Irregular Pulse After Shuttle Landing

I can't view the footage but the intro picture shows some tip vortices (spiral forms at wing tips) that may explain what you are seeing. Low pressures caused by the vehicle upper surface aerodynamics may be causing the air to condense locally. This can occur briefly in localised regions of air as the shuttle goes through them at high angles of attack. You see it often on passenger aircraft.

Does this explanation sound plausible?

No modelaer, that is not what is shown. Sorry you can't see the footage, Ky.

Smoke emission quantity is suspiciously synchronized with bulb light , so it's consistent with a high intensity discharge type bulb with a broken glass. It's electrodes would emit light (not for long) even at oxygen containing atmosphere, and the smoke should be tungsten oxides forming. Well I would prefere a reused bulb at launch than a reused tire.(LOL) Just a guess. S.M.

Or just illuminating the condensation?

Nothing much of synchronization to be see. If it would have been regular I would have not even noticed. What is the gas, steam that is being vented, flared off, and why not in one burst?

You're off to a good start!

Welcome.

I did have a look and know a bit about APU's. Again, whatever is happening it does not seem very regulated but more irregular in timing and flame signature.I'll better have another look and check on the light source.

The "irregular" period of these bursts is actually a very subjective attribute. You (Ky) clearly do not see an understandable periodicity to these flares. That does not mean that there is not a reasoned pattern to these bursts (pressure and trip hysteresis combined with anticipated skin temperature). The human perspective is poor at identifying a truly random (chaotic) pattern.

_{This answer should be considered a GE response from me, Guinness Enhanced. (hic)}

You are right. I now understand that the pulses are governed by a computer which reacts in accordance with what the skin tells it to do.

When I was experimenting with dual fuels I relied completely on sound and sight and the consequences were that I recognized that even my abilities to correlate from those were stretched and not reliable.

I knew when to turn off the "engine" when it all started to make noises and flames which didn't sound healthy. They were very similar to the shuttle images. Besides, my neighbors were getting a bit nervous about what I was doing.

Speculation is setting in, I'll refrain. Have a couple on me, Ky.

I think it was responding to the pilots pumping the breaks and moving the controls for the last time. Each action required additional power from the APU.

I thought it was breaking the pumps but I get it frack to bont all the time

I don't know for sure what is happening with the shuttle in those pictures but I'll hazard a guess. With the imaging switching between visible and infrared light cameras, I suspect that what you're seeing is the safe burning of remaining thruster control fuel. This may not be visible with daylight landings, which is why this seems to be a new image to you. As I said, this is just a guess on my part.

avasco73 has it right; APU venting.

Here is a short article. I was hoping to find a more complete explanation . Sorry.

You are right, APU venting it is. But why so irregular? I would imagine that a steady venting or at least a reliable pulse would end such an incredible journey made by such a perfect piece of machinery. I just can't see it as something coincidental, there must be a reason for the pulse, pulse pulse, pulse. Looks more like Morse code than controlled venting. I'm nearly over it, Ky.

I saw that too... I think the image was in IR mode what I saw, which suggested that the plume was as much thermal as it was mist, steam, smoke, or flame.

I would think it is a pressure relief valve, and that for various reasons, the interval between relief ventings is subject to the 'chaos' of multiple variables, and therefore not uniform in sequence.

chris

Thanks Chris

Yeah, the randomness of it all, in such a perfect system, is exactly what made me wonder. All systems on off and it's still thumping away. You know what I am really thinking but speculating in CR4 in a big no-no for me. Give me a couple of more years and I might try

How was your trip?

In that excellent and through link provided in #4 (GA)

(about 2 screens down, in outlining control logic)

"The frequency and duration of the primary fuel control valve pulses are a function of the hydraulic load on the unit"

I.e. it's a 'instant demand' based system.

So what you are seeing is throttle and mixture changes as it powers up or down with the activation of the range of avionics loads.

Not 'random' or 'irregular', as such, just driven by activities not readily apparent.

thats what I meant by many 'variables' appearing chaotic... valves and such like thingies

I understand now. I am happy about the comments made by all and have done some further reading myself. CR4 is just great and gets these questions out of ones system without much delay and in a friendly tone.

, Ky.

Nice..

