Btw, the reaction wheels are for attitude control of the missile. Oops, I mean launch vehicle*! Duh. Sorry, I was wiped last night. The language that they've developed reminds me of how a fascist hijacks political language. "Highly iterative design process" is probably my favorite phrase, substituted for "every design so far has failed, and failed quickly". I wonder if jargon and framing is something they're coached on or if it's just the usual cultural business rot of the VC world? Maybe both. I still can't figure out what payload SpinLaunch could hope to carry. It's seriously like "maybe we'll get lucky this time with a GoPro". Maybe Bezos is good for 10k g's? Let's try
My god I didn't even consider that. So in other words in the middle of all this bullshit they intend to... deploy their guidance system. While flipping from 10,000g lateral to zero g vertical they're going to spool up, spin out and control some goddamn FLYWHEELS to keep the thing from turning into confetti. That might just be worse than the fucking airlock, which I've been obsessing over since last night. 'cuz if their gadget is 20 feet long, and their airlock is 40 feet long just for safety's sake, and they're flinging the fucker out at Mach 6 (at sea level, rather than 1mbar), they have 30 microseconds to get the first door completely closed and the second door completely open. And they need to do it in a non-turbulent, symmetrical fashion. Just for comparison's sake, I've been learning a thing or two about EtherCAT, which is a machine control protocol that lives on Ethernet but below the TCP/IP stack... because TCP/IP is too slow. It's kind of like token ring, in that the frame goes from the controller to all the devices on the ring and they add and subtract instruction sets from the frame to make things as quick as possible. EtherCAT is quick, and it's becoming the dominant protocol for machine control because it's also cheap. EtherCAT? gets done what it needs to get done in 500 microseconds. Assume the door is the size of a pizza box. Assume it's double-sided. I need one to close (both sides) in 15 microseconds and then I need the other to open (both sides) in 15 microseconds. Let's call it two feet - the actual creature needs to be bigger, but I like the pizza box. I need that pizza box to close one foot in 1/15e-6 seconds - in other words, my door needs to slam shut at 67,000 feet per second. Now - you may shudder to think that this is a lot of performance to expect from, say, an explosive sledge. You're going to have to generate a lot of gas in a lot of hurry in order to make a mechanical object go from zero to 47,000mph. Not to worry, though - not only is that only 0.0007C, or a minuscule fraction of the speed of light, it's also nearly double the burn rate of C4, a good 60% faster than HMX and 50% faster than what wikipedia tells me is the fastest explosive we've ever developed so no worries, friend, if we tried to motivate this fukka with explosives the burn front wouldn't even be halfway through the charge before it was too late so we'll have to think of something else. As demonstrated, a capacitor BARELY BENDS OVER in 10,000gs, no worries. How much you think their reaction wheels weigh?Btw, the reaction wheels are for attitude control of the missile.
Maybe Bezos is good for 10k g's? Let's try
Ah yes, the interlock doors. Arguably the least impressive demo so far. We are informed they "basically close 95% of the way within 30 ms", which is about 2 frames of 60 fps YouTube video. It looks like this is actually kinda correct, but the thing is still flopping around, reverberating and unsealed, for another 100 ms or so. They will have the advantage of atmosphere pushing down on it when there's an actual pressure differential, to be fair. If they install it correctly. If I (generously) assume a 20 meter length between interlocks, and Mach 6, 6 * 343 m/s ~ 2000 m/s, I end up getting a transit time of 10 ms for the ballistic. So at this stage of development, yep, the doors will be open at the same time, for the majority of the time they're open. Here's one major overarching issue: When you instantaneously expose a volume at vacuum to a volume at pressure, you should treat it like a shock, using fluid mechanics. I think they are making a major mistake in thinking that the tunnel length is long enough that the atmosphere, presumably traveling at mach 1, won't have time to reach the chamber in 30 ms. Shocks can propagate well above the speed of sound, indeed, some shocks are of course caused by a bulk/fluid flow traveling faster than the sound