into the thin, upper atmosphere where they can avoid drag and go horizontally faster.
Experimental planes are sometimes carried under the wings of bombers. They sometimes can reach the Karman Line designating the boundary between the atmosphere and space. There is a British company attempting to create a plane that can fly to orbit using air breathing engines and carrying a supply of oxygen and fuel to burn when the air gets too thin. They’re called SABRE engines.
wings and turbines depend on a certain atmospheric pressure to function, flight record is like 30km, obviously that being a purpose built aircraft, not a heavy lift.
there have been concepts to use an assist aircraft (or balloon) to get the shuttle up a bit before finishing with liquid fuel rocket propulsion.
Problem is… you might get up to what… 10 or 20km if your lucky, the space station is 340km up… so a long long way to go.
More importantly, you need to get it moving laterally too. The vast majority of launch thrust is to achieve this, not the vertical climb.
So your shaving only a fraction of the energy cost off the journey, but adding a TON of complexity (and limiting your payload based on what the plane can lift).
First, rockets only go straight up at the very beginning of their flight, in order to get out of the atmosphere. After a few minutes they’re going nearly horizontal.
There are two reasons why airplanes can’t go higher. The first is that most planes have a thrust to weight ratio under 1, so they rely on their wings to provide lift. In space, there’s not enough air to provide lift.
The second, and more important reason is that aircraft engines work by accelerating air. They take air in the front, burn it, and shove it faster out the back. If there’s no air coming in the front, they can’t burn their fuel and have nothing to shove out the back.
Rockets on the other hand start with a thrust to weight ratio typically a little over 1, which rises as it burns fuel, and the ship gets lighter(until staging anyway). Once you’re going sideways fast enough the earth curves away from you as you fall, decreasing the required thrust.
More importantly, rockets carry their oxidizer, so they don’t need to bring in air to burn their fuel, and they accelerate by shoving the combustion products out the back. The downside is that you have to carry all that reaction mass with you, you can’t pick it up as you fly like a plane can.
The hard part of getting to orbit isn’t going high enough, it’s going fast enough to not fall back down. The fastest air breathing planes go about 1200 m/s, while you need to go about 8000m/s sideways in order to not fall back down.
Planes are held aloft by the lift generated from air flowing over the wings. If you go high enough there isn’t enough air to create the necessary lift, and so you come down.
Airplanes require airflow to generate lift under the wings. After the air thins to a certain point, the plane can’t go any higher
Airplane engines need oxygen to burn their fuel, so they cant go into space. And the straight-up approach makes it easier to reach the speed needed to escape the earth’s atmosphere. (Feel free to fact-check these statements)
Atmosphere has thinner air as you go up.
Make a paper plane and throw it inside your home.
Now go outside and do the same. If it’s hot outside, the air would be thinner and it would travel slightly less. If it’s cold, it would travel a bit more.
So, planes require air to lift themselves up. Once you go up enough, you can’t go further as there’s no air to support.
Rockets on the other hand are like pogo sticks. They use own energy to go up. So, they can reach space.
TLDR: There’s no air in space
Jet engines and gas engines need air to burn/explode fuel so they can’t work in space. While Rocket engines carry a supply of their own oxidizer so they don’t need air.
Airplanes also need air flowing over the wings to generate lift. However this can be overcome by having a powerful enough engine to provide rocket like thrust and to maneuver once the wings stop working. It just isn’t currently practical to design an aircraft that way.
Airplanes also don’t have enough thrust to achieve escape velocity to attain orbit. However again this is more a case of practicality than a physical limitation on the airplanes themselves.
Airplanes, by definition, require air to work. They generate lift from the motion of air passing over their wings. Propellers and jet engines also need air to generate forward thrust, for more or less the same reason.
There is no air in space. An airplane could get you quite high, but it cannot take you into space any more than a submarine can travel above the surface of the ocean.
It’s not actually that hard to get to the edge of space. The space program uses rockets not so much for the going-up part, but because to get into orbit (or to leave the Earth entirely) you need to go sideways really really fast.
Rockets don’t go straight up, they go slightly diagonal at first and then when the air thins out they start going perpendicular to try and fall past the Earth aka get into orbit. The ISS and satellites are really just falling, but they are going so far sideways they keep missing the ground/Earth.
The air is what keeps airplanes aloft and air is needed for engines to work. At a certain point there becomes too little air for lift and to burn fuel.
Ignore where this image came from (a flat earth site), but this is the [flight path a rocket takes to get into space](http://fenewsnet.com/wp-content/uploads/2018/07/Flat-Earth-Rocket-Curve-Not_Hit_Dome.jpg)
They normally fly East because it is easier to follow Earth’s rotation and it gives them a speed boost to get to orbital speed.
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