SpaceX CRS-4 SECO view of LOX tank as it enters zero G

That's kind of cool...

We saw that during the launch feed the other night and were wondering what the heck we were looking at as they were switching feeds amongst a number of cameras onboard. In the conversation a view inside one of the tanks was one of our guesses....

That is really amazing! I had no idea that they had cameras inside the tank. But i guess they have for quite some time
I just found a video from inside a the SA-5, Saturn 1 - internal LOX tank during engine burn (partial)

[video=youtube;PV6NDTbJB3A]https://www.youtube.com/watch?v=PV6NDTbJB3A[/video]

I wasn't expecting the really small baffles inside the SpaceX tank as compared to the huge baffles that I had seen in that film from the Saturn. They must've decided that a little baffling went a long way.

Here's one of the interior of an S-IVB stage as it flies to orbit and then shuts down... while the engine is burning, the liquid hydrogen is kept firmly seated on the aft dome of the tank, but when the engine shuts down, it floats off across the tank in great splattering globules that spread themselves over the quartz window the camera was looking through, which explains the distortion. Once it settles down, though, you can see great blobs of liquid hydrogen floating around inside the tank...

[video=youtube;IBWw_QJKAsI]IBWw_QJKAsI[/video]

On "The Mighty Saturns" video from Spacecraft Films, the entirety of the Saturn I interior tank view is shown... near the end of the video, when the engines shut down and the retros fired to separate the stages, the propellant comes RUSHING back up the baffles and core toward the camera due to the negative acceleration imparted to the coasting stage, spraying the camera window with propellant.

What's amazing to me is that you look inside these tanks, and you're seeing stuff that looks like a swimming pool full of water, but it's ultra-cold propellants at anywhere from -290 degrees (for liquid oxygen) to -453 degrees (for liquid hydrogen). Amazing...

It's pretty interesting how they did these as well, at least back in the old days... they used small quartz windows installed in fittings bolted to the tank, and early fiber-optics to carry the light and the images to the cameras mounted in ejectable pods... The lit the interiors of the tanks with external lights shining through these "windows" and then piped the light back out to the cameras to film it. Once the staging was completed and the job complete, the cameras were ejected to parachute into the ocean inside protective pods equipped with radio location beacons, parachutes, and flotation devices so they could be recovered.

I think they beamed back the images from the orbital stages like the S-IVB, which they had instrumented to test the reaction of LH2 inside the tank to microgravity in orbit... the pods were designed for first and second stages before they achieved orbital velocities, not to reenter from orbit...

I suppose this is much easier nowdays with microcameras and microelectronics... the hardest part is probably engineering the tank penetrations and the windows through which the lighting and camera looks...

Later! OL JR

RoyAtl said:

I wasn't expecting the really small baffles inside the SpaceX tank as compared to the huge baffles that I had seen in that film from the Saturn. They must've decided that a little baffling went a long way.

Click to expand...

Well, you have to remember, those Saturn tanks were built way back at the beginning of the space age... controlling propellant sloshing was, like many other things, not well understood and a sort of "black art" back then... so it's really no wonder that they probably had a lot more baffles than they actually needed to prevent sloshing... In fact there were some back then who wondered if stages as large as the Saturn V's could even be built and actually fly without the rocket going unstable and breaking up from uncontrollable sloshing... with early rockets like the Redstones (which were 70 inches in diameter) and even the Titans and Atlases (which were 120 inches in diameter) sloshing had to be addressed... then when the Saturn I came along and suddenly you've got a first stage made up of an amalgamation of tanks ranging from 70 to 90 inches in diameter, with an overall diameter of 260 inches, and you're building a monolithic-tank design for a six engine upper stage 220 inches in diameter (S-IV) and an even bigger monolithic-tank J-2 engine upper stage 260 inches in diameter (S-IVB), plus designs for a first and second stage for Saturn V 396 inches in diameter... well, sloshing was a considerable worry.

OF course, we've come a long way since then... we know a lot more about the behavior of propellants and sloshing and flight dynamics than we did then, control is more accurate and the guidance systems are better, reducing motions of the vehicle that induce sloshing... so it stands to reason we can get by with less slosh baffles now than we did then... PLUS, every pound of weight you reduce off the stage by reducing slosh baffle weight is additional payload (roughly 1 pound additional payload for every 10 pounds reduced on first stages, and basically a 1:1 payload to weight reduction improvement on ascent to orbit upper stages). So there's a STRONG impetus to minimize stage dry mass, and therefore to minimize slosh baffling to the extent possible...

Later! OL JR

Certainly cool stuff.

TA

thats pretty awesome

luke strawwalker said:

Here's one of the interior of an S-IVB stage as it flies to orbit and then shuts down... while the engine is burning, the liquid hydrogen is kept firmly seated on the aft dome of the tank, but when the engine shuts down, it floats off across the tank in great splattering globules that spread themselves over the quartz window the camera was looking through, which explains the distortion. Once it settles down, though, you can see great blobs of liquid hydrogen floating around inside the tank...

On "The Mighty Saturns" video from Spacecraft Films, the entirety of the Saturn I interior tank view is shown... near the end of the video, when the engines shut down and the retros fired to separate the stages, the propellant comes RUSHING back up the baffles and core toward the camera due to the negative acceleration imparted to the coasting stage, spraying the camera window with propellant.

Click to expand...

If one continued watching Sunday morning, they flipped back to the tank camera at one point as globules of LO2 were dancing and merging very near the camera.

Watched the lauch live.... didn't know what I was looking at for a while, thought... "fuel tank? I'd be pretty wary of putting a camera in there." It looked more and more like a pool of liquid as the flight progressed (and the level drained down), then... massive "wow, that's ridiculously cool" as the second stage hit MECO and the propellant globule'd up in the center.

Zeroignite said:

Watched the lauch live.... didn't know what I was looking at for a while, thought... "fuel tank? I'd be pretty wary of putting a camera in there." It looked more and more like a pool of liquid as the flight progressed (and the level drained down), then... massive "wow, that's ridiculously cool" as the second stage hit MECO and the propellant globule'd up in the center.

Click to expand...

Unless they're doing it different, the camera isn't actually IN the propellant tank-- just a "window" installed in the tank that the camera peers through... (and by "window" I mean an optically clear portal, not necessarily a "window" in the traditional sense... it could be as small as a pipe fitting equipped with a pressure sealed clear material to allow light to pass...)

Of course one COULD (I suppose) mount the camera inside the propellant tank nowdays, in a properly sealed housing of some sort... hard to imagine WHY one would do it that way though, compared to having it mounted outside "remotely" filming through a "window" into the tank... certainly from a maintenance perspective having it outside the tank is a lot easier to fix if something goes wrong...

If we put electric fuel pumps inside the gasoline tanks of all our cars nowdays, then it's CERTAINLY not impossible to mount a camera inside a rocket propellant tank... (BTW I'm no fan of electric fuel pumps inside gas tanks either...)

Later! OL JR

Love SpaceX!!!