I could close my eyes and throw darts and and come up with many more misleading and downright ignorant thread titles than this. But, my monitor's not dart proof.

I admit that I first thought that we were talking about a medical condition. Then I saw the irregular pulse. He wasn't talking about heart beats.

I hope that this "stupid question" is not going to turn into a medical condition for me.

I didn't think it was stupid, at all. Especially after watching the video.

You are right. What I know of EPU's doesn't correspond with what is shown in the clip. The whole unit is so tightly organized that something as irregular as this pulse seems to be a bit odd. If I were in control, TG I'm not, I would try and rectify this even if it would be only something cosmetic.

I have seen this before but always thought they, NASA, would know what they are doing. I even thought it might have to do with getting rid of the parachute but by this time it is laying on the tarmac. Wish I could have one of those as a pool cover and I bet that's were they end up in some cases .

It's not just something that escapes my eyes and I am surprised that there isn't a straight forward answer. It's still early days and the explanation is possibly quiet simple. See what happens, Ky.

Well,

It is, after all, moot. The shuttle will never land again with APU's running.

Moot it is. I know now what it is after surfing the net, just the irregular pulses are still a mystery.

Simple. It has attitude rocket nozzles all over it. These, in order to be absolutely reliable work with a monopropellant (oxidizer and fuel in one). When that hits a platinum catalizer in the rocket chamber, it burns, reliably. It only takes a valve to make it work.

After landing, the heated and expanding, slightly poisonous liquid's gases needed to be vented. The ground crews approach the lander only after some 30 minutes in moonsuites and gas sensors, before opening the doors for that reason.

Landing videos are edited. Nobody cares to see no activity around the lander for long.

"attitude rocket nozzles"

Why didn't I think of that as a title?

The shuttle doesn't have a traditional APU, but rather, a unit using hydrazine (very nasty stuff) driving a turbine. My guess is that you are seeing the flame, or thermal signature of a flame, from that and it's subsequent venting. I am not sure why it pulses.

I would think that the exhaust of the APU would not go straight out of the ship because in space there would be total vacuum on the outside. That would make it necessary to alter the normal way of exhausting gasses. It could be that the exhaust vents into a chamber that has a control valve that opens when there is sufficient exhaust to vent.

The APU's are not operated when the shuttle is in orbit. Directional control is maintained with thrusters, since there's no air for the control surfaces to act against.

It looks to me like the Shuttle is venting some sort of gas!.....Or maybe built up heat.

This current shuttle program status begs some questions with me in terms of its termination.

The shuttle program is now over, leaving the US with no alternative "rides" to get into space, or the ability to retrieve its people from the Space Station. While I am sure the Russians are capable of filling this need, I can't get my head around the fact that NASA would abandon this program without an alternative. I am wondering (no I am not paranoid) if the US if fact, has a ride available that is secret, that they could use in a pinch to get into space and have a presence there. Right now they only have rockets that can spew sat's into space. Doesn't fit with the previous American committment to being number 1 in the industry. What is your thoughts on this. I am flabbergasted. Santa is their only current option as far as I know.

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I saw this & said to my wife that i hadn't noticed it before, the only explanation I could come up with is that it is an on board generator for power.

All in all great informative thread, thanks for asking the Question KY, awesome to learn somthing new today.

Yeah, same here Mate. I wanted to ask that question since some time now but thought I'll come up with an explanation on my own. I am fully satisfied and maybe I should ask more questions that can't be googled or only answered there in a cosmetic way.

The CR4 "Gang" is the best thing since sliced bread for me and I think for many others as well. Thanks again to all for giving me a better understanding of the matter. Back to the drawing board it is, I'm on the case, Ky.

I'm guessing it could be a relief valve alternately letting off pressure and reseating until the pressure builds back up again. This can be sporadic (roughly but inconsistently periodic), as in the video.

that sounds vaguely familiar...

"vaguely" as in 'skipped #4 too'?

i did'nt have time to read all the cooments. has anyone suggested residual ionizatiion?

No.

If you find the time have a look at the video. It's dark most of the time but towards the end one can see the light

Residual Ionization? If that goes on for half an hour, and longer, there must be heaps of whatever was ionized. I am sure the above explanations are sufficient to explain "The Pulsing".

Again thanks to all, Ky.

The flames are hydrazine venting and burning off.