| Newsgroups: sci.space
Subject: Re: LDEF retrieval fact sheet (Forwarded)
Date: 29 Jun 89 16:46:26 GMT
Reply-To: [email protected] (Tom Neff)
In article <[email protected]> [email protected]
(Peter E. Yee) writes:
> LDEF RETRIEVAL FACT SHEET
> NASA is planning Space Shuttle mission STS-32 in December
>1989, using orbiter Columbia, to retrieve the Long Duration
>Exposure Facility (LDEF). ...
> After more than 5 years in space, LDEF is a unique and
>valuable repository of information on space environmental
>effects. LDEF also has valuable science and applications data on
>board. The data will have critical design implications for
>spacecraft that have requirements for long-duration flight in
>low-Earth orbit. However, before scientists can study this data,
>LDEF must be retrieved. Otherwise, the spacecraft and its
>experiments will be destroyed during reentry.
> Recognizing the significance of LDEF, NASA has been ...
Not mentioned in this press release is that the big push to grab
LDEF before it decays is coming from the Star Wars camp. Most of the
original experiments are shot. (I wouldn't want to be in the room
when they open the seedling chamber, phew! :-) ) But a lot of people,
ESPECIALLY the SDI-nauts, want to know what happens when you leave
things in orbit for years at a time. Which they would of course have
to do. Having neither the spare budget nor the time to fly their own
custom longevity experiments, they view LDEF as a godsend and lobbied
hard to move up the retrieval mission when solar flux upped the drag
coefficient unexpectedly.
LDEF retrieval will be expensive and it could also be risky,
depending on how far the orbit has decayed when Columbia gets there.
Rendezvous and RMU operation in the fringes of the atmosphere hasn't
been done before to my knowledge. I assume NASA knows what it's
doing, but they are skating pretty close to the edge on this one. I
just wanted to point out to the loyal readership why they're
bothering.
"My God, Thiokol, when do you \\ Tom Neff
want me to launch -- next April?" \\ uunet!bfmny0!tneff
|
| Newsgroups: sci.space
Subject: Space exposed tomato seeds are coming home (Forwarded)
Date: 14 Nov 89 23:35:36 GMT
Reply-To: [email protected] (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Terri Sindelar
Headquarters, Washington, D.C. November 14, 1989
RELEASE: 89-174
SPACE EXPOSED TOMATO SEEDS ARE COMING HOME
NASA is offering 12.5 million tomato seeds to budding student
gardeners in the first experiment ever to study the effects of
long-term space exposure on living tissue.
It has been more than 5-1/2 years since the Space Shuttle
deployed 12.5 million tomato seeds, housed in the Long Duration
Exposure Facility (LDEF), into Earth orbit. Next month during Space
Shuttle mission 32, NASA plans to retrieve the 11-ton, free-flying
satellite. LDEF carries 57 experiments concerned with the exposure of
materials to the space environment, one of which is SEEDS.
SEEDS (Space Exposed Experiment Developed for Students) is a
cooperative educational partnership among NASA Headquarters Education
Affairs Division, Washington, D.C., NASA's Langley Research Center,
Hampton, Va., and the George W. Park Seed Co., Greenwood, S.C.
The project is designed as a classroom experiment for U.S. students
in grades 5 through university to conduct open-ended research.
NASA Administrator Richard H. Truly said, "Because this is the
first opportunity for long-duration space exposure of living tissues,
every classroom experiment will be significant. I hope millions of
students will experience this hands-on, one-of-a-kind experiment and
learn that science is fun."
The SEEDS project has the potential to directly involve 4 million
students and 40,000 educators, in 250,000 classrooms.
After LDEF is retrieved, the flight seeds will be returned to
Park Seed Co. where an equal number of control seeds from the same lot
have been maintained in a ground-based facility.
Following preliminary growth tests conducted by plant scientists,
these seeds will be distributed in late February. Each seed kit will
contain 50 flight seeds and 50 control seeds, instructional materials
and computerized data collection and reporting booklets.
Students will conduct classroom experiments, including experiment
design, data gathering, sample comparison and final reporting results.
Upper elementary and secondary levels could compare germination rates
and times, seed embryos, phototropic responses and fruit products.
Students also could consider the impact of varying environmental
factors. Upper secondary and university students could perform
chromosome experiments and population genetics studies.
