'Sokay. We've got a lawn dart, and it's doing more than going up. Now let's look at our friends Spinlaunch and their demo launcher. I'ma use your velocity 'cuz you calculated it and again, lazy. I'm also going to model their demo as a scuba tank because - you guessed it! - lazy. Let's go with an AL80 - 14.2kg, 184mm in diameter, 662mm long. we're going to work backwards from your linear velocity. SCUBALAUNCH = 14.2kg, 184mm dia, 662mm long SCUBALAUNCH LINEAR VELOCITY = 800m/s SCUBALAUNCH RADIUS = 1/3 45m = 15m SCUBALAUNCH ANGULAR VELOCITY = 509 RPM Oops, we already have a problem. We know it's designed to go 450 RPM. We also know that "SpinLaunch’s first suborbital flight utilized about 20% of the accelerator’s full power capacity for the launch" which... I mean they been pretty loosey-goosey with terms so I'll bet they mean it was running at 20% of the critter's speed. SCUBALAUNCH PROBABLE ANGULAR VELOCITY = 108 RPM SCUBALAUNCH CORRECTED LINEAR VELOCITY = 168 m/s SCUBALAUNCH CORRECTED FLIGHT TIME = 17.1 s SCUBALAUNCH CORRECTED ALTITUDE = 1438m = 4717 ft which, again, is aspirational but looks a lot more like what they actually got on video. And i mean, I can't throw a scuba tank most of a mile into the air so kudos. But I don't really think Spinlaunch can, either. Can they spin a scuba tank in a 15m circle at 108 RPM? mmmmmyeah, I'll bet they can. Can they put that 30m circle under something kind-of vacuum-ish? mmmyeah, I'll bet they can. But you can hear the whirring. It's under vacuum-lite at best. But let's tie this poor sonofabitch back into our lawn dart. SCUBALAUNCH LINEAR KINETIC ENERGY = 200kJ SCUBALAUNCH MOMENT OF INERTIA = 3195 kg/m^2 SCUBALAUNCH ROTATIONAL KINETIC ENERGY = 772,000 kJ ...this is getting foreboding. That's 215 kW/h. We'll bleed off our pathetic 200kJ and be left with... about the same. We're going to swap our 3195 kg/m^2 moment of inertia for...much less.. NEW SCUBALAUNCH MOMENT OF INERTIA = 0.548 kg/m^2 SCUBALAUNCH SUICIDAL URGE = 8844 Hz Now. this is about where I argue, often ad nauseum, that the model is broken. 214kW/h is a lot of energy to put into a scuba tank. 15m is a hell of a lever arm. But there is no way in hell you're going to get a 9kHz flat spin out of a scuba tank. Ever. Under any natural, normal circumstances. But you're also not going to get zero. Conservation of angular momentum means the lion's share of energy you're pumping into the system stays with you. And it does so in an inconvenient form. Never mind any counterweight you may have, you're pouring the majority of your energy into you, not your launcher and you don't have a convenient way to deal with it. Worse than that you inherit it all at once when you fling your scuba tank into space. You can't get rid of it easily, either. I mean, you could keep your scuba tank from rotating with a linkage. You would then turn it into a cocktail shaker, unfortunately, and shaking your cocktail at 107 cycles per second (never mind 450) is going to be bad for your cargo ("jerk"). But Isaac won't be cheated - the conversion between one kind of motion and another conserves momentum and there is much in this system.
I ran the numbers for Spinlaunch's actual system. This is left as an exercise for the student. What you need to know is it's at a 45m arm, it weighs 11,200 kg, it's 25 feet long and prolly 3-4 feet in diameter. It's "suicidal urge" is gobsmacking. And again. Those aren't real numbers. But there AREN'T ANY REAL NUMBERS AROUND SPINLAUNCH. In order to get to that math you're spinning a pair of orcas around a 45m circle at 450 rpm and then flinging them into the air at Mach 6. I mean, c'mon. Presume you build this thing out of rainbows and hope, dumb-ass dynamics is still slapping you down. A half-gram USB-C connector under 10,000g weighs this: Design for that. Go ahead. Design for it in not one axis, not two axes, but the transition between those two axes. Also tell me you're going to aerodynamically stabilize a two-body problem with this thing. I don't know what kinda yaw is recoverable at transsonic speeds but I'll bet those are heroic calculations, too. And it kinda feels like this is more math than has ever been done around Spinlaunch.
so holy shit y'all - the accepted rotational velocity of a frisbee is like 2300 RPM - the accepted rotational velocity of a discus is like 400 RPM - the accepted rotational velocity of a clay pigeon is 2-3000 RPM So while I'm keenly uncomfortable with the idea of a lawn dart spinning through the sky at 146 Hz is 8700 RPM, I'm 100% A-OK with a frisbee doing 2300. So... maybe the difference between the lawn dart's suicidal urge and the lawn dart's reasonable behavior is the aerodynamics of the lawn dart. This does not portend well for the rest of the math.