speed. I'm not sure about this instance, I'm hoping to find some time later today to do the math. OH, not to mention, the sound speed is much higher in a vacuum. None of that's actually not the real problem, though. The problem is that shocks are non-linear. They could have a day of successful launches, and then the next day, a 7 mph cross-breeze seeds a micro-instability across the outer interlock that balloons into a disturbance that destroys the entire facility. But if you're intent on gambling with the butterfly effect (no tag! hah)? You're gonna want your geometry as symmetric as possible, like a perfectly cylindrical tunnel, in this case, and I just... I dunno. They might not know that. Should we mail in weekly suggestion letters? (no) This was so funny, because he goes "it's just a bit of mass held onto the board by, y'know, steel", and I'm stuck wondering if they fucking welded components onto a circuit board, or the guy doesn't know that solder is made of tin and lead. Whatever. I can assure you that the reaction wheels weigh both too much and not enough, depending on which problem you're talking about. Both options of "slamming the counterweight into an armored wall inside a vacuum chamber" and "re-opening the interlock doors for the counterweight ~ 100 ms later" have had me in stitches multiple times over the last few months. They're doomed. And they know it. It's their grift.a capacitor BARELY BENDS OVER in 10,000gs
loool 343 m/s is Mach 1. We're at Mach 6, bitch, which at the New Mexico Space Port, elevation 1500m, is 2000 m/s more or less. The Wired article says "nearly 5,000 mph" which would be 2200 m/s. Let's assume a 20 meter length because it's fun and it makes the math easy. we're going to traverse that distance, nose to nose, in ten milliseconds. That said same Wired article says "about 25 feet long" or 7.6 meters. So now we're traversing 13 meters in six and a half milliseconds, divide by two because you want one open not two, you're at 3.25 milliseconds. I'll say this - I was five fingers of bourbon down and off by two factors of ten, you're a goddamn rocket scientist and left off five machs. Or actually you didn't. But you said km/sec when you meant m/sec and you're still a rocket scientist so nyah nyah. So okay. We gotta go a foot in one and a half millisecond, which sucks a lot less than a foot in fifteen microseconds. We're no longer racing HMX we just need it to produce exhaust gas roughly a tenth as fast as it burns which is the sort of fluid mechanics I'd say model, don't calculate because you will make an Ass out of U and Me. And I say that having been doing some peculiar consulting on the side. Obviously this is going to be a 100% laminar environment because the air, upon seeing that door open, is gonna go "whoa, holy shit they said 'yeet'" and get the fuck out of the way.The problem is that shocks are non-linear.
Oh shit, sorry, 2,000 km/s is SpinLaunch II, when we need to start considering relativistic effects. Investors love it. But thanks, I edited my above comment, I do typically work in the thousands of km/s regime, with ~ 100 eV electrons, and bluk flows of ~ 500 km/s. Yup, even more incriminating than the aversion to explaining where their funding is coming from is indeed the lack of showcasing any modeling results. They don't even say that they've used any fluid models whatsoever. I think this could be an engineers only project. There might not be a single physics PhD floating around the company. And I wonder, after this thing goes tits up, if ex-employees will want to put it on their resume. How many of the higher-ups do you think truly believe this is possible? "Forced entry, re-imagined" is the most American thing I've heard in at least a couple weeks, thanks for that.
Hey man, as a low achieving engineer even I can see the holes in this, It's a yes-man-only project because they've gotta keep this going until the next scheme gets funded.
The only thing funnier than an "engineers only" project is a "physicists only" project. A bunch of pasty nerds writing Python routines to turn a wrench using a Raspberry Pi and 80/20 t-bars, consulting several Wrench Turning Theory textbooks. But yeah 'bl00 really blew the roof off of any doubts that this is anything but a VC scam with the links in this thread. Stick it to 'em, SpinLaunch! And then, maybe (more) jail time. But doing time won't bring the money back :).
On second thought, you could totally do this by hiring engineers to each 'own' some small component and yelling at them if they look at anything else or the system as a whole.
