Space Power Facility#Reverberant Acoustic Test Facility

This is a vacuum chamber built by NASA in 1969. It stands {{convert|122|ft|m}} high and {{convert|100|ft|m}} in diameter, enclosing a bullet-shaped space. It is the world's largest thermal vacuum chamber. It was originally commissioned for nuclear-electric power studies under vacuum conditions, but was later decommissioned. It was subsequently recommissioned for use in testing spacecraft propulsion systems. Recent uses include testing the airbag landing systems for the Mars Pathfinder and the Mars Exploration Rovers Spirit and Opportunity, under simulated Mars atmospheric conditions.

The facility was designed and constructed to test both nuclear and non-nuclear space hardware in a simulated low-Earth-orbiting environment. Although the facility was designed for testing nuclear hardware, only non-nuclear tests have been performed throughout its history. Test programs performed at the facility include high-energy experiments, rocket-fairing separation tests, Mars Lander system tests, deployable solar sail tests, and International Space Station hardware tests. The facility can sustain a high vacuum (10⁻⁶ torr, 130 μPa), and simulate solar radiation via a 4 MW quartz heat lamp array, solar spectrum by a 400 kW arc lamp, and cold environments ({{convert|-320|F|C}}) with a variable geometry cryogenic cold shroud.

The facility is available on a full-cost reimbursable basis to government, universities, and the private sector.

The aluminum test chamber is a vacuum-tight aluminum plate vessel that is {{convert|100|ft|m}} in diameter and {{convert|122|ft|m}} high. Designed for an external pressure of {{convert|2.5|psi|kPa|abbr=on}} and internal pressure of {{convert|5|psi|kPa|abbr=on}}, the chamber is constructed of Type 5083 aluminum which is a clad on the interior surface with a {{convert|1/8|in|mm|abbr=on}} thick type 3003 aluminum for corrosion resistance. This material was selected because of its low neutron absorption cross-section. The floor plate and vertical shell are {{convert|1|in|mm}} (total) thick, while the dome shell is {{convert|1+3/8|in|mm|abbr=on}}. Welded circumferentially to the exterior surface is aluminum structural T-section members that are {{convert|3|ft|m|1}} deep and {{convert|2|ft|m|1}} wide. The doors of the test chamber are {{convert|50|by|50|ft|m}} in size and have double door seals to prevent leakage. The chamber floor was designed for a load of 300 tons.

The concrete chamber enclosure serves not only as a radiological shield but also as a primary vacuum barrier from atmospheric pressure. {{convert|130|ft|m}} in diameter and {{convert|150|ft|m}} in height, the chamber was designed to withstand atmospheric pressure outside of the chamber at the same time vacuum conditions are occurring within. The concrete thickness varies from {{convert|6|to|8|ft|m}} and contains a leak-tight steel containment barrier embedded within. The chamber's doors are {{convert|50|by|50|ft|m}} and have inflatable seals. The space between the concrete enclosure and the aluminum test chamber is pumped down to a pressure of {{convert|20|torr|kPa}} during a test.

Space Power Facility.gif|Interior of the Space Power Facility

Image:Centaur_Standard_Shroud_at_SPF_Plum_Brook_-_GPN-2000-001464.jpg|Centaur Standard Shroud at the Space Power Facility

Thermo-Vac Scavenger Plate.JPG|NASA's SPF thermal-vac chamber scavenger plate

Thermo VacCryo Pump as Seen from the Annulus Basement.JPG|NASA's SPF thermal-vac chamber VacCryo pump as seen from the annulus basement

Turbo Molecular Pumps in the Thermo-Vac Chamber Wall.JPG|NASA's SPF thermal-vac chamber turbo molecular pumps

Brian Cox of the BBC's Human Universe filmed a rock and feather drop episode at the Space Power Facility.[https://www.youtube.com/watch?v=E43-CfukEgs Rock and Feather Drop at NASA's Space Power Facility]

Designed specifically as a large-scale thermal-vacuum test chamber for qualification testing of vehicles and equipment in outer-space conditions, it was discovered in the late 2000s that the unique construction of the SPF interior aluminum vacuum chamber also makes it an extremely large and electrically complex microwave or radio frequency cavity with excellent reverberant electro-magnetic characteristics. In 2009 these characteristics were measured by the National Institute of Standards and Technology and others[https://archive.org/details/electromagnetice1558koep NIST TN-1558 - An electromagnetic evaluation of the NASA space power facility at Plum Brook Station by Koepke, Galen H.; Ladbury, John; Camell, Dennis; Coder, Jason; Hammerschmidt, Chriss; Direeen, Randall; Guerrieri, Jeff.] after which the facility was understood to be, not only the world's largest Vacuum chamber, but also the world's largest EMI/EMC test facility. In 2011, the Glenn Research Center successfully performed a calibration of the aluminum vacuum chamber[https://ntrs.nasa.gov/search.jsp?R=20150000254 NASA TM—2014-218363 - Space Power Facility Reverberation Chamber Calibration Report] using IEC 61000-4-21 methodologies.[https://webstore.iec.ch/publication/4191 IEC 61000-4-21:2011 - Electromagnetic compatibility (EMC) - Part 4-21: Testing and measurement techniques - Reverberation chamber test methods] As a result of these activities, the SPF can perform radiated susceptibility EMI tests for vehicles and equipment per MIL-STD-461, and can achieve MIL-STD-461F limits above approximately 80 MHz. In the spring of 2017 the low-power characterizations and calibrations from 2009 and 2011 were proven correct in a series of high-power tests performed in the chamber to validate its capabilities. The SPF chamber is currently being prepared for EMI radiated susceptibility testing of the crew module for the Artemis 1 of NASA's Orion spacecraft.