The tomato seed was chosen because students in all geographic
areas are familiar with the plant; it is relatively simple to
germinate and grow; it is small enough to permit a large number to be
flown; and it is proven to be very hardy. Rutgers tomato seeds are
open-pollinated, nonhybrids and produce plants with comparatively
little variation from generation to generation. Consequently, any
changes in the space tomatoes' characteristics will be easy to detect.
The Rutgers tomato seed was selected because it has wide adaptation
and can be grown in every state.
The SEEDS project gives students the unprecedented opportunity to
be involved in a national, first-of-a-kind experiment that encourages
both active involvement and an interdisciplinary approach to designing
their own investigations to involve decision-making, data-gathering
and reporting of final results.
There is still time to participate in the SEEDS project.
Educators wishing further information in order to participate in the
program should contact the NASA SEEDS Project, Educational Affairs
Division, Code XEO, NASA, Washington, D.C. 20546, and indicate
education/grade level.
|
| RELEASE: 91-113 (7/16/91)
NASA's Long Duration Exposure Facility (LDEF)
yielded a rich harvest of data on the conditions in Earth
orbit and how spacecraft materials and systems performed
in that environment.
LDEF, built by NASA's Langley Research Center,
Hampton, Va., studied the space environment during a 69-
month sojourn from April 1984 to January 1990. It was
NASA's first opportunity to expose a spacecraft, with an
intentionally-selected set of materials samples, to the
harsh environment of space for a long duration and
retrieve the spacecraft and samples for extensive
laboratory analysis.
The LDEF experiments gathered information on space
radiation, atomic oxygen, meteoroids, contamination,
space debris, space systems and life sciences and
produced the following findings:
--A meteoroid experiment on LDEF recorded the
direction and precise time of more than 15,000 impacts.
Analysis will provide clues to the origin and evolution
of both natural meteoroids and man-made debris.
--LDEF was the first satellite to detect beta
meteoroids -- minute particles accelerated by solar
radiation. Its experiments also identified debris
particles from a number of Space Shuttle missions and
apparently from other launch vehicles.
--Several investigators reported impacts on LDEF's
trailing edge. Researchers believe the impacts show for
the first time that debris particles exist in elliptical
orbits.
--The in-orbit performance of protective paints
varied dramatically. White polyurethane paint was
darkened by ultraviolet radiation, but atomic oxygen
continually swept away the darkened paint on LDEF's
leading edge. The latter effect caused these surfaces to
look freshly painted.
--Many of the polymers on the leading surfaces of
LDEF were eroded. Some Kapton thermal blankets
completely eroded away from their experiments. Silvered
Teflon thermal blankets suffered erosion, a decrease in
mechanical properties and darkening and delamination
around impact sites. Silicones and anodized aluminum,
were unaffected by atomic oxygen.
--LDEF gathered a large body of data about induced
radioactivity in aluminum, stainless steel, titanium,
lead, copper and nickel. Researchers found radioactive
beryllium-7 on LDEF's leading surfaces -- the first known
evidence for radioactive isotope accumulation onto an
orbiting spacecraft.
--Three cosmic ray experiments showed good
sensitivity and resolution. The measurements are six
times more sensitive than before.
--Most living specimens remained alive after
exposure to varying degrees of radiation during their
journey in space. Shrimp had shortened life spans and
some genetic mutations. Plants grown from space-exposed
seeds had variegated leaves and flower buds. Some leaf
parts were a normal green, others totally lacked
chlorophyll. These experiments are part of continuing
international studies to increase knowledge of space
environmental effects on biological organisms.
--Very few electrical or mechanical system failures
were caused by the spaceflight environment. Some low-
cost electrical components were used successfully, but
relays were a continuing problem. The tape recorders
functioned well, and data tapes had no loss of stored
information.
--Researchers unexpectedly observed scoring on metal
surfaces that had rubbed together, but saw no evidence of
cold welding. Cold welding is the solid-state metallic
bonding between atoms on opposing surfaces.
LDEF carried 57 different science and technology
experiments. Investigators continue to study the LDEF
results and draw conclusions that will contribute to the
knowledge base for long-lasting space endeavors such as
Space Station Freedom, the Earth Observing System and
exploration of the Moon and Mars.
