A dedicated deployable aerobraking structure concept was developed that significantly increases the effective area of a spacecraft during aerobraking by up to a factor of 5 or more (depending on spacecraft size) without substantially increasing total spacecraft mass. Increasing the effective aerobraking area of a spacecraft (without significantly increasing spacecraft mass) results in a corresponding reduction in the time required for aerobraking. For example, if the effective area of a spacecraft is doubled, the time required for aero-braking is roughly reduced to half the previous value. The dedicated deployable aerobraking structure thus enables significantly shorter aerobraking phases, which results in reduced mission cost, risk, and allows science operations to begin earlier in the mission.
In order to achieve a large area without impacting the spacecraft or launch vehicle, a deployable structure is necessary. The dedicated deployable aerobraking structure uses a set of deployable rigid “arms” to deploy and support a large membrane. The membrane is made of material (Kapton, for example) that can withstand the thermal and mechanical loads characteristic of aerobraking. Once aerobreaking is complete, this aerobraking structure would be jettisoned into an atmosphere-intercepting orbit and subsequently destroyed upon atmospheric entry. This concept uses a mechanical implementation distinct from inflatable aerodynamic decelerators studied for aerocapture and other applications. Aerobraking requires multiple passes through the atmosphere over several weeks (at least), and so any small leaks or punctures that develop in an inflatable structure during that time could compromise the inflatable structure; this makes inflatable structures a higher risk implementation for an aerobraking structure relative to the mechanical implementation used in this concept.
Tentative mechanical and thermal requirements for this technology have been developed. Full-scale proof of concept hardware corresponding to one quadrant of a 72 m2 aerobraking structure was successfully designed, fabricated, deployed, and tested. The lab tests were designed so that the mechanical loads in the 1-g lab environment were higher than the anticipated aerobraking loads, which proved the structure could survive in flight. Finite element models were developed and found to be in good agreement with the proof-of-concept hardware. Thermal and attitude stability aspects of the concept were analyzed. Based on the preliminary requirements, hardware tests, computational models, and analyses developed, the concept was found to be viable using conventional engineering materials and techniques.
In addition to potential use on planetary missions, this technology can also be used as an inexpensive, robust, and reliable method for reducing orbital debris hazards in Earth orbit by increasing the rate of orbital decay of objects in orbit about the Earth such as decommissioned satellites and spent launch vehicle upper stages.
This work was done by Louis R. Giersch and Kevin Knarr of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Mechanics/Machinery category. NPO-47227
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