SLOW MO! SpaceX Vacuum Raptor Engine

SLOW MO! SpaceX Vacuum Raptor Engine
#SpaceX #RaptorEngine #Starship
Shutdown of a Raptor vacuum engine in slow motion. The engine’s nozzle is sized for use by Starship in the Earth’s upper atmosphere and outer space, so operation at sea level and low chamber pressures results in flow separation creating visible rings in the exhaust
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VIDEO SOURCES:
SpaceX
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[@jpburned2414]

Holy crap, the flow separation is crazy!!!!

[@TheLaunchPad]

right!

[@satrianaliqa]

😮

[@Potatoincanada201Unknow-bv1yy]

I agree!

[@StrawberryFlavouredCat]

The shock diamond dissolving is so cool

[@winsurfer123]

A narrative explaining throttle up/down from Zach would be awesome.

[@MiguelLopez-tz7jp]

What a beautiful engine!

[@Antirobo1]

I have no clue what is happening. But it is both impressive and beautiful.

[@MrSpacePhoneRepair14]

I think its the spacex vacuum engine slow mo engine shutdown but could be another test

[@lukestrawwalker]

@@MrSpacePhoneRepair14 correct....

[@frankwelch3594]

Beautiful huge warp diamond just starting in the exhaust. Need to back up to see it!

[@lukestrawwalker]

MACH diamond, not warp diamond LOL:)

[@tedsmith6137]

I would like to see a slow motion of a start up!

[@cpunut]

Shutdown is a beast!

[@0cujo0]

A vacuum engine being tested at sea level(approx). There was a time when this wasn’t possible.

[@KiRiTO72987]

There still are some vac engines that can't be just depends on how optimized for vacuum the engine is

[@RiNo5659]

The real test for vac engine are when they are in the vacuum of space. Unless there is a testing medium they can use, which is so impractical, they can only test that the systems are working and the thrust of the rocket.

[@PeterJCalkins]

Dang...y'all are fast!

[@wrxsti1987]

AMAZING

[@DoyoVR]

Here before it popular

[@lyricbread]

What a unit!

[@man-from-2058]

0:12 the way the massive vapor cone or whatever it was just vanished

[@brycedarnell7395]

It honestly looks like CGI, that’s just incredible. Next we build a Venator-class cruiser with this one.

[@clipseobastian1433]

How do you think this is CGI? It just in slow motion prob making you think look CGI.

[@brycedarnell7395]

@@clipseobastian1433 It just looks really similar to the massive ion engines on the Venator-class jedi cruisers from the clone wars, and when they fired one of them up in an episode of the bad batch

[@scottmitchell7302]

Done good

[@ScienceSpace.M]

I like it so much

[@marcelomapurunga6936]

Lindas imagens 🇧🇷

[@EdwardNathanielDeLosSantos]

Wow 😎

[@Neront90]

Apparently they reinforced the edge of the engine to prevent damage from flow separation I wonder if they will do something similar on Starship to allow it to start its vacuum optimised raptors at sea level as a part of Launch Escape System

[@RandomRoulett3]

i guess thats what makes the fart sound at shutdown.

[@smokingfoxx]

Smooth like butta

[@Rob-ue7ig]

This is some great rocket engine p***🎉

[@PaddyPatrone]

I regularly come to this channel just to rewatch original spacex videos lol. Twitter is such a terrible video platform.

[@MrBen527]

REALLY SLOW!!!

[@giridharyerramsetti7117]

There are shock waves inside the nozzle, it so for flow separation and ring formation?

[@realgammer6645]

MAGNIFICENT!!! 😮

[@Raptorman0909]

After the flow separated the exhaust went white or nearly white -- not sure what that was. This didn't look like the typical setup for testing vacuum engines.

[@techraan2160]

this RVac 3?

[@2EEsTunes]

i need someone smarter than me to explain the physics of what is going on here

[@lukestrawwalker]

