Reentry Breakup Recorder with Wireless Sensors (REBR-W) - 11.22.16

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
When aging satellites or space stations succumb to atmospheric drag and gravity and fall back down to Earth, passage through the denser atmosphere breaks them up into several pieces that can be hazardous to life on the ground. The Reentry Breakup Recorder with Wireless Sensors (REBR-W) tests a device that can ride along inside a vehicle re-entering Earth’s atmosphere to record data about when and how the craft breaks apart in the atmosphere. This information can be used for reentry hazard prediction studies, reducing risks, and improving planning for spacecraft that eventually must deorbit.
Science Results for Everyone
Initiation of this investigation has been affected by power-chain failure on the ATV-5 vehicle in February 2015.

The following content was provided by William Ailor, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom:

Principal Investigator(s)
Michael A. Weaver, Ph.D., The Aerospace Corporation, El Segundo, CA, United States

Co-Investigator(s)/Collaborator(s)
William Ailor, Ph.D., The Aerospace Corporation, El Segundo, CA, United States

Developer(s)
The Aerospace Corporation, El Segundo, CA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Technology Demonstration Office (TDO)

Research Benefits
Space Exploration, Earth Benefits, Scientific Discovery

ISS Expedition Duration
March 2015 - March 2016; March 2016 - September 2016

Expeditions Assigned
43/44,45/46,47/48

Previous Missions
Increments 27/28 and 31/32

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Experiment Description

Research Overview

  • Hazards posed by space hardware debris surviving reentry are becoming a significant issue for spacecraft designers and space mission planners. Current DoD and NASA policies specify that space hardware must be reentered into an ocean area when the casualty expectation, the risk of a human injury or death, for a random reentry exceeds 1 in 10,000.  As a result, spacecraft must potentially be deorbited into a safe area (open ocean) before end-of-life, as occurred for NASA’s Compton Gamma Ray Observatory, when failure of one of the control gyros forced deorbit of an otherwise healthy spacecraft.  This requirement can add significant cost to the spacecraft and the mission, or the appropriate risk acceptance authority is required to accept a risk with a large degree of uncertainty.
  • Data collected enhance our understanding of vehicle breakup during reentry, allowing improvements in prediction of the breakup process, increasing the accuracy of estimated casualty expectations, and thus limiting premature deorbiting of space hardware.  Data may also enable space hardware to be “designed for demise” – designed to disintegrate into less hazardous fragments – thereby increasing mission life and reducing costs by eliminating the requirement for a controlled deorbit.  The goal of the launch (and reentry) test is to verify operation under actual reentry breakup conditions.
  • In the long term, this research assists in the development of a "black box" for commercial space transportation systems.  The research may also lead to a cost-effective device and mission strategy that may be used by university and other researchers to perform hypersonic flight testing, evaluate thermal protection materials in a reentry environment, study the rarefied flow regime, etc.

Description

Casualty expectation for reentering space hardware is computed using reentry-survivability models that, in general, have not been validated against flight data from orbital reentries.  In fact, observational data indicate that these models do not accurately predict the heating experienced in the rarefied regime (between the free-molecular and continuum regimes, or typically between 40 and 65 nautical miles in altitude), and ad hoc corrections are used to account for this inaccuracy.  Exclusive of the Space Shuttle Columbia accident, only a few fragments have been found on the ground and analyzed.  Data obtained   from a validated model would provide a more accurate basis on which to specify necessary re-design of space hardware to include features that will realistically minimize reentry ground hazard.  Even better, sufficient data should lead to physical explanations of the apparent inaccuracy, allowing improved physical modeling.

The REBR-W system is designed to collect the type of data needed to improve reentry breakup models.  REBR-W uses a small, lightweight, autonomous system for recording temperatures, accelerations, and other data experienced by the host vehicle as it reenters the atmosphere.  REBR-W survives the breakup of the host vehicle and “phones home” the recorded data prior to ground or ocean impact of the recording device.  REBR-W can be attached to launch stages and spacecraft and the data collected from their reentries will expand our understanding of reentry breakup and related phenomena.    A single launch may include more than one REBR-W.

The REBR-W design consists of a sensor suite consisting of temperature sensors, accelerometers, rate gyros, pressure sensors, an Iridium modem, a combination GPS/Iridium antenna, and batteries (no power required from host vehicle).  All internal equipment is contained within a heat shield and includes a thermal protection system derived from Space Shuttle technology.

