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> Come to think of it, that's how the Apollo capsule also confirmed its location. Isn't that still how it's done? - When leaving earth orbit there isn't GPS or

> Come to think of it, that's how the Apollo capsule also confirmed its location. Isn't that still how it's done? - When leaving earth orbit there isn't GPS or such, the guidance to the moon or further still uses star trackers.

AStonesThrow 1y ago
The Voyager space probes for sure use visual fixes on guide stars, such as Alpha Centauri (and our own Sun?) to ensure correct orientation. Of course, they don't need to navigate much, since given the relative velocities, their thrusters wouldn't make much difference. And there is a quite-famous scene in Apollo 13 where they literally line-up the Moon itself in the reticule so that their engine burn puts them on exactly the correct trajectory.
SSLy 1y ago
I believe star maps are also baked into ICBMs
- agurk 1y ago
  Some SLBMs (Submarine Launched Ballistic Missiles) use star sighting to correct their trajectory mid-flight. ICBMs launched from silos know exactly where they're starting from, whereas a submarine is both moving, at different depths and has some error to knowing exactly where it is. Missiles use inertial guidance, so knowing your starting your point is crucial. How accurate a missile needs to be is a whole other dimension though. If the value of a missile is as retaliation to destroy a city (countervalue) then it can be a large warhead and "miss" by quite a margin but needs some form of credible survivability of an enemy first strike. If the missile is to be used to destroy enemy military installations (counterforce) then it needs to be a lot more accurate but usually the implication is as a first strike so less survivability is required. When you have nuclear weapons that you can drop from manned aircraft, ICBMs from silos and SLBMs controlled by different military branches there is going to be a lot of politics over what the missile is for, which will determine its required accuracy, which will be a factor on if it needs star sighting.
- p_l 1y ago
  ICBMs early on applied star tracking to increase precision, starting with pretty simple analog systems (I recall something about shifting a tape with simulated tracker signal to a position matching the launch time) to modern digital map systems.

AStonesThrow 1y ago

The Voyager space probes for sure use visual fixes on guide stars, such as Alpha Centauri (and our own Sun?) to ensure correct orientation. Of course, they don't need to navigate much, since given the relative velocities, their thrusters wouldn't make much difference. And there is a quite-famous scene in Apollo 13 where they literally line-up the Moon itself in the reticule so that their engine burn puts them on exactly the correct trajectory.

SSLy 1y ago

I believe star maps are also baked into ICBMs

agurk 1y ago
Some SLBMs (Submarine Launched Ballistic Missiles) use star sighting to correct their trajectory mid-flight. ICBMs launched from silos know exactly where they're starting from, whereas a submarine is both moving, at different depths and has some error to knowing exactly where it is. Missiles use inertial guidance, so knowing your starting your point is crucial. How accurate a missile needs to be is a whole other dimension though. If the value of a missile is as retaliation to destroy a city (countervalue) then it can be a large warhead and "miss" by quite a margin but needs some form of credible survivability of an enemy first strike. If the missile is to be used to destroy enemy military installations (counterforce) then it needs to be a lot more accurate but usually the implication is as a first strike so less survivability is required. When you have nuclear weapons that you can drop from manned aircraft, ICBMs from silos and SLBMs controlled by different military branches there is going to be a lot of politics over what the missile is for, which will determine its required accuracy, which will be a factor on if it needs star sighting.
p_l 1y ago
ICBMs early on applied star tracking to increase precision, starting with pretty simple analog systems (I recall something about shifting a tape with simulated tracker signal to a position matching the launch time) to modern digital map systems.