61 replies
1d1h
On the other hand a reentering ICBM warhead (test) looks like from the ground as if the gods are angry with you and your general vicinity: https://www.youtube.com/watch?v=2a1acYZ93yc
38 replies
1d2h
for people using non-medieval units of measure, √(GM/r) is a fairly precise approximation to circular orbital speed, and units(1) is good at calculating things like this:
You have: (G earthmass / earthradius)**.5
You want:
Definition: 7909.7861 m / s
24 replies
1d1h
I find it interesting people are pretty hardcore that meters is a superior measure based on its lack of human foot reference, but still hold onto Celsius. Basing a unit on the temperatures water phase changes at 1atm is as barbaric and anthropomorphic. That’s why I only measure with a zero based on actually zero. Negative heat?? Wtf.
12 replies
1d1h
Your argument doesn't make that much sense to me when Kelvins, while 0=absolute 0, have the same magnitude as a degree Celsius. I.e. they're still based on water phase changes at 1 atm.
11 replies
1d1h
The language defining the Celsius unit originally was: "The arbitrary points which coincide on the two scales are 0° and 100°"
Those distances are arbitrary, and not specifically moored on the anchors of 0 and 100. Kelvin units are moored however on a fundamental anchor of zero heat energy, with arbitrary sized units above. It happens they were later calibrated to the Boltzmann constant, which itself is anchored on the triple point of water. None of this is based on human experience.
10 replies
1d1h
it's water because the humans are mostly made of water. rumor has it that on 𐍨𐍓𐍰𐍚𐍠 they use the triple point of what the humans call 'phosphoric acid' (it's a toasty place) and in 𓃾𓂃𓂌𓀩 they use the triple point of the ammonia-methane eutectic
5 replies
1d
It's funny that I can't even accomplish an emoticon in these comments while some people manage to draw complete scenes or algebraic formulas interleaved with the text.
I must admit that, unlike a lot of HN'ers, I'm using a virtual keyboard on a heldheld device to type comments; I never took the effort of looking up how it is done though it must have to do with extended char sets.
4 replies
1d
most emoji are banned, as are nonstandard space symbols like thin space and some other things. emoticons (things like :-) and XD) are allowed. generally alphabetic characters and digits are allowed, and some other things, but i think unknown unicode is forbidden by default. https://news.ycombinator.com/item?id=23440551 has some investigation and results which are probably still accurate
i do most of my algebraic formulas with the compose key and a custom compose map mostly written by mark shoulson https://github.com/kragen/xcompose
for the above, after a false start picking random unicode characters, i realized that maybe i shouldn't use a modern language because someone who actually uses the language might feel like i was calling them an extraterrestrial, so i switched to googling archaic scripts. i pasted part of the old permic table from wikipedia
>>> s = '''𐍐 𐍑 𐍒 𐍓 𐍔 𐍕 𐍖 𐍗 𐍘 𐍙 𐍚 𐍛 𐍜 𐍝 𐍞 𐍟
... U+1036x 𐍠 𐍡 𐍢 𐍣 𐍤 𐍥 𐍦 𐍧 𐍨 𐍩 𐍪 𐍫 𐍬 𐍭 𐍮 𐍯
... U+1037x 𐍰 𐍱 𐍲 𐍳 𐍴 𐍵'''
>>> print(''.join(c for c in s if ord(c) >= 0x10350))
𐍐𐍑𐍒𐍓𐍔𐍕𐍖𐍗𐍘𐍙𐍚𐍛𐍜𐍝𐍞𐍟𐍠𐍡𐍢𐍣𐍤𐍥𐍦𐍧𐍨𐍩𐍪𐍫𐍬𐍭𐍮𐍯𐍰𐍱𐍲𐍳𐍴𐍵
>>> len(''.join(c for c in s if ord(c) >= 0x10350))
38
>>> permic = (''.join(c for c in s if ord(c) >= 0x10350))
>>> ''.join(random.choice(permic) for i in range(5))
'𐍨𐍓𐍰𐍚𐍠'
>>> print(''.join(chr(i) for i in range(0x13000, 0x14000)))
𓀀𓀁𓀂𓀃𓀄𓀅𓀆𓀇𓀈𓀉𓀊𓀋𓀌𓀍𓀎𓀏𓀐𓀑𓀒𓀓𓀔𓀕𓀖𓀗𓀘𓀙𓀚𓀛𓀜𓀝𓀞𓀟𓀠𓀡𓀢𓀣𓀤𓀥𓀦𓀧𓀨𓀩𓀪𓀫𓀬𓀭...
>>> hiero = (''.join(chr(i) for i in range(0x13000, 0x13100)))
>>> ''.join(random.choice(hiero) for i in range(4))
'𓃾𓂃𓂌𓀩'
it's funny how this conversation has swung from the extreme of universal constants of the universe to the opposite extreme of completely arbitrary and historically contingent things like which ideograms (themselves completely arbitrary) are prevented from being posted by implementation bugs in hacker news
1 replies
23h41m
Exactly a good reason why I love HN comments so much. The off-topic reply is frowned upon.
Thanks so much for this, let's see if copy paste works on this unix derived os. 𓀝𓀞𓀟𓀠𓀡𓀢𓀣𓀤𓀥
0 replies
23h4m
i'm glad you liked it!
1 replies
23h32m
Oh, they were just random hieroglyphs? I thought you made a tiny cartoon of a man flipping a table.
0 replies
23h28m
hahaha, that's awesome! i hadn't even noticed that it sort of looks like that
1 replies
22h31m
That’s why we picked water, but water exists everywhere. Earth, the kings foot, 1atm, are specific to the human experience.
0 replies
21h16m
most of the non-dark-matter non-dark-energy mass of the universe finds itself in conditions that prevent the existence of water: black holes, degenerate-matter stars, conventional plasma stars, things like that. almost all of the rest is hydrogen and helium, so water exists there in the same sense that uranium exists here. but, although almost all of the universe is cold enough to freeze hydrogen, its vapor pressure is high enough at the cbr that most of it is vapor, so basically none of that is solid. solid objects do have a substantial amount of water in them, although if our solar system is typical, many of them don't
but sure, if it turns out that there are electron-degenerate-gas vortex intelligences on the surface of white-dwarf stars, they could very likely work out some way to launch robotic probes out of the star into places where water could exist, so that they could measure its triple point. and the folks on 𐍨𐍓𐍰𐍚𐍠 use trace amounts of water in their biology (it's a reasonably powerful base) and have isolated it in liquid form in their cryogenic laboratories. it's accessible in a way that the artifact kilogram and artifact meter and the circumference of the earth aren't
1 replies
19h31m
triple point of the ammonia-methane eutectic
Which is a shame that the temperature scale is still anchored in that arbitrary mix, picked by a lazy apprentice. It's also historically base-10, not like the modern systematic base-8 units.
(Can ammonia actually alloy with methane? Their crystalline lattices don't seem to be compatible, and they don't react together.)