I dunno, man. The compartmentalization on this is gonna run into serious issues no matter how small you chop it. - We need a kinetic object to do 2200m/s in a 250m radius in a vacuum and then release - We need a 250m radius of vacuum - we need a 2200m/s release - we need 450rpm out of a 250m radius I mean, the Air Force kinda noped out of launching at hypersonic speeds. Of their two attempts, one was a near disaster and the other was a catastrophe. And that was at 80,000 feet where all they had to do was let go. Yeah, you've got stages on rockets but up until recently, doctrine was "throw the bottom one away." I'd have a hard time writing an RFQ for any part of this project, no matter how compartmentalized. Each aspect has some gonzo shit in it like "I need a stadium's worth of hard vacuum" or "I need to release thirteen oil tankers' worth of mass".
Dude I'm not willing to believe there's even any physics majors involved. I like how they spent five or six minutes talking about the magic vacuum pump that works in the regime they're absolutely never going to hit. After they spent five or six minutes talking about how mild steel outgasses which fucks you over when you're trying to draw a really hard vacuum so isn't it nice that they built everything out of mild steel because they totally never have to worry about a vacuum that hard. They just installed the pump as a conversation piece. I think if you put Adam and Jamie on this they'd probably call in an expert who would tell them to stop. ALUMINUM: 660 c SKIN TEMP OF THE SPRINT MISSILE, WHICH FORMED A PLASMA AT LAUNCH: 3,430 c Assume their lawn dart survives the hard luck of actually being released. Aluminum ignites at 2000c. The thing is a damn match the minute it hits air even if everything goes perfectly.
What is a nose cone with good heat conduction fixing? Making sure the inside cooks too, because they never made any mention of heat capacity or dissipation.
Based on my assumption that their renderings are to scale, the distance between airlocks looks like about 10 m to me in the 1/3 scale system. So I'm guessing that they'll be a 30 m in the full scale? Not sure about the projectile though. Is that 3 m also 1/3 scale? Because it matter a lot, since the doors can't close until the projectile is clear of door 1, which makes the effective distance one projectile length shorter than the full distance between the doors. That 30% means a lot when your tolerance is already a bit tight for comfort.
I dunno about the scalings, but no worries, "comfort" isn't really on the table, here.
I'm more struggling with the design of the vacuum chamber than all the other things (or at least as much, I guess). The model has a max distance of 15 m from the central axis to the edge, and if I'm not mistaken, they didn't run the big test at full vacuum, though I don't think they said what it was. The total force on the structure will scale with the square of the length, so at 45 m, it's 9x the force, while also having 3x the length in which there can be no internal supports--the max deflection in the middle is going to get saggy. Maybe they're going to put buttresses on the outside like a gothic cathedral? That could be feasible, right?
That's because you have some passing experience with vacuum and centrifuges. You can roll it around in your mouth. I, on the other hand, have some passing experience with materials science and this ...just breaks everything. Breaks it all to shit. The fundamental basis of this whole shitshow is A) a seatbelt capable of holding its own against at full thrust and B) a release mechanism capable of letting go of without setting off a supernova.