Thermo-Vacuum Chamber with EMI mode stirrer.jpg|EMI mode stirrer in the thermal-vacuum chamber

Todd Shroeder working on the EMI Test Equipmnet.jpg|Installation of EMI equipment in the thermal-vacuum chamber

The Reverberant Acoustic Test Facility has 36 nitrogen-driven horns to simulate the high noise levels that are experienced during a space vehicle launch and supersonic ascent conditions. The RATF is capable of an overall sound pressure level of 163 dB within a {{convert|101,500|ft3|adj=on}} chamber.

SpaceX Falcon 9 Fairing RATF Test at NASA's Space Power Facility.JPG|The SpaceX Falcon 9 fairing was the first test article to utilize NASA's (RATF).

SPF RATF.tif|Reverberant Acoustic Test Facility

Larry Opper in front of one of the 25 Hz. Horns in the RATF.jpg|Larry Opper in front of one of the 25 Hz horns in the RATF

NASA's Vibro-Acoustic Control Room at the Space Power Facility.jpg|NASA's Vibro-Acoustic Control Room at the Space Power Facility

File:Mechanical Vibration Facility.jpg

The Mechanical Vibration Test Facility (MVF) is a three-axis vibration system. It will apply vibration in each of the three orthogonal axes (not simultaneously) with one direction in parallel to the Earth-launch thrust axis (X) at 5–150 Hz, 0-1.25 g-pk vertical, and 5–150 Hz 0-1.0 g-pk for the horizontal axes.

Vertical, or the thrust axis, shaking is accomplished by using 16 vertical actuators manufactured by TEAM Corporation,[https://teamcorporation.com/ TEAM Corporation] each capable of {{convert|30000|lbf|kN|abbr=on}}. The 16 vertical actuators allow for testing of up to a {{convert|75000|lb|kg|abbr=on}} article at the previously stated frequency and amplitude limits.

Horizontal shaking is accomplished by four TEAM Corporation Horizontal Actuators. The horizontal actuators are used during vertical testing to counteract cross axis forces and overturning moments.

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File:Mechanical Vibration Facility with the table installed.jpg|Mechanical Vibration Facility with the table installed

File:Control Accelerometer Installation.JPG|Control accelerometer installation

File:One of 16 Vertical Actuators and Spherical Coupling Assemblies for Space Power Facility's MVF.jpg|One of 16 vertical actuators and spherical coupling assemblies for the MVF

File:VAA3.jpg|Vertical actuator

File:TEAM Horizontal Actuator for the Mechanical Vibration Facility.jpg|TEAM horizontal actuator for the Mechanical Vibration Facility

In addition to the sine vibe table, a fixed-base modal floor sufficient for the {{convert|20|ft|m|abbr=on}} diameter test article is available. The fixed-base modal test facility is a {{convert|6|in|mm|abbr=on}} thick steel floor on top of {{convert|19|ft|m|abbr=on}} of concrete, that is tied to the earth using {{convert|50|ft|m|abbr=on}} deep tensioned rock anchors.

There were over {{convert|21000000|lb|MT}} of rock anchors, and {{convert|6000000|lb|MT}} of concrete used in the construction of the fixed-base modal test facility and mechanical vibration test facility.

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File:MVF and modal plate located the NASA Space Power Facility.jpg|The modal test facility is a {{convert|6|in|mm|abbr=on}} steel plate on top of {{convert|19|ft|m|abbr=on}} of concrete, that is then tied to the shale utilizing tensioned rock anchors that are {{convert|50|ft|m|abbr=on}} long.

File:Mechanical Vibration Facility's Table - Modal Test (Free-Free).JPG|Mechanical Vibration Facility's table - modal test (free-free)

File:Vibration Test Article - Modal Test.JPG|Vibration test article - modal test

The SPF layout is ideal for performing multiple test programs. The facility has two large high bay areas adjacent to either side of the vacuum chamber. The advantage of having both areas available is that it allows for two complex tests to be prepared simultaneously. One can be prepared in a high bay while another is being conducted in the vacuum chamber. Large chamber doors provide access to the test chamber from either high bay.

{{Reflist}}

{{commons category|Space Environments Complex}}

• [https://www.nasa.gov/neil-armstrong-test-facility Neil Armstrong Test Facility] - official NASA website
• [https://web.archive.org/web/20090714024142/http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001462.html Skylab Shroud in Plum Brook Space Power Facility]
• [http://www.nasa.gov/multimedia/imagegallery/image_feature_648.html NASA image gallery, featuring the SPF]
• [https://web.archive.org/web/20071217095247/http://facilities.grc.nasa.gov/spf/capabilities.html Detailed facility capabilities]
• [https://www.youtube.com/watch?v=uva06uQI0rI "Space Power Facility Construction"] at Youtube

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