welcome back as we continue with our examination of thunder fact second video
in his Hyperloop busted series we're picking up the video starting at around
nine and a half minutes in and much of the rest of this second video
Thunderfoot engages in a lot of scaremongering but in the end he doesn't
quantify the risks while it is true that there are scenarios in which passengers
can be killed on the Hyperloop this is also true for any other form of
transport
it's hardly the case that no one ever dies with cars airplanes and trains it's
not enough to nearly say there are risks they must be quantified and compared to
alternatives underfoot completely fails to do so and 933 Thunderfoot points out
that a rupture of the pods cabin could kill the passengers actually he does far
worse there's another problem
people also need to add to live so there's any rupture in the high blue
capsule for any reason whatsoever you will die in the Hyperloop in pretty much
exactly the same way that you would die in deep space he boldly declares that
any rupture of the pod for any reason would kill the passengers
however the paper clearly details on page 54 what contingencies are in place
for the compression events Hyperloop capsules will be designed to the highest
safety standards and manufactured with extensive quality checks to ensure their
integrity in the event of a minor leak the onboard environmental control system
would maintain capsule pressure using the reserve air carried onboard for the
short period of time it will take to reach the destination in the case of a
more significant depressurization oxygen masks will be deployed as an airplanes
safety of the onboard air supply in Hyperloop would be very similar to
aircraft and can take advantage of decades of development and similar
systems in the unlikely event of a large-scale capsule depressurization
other capsules in the two will automatically begin emergency braking
wants the Hyperloop tube with undergo rapid repressurization along its entire
length since humans are capable of surviving in the banking for up to a
minute and possibly even as many as three these contingencies effectively
eliminate cabin decompression is a life-threatening scenario
come on Thunderfoot you're not even trying to be honest with this garbage
you're spewing further underfoot
fails to address the likelihood of such an event it stands to reason that the
pod cabins would be more reliable than commercial jets after all airplanes are
subject to weight limitations that require the fuselage to be light enough
to fly the Hyperloop on the other hand uses a different mechanism for
levitation and does can be built with the sturdier cabin
also unlike jets the Hyperloop does not have to contend with potential bird
strikes for these reasons one can reasonably assume that while certainly
not free of all risk Hyperloop odds would probably be safer than commercial
aircraft in this regard and keep in mind
commercial aircraft have one of the best safety records of any mode of travel
people won't be able to hear you call for help because alien formulas in space
no one can hear you scream oh come on now you're just being stupid
obviously the ponds will be equipped with sensors to detect the loss of cabin
pressure and radio the information to a control center i refer you to page 54
again it's amazing what you learn when you actually read the proposal the
velocity of the capsule is about that of a bullet fired from a gun except it's a
15-ton bullet any failure whatsoever will rip through that 2-centimeter on
youtube like candy
no it wouldn't do bullets ripped the barrels of the guns that fire them know
they slide along it the ponds travel parallel to the surface of the tube so
their relative velocity the wall is effectively zero as long as the air
cushions are made of a material that somewhat softer than the steel tubing
the pod would simply slide along the inside of the tube in the same way a
bullet slides down a gun barrel this would not be fatal to the passengers
because the coefficient of friction will be less than one meaning that the pod
would slow to a stop at a rate less than 1g Thunder fits next argument is based
on the flogged conception of compressible fluid dynamics I can't
fault underfoot for this the physics involved are incredibly complicated so
hold onto your hats folks it's gonna be a bumpy ride
see what I did there in order to understand where Thunderfoot went wrong
we have to take a crash course in compressible flow
let's examine the physics behind a convergent nozzle
because you have a source of high pressure gas on the larger size of the
mouthful and low pressure gas or vacuum on the smaller side naturally the gas
will push itself from the high pressure region to the low pressure region as it
does the gas expands by accelerating down the nozzle in doing so the
temperature density and pressure drop in accordance with thermodynamics in the
ideal gas law the drop in pressure associated with increased velocity is
known as the venturi effect but an interesting thing happens if the ratio
of high pressure to low pressure exceeds a certain limit at this point the gas
reaches the speed of sound and rarefaction waves can propagate against
the flow to cause any increase in mass flow through the throat
however the gas coming out of the nozzle may still have some residual heat and
pressure and thus it continues expanding and accelerating beyond the speed of
sound in order to further accelerate the gas and useful manner a divergent nozzle
must be used to redirect the expansion and generate sustained flow with a
velocity over the speed of sound
this system is known as a convergent divergent nozzle and is the basic
principle behind most rocket engines
yes this really is rocket science physicists often simplified this
phenomenon by stating that you needed the Virgin nozzle to accelerate a gas
beyond the speed of sound but this is only true for sustained flow and doesn't
apply to the leading edge of a pressure wave propagating down the long straight
tube like the Hyperloop we can actually calculate the maximum velocity the gas
can reach with this equation maximum velocity equals the square root of two
times C sub P times T sub T where C sub P is the constant pressure heat capacity
and T sub T is the stagnation temperature in other words the
temperature of the gas before it starts moving according to engineering tool box
the constant pressure specific heat capacity is 1.00 five kilojoules per
kilogram kelvin let's assume a temperature of 20 degrees Celsius or 293
kelvins which is 68 degrees Fahrenheit fairly common in central California
plugging these values into our equation we get a maximum velocity of 767 . for
m/s of course in real life this value will be slightly
les is the small amount of air pressure on the inside of the tube will prevent
the incoming air from expanding completely so the air entering the tube