HOLLLLLLLLUPAMINNIT "So... that means... that the tether... at the tip... is going to need... to be able to support... one hundred THOUSAND metric tons. Or... one hundred MILLION kilograms. To put that in context, a FULLYloaded. FalconNine. Weighs about ZERO point five five... MILLION kilograms. So. This tether. Is going to need to support. The equivalent weight. Of one hundred and EIGHTY TWO falcon nines. Spinlaunch, payload to orbit: 200kg Falcon 9, payload to orbit: 22,800kg "One hundret. And EIGHTY TWO. FalconNines" payload to orbit: 4,150 METRIC TONS Now - energy is neither created nor destroyed, right? But first stage on a Falcon 9 is two minutes and change. This dumb thing takes like an hour to spin up. It seems to me that they're mostly using a lot of energy to create forces they'd really rather not deal with, and as a cherry on top they generate enough KE to push a Sputnik or two into LEO (with the help of a 20 metric ton rocket). How can you get to and "200kg payload" and not go "...where the fuck did all that energy go"
Also fukkit intermediate modulus carbon fiber is 800-1000 ksi. 1 psi is 6895 newtons per square meter. 1 ksi is 6,895,000 newtons per square meter. is 689 newtons per square cm. Is 155lb per square cm. Yield strength of mild steel is around 50 ksi, so a 1 square cm bar of mild steel is gonna yield at a little under 8,000 lbs. 1 square cm of aligned carbon fiber is gonna be able to pick up a fully-loaded M1A1 Abrams tank. You shouldn't tho. "One. Hundred MILLION kilograms" is 981 meganewtons. To support that, at yield, with carbon fiber is 0.2 square meters, or a round rod half a meter in diameter. Solid. No flaws. At yield. Where its elongation is 1.75% so your lawn dart is gonna be between 50 and 80cm closer to the inside of your can at the end of your process than at the beginning. I'm trained that carbon fiber actually kinda sucks more than you think from an engineering standpoint because you have to build it into a mat to do anything useful with it, and then you can't test it, but fuckin' hell the shit's tough in tension. It's just those places where it isn't in tension that you're in a world of hurt. Hmm. I got some carbon fiber printer filament. Maybe I should look into doing something with it.
The world of ice hockey the last 20 years has seen a dramatic shift from wood sticks to carbon fiber. Carbon fiber is superior in all but 2 ways. First, sticks used to cost $20-30. Now they cost $200-300. More importantly, whereas wood would splinter or crack, carbon fiber sticks are highly prone to catastrophic failure. They just explode sometimes. This happens because they get small nicks in them due to skates, pucks, ice, whatever. Then when you load the shit out of it, that tensile strength becomes tear strength and that’s a whole ‘nuther ball game. Obviously industrial applications will have different quality materials, but it’s still one more thing to fear.
When carbon fiber first hit the scene, Formula One built like every single part they could out of it. Then one of the Ferrari(?) cars bumped into someone else in like '91 and the thing shattered like a champagne flute, leaving the driver (and the motor, and the transmission, and the tires, and the fuel tank) bouncing around on the track like a craps hand. FIA decided that maybe the monocoque should be something that doesn't turn into kibble under force. I learned that the thing that keeps carbon fiber and aramid composites out of mainstream usage is the inability to non-destructively test it. At the time, airlines were busily swapping carbon fiber 777 components out for aluminum ones because while the aluminum parts were heavier, you could actually magnaflux them and see if they needed replacement, whereas the carbon fiber stuff flies X many hours and is grounded forever. This later became an issue for the Air Force in Iraq. I didn't buy a carbon fiber frame for my LA bike so hard. As I told my friends, I've only been hit by a car three times and carbon fiber frames can just f'n shatter on you. Which is not what you want to deal with when you need to run Schwalbe Marathons just to keep the flats under two a month.
Thanks, I now have a new fear of carbon fiber. Just checked and thankfully my recently acquired bike is made out of aluminium. I’m also now morbidly curious what might happen to the i3 a few years down the line, as it has both a shit ton of carbon fiber and zero bolts.
Archetypal composite design in luxury vehicle is "make the non-structural stuff out of carbon fiber." It saves you weight, it gives you bragging rights, and it'll never be a problem. A carbon fiber component experiencing zero stress or strain is a new carbon fiber component for the sum total of its projected life. Aside from environmental damage, it will behave exactly the same in a crash twenty years from now as it will fresh off the assembly line. You start carrying math overhead when you put it somewhere structural. Bike frames... crack or they don't, and they ride spectacularly until they do. Generally the people who buy carbon fiber framed bikes don't do it by accident, and they know in the back of their head that mmmmaybe that thing is just not gonna come back from a crack-up. Formula One doesn't let you do carbon fiber structure without the safety aspects being non-carbon-fiber. It may fail? It may fail spectacularly but it won't do so in a way that threatens anyone's life. Motorsport learned that lesson early and often, you don't want to rely on components that will let you down because of something you thought was fine six weeks ago. Here's a thing to keep in mind about carbon fiber - it only absorbs energy so long as it's intact. It ceases to be a part of your crash protection portfolio the minute you exceed its yield strength. As a result, there's little incentive for anyone outside of high performance aerospace to use it in a life safety aspect. Aluminum? Steel? Once you push that stuff past yield it absorbs energy as it yields in a nice, calculable fashion. You can make a "crumple zone" out of metal but a "crumple zone" out of composite might as well be a pile of wine goblets. Push it past its yield and it's cracked eggshells. Which is a long way of saying there's very little in your life that relies on carbon fiber. As I said, even United Airlines got sick of (zero stress) carbon fiber body panels because while the plane is still flyable if a panel shreds at take-off, it's a bad look and with an aluminum hatch panel, you can check wear with a spray bottle and a UV lamp. With a carbon fiber panel you throw it away once it's over a certain number of hours, the end.