0 replies
15h28m
i don't actually know. however, the same considerations would suggest that methane clathrates in water are impossible, which turns out not to be true. methane freezes at 90 kelvin, so if there's a eutectic, it would be lower than that.
8 replies
1d1h
guilty as charged. it gets worse, though: meters are originally based on the size of the earth, but humboldt's expedition (?) fucked up the measurement and now we're stuck with a meter that's significantly too short, nominally defined as the distance light travels in 9192631770/299792458 cycles of the hyperfine transition radiation frequency of cesium-133. you probably think this is a goddamned joke but it's not
i ask you, what the fuck kind of number is 9192631770? is that a hexadecimal encoding of linus torvalds's first child's birthdate? no, it's just a random fucking number derived from the sumerian base 60 numbering system and the average rotational speed of the earth in the 20th century. the kelvin has a similarly filthy history; it's when the thermal energy changes by 1.380649e-23 joules, because that makes the triple point of water come out to 273.16 kelvins. so now we have to preserve those numbers for all eternity like they're the fucking holy writ of the priestesses at delphi in order to interpret scientific papers from the 19th and 20th century. (and don't get me started on the motherfucking calendar. jesus jumping blue christ.)
you will be pleased to learn about https://en.wikipedia.org/wiki/Natural_units (which i used in https://dercuano.github.io/notes/2017-sap-allocation.html because i'm uncreative) and https://en.wikipedia.org/wiki/Duodecimal#Systematic_Dozenal_...
3 replies
1d
You probably know all this, but it is fun to write. Units are parts of models. Used Models were the best in class, at the time they were derived or adopted. Models are wrong and get replaced by less wrong models over time.
That said I think meters and Kelvins are doing their job just fine even for use with rocket science. I'm glad I learned the SI units at school, they reduced the number of constants a lot in physical formulas.
2 replies
1d
yeah, but there are still a lot of constants even with the si units, which is because they predate the discoveries of many of the constants. more constants generally means more arithmetic operations you can accidentally leave out of your program and constants you can get wrong. this was a bigger concern in the slide-rule era, but the humans are still infallible, so it hasn't gone away entirely
i don't think it makes sense to describe miles or meters or stoney lengths as 'wrong' or 'right'; you can express the fitzgerald contraction or orbital speed or whatever equally well with any of the three, but one of them simplifies the fitzgerald contraction somewhat
1 replies
22h16m
I think a key tho in a measurement unit that’s desirable is its relationship to something consistent everywhere in the universe, such that the reference unit is reproducible by anyone. This doesn’t matter much day to day but as a system we should converge to one that anyone anywhere can agree how long a distance may be without a mutually agreed upon calibration but can calibrate without access any specific reference unit. The triple point of water is always what it is, and a colony on mars without easy access to something locked in a room in Paris or whatever can create their own reference measurements from whole cloth and they’ll be the same as the colony at Alpha Centauri now and in 20,000 years.
0 replies
21h12m
yes, even before alpha centauri, a big problem with the kilogram artifact locked in a room in paris was that it keeps changing its mass and nobody knows why or exactly how much or in which direction, although the best estimates are that it's a fair fraction of a part per million by now
agreeing on distances with a faraway colony is actually a considerably easier problem than the kilogram; if we transmit them a radio or laser message, they can measure its length to within parts per billion, and we can do that with 01950s technology, while kibble didn't invent the kibble balance (previously known as the watt balance) until the 01970s
(you do have to worry about redshift: one part per billion of redshift is 300 millimeters per second, so you have to know the relative velocity of alpha centauri to within meters per second to correct for it—and, while that's also the 01950s technology of measuring spectral line frequencies to that precision, that same technology is what allows you to do without the radio message entirely)
transmitting or storing the number "9192631770/299792458" can be done with significantly higher exactitude, of course, and can be done over twenty millennia more easily than transmitting a radio message can
1 replies
19h28m
guilty as charged. it gets worse, though: meters are originally based on the size of the earth, but humboldt's expedition (?) fucked up the measurement and now we're stuck with a meter that's significantly too short
Uhm, a kilometer is supposed to be 1/40000-th of the Earth's meridional (i.e. from South to North poles) circumference. The modern value is 40008km, so the official meter is juuuust about 0.02% shorter than it should be.
0 replies
18h13m
i think it was a ten thousandth of the distance from the north pole to the equator through paris, disregarding the southern hemisphere, which was more difficult to survey. i've been looking for a precise number for how far that distance actually turned out to be, but i haven't been able to find it; i would be delighted if you could!
whether 0.02% sounds ridiculously good or ridiculously bad depends on your frame of reference
https://en.wikipedia.org/wiki/History_of_the_metre#History_o... says that the original mètre des archives in 01799 was machined to within 50μm, which is 0.005%, four times smaller than the error in delambre and méchain's computation. so even at the time that was a pretty large error. since then the measurement uncertainty of the meter has improved by five more orders of magnitude, to about 0.1 part per billion. 0.02% is 200 parts per million, or 200000 parts per billion, which is a lot more than 0.1
0 replies
1d1h
It all gets the job done, no reason to let any of it bother you.
0 replies
20h46m
it wasn't humboldt's expedition https://en.wikipedia.org/wiki/Alexander_von_Humboldt#Spanish... which had nothing to do with the decades-earlier meter-measuring expedition https://en.wikipedia.org/wiki/French_Geodesic_Mission_to_the... (except for being inspired by it) and the contemporary calculations of the paris meridian https://en.wikipedia.org/wiki/History_of_the_metre#M%C3%A8tr...
1 replies
1d1h
0 replies
22h8m
Quantum and their oppositionally defiant exceptions.
4 replies
1d2h
I am ashamed, I misread the room.
3 replies
1d2h
Everything in mission control is typically m/sec, we're not animals :P
1 replies
1d
Statistically, it wouldn't be too surprising if at least one of you was a furry. :)
0 replies
1d
probably a lot of them; every high-tech field is full of furries
also though the humans are animals, not stable configurations of plasma currents in the chromosphere or something
0 replies
1d2h
well i am, which is why unit conversion is difficult for me
3 replies
1d2h
Sound came back later in the video, so I’m pretty sure they just turned the volume way down. The sound was probably very annoying for that period of time, but they actually wanted people to be able to enjoy the beauty of that scene.
1 replies
13h47m
Nope, all audio was straight from the camera, no gain adjustment or muting. Something odd happened with the diaphragm in the mic I think.
0 replies
13h39m
Fascinating, I wouldn’t have expected that!
0 replies
1d2h
thanks for the correction; incorporated
3 replies
17h38m
What a strange way to take a dig at non-metric measurements. The "units" command makes it trivial to get whatever you want:
You have: (G earthmass / earthradius)**.5
You want: mph
* 17693.688
/ 5.6517331e-05
You have: (G earthmass / earthradius)**.5
You want: furlongs / fortnight
* 47560632
/ 2.1025793e-082 replies
14h30m
yes, but why would you want that?
the original title said 'at 17000 mph', and as you can see, that's very significantly low, about 4%:
You have: (G earthmass / earthradius) ** .5 / 17000mph - 1
You want: %
* 4.0805157
1 replies
13h41m
Maybe 17000mph was a bit sloppy of a title on my part. It was a weird orbit, with the burns we were doing.
