SETI bioastro: Ballooning To Mars

From: Larry Klaes (
Date: Fri Apr 14 2000 - 12:16:45 PDT

Date: Wed, 5 Apr 2000 15:38:59 GMT
Subject: [ASTRO] Ballooning To Mars

University Relations
University of Arkansas

Larry Roe, assistant professor of mechanical engineering
(501) 575-3750,

Carolyne Garcia, science and research communication officer
(501) 575-5555,


Ballooning To Mars

FAYETTEVILLE, Ark. -- Every day Larry Roe grapples with questions like: How
do you inflate what does not exist, under unknown conditions, using unknown
materials, for an unknown application? Roe, a mechanical engineering
professor at the University of Arkansas, faces these problems in his work
with NASA and the Jet Propulsion Laboratory to invent inflation devices for
space missions.

"Some people see these questions as insurmountable obstacles," Roe laughs.
"Those kinds of questions can drive them crazy. But to me they are creative

Roe's current challenge is designing systems to inflate structures for
near-term space missions that are in various stages of planning. For
near-term missions, Roe's designs are grounded in known engineering
principles and existing hardware. He is looking at structures that range in
size from a baseball to 50 meters (161 feet) across. Subsequent missions
may call for inflatables that are 3 to 5 kilometers (2 to 3 miles) across.

For missions to Mars or other planets with sufficient atmosphere, Roe
envisions reconnaissance balloons. These small, lightweight devices could
collect and transmit data or carry cameras to provide additional views of
the planet.

A number of inflatable other devices have also been identified for these
missions, according to Roe. These structures include data collection and
communication antennas, solar shields, thermal radiators, solar
concentrators, light sails, landing systems, rover tires and habitats.
Although vastly different in design and purpose, they all have a common
need for some type of inflation gas.

"Currently, devices such as antennas and reflectors are expensive, heavy
and prone to failure," noted Roe. "Inflatable devices can overcome these
obstacles, making space explorations more reliable and affordable."

Inflatable structures are classified according to the type of inflation they
require, regardless of their size. The three main categories are continuously
inflated (CI) structures, rigidized inflatable (RI) structures, and
single-inflation (SI) devices. The gas used to inflate all three types must
be light, non-contaminating to the spacecraft instruments, non-condensing
under given pressure and temperatures, non-reactive with structural
elements and able to be delivered reliably and controllably.

SI and RI devices are only inflated once. SI devices, such as landing bags are
then discarded. RI structures, such as communication antennas, light sails
or solar shields, are made of materials that can be folded and packaged, but
harden once inflated and exposed to sunlight.

CI structures, such as data collection antennas, rover tires or habitats
present a different set of problems. They must be continuously inflated
throughout the life of the mission, and they invariably leak. In addition,
some CI devices can be very large. A reflecting membrane currently
envisioned for the ARISE (Advanced Radio Interferometry between Space
and Earth) mission may be 25 meters (around 83 feet) in diameter.

"Preliminary characterizations studies show that either a tanked-gas or
systems that generate inflation gas via chemical reaction are indicated," Roe
explained. "Our prime candidate is the catalytic decomposition of hydrazine,
which produces a mixture primarily of hydrogen and nitrogen."

Roe is doing conceptual designs for projects that are about 10 years in the
future. He is focusing both on determining good ways to inflate devices and
eliminating things that don't work. For example, subliming solid systems
used in the Echo series of balloons have contamination and control issues
that must be addressed before they could be used reliably.

Optimization is another key issue, Roe indicated. Once a viable process is
determined, it must be made more efficient. Inflation systems have already
been reduced in size by 50 percent, but Roe believes that further efficiencies
and size reductions are possible.

"For the near-term the primary development focus is on RI and CI structures,"
said Roe. "Inflation technology can be incorporated into deployable solar
arrays for power, solar shields for spacecraft thermal management and
antennas for data collection and communication."

Roe is presenting his findings in Atlanta on April 4, 2000, at the American
Institute of Aeronautics an Astronautics Joint Conference on Structures,
Structural Dynamics, and Materials.

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