Re: your assessment of carbon fiber on luxury cars: I have a Polestar, and it had, for about a week after I bought it, a carbon fiber splitter. One rough bump and it was toast. And cost like 2 grand to get replaced…if I were to do the labor myself. Hence no splitter since week one, since I doubt the next one would last much longer.
What about nicks from the shrapnel of exploded counterbalances? Ohsmall nicks in them due to skates, pucks, ice, whatever
whatever
That's absolutely another major concern. I can't tell if they've designed their centrifuge to also provide structural support, such that I guess only an outer sleeve of the thing is able to rotate. Because, strangely, we're not afforded a view inside the latest build. And if I were there, in person, I'm not getting anywhere near that thing when it's running. So they're like "Hey we can pump down really quick, it's only a rough vacuum". Well, guess what the pressure differential is between 760 Torr and 1E-7 Torr vs. 760 Torr and 1E-3 Torr? Just about 760 Torr, for both. You've got 1 atmosphere trying to implode the thing (love the music). Yeah, the thing will have to live in a web of buttressed supports outside of it. Ideally, you want to cut a vacuum chamber from a single hunk of steel. There's not a forge in the world that has a 45 m radius capability, I just checked. ~15 m seems to be the current record. Not even close. So you'll unavoidably have welding joints in the chamber walls, and you'll have to pass through resonances with chamber vibration modes as the centrifuge spins up or down, with atmosphere pushing in from all sides. Cool, seems fine. Ideally, you'd want the walls to be thicc af, but... how do you weld something super thick together? Genuinely asking. Surely the steel you're fusing together only extends maybe 1/4" or 1/2" into the steel, right? Ladies and gents, I present to you - The Theranos of the space industry.
Dude. 5:33. Whizzy spinny arm. Watch the sun. They shot that shit timelapse They aren't even in the regime of approximation here. They straight up welded up a beer can, got a motor spinning, and then broke the shit out of it. Probably when they let their load go in an insufficiently synchronized fashion and smashed the bearing first one direction and then the other. Does it really matter? They pretty much need it to be vacuum from launch to the Karman Line or else they're fucked. There's no aspect of their design that indicates they've even done wind tunnel tests. They haven't so much as watched a redneck sandcasting aluminum with a propane torch. "Mach 6" is a phrase for them, not a fluid regime. The thing that blows my mind about that video is the only stuff that we didn't call out a year ago is stuff that is actually worse.
Thanks, I gave up after a while of scrubbing through the vid. Blink and ya miss it, eh? So, no support along the chamber axis of symmetry, yet. LOL Hey, here's another entire thing we haven't ragged on yet: The orbit!! You get one orbit per facility. But you can steer a first stage rocket quite a few degrees by gimbaling the engine to one side. And now I'm in stitches trying to imagine attempting to steer a spunlaunch with little thrusters in the lower atmosphere. I'm sure they'll target geosynchronous orbit, since that'd be the most in-demand. But, like you said, who cares? It doesn't matter. It really doesn't. Yeah I was cruising that first thread from 900-odd days ago and feeling like a smug bastard. It's good that this place is pseudonymous because these are the types of companies that'll go after you for "slander", I'm sure.5:33
The thing that blows my mind about that video is the only stuff that we didn't call out a year ago is stuff that is actually worse.