0 replies
13h38m
naw, 4% is fine, i'm half joking
i'm pretty much a raw beginner with orbital dynamics but my vague idea was that you'd have to ellipticize the orbit by hundreds of kilometers to change the orbital speed by more than a fraction of a percent, and that would be expensive enough that you'd only do it if you had a really good reason
but the only satellites i've ever troubleshot had only extremely limited maneuverability (though i'm not totally sure how much more than that i can say)
27 replies
1d1h
This marks the first time a commercial company has landed a spacecraft on United States soil.
I'm assuming SpaceX doesn't count somehow? Boosters have landed on soil for sure (well, technically on landing pads), but maybe they didn't become spacecraft.
18 replies
1d1h
Those reentered from suborbital trajectories. If reaching space (> 100 km) was necessary, I think even amateur rocket people have achieved that.
14 replies
1d1h
Come on LOL.
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.
6 replies
1d
I mean sure, there's ambiguity around the word "spacecraft". But Falcon 9's booster isn't orbital, its payload is. So it might still be a first for an orbital spacecraft.
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.
3 replies
16h27m
Huh? Did you flunk freshman physics?
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.
1 replies
11h43m
You are correct (aside from the s/ME/M/ typo), but the snark isn't needed.
0 replies
3h35m
No, they are not correct either.
0 replies
3h35m
You're quoting this article, but you're misunderstanding it:
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.
1 replies
19h48m
F9 landing is not trivial, and despite all the comments on this thread trying to back up the claim this is the “first commercial spacecraft to land on US soil” ludicrous.
0 replies
3h33m
I wasn't trying to extend the analogy to saying landing F9 is trivial. But F9 surviving re-entry is fairly trivial, which is the important difference between the two. Once you've survived re-entry and slowed down to terminal velocity, there's not a huge difference between landing from orbital and sub-orbital trajectories. I agree that the way it's phrased is fairly meaningless and reeks of baseball commentary cherry-picking, but surviving from orbit is still a very different milestone than surviving from sub-orbit.
2 replies
23h54m
Umm, no. It's a booster of an orbital rocket, the booster itself is not orbital. Falcon 9 stages super early even compared to other rockets, specifically so the booster can come back before it gains anywhere near a significant fraction of orbital energy.
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.
1 replies
23h22m
How was the spacecraft in this video "more orbital"? Did it reach orbit itself?
0 replies
23h7m
It was a capsule sitting in orbit for a few months waiting for bureaucratic processes before being allowed to come back down.
2 replies
1d
I disagree. Falcon 9 is an orbital booster, but only the second stage goes to orbit. The hard part is surviving re-entry, the first stage only barely requires a heat shield.
Dragon would qualify, except it lands on the ocean, so not "US soil".
1 replies
18h3m
apparently the hard part is getting the control systems and landing legs simultaneously lightweight enough and reliable enough, if i correctly understand spacex's long history of failing to land rockets (which i may not, since all i know is a small sample of what they've published)
agreed about dragon. those fuckers do orbit!
0 replies
1h24m
The hard part for landing a suborbital rocket vertically is that. The hard part of landing anything from orbit is still definitely the re-entry.
0 replies
1d
Falcon 9 boosters are not orbital. The point of first stage booster is to get rocket part of the way to orbit and the second stage gets it into orbit. The boosters don't have the heat shield to return from orbit.
2 replies
21h35m
Then what about Starliner? Here's a video of the landing from OFT-2 [1] two years ago, on the way back from the ISS. It was in orbit and landed on land in New Mexico. And while they are doing this as part of a NASA contract, the spacecraft and mission control were both from Boeing. I don't see how they don't qualify
1 replies
13h20m
Done under government contract. This was the first time a purely commercial effort did it on their own dime.
0 replies
13h0m
Went from founding to shipped flight hardware in 2 years with 45 people. I think the key was the really good coffee machines.
3 replies
1d1h
This capsule was recovered from orbit, SpaceX boosters are not orbital at all and are just falling basically
1 replies
22h23m
I guess the Dragon capsule doesn't count because it lands in water just slightly offshore, lol
0 replies
21h37m
Water is famously not soil.
0 replies
21h50m
To be fair, orbit is also "just falling, basically".
1 replies
22h19m
Others have pointed out why boosters don't count.
But what about Dragon?
0 replies
21h29m
Dragon capsules (as well as all US-based capsules [could be wrong]) splash down in water, so not soil. Soyuz capsules land on soil.
0 replies
23h25m
They should definitely also add an "intact" qualifier. ;-)
0 replies
23h53m
The boosters aren't themselves orbital, and while the Dragon capsules have re-entered several dozen times now, they splashdown in water. I think technically Starliner would better fit the case of a commercial company landing a spacecraft on US soil.
26 replies
1d2h
That's what a several miles per second wind looks like!
The heat is not from the friction, but from the compression of the gasses.
21 replies
1d2h
I often see that claim, but I don't like it.
The implication is that the heating is like when one compresses air in a bicycle pump, the increase in temperature that comes from adiabatic (reversible, isentropic) compression of a gas. And some compression does occur, so there is some necessary heating from that source (as required by the second law).
But entry heating is not reversible. It's fundamentally irreversible, in fact. The gas is going through a shock. Shocks fundamentally cause an increase in entropy as fast gas slams into slow gas over a region whose thickness is on the order of a mean free path of molecules in the gas. And, in fact, the increase in density of gas going through a shock approaches a limit (around 4, IIRC, for air) regardless of the Mach number. So at sufficiently high speed most of the heating is coming from dissipation at the shock (a process akin to friction), over and above the heating implied by adiabatic compression.
15 replies
1d2h
Seems like the gases are getting compressed either way and it's just different ways of wording the same effect. As for it being reversible or not, is it not just a matter of whether the energy was actually transferred somewhere? Like you could technically undo the shock the same as you could depressurise air in a pump no? I don't really know what I'm talking about though, fyi.
10 replies
1d2h
Gas is being compressed, but that doesn't mean the heating is from compression.
There's a gas heater on the market that works by using rapidly moving vanes to induce shock waves in the gas. The outflow has the nearly the same pressure as the inflow, but the gas has been heated, potentially to a temperature higher than could be achieved by resistive heating elements. EDIT: I mistated this; see below for link.
Consider also that once the shock heated air around the reentry vehicle has expanded back to ambient pressure, it will be hotter than it initially was.
6 replies
1d1h
resistive heating elements made of carborundum can heat air to 1625° https://www.kanthal.com/en/products/furnace-products/electri... and molybdenum disilicide to 1800° https://zircarceramics.com/wp-content/uploads/2017/02/Design.... while graphite heating elements can go to 2200° https://apps.dtic.mil/sti/tr/pdf/ADA329681.pdf but not in air. what are these vanes made of?
5 replies
1d
The point is that the shock isn't the air hitting the vanes, it's the air hitting other air.