I remember when they were trying to put enormous flywheels in the floor of public buses, which would be the source of motive power. Electromagnets under the ground at each stop were to recharge the spin of the flywheel. (Short version.) There was much concern expressed about the safety of an enormous piece of steel under the floorboards spinning at thousands of RPMs, and what could happen to the passengers in the event of a hardware failure or accident. I seem to remember the were going to address the problem with some sort of graphite flywheel that would basically explode into a giant ball of harmless thread in the event the flywheel failed for any reason. Spinning wheel, WHOOMPF, flywheel chamber full of graphite thread. Now... hear me out here... if the throwing arm in the SpinLaunch design is DESIGNED to explode into a cloud of graphite threads immediately upon release of the projectile.... does that burn off the energy left in the system after the projectile exits the building? Could that be a design feature to address some of the issues left behind once the launch happens? Ok, yeah, it's a stupid thought experiment. But then so is SpinLaunch and it EXISTS. I'd like to at least think someone in one of those rooms has wondered what happens to the arm once it releases...? Someone? Anyone...? Hello? Is this thing on...?
Lol yeah the gyrobus and its lesser-known younger brother, the General Electric Battle Top. Here's the problem: GE's clever idea was to dissipate 1.5 tons spinning at 10,000 RPM through explosive disintegration. That's 373 kJ of bad news. A couple pounds of TNT is 4200 kJ worth of bad news so converting your spinning war top of doom into explosive force, without conversion, is a quarter stick of dynamite. More or less. Work with me here. Spinlaunch, on the other hand, is at about 800,000 kJ assuming the arm that's flinging it has no mass. Assume we're just talking about the counterbalance - we get to dissipate the energy of one of these in our hypercentrifuge every time we fire it up. Again, assuming unicorns and rainbows, massless masses, perfect conversion, la la la la la. They'll want to move the office methinks.
Funny, I didn't even know about the GyroBus! The one I was thinking of was in the 2000's, and I can't find a link to it any more. I think the City of Seattle was looking into them, when I was with the Pioneer Square Community Association. Seems like we saw a presentation on this possible technology being used in Seattle transit buses. Google told me about this older Williams Racing project which used a flywheel as a power-assist in traditional ICE-powered vehicles, too:
On paper? It would. From conservation of (angular) momentum, it'd be a cloud of slower-moving (spinning) particles colliding with the walls of the chamber. From conservation of energy, it'd dissipate in a plethora of ways, but IMO mostly increase in temperature. Depending on the amount of energy to dissipate, if it were made from carbon like in your example, you might end up with friction lightning creating stuff like buckyballs, but mostly chain (=C=C=C=) or cyclic (same, but connect beginning with end) allotropes. Now, if you're asking if this is at all practical or doable...Now... hear me out here... if the throwing arm in the SpinLaunch design is DESIGNED to explode into a cloud of graphite threads immediately upon release of the projectile.... does that burn off the energy left in the system after the projectile exits the building? Could that be a design feature to address some of the issues left behind once the launch happens?
We'll use Tosser to accelerate carbon and make our own nanotubes, dammit! I even know how to get all the carbon we'd need for free: adopt legions of christian children, convince them to act naughty, collect the coal from their stockings. Use said legions as minions. We may be past Bond, but I can still turn it into Johnny English.
Just got off the phone with marketing, here are our two strongest slogan options: JAMES Dissociate." or MOLECULAR Bond." I think maybe the second, the first one maybe makes it sound like our company is destructive or bad."The name's Dissociate...
"It's Bond...
Yup, basically the same company. Watching that gud ol' Texasboi talk a lil' shit brought a tear to my smiling eye. It's unironically called "Not a Flamethrower" and is a piss-poor flamethrower. Closer to a butane torch, really. It feels really bad to churn out all this satirical content, only to be vastly, repeatedly outdone by Master Musk. But I'm busy. Tomorrow I am releasing my self-driving car software update and Donald Trump's healthcare plan.