How Do NASA and other organisations make sure they are at the right spot to pick them up and that the astronauts don’t land in some war zone or remote hard to reach area?
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Answer: The earth is 70% water. NASA sends most it rockets from Florida because most of the debris will land in the Atlantic Ocean when leaving orbit. And on the way back they land in the pacific because it’s the largest ocean. They literally just aim for (as Neil degrasse Tyson puts it) “the big toilet bowl of the world.”
Well they know the speed on the planets and the space ship on each axis and they do a sorta complicated arithmetic using mechanical physics and the trajectory of projectiles to calculate when each body will be at a point where they can come in contact. Basically a lot of math and science brought about by their knowledge of the relativity of the planets and speed of everything so just taking the distance and the speed and finding the time and place.
Orbital trajectories and the effects of air resistance are well known and very predictable.
Assuming that you are not in a spacecraft with wings, there is a predetermined point where you fire thrusters in the opposite direction to your motion to slow you down somewhat. That means your orbit starts to decay and intersects with the top of the atmosphere sometime after. That slows you down even more, generating a lot of heat as you compress the air ahead of you. As the atmosphere becomes thicker lower down you lo*o*se your remaining forward velocity and descend the last bit vertically under a parachute.
All those effects are known and can be factored into the calculation as to when, how long and how hard to do the initial reverse thrust burn to get fairly close to your desired landing spot.
If you ignore the atmosphere the calculation become very simple. When you slow down the spacecraft to deorbit the trajectory at the opposite side of the planet will be lowered so this is where you will land. Just make sure you are at the opposite side of the planet to where you want to land and you are good to deorbit. With atmosphere the landing spot is not at exactly the opposite side of the planet. But you will have this all calculated as the spacecraft is being designed and there will be tables for how far around the planet you will make it to deorbit. So you make sure to deorbit when your orbit will be over your landing site in the amount of degrees specified in the tables.
But the deorbit burn is not the last time you can normally steer the spacecraft. Capsules have their mass off center so the heat shield on the bottom will form an angled plane to the air in the atmosphere and therefore generate some lift. This allows the astronauts to roll left and right to control their descent and guide themselves towards the desired landing spot.
Even with all this they do not have to land extremely accurately. The recovery crew does have helicopters that can reach the landing site within minutes in most cases. Even if the astronauts had to do emergency landings they have managed to control it close enough to get recovered fairly soon.
There are however some Russian stories of uncommanded emergency landings where the astronauts did not have the luxury of picking a landing site. This was mostly during launch and not in orbit. These have demonstrated that recovery can take days and that the survival training and emergency camping equipment are necessary. Rumor has it that in one of these incidents they did have to cross a country boarder to conduct the recovery and did not ask for permission fearing that they would not be the first on scene, but this is unconfirmed and likely not true.
In general the emergency descent is only conducted when being in a remote wilderness, in the middle of the ocean, or in the middle of a war zone is preferable to being in space a few minutes longer in the current condition of the spaceship.
Orbital trajectories and the effects of air resistance are well known and very predictable.
Assuming that you are not in a spacecraft with wings, there is a predetermined point where you fire thrusters in the opposite direction to your motion to slow you down somewhat. That means your orbit starts to decay and intersects with the top of the atmosphere sometime after. That slows you down even more, generating a lot of heat as you compress the air ahead of you. As the atmosphere becomes thicker lower down you lo*o*se your remaining forward velocity and descend the last bit vertically under a parachute.
All those effects are known and can be factored into the calculation as to when, how long and how hard to do the initial reverse thrust burn to get fairly close to your desired landing spot.
Orbital trajectories and the effects of air resistance are well known and very predictable.
Assuming that you are not in a spacecraft with wings, there is a predetermined point where you fire thrusters in the opposite direction to your motion to slow you down somewhat. That means your orbit starts to decay and intersects with the top of the atmosphere sometime after. That slows you down even more, generating a lot of heat as you compress the air ahead of you. As the atmosphere becomes thicker lower down you lo*o*se your remaining forward velocity and descend the last bit vertically under a parachute.
All those effects are known and can be factored into the calculation as to when, how long and how hard to do the initial reverse thrust burn to get fairly close to your desired landing spot.