Similar to re-entry heating: the specific kinetic energy of the returning capsule is many times greater than would be required to melt and vaporize any material. So why do things survive re-entry? Because most of the energy is dissipated in the bow shock, significant distance away from from the capsule, where air gets heated to temperatures higher than the surface of the sun when other air slams into it. The purpose of the heatshield is to protect from radiative heating from the bow shock, not convective heating. Ablative heatshields do not work because ablation consumes energy which removes heat (again, there is sufficient energy going around to ablate the entire craft), but because they place a shade (made of ablated carbon particles) between the bow shock and the craft, which shields it from the radiative heating.
3 replies
1d
The purpose of the heatshield is to protect from radiative heating from the bow shock, not convective heating.
In this case the entry regime was such that convective heating far outweighed radiative heating.
2 replies
1d
i'm interested to hear more about these heaters. do you know what they are called or what they are made of?
1 replies
23h19m
See link in a comment below.
0 replies
23h5m
0 replies
1d
hmm, that's a good point; so if you run coolant through the vanes they can operate without damage while producing temperatures that would vaporize them?
2 replies
1d1h
Do you have a link or company/product name? Sounds fascinating.
1 replies
1d1h
https://coolbrook.com/wp-content/uploads/2023/06/REPRINT-202...
I mistated slightly: the gas is accelerated to supersonic speed then slowed in a diffuser, where shock waves heat it.
0 replies
23h7m
thank you, this is great! it sounds like they're only targeting 1700°, though, which is a temperature that exotic resistive heating elements can reach. it's too bad they didn't include any kind of diagram
3 replies
1d1h
The gasses get so hot they give off a lot of black body radiation. Heat shield is mostly beat up with infrared.
When the gases decompress they'll be a lot cooler, just like your AC.
2 replies
1d1h
I believe for entry from LEO, and particularly for small RVs like this one, convective heating is orders of magnitude higher than radiative heating.
https://ntrs.nasa.gov/api/citations/20140012475/downloads/20... (see slide 7)
1 replies
23h57m
From Slide 7: "Radiation dominates convection at ~11.5km/s for 1m radius • Radiation dominates convection at ~10km/s for 5m radius"
0 replies
23h18m
Since this is reentering from LEO, it's maybe 8km/s (and dropping). And the radius of curvature on the nose of that shield was maybe 20 cm?
3 replies
1d2h
I prefer to say it's the molecules screaming in agony as they are violently compressed and forced to hit each other at speeds they are mostly uncomfortable with.
2 replies
1d2h
A molecular equivalent of a massive, high-gee car pileup on a highway.
(Hope that never actually happens.)
0 replies
23h17m
I see you've never seen people drive in Texas when there's ice on the road.
0 replies
1d1h
Shock wave dynamics are observed in the flow of traffic on sufficiently crowded highways.
https://en.wikibooks.org/wiki/Fundamentals_of_Transportation...
0 replies
1d2h
thank you, this is very illuminating. i'm very weak on thermodynamics
3 replies
1d2h
All those little molecules trying to get out of the way.
2 replies
1d2h
They are screaming, first in infrared, then red, orange, white...
0 replies
1d1h
They're so excited, and they just can't hide it.
0 replies
1d2h
They were not expecting this....
11 replies
1d3h
This is what filming hypersonic plasma with a gopro from a reentry capsule looks like.
For the true space nerds, here is the 27min uncut version. https://www.youtube.com/watch?v=BWxl921rMgM
7 replies
1d2h
Watching this somehow makes the whole MOOSE concept [1] of a person falling from orbit seem a lot more reasonable. It wouldn't be pleasant obviously
2 replies
1d1h
Eventually Red Bull is going to sponsor somebody to do this.
1 replies
1d1h
No, it's going to be some old, rich tech nerd! (eg Alan Eustace, who broke Felix's balloon record shortly after it was set but without anywhere near as mich fanfare)
0 replies
17h10m
The ultimate billionare sport would be basically parachuting from space (MOOSE-style). It would be such a rush. I volunteer Elon for initial testing.
1 replies
1d
Maaaaaaybe. But we did pull like 20g+ on descent, so that's a bit problematic
0 replies
18h5m
you'd have to decelerate several times slower (four gees to be safe, three gees to be gravitron-style 'comfortable'), but that's feasible in an aerodynamic (plasmadynamic?) fashion, even with a relatively low mass-per-unit-area projectile like a person facing forward
0 replies
1d
You kidding? I'd pay to try that. Suck it, Baumgartner!
0 replies
1d2h
this is great! i think you could make it as pleasant as a typical rush-hour trip on the city bus: louder and more dangerous, but with less people, and perhaps roughly as comfortable, at least if you have the kind of rush hour where you are frequently in danger of fainting from the heat
0 replies
1d
Looks identical
0 replies
1d2h
this is so awesome, thank you
also, congratulations. space is hard, and what you've done is harder than reentry
0 replies
1d
Grabbed the wrong link, that's the 5min version.
9 replies
1d3h
Was there a jump cut at the end or was the person collecting the chute really mere steps away from where it landed?
7 replies
1d3h
Jump cut. We helicoptered in, but it took about 20 minutes.
5 replies
1d2h
IDK what your job title is, but 'helicoptered in to collect a recently landed spacecraft from the desert' sounds like an awesome day at work.
2 replies
1d1h
Seriously muddy sneakers tho.
1 replies
1d
I laughed - looks exactly like the "playa stilts" you see after rainfall at Burning Man.
0 replies
22h59m
Reminded me of https://www.youtube.com/watch?v=QrxPuk0JefA
1 replies
1d
I don't really have a job description, I just solve problems.
0 replies
9h58m
That sounds worrying. Maybe they shoot you up next.
Awesome video you created! Looks like there is bad weather over half of the planet though.
0 replies
1d2h
That is still an impressive aim that y'all achieved. Congrats!
0 replies
1d2h
You can tell it was a cut, by the way the person faded into view.
7 replies
1d2h
This footage is amazing. And I love how the microphone just gave up as the plasma formed xD
EDIT: As commenters noted, it fades out so it probably was edited in post.
5 replies
1d2h
But it came back later! Frankly we're all surprised and a little confused how much audio we got while at 500km altitude before reentry.
1 replies
1d2h
It sounds like it indeed was a GoPro, neat! Were you not surprised to get video back, then? What steps were taken? I don't know much about Space Stuff but seems like even with shielding, you would expect off-the-shelf consumer hardware to fail somehow..
0 replies
1d
Heavily modified. But it's the Gopro sensor and board.
1 replies
1d1h
How interesting... the anacoustic zone apparently begins at about 160km altitude.
0 replies
1d1h
What's the maximum voltage in a GoPro? In some ranges of air pressure, if the voltage is sufficiently high a discharge could occur, perhaps shorting out something temporarily.
