SpaceX rocket set for unintentional Moon landing – well, a piece of it anyway An astronomy software dev claims a Falcon 9 upper stage will hit the Moon in August, traveling at several times the speed of sound. The upper stage of the Falcon 9 rocket used to launch the Blue Ghost and Hakuto-R lunar lander is set to have its own close encounter with the Moon after loitering in orbit for more than a year, …
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A nice way of saying that two objects are destined to be coincident in space and time to the extreme prejudice to one.
2026-11-03 might shape up in this fashion when multiple trajectories of insanity are fated to converge.
Possibly more kiss·my·arse… than kismet.
"there are no humans on or around the Moon, ".
Once again us earthlings only worry when it's us at risk.without the slightest concern for those that are actually affected.
I've heard the Clangers are frantically negotiating with the Selenites for asylum, as they fear their house are to shallow to survive a direct impact.
Well - if we're really gong to get pedantic.... MACH numbers are dependant on the density of the medium.
IE, the "speed of sound" is different at high atlitude than it is at low altitude, due to the density of the gaseous soup we call "atmosphere".
So - even if the mph or kph figure can be stated directly, the MACH number hasn't been stated "well" (I was going to use accurately, but it's an approximation anyway), because they haven't given the correlatory altitude*.
Given the Moon's lower gravitational pull, IF it had an atmosphere, the density of said atmosphere at any given altitude would not the same as that on Earth....
"MACH numbers are dependant on the density of the medium."
An excellent point. So what is the speed of sound through lunar rock? If it's anything like the speed of sound through terrestrial rock, the speed of impact might be lower than the speed of the acoustic vibrations it will cause to travel through the moon itself, making the speed of impact subsonic in that context.
(I"m waiting for the Friday afternoon shift to end - can you tell?)
"There is, of course, a very sparse layer of gases surrounding the Moon and not a vacuum although it is often considered such."
There are also gas molecules in space so it's not a perfect vacuum either. There is a line where something is so vanishingly small that it makes no difference in all by a tiny fraction of a tiny fraction of cases. That's a concept I use all of the time in electronics. It's why Newton's equations can be suitable for some things rather than complicating a calculation with everything Einstein came up with.
"But if there were air, the speed would be about Mach 7, seven times the speed of sound"
It would be better to just express the speed in meters/second relative to the lunar surface at impact. Probably not that meaningful to most people, but they also won't have a direct grasp of other units either.
(I am the Bill Gray mentioned in the article.)
You can sort of blame me there, I suppose. Here's what I wrote on the subject :
https://www.projectpluto.com/25010d.htm#speed
There is, of course, no air and no sound on the moon [0], so a "Mach number" doesn't really make sense. But if there were air, the speed would be about Mach 7, seven times the speed of sound.
I'll claim some experience here, though. When the (only) previous bit of junk hit the moon unintentionally, the Chang'e-5 T1 upper stage in March 2022, I was frequently asked how fast it would be going when it hit, both in units all of us here would (I hope) understand, such as kilometers/second and km/hour, and in "traditional" units.
Much as heights are often measured in giraffes and volumes in Olympic swimming pools, I was asked for a more reader-friendly way of putting such things. I figured the above would do it.
[0] I managed to resist the temptation to insert "nobody can hear you scream".
The definitive reference for velocity calculations involving sheep in a vacuum (but not Welshmen) is this post by Lester:
https://www.theregister.com/2007/08/24/vulture_central_standards/
That's about 3½ Concordes (assuming there was air for it to fly in).
May I humbly propose the Concorde as the official Reg unit of speeds above Mach 1 (technically, 1 Concorde = Mach 2.05, while the absolute speed in km/h or snail-cm-day-1 per week depends on the gas temperature and mean molecular mass).
Lets hope lots of orbiting probes get a good view. Knowing exactly when and where it's going to hit this far in advance should hopefully give them a chance to get a good view. Events like this are very rare, where we know all about the impactor and the impact before it happens. It may be an accident, but there's lots of science we can do with it.
Sky & Telescope article about (six) lunar flashes seen by Artemis 2 crew. Looks to be small meteoroids, somewhat more than were expected to be visible.
There should be a "Pt Nemo" on the moon to aim leftover spacecraft at if there's a good chance something will impact the lunar surface. A store of refined metals could be very handy at some point rather than trying to smelt them from regolith. I don't think there's good chances of there being nice ore bodies on the moon like there are on Earth. Ore being defined as material that can be mined at a profit. If it's too hard to separate, it's just dirt. Profit on the moon will mean that it can be accomplished for less than sending the materials from Earth in cargo ships or in the form of something like decent stages.
Most heavy Earth-Moon missions are going to aim for a fairly central inclination orbit relative to the Earth-Moon plane cos you don't want to waste energy.
But precise orbits around the moon are tricky cos its gravity is rather lumpy. It's not quite the point mass that the equations would prefer
That is indeed a problem for objects actually orbiting the moon, but we don't really have very many of those. The much more common case is a flyby, or a mission that goes into orbit but leaves the upper stage flying past the moon. (Obviously, we do have the problem that both the orbiters and the flyby upper stages are increasing in number.)
An upper stage passing by the moon doesn't spend all that much time within the moon's sphere of influence. And, those "lumps" are modelled via a series of spherical harmonics that drop off quickly with distance. Models have been constructed for the gravitational fields of the terrestrial planets and the moon, and even for the much "lumpier" fields around Ceres and Vesta. (For the gas giants, their oblateness matters, and a subset of the spherical harmonics matters. The oblateness of the Sun matters, but it rotates so slowly and is so close to being a sphere that it's barely noticeable.)
Bottom line : if you wanted to plan an impact, you could do so (as was done for, for example, the LCROSS mission in 2009). It will usually be simpler to use the initial lunar flyby to eject the upper stage into heliocentric orbit, though. I think this is what was done with the New Glenn upper stage for the ESCApade mission late last year. (It definitely ended up in an orbit that will put it into heliocentric orbit for a long time, but I don't know if that was a lucky accident or a planned thing.)
I will not be surprised if the eventual "solution" involves throwing the upper stages into heliocentric orbit (because that's easy to do) and being slightly more careful about where satellites that are actually in lunar orbit crash.
"I know, he's got an ego the size of the crater this thing is going to make, but what about the name?"
Musk Crater should be a spot devoid of a sizeable crater, just the promise that there could be a really big one there sometime in the future. A year or maybe a year and 3 months.
> he's got an ego the size of the crater this thing is going to make
And charisma the size of one of the pebbles it's going to dislodge.
(Not even sure now whether that was a conscious or subconscious ripoff of the scene in Red Dwarf- of Rimmer being rebooted- that it instantly reminded me of. I notice *that* has Rimmer being almost entirely full of "arrogance" with a pinkie's worth of "charisma", so that would work almost as well.)
As long as it doesn't knock the moon out of orbit towards the earth [Film: Moonfall or else casue a Space 1999 type catastrophe]
And hopefully it won't damage the monolith on the far side [2001]
Yes, I'm aware that Kinetic energy = 1/2 MV^2 and that a small piece of space junk isn't going to significantly affect the moon [approximate mass = 7.347e22 kilograms].
