# Presentation: 384557

## NASA Fire-Prevention Update

- International Aircraft Systems Fire Protection Working Group
- by
- Clarence Chang & Bob McKnight
- NASA Aviation Safety Program (AvSP)
- Fire-Prevention Element Leader
- March 26, 2003
- Phoenix, Arizona

**Notes:**
Clarence Chang – Bio
NASA Glenn Research Center 

Clarence Chang is NASA Glenn Research Center’s Aviation Safety Program Level-3 element leader. He currently oversees sub-elements in OBIGGS/OBOGS, fire-safe fuels, fire-detection sensor and modeling. He worked on aero-propulsion projects in gas-phase mixing, spray combustion, emission reduction, and is currently working on active combustion control. He is a mechanical engineer and holds a BSE from University of Pennsylvania and MS and Ph.D. from MIT.

## Quick 5-minute briefing

- Aviation Fire / Fuel Security Workshop
- State of the NASA OBIGGS/OBOGS contract
- Alternate OBOGS technology leveraging
- Fire-safe fuel research status

## Aviation Fire / Fuel Security WorkshopMarch 11-12, 2003, Alexandria, VA

- Scenarios: Shoe bomb, API sniper round through tank, MANPAD
- Technologies: Fuel foam, solid polymer fuel, active suppression
- 	            reticulated foam, inerting, MCK, metal mesh
- Board evaluation of ideas to help NASA sort out technologies for
- security program from FY04-07.
- Security program
- 	Aircraft Hardening
- 		Fire Prevention:  1 to 2 M /yr funding:

**Notes:**
A workshop on Aviation fuel system security was held in Alexandria, VA on March 11-12, 2003. This workshop was jointly sponsored by FAA, NASA, and TSA to look at ideas that may be usable by the TSA to promote fuel system security. The specific scenarios deals with ignition threats from armor-piercing incindiary (API) rounds passing through the ullage gas and igniting the fuel vapor, hydro-dynamic ram setup by the bullet passing through the liquid fuel, a shoe bomb placed above the center wing tank, or a near-miss by a MANPAD that resulted in shrapnel damage.

The ideas presented were using air bubbles inside the fuel to reduce pressure effect from hydrodynamic ram of passing projectiles. And additive in the fuel also causes the fuel to foam so that even if an API round ignites the ullage gas, the flame is snuffed out by the foam.

Another idea is to use polymer such as polyethlyene was as fuel. The polymers are solid and therefore has dual use for protection against terrorist or controlled crashes.

Walter Kidd company presented active fuel tank suppression.

Foamex presented the use of reticulated foam to snuf out ignition as is used in C-130 tactical transports.

Dick Hill presented the use of fuel tank inerting to suppress ullage ignition.

JPL presented their resurrection of the AMK program (renamed MCK).

And a presentation on live-fire test of metal meshes in fuel tank.

The evaluation board will sort out their thoughts and put together a report for NASA and TSA to use in formulating their security programs.

Current NASA Security program planning has a sub-element “Aircraft Hardening” and the Fire Prevention element will be listed under here. The estimated funding level is about 1 to 2 million a year.

## OBIGGS/OBOGS Program Status

- Retarget from B757-200 to B737-700
- 6-month feasibility study finishing on 3/26/03
- No new technology entrant:
- Higher-Temperature membranes
- System-level performance improvement
- Oxygen waste stream for emergency-cruise breathing
- Phase II evaluation and selection by 4/26/03
- Enough funding for 3 of 4 proposed Phase II contracts

**Notes:**
At the end of last September, NASA selected four vendors to study the feasibility of means of increasing the performance of gas separation technology for fuel tank inerting, cargo compartment fire suppression, and emergency breathing oxygen. 
However, part-way through the work, our FAA colleagues obtained a B737-200 aircraft which they have offered to us for testing our new systems. Taking advantage of this opportunity, we have resized our technology test beds from the B757—200 to a B737-700. The –200’s bleed air system is a reasonably similar to that of a more modern –700, so that the contractors can directly apply the lessons they learned to future prototypes. This change is more challenging to the contractors. For even though the inerting requirement is reduced by 50%, the bleed air and electrical supply is reduced by 2/3.