0 replies
23h18m
maybe a lot of that audio is electromagnetic interference? that's what it sounds like, and audio amplifiers can be pretty sensitive
also, sometimes audio amplifiers oscillate on their own (though i think the single-jfet preamp in an electret mic is unconditionally stable); an amplifier that oscillates in space in a way that physically vibrates the microphone might be damped by air so that you don't notice it when air is present
interestingly, microphone amplifiers oscillating and producing physical vibrations is not a phenomenon restricted to electronic systems: https://en.wikipedia.org/wiki/Otoacoustic_emission
pfdietz seems to be suggesting corona discharge encouraged by the lowered paschen voltage in low vacuum, and of course the negative-resistance characteristic of gas discharges can easily set up a parasitic relaxation oscillator; all you need is some parallel capacitance or series inductance, plus some kind of ballast that quenches the discharge http://tinyurl.com/23dt3d5e http://tinyurl.com/2de5uaog https://www.physics.purdue.edu/demos/display_page.php?item=6...
0 replies
1d2h
I was curious at this point; did the mic actually give up (it was working again later), or was it muted because of lots of noise?
6 replies
1d3h
I find the most crazy thing is not the reentry, but the number of objects (satellites) visible at the beginning of the video.
And maybe the most worrying part is that there is more and more unidentified objects: https://sdup.esoc.esa.int/discosweb/statistics/
Also the number of payload really rised after 2020 (because of spaceX I guess).
1980: less than 1000 objects Today: Almost 10000 objects, including approx. 4000 in LEO only.
2 replies
1d3h
Pretty sure that's just debris from the separation, most likely to end burning up in the atmosphere too.
0 replies
1d2h
If not, their orbits would rapidly decay due to very low ballistic coefficient (mass/area).
0 replies
1d2h
Yeah, that's some dust from the heat shield
1 replies
1d2h
Those little white specs moving from lower left toward upper right? I think that's just tiny pieces of debris dislodged when the RV separated, shining in the sunlight.
0 replies
1d1h
Make sense...still impressive to have x10 more objects floating around in less than half a century.
0 replies
1d2h
Those specks are almost certainly not distant satellites, but very nearby specks of dust and debris caused by the separation process.
One dead giveaway is that they don't appear to be moving in perfectly straight lines. If they were distant, this would imply they were not free-falling but under powered flight, at an implausibly high acceleration.
You can see the same phenomenon in e.g. film footage of Apollo stage separation: https://youtu.be/9DNnZ82Kg3w
6 replies
23h32m
I have a friend who's at Varda. They manufacture space drugs. SPACE DRUGS!!
https://www.healio.com/news/infectious-disease/20240222/hiv-...
5 replies
20h56m
Out of curiosity, what's the benefit of pharmaceuticals manufacturing in space?
Is there a benefit to manufacturing drugs in low gravity environments, or is it more of an experiment to see if it's feasible, in a future where more people might be living in space?
3 replies
19h42m
Perfect crystals. Also, the proof-of-concept drug was ritonavir, and it's nearly impossible to consistently grow large crystals of it on Earth. All of the labs that work with ritonavir are contaminated by a more stable form ("polymorph") that rapidly converts any ritonavir crystals into a less-useful form.
1 replies
16h59m
You just need a crystallographer with a beard in the lab (https://improbable.com/2011/02/09/legend-of-chrystallographe... https://www.science.org/content/article/pure-stupid-luck https://www.chemistryworld.com/opinion/czochralskis-pulley/3...).
More seriously: this was pretty much solved already through improved techniques. I'm generally of the opinion that if you have to send a molecule to space to crystallize it better, you should probably spend your money on other, more terrestrial approaches. I do credit Varda for doing this automatically, rather than on ISS, because launch costs for autonomous vehicles are much more affordable than human space flight.
0 replies
14h33m
It's actually still not solved, you can't grow large ritonavir crystals on Earth.
Ritonavir used as a drug works around the issue. It's produced as dispersed molten droplets inside a matrix of inactive material. Its heated above the melting temperature of ritonavir, so it prevents contamination.
0 replies
18h58m
> All of the labs that work with ritonavir are contaminated by a more stable form ("polymorph") that rapidly converts any ritonavir crystals into a less-useful form.
The incredible case of the disappearing polymorphs: https://en.wikipedia.org/wiki/Disappearing_polymorphs
It's an actual virulent molecule!
0 replies
20h42m
I believe last I read about it, some drugs are formed as crystals, and being in 0g (or free fall if your pedantic) meant the formed crystals were much bigger or easier to actually form, can't remember which, the specific drug is related to HIV medications
5 replies
21h43m
Only a handful of minutes from a position in space where you can see the whole earth to a small spot in the desert of Utah. Where you see the feet of a human walking towards you.
Amazing what is achievable with the tech of today. Space is not that far away after all. Still very odd to see the two scenes described above in a short video on YouTube.
Having the human walk towards the camera has a tremendous effect. It's something everyone can relate to and it puts a great context to all the scenes that are shown in the video before that.
1 replies
21h4m
Just a heads up that the video linked above has been cut, the full length video can be found here: https://www.youtube.com/watch?v=BWxl921rMgM
What you said is still valid though, since the full video is not much longer.
0 replies
19h55m
Yeah sorry, grabbed the wrong link initially.
0 replies
21h3m
If you live in San Francisco you're closer to LEO than you are to Los Angeles.
Probably also helps that 17,000 mph is really freaking fast.
0 replies
17h21m
Yea, that's something we have to explain to folks quite a bit working at/on Varda; space feels further away than it really is because of how inaccessible it has historically been; really due to cost, but also cadence of launch in near equal measures. Now that both of those barriers have fallen with the Falcon 9, and will continue to do so with Starship, that perception of inaccessibility will slowly change...or I hope it does/I'm working really hard (with some decent progress) to make that true.
0 replies
14h52m
You can't see the whole earth (most of one hemisphere) from LEO, only a circle about 1000 km in diameter, which is about the size of Texas or twice the width of Utah. That doesn't stop it being amazing though!
There's also a cut before the person appears, so it could have sat waiting much longer than a few minutes.
4 replies
1d3h
Can anyone explain the random bright flashes at the apex of its velocity?
3 replies
1d2h
Tiny pieces of the heatshield debonding from the craft and interacting with the plasma.
1 replies
1d2h
"...and interacting with the plasma"
That sounds like an exciting day at work. ;-)
0 replies
1d2h
Rapid unscheduled dismantling happening at the molecular level.
In this case, it wasn't really unscheduled.
0 replies
19h3m
Compare the heat shield in the pic here (before launch): https://x.com/VardaSpace/status/1671621386065027072?s=20
To here (after reentry): https://x.com/VardaSpace/status/1760726397889466792?s=20
4 replies
21h28m
Question, that might be obvious to many but not to me: isn't space supposed to be empty? How is the mic picking up noise (= sound) just after detaching from the other module?
1 replies
20h23m
I was confused by the fact that it started off with a little sound, and then there was a crescendo, and then it cut off to silence at about the 3 minute mark ... and then around the 4 minute mark sound ramps back up. Was that artificially muted out because that section would have been too loud?
0 replies
5h53m
From OP:
Nope, all audio was straight from the camera, no gain adjustment or muting. Something odd happened with the diaphragm in the mic I think.