If you ignore the atmosphere the calculation become very simple. When you slow down the spacecraft to deorbit the trajectory at the opposite side of the planet will be lowered so this is where you will land. Just make sure you are at the opposite side of the planet to where you want to land and you are good to deorbit. With atmosphere the landing spot is not at exactly the opposite side of the planet. But you will have this all calculated as the spacecraft is being designed and there will be tables for how far around the planet you will make it to deorbit. So you make sure to deorbit when your orbit will be over your landing site in the amount of degrees specified in the tables.
But the deorbit burn is not the last time you can normally steer the spacecraft. Capsules have their mass off center so the heat shield on the bottom will form an angled plane to the air in the atmosphere and therefore generate some lift. This allows the astronauts to roll left and right to control their descent and guide themselves towards the desired landing spot.
Even with all this they do not have to land extremely accurately. The recovery crew does have helicopters that can reach the landing site within minutes in most cases. Even if the astronauts had to do emergency landings they have managed to control it close enough to get recovered fairly soon.
There are however some Russian stories of uncommanded emergency landings where the astronauts did not have the luxury of picking a landing site. This was mostly during launch and not in orbit. These have demonstrated that recovery can take days and that the survival training and emergency camping equipment are necessary. Rumor has it that in one of these incidents they did have to cross a country boarder to conduct the recovery and did not ask for permission fearing that they would not be the first on scene, but this is unconfirmed and likely not true.
In general the emergency descent is only conducted when being in a remote wilderness, in the middle of the ocean, or in the middle of a war zone is preferable to being in space a few minutes longer in the current condition of the spaceship.
If you ignore the atmosphere the calculation become very simple. When you slow down the spacecraft to deorbit the trajectory at the opposite side of the planet will be lowered so this is where you will land. Just make sure you are at the opposite side of the planet to where you want to land and you are good to deorbit. With atmosphere the landing spot is not at exactly the opposite side of the planet. But you will have this all calculated as the spacecraft is being designed and there will be tables for how far around the planet you will make it to deorbit. So you make sure to deorbit when your orbit will be over your landing site in the amount of degrees specified in the tables.
But the deorbit burn is not the last time you can normally steer the spacecraft. Capsules have their mass off center so the heat shield on the bottom will form an angled plane to the air in the atmosphere and therefore generate some lift. This allows the astronauts to roll left and right to control their descent and guide themselves towards the desired landing spot.
Even with all this they do not have to land extremely accurately. The recovery crew does have helicopters that can reach the landing site within minutes in most cases. Even if the astronauts had to do emergency landings they have managed to control it close enough to get recovered fairly soon.
There are however some Russian stories of uncommanded emergency landings where the astronauts did not have the luxury of picking a landing site. This was mostly during launch and not in orbit. These have demonstrated that recovery can take days and that the survival training and emergency camping equipment are necessary. Rumor has it that in one of these incidents they did have to cross a country boarder to conduct the recovery and did not ask for permission fearing that they would not be the first on scene, but this is unconfirmed and likely not true.
In general the emergency descent is only conducted when being in a remote wilderness, in the middle of the ocean, or in the middle of a war zone is preferable to being in space a few minutes longer in the current condition of the spaceship.
https://spotthestation.nasa.gov/tracking_map.cfm
This is the ISS orbital tracker. If you separated from the ISS and burned retrograde (slowed down), your would begin to descend, and land somewhere along that path. How far along depends on how much you slowed down, and can be calculated.
Wait for the earth to rotate under the ISS until the path lines up with where you want to go, then burn retrograde the correct amount at the correct time.
The spacecraft can then use aerodynamic effects to steer inside the atmosphere as it falls back. The extent that it can do this is known as cross range capability. The Space Shuttle had a lot, because it had wings, but even capsules have a little bit
https://spotthestation.nasa.gov/tracking_map.cfm
This is the ISS orbital tracker. If you separated from the ISS and burned retrograde (slowed down), your would begin to descend, and land somewhere along that path. How far along depends on how much you slowed down, and can be calculated.
Wait for the earth to rotate under the ISS until the path lines up with where you want to go, then burn retrograde the correct amount at the correct time.
The spacecraft can then use aerodynamic effects to steer inside the atmosphere as it falls back. The extent that it can do this is known as cross range capability. The Space Shuttle had a lot, because it had wings, but even capsules have a little bit
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