a thoughtful web.
Good ideas and conversation. No ads, no tracking.   Login or Take a Tour!
comment by kleinbl00

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.

    The problem is that shocks are non-linear.

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.





am_Unition  ·  834 days ago  ·  link  ·  

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.

ThurberMingus  ·  830 days ago  ·  link  ·  

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.

am_Unition  ·  830 days ago  ·  link  ·  

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 :).

ThurberMingus  ·  829 days ago  ·  link  ·  

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.

kleinbl00  ·  829 days ago  ·  link  ·  

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".

ThurberMingus  ·  829 days ago  ·  link  ·  

...Quit worrying about the large scale system, that's not your job. Just parcel out the 33m demo system...

kleinbl00  ·  829 days ago  ·  link  ·  

thermos to 1000 ft

kleinbl00  ·  834 days ago  ·  link  ·  

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.

ThurberMingus  ·  829 days ago  ·  link  ·  

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.

kleinbl00  ·  829 days ago  ·  link  ·  

So in pyrotechnics, you use aluminum for this:

Copper isn't particularly interesting unless it's a salt, so I don't even have a good joke for that one.