STS-130

[scottmsg]

However, to have at least a dozen night landing missions where it has never been seen and it's only just starting to happen, well, if I was a manager or a engineer associated to the APUs, I would be asking a lot of questions.

The only thing I can think of has the APU been modified to run a different mix of fuel recently?

The APU exhaust flames were first observed on STS-51 (September 1993), which was the first night landing at Kennedy.  They have also been observed on several other flights (including STS-97, STS-99, STS-106 and STS-123) all of which were at KSC.  I'm not aware of flames being observed at any Edwards landings.  That suggests to me that environmental factors play a large part in the visibility of the exhaust.

[desktopsimmer]

I've spent over an hour this afternoon watching all of the night landing at KSC, and none of them show flames, except STS-51, STS-123, STS-130, I forgot about STS-51 so I couldn't comment about that one previously. However I've watched STS-97, 99, 106 & 123 and I could not see or there wasn't any significant flame plumes.

I'll watch the EDW ones tomorrow.

FYI A good collection of videos I've found here, just FastForward to the last minute or so:
http://www.nss.org/resources/library/shuttlevideos/index.htm

P.S. I've just been told that it could 'very' possible be due to the air around the shuttle igniting, well it is over 1000 C .

[scottmsg]

I've spent over an hour this afternoon watching all of the night landing at KSC, and none of them show flames, except STS-51, STS-123, STS-130, I forgot about STS-51 so I couldn't comment about that one previously. However I've watched STS-97, 99, 106 & 123 and I could not see or there wasn't any significant flame plumes.

I'll watch the EDW ones tomorrow.

FYI A good collection of videos I've found here, just FastForward to the last minute or so:
http://www.nss.org/resources/library/shuttlevideos/index.htm

P.S. I've just been told that it could 'very' possible be due to the air around the shuttle igniting, well it is over 1000 C .

The flames on STS-99 didn't start until well after wheel stop.  STS-97 exhaust flames were actually visible during the launch, not landing.

BTW, on the STS-9 APU fire (caused by a hydrazine leak) there was no indication of any problem from the outside.

[neosonic2k]

A quick explanation on the APU fire, taken from http://www.spaceflightnews.net/article.php?story=20080329144436610

"As the crew worked through safing and power-down procedures on the runway, flames of exhaust could be seen shooting up from each side of the Shuttle's tail. Initially startling viewers in person and television, the exhaust came from vents at the base of the tail for the auxiliary power units.

The APU's burn noxious hydrazine to provide power to the landing gear, speed brake and elevons, as well as repositioning the main engine nozzles after landing. The exhaust is vented by the tail and during daylight is barely noticeable. Even at night, the exhaust isn't very bright, but conditions this time accentuated the brightness of the flame and startled many observers.

A similar event occurred after STS-9 when the APU venting was more prominent than after the 8 previous flights. On that flight, however, there actually was a small fire that broke out in one of the APU's. "

So, yeah. It was brightened due to the weather (wind, temp, humidity, etc). That's why Houston PAO didn't even care about it for a while. Besides, think about it... if no one went around screaming "OMGFIREEEEE!!!!!!!!!!!" or the NASA equivalent of said statement, "Houston, we have a problem" (this isn't the exact quote... it just sounded more dramatic to "Apollo 13"'s director), then this must be perfectly normal.

Welcome home, Endeavour! Up next, Discovery!!!

[desktopsimmer]

BTW, on the STS-9 APU fire (caused by a hydrazine leak) there was no indication of any problem from the outside.

Luckily it burnt itself out, and only discovered when the recovery crews were checking the aft section. It made a mess of the compartment.

Still find it bizarre, not in a panic sense, but as a sense of curiosity, that there are cases were the APU heat plume will not appear, but rare cases it will. I found some landing environmental data (wind speed, temp, pressure and humidity) between a non-flash to a flashed one and there is very little difference, maybe just enough to make the plume visible

The only thing I can think of is either unspent hydrazine, unlikely but possible (a bit like a backfire), or the air around the exhaust vent combusts under the exhaust temperature. Is the reason we see it as yellow flame because it's reaction with oxygen in the atmosphere?

[Dee-Jay]

STS-130 Ascent Highlights 

http://www.nasa.gov/multimedia/nasatv/on_demand_video.html?param=http://mfile3.akamai.com/18566/wmv/etouchsyst2.download.akamai.com/18355/wm.nasa-global/STS-130/sts130_ascent.asx&_id=224368&_title=STS-130%20Ascent%20Highlights&_tnimage=427933main_sts130_ascent_100.jpg

[desktopsimmer]

On Topic
Looking at view pictures of the mission, I noticed that there was someting  between the pilot/cmdr and the payload bay window. It's not another HUD. is it some kind of visual guide, or transparent check list?

http://upload.wikimedia.org/wikipedia/commons/1/13/STS-130_Endeavour_Rendezvous_Pitch_Maneuver_aft_portion.jpg

Off Topic......
After a lot of reading (including SCOM and an article about Hydrazine reactions), the visible flame is the air in between OMS pod and the tailfin igniting due to the extreme temperatures from the exhaust vent. If I understand this correctly, this is basic operation of the APU. Please correct me if I'm wrong:

As the Hydrazine enters APU and it reacts with the Shell 405 catalyst, becoming a very hot gasous format, expands and produces/converts onto nitrogen, hydrogen and ammonia. The hot gas then shifts (at some rate) into the turbine which rotates turns the gearbox, which turns hydraulic pumps, which makes the control surface work. Meanwhile, the hot gas escapes via the exhaust pipe, at 1000C and upon exiting it might ignite with the air.

[ssjfb]

On Topic
Looking at view pictures of the mission, I noticed that there was someting  between the pilot/cmdr and the payload bay window. It's not another HUD. is it some kind of visual guide, or transparent check list?

I think you can find the answer just at the beginning of this video :
http://www.youtube.com/watch?v=xCNpFNi8IMU

In front of aft windows, astronauts have a kind of monitor. On the picture you described, you see the open screen of this monitor with a kind of brightness (that's why it seems to be transparent).

[Admin]

OK gang. STS-130 is over, posts starting to slowly drift away. Time for a tactical thread lock.

/Admin