1 replies
21h22m
I'd say vibrations of the capsule which shake the camera, which then shakes the diaphragm/membrane of the microphone, and maybe electromagnetic inferences
0 replies
19h28m
If it's a go pro in an airtight housing, it has that air to make the mic work normally
3 replies
17h48m
Surprising to see another spacecraft at 1:30
1 replies
16h40m
that's the spacecraft that dropped us off!
0 replies
16h40m
oh god I need to change my HN username
0 replies
12h42m
Rocketlab Photon?
3 replies
1d2h
I'm surprised it took only around 2-ish minutes from somewhere above the clouds to on the ground.
1 replies
1d1h
Yeah, I think it would have been nicer if they used wipes or some other more obvious transition when hey cut out bits. Some of the cuts you almost don't notice tricking you into thinking things happens much faster than they really did.
0 replies
1d
Full 27min uncut video here. https://youtu.be/BWxl921rMgM?si=q50ewZw4ARRU-hG0
0 replies
1d1h
There’s a cut at 5:10, after the parachute opens: https://youtu.be/qw4DseiPu7E?si=QZFAnKYfVnQc92TD&t=305
There’s another cut earlier when still outside the atmosphere as well.
3 replies
21h8m
What I found interesting is the sun is actually white in this camera feed instead of the usual yellow we associated with it.
1 replies
21h3m
Yeah, the sun is actually white! It's a big star, after all
https://en.wikipedia.org/wiki/Sun#Sunlight_and_neutrinos
The Sun emits light across the visible spectrum, so its color is white, [...], when viewed from space or when the Sun is high in the sky.
When the Sun is very low in the sky, atmospheric scattering renders the Sun yellow, red, orange, or magenta, and in rare occasions even green or blue.
Despite its typical whiteness [...], some cultures mentally picture the Sun as yellow and some even red; the reasons for this are cultural and exact ones are the subject of debate.
0 replies
18h10m
That last sentence about the color of the sun being cultural is weird to me.
The sun simply looks very different depending on where you are on earth.
Example (from experience/memory): the sun looks very orange/red during a Norwegian winter sunrise for like an hour or so.
Around the equator the sun is up and white within minutes.
0 replies
19h55m
It's a GoPro doing automatic white balance.
2 replies
1d2h
Could video camera be damaged by a direct imaging of Sun?
0 replies
1d1h
Just like from the surface of the Earth. The atmosphere doesn't really diminish the brightness that much.
So, while you should be careful including the sun in a photo from a camera, it really depends on the focal length and aperture of the lens used. Lenses with long focal lengths will create a larger sun image on the sensor leading to greater heating. The camera should automatically shrink the aperture when the sun appears in frame to adjust the brightness, but if it doesn't and the aperture is sufficiently large then you could end up with enough heating on the sensor to damage it. With a very wide-angle lens like the one used for this video, it's not likely to be a problem.
0 replies
17h58m
there are definitely video cameras that can, but a gopro (with, as mnw21cam pointed out, a wide-angle lens) probably isn't one of them—even in space with no air to cool the focal plane
2 replies
1d2h
The mud on those shoes at the end man. Still impressive footage!
0 replies
1d
I was very confused about the shoes. I was watching on low res (bad internet) and I thought it was some sort of weird ghillie suit! Thx
0 replies
1d1h
It's been rainy lately out west, I think. Kayaking in Death Valley!
They needed it.
2 replies
1d
This is the second time Varda's been on my radar in the past year. First time was when their engineer Andrew McCalip livestreamed his replication attempt for LK-99 (using company equipment) just days after the initial announcement [1][2]. I'm not even remotely in the right field, but stuff like this makes me think Varda would be a cool place to work.
[1] https://news.ycombinator.com/item?id=36997821 [2] https://www.tomshardware.com/news/engineer-details-messy-lk-...
1 replies
1d
Hehe, that was me. The hobbies do occasionally get out of control :P
0 replies
23h54m
When the hobbies become indistinguishable from the job. Congrats on the reentry.
1 replies
11h53m
Kenton?
0 replies
17m
Nope, not me.
1 replies
22h39m
Are the points of light when it first separates Starlink/other satellites moving around up there, or stars?
0 replies
21h57m
they could be much smaller and much closer from debris from the craft itself. perspective at that altitude is tricky
1 replies
1d2h
The audio (in both videos) sounds like it was ring modulated. And later, cut out entirely. Is that an attempt to stretch audio that was sampled periodically from another system, or an artifact of the GoPro's own audio circuitry?
0 replies
1d2h
Entirely from the Gopro internal mic
1 replies
1d1h
This is definitely not dropping out of “hyperspace”. Title should be changed.
Very cool video though.
0 replies
1d1h
I mean it definitely looks like it.
1 replies
21h20m
I don’t know if Andrew is still answering, but how does it work with calculations for reentry?
It’s basically ballistic downward, how do you make sure you won’t hit anything on your way down over many layers?
0 replies
19h10m
Eric here from Varda. Short answer: lots of math. But really, that's the job of lots of folks over here, but primarily comes from our GNC and Hypersonic/Analysis teams. Folks like my colleagues Marat Kulakhmetov
1 replies
1d2h
Is the bright body visible from 0:25 to 0:35 the Sun? It looks much brighter already at 4:04.
0 replies
1d2h
The moon!
1 replies
23h35m
Can anyone post a timestamp?
0 replies
22h9m
2:44
1 replies
23h19m
What are the "sparklies"? They look like small particles burning up but it's not clear why they're only luminous so briefly within the frame of the video.
0 replies
18h3m
This answer and the following children answers will answer your question: https://news.ycombinator.com/item?id=39539147
I didn't know what to ctrl+f to find my answer, settled with "sparks" and then "flashes".
0 replies
1d1h
This was incredible to me and I'm not even sure why. I was enthralled.
0 replies
1d3h
So we know what dropping from hyperspace looks like? Area 51 confirmed!!
0 replies
1d1h
So I have a question about the audio at the beginning of the video. How low is LEO and how much atmosphere is there? You know, the whole sci-fi movie trope with lasers making noise in space?
0 replies
1d1h
Immediately before touchdown, the camera rolls slightly before we hear and see it impact. Why is that?
0 replies
1d1h
The experiences of awakening astronauts get when they see Earth for the first time make sense to me now.
0 replies
1d
27min full uncut version. https://youtu.be/BWxl921rMgM?si=9lVkkMBd5pAw2hSv
0 replies
1d
This is some serious Deep tech [1] technology, not your average fully remote SAAS.
0 replies
23h16m
What ITAR restrictions do you have for employment?
0 replies
1d1h
That meringue got toasted!
Pretty neat the way it went from crazy hyperspace to a gentle, peaceful floating in the air!
0 replies
21h59m
What version of Reentry Particle Effect did you use for this KSP install?
0 replies
1d2h
Beautiful, thank you for posting!
I predict new reentry shaders being made for Kerbal Space Program by modders in short order.
0 replies
22h48m
Helldiver reporting for duty!
