Friday, May 4, 2012
At the Science and Engineering Festival, there was a booth showing off a program called R.E.B.R.
"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 74 and 120 km (40 and 65 nautical miles (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 composed of a GPS receiver, temperature sensors, accelerometers and rate gyros, a pressure sensor, electronics developed for Aerospace Corporations PICOSAT and modified for REBR, a commercially-available Iridium modem, a combination GPS/Iridium antenna, and batteries (one year lifetime in the dormant mode; no power required from host vehicle). All equipment is contained within an aeroshell design developed by NASA Ames Research for the Deep-Space-2 Mars probes. The thermal protection system is provided by The Boeing Company. Total weight of the flight system, which includes all sensors, electronics, and batteries, will be approximately 4 kg (9 pounds) and the maximum dimension is approximately 31 cm (1 foot). The device, enclosed in its protective housing, is attached to an available location on the host vehicle. Including the housing, the device weighs approximately 8.6 kg (19 pounds) and has a maximum dimension of 36 cm (14 in). The device is carried to orbit attached to the host vehicle (or can be carried to orbit in a storage bag and attached by crewmembers), begins to record data during reentry, and remains attached to the host until the housing melts away during reentry breakup. Before and after release, the device is protected by its heat shield. At about 30 km (100,000 ft), the device is falling at subsonic velocity. At about 18.3 km (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 device is not designed to survive ground impact. The recovery of the REBR hardware is not required."