by Staff Writers
Houston TX (SPX) Nov 22, 2016
Just five months into its two-year demonstration mission on the International Space Station, the first human-rated expandable habitat in low-Earth orbit is already returning valuable information about expandable technology performance and operations in space. Developed through a public-private partnership between NASA and Bigelow Aerospace, the Bigelow Expandable Activity Module (BEAM) launched to the station April 8, 2016, in the "trunk" of the Dragon capsule during the eighth SpaceX Commercial Resupply Service mission.
In late May, with careful instructions from the ground, NASA astronaut Jeff Williams conducted the manual expansion of the module through a series of seconds-long valve openings that allowed space station air to enter and expand BEAM. After BEAM was fully expanded with low pressure, air tanks inside the BEAM were opened with an automated controller to fully pressurize BEAM to match station pressure.
From its packed to expanded configurations, the module nearly doubled in length and increased by 40 percent in diameter. This capability to increase a spacecraft's useable internal volume after launch offers a potentially significant advantage for mission planners who seek to reduce cargo volume, maximize payload space and efficiently package structures inside a launch vehicle fairing.
During and after expansion, sensors inside the BEAM recorded overall structural and thermal performance. Once it was confirmed that the module was maintaining pressure with no leaks during the week following deployment, Williams commenced the beginning of BEAM's two-year demonstration when he entered the module for the first time on June 6, 2016. He entered again on June 7 and 8, outfitting the interior with additional sensors and air ventilation ducts and taking surface and air samples to test for microbes.
Steve Munday, BEAM Manager at NASA's Johnson Space Center (JSC) in Houston, notes that the module and its sensors have performed as expected for the most part. "Through the NASA sensor suites on board, our teams on the ground, and astronaut support on station, we're gaining extremely valuable data about the performance of expandable structures and habitats in space," he says.
The NASA sensor suites inside BEAM help analyze module performance as it orbits Earth attached to a port on the space station's Tranquility Node. Bulkhead accelerometers measured structural dynamics during deployment, wireless thermal sensors help assess the insulation performance of the fabric shell layers and metallic bulkheads, active and passive dosimeters measure radiation penetration, and Distributed Impact Detection System (DIDS) sensors detect and locate any space debris impacts on the BEAM exterior.
But like any advanced technology demonstration, the BEAM has offered a few surprises. "That's why we test, to learn and explore new technology," asserts Munday.
In fact, the successful expansion on May 28 was the second attempt. During the first attempt on May 26, the BEAM's fabric layers expanded more slowly than was predicted by deployment models on the ground, perhaps partially due to being tightly packed for more than a year awaiting launch on SpaceX CRS-8. NASA and Bigelow Aerospace teams halted the deployment to closely compare the predictive deployment models pressure limits with actual readings to ensure that continuing expansion would pose no risk to the station or crew.
On May 27, astronauts released pressure from BEAM to help the stiff fabric layers relax after the initial resistance. After reconfirming that the BEAM deployment operation posed no risk to the space station or its crew, the team restarted BEAM expansion on May 28, successfully reaching the fully expanded and pressurized configuration after about seven hours.
Thermal engineers at JSC found that BEAM was warmer than predicted, particularly in the packed configuration immediately prior to deployment. Munday suggests it could be due to less contact between the folded layers, providing more heat insulation than we expected. Warmer is better than cooler for BEAM, which has no active thermal control and relies upon air exchange with the station.
"A colder-than-expected BEAM would have increased the risk of condensation, so we were pleased when Jeff first opened the hatch and found the interior to be bone dry," says Munday. "BEAM is the first of its kind, so we're learning as we go and this data will improve our structural and thermal models and analyses going forward."
Space station crew members entered the BEAM twice more in September to reinforce instruments that had loosened since installation, reboot a sensor data-relay laptop that had crashed, take additional samples for return to Earth, and perform tests inside the module to help engineers on the ground better define the structural characteristics of BEAM. NASA Astronaut Kate Rubins entered the BEAM on Sept. 5 to replace the DIDS battery packs after it was determined that drained batteries were disrupting wireless communications with the sensors.
Ground operators remotely reconfigured DIDS power settings to a more efficient mode, preventing further disruptions. On Sept. 29, she entered again to conduct a series of modal tests to assess how the structure responds to impacts that cause vibrations and the structure's ability to dampen the vibrations.
NASA and Bigelow Aerospace are pleased to report that, overall, BEAM is operating as expected and continues to produce valuable data. Structural engineers at NASA JSC confirmed that BEAM deployment loads upon the space station were very small, and continue to analyze the module's structural data for comparison with ground tests and models.
Researchers at NASA's Langley Research Center in Hampton, Virginia, have found no evidence of large debris impacts in the DIDS data to date-good news for any spacecraft. And radiation researchers at JSC have found that the dosage due to Galactic Cosmic Rays in BEAM is similar to other space station modules, and continue to analyze local "trapped" radiation particles, particularly from the South Atlantic Anomaly, to help determine additional shielding requirements for long-duration exploration missions.
The space station is the world's primary platform for testing and validating deep space capabilities. "The two-year BEAM mission on ISS provides us with an early opportunity to understand how expandable habitats perform in space," says Munday. "We're extraordinarily fortunate to have the the space station and its crew to help demonstrate and assess BEAM technology for use in future exploration missions."
The BEAM demonstration is a public-private partnership managed by NASA's Advanced Exploration Systems Division (AES). AES is pioneering innovative approaches and public-private partnerships to rapidly develop prototype systems, advance key capabilities, and validate operational concepts for future human missions beyond Earth orbit.
Although the BEAM represents an early demonstration of deep space habitation capabilities, AES is also pursuing deep space habitation development with industry partners through contracts issued under the Next Space Technologies for Exploration Partnerships (NextSTEP) Broad Agency Announcement.
Under NextSTEP, four companies (Bigelow Aerospace, Boeing, Lockheed Martin and Orbital ATK) have recently completed cislunar habitation concept studies, and all four plus Sierra Nevada Corporation, are proceeding toward contract negotiations to develop full-size ground prototypes of cislunar habitats. A sixth team led by NanoRacks was selected to complete an additional study on the repurposing of upper stages of rockets into habitats.
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