This 6-month work will end at 3/26/03. An evaluation panel will look through the Phase II work plans and the Phase I final report and choose three to fund during Phase II hardware build up. There were other parties other than the original four selected for Phase I who had expressed interest in entering into the Phase II selection. However, no significantly new technology have appeared to warren inclusion into this existing selection pool. The current work area still are the higher-temperature membranes to improve diffusivity and selection, and the utilization of waste oxygen stream for emergency breathing.

We expect the selection results to be available by 4/26/03.

Our current funding is stable. Therefore, we are still on target to fund three of the four current projects.

## Alternate OBOGS Application

- Currently no suitable means for OBOGS to satisfy surge load
- Surge load requires some form of stored oxygen
- Higher-altitude emergency cruising (20-25kft) requires better membrane selectivity or PSA-type enrichment
- Enriched oxygen for hybrid fuel-cell APU
- All-electric airplane requires larger electrical load
- Electrical generation from more efficient fuel-cell
- Oxygen-enriched waste stream increases power density
- Lower pollution -- Clean APU exhaust
- Contact Clarence Chang at 216-433-8561
-                               Clarence.T.Chang@nasa.gov

**Notes:**
First, the issue with OBOGS is that the surge load is the driving factor. Our current specification calls for high-purity oxygen delivery within 30-seconds of activation, assuming some form of oxygen storage is available. However, the oxygen consumption rate at normal cruise-altitude is much higher than what a combined OBIGGS-OBOGS sized for fuel-tank inerting can make. So even if high-purity oxygen can be made, sizing the system for the oxygen surge load will make the system over-sized. As a result, it may be better just to extend that 30-second surge load to a longer period using stored oxygen until the OBOGS can take over at intermediate altitudes. 

Secondly, the oxygen concentration from the OBIGGS waste stream limits the emergency cruising altitude. So unless the membrane selectivity increases with the typical bleed air supply pressure, the oxygen concentration for a simple single-stage process is only around 30%. This limits the useful cruising altitude of the aircraft using this waste gas to supply breathing oxygen to the occupants. So if OBOGS is used to extend the emergency cruising altitude and hence the range, membrane selectivity much be increased to produce high oxygen concentration.

We had previously three applications for a OBIGGS/OBOGS gas separation system: fuel tank inerting, cargo compartment fire suppression, and emergency breathing oxygen. NASA recently identified a fourth application: enriched oxygen for hybrid fuel-cell APU. 

The recent move to consider all-electric airplane opens up the need for a full-time operating APU to generate electrical power. In this concept, the engines would only provide bleed air but no electrical power. All electrical power would come from the APU. This requires the thermal efficiency of the APU to be as high as possible. NASA currently has an internal project on a hybrid fuel-cell APU that has a thermal efficiency greater than 50%. This cell would catalytically crack jet-A and then reform it into a hydrogen-rich mixture. But the oxidizer side of the fuel cell still uses hot air. We can use this oxygen-enriched OBIGGS stream to feed the fuel-cell, thereby increasing its power density.

## Fire-Safe-Fuels Research Status

-      energy ignition tests
- 	– level-field for world-wide fuel test comparison
- 	– coordinating effort with FAA and DoD
- Establish a surrogate Jet-A blend from pure substances
-      for ignition-reduction additive testing.
- Raise flash point another 20 F
- Contact Marty Rabinowitz at 216-433-5847
-                     Martin.J.Rabinowitz@nasa.gov

_***Fire-Safe-Fuels Research Status***_

**Notes:**
The second half of our fuel-tank safety work is to look at how to make fuel that are safer in storage. We have just recently finished our round of low-energy ignition testing to look at establishing a methodology on how ignition tests should be done in order to control the uncertainties in the result. Marty Rabinowitz will be sharing his recent findings with you later. This allows fuel ignition tests done anywhere in the world to be comparable directly. We are currently coordinating our effort in this area with the FAA and DoD.

We have a ongoing work on establishing a surrogate Jet-A research fuel to make ignition-suppressing fuel-additive testing comparable. Our objective is to raise the flash point another 20 F.