JPL plans cleanrooms for Mars and solar system exploration
At Caltech`s Jet Propulsion Laboratory in situ instruments lab, interplanetary satellites and instruments will be built and tested in cleanrooms for real-time testing of planetary atmospheres.
By Susan English-Seaton
At the foot of the San Gabriel Mountains, 12 miles north-east of Los Angeles, Caltech`s Jet Propulsion Laboratory in Pasadena, CA, is developing an in situ instruments laboratory dedicated to solar system exploration, including Mars and Jupiter. The new facility — the two-story In Situ Instruments Laboratory — will encompass approximately 11,000 sq. ft. of space and will include physical and chemical measurement laboratories and an assembly cleanroom capable of operating at Class 10,000. The planned facility is designed to take instruments through all the various phases of R&D, from assembly to installation into the interplanetary vehicles that will perform the in situ or real-time testing on planet surfaces. The $5 million project, which will be executed by La Canada Design Group, is scheduled for completion in the year 2000.
Managed for NASA by the California Institute of Technology, the Jet Propulsion Laboratory is the lead U.S. center for robotic exploration of the solar system. JPL spacecraft have visited all known planets except Pluto (a Pluto mission is currently under study for 1998 or 1999.) In addition, JPL manages the worldwide Deep Space Network, which communicates with spacecraft and conducts scientific investigations from its complexes in California`s Mojave Desert near Goldstone; near Madrid, Spain; and near Canberra, Australia.
The In Situ Instruments Laboratory will produce instrumentation and systems for landing on bodies in the solar system — planets, planetary satellites, asteroids and comets — to perform scientific studies of their properties. Currently, Mars and Jupiter`s moon, Europa, are attracting intense interest as possible habitats for extant life. Where previous missions sent spacecraft to the vicinity of such bodies, studying their properties from a distance by remote observational instruments, the instruments developed by the JPL will actually be placed on the surfaces or in the atmospheres of the bodies being studied. These in situ missions, planned for early in the next century, will require a facility where small co-located teams can assemble, calibrate, and test flight systems for delivery and deployment on these remote bodies.
The instruments that will be tested and calibrated at the JPL will perform on-site testing of the atmospheres and soil samples, rock samples, etc. and report the findings back to Earth via radio transmission. Contamination concerns include not only particulate, but biocontaminants, such as surface oils from the skin and contaminants that could offgas in space, carried aboard the satellite on the instruments. In space, the oil vaporizes, and because vapor pressures are much different than those on Earth — or even non-existent — any contamination on devices would skew test results. In addition to cleanliness, because of payload size, miniaturization is an important factor in the success of the work, says architect Veronica Romero-West of La Canada Design Group. “In this age of faster, smarter, better and smaller, they`re trying to develop everything on a smaller scale. Instead of large vehicles or instruments, they`re concentrating on miniaturizing everything for economy as well as efficiency.”
Designing flexibility
Flexibility is also a must at this stage of the planning in designing the individual labs. The structural grid was designed to provide a relatively column-free space for laboratory development. Mechanical equipment is located on the roof and screened from public view on the east, south and west elevations. The north elevation is open, and ducts serving the labs on the first floor are exposed, providing maximum flexibility for future modifications. As the mission evolves and specific testing instruments are determined, chambers can be created as needed for specific instruments, says Romero-West. Also, as the facility`s missions expand, more buildings will be needed, so 25 percent to 30 percent extra capacity has been designed into all systems, including controls, air-handlers and electrical systems.
“Like any other quasi-government facility, once it`s built, they don`t get a lot of opportunity or money to change the facility, so they want it to be as flexible as possible. We tried to make it flexible without knowing the specifics at this point, so we allowed for 100 watts per square meter of heatload,” says Romero-West. The facility is being designed to accommodate upgrades of an entire room or each individual room to Class 10,000. The assembly cleanrooms, physical measurements laboratory, and chemical measurements laboratory are currently designed to Class 100,000. Later, specialized Class 100 environmental chambers — actually sub-cleanrooms — will be installed to accommodate functions as they evolve with the missions. To minimize vibration throughout the building, the laboratory will be cast-in-place reinforced concrete. To conserve space, the mechanical and electrical design makes use of the excess capacity of the central plant and cooling tower of an adjacent building, which will accommodate sister functions.
Special 4-meter high (13 ft., 1.5 in.) ceilings on both floors provide a large area of interstitial space to accommodate ductwork and maximum flexibility for HVAC and process piping. Each laboratory has its own individual air-handling unit so that the air is never mixed. This has necessitated an interstitial vs. a plenum ceiling design. Four-foot diameter steel ducts supply Class 100,000 air from rooftop air-handling units, which flows out the side of the building and back to the air handlers. The ducts are encased in an insulated metal enclosure to maintain the right temperature as air flows to the exterior of the building and back into the air handler. All ductwork is precleaned and cleaned again during installation with a mixture of DI water and isopropyl alcohol. Class 100,000 areas will have a minimum circulated air velocity of 5.5 ft./min. HEPA filters will be located in the ceiling grid (approximately one HEPA per 100 sq. ft.). To prevent jets of cold air, diffuser screens will direct air horizontally, as well as vertically. Filter velocity will be 90 ft./min. (HEPAs).
