SITIS Archives - Topic Details
Program:  SBIR
Topic Num:  AF071-108 (AirForce)
Title:  Pavement Material for Joint Strike Fighter (JSF) Vertcal Takeoff and Landing (VTOL) Operations
Research & Technical Areas:  Materials/Processes

  Objective:  Develop a pavement material upon which the JSF can perform frequent, prolonged VTOL operations without affecting the aircraft or significantly degrading the operating surface.
  Description:  The introduction of the new weapon system will bring new environmental effects that are harsher than legacy systems (such as USMC AV-8B), particularly on the pavement areas upon which VTOL operations will be performed. There are concerns that during VTOL operations, the combined effects of exhaust gas mass flow and temperature will cause spalling of a traditional concrete operating surface and may rapidly degrade the surface to an unusable condition. Due to the high airflow rates from the aircraft exhaust, any loosened material would then present a significant foreign object debris/damage (FOD)* hazard. FOD hazards can lead to damage or destruction of the causing aircraft, nearby aircraft, and/or equipment. In addition, FOD generation has the potential to harm personnel. Therefore, a new, durable and low-cost material or method is required that can be substituted for or retrofit existing concrete in the pavement areas used particularly for VTOL training (initially at Eglin AFB and then subsequently at other military bases). The material must be able to withstand, without damage or deformation, the heat, airflow and landing gear load stresses imposed during VTOL operations and also be able to provide a lasting nonslip surface that is unaffected by water, oils, lubricants, or any other natural or synthetic compounds likely to be present in a fighter operating area. The material must be able to perform equally in arctic, temperate, desert, or tropical environmental conditions. Thresholds that the material must withstand based on typical induced loads are as follows: Exhaust gas temperature 1800F or higher Exhaust gas pressure 36psi or greater Exhaust gas scrubbing velocity 1000ft/sec or faster Time duration for typical maximum intensity exhaust gas exposure 15sec per landing/take-off Undercarriage load 52000lbs through a 100 square inch tire patch at 255 psi (pressure distribution over the 100 square inches is not expected to be uniform) *FOD = Foreign Object Debris/Damage; A collective term used that signifies a potential hazard to aircraft operations due to the presence of loose articles within the vicinity of aircraft. The loosened pavement material could be ingested by aircraft engines, blown around at high velocity by aircraft exhausts, or fall into places it could jam aircraft controls, all of which might lead to hazardous consequences.

  PHASE I: Evaluate materials and methods (either new developments or modifications of existing materials) that offer potential to meet the requirement. Test specimens to show the likely operational limits for temperature, blast and mass loads related to VTOL operations. Estimate production costs.
  
  PHASE II: Develop a selected material from Phase I. Show full suitability for VTOL operations, including exposure to repeated heat/load stresses and prolonged natural and induced environmental exposure. Design criteria, life-cycle cost data and an estimate of the anticipated production costs for the proposed material will be provided. Construct a large-scale pad to be tested under actual engine loads.

  DUAL USE COMMERCIALIZATION: Military application: Runways and taxiways that will operate VTOL aircraft and/or require heat-tolerant pavement surfaces. Commercial application: Commercial airport runways and taxiways that require heat-tolerant pavement surfaces.

  References:  1. Robins, P.J., Austin, S.A., and Richards, M.R., "Resistance of steel fibre concrete to VTOL engine jet blast," Cement & Concrete Composites, 1994, Vol. 16, No. 1, pp. 57-64. 2. Austin, S.A., Robins, P.J., Richards, M.R., "Jetblast temperature-resistant concrete for Harrier aircraft pavements", Structural Engineer, 1992, Vol. 70, No. 23-24, pp. 427-432.

Keywords:  heat-resistant pavement material, high-stress concrete, spalling from high heat, non-slip pavement material, temperature resilient concrete

Questions and Answers:
Q: Is concrete the only acceptable material for the pad?
A: No, you are not restricted to concrete.
Q: 1. I would like to better understand the terms of the jet-blast gas pressure. It is measured at the nozzle exit point or at the pavement touch-down?

2. If the exhaust gas scrubbing velocity is required to be 1000 ft/sec what will be the size of the gas stream, to be measured as ft3/sec?

3. I would also like to understand the effect of dust or mist droplets over the pavement surface and the existing concentration of such particulates and droplets within the gas stream.

4. I would also like to know to whom we should address the materials specimens, which entity is willing to look into this and if you can, please let us know to whom we should speak with for getting current specimens to compare them with our trials. We would like very much to work together with an authority in charge of making such runways and taxiways, especially if we must build a large-scale pad to be tested under actual jet-blast loads.

