Michael Lou

Self-Rigidizable Space Inflatable Boom

Development of inflatable structures for space applications has progressed rapidly in the past few years. Noticeable advances have been achieved in several key technology areas, such as system concepts, analysis tools, material selection and characterization, and inflation deployment control. However, many challenges remain to be overcome before the inflatable structures can be actually incorporated into space flight systems. One of these challenges is the development of suitable in-space rigidization methods, and many researchers in the space inflatables community are currently working toward this goal. The concept and development of a new type of space inflatable/self-rigidizable structures, called the spring-tape-reinforced aluminum laminate booms is described. Analysis and test results related to buckling capability, effects of stowage, modal characteristics, and dynamic responses of spring-tape-reinforced aluminum laminate booms are presented and discussed.

Inflatable Structure for a Three-Meter Reflectarray Antenna

The application of inflatable/rigidizable structures technology has become feasible for near-term large space antennas. The development of one of such application of a 3-m Ka-band reflectarray antenna is discussed. This antenna employs the beam scanning and circular polarization technology that allows the use of a flat surface instead of a parabolic antenna surface. Structurally, a flat surface is comparatively easier to fabricate, package, and maintain than a curved parabolic surface. The development of this antenna was also supported by an innovative inflatable/self-rigidizable boom technology, namely spring tape reinforced aluminum laminate boom. A spring tape reinforced aluminum laminate boom automatically rigidizes after it is deployed by inflation pressure. The rigidization of this boom requires no space power, curing agent, or other added-on rigidization devices. Small damage caused by micrometeoroid impacts will not affect structural performance of the boom, and inflation air is no longer needed after the boom is deployed. Detailed mechanical design, dynamic analysis, and deployment demonstration of the antenna are discussed.

A combined analytical and experimental study on space inflatable booms

Development and infusion of break-through technologies is needed to enable better, faster and cheaper space missions to be flown in the future. One of these technologies, space inflatable structure, is currently receiving much attention. The use of space inflatable structures can potentially revolutionize the architecture and design of many large, lightweight space systems that must have extremely high packing efficiency at launch and be reliably deployed in space. Examples of these systems include sunshields, solar arrays, solar sails, telescopes, concentrators, and space radar antennae. To facilitate effective designs of these space inflatable systems, the behaviors of their fundamental, building-block structural elements, the inflatable booms, need to be thoroughly characterized and understood. This paper presents experimental and analytical study results on different types of space inflatable booms, including the self-rigidizable carpenter-tape-reinforced aluminum laminate booms.

System concept for the next-generation spaceborne precipitation radars

The 13.8-GHz Precipitation Radar (PR) aboard the US/Japan Tropical Rainfall Measuring Mission (TRMM) satellite is the first rain profiling radar ever launched into space. A TRMM follow-on mission, called the Global Precipitation Mission (GPM), is currently planned to extend and to improve the TRMM acquired rainfall data set. One of the key components of the GPM science instrumentation is an advanced, dual-frequency rain mapping radar. In this paper, we present a system concept for this second-generation spaceborne precipitation radar (PR-2) for the GPM. The key PR-2 system consists of: (1) a 13.6/35 GHz dual frequency radar electronics that has Doppler and dual-polarization capabilities; (2) a large but lightweight, dual-frequency, wide-swath scanning, deployable antenna; (3) digital chirp generation and the corresponding on-board pulse compression scheme to allow a significant improvement on rain signal detection without using the traditional, high-peak-power transmitters and without sacrificing the range resolution; (4) an approach to adaptively scan the antenna so that more time can be spent to observe rain rather than clear air; and (5) the built-in flexibility on the radar parameters and timing control such that the same radar can be used by different future rain missions.

Development of a 7-meter inflatable reflectarray antenna

This paper presents the structural and mechanical development of a 7-meter inflatable/self-rigidizable reflectarray antenna that is intended for space communication applications.