LDEF: TESTBED FOR SPACE STATION FREEDOM--AND
BEYOND
NASA's Long Duration Exposure Facility (LDEF)
connected a variety of experiments to form a family of
space science applications. Those experiments are
providing a bonanza of data about the long-term effects
of the low Earth orbit environment. A recurring theme at
the first LDEF Post- Retrieval Symposium was how that
information will help the engineers and scientists
planning Space Station Freedom.
Bruce Banks, tasked with finding the appropriate
protective coating for Freedom's solar arrays, said, "We
have looked at various silicones, such as the SiOx
coating and silicon-filled Kapton and conventional Kapton
that could be used on the solar arrays. We think that
the SiOx coating on either side of two sheets of
polyamide Kapton will be sufficient to withstand the
atomic oxygen influence on the solar arrays."
Banks, an LDEF principal investigator from NASA's
Lewis Research Center, Cleveland, explained that the two
sheets are layered together with fiberglass netting and
silicon to give a sandwich effect. This coating should
meet the 15-year materials requirement for Freedom.
Investigators are also looking at the integrity of
LDEF systems data and preliminary results to compare
different coatings available to protect Freedom's large
radiators. Banks said one coating, a black paint called
Z-93, held up very well on the LDEF Marshall Space Flight
Center experiments.
The paint seems to offer several advantages. Its
aerial density is lower and it is significantly lighter
than other paints. It is a high-performance, durable
coating with good long-term performance properties and it
showed little darkening during LDEF's orbital stay.
Z-93 flew on Apollo and Skylab, so investigators
have reasonable confidence in it. "We realize that you
can reduce the amount of power needed on Freedom and save
considerable weight--1200 pounds compared to Teflon--on
the radiator surfaces with Z-93. You'd need a fairly
thick coating of silver Teflon on the radiators to have
them survive for 15 years," Banks said. "Z-93 is now
considered the baseline candidate on the restructured
Space Station Freedom."
"One very important finding from LDEF is how
incredibly stable it remained during its 5.9 years in
space," said Sally Little, liaison between the LDEF
Science Office and the Space Station Freedom office at
NASA Headquarters, Washington, D.C. "Freedom will be
designed to remain stable as well, although its altitude
will differ. LDEF brings home how important it is to
protect the leading surfaces of a space system.
"We are using that information to help us determine
how much shielding we need against the debris
environment," Little noted. "We are confident now,
however, that we don't need as much meteoroid and debris
shielding on the trailing side of Freedom. We can save
weight, reduce the maintenance requirements and
ultimately save money--a direct result of the LDEF
experience."
"It's imperative that the investigators in highly
specialized disciplines come together to integrate,
synthesize and disseminate this information into the
community," said Little, "That's what the symposium was
all about. We must translate this scientific information
into terms that people in other disciplines can
understand. In order for us to know how the electronics
survived, for example, we have to understand radiation
and its effects."
"It's so important to have a mission like LDEF,"
Little added. "It is allowing us to extrapolate data and
compare it with ground data to determine the life of many
materials for future missions. LDEF is definitely
confirming how detrimental the space environment can be.
A 7-day Space Shuttle mission is one thing; a 6-year LDEF
mission is something else."
Looking further into the future, scientists are
considering what the LDEF results mean for the design of
lunar bases and Mars-bound spacecraft. For example, no
radiation effects were observed in LDEF surface
materials, but possible radiation effects were reported
in uncovered solar cells, electronics and quartz crystal
resonators. The effects of directional properties of
trapped protons were clearly observed in aluminum tray
clamps and stainless steel trunnion layers.
"These data will provide a high-precision test of
new trapped proton directional models, said Tom Parnell,
chairman of the radiation special investigation group
from Marshall Space Flight Center. "Due to LDEF's long
exposure and stability, the data base is unique and
important for planning radiation shielding in future
space systems."
LDEF's impact won't be limited to hardware. The life
science experiment that probably received the most
attention was SEEDS (Space Exposed Experiment Developed
for Students), which involved distributing 12.5 million
tomato seeds to over 3.5 million students.
"Reports show that space-flown seeds had slightly
higher germination rates than unflown seeds," said
William Kinard, Head, LDEF Science Office. This may
indicate that space can be used to store seed material in
the future. But the stimulus that this experiment has
p
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