Why people make temperature in space a big deal? It's mostly vacuum and has no heat capacity. Sun radiation is the real threat, but the concept of temperature can't even be applied to vacuum.
Athena landed in a dark crater where the temperature was -280° F / -173° C
151–160 of 277 posts
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#152Earlier quoted context omitted.
Noise at 30km altitude probably points more towards a sensor issue than dust.
May it be that laser bounced off exhaust plume?
Unless their processing is very weird, that shouldn’t be the issue.
You send a pulse and record the output of a detector to listen for the reflection. If the laser is reflected at the plume, you should get some pulses very quickly, but also faint and spread out in time, which you would be able to tune out. And the real response from the ground should be more narrow because it’s reflecting at a single distance.
If very short range noise influences the signal when measuring 30km real distance, you’re doing something wrong.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#153Why people make temperature in space a big deal? It's mostly vacuum and has no heat capacity. Sun radiation is the real threat, but the concept of temperature can't even be applied to vacuum.
The ground it's laying on though does though.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#154If you take the time to study the documentation from the 1950s & 1960s, the engineering culture of that era appears to be markedly different from the engineering culture prevalent today. And I think it's deeply rooted in the symbiotic relationship between computing, Baumol's cost disease and our obsession with precision, results-oriented, MBA-style-min-maxing, "good enough for government work" engineering. Robert Tru…
> China adopted the Surveyor / Apollo-era philosophy. Their first successful lander, Chang'e 3, used the same hover & fall technique as Surveyor. Dropping the last 4 metres isn't a sign of having a ruggedized, over-speced "takes a lickin' and keeps on kicking' approach". In lunar gravity, you could drop a raw egg from that height and not perturb the chick inside. Instead the aim is to avoid throwing up too much moon…
> Dropping the last 4 metres isn't a sign of having a ruggedized, over-speced "takes a lickin' and keeps on kicking' approach". In lunar gravity, you could drop a raw egg from that height and not perturb the chick inside.
Just for maximum pedantry:
Falling 4 m on the moon is like falling 66 cm or about 2 feet on earth. I don’t know about your eggs but the ones I know wouldn’t survive that.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#155Why people make temperature in space a big deal? It's mostly vacuum and has no heat capacity. Sun radiation is the real threat, but the concept of temperature can't even be applied to vacuum.
The space surrounding you may not have a temperature but your spacecraft does, and it will lose heat via radiation, batteries and electronics will stop working after your temperature reaches a certain low.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#156Earlier quoted context omitted.
The top-heavy design didn't help things either. I'll be shocked if they don't go three-for-three on landing sideways given IM3 has the same tall design.
>> The top-heavy design didn't help things either Just wait for SpaceX to start trying to land starships on the moon. Also vertically. Also doomed to tip over whenever the surface is slightly out of spec. https://www.spacex.com/humanspaceflight/moon/
Why does this even have to be a problem?
We can send small probes to image the moon in incredibly high resolution. It's a big place I'm sure there is a perfectly flat rock somewhere they can use.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#157Earlier quoted context omitted.
It touched down with a large horizontal velocity component
That’s another thing that bothered me about this story. They said they knew where the craft was , relative to the surface of the moon. Wouldn’t that also mean they should know of any substantial horizontal (x/y) component of velocity?
Yes, through image analysis.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#158If you take the time to study the documentation from the 1950s & 1960s, the engineering culture of that era appears to be markedly different from the engineering culture prevalent today. And I think it's deeply rooted in the symbiotic relationship between computing, Baumol's cost disease and our obsession with precision, results-oriented, MBA-style-min-maxing, "good enough for government work" engineering. Robert Tru…
If you look at Change 5 and 6, they seem to do the same image processing based landing control. This doesn't seem to be a cost cutting measure, since the image processing is computationally much more complex than using a radar altimeter.
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#159Earlier quoted context omitted.
There are multiple factors. The biggest ones are reflected sunlight; infrared and thermal conduction from surrounding rocks; and the Moon's internal heat (the region between the core and the mantle has a temperature of over 1,300 C).
Also, little atmosphere means the sun doesn't heat up the area like in your house. Once you're out of the sunlight, it's darn cold.
The question isn't “why is it cold” but the opposite “why is it so hot” (100K when the universe radiation is 3K)
Re: Athena landed in a dark crater where the temperature was -280° F / -173° C
#160Earlier quoted context omitted.
Well, there's a natural barrier to entry, i.e. it costs millions on dollars and years of time to be able to "crash" your "junk" onto the surface. So it's not like a bunch of hobby rocketeers are throwing away their McDonald's garbage. By the way, in comparison to the cost and complexity of said "junk", everything you own is cluttering up the Earth. You should really do something about that.
Are you making the argument that anyone with enough money should be able to do whatever they want on the moon? Giant neon McDonalds billboards visible from everywhere on Earth? Mining with zero restriction on impacts to the surface of the Moon or its atmosphere? Apparently the HN crowd doesn't stand anyone criticizing a "startup", but I'm asking a legitimate question. So far most of the junk we've launched onto the M…
Are you making the argument that for some reason we should heavily discourage lunar exploration for the sake of keeping the moon pristine?
Why is this more important than expanding our ability as a species to explore space?