Oh god. You're right. You're putting it in that spot, that spot right there, that's the spot you're putting it in. Theoretically second-stage is a full-on rocket (so, like I said last time, why bother with the fuckin' tilt-a-whirl) so you can do rockety stuff with that stage, but this is a bunch of people who flew their one and only drone into the ground in 2015. That said, I don't think it will get to geosync, dude. They're claiming 200 kg "to orbit" but you know that's LEO. That means they're prolly like 70kg to GTO. What the fuck do you do with that? Their entire embarrassing website makes much of cubesats but really - what the fuck do you do with cubesats other than make your community college proud?Hey, here's another entire thing we haven't ragged on yet: The orbit!! You get one orbit per facility.
btw everyone, GTO is geosynchronous transfer orbit, but if you don't know LEO, delete your account. For sure, the second stage could (very theoretically, after 182 Falcon 9's) perform some corrections, but the changes would have to be comparatively minor. Maybe the best way I can explain the mechanics simply is to point out that the most efficient orbital inclination corrections are performed near apogee, after orbit has already been achieved, and the spunlunch first stage does not even make it to LEO orbit with YOUR 182 FALCON 9 MOM!!! onboard. Presuming you couldn't steer the "first stage" spunL equivalent. (you can't; your mom) Unless they build a luncher near the equator? Best of luck with the 10k g's compliant gimbal system or any other scheme whatsoever to park longitudinally in GEO without roving +/- 30 degrees of latitude every orbit or two or so. Now, imagine the military contracting SpinRanch to put something in low latitude LEO. That's all, that's this paragraph, I hope you enjoyed it. Thank you. Time for minor NASA sacrilege. There is a case to be made against the current paradigm, I will confess. Many things could benefit from serious miniaturization. But many things are very difficult to miniaturize further. Many things should just be shot up into space with way less testing, b/c diminishing returns. Sadly, institutional reputation prevents a bit of progress, for now, cubesats and microsats aside (if only relatively). Everything's all over the board, but the idea that any scientific, military, comms, seriously ANYfucking type of payload can be both miniaturized and 10k g's hardened, and the SpinLaugh scheme would make up for for the hit$ you'd be taking is so fucking hilarious that this is legitimately embarrassing for the current culture of American capitalism's distrust of expertise. There was even a small part of me that was like "wow, this almost kinda diminishes from the respectable successes of the SpaceX business model", but I just cut off both my baby toes, and I'm feeling a lot better. #subsideezNUTSwhat the fuck do you do with cubesats other than make your community college proud?
It isn't clear to me that the reaction wheels are for the launch vehicle and not an attempt to show the hater's that the second stage rocket will survive the launch. I'm 99% sure in their videos they're just flinging this dart out with no attitude control and letting the tail fins and heavy nose keep it from tumbling. At 1:58 it exits the tube pointing about 20 deg from straight in the direction of centrifuge rotation. And in the next 5 seconds looks like it pitches back almost the same amount in the other direction. I have developed no intuition for aerodynamic forces at mach speeds but I wonder if different things happen when you hit atmosphere at 20 deg of pitch at mach 6 instead of 1.6 🤔. I also love how he talks for a couple minutes about C_D improving between mach 1.6 and 6 while completely ignoring the small ^2 floating next to velocity. Also ignoring that C_D for a dart shaped body only applies when it's not sideways.
I think based on the discussion here it's unclear what the reaction wheels are for. I also think it's clear that they're very proud of making one. They themselves might not know what it's for. They will never breach Mach 1. They will never achieve a vacuum thin enough to do so, they will never achieve a rotational velocity fast enough to do so, thus they will never have to address the creation of a shockwave in their chamber, which is good, because it would be dramatic.
Oh god I'd forgotten. "You would, though, if it were playing" Just a gentle reminder - basic rotational mechanics analysis on this nightmare has something like 99% of the energy of the system going into rotation, not displacement. No matter how you build it, it's Physics 101 impossible.