In the middle of a global pandemic, a ragtag
group of welders, heavy machine operators and builders were brought together. They were given plans for a mysterious structure. With little information on what exactly they
were building, their only clue was scrawled across the top of their plans. Spinlaunch. A space catapult. In this exclusive, behind the scenes documentary,
I talked to the people behind this new innovative company. Spinlaunch is attempting to subvert a problem
that plagues the space industry, the rocket equation. The rocket equation has been the tyrant engineers
have feuded with from the dawn of the space age. A simple equation that describes how much
fuel a rocket needs to carry a payload to its destination. The tyranny of this equation, is that the
fuel needed to deliver that payload is a payload itself. A compounding problem that makes rockets more
fuel than rocket, Typical rockets are more than 90% percent
fuel. Spinlaunch is trying to change that paradigm,
by imparting as much velocity as possible to the payload on the ground, eliminating
as much fuel as possible from the rocket's weight while greatly reducing the size and
complexity of non-reusable components. Their plan? To spin a small rocket in a centrifugal mass
accelerator under vacuum up to an astonishing speed before releasing it. Punching through the thickest layers of our
atmosphere at hypersonic speeds. Gaining 72 kilometers of altitude off nothing
but pure kinetic energy, before splitting its fairings and unveiling a substantially
miniaturized 2 stage rocket to continue its journey into orbit. You may question the numbers here, but this
isn’t the first time this has been done. Project Harp, standing for high altitude research
project, managed to get a projectile to 180 kilometers of altitude with a high powered
gun. They achieved a muzzle velocity nearly identical
to Spinlaunch’s planned launch velocity. However, scaling a kinetic energy launch system
up, to launch a 10 tonne projectile needs spinlaunch’s technology. Ofcourse, all of this is easier said than
done. The challenge facing Spinlaunch’s engineers
is immense. This endeavor demands several new key enabling
technologies. So in terms of key enabling technologies,
carbon fiber certainly take center stage. That’s David Wrenn, Spinlaunch’s VP of
Technology. I spoke with him on the Spinlaunch factory
floor about the carbon fiber reinforced plastic they are using for their tether. You know, in terms of its strength to weight
ratio, it's it's essentially unmatched by any other material on Earth. And the amazing thing is that it's actually
available in industrial quantities now and engineering tools and simulation methods exist
to really quickly iterate, understand what a composite structure will do. And then we have structures and test rigs
like this to validate in the real world that the components actually fail at the expected
loads. So just to give you a sense of the strength
of carbon fiber, this is a protrusion. So this is made by taking carbon fiber tow
essentially spools of carbon fiber and pulling it through a heated die with a resin bath. Basically the version gets impregnated into
the carbon fiber toe as it gets pulled through the heat to die. And you get these really nice, highly unique
directional structures that can be used for, you know, spin launch. Right. And so as small as this cross-section is,
right, I think this is about an eighth of an inch thick and only a few inches wide. This can do just under a quarter million pounds
of total load capacity, which is which is really, really impressive for what this is. Trying to convert to metric in my head. It's like, oh, yeah, that’s a lot. Yeah. I think that's like a million newtons or something
like that. So and then if you look at, you know, this
is where it gets interesting is, is can you build really thick cross-sections of carbon
fiber? You can see there's there's really great. Is this pultruded as well? So this is not opportunity to this is laid
up and then it's it's cured in an autoclave. So this is essentially a subsection of the
laminate that you would see at the root of the tether on the suborbital system. Okay.So this is, this is. So this isn't this is not unique directional
or protruded, but if it were if you were to take this the same cross-section here and
basically make this a pull treated fiber, if you've just stacked up multiple protruded
sections, you would get about 9 million pounds of total load capacity through this cross-section. So it's, it's impressively strong for what
it is. I mean, it's, it's heavier than you’d expect Yeah. Holding a carbon fiber brick. I don't think there's, I've never seen an
application where that much carbon fiber has been laid up. It's, it's rare to see carbon fiber this thick. Yeah. It really is rare, the final fully scaled
tether for spinlaunch’s orbital system is likely going to be the single strongest tensile
structure on earth. Let’s do the math on that. Spinlaunch aims to yeet its aeroshell, containing
the miniaturized rocket system, at about mach 6, that’s roughly 2 kilometers per second. With a radius of 45 meters, the tether will
need to spin 450 times per minute to attain that velocity. At that rate the g loading on the tether will
be 10,000 gs. Meaning this aeroshell is going to exert a
force 10,000 times greater than its weight due to gravity. The aeroshell with the payload and rocket
