I had to explain to my wife and kids (not that I'm in this field, but I also have to remind myself) that we are able to pinpoint where the craft will land, when it will land down to the minute, because of ... just ... math. And we're able to get them there and back because of science.
It all boils down to equations that describe the world accurately, and a way of experimentation, iteration, thinking that gets us all the way to do something this unbelievably complex.
The analogies for these things like "hitting a golf ball into a hole in one 5,000 miles away" are always fun.
I like starting from the fact that Ptolemy was able to get the accuracy of the "motions of the heavens" down so well that it took more than a thousand years to get observations that showed discrepancies. The math, it maths.
I always feel like these analogies don't really fit the real space flight as you quite often have a lot of time to correct the trajectory if you get it roughly right during launch and even that takes a couple minutes. You also have closed circuit guidance and external radar stations to verify the trajectory.
You really don't have anything like that when playing golf, so I don't thin it is a good analogy.
But for the old Sprint anti balistic missile - that was spot on. :D Hitting ICBM warheads kilometers abobe ground, second before detonation - yeah, that fits. It also dispelled the myth that you can't communicate to compact craft due to re-entry plasma. Of course you can, just use a 30 MW radar beam & it will get through just fine! Not to mention the Sprint missile was protected by an ablative heatshield and covered by plasma going up during launch. :D
There’s a big difference (not really as much as you might think because fuel is limited) between a single shot with no thrusters and a rocket that has all sorts of adjustments possible.
It’s all in fun, really, like the old analogies involving hard drive heads and jet planes.
I feel like it’s “easier” with space math because there’s so little to interfere with the course. With a golf ball, the basic math is easy, but the slightest bit of wind throws it off way beyond the acceptable error, and you can’t model all the wind perfectly.
The first-order approximations are easy. When you start adding up all the other factors, it gets complicated fast. The solar wind, which isn't constant, affects trajectories. Earth's atmosphere is neither homogenous nor perfectly predictable along many dimensions: upper-level wind speeds and directions, air density, and temperatures, to name a few. The Moon's gravitational field is very lumpy. Earth's gravitational field, while relatively smooth compared to the Moon, also isn't perfectly uniform. Propulsion systems have tolerances. Same with parachutes. The location of the vehicle's center of gravity affects everything.
All of these factors and more have to be taken into account if you want your predictions to be accurate. Aside from telemetry processing, most of the computing power on the ground during a space mission is used for churning out navigation solutions.
Agreed.
Fun info: The NASA orbital codes include things like photon pressure... from sunlight reflected off of other planets in the solar system. At some point, I think they are just showing off :)
Not a great analogy because there actually is interference and golf balls aren't typically monitored and course corrected during flight
I'd add a caveat to this.
We can do this because of war.
We know where it will land accurately because that maths and physics has been sharpened with butt loads of data. Even the reentry blackout has links to war in Plasma Stealth[0].
That data was mostly obtained because we want to know where our ICBM warheads will land. And where the enemies ICBM warheads will land so we can work on the problem of shooting them down.
The Russian Kinzhal missile can hit targets at mach-10, with a plasma aura making it's terminal phase hard to track on Radar. But after some data was collected Patriot missile systems were able to intercept about 1 in 3 air launched Kinzhal missiles. Then minor terminal adjustments were introduced and interception fell to about 1 in 20. Now there's a constant cat and mouse game going on in Ukraine.
On the one hand that's a good thing, our combative efforts being sublimated into curiosity of the world.
On the other hand, we still put far more effort into furthering our ability to destroy the world.
[0] https://en.wikipedia.org/wiki/Plasma_stealth
IIRC reentry plasma is actually highly radar reflective - so it is not hard to track, just hard to hit due to the speed, as there is limited time to do it.
If that were the case then the mach-10 Kinzhal would be harder to hit than the mach-5 Kh-32.
But the interception rate for the Kh-32 is basically nonexistence (<1%).
The Kh-22/32 is why mach-5 + maneuverability is the current goal of offensive missile systems.
The plasma has complex interaction with radar, it's not stealth as in entirely invisible just chaotic scattering and reflections. The result is a jamming effect preventing a definite intercept solution.
On the other hand the plasma shows up on satilite based IR tracking systems.
To say “because of war”, you would also have to prove we could not do it without war.
That's an absurd statement. By your logic, you can't just say that we have the smallpox vaccine "because of Edward Jenner". Because you would also "have to prove we could not do it without Edward Jenner". What does that even mean??