REBR Probes the Mystery of Reentry Forces
Thousands of man-made objects currently circle the Earth, ranging in size from small flecks of paint to bus-sized satellites. At some point, all will reenter Earth’s atmosphere as their orbits decay.
The majority of them will be destroyed due to aerodynamic heating. However, some are large enough or constructed of materials strong enough to survive reentry and impact Earth’s surface.
No one has ever been injured by a reentering piece of space debris, due primarily to the fact that 70 percent of Earth’s surface is water – the majority of debris that survives reentry lands in the ocean and sinks. Those objects that have come to rest on land have done so largely in unpopulated areas.
However, there is the possibility of injury or property damage from reentering debris. In order to minimize this risk, engineers and scientists at The Aerospace Corporation have been working to better understand all the dynamic forces that are in play during reentry. Their efforts have been complicated by the fact that all data about reentry forces must be gathered remotely, from ground-based observations.
To collect more accurate reentry data, Aerospace engineers conceived, designed, and constructed the Reentry Breakup Recorder, or REBR. The basketball-sized device is launched into orbit aboard a larger spacecraft, and later intentionally deorbited, when a host spacecraft returns to Earth. The REBR gathers data as its host vehicle reenters, transmitting data to Earth for analysis.
The first REBR in space was placed aboard a Japanese H-II Transfer Vehicle (HTV), which carried supplies to the ISS, on Jan. 22, 2011. Once the supplies were unloaded, the HTV was loaded with trash and waste material from the station, then cast loose and commanded to reenter over the South Pacific, on March 30, 2011.
The HTV disintegrated as it reentered the atmosphere. REBR, still aboard the vehicle, recorded the first-ever reentry breakup data obtained from unprotected space hardware. REBR recorded data about acceleration, rotation rate, heat shield temperature, and internal pressure. It successfully gathered this information from the first moments of reentry all the way through the final breakup of the HTV, at which point REBR separated from the remnants of the HTV and fell freely.
While in free flight, REBR transmitted its recorded data via a telephone link through the Iridium satellite constellation to Aerospace. REBR continued to transmit its data after surviving an ocean impact – which it was not designed to do – and floating for 17 hours until its battery died.
A second REBR, also carried into space on the HTV-2, was transferred to the European ATV-2 for reentry later in 2011. That REBR failed to transmit data from that reentry.
The REBR-3 and REBR-4 were launched by the Japan Aerospace Exploration Agency (JAXA) in July, 2012. REBR-3 returned successfully in September and REBR-4 reentered in October.
Meanwhile, work has begun on the next version of the device — REBR-Wireless. The REBR-Wireless system will add a number of small, wireless sensors attached to critical structural elements in the host vehicle. REBR will record temperature, pressure, and other data from these small sensors as the host vehicle reenters and breaks apart. This data, added to the data stream from the REBR’s internal sensors, should provide more information on reentry heating of large, unprotected structures that can be used to verify reentry hazard prediction models and enable launch vehicles and satellites to be designed so that they pose less of a hazard to people and property during reentry.
Future REBRs may include video and photo capabilities.
REBR was developed by The Aerospace Corporation with funding and support from the Air Force Space and Missile Systems Center, the Air Force Safety Center, The Boeing Company, NASA Goddard Space Flight Center, and NASA Ames Research Center. REBR flight tests were integrated and flown under the direction of the Department of Defense’s Space Test Program.
Click here to view an interview with Ailor on NASA TV.
Click here to view an article about REBR on the NASA website.