is going to weigh approximately 10 metric tonnes, so that means the tether, at the tip,
is going to need to be able support 100,000 metric tonnes, or 100 million kilograms. To put that into context, a fully loaded falcon
9 weighs about 0.55 million kilograms, so this tether is going to need to support the
equivalent weight of 182 falcon 9s. This is going to require a hefty piece of
carbon composite with cross-sectional area of at least 0.23 meters squared. That explains the brick of carbon fiber we
saw. That brick could support about 4.1 million
kilograms. So the full scale tether will need to be 24.4
times this size at its tip, but that’s just the tip. This equation tells us why carbon fiber is
so vital to this endeavor. Because each section of the tether has to
support the section above it, its strength to weight ratio needs to be exceptional. If we calculate the tether area near the hub
for the same carbon composite the tether only needs to increase in area by 2.5 times, at
about 0.56 meters squared. We would ofcourse need to add a safety factor
of at least 1.5 to this, increasing these dimensions by 50%. I have skimmed over this equation here, but
if you want to learn more about the engineering of this system, and energy of getting to space
in general, I have created an entire course on Brilliant to partner this video, and you
can sign up for it with the link in the description. That design is perfectly feasible and is reflected
in SpinLaunch’s renders. We even have the manufacturing skills necessary
to build even larger composite structures thanks to the wind industry. So, this is all well and good, but spinning
a carbon fiber composite up to Mach 6 isn’t possible in air. The aerodynamic heating would destroy it. So, to solve this issue. Spinlaunch created a massive vacuum chamber
around its tether. You know, there's a bunch of things at the
beginning of Spinlaunch that were nonstarters for a lot of people, like even just building
a large diameter vacuum chamber. You know, people were telling us, you know,
the one behind me here would cost tens of millions of dollars to build. And we ended up doing it. You know, we had this really, really kind
of scrappy lead mindset. And we ended up doing it for less than a couple
million dollars with ten people. Right. Which is unheard of. Was there, was there any specific kind of
engineering solution that you came up with that, to to reduce the cost that much? Yes. So that if you compare our vacuum chamber
to, you know, vacuum chambers that you would traditionally see and say in the aerospace
industry. A lot of the really, really, large vacuum
chambers, there's a there's some large industrial vacuum chambers out there. But there's, you know, quite a few of the
really large chambers around the world are for aerospace applications. And so they're achieving extremely high levels
of not only vacuum, but cleanliness. And so the cost is proportional to that. And it's kind of exponential. You know, they're achieving vacuums that are
on the order of ten to the negative 8 millibar thor. And, you know, typically we're operating at
about a million times worse than that. Spinlaunch is breaking new ground with this
kind of vacuum chamber. Typical large volume vacuum chambers, like
the world’s largest one at the Space Power Facility in Sandusky, Ohio, are designed to
simulate the vacuum of space. [3] Those require an extremely low pressure vacuum,
with tight tolerances and control of contamination. They even need specialized tools like lamps
to simulate the radiation and heat emanating from the Sun and cryogenic cooling to simulate
the heat of space. The people that built these facilities are
the industrial experts Spinlaunch had to draw from, and most thought they would never be
able build a vacuum chamber this large on their budget. But Spinlaunch had some things on their side. They didn’t need that extreme of a vacuum,
as their goal is not to simulate the vacuum of space. Their goal is to minimize drag and the power
required to overcome it, minimize the aerodynamic heating that would destroy the tether, and
eliminate all those pesky aerodynamics effects like flutter. That means Spinlaunch could use cheaper materials
like mild steel, where ultra high vacuums need more expensive specialized processed
materials to avoid outgassing, where gasses within the metal in the form
of oxides, or simply dissolved within the metal, are released into the vacuum. It also makes the process of drawing a vacuum
much easier. Drawing a vacuum isn’t as simple as just
turning on a pump and leaving it on long enough. The more air you draw out, the harder it becomes. As you are not only working against a continually
growing pressure gradient, but statistical probability. [5] The first stage of drawing a vacuum is to
remove the bulk gas, at this stage the gas is a viscous fluid, and the molecules within
the chamber interact with each other often. Here we can use traditional fluid flow pumps,
like a positive displacement pump. That mechanically moves molecules out of the
chamber, and higher pressure air at the back of the chamber forces air to fill the space
created. Allowing more air to be pumped out. But, as gas is removed from the chamber the
distance between the molecules increases. This is called the mean free path. The distance a molecule can travel without
colliding with another molecule. Now, pressure is really just molecules colliding,
and as collisions become more infrequent, the pressure gradients that are needed to