Rocket engine firing... this one is vacuum optimized, which means that the nozzle is actually bigger than it should be for operating at sea level atmospheric pressure (14.7 PSI) in the dense lower atmosphere. This is important because the atmosphere actually exerts this pressure on the burning gases in the rocket engine exhaust just as it does with everything else, keeping it from expanding by a certain amount. If you've ever watched a regular SpaceX rocket launch of Falcon 9, you'll see that the plume (exhaust trail) from the engines is quite straight and slender when the rocket lifts off, but once it ascends out of the lower dense atmosphere, at an altitude of about 20 miles (90% of Earth's atmosphere is below 20 miles high) it begins to expand rapidly and takes on a different shape, due to the plume interactions between engines (leading to 8 distinct "lobes" of fire from the outer 8 Merlins plumes impinging on one another). As the plume expands, if you remember Boyle's law from high school physics, an expanding gas cools down, so the flame actually at some point becomes nearly invisible, because as it expands it cools below the point where the gas glows and emits light... then the engines shut down and it stages, and if you ever notice, the second stage engine only has a few "visible flames" licking out around the base of the engine nozzle, because as the gases expand out the nozzle they cool enough to go invisible. Now, all that said to explain why the upper stage nozzles on vacuum optimized engines are SO much bigger, and the problems that presents down near the surface in the dense lower atmosphere... because there is essentially vacuum, NO air pushing inwards on the plume at high altitude (above 62.5 miles or 100 km, the so called 'Karman line' that defines the edge of space) the gases expanding out the back of the rocket engine expand much more. This can be useful energy IF it is captured by a larger nozzle and that expansion exerts force on it, which is thrust. SO why not use larger nozzles even on sea-level engines and gain more thrust?? Because in the dense lower atmosphere, the gases are compressed by the surrounding air and don't expand as much. This leads to something called "flow separation" where the gases will not be able to expand out to the full diameter of a larger nozzle, and will RIP away from the surface of the nozzle. Gases moving at high speed over a surface exert less force than slower moving gases, (which is the principle of lift that causes airplane wings to be pushed upwards by the slower moving air below them) and this creates a low-pressure area where the gases separate... the higher pressure atmosphere the rushes in like a wedge to fill this low pressure area, which creates a flow instability and pressure spikes that can destroy an engine very quickly. Plus of course it robs enormous amounts of power which is counterproductive to producing thrust in the first place, so the engine has to be designed so that the expansion ratio of the nozzle is optimized for the flow, pressure, combustion temperature, etc. of the engine design itself. Too large a nozzle will flow separate, too small wastes energy by not capturing the maximum amount of exhaust flow expansion as thrust against the nozzle inner surface. As the hot combustion gases leave a rocket nozzle, they expand outwards, pushing against the nozzle creating thrust. As gases expand, they cool, and they also slow down since the same volume of gases is not flowing through a larger and larger opening (the nozzle cone). The maximum pressure is in the nozzle throat of the engine between the combustion chamber just below the propellant injectors, and the smaller nozzle throat at the back of the combustion chamber that the exhaust gases exit through. SO as the gases expand, they cool and slow down as they move from the nozzle throat to the back end of the nozzle, which creates some interesting flow effects... as the gases exit the nozzle, they then further expand against the atmosphere (or at altitude into surrounding vacuum) and they expand at different velocities due to the intricacies of flow dynamics of hot gases. Some of the gases are flowing supersonically (or even hypersonically) and some are travelling slower than the speed of sound, so this creates wavefronts, essentially 'standing waves' much like those of a water-injected "surfing pool" where one rides on a standing wave of water from high pressure high volume water injectors flowing up a ramp. These standing wave fronts create what is called "mach diamonds' within the exhaust, as these pressure waves can move back and forth and interact depending on the flow rates and volume of the gases, their speeds, etc. These denser wave fronts are hotter (because they're denser) and thus emit light when the surrounding gas is cooler and not emitting light or less light or a different color light, so they become visible in the exhaust stream. High speed high power jet engines can have multiple mach diamonds, due to the expansion ratios of rocket nozzles, there's usually only one or two, depending on flow interactions,and they tend to be "Mach cones" instead of true diamond shapes which are common in jet engines. You will see that there's a stable "Mach cone" behind the engine bell when its operating at a given power level (thus amount and flow of gas and given pressure, its all a stable steady-state condition so the Mach cone is more or less "stable". As the engine powers down for shutdown, the flow rates reduce, the pressure reduces, and the Mach cone travels forward in the flow out of the exhaust in response to the changing flow and pressure conditions, leading to changes in the standing wave interaction inside the exhaust plume gases. At some point, the wave front changes and it "pops' like a soap bubble, going from a 'Mach cone' to a "Mach ring" as the standing wave collapses into a ring shape from the previous cone shape, due to reducing flow and pressure interactions within the plume. As the engine shuts down, this ring expands out in the flow to the nozzle inside surface, and begins to "flicker" back and forth due to flow separation as the rate of gases being expelled from the combustion chamber is no longer enough to prevent flow separation from occuring within the nozzle as outside air is pushing inwards on the outward flowing plume of gas... these 'flickers" are pressure waves in the hot gas of the exhaust as the air pushes inward in pulses of flow separation... these results in pulses where the temperature in the wavefront rises rapidly due to the atmosphere preventing it from expanding as rapidly, causing it to retain heat that would otherwise be lost to expansion, thus getting much brighter and "flashing" or "flickering" brighter; the more heat the more pressure it exerts, so it pushes the impinging atmosphere back, which then lowers the pressure and allows it to cool, thus expanding more and cooling and growing dimmer, which then allows the air to push in again, and repeats the cycle a few times until the last of the combustion takes place and the engine firing is over, and the last of the hot gases expands out the nozzle and reaches equilibrium with the atmospheric pressure pushing inwards into the nozzle... It's all about flow, pressure, and temperature, and standing wave fronts causing gases to glow... it makes what is invisible visible, and a beautiful phenomenon it is... :) Later! OL J R :)

[@2EEsTunes]

@@lukestrawwalker water-injected "surfing pool" analogy worked well thankyou

[@lukestrawwalker]

@@2EEsTunes you're welcome!

[@dsdy1205]

​@lukestrawwalker this is really well done 👏 👏

[@lukestrawwalker]

@@dsdy1205 thank you...

[@TheMoneypresident]

But it's not blowing itself apart.

[@lennyjames8457]

me on the toilet after eating a lethal amount of taco bell

[@mehrnazzandieh9366]

🪄 🚀💖