0 replies
23h18m
"Landing on the beach Do Do Do Do!"
"Peacekeeper" ICBM... the irony
Seeing as the Peacekeeper hasn't killed anyone, the name seems pretty apt.
The US nuclear program is about deterrence after all. Well, after 1945, anyway.
I was just thinking about what the alternatives to nuclear would have been, had it not been created. (Purely hypothetical, as I know it would require a vastly different timeline of scientific discovery to avoid nuclear entirely.)
Would we still have an equivalent war deterrent today without nuclear? What would it look like?
My guess is something biological. My tongue-in-cheek guess would be something zoological (laser sharks anyone? pigeon pirahna hybrids?)
My guess is biological, too.
And in the short-term future, I think synthetic biology will represent an even greater threat than nuclear.
Why? Lethality, ease of manufacture once figured out, mishandling of process or materials, lack of regulation, ethnic/DNA targeting, etc.
Hard to pinpoint origin in the case of bad actors...
The only reason nuclear weapons are easy to pinpoint is because so few actors are capable of making them. If you had one you could load it onto a semi truck, drive into the middle of New York or Moscow and detonate it, with all evidence conveniently destroyed in the blast.
Keep in mind that there are nuclear detection sensors deployed throughout the US and if you tried to roll a nuke-containing semi into New York, there would be a heavily-armed team trying to intercept you[1].
Supposedly[2], they are sensitive enough that it's untenable to transport enough lead around to shield it.
1. https://en.wikipedia.org/wiki/National_Nuclear_Security_Admi...
2. I have no inside info.
Biological has the advantage of not destroying the infrastructure of the place you are attacking nor making it inhabitable for thousands of years. So if you're wanting to take over the land after you remove the pesky opponents currently occupying it, nuclear is a really bad choice. Biological and chemical can be cleaned up and or inoculated against depending on method used.
From what I remember, the US's nuclear weapons make a place uninhabitable in terms of weeks, not years. But, point still noted.
A strategic deterrent needs to be targetable and scalable. Biological and chemical weapons don't have this property. Before nuclear, strategic deterrence meant maintaining a massive standing army and navy. This was very expensive and also difficult to scale due to the logistical footprint, so most countries could not maintain it very long. There is also the issue that the economic cost of strategic deterrence is relatively much higher for smaller countries.
What changed with nuclear is that you could maintain a credible and scalable strategic deterrent indefinitely at a tiny cost compared to maintaining conventional forces at an equivalent level of deterrence effect.
Scalability is a bit of an issue, but a biological weapon like weaponized anthrax or chemical weapon like a powder that converts to 4highly effective nerve gas could conceivably delivered by methods similar to the nuclear triad. Strategic bombers could airdrop them over population centers, and with enough engineering we could probably make ballistic missiles with payloads that disperse such agents in an air burst, using a small amount of explosives to scatter it over an area the size of Manhattan
WW2 showed that strategic deterrence with chemical and biological weapons doesn't work. Both sides feared gas particularly and therefore didn't use war gas on each other (civilians is another matter.) Germany had very potent nerve gasses and had reason to believe the allies did as well, and didn't dare use them. But the threat of these gasses wasn't strong enough to deter the rest of the war.
Weapon designed for use in a war or otherwise some sort of conflict requiring the use of lethal force, which would be the exact opposite of peace, is named peacekeeper
These comments are being obtuse on purpose. Look at the name and look at what the name is on. The name peacekeeper is on a weapon that will only be used in times of no peace. Not a hard thing to see the irony in.
I'm not being obtuse, I think we just have different views on how the world works.
In my view, violence, or hopefully, just the threat of violence, maintains order.
There are certain classes of people where diplomacy and pacifism just isn't going to work.
Again, the post-1945 US nuclear program is about deterrence ("peace through superior firepower"). So, in that perspective, the Peacekeeper's threat of violence... kept the peace.
The US and the Soviet Union/Russia both do not want to use nuclear weapons.
Citation: Self. Was in the nuclear program during the latter days of the Cold War and shortly thereafter.
If you look at the rich history of nuclear near-misses through the cold war, I don't think there's any reason to feel secure in the idea that nuclear deterrence ensures peace. What it does do, is ensures that the consequences of war will be catastrophic, likely civilization-ending.
Which, you know, is the dice we're going to be rolling from now on. Maybe we'll survive the next century, then maybe the next, but in the long term? Humans just don't have that good judgement.
The weapon is used by not being used. It's purpose is to be a threat. It has been in continuous use ever since it entered service.
It is indeed a deadly weapon system. But it is used every second during peacetime too. Every second it is fielded it maintains a situation where the preferable choice of action is to not attack the one fielding it. In other words it is keeping the peace.
You are being obtuse to the fact that this missile's primary and explicit purpose was to be a compelling and credible strategic deterrent. The entire point of building it is was so that it would never need to be used. This is not a contradiction. Strategic deterrence is an effective way of keeping the peace as has been demonstrated throughout history.
The name "peacekeeper" is a formal acknowledgement of its purpose in the military arsenal. It has no other role.
Is it any different to "peacekeepers" being soldiers?
https://en.wikipedia.org/wiki/Si_vis_pacem,_para_bellum
If you want peace, prepare for war.
Or as Roosevelt put it, speak softly and carry a big stick.
Building an incredibly powerful weapon and calling it "Peacekeeper" is meant to strongly imply that we don't plan on using it, but rather, it's symbolic as a preemptive threat against any would-be attackers. Peace is kept by showing that any attack would be retaliated with overwhelming force.
If you can't conceive of some adversary being aggressive if they perceive you as weak, then you don't understand geopolitics or history. So yes, credible deterrence by means of a powerful destructive weapon can prevent war and maintain some level of peace particularly in preventing large scale war between large industrial powers.
What else does maintain peace besides power?
The strong do what they can, the weak suffer what they must. If you want peace prepare for war. Do you think these are just famous slogans or they really do reflect some hard earned wisdom?
There have been many wars since 1945, and also since the development of this so-called "peacekeeper." Its existence is not doing a great job of keeping general peace.
The only thing nuclear weapons seem to do is ensure their owners are always the aggressors in war and not defenders. Nobody wants to attack a country with nuclear weapons, so it enables them to pick and choose which wars to start.
How many did it kill?
I'm not talking about the test. I'm talking about an entire missile system designed to deliver nuclear payloads to anywhere in the world being dubbed "Peacekeeper", but you already knew that.
I'm also talking about the LGM-118 Peacekeeper missile system. It was in service from 1986 to 2005. Did it ever needed to be used in anger or not? During that time did any military attack the nation which fielded it?
If not I would say it lived up to its name.
Americans call their ICBM “peacekeeper”, while renaming Russian ICBM to “Satan”
NATO reporting names use common starting letters for different categories of weapons. For surface-to-surface missiles all begin with the letter S. Most of the names chosen wouldn't raise eyebrows: Sapwood, Sasin, Sibling, Stone... Some of them seem to have an appreciative "cool factor": Skyfall, Saber, Stiletto... But generally there isn't a derogatory theme to these code names. For instance, codenames for fighter jets include Foxhound, Firebird, Fencer, and Felon. Some of these are really cool names that could have been given to western jets by marketting while others seem derogatory. There's not much of a pattern here.