achieve equilibrium begin to vanish. Meaning it takes longer and longer for equilibrium
to be established, and the rate the pump can remove molecules lowers, as there are simply
fewer and fewer molecules near the pump to remove. At some point viscous flow stops entirely
and we enter a flow regime called molecular flow. Where the distance between collisions is actually
larger than the internal dimensions of the vacuum chamber. Meaning, the molecules are statistically more
likely to just bounce inside the chamber with nothing forcing them towards the exit. At this stage it is impossible to actively
pump the molecules out. The molecular pumps needed for this flow regime
instead act like some kind of Venus fly trap, waiting for a molecule to enter it, and then
its job is to prevent the molecule from returning to the original chamber. Turbomolecular pumps are basically multiple
levels of turbines that knock molecules in one direction and prevent them from traveling
backwards. These pumps require insane rotation speeds,
anywhere from 36,000 rpm to 72,000 rpm and need incredibly tight tolerances too; They
are trying to pump individual molecules after all. So, it goes without saying, these kinds of
pumps are expensive. All the while, outgassing and other leaks
are actively working against the game of pure chance. Creating a high vacuum requires extreme precision
in manufacturing and design. Spinlaunch didn’t need any of this. Mark Sipperley, the director of Engineering
at Spinlaunch walked me through the vacuum pump station at the New Mexico site. Here in the vacuum plant the, the most familiar
thing would be the tube that came out of the chamber and then runs underground is this
manifold. So this is the very end of it. So off of this vacuum manifold, we then have
a series of three different types of pumps up on top we first have roughly pumps, which
pull the atmosphere of like one atmosphere down to about 30 millibars. Those are dry screw pump that are essentially
like overlapping lobes. It's it's one form like a turbocharger. Then the next stage is we have this roots
pump, which is, which is like a yeah, Another shape of a turbocharger. It's like this the rotating twin screw pumps
okay. All right. So that kicks on at about 30 millibars. So it's mostly only in it's 30 millibars below. But you'll notice that each pump, it exhausts
into the pump like a pump, that's a slightly higher pressure. All right. So this roots pump only works in 30 millibars
below, but it can't exhaust all the way up to one atmosphere. So that's backed by another pistons pump So this this would also be like a great roughing
pump. So when we turn on the first system, we have
nine Edwards GSX pumps up there, and then this piston pump. Sorry, both of these piston pops when we get
down to 30 millibars, which we turn on a series of roots pump, which is this guy right here. And we have another smaller one on this one. These pistons are also running as well. And then once we get down below one millibar
they're going to turn on these vapor diffusion pumps, which only are really effective down
at the very low pressure. Those work like oil jets. So you vaporize oil, you shoot it down a series
of channels and it grabs onto the air molecules, runs them down a series of tubes and then
you have these cooling loops that will then condense out the oil and then the water, or
sorry, the air progressively makes its way through like a long path, and it eventually
goes to the roots pump, which can grab on to it, and then it goes to a piston pump,
then all the way out. So we talked before you know, vacuum may not
be the best description .most people think of vacuum like a hard vacuum like in millibar,in
torr is what most people are used to like. E to the minus -7 torr, like seven zeros are
six zeros. And the number that's like true vacuum. That's hard vacuum, that's where you test
like, you know, like electric propulsion systems and like high end high end space features. That is nowhere near the atmosphere that we
need. And that's that vacuum is also really expensive
to get to. We have to follow a lot of stringent rules
like you can't use steels, you have to use aluminums and use coatings. You know, even like putting your fingerprint
in an atmosphere in a vacuum that low, will take weeks to boil off. We only require the equivalent to the minus
3 Tor or as a .01 millibar or .1 millibar. Today we're going to be running at like one
millibar. We only pull the vacuum we need, because a
vacuum is expensive. So it’s is closer to describing it like
a high atmospheric chamber than a vacuum chamber specifically. And then it will be the same. And again, that's all driven by the aerothermal. That's all that's the only vacuum that we
needed to accomplish. So on the orbital system, we'll probably pull
a very similar vacuum, we don’t have to go much deeper, there’s no benefit to going
lower. This is another one of those technical issues
that the internet made a big deal out of, without fully understanding what Spinlaunch
actually needed out of the vacuum chamber. One of the other primary concerns expressed
on the internet was the tricky and unique problem of a vehicle traveling at hypersonic
speeds from a vacuum into a thick sea level atmosphere. To begin with, we need to prevent air from
rushing into the vacuum chamber once the vehicle is released. Spinlaunch is aiming to be a high frequency