Air handling requirements
Air will flow through ceiling HEPA filters. Return air will be ducted from the floor, and exhaust air will be ducted to the outside. Temperatures will probably be kept at 68 degrees Fahrenheit ± 2 degrees; humidity at 46 percent ± 3 percent, and the building is controlled by an energy management system. Metric units were used for all dimensions. Heatload in the sub-cleanroom created by the recirculation fans, as well as the equipment, poses a challenge in cooling the space, says Jay Landgren, principal project director at AE Associates, Inc. (Greeley, CO), the outside consultant designing the mechanical systems for the cleanrooms. Fans and cooling coils will be designed in, and chilled water will be circulated through a tertiary loop at roughly 60 degrees F. For Class 100,000 areas, the water will be distributed through pumps to the seven air-handling units located on the roof. These air-handling units, says Landgren, are the same as those used in microelectronics factories, handling 7,000 to 10,000 cfm apiece — powder-coated internally, stainless steel components, aluminum components, no carbon steel, no painted surfaces that would offgas.
“Starting at the outside air intake, we pre-filter the air with a 30 percent filter, and then, the air passes through a carbon filter to remove hydrocarbons, because we`re out here in the Los Angeles area,” says Landgren. “The next step is a 65 percent filter, and that would further clean up the entering outside air, but it also removes dusting problems associated with carbon filters. Carbon tends to slough off when it`s jiggled or installed or removed, and carbon pellets can fall out into the air stream. We have a plug-fan — and then we have 95 percent filters and then a cooling coil, where we will chill the air temperature down to remove moisture and also to get it down to an air temperature that`s suitable for cooling the space. And sometimes when you`re dehumidifying, you must take the air temperature down lower than what the space requires; so the next step required is to heat it with a heating coil. And then, one more step down from there are humidifiers (electric).” Ventilation systems will also be necessary for toxic gas cabinets, such as nitrogen for operations that may require gas purging.
Lab and assembly cleanrooms
The laboratory`s in situ environment will be located in the 1,200-sq. ft. physical measurements lab, which will also contain environmental chambers and vibration tables. The various planet atmospheres, such as the low temperature and atmospheric pressure of Mars, will be created and tested in the 1,000-sq. ft. chemical measurement laboratory. “It`s a big challenge,” says Romero-West, “because you need to keep outside particles or contaminants from getting in there and spoiling the testing. This is also where any biological hazards — earth-originating chemical and biological contaminants — will be removed.”
Instruments will be assembled in the assembly cleanroom, which features its own air-handling unit operating at 12,000 cfm and is capable of being upgraded to operate at Class 10,000. The physical measurements lab and the assembly cleanroom are interconnected through an equipment support area for sharing of computers and data, while the chemical measurements lab is isolated from the two laboratories.
In the Rapid Prototyping Room laboratory, full-scale working models of prototype instruments are available for testing before being sent onto the next phase of a mission or for further testing once installed in vehicles or satellites. Here in a machine shop-type environment, says Landgren, a part can be machined on the spot as prototypes are being built.
Because equipment is brought in infrequently — once or twice a year — an equipment wipedown area, with its own ventilation to exhaust for the isopropyl alcohol, shares quarters with the large, Class 100,000 gowning area, where laboratory personnel don booties, jumpsuits and hoods. Part of the clean protocol is a Class 100,000 “clean” janitor`s closet, “clean” toilet, and also a clean conference room — or “clean document room” which allows lab personnel to use those facilities without degowning — all cleanroom support areas adjacent to one another.
Plans also include construction of a spectacular two-story glass-windowed observation corridor, with a viewing aisle running the full length of the 8-meter-long corridor. Visitors will be able to watch satellites being put together in the assembly cleanroom and physical measurements lab without disturbing personnel at work.
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(At right) Assembly of Mars Pathfinder, launched in December 1996. Pathfinder landed on the surface carrying a small rover robot. Mars missions are planned for about once every two years.
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View of NASA`s Mars Global Surveyor spacecraft, managed by JPL, with its science payload for its study of the Martian atmosphere, surface and interior.
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(At left) Technicians at the Jet Propulsion laboratory ready the power and pyro subsystem for installation of NASA`s Saturn-bound Cassini spacecraft. Cassini is schedule to arrive at the ringed planet in July 2004 to begin four years of detailed studies. It will also carry a parachuted probe to be dropped to the surface of Saturn`s large moon Titan.
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One possible sample return mission concept under consideration by NASA and scientists and engineers at NASA`s Jet Propulsion Laboratory (JPL). In this concept, a spacecraft would carry two or more miniature rovers to Mars, where the vehicles would rove independently, collecting soil and rock samples which would then be returned to the mothership. The sample return spacecraft would be able to blast off the surface of Mars, as seen here, carrying the soil samples, and rendezvous with an orbiter circling Mars. The soil samples could be transferred in space to the orbiter, which would then return the samples to Earth.
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The Huygens probe parachutes to the surface of Saturn`s moon Titan after being released by the Cassini orbiter. (Artist`s Conception)
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Cassini/Huygens above Titan.
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An aerial photo of the Jet Propulsion Laboratory (JPL) main site in Pasadena, CA.