Falcon 9 is an orbital booster that's landed dozens of times on US soil. Suggesting this spacecraft has achieved some kind of world first is totally ridiculous and diminishes the actual achievement.
The gravitational potential energy of a 100kg payload in 100km orbit is 98 MJ. The kinetic energy of a 100kg payload in 100km orbit is 3042 MJ, over 30x more. So surviving reentry from orbit is orders of magnitude more difficult than surviving a straight up/down shot.
Now F9 boosters obviously have a horizontal velocity as well that they need to cancel out, but suborbital and orbital spacecrafts are very different beasts and it's absolutely noteworthy. It's the difference between surviving a car crash at 20 mph vs 95 mph. One is trivial, the other requires a heck of a lot of engineering.
E=K+U=GmM/2r−GmM/r=−GmME/r. We can see that the total energy is negative, with the same magnitude as the kinetic energy. For circular orbits, the magnitude of the kinetic energy is exactly one-half the magnitude of the potential energy.
Do the calculation over.
https://phys.libretexts.org/Bookshelves/University_Physics/U....
This is calculating the gravitational potential between two point masses. In other words, the potential energy if both masses were singular points at a distance from each other.
I was quoting the potential energy differential between being 100km over the ground, and on the ground. This is 98 MJ for a 100kg object, and that's what you have to cancel out to land back on Earth. The total gravitational energy of that object to the Earth's centre is more like 6300 MJ, but that's a meaningless number.
This is great because it does make it practical to recover the booster, but it's only possible by making the second stage significantly larger and more powerful than comparable rockets that stage later.
If the booster got up to orbital velocity, it would burn up just like the Rocket Lab "mothership" host satellite that accompanied the Varda capsule. They were coupled together, the mothership performed the braking burn to adjust their orbit into a reentry trajectory before the two separated. Only a minuscule amount of drift separated the two as they hit the atmosphere, but while the mothership burned up, the capsule survived.
If Falcon's booster achieved orbit, it would burn up just the same. The only reason it doesn't, is that it's only going a tiny fraction of orbital velocity when it comes home.
Dragon would qualify, except it lands on the ocean, so not "US soil".
agreed about dragon. those fuckers do orbit!
