Fire and Outgassing at Every Shuttle Landing?

[TK-8964]

Greetings!

I have emailed NASA and a few other Space Shuttle websites, with No Returned Email about my Question/s. Hopefully someone here can Help me out...PLEASE!

Best YouTube vid that I have found for a good visual example...

Right after "Wheels Stop", you can really see the Flames at a night landing. During a daytime landing, the flames are not often seen, but you can see the heat plumes.

The flames and/or heat plume located between the rear of the Cargo Bay Doors and right in front the base of the Rudder, and it happens on top of all the Shuttles.

Questions...

- What is being vented and on fire at the position mentioned above?
- What is the main purpose of this action?
- Why does the fire and venting happen while the shuttle is still flying? (Chute Open)
- If activated by the shuttle crew or automatically, how and when do they ignight it?
- Is this action stopped later after landing, or is it on fire until it bleeds dry?
- And is it shut off maunually by flight or the ground crew?

I would Greatly Appreciate any insight and/or explination!!!

Thanks,
Willy

 

[David413]

That is the exhaust of the Aux power units (APUs). It has been discussed several times on NASA TV following a shuttle landing. Google the APUs if you want answers to your remaining questions. It is a normal occurance.

 

[Urwumpe]

In some more detail:

- What is being vented and on fire at the position mentioned above?

Exhaust gases from the three APUs.

- What is the main purpose of this action?

Each APU is a hydraulic pump powered by a gas turbine. The gas turbine is propelled by hot gas produced by a small gas generator, which decomposes the chemical hydrazine into hot steam by spraying it on a catalyst bed. The still hot exhaust of the turbine is vented overboard after it had done it's purpose and driven the turbine.

- Why does the fire and venting happen while the shuttle is still flying? (Chute Open)

The APUs provide hydraulic pressure for moving the control surfaces, main engines, deploy the landing gear and invoke the brakes after landing. Each APU provides pressure for one of the three hydraulic circuits.

- If activated by the shuttle crew or automatically, how and when do they ignight it?

The APUs are started manually every time the crew needs hydraulic pressure. One is enough for operating the surfaces and allow landing the shuttle, for all critical phases (launch & landing) all three are used for safety.

- Is this action stopped later after landing, or is it on fire until it bleeds dry?

Usually stopped manually right after landing, as the hydraulic pressure is no longer required then. The last action before thus is AFAIR moving the SSME nozzles into a rain-drain position by the pilot (which requires hydraulic pressure), after opening the ET umbilical doors.

- And is it shut off maunually by flight or the ground crew?

Flight crew, more specific, by the pilot over the Panel R2 (which has all APU controls).

The ground crew can only do so, if the flight crew installed a special set of cables in the space shuttle as emergency measure, for letting the Shuttle be controlled by sending real-time commands from the ground.

 

[doggie015]

IIRC flames are not supposed to come out of the exhaust under normal conditions correct?

 

[Andy44]

I never see any flames, just heat plumes, which are visible in daylight as waves, and whch are unmistakable in the IR footage at night.

 

[tblaxland]

I've seen flames before and if I've understood my chemistry correctly, they would be from the hydrogen gas from the decomposition of hydrazine reacting with atmospheric oxygen. I don't know how hot the gas turbine exhaust is but hydrogen gas has an auto-ignition temperature of 560 deg C, so it is at least possible.

 

[Star Voyager]

According to astronaut Mike Mullane, he said as of 2005, the only landing with a shuttle on fire was STS-9, when a hydraulic line busted open.

 

[zerofay32]

According to astronaut Mike Mullane, he said as of 2005, the only landing with a shuttle on fire was STS-9, when a hydraulic line busted open.

That fire was in the Aft Compartment though, IIRC.

Zerofay32

 

[Urwumpe]

According to astronaut Mike Mullane, he said as of 2005, the only landing with a shuttle on fire was STS-9, when a hydraulic line busted open.

That is wrong. Two APUs had been on fire and even exploded around main gear touch down. That was caused by a hydrazine leak in the gas generator of the APUs, created by corrosion. The fire did not leave the aft compartment though, except the damage inside, the only indication was a "APU UNDERSPEED" warning.

 

[TK-8964]

Thanks to everyone for helping me with this thread, and the extra "Fire" events.

Thanks to David413 for defining what topic and terms to use, to find out more info with internet searches!!!

And a Huge Thanks to Urwumpe for taking the time and effort with anwsering all my questions in one post!!!

I Really Appreciate all the Help with Anwsering my inquirey, and also the Extra Shuttle "Fire" Info!

Thanks Everyone!!!

Willy Leitner
Sgt. USAF Retired

 

[Star Voyager]

That is wrong. Two APUs had been on fire and even exploded around main gear touch down. That was caused by a hydrazine leak in the gas generator of the APUs, created by corrosion. The fire did not leave the aft compartment though, except the damage inside, the only indication was a "APU UNDERSPEED" warning.

What mission was this? Were you talking about STS-9?

 

[DaveS]

What mission was this? Were you talking about STS-9?

Yes, STS-9 with OV-102, first SpaceLab mission, Nov. 1983. Landing at Edwards AF.

 

[Star Voyager]

Okay, that's what I thought. I was just going by what Mike Mullane told me.