Gimbaled array of four
1-m diameter inflatable membrane antennas developed by Glenn
and SRS; installed at Georgia Tech.
To improve the quality and reliability of
space communication, NASA’s Glenn Research Center is developing
lightweight, deployable antenna technology. The Antenna, Microwave
and Optical Systems (RCA) Branch at Glenn is leading two projects
in this area: Inflatable Membrane and Hybrid Inflatable antennas.
Glenn’s RCA Branch is currently developing an agency-wide
large deployable antenna roadmap, which will focus the efforts of
all NASA centers in this area. They are collaborating with Langley
Research Center, the Jet Propulsion Laboratory and the following
organizations on the deployable antenna projects: SRS Technologies,
John Hopkins University, ILC Dover, Cornerstone Research Group,
Infoscitex and Mevicon.
SRS 2.5 meter Inflatable
Radome Antenna System Undergoing evaluation in Glenn's near-field
Three years ago, Glenn began pursuing the
development of large, lightweight deployable antennas. The ultimate
objectives of the project are to develop a deployable antenna
technology that has the following characteristics:
- Surface accuracy consistent with Ka-band operation,
possibly implying active surface control (surface can be adjusted
to compensate for factors like thermal distortion)
- On-orbit rigidization (antenna becomes stiff)
- Aerial densities (antenna mass divided by surface
area) below 2 kg/m2, preferably below 1.0 kg/m2
- Minimal risk deployment mechanism, possibly
- Minimal spacecraft power requirements for deployment
- Articulated feed (provides adjustable phase
and possibly amplitude) for fine beam pointing
- Deployed-to-packaged volume ratios exceeding
4 X 6 meter SRS inflatable
membrane reflector, with rigidized torus, positioned for
testing in Glenn's near-field antenna range.
Of the two types of inflatable antennas, the inflatable
membrane is the furthest in the development cycle since a 4 x 6
meter prototype has already been built. This antenna is made of
thin polymer films that form a reflector surface and a canopy. The
goal is to have the antenna membrane rigidize and maintain its shape
once it has been deployed in space.
Inflatable membrane antennas offer several key advantages over other
types. One possible advantage is that the primary reflector surface
is a smooth, true parabolic surface, which is unlike mesh-type reflector
systems that are composed of small, flat triangular sections to
make them appear parabolic. The antenna’s low aerial density
makes it very lightweight. Finally, the packaging efficiency (ratio
of deployed to package volume) is high since the expandable antenna
can be compacted to fit inside a small package.
antenna concept using a novel shape-memory polymer composite
reflector system for deployment.
The second type of antenna is known as the hybrid
inflatable antenna. This antenna has a shape memory polymer composite
surface and no inflation is necessary. When the antenna is deployed,
solar energy or embedded wire heats the material changing it from
a plastic to an elastic state. Once the material cools, the material
returns to a plastic state and is ready for use as a sturdy antenna.
Hybrid inflatable antenna
concept using a novel shape-memory polymer composite reflector
system for deployment.
Similar to the inflatable membrane antenna, the
hybrid inflatable is a true paraboloid. However, it does not require
inflation or post-deployment rigidization because of its shape memory
polymer material. The concept also involves a fixed, rigid, back-up
reflector in the event of an unlikely deployment issue.
Inflatable antenna technology is vital to extended
missions that require high data rates for space communication. In
the near future, this technology may be used to achieve communication
rates approaching 1 GBPS from a Mars relay satellite to Earth. This
will enhance NASA’s continued efforts to realize the Vision
for Space Exploration by exploring the moon, Mars and beyond.