I've always thought the worst thing about ICBM's is the hypocrisy of the name too!
But seriously these names are pretty much random, sometimes 'cool' sometimes not, just sequential NATO designations like Falcon, Felon, etc.
Nothing ironic about it, nukes have made their owning countries impervious to invasion. Peace through superior firepower as they say.
you'd have to be MAD to have it make sense
It literally kept the peace?
"It keeps the peace, in a dominating, intimidating sort of way."
Awesome link. Reminds me that one of my biggest gripes with movies is that when they show meteors (or whatever) entering Earth, it's never at realistic speeds. They're always super slow and floaty, hovering in the sky to menacing effect. Great, that's the artist's choice. But the real thing is so much scarier, like this footage! And it's still a fraction of the speed of an interstellar object.
On movies those are usually very large objects. Very large objects do hoover menacingly for a very long time before they finally appear to fall for a few seconds.
The larger it is, the longer it will stay hoovering and only slowly growing in size.
Nah, even the big ones are shown sauntering through the atmosphere at maybe Mach 3, trailing smoke and flames like lit pitch.
A city-sized asteroid wouldn't be more than a bright dot until the last seconds before entry, and at interstellar speeds it would take about three seconds to go from the vacuum of space to ground impact unless it had a very shallow vector.
At relativistic speeds it would take about 1 millisecond to go from LEO altitude to the ground.
A relativistic asteroid would not be a good time for earth. Apparently according to gpt4 (so big grain of salt), a 1km asteroid going 0.9c is roughly 4.37×10^16 megatons of TNT worth of energy.
that's one of those too big to comprehend type numbers. that's fine when talking about number of atoms, or the distances to another galaxy. trying to have my brain apply that to explosion just immediately goes to BSOD
Yeah same haha - for a slightly more relevant number, if every nuclear weapon yielded 50MT of TNT, the asteroid impact is approx 63 Billion times the entire worlds nuclear arsenal in terms of power.
And that is still impossible to comprehend, so how about this, the Sun's energy output is about 10^10 megatons of tnt per second, so this impact would release 1 million second's worth of the Sun's output, or about 12 days. In other words, it would instantly vaporize the entire planet.
For the ultimate nerd snipe, how far would the light from that explosion be visible?
using what to "see"? naked eye? binocular aided? telescopes?
also, seen by who/what? for the only known living things that could see it, it would be the last thing they did see. so maybe as far away as a couple of inches?
This is in the correct ballpark. But 0.9c is crazy fast. [Expanse spoiler alert]
I love how they use this mechanic for storytelling in "The Expanse". The rebels of the belt threaten earth by slinging rocks at it at really high speed. Seems a very realistic way of interplanetary war. Why not bend some fast moving rocks to your enemy?
I don't know if it's been the first time in fiction where that concept was described but in Heinleins "The Moon is a harsh Mistress" this was what the Moon Colonists did.
Or a grain of TNT
I decided to challenge the glorified-autocorrect machine with some more-manual napkin math, and I get 5.56×10^13 megatons, which is smaller by a factor of ~786x.
That discrepancy is too big to explain just in terms of asteroid composition: Even an impactor of pure Osmium would only be ~12x more energetic.
Here's my work, if anyone wants to check for errors:
Hehe, I too love vacuuming.
No, that's Hoovering. case sensitivity is important /s
Edit: added /s for those unable
I've never seen anyone capitalize googling or astroturfing, though my dictionary seems to want to capitalize Xeroxing.
No one does that. Except perhaps the PR and legal departments of the Hoover company.
I suppose you capitalise aspirin as well.
Hollywood does slow explosions too. Its kind of a funny meta-anachronism when CGI uses the slow firey explosions that I suppose are inherited from the limitations of practical effects using gasoline deflagrations.
YouTube has shown people real big explosions (Beirut, Tianjin, etc) and how vicious they are, but you rarely see a CGI shock wave.
Rockets too, RPGs are fast but movies have them sauntering through the air.
I mean just look at laser beams in sci-fi :)
The other problem with movies showing large meteors is how dim they are. In reality you would be blinded, even lethally burned, before the thing even hit the ground.
the chelyabinsk meteor was super slow and floaty, hovering in the sky to menacing effect (while glowing much brighter than the rising sun): https://youtu.be/gRrdSwhQhY0
however, that's because its trajectory was nearly horizontal rather than nearly vertical, so most of the people who saw it and were injured by it were tens of kilometers away, and it broke apart (exploded really) at 30 km up. it was initially traveling 19 km per second, 2½ times leo orbital speed. if you're traveling 19 km per second vertically instead of horizontally you only have 5 seconds from the von karman line (100km) until you make a crater or a tunguska
3 seconds from visibility to devastation still might be enough for hollywood dramatic flair
https://en.wikipedia.org/wiki/Chelyabinsk_meteor
Imagine if Don't Look Up had tried for a realistic comet impact. It could make a much greater artistic impact, the contrast to the surrealistic spin games up to that point.
Notice the two that impacted at almost exactly the same spot, a few second apart (around 1:00). What precision!
Yeah. To understand why this is quite a flex: nearly no structure survives when they are directly hit with a nuclear weapon. The way hardened structures are designed is that the designers guestimate how big of a boom they have to survive and at what distance. They do this based on your intelligence sources of course.
So let's say your spies are telling you that the enemy can deliver 60 kiloton device with 200m circular error probable (CEP). Then your engineers can calculate how likely is that your bunker/silo will survive that (and can do something like a counter attack.)
And you build the number of silos you think you need based on that calculation. You put a lot of concrete and lot of work literally in the ground based on those numbers. And then suddenly your enemy just improves their guidance system and they drop (figuratively) such a video on you. That tends to cause jitters.
Yeah, that was the first thing that popped into my mind as well when I saw that. Horse shoes and hand grenades, and atomic weapons was what we always joked about being close enough
TIL the shockwave effect so popular in movies the last 20 years is 100% accurate
Here's footage of several MIRVs entering the atmosphere at night: https://youtu.be/3ZM3y5qpMgY?t=68
On a more scientific note, here's a video from the Space Shuttle boosters as they reenter (2005): https://youtu.be/527fb3-UZGo?t=70
On the subject of impressive old missile footage, I recommend the Nike-X program's Sprint interceptor-missile. Not hot glowing plasma on re-entry, but instead going up.
As a short-range interceptor, Sprints were slammed up out of their silos via an explosively-driven piston, then they would ignite and reorient in midair, accelerating at 100g to reach Mach 10. The missile itself couldn't see very much, but would be remotely guided with strong signals from the launch installation.
https://www.youtube.com/watch?v=gSFIkGfbLxs&t=23m37s
https://www.youtube.com/watch?v=6lWDbwmsz9E&t=7m15s
https://www.youtube.com/watch?v=3dl9Ovwmnxw&t=2m44s