launch system, capable of launching multiple satellites per day, holding the vacuum between
launches to decrease energy and time costs. However, the primary concern is the disastrous
effects that air would have as it meets the tether spinning at hypersonic speeds. This would be an incredibly expensive single
shot system if this was allowed to happen. To solve this problem Spinlaunch needed a
way of sealing the chamber extremely quickly after launch, so inside this long tube attached
to the vacuum chamber is a double door airlock, with doors on either end of the tube. This tube is also under vacuum during spin
up. As the vehicle is released, using a release
mechanism that Spinlaunch kept hidden from our cameras throughout the shoot,it passes
into the exit tunnel where the first door rapidly closes behind it. As this first door is closing the second door
will begin to open. The atmosphere will begin rushing into the
tube and give the aeroshell its first taste of the hypersonic flight regime it will be
flying in. The first and second door need to close quickly
enough to prevent air from entering the vacuum chamber. This is not an easy problem either. Millisecond delays that may seem trivial in
most cases start to mount up when the vehicle travels this quickly. The time it takes for an electrical signal
to propagate, the time it takes to overcome the inertia of the door, the time it takes
for a proper seal to form. All these problems become matters of survival
at these speeds. Once again, Spinlaunch are keeping their cards
close to the chest on this one, but they did give me a demonstration of the door closing
in their factory and engineering hub in Long Beach, California. Well, it’s it's moving really fast. And so when the when the you know, without
specifying, is he going to do a countdown You're ready for a countdown just let me know Yeah. So basically what's going to happen is, you
know, this is going to be filled with, you know, for lack of a better word, like a black
door which basically you'll see that like you can pass through this with a vehicle and
then in an instant it's going to be close. Okay. So and again, it's like fast in the blink
of an eye. So you'll see a little bit of settling as
a, as a after it closes. But it's, you know, basically 95% close within,
you know, 30 milliseconds. Oh wow, okay. Speaker
Closing the airlock. [Static] Speaker
Closing airlock in five, four, three, two, one. [LOUD BANG] It's pretty fast. Yeah that is not what I was expecting. [Laughing] Yeah, it's fast. So that actually closes. Like, it's actually hinged There's a pivot. Yeah, there's a pivot involved Yeah I wasn’t sure if it was going to be
a sliding thing. But the hinged one makes sense as well. Yeah, that wasn't that what I was expecting Yeah. So it’s 100% reusable, so you can set that
back up again and do it again and again and again. So that's a key aspect of it is that you don't
have any major consumables in the process. So, so that's fast. Visceral All right. [Laughter] It’s a door closing. I don't know what to ask. It's really important not to let everybody
back in. So that's you know, that's why we have it. Oh, everybody jumps. You can’t not. Yeah, yeah. So. So, you know, the airlock is a really critical
subsystem of the overall, you know, of the overall architecture as you travel from vacuum
into the atmosphere because the tether is still rotating at high velocities, you want
to maintain the vacuum inside of the vacuum chamber. And so the airlock is your first line of defense
for that. And so we have multiple redundant airlock
just like what you see here that the vehicle passes through and it subsequently closes
behind the vehicle, you know, preventing the air from in rushing and reentering into the
vacuum chamber. Amd so that the exit tunnel is really the
only portion of the chamber that experiences a rise in pressure. I imagine that allows you to reset and like
increase frequency of launches as well. If you're not having to re…like.. Yeah, totally. So you can, you can do, you know, you can
essentially provide a, you know, an air locked space for the end of the tether as well. And so you can basically just re-pressurize
that space as you load in new vehicles. It's possible you could do vehicle integration
in vacuum. But currently we're we're anticipating actually
preparing a small portion of, you know, interfacing around the tether. Repressurising a small portion and integrating
the vehicle without it being in vacuum or. What do you actually see the like how many
launches a day do you think you can manage? I think that's like one of the advantages
of this that you can yeah. I think on the very high end, it's upwards
of ten. I think on the low end, it's, it's, it's about
five is a pretty good nominal target for us. We see viability there. In Spinlaunch’s public videos, the secondary
air lock has simply been sheets of mylar. This is one of the few problems that becomes
easier as the launcher scales. As the exit tunnel grows in length, it will
take air longer to reach the door at the base of the exit tunnel. Spinlaunch have only just begun these one
third scale tests, with their fastest launch to date at 1.6 Mach, slowing ramping up the
speed of launch as they test their system. This prototype launcher features some other
simplifications compared to their final planned configuration. One of the most obvious problems to tackle
is the issue of vibration. When a spinning object's weight is not evenly