5. It is important for the pavement material to have good thermal conductivity?
A: 1. The temperature of 1800 degree F is measured at the nozzle. The temperature at the pavement surface can be as high as 1400 degrees F.
The velocity of 1000 degrees F is at the velocity at the nozzle. The pressur eof 36 psi is on the pavement.

2. The mass flow rate is 1768 lbm/s. The flow rate in cubic feet per second is a function of the density of the jet exhaust. We are gathering that info and will post it as soon as it is available.

3. The gas stream is 1400 degrees F there is little if any water droplet in the gas stream. The dust is a function of the environment. The major problem with most of the existing materials is the generation of FOD due to spalling caused by the extreme thermal environment caused by the VTOL operation. The FOD generated can be easily ingested by the the aircraft intake.

4. AFRL/MLQD will manage the project. All specimens and reports will be submitted to AFRL/ MLQD, Tyndall AFB, FL 32403. We may be able to provide some 6 inch diameter cores from some existing runways; however, these are limited. If you require larger specimens than you will need to plan to prepare them yourself using the current design criteria and design specifications used in Airfield pavement construction. You will not be require to construct a large scale pad as a part of the phase I and is not required as part of the proposal.

5. It is up to the applicant to propose which characteristics are most desirable and applicable to their solution methodology. It may be desirable in one methodology to have a material with a high thermal conductivity; however, another approach may require a low thermal conductivity to be effective.
Q: I was wondering if you could tell me how big the pavement opportunity for the JSF and vertical take-off vehicle might be. A ballpark guess will be more than adequate.
A: Each Pad is 96' by 96'. There will be several pads at each base using this aircraft. This could be as many as 200 bases by 2013. If the solution is ecomical and applicable to other heat related problems associated with this and other aircraft then the size of the area to be treated could become approximately one million square yards per base.
Q: Is concrete the only acceptable material for the pad?
A: No, you are not restricted to concrete.
Q: 1. I would like to better understand the terms of the jet-blast gas pressure. It is measured at the nozzle exit point or at the pavement touch-down?

2. If the exhaust gas scrubbing velocity is required to be 1000 ft/sec what will be the size of the gas stream, to be measured as ft3/sec?

3. I would also like to understand the effect of dust or mist droplets over the pavement surface and the existing concentration of such particulates and droplets within the gas stream.

4. I would also like to know to whom we should address the materials specimens, which entity is willing to look into this and if you can, please let us know to whom we should speak with for getting current specimens to compare them with our trials. We would like very much to work together with an authority in charge of making such runways and taxiways, especially if we must build a large-scale pad to be tested under actual jet-blast loads.

5. It is important for the pavement material to have good thermal conductivity?
A: 1. The temperature of 1800 degree F is measured at the nozzle. The temperature at the pavement surface can be as high as 1400 degrees F.
The velocity of 1000 degrees F is at the velocity at the nozzle. The pressur eof 36 psi is on the pavement.

2. The mass flow rate is 1768 lbm/s. The flow rate in cubic feet per second is a function of the density of the jet exhaust. We are gathering that info and will post it as soon as it is available.

3. The gas stream is 1400 degrees F there is little if any water droplet in the gas stream. The dust is a function of the environment. The major problem with most of the existing materials is the generation of FOD due to spalling caused by the extreme thermal environment caused by the VTOL operation. The FOD generated can be easily ingested by the the aircraft intake.

4. AFRL/MLQD will manage the project. All specimens and reports will be submitted to AFRL/ MLQD, Tyndall AFB, FL 32403. We may be able to provide some 6 inch diameter cores from some existing runways; however, these are limited. If you require larger specimens than you will need to plan to prepare them yourself using the current design criteria and design specifications used in Airfield pavement construction. You will not be require to construct a large scale pad as a part of the phase I and is not required as part of the proposal.

5. It is up to the applicant to propose which characteristics are most desirable and applicable to their solution methodology. It may be desirable in one methodology to have a material with a high thermal conductivity; however, another approach may require a low thermal conductivity to be effective.
Q: I was wondering if you could tell me how big the pavement opportunity for the JSF and vertical take-off vehicle might be. A ballpark guess will be more than adequate.
A: Each Pad is 96' by 96'. There will be several pads at each base using this aircraft. This could be as many as 200 bases by 2013. If the solution is ecomical and applicable to other heat related problems associated with this and other aircraft then the size of the area to be treated could become approximately one million square yards per base.

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