Why can’t the space shuttle just go slow enough to not be heated up by friction with earths atmosphere on re-entry?
In: 5
So basically, there is a couple things going on here.
First, the space shuttle (or any space craft) doesn’t carry enough fuel to do this. By the time they get into orbit all they have is enough fuel to maneuver a bit and then to start back descending when the time comes. Because they have to go so fast to stay in orbit, there is no way for them to slow down. They’ve used all their fuel to get there.
Second, as they break orbit and come in to earth, gravity pulls them faster and faster. Think of like a hotwheels car on a track. The track goes up, then back down on the other side. You send your car and it goes up the track, and by the time it reaches the top it’s going pretty slow, but then it goes down the other side and keeps speeding up until it reaches the bottom. Same thing for spacecraft. They accelerate a lot on the way back to earth, and as I stated in the first reason, they don’t carry enough fuel to slow down.
It’s essentially in a directed free fall, it can’t like ‘brake’ there’s no ‘reverse’ on the thrusters and stuff.
It’s in space before re-entry so there’s nothing slowing it down, it can only really start to slow down as it enters the atmosphere.
In order to orbit Earth it’s gotta be going close to Mach 25, and there’s just no way to slow that down enough in open space before you’d fall into the atmosphere anyway, so it tries to slow down a lot in the upper atmosphere as it can, but its ability to slow down is proportional to the density of the air, and it’s ability to steer in very thin air is much less.
So it just tries to take a really thin angle and ease in as much as possible.
The earth is spinning at like 1100 mph and traveling around the sun at like 66kmps. Our atmosphere isnt stationary it moves along with the planet. However if you were to go in a geosynchronous orbit and slowly descend gravity would catch up to you and either you would enter into a spin that goes faster and faster until your craft is ripped apart or you would be caught in a nose dive going soo steep that you would not be able to pull out of it without slamming nosefirst into the ground or have the wings ripped off off trying to pull out of a 90 degree approach
The earth is rotating at 1000 miles an hr.
If it slowed down when entering the atmosphere, it would just get destroyed or bounce back into space.
Also when it enters the atmosphere its relying on friction and gravity to slow down. They typically wont have any fuel or even any “brakes” on the space shuttle. So the speed is all just from “coasting”.
The atmosphere is like a whirlpool. If you dont go fast enough to break the current, you just burn up.
[removed]
We WANT it to burn up. That conversion of kinetic energy to heat and the disintegration of ablative material is how we slow it down on the cheap.
Because friction is a completely free way to slow a spacecraft down. In space, the only way to slow down is to burn fuel in the opposite direction you’re moving. Using the air to slow down instead means you don’t need to bring as much fuel, which means you can bring a heavier payload.
Increasing the payload size by making the rocket more efficient is a goal for any rocket scientist.
No-one mentioned it, so I will. The space shuttle is *not*, I repeat, *not* heated up to any significant degree by friction. This is a widely held misconception.
The heating is from the *compression* of the air in front of it.
First off, why?
Secondly, how would they slow down?
Thirdly, it has to go super fast to stay in orbit. You can’t just hover above a planet or the gravity will pull you in. You have to stay moving fast enough to keep “circling the drain without falling in.” When it’s finally time to de-orbit there’s literally no way to slow down before you hit the atmosphere. There’s nothing to grab onto, no drag because theres no air up there, and trying to use some kind of rocket would add too much extra hardware, fuel and weight to be practical. All you need to do is point yourself at the atmosphere at the correct angle and then gracefully plow into it to dissipate the right amount of momentum so that you drop from orbital speed to landing speed. They’re literally using the whole craft as an air brake, which is the simplest and best way to slow down in air.
Technically ANY friction with the air will generate heat energy. If you stick your arm out of a moving car there is heat energy being generated by the air friction, but it’s so tiny it gets carried away by the air itself. Space craft are much bigger, heavier and faster, so they end up trading their momentum for a bunch of heat energy that temporarily builds up (which they are designed to do) until they slow down enough that the air carries the heat away faster than the friction generates it.
If it never speeds up to those extreme speeds, it will fall right back down once it gets to space.
If you want to use your engines to slow you down instead of dumping that energy into the atmosphere, you have to build a rocket about 20 times bigger than the one you have to carry the rocket you have into orbit with the fuel tanks still full.
Latest Answers