The REBR-W device, enclosed in its protective housing, is attached to an available location on the host vehicle and its external sensors are clamped or affixed to structural elements where temperature increase during reentry can be monitored.  The device begins to record data during reentry, and remains attached to the host until the housing fasteners melt away during reentry breakup and release the instrument.  Before and after release, the device is protected by its heat shield.  At about 160,000 ft, the modem begins attempting to connect to the Iridium system.  At about 96,000 ft, the self-stabilizing device is falling at subsonic terminal velocity and begins transmitting its data to a ground-based computer.  The location and time of reentry can be arbitrary and the recovery of the REBR hardware is not required.
Casualty expectation for reentering space hardware is computed using reentry-survivability models that, in general, have not been validated against flight data from orbital reentries.  In fact, observational data indicate that these models do not accurately predict the heating experienced in the rarified regime (between the free-molecular and continuum regimes, or typically between 40 and 65 nmi in altitude), and ad hoc corrections are used to account for this inaccuracy.  Exclusive of the Space Shuttle Columbia accident, only a few fragments have been found on the ground and analyzed.  Data obtained from a calibrated model would provide a more accurate basis on which to specify necessary re-design of space hardware to include features that will realistically minimize reentry ground hazard.  Even better, sufficient data should lead to physical explanations of the apparent inaccuracy, allowing improved physical modeling.

The objective of the REBR flight test is to verify the use of a small, lightweight, autonomous system for recording temperatures, accelerations, and other data experienced by the host vehicle during reentry, surviving the breakup of the host vehicle, and finally “phoning home” the recorded data prior to impact of the recording device.  Once verified, REBR can be attached to launch stages and spacecraft and the data collected from their reentries will expand our understanding of reentry breakup and related phenomena.  A single launch may include more than one REBR. 
The REBR design consists of a sensor suite consisting of temperature sensors, accelerometers, rate gyros, a pressure sensor, Iridium modem, and a combination GPS/Iridium antenna, and batteries (1-year lifetime in the dormant mode; no power required from host vehicle).  All equipment is contained within an aeroshell and includes a thermal protection system derived from Space Shuttle technology.  Total weight of the flight system, which includes all sensors, electronics, batteries, and housing will be approximately 20 pounds and the maximum dimension is approximately 15 inches.  The device, enclosed in its protective housing, is attached to an available location on the host vehicle.  The device begins to record data during reentry, and remains attached to the host until the housing fasteners melt away during reentry breakup and release the instrument.  Before and after release, the device is protected by its heat shield.  At about 100,000 ft, the device is falling at subsonic velocity.  At about 60,000 ft the GPS/Iridium antenna is pointing to zenith; at this point, a phone call is made through the Iridium system and the device transmits its data to a ground-based computer.  The location and time of reentry can be arbitrary and the recovery of the REBR hardware is not required.
 

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Applications

Space Applications
If a spacecraft's mission ends because of an accident, a broken part, low propellant, or failing components, NASA and the Department of Defense require that it re-enter over unpopulated areas (such as the open ocean) to prevent injury to people or damage to property. This sometimes means de-orbiting a spacecraft that still works, to ensure it is out of the way. Currently, scientists predict vehicle breakup using computer models, but observations suggest the models are not always accurate. The REBR-Wireless device rides on a vehicle that will break up on reentry, and the data REBR-Wireless collects is providing new insight that could eliminate the need for moving a spacecraft before it falls to Earth naturally. This would extend mission life and reduce cost and complexity while minimizing risk.

Earth Applications
Results from this investigation could help in designing future spacecraft that have lower risk to people and property when they reenter even if the vehicle cannot be controlled or directed so that debris falls in an unpopulated area. In addition to insight into the nature of spacecraft breakups during reentry, data from REBR-W may also lead to new ways for scientists to perform hypersonic flight testing, test new thermal protection materials, and study the uppermost layers of the atmosphere.

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Operations

Operational Requirements and Protocols

Details on the launch environment (loads, vibrations, etc.) must be closely monitored.  The nominal mission profile, including launch accelerations, staging events, and orbit parameters for the host vehicle are required to assure the proper functioning of the REBR-W electronics.  Coordinates of the physical location, and orientation of the REBR-W devices in the host vehicle’s reference frame are recorded.  Attachment constraints (footprint limitations, penetration or bonding restrictions, etc.), and the environment at the attachment location (exposure to space environment, internal temperatures, cryogenic temperatures, etc.) are documented.


REBR-W collects data at the beginning of and during reentry.  The goal is to ride a host launch stage or spacecraft that stays in orbit for a relatively short time (less than 6 months).  REBR-W remains attached to the host vehicle until separated during the reentry breakup phase.  Data are broadcast via the Iridium communications system to a ground-based computer prior to ground impact.  Data covers at most 30 minutes of flight and the data file created is small.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Related Websites
The Aerospace Corporation

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Imagery

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Overview of REBR-W and sensors for ATV-5 reentry. Image courtesy of The Aerospace Corporation.

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Exploded view of the REBR-W assembly.  Image courtesy of The Aerospace Corporation.

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Pre-launch photo of REBR-W and sensors for ATV-5 reentry. Image courtesy of The Aerospace Corporation.

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Planned locations on ATV-5 for installation of REBR-W and sensors. Image courtesy of The Aerospace Corporation.

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