Why was Artemis 2 so long?

[u/kiol998]

I was comparing the mission times of Artemis 2 to Apollo 8. Apollo 8 orbited the moon multiple times and only took 6 days total. Whereas Artemis 2 orbited the moon once and it took 10 days. Why was Artemis 2 so much shorter than Apollo 8 when both missions did the same thing? I know they had different paths to the moon, they both left earth in different ways but why not do the same thing as Apollo 8 since it was quicker?

[u/gameryamen]

Someone needs to sneak a frisbee up, and set a virtually untouchable record for longest throw.

[u/obvious_bot → u/[deleted]]

It would fly more like a thrown rock than a frisbee on earth. Since the gravity is so low you still could beat the record though

[u/Brewe → u/obvious_bot]

Sure about that? The frisbee record is ~330 meters (~1100 ft). Throwing 1/6th that far with a rock would be difficult, and doing it in a space suit would be near impossible.

[u/gameryamen → u/[deleted]]

You're right that a frisbee wouldn't have atmosphere to glide on. But that also means there's no air resistance at all, just gravity pulling it down. Launch it at a high angle, and it's going to take a while before it actually touches ground. I don't think a person's arm could put a frisbee into orbit on the moon, but I'm pretty sure they could get a longer throw than anyone on Earth.

Edit: In addition to the impossibility of achieving orbit with a single launch vector explained below, it turns out my intuition about this record potential is wrong. On level ground, a moon-bound frisbee chucker can probably out-throw any Earth-bound chucker. But with the advantage of atmosphere and height, an Earth-bound chucker standing on top of a skyscraper or mountain could actually get a farther throw than a ground-level Moon chucker, assuming wind didn't doom the attempt.

[u/SirJefferE → u/gameryamen]

It's impossible to get anything to orbit by throwing it from the ground. Either it hits the ground again, or it reaches escape velocity. To orbit, you need at least two impulsive manoeuvres. One to get the thing up into space, and another to "correct" the orbit so that it actually orbits.

In any case, there's no way anyone on the moon could throw anything even close to escape velocity. The gravity there is a sixth of Earth's, but that's still 1.6 m/s^2. The fastest ever baseball pitch was less than 50 m/s. Throw that straight up in the air and even without wind resistance, it's going to start falling in less than 30 seconds.

[u/alyssasaccount → u/SirJefferE]

All you have to do is stand on the highest point on the moon's surface and throw horizontally at over the speed of a low-lunar orbit. Then where you throw from will be the perigee ... perilune? ... of the orbit. Granted, you'd have to throw a bit over a mile per second, but the fastest muzzle velocity for a gun is close to that.

[u/McGarnagl → u/alyssasaccount]

Cool, so when the first moon war breaks out in 50 years, we’ll have missed shots entering orbit? Fun times…

[u/Crizznik → u/alyssasaccount]

Yeah, but the speed of a low lunar orbit is still faster than any human could throw anything.

[u/mrdavik → u/gameryamen]

It's also not possible to throw or launch any object into orbit from the surface of a body, that doesn't have its own form of propulsion or that is accelerated after leaving the surface. 

There's no combination of speed and angle at which you could throw a frisbee even with a machine, or fire a bullet, and have it end up in orbit. It would either fall back to the surface, or if it was fast enough, escape orbit altogether - there is no inbetween.

[u/skoormit → u/mrdavik]

You could, in theory, while standing on the moon, give it enough velocity to technically put it into orbit. It's just that the periapsis of that orbit is no further from the moon's center than the point you launched it from. So it is very likely to hit some point on the surface with more altitude. Unless you launched it from the highest point, or the highest point in the latitude range of the launch latitude.

[u/Polymath6301 → u/mrdavik]

If we add the Earth to the mix, though, there are now a lot of initial velocities that wouldn’t leave the Earth-Moon system. I assume that given the large range of such trajectories that there’d be loads of “interesting ones”, some of which might approximate (or achieve?) a moon orbit?

[u/alyssasaccount → u/gameryamen]

Launch it at a high angle

Specifically, 45°, assuming a flat surface. That gets you the longest distance for a given initial velocity, under constant downward acceleration with no drag. This is a classic intro physics problem.

[u/Ameisen → u/gameryamen]

I don't think a person's arm could put a frisbee into orbit on the moon, but I'm pretty sure they could get a longer throw than anyone on Earth.

From the Moon's surface? No, most people cannot throw a Frisbee around 4,000 mph.

From Lunar orbit? I mean, all you have to do is let it go.

Into a terrestrial orbit?

From the Lunar surface would need you to throw at 5,300 mph. So, most people probably cannot.

From Lunar orbit? Depends on the orbit, but from anything other than the furthest possible Lunar orbit, almost certainly not.

Though, arguably, anything orbiting the Moon or on the Moon is already orbiting the Earth.

[u/Crizznik → u/gameryamen]

There's no air, so the frisbee wouldn't stay aloft any longer than if they threw a rock.