distributed it will vibrate. This is how rumble feedback works in gaming
controllers. A simple electric motor with an uneven weight
attached. However, with a structure as large as Spinlaunch’s
tether, spinning several times per second, any imbalance could shake the entire structure
to the ground. This is a major problem, because by design
the tether releases a 10 tonne weight right as it hits its maximum velocity. Spinlaunch needs a way to balance the tether
after launch. There is a very simple solution to this problem
though. Release a balanced weight from the other side
of the arm at the same time. Right now they are simply releasing a counterweight
that slams into an armored section of the vacuum chamber. We saw one of these counterweights being manufactured
out of fiberglass in the Long Beach factory, however over the long term having to clean
up the mess this creates after each and every launch is far from ideal. The ideal solution would be to release a counterweight
in the form of another launch vehicle after a single half rotation of the tether. The oil-filled journal bearing the massive
axle sits upon should be able absorb the force of this imbalance over a period of time this
short. The next issue we need to concern ourselves
with is the aeroshell punching into the atmosphere at Mach 6. This again, is a fairly unique problem. Typically weight is a restraining factor in
aerospace, but for spinlaunch the energy required to spin the aeroshell up to speed is actually
rather trivial, And I like to use the analogy of like a Tesla,
right? So the Tesla Model S plaid is about 0.7 megawatt. So on the low end, it's about 100 Teslas but
it really comes. Is that the full scale? Yeah, for the full scale. Yeah, yeah, yeah. For the orbital. System you're talking about like on the low
end. On a very low end. You know, it's probably about 65 to 70 megawatts. And again, that really depends on where you
end up with the final orbital tether, you know, whether or not you, you know, what,
what safety factor you. Operate with. What, what, you know, what tether strength
you end up with your effective tether, cross sectional strength that all feeds back into
itself. And then you have to kind of scale it accordingly. I would say like really conservatively, like. You know, if you wanted to spin. Up really fast, then you're talking about
higher power demand. So whether you want to speed up in an hour
or 2 hours, you know, proportionately makes a difference of of how much power that you
need. So but, you know, on the high end, you're
talking about maybe 150 megawatts of. Power, which is like. I don't know, maybe in layman's terms, it
sounds significant, but, you know, you can you know, there's, you know, there's motor
catalogs where you purchase you know, the motor that that has that capacity. Right. And so this is, you know, it's industrial
scale hardware and certainly, you know, mostly off the. Shelf do you need to worry about grid integration
at all when you're when you're suddenly drawing that much. Power? I mean. For better or for worse? No, because you're typically, you know, particularly
for for early, you know, orbital accelerators that we're building, we're expecting them
to be in really remote locations, kind of remote coastal locations. Greenfield sites that don't have substantial
existing onsite, you know, resources or power. So you're you're basically, you know, bringing
your own power. You you know, and so you have to, you know,
decide on, you know, what is your energy source or are you doing energy recapture, you know,
etc.. Spinlaunch claims their total energy demand
per spin-up is about 100 MWhrs. The cost per kilowatt hour for industrial
facilities is about 6 cent. So that’s a cost of 6000 dollars in electricity
cost. [9] That’s insanely cheap. To put that into perspective 100 megawatt
hours is equivalent to about 9600 litres of kerosene [10], about 8 tonnes of fuel. For reference, the Electron Rocket from New
Zealand's small satellite launching company Rocket Lab, capable of launching a similar
sized satellites, weighs a total of 12.5 tonnes. The vast majority of that weight being its
own fuel and oxidiser. Spinlaunch claims their rockets will need
to carry about 30% of the fuel and oxidiser compared to these competitors, with substantially
miniaturized and simplified rocket components. They are essentially replacing the first stage
of a traditional rocket with an easily reusable kinetic launch system. Spinlaunch will also be able to recapture
a good deal of the electricity stored as kinetic energy in the tether, using regenerative braking. Even further reducing their electricity bill. Because of all this, the limiting factor for
spinlaunch in terms of weight is actually the weight the tether can support, and as
a result, it actually makes sense to maximize the density of the aeroshell, because it affects
a variable that will drastically improve its ability to punch through the atmosphere. It’s ballistic coefficient. Ballistic coefficient is essentially an object's
ability to resist air resistance. Think about how hard it is to throw a feather. No matter how hard you throw it, it’s not
going to go very far. It’s got a large surface area for air resistance
to act upon relative to its weight. That’s a low ballistic coefficient. Ballistic coefficient is found by dividing
the mass of the projective by the drag coefficient multiplied by the cross-sectional area. So spinlaunch effectively wants to maximize
