NIRAD Data Package for the NASA WB-57. N on-dispersed I nfra R ed A irborne CO 2 D etector (NIRAD). Prepared by Darin Toohey University of Colorado, Boulder April 2004 Updated March 2005.
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NIRAD Data Package for the NASA WB-57
Non-dispersed InfraRed Airborne CO2Detector (NIRAD)
Prepared by Darin Toohey
University of Colorado, Boulder
Updated March 2005
1. Payload Description
Measurement: Carbon Dioxide (CO2)
Method: Non-dispersed infrared absorption spectroscopy relative to a reference gas with known CO2
Instrument Details: Right wing pod, 66.5 lb, 10”x24”x14” (lwh), <250 W (28V aircraft power at <10 A)
Sampling frequency: 10 Hz
Accuracy: < 0.1%
Precision: <0.03% at 10 Hz, <0.01% at 1 Hz, < 0.003% at 10 seconds
NIRAD consists of three systems: (1) CO2 detector, (2) power and data acquisition, and (3) gas-handling. All three systems have flown previously. The CO2 detector was first flown in 1999 as part of CORE+ instrument during RISO and ACCENT and again in 2004 during PUMA-A. There have been no changes to the detector, other than inspection and routine maintenance. The power and data acquisition system were new for PUMA-A, and are flown here without change, other than to software. The gas-handling system is the same as that flown in May 2004, except that it is now packaged into a single box that contains the detector and power/data system.
The detector is packaged in a vacuum housing to facilitate management of temperature and pressure. At power-up the housing is pumped down to ~300 hPa by one stage of a diaphragm pump and held at this pressure throughout the flight. Thus, at pressure altitudes < 300 hPa the pressure within the housing is above ambient. By design, if the pressure differential is significantly greater than about 5 psi, the O-ring seals leak. A redundant additional mechanical safety relief valve (set for ~15 psi or less) is placed on the housing.
Two 1.2 L epoxy-coated, fiber-wrapped aluminum bottles (DOT rated and certified) are filled to ~1600 psi before flight with zero air doped with CO2. These ‘standards’ are sampled repeatedly during flight to provide an accurate standard for reference to the NOAA/CMDL CO2 scale. Two-stage regulators provide a service pressure of ~25-30 psig throughout flight. The bottles and regulators are backed with safety relief valves.
The diaphragm pump is current-limited for a ‘soft start’ (that is, there is no electrical surge on startup, allowing for use of compact, highly efficient Vicor VI-100 DC/DC converters.
LiCor electronics and pressure controllers
100 W rating
Pressure gauges and controllers
100 W rating
Computer + A/D System
2. Structural Analysis
(a) Itemized weight
ComponentWeight, kgWeight, lb
MKS 248 Control valve0.541.2
gas standard 1w/relief valve1.603.5
gas standard 2 w/relief valve1.603.5
PC-104 computer stack0.601.3
dc/dc converter 10.100.2
dc/dc converter 20.100.2
gas regulator 1w/relief valve1.002.2
gas regulator2 w/relief valve1.002.2
cables, gas lines, fittings2.164.4
frame, structure, covers9.5521.0
Total30.23 kg66.5 lb
2. Structural Analysis (click on Excel spreadsheet for supporting calculations)
There are two structural issues to consider for integration of NIRAD into the wing pod of the WB-57. The first issue involves the mounting of the individual components listed on the previous page into the box, the second involves mounting the box to the rack. These will be dealt with separately below.
1 - Mounting of individual components into the instrument box
Due to small masses, nearly all components are mounted within the respective housings with high safety margins (factor of 10 or larger). The component with the lowest safety factor is the diaphragm pump, which weighs 10 lbs and is mounted with four #10 stainless steel bolts to a 1/8” thick aluminum plate that forms the bottom of the box. Viton rubber sheets are used between the lugs of the pump and the plate to dampen vibration, although the Vacubrand pump used here was selected for its extraordinarily low vibration. The bolts are secured into locking captive washers (cinch nuts).
Structural analysis shows that all loads have safety margins of x5 or larger, the lowest being the vertical (up) load plus horizontal (forward/aft and left/right) overturning moments (margin = 10). Thus, it is determined that the pump is safely mounted to the box, and that all other components, which are smaller and lighter, do not represent safety issues.
2 – Mounting of box and frame to rack
The instrument box is mounted to the rack with six #10 cadmium coated, stainless steel bolts. Structural analysis shown in the accompanying excel file indicates that the lowest safety margin (380-480%, or a factor of nearly 5 over nominal ratings) is for the flange bending (vertical load plus horizontal overturning moments). Flange shearout has a safety margin of over 700%, and all other margins are at least a factor of ten over nominal ratings.
Values based on measurements in lab and estimates of pump performance versus pressure
115 VAC 60 HZ (Single Phase)
115 VAC 400 HZ (Single Phase)
115 VAC 400 HZ (Three Phase - A)
115 VAC 400 HZ (Three Phase - B)
115 VAC 400 HZ (Three Phase- C)
3. Electrical Load Analysis
Maximum value will occur on ascent, immediately following power-up, where the pressure is largest and temperatures are lowest. This is due to loading of diaphragm pump and heaters. Nominal current draw will depend on cruise altitude – lower values pertaining to highest altitudes
Momentary (< 0.1s) surges of ~0.3 A may occur due to valve switching at ~120 second intervals
4. Pressure/vacuum systems
5 psig safety relief valve
Normally closed valves
Vent to box
Housing pressure determined by this feedback loop
5. Laser systems - none
6. Hazard Source Checklist
X - Rotating device
The diaphragm pump consists of a rotating armature driven by brushless 24 VDC, and small flywheel to reduce vibration. Friction in the diaphragms is sufficient to stop rotation within a few seconds of power loss.
N/A - Extendible/deployable/articulating experiment element (collision)
N/A - Stowage restraint failure
N/A - Stored energy device (i.e., mechanical spring under compression)
Vacuum vent failure (i.e., loss of pressure/atmosphere)
N/A - Heat transfer (habitable area over-temperature)
N/A - Over-temperature explosive rupture (including electrical battery)
N/A - High/Low touch temperature
N/A - Hardware cooling/heating loss (i.e., loss of thermal control)
N/A - Pyrotechnic/explosive device
X- Propulsion system (pressurized gas or liquid/solid propellant)
Gas bottles and regulators, as described above. The bottles are clamped to a ½” thick 2024-Al machined plate surrounded by a 1/16” thick aluminum housing and bolted to the rack within the wingpod via the Al plate. The largest diameter tubing maintained at high pressure is ¼” stainless steel contained within the bottle housing. The force of any inadvertent release of pressure is smaller than the safety margins for structural components in this same housing (e.g. bottle and regulator).
N/A - High acoustic noise level
N/A - Toxic off-gassing material
N/A - Mercury/mercury compound
N/A - Organic/microbiological (pathogenic) contamination source
N/A - Sharp corner/edge/protrusion/protuberance
N/A - Flammable/combustible material, fluid ignition source (ı.e., short circuit; under-sized wiring/fuse/circuit breaker)
N/A - High voltage (electrical shock)
N/A - High static electrical discharge producer
N/A - Software error or computer fault
N/A - Carcinogenic material
8. Hazardous materials – none
9. MSDS – n/a
10. Mission procedures