Artemis 2 launch - humans return to the Moon after 54 years

[.Scott]

Artemis, twin of Apollo.
Fitting name for the second series of manned moon missions.

And she personified the Moon. But Artemis was the older of the twins.

 

[PeterDonis]

Did the rocket speed up when moon's gravity became stronger than earth's?

I'm not sure I would expect it to, because the trajectory it's following is so far from the Moon, as compared with the Apollo missions. I haven't run the numbers, but I suspect the Moon's force is just curving the trajectory, not speeding it up.

 

[Charles Link]

I did find from one article in a google that the expected speed at closest approach would be 3,139 m.p.h. I am lead to believe the website that showed no increase all day and a decrease to below 1,000 m.p.h. was inaccurate.

Edit: I found a video on Facebook that may offer at least a partial explanation: The rocket passes the moon to the left of the moon and then loops to the right when it is behind it, with the moon moving right to left. The 3,139 number might be the speed relative to the moon. I estimate the moon's right to left speed at about 2,000 m.p.h. Edit: With a google I see the moon moves about 2,288 m.p.h. in its orbit around the earth.

Meanwhile an acceleration of the rocket to the right will create a velocity component to the right that adds as a vector to the forward velocity component (relative to earth) and may not affect the speed w.r.t. the earth all that much.

 

[Jonathan Scott]

The area brightness of an object does not depend on distance.

True of course, and presumably relevant in this case, but to avoid confusion this needs to be accompanied by the important point that if the angular size of an individual object (such as a star) is smaller than the sensor or eye resolution then the apparent brightness is decreased accordingly (which is presumably the main factor limiting the number of stars which we can see with the naked eye).

 

[pinball1970]

Metro UK today, Wiseman said humans have "not evolved" to see images like the ones they are seeing.

 

[DennisN]

Some gorgeous photos here:

Artemis II Lunar Flyby (NASA)
Quote: "The first flyby images of the Moon captured by NASA’s Artemis II astronauts during their historic test flight reveal regions no human has ever seen before—including a rare in-space solar eclipse. Released Tuesday, April 7, 2026, the photos were taken on April 6 during the crew’s seven‑hour pass over the lunar far side, marking humanity’s return to the Moon’s vicinity."
https://www.nasa.gov/gallery/lunar-flyby/

Examples:

A Setting Earth

Shadows at the Edge of Lunar Day

Shadows Across Vavilov Crater

They got better Moon photos than me!

Of course it is impossible for us terrestrial astrophotographers to get the Earth in a shot without faking it, but how can we at PF counter this novel threat from these four upstarts sitting in a tin can?

Can I spend a fortune and buy dedicated gear for Moon photography? (maybe, but I won't )
Can @timmdeeg get himself a new super expensive lens?
Does @russ_watters have any unknown tricks up his sleeve?
Can @Andy Resnick conjure up some optical magic with his gear?
Can @collinsmark direct his monstrosity of a scope towards the Moon and pull off some stunts?

What to do, what to do?

 

[DennisN]

Look, here is one of the upstarts taking photos:

Photographer at Work

art002e009295 (April 6, 2026) – Astronaut Jeremy Hansen captures an image through the camera shroud covering window 2 of the Orion spacecraft. The camera shroud, essentially a curtain with a hole for the lens to pass through, is used to prevent light from the cabin from reflecting on the windowpanes.
Image Credit: NASA

Source: https://www.nasa.gov/image-detail/amf-art002e009295/

I think this is close to cheating; he was one lucky dude and got really, really close to his subject (the Moon), and furthermore he is enjoying the benefits of zero gravity.
Bah! And I bet he is using image stabilization too on his camera. I'm telling you, he had it easy.

(I'm only joking, of course )

 

[sophiecentaur]

I'm not sure I would expect it to, because the trajectory it's following is so far from the Moon, as compared with the Apollo missions. I haven't run the numbers, but I suspect the Moon's force is just curving the trajectory, not speeding it up.

The closest approach to the moon is much greater than for the Apollo missions. That would, of course, be a much lower energy requirement. Thinking in terms of orbital energy for the lunar encounter, the GPE change is much less for the pass by of Artemis pass than going down to a low lunar orbit and then landing and takeoff.
It does surprise me that they didn't choose to carry that much extra fuel to allow a lower lunar orbit. Future landings would obvs need the full amount of fuel. I couldn't imagine that the navigation would have been a problem.

 

[Filip Larsen]

https://arstechnica.com/space/2026/...design-to-fix-orion-spacecrafts-leaky-valves/

Orion helium leak no threat to Artemis II reentry, but will require redesign.
After leaks on Artemis I and II, Orion’s next flight to the Moon will need new valves.
[...]
The valves are inside the European-built service module, which the Orion spacecraft will jettison just before reentering the atmosphere Friday evening.

 

[pinball1970]

There was an issue with heat shield in 2022 with Artemis 1.

https://www.nasa.gov/missions/artem...use-of-artemis-i-orion-heat-shield-char-loss/

They will be coming in a steeper angle so less time at high temperature but will that not also create more friction?

 

[mfb]

NASA stream for reentry (landing in ~1.5 hours)

A steeper angle will lead to a higher peak heat load but the heat shield is designed for that. It's the slow, long-term heating in deeper layers that caused the ablation.

True of course, and presumably relevant in this case, but to avoid confusion this needs to be accompanied by the important point that if the angular size of an individual object (such as a star) is smaller than the sensor or eye resolution then the apparent brightness is decreased accordingly (which is presumably the main factor limiting the number of stars which we can see with the naked eye).

The discussion was about a nebula, not a point source.

 

[neilparker62]

Some snapshots taken from the live stream. Times as recorded on my cellphone. GMT+2

23:49

01:54

02:07

02:09

 

[Charles Link]

In regards to posts 60 and posts 63 above, I did a calculation assuming the total energy of the rocket stays constant using the gravitational potentials of the earth and moon, and that calculation showed the rocket should speed up considerably, up to about 2600 m.p.h. I determined that calculation to be in error though.

The moon, the source of the second gravitational potential was moving at about 2200 m.p.h. Thereby, the rocket didn't move across the gravitational potential enough (in the reference frame of the earth) to get the complete $dW=\vec{F} \cdot d \vec{s}=\Delta(mv^2/2)$. Instead, much of the closure in distance was because of the motion of the moon. The way I initially treated it as a static/fixed gravitational potential was incorrect. To apply the method of gravitational potential to get the change in $v^2$, it seems it is necessary to go to the reference frame of the moon. Thereby I have concluded that the nasa data showing no increase in speed measured w.r.t. the earth, (the speed stayed nearly steady at about one thousand m.p.h.), even in its closest approach to the moon, was apparently completely valid.

I thought I was somewhat clever in applying the use of two gravitational potentials to compute the $v$, but it seems that if one or both of the two sources are moving, the method can not be used to compute the kinetic energy of the 3rd body in the simple straightforward manner that I tried to employ.

Note: This was the first time I ever tried to work a problem involving two gravitational potentials at the same time. It would have worked if the moon were stationary, but it isn't.