the mass relative to the cross sectional area. This is obviously not typical for aerospace
vehicles. If you, if you look at reentry capsules whether
it's for something like the Stardust return capsule where it's really, really high velocity
or you look at it reentry from orbit for a manned capsule or something like the space
shuttle. They're typically using thermal protection
systems that are extremely low density, like on the order of less than 300 kilograms per
cubic meter. It's just basically foam. And so so typically that means you're making
like significant compromises, like. The material often is. You know, brittle Or prone to fracture you
know, or really expensive or gets worn away. And then you have to replace the tiles, kind
of in the infamous case of the space shuttle. So what we're dealing with is, you know, you're
on the tip of the vehicle. You have, you know, materials like copper,
which, you know, not only are they, you know, a significantly higher density, right? You're talking about, you know, thousands
of kilograms per cubic meter, but they also have really great thermal conductivity. So basically, as you transition through the
atmosphere, you have a high heat load, but then you're basically into heavy, dense materials
that have good thermal conductivity. This is one of those unintuitive consequences
of this style of launch. When I first saw the full-scale aeroshell
on the Spinlaunch factory floor, I first asked if I could ride it like a cowboy, but then
immediately noticed the bi-metallic nose cone. I knew from looking at it that it was made
from copper and aluminum, and that struck me as extremely odd. Those metals would melt at the temperatures
I associate with hypersonic speeds. But, because spinlaunch launches at Mach 6,
it actually transitions through the lower atmosphere rather quickly, and as a result,
the heat generated can simply be absorbed by these large heat sinks. Aluminum and copper's high thermal conductivity
means the heat is distributed through the body of the aeroshell before it has a chance
to damage the vehicle. The hefty carbon fiber shell is also incredibly
strong. Spinlaunch has already pulled their smaller
scale aeroshells out of the ground, buried several feet deep from the force of impact,
and reused them with minimal refurbishment. With a parachute these aeroshells will be
fully reusable with minimal maintenance, especially as they serve no function other than to protect
the inner rocket’s stages. This isn’t an intricate mechanical machine. Launching from the ground at these speeds
comes with advantages too. If we plot drag coefficient vs mach number
for a bullet like projectile something rather unintuitive occurs. The drag coefficient rises as you would expect
up until we hit Mach 1, at this point it starts to fall as Mach number increases. This is the equation for drag. It’s proportional to drag coefficient, air
density and velocity squared. With drag coefficient being lower at hypersonic
speeds, it actually makes some sense to punch through the thick lower atmosphere, where
the high density air causes drag to rise, as fast as possible. Deceleration is a function of time after all,
meters per second square, meters per second lost per second. Let’s calculate the dynamic pressure this
drag would create at launch, and the deceleration it would cause. The dynamic pressure is found by multiplying
air density by the velocity squared and dividing by 2. At sea level, at Mach 6, the dynamic pressure
will be 2.6 Megapascals. The final aeroshell is 1 meter in diameter
and has a drag coefficient of about 0.1. Which means the force applied to the aeroshell
at launch will be 205 kNs. This sounds like a lot, but here's where the
ballistic coefficient comes in. This drag force is being applied to a 10 tonne
body moving at mach 6. That’s a lot of inertia. Force equals mass by acceleration. Acceleration equals force divided by mass. That means high mass equals less deceleration. In this case deceleration due to drag will
be about 19.8 m/s per second at launch, but it will rapidly decrease as we move through
to thinner and thinner layers of the atmosphere and lose velocity. In fact, with Spinlaunch’s planned trajectory,
we can plot the atmospheric density the aeroshell will encounter over time. Halfing in just 5 seconds, and dropping to
less that 10% of the original air density in 15 seconds. While gravity will remain more or less constant
at 9.8 m/s per second. That means gravity loses form the majority
of energy losses in our transition to orbit. In total spinlaunch will lose about 150 m/s
of velocity to drag and 1000 m/s to gravity. Satellites like Starlink orbit at 500 kilometers
with a velocity of about 7700 m/s, so even if Spinlaunch maintained it 2050 m/s velocity
from launch up until the aeroshell broke apart, the 2 stage rocket hidden within would still
have its work cut out for it. However, now free of the mass of the aeroshell,
the substantially miniaturized rocket needs only a fraction of the mass of fuel and oxidiser
to rapidly accelerate the 200 kilogram satellite, the largest satellite this system can launch,
through the thin atmosphere at this altitude. We can actually graph the relative velocity
of the spacecraft over time. It Started at Mach 6 at launch, and ended
up at about 1500 m/s when the aeroshell splits. The rocket motors then kick in to rapidly
accelerate the satellite to its 7700 m/s orbital velocity. The physics here absolutely checks out here,