is limited to the speed of sound while the leading edge of the pressure wave is
limited to just over 700 meters per second this is important because
according to the conservation of mass and the venturi effect the pressure must
smoothly transition from 100 Pascal's at the leading edge of the pressure wave to
figure a little less than 1 atmosphere at the rupture still with me i'm really
impressed if you are we're dealing with some pretty advanced physics but i think
i said enough so let's go back to the Thundercats criticisms from 1142 1603
one of the delves into a very long-winded and highly speculative
explanation of how a few bullets could cause a cascading failure that would
kill everybody in the hyperlink in it he makes quite a few ridiculous assumptions
he argues that a few bullets can cause an air pocket which will cause the
forward compressor to explode which will cause the pod to crash through the tube
which will result in a wall of one atmosphere air moving down the tube at
the speed of sound which will destroy the capsules
let's go through these assumptions one by one first
what would happen if someone did shoot a few holes in the Hyperloop if say for
instance is a pocket of high pressure air because someone shot a few holes in
the Hyperloop then the turbine is all of a sudden going from running it 1000 of
an atmosphere to hitting a pocket of air a one-tenth of analysis that figure
sounds a bit hi I'm Betty just pulled it down at his ass
any bets on how far off eous as i mentioned above the air coming in with
expand rapidly down both directions of the tube
let's assume the bullet shot of the tube is a 50 caliber BMG one of the most
powerful rounds available to the public
it's worth mentioning that even the armor-piercing version of this round is
only rated to penetrate 19 millimeters of Steel not the 22 23 millimeters of
Steel proposed for the Hyperloop however this is for a range up to 1,500 yards
and we did find a video of this round being fired at multiple layers of
happens steel body armor plates for it penetrated too but not three layers so
it looks like the round with just barely be capable of penetrating once
side of the tube and embedding itself on the other side if the terrorists can get
close enough
it's also worth noting that the Hyperloop could be made completely
bulletproof simply by doubling its thickness this would effectively double
the cost of the tube but that's only a ten percent increase in the cost of the
entire project it's also completely unnecessary as will see a 50 caliber
bullet would punch a hole about 1.26 square centimeters in size the
cross-sectional area of the tube on the other hand is 3.90 square meters and
since expansion will occur in both directions
this gives us at the Virgin nozzle area of 7.80 square meters
this gives us an expansion ratio of 60 1900 in short this would result in a
localized overpressure of only 1.64 Pascal's a pressure increase of less
than 2% however Thunderfoot throws out a figure of one-tenth of an atmosphere
which is over 10,000 Pascal's he's off by a factor of six thousand the second
stupid assumption was that hitting the overpressure would cause the compressor
to explode
those are going to have a hundred times the force acting on it which is the sort
of thing that causes blade failure
this is nonsense in part because the actual increase will be more like two
percent but even if we grant hungerford is totally laughable figure as i
explained this pressure gradient would rapidly stretch down the tube so the
compressor would slow down gradually as pressure built up it wouldn't explode it
wouldn't even sees powering the air cushions and SpaceX knows this as they
said in the paper minor depressurization of the tube is unlikely to affect
Hyperloop capsules or passengers and would likely be overcome by increased
thank you pump our any minor tube leaks could then be repaired during standard
maintenance the third assumption is that an exploding compressor would cause the
pod to crash through the wall of the tube any failure whatsoever will rip
through that too sent me two hundred tube like candy also nonsense as we
explained the problem probably just slide down the tube coming to a stop
after a significant distance even if the automatic emergency brakes didn't
boy it wouldn't even kill the passengers of that one pod the fourth stupid
assumption is that this would cause a wall of air to move down the tube at the
speed of sound but you can still expect it to kill pretty much anything it hits
me a rough idea of one atmosphere pressure wave will do from some nucca
benchmarking tests or what about the people trapped inside this 600
kilometers long steel tube well there's a wall for air traveling down towards
them at about the speed of sound essentially a shockwave and the kill
everyone in the capsule when it hits them as I demonstrated this would not be
the case within seconds the pressure gradient will have stretch down over
several kilometres so instead of a jarring change in pressure comparable to
a blast away from a nuclear bomb what we'd actually see is a gradual buildup
in the pressure of the air surrounding the pod
not only that but if it completely ignores the papers proposal for
emergency repressurization bounds along the length of the tube for just such an
emergency which would automatically activated the system detects a rupture
once again page 54 and the fifth stupid assumption is that the pods will be
destroyed by a 1 atmosphere pressure differential now of course you have to
hope that the emergency bridge a good enough and the capsule strong enough to
survive being hit by that one atmosphere pressure way and honestly I've got my
doubts about that because these capsules are designed to run at 1000 of an
atmosphere
oh come on just because the capsules normally operate at 11 thousands of an
atmosphere doesn't mean they couldn't be designed to handle one atmosphere
pressure gradient in fact the capsules have to stop for boarding and
disembarking don't they
that would be in one atmosphere wouldn't or just under think that all have to
board wearing spacesuits and while it is true that flow choking may result in a
buildup of pressure approaching one atmosphere has demonstrated in our first
video this would not expose the passengers to lethal accelerations nor
would it be difficult to engineer a capsule capable of standing up to this
pressure
here's a good comparison to help visualize the pressure gradient we're
looking at and that's the Hyperloop pod 10 meters in length being submerged in
water knows
first until its rear is at the surface that's the kind of pressure revealing
with who that was a lot so let's stop here for now the good news is you're
through the worst of it
the physics and the rest of this series shouldn't need to be anywhere near this
advanced but this does seem like a good point to leave off until our next video
so stay strong and be free