DEVELOPMENT OF SPACE INFLATABLE/RIGIDIZABLE STR ALUMINUM LAMINATE BOOMS

Development of inflatable structures for space applications has progressed rapidly in the past few years. Noticeable advances have been achieved in several key technology areas, such as system concepts, analysis tools, material selection and characterization, and inflation deployment control. However, many challenges remain to be overcome before the inflatable structures can be actually incorporated into space flight systems. One of these challenges is the development of suitable in-space rigidi/ation methods and many researchers in the space inflatables community are currently working toward this goal. This paper describes the concept and development of a new type of space inflatable/rigidizable structures, called the springtape-reinforced aluminum laminate booms (simply, STR booms). Analysis and test results related to buckling capability, effects of stowage, modal characteristics, and dynamic responses of SRT booms are presented and discussed. Additional research efforts are also recommended for improving structural integrity of the STR booms, as well as developing load-carrying booms over 50 meters. Copyright

THERMAL DISTORTION ANALYSES OF A THREE-METER INFLATABLE REFLECTARRAY ANTENNA

Gossamer space structures are relatively large, flimsy, and lightweight. As a result, they are more easily affected or degraded by space thermal environments compared to other space structures. This study examines the structural integrity of a Three-Meter Ka-Band Inflatable/Self-Rigidizable Reflectarray Antenna under space thermal environments. Space thermal environments discussed by this paper include Earth, Mars, and Jupiter orbits. The most critical structural components of this antenna are the two Spring Tape Reinforced Aluminum Laminate Inflatable/Self-Rigidizable Booms. The effects of the thermal distortion of the booms to surface deviation of the Radio Frequency membrane are also investigated.

The Development of Large Flat Inflatable Antennna for Deep-Space Communications

NASA/JPL’s deep-space exploration program has been placing emphasis on reducing the mass and stowage volume of its spacecraft’s high-gain and large-aperture antennas. To achieve these goals, the concept of deployable flat reflectarray antenna using an inflatable/thin-membrane structure was introduced at JPL several years ago. A reflectarray is a flat array antenna space-fed by a low-gain feed located at its focal point in a fashion similar to that of a parabolic reflector. The reflectarray’s elements, using microstrip technology, can be printed onto a flat thinmembrane surface and are each uniquely designed to compensate for the different phase delays due to different path lengths from the feed. Although the reflectarray suffers from limited bandwidth (typically < 10%), it offers a more reliably deployed and maintained flat “natural” surface. A recent hardware development at JPL has demonstrated that a 0.2mm rms surface tolerance (1/50 th of a wavelength) was achieved on a 3-meter Ka-band inflatable reflectarray. Another recent development, to combat the reflectarray’s narrow band characteristic, demonstrated that dual-band performance, such as X- and Ka-bands, with an aperture efficiency of above 50 percent is achievable by the reflectarray antenna. To mechanically deploy the antenna, the reflectarray’s thin membrane aperture surface is supported, tensioned and deployed by an inflatable structure. There are several critical elements and challenging issues associated with the inflatable boom structure. First, the inflatable boom must be made rigidizable so that, once the boom is fully deployed in space, it rigidizes itself and the inflation system is no longer needed. In addition, if the boom is penetrated by small space debris, the boom will maintain its rigidity and not cause deformation to the antenna structure. To support large apertures (e.g. 10m or beyond) without causing any buckling to the small-diameter inflatable boom during vibration, the tube, in addition to rigidization, is also reinforced by circumferential thin blades, as well as axial blades. Second, a controlled deployment mechanism, such as by using Velcro strips, must also be implemented into the system so that, for very large structures, the long inflatable booms can be deployed in a time-controlled fashion and not get tangled with each other. Third, the thermal analysis is another critical element and must be performed for the boom design in order to assure that the inflated boom, under extreme space thermal conditions, will not deform significantly. Finally, the dynamic vibration analysis must also be performed on the inflatable structure. This will investigate the response of the structure due to excitation introduced by the spacecraft maneuvering and thus determine any necessary damping. Several reflectarray antennas have been developed at JPL to demonstrate the technology. These include an earlier 1meter X-band inflatable reflectarray, a 3-meter Ka-band inflatable reflectarray, a half-meter dual-band (X and Ka) reflectarray, and the current on-going 10-meter inflatable structure development. The detailed RF and mechanical descriptions of these antennas, as well as their performances, will be presented during the conference.