but whether the economics and cost of development will be viable is the big question to be answered. Spinlaunch has built a 1 third scale prototype
at a relatively low cost, but the hardest part of this technology is scale. They have reached 1.6 mach thus far, have
tested their satellite components at 10,000g in their test facility in Long Beach, and
are continually upping their test parameters, pushing further and further. This is a comparison of SpaceX and Spinlaunch’s
proposed launch trajectory, but it doesn’t tell the full story of the real driving issue
here, economics. A SpaceX launch to low earth orbit costs about
67 millions dollars. The heaviest Falcon 9 payload to date has
been 16,250 kg on a densely packed starlink mission. [14] That equates to a launch price of about
4100 dollars per kilogram. However, small satellite launch companies,
like Rocket Lab, who offer greater control over orbit and launch schedules, charge about
15,000 to 25,000 dollars per kilogram. Dollars per kilogram is not a perfect metric,
but gives us some idea of the competition Spinlaunch is facing. Spinlaunch’s main competitive advantage
is in the decrease of expendable materials like fuel while substantially miniaturized
rocket components. They also have huge potential to launch far
more frequently than their competitors, helping the economics of scale to kick in. Spinlaunch claims to be targeting an ambitious
per launch price in the range of half a million dollars, placing them at 2500 dollars per
kilogram. In my time in Spinlaunch, talking to their
engineers, it’s clear they are excited and believe in this company. The basic napkin physics for Spinlaunch absolutely
checks out, and they are well on their way of solving the engineering challenges, but
scaling up this monstrous engineering effort is going to require enormous amounts of investment,
and Spinlaunch could not disclose the answer to many of my questions, as they seek patents
for their solutions. I got little info on one of the most difficult
parts of the launch system, the release mechanism for the aeroshell; even the 3D models Spinlaunch
provided for this video had the release mechanism removed, so we had to model our own along
with the internal rocket structure. The design of the satellites is another problem,
due to the massive gs the satellites have to survive, but g-hardening isn’t as large
an engineering challenge as the internet seems to think. The most difficult part. So besides the structure is, is also the reaction
wheel. So the reaction wheel is, generates momentum
and basically steals the bus. Yeah. And so it typically is a big mass that's cantilevered
up at a certain angle. So which is the one thing that we don't like,
you don't want having a big mass sticking up on a can really. This is what I assumed was going to be like
a difficult thing to because it inherently has to be fairly high mass to control the
satellite. Right. And so we've done a lot of work to instead
of re-engineering the wheel itself and figure out different ways to do that, we basically
just took and created it took a clever way of deploying the wheel. So we support the wheel in the flat orientation
and we spin. So when it's spinning, it's, it's well supported. The bearings are unloaded and so it can spin
and do its thing. And then we deploy the wheel for when it actually
used to operate. Okay. So it's a it's a simple solution for what
could have been a really difficult problem. And does the the axis of the actual wheel
cause any issues when it's like being loaded? I imagine that's a fairly high weight to have
on the axle yeah. So we, what we do is we unload the bearings
and as part of the deployment mechanism we actually move we reload the wheel into the
bearings. Oh, okay. So it's just taken off completely Okay. That's interesting. Okay, that's funny. Yeah. So again, trying to make simple solutions
for very difficult problems. Yeah. I like that. And like those are very simple answers, right? Like I figured that the like the inertial
wheels would be difficult, not like you just think about it as like, yeah, that's actually
a fairly easy thing to just not deal with. You don't have to have it in the exact configuration
when you like launch, right? Same with the solar panels.You can have them,
like you said, loaded. Yeah. So it's the problems aren't necessarily hard
to deal with. It's just you have to think differently. Right? And so, you know, Randy, who you talk to earlier,
that's one of the things he's been saying a lot is it's not that these are difficult
problems. We just have to change the way we think about
design. So it's a little bit it's not a lot. The nice part is to that over the last 60
years, what people have been trying to do with satellites actually has helped us because
they want to reduce mass. They want to make things stronger. So every bit that they're forcing them to
deal with shock and vibe already helps us. And it already inherently starts to make them
more hardened. Most components, we don't have to do anything
to them. Maybe a little epoxy here but like we one
of the most surprising events that we have here among the entire team is we took a board
that had a password stuck up, you know, maybe a quarter of an inch. And we all looked I was like, okay, that thing's
it's going to fly off the wall. And we spun it and we brought it back and
