valcatosi t1_j9zgvru wrote

You're not dumb. The only thing you're missing is that acceleration is a change in velocity, not a change in speed.

What does that mean? Picture a car driving down the freeway. The speed is what you see on the dashboard, and the velocity is that plus the direction you're going. Now picture driving around a curve in the freeway. The speed stayed the same, but the velocity changed because you changed direction, and while you were on the curve you felt a sideways force. That force is the result of the acceleration that changed the car's velocity but not its speed.

If that makes sense, now picture a car driving around a circular track. The speed stays the same all the time, but the velocity always changes because the car's direction is always changing. The result is that even though the car isn't speeding up or slowing down, you feel a force - that's acceleration!


valcatosi t1_j9z2ta7 wrote

The Lagrange points themselves are (theoretically) literally points. Zero spatial extent. The reason they're useful is that you can enter what's colloquially known as a "halo orbit" around them. Those orbits can be enormous - there's plenty of room for all the telescopes we could ever send.


valcatosi t1_j9vkopo wrote

This really bugs me. Zhuque-2's methane stage operated nominally and a later unrelated stage failed. That has no bearing on "methane engine to orbit" and only has any possible bearing on "a rocket with some methane in it has a fully nominal mission". If the point is methane fueled to orbit, Vulcan and New Glenn (lol) are not in the running, since their methane stages don't get the vehicles to orbit.