it just went over and that was it. And we are like, all right. Our intuition is completely changing. And yeah, and it's because it's, it's so little
mass and it's being held on by two pieces of steel. You know, the amount of force that that was
really imparting on those two piece of steel was relatively small. Right so it just bent over and we all kind
of like, Oh, yeah, after you think about it, it does make sense. Okay. Yeah, that's right. So our intuition is starting to grow about,
yeah, this little connector of the sticking up really isn't that big of a deal. And so that has been in a positive way. Very surprising. Gs can only create force where there is mass,
and it turns out the satellite industry has been finding ways to reduce mass for decades. A simple aluminum can is capable of withstanding
10,000 gs with a basic redesign of its structure. Minimizing weight located on unsupported surfaces
lowers the mass available to be multiplied by the gs, and some simple corrugation can
help the aluminium absorb some of the loading without buckling. We spun up an off the shelf star tracking
camera using Spin Launch's in-house centrifugal accelerator, which can already achieve 10,000
gs, and the camera worked perfectly fine just moments later. This is a really interesting engineering challenge,
that I think the internet is giving a hard time for some bizarre reason. Posing questions about basic physics calculations
without actually doing the math, and then saying it’s impossible. Even missing the fact that kinetic energy
launch systems have already reached beyond the Karmin line 6 decades ago. If you want to check the math and physics
of this problem yourself, instead of just taking my word for it, I have, in partnership
with Brilliant, created an entire course deep diving into this problem. Starting with an in-depth interactive lesson
on the physics of orbit and traditional rocket launches, and moving on through to interactive
calculations of the launch speeds a kinetic launch system like this would need to achieve,
and the design considerations for the tether itself. This is your chance to test your understanding
of the things you learned in this video with a curated interactive course. All designed with fun interactive Real Engineering
blueprints. You can get access to that course right now,
and all of Brilliant's other curated interactive courses, by clicking the link to the description. You can get started for free, and the first
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and engineers. If you are looking for something else to watch
right now you could watch our last video on the life limiting challenges facing the next
generation of spacesuits, or you could watch Real Science’s new video on the strange
phenomenon of deep sea gigantism.
I love he called out the people in this subreddit that were wrong on nonsense about Gs and drag, while still being critical of challenge to upscale without shutting the idea down or calling it a scam.
We can, with the superior siege engine: the trebuchet.
I am curious how $/kg (35:15) was still not lower than rockets. The main energy cost seems to be drawing the vacuum, it seems this calculation is based on having to draw a complete vacuum for each launch rather than either calculating it with: 1) combining two launches at once (one on each side of the arm) or 2) re-using the vacuum for multiple launches. Especially because earlier in the vid, electricity costs for spinning were $6000.
That door closing did not seem nearly fast enough to stop the inrushing atmosphere at a very high level. Certainly enough to block most of the air, leaving something of a vacuum behind... but enough to be rapidly reusable? I dunno. I don't know how much is too much, how rapid is rapid enough, etc.
But that door did not look like some hyper-secret amazing tech... it looked like they made a carbon fiber door and put it on a spring and they are counting on air pressure to create the final seal, which means they are gonna leak a bit on purpose.
In the past, I watched a video on this subject or maybe this video. I think that linear acceleration would be better for the satellite and attached rocket.
They mention HARP but not Super HARP or its living successor, Quicklaunch (now Greenlaunch iirc). I wish there was more attention for other kinetic launch systems.
What about the angular momentum of the projectile? It will be spinning at very high RPM and that angular momentum doesn't disappear when its released.
Could we? Yes. Is it worth it? Everything thus far suggests not.
Do the guys from Real Engineering actually have an engineering degree? There would have been so many questions to ask about that system, that seem to be deal breakers for the spinlaunch.
Example: How are they dealing with the tumble of the projectile, as it leaves the launcher? (Because in the videos it looks like they just let it tumble out of control). Most probable answer is: they can't stop the tumble at all - which makes the system unusable. I would have loved to hear the answer to a question like that.
Also, that airlock door... Jesus. That thing can't hold a vacuum. I worked with vacuum systems for a significant period in my professional career, and that's just laughable. Even if it closes in time (I'd doesn't in the video), air rushing in through the now open launch tube will actually smash into that "Tupperware lid" at the speed of sound.
That whole company is just there tu syphon some grants and VC - and they all know it.