I.
Existing Technology Currently Undergoing
Augmentation
A.
Coarse Attitude Determination
and Control
Improving
both coarse attitude control and attitude knowledge continues to
constitute an
important dialogue among the SRWG, the SRPO, and NSROC.
The SRWG is pleased that NSROC is dedicating
resources to improving the situation, as evidenced by the presentation
by NSROC
at the last meeting. The SRWG has the
following remarks relative to the current situation and future plans:
1.
Post-flight
attitude determination.
The SRWG is pleased that NSROC recognizes the need
to improve over past
performance. The goal must be to provide
accurate, routine, and easily interpretable attitude data to the
scientists so
they can analyze their data without the need to carry out extensive
(and
expensive) efforts on each payload simply to determine where it was
pointing. The NSROC presentation of 11 June 2002
shows that improvements have been made in the visualization of gyro
data and
that work is underway to verify gyro solutions using other simultaneous
on-board measurements (e.g., magnetometers). It
is clear that many adjustable parameters (e.g.,
gyro drift,
unmeasured magnetometer offsets, and non-orthogonality matrices) are
used in
the current paradigm. The SRWG would
like to work with NSROC to better understand how these parameters are
used and
what magnitudes are ascribed to them for a given flight.
We commend NSROC for embarking on this path
and look forward to the day when such verifications are routine.
2.
Replacement
of Space Vector systems.
The replacement of the Space-Vector supplied systems
(gyros and coarse
inertial and magnetic ACS units) is of paramount importance and urgency. The SRWG is alarmed that this replacement has
been allowed to fall behind to the point that it is not clear whether
missions
currently awaiting design review will use Space Vector systems or
newly-developed NSROC systems. We urge
both SRPO and NSROC to place a high priority on this activity.
3.
Miniature
Daytime Attitude Sensor --
“NSROC(a)”.
On their own initiative, NSROC has placed a
high priority on the development of a new, miniature attitude knowledge
system
called “NSROC(a),” although the motivation is not apparent to the SRWG. The most mature aspect of the NSROC(a) system
is its use of a sun sensor to determine attitude. This
sensor works only for daytime flights,
which account for only a small fraction of the experiments that utilize
coarse
attitude. A horizon sensor will be
substituted for nighttime flights. Both
sun sensors and horizon sensors have been used by the Wallops rocket
program
for decades and have not proven to be as reliable as the gyro for
providing
accurate and routine attitude data to the experimenter.
Since the NSROC(a) system has now been flown
on numerous payloads, presumably each time as a test bed, we would like
to know
how well it has performed with respect to its absolute accuracy -- e.g., body
azimuth, elevation, and roll position (or
Euler yaw, pitch,
and roll) relative to a fixed reference system on the earth. In this regard, traditionally, absolute roll
position has been the most difficult parameter to reliably ascertain
(to within
1 degree), whereas body elevation and roll rate are comparatively
simple.
The
SRWG is puzzled as to why the NSROC(a) has received a priority in
development. We believe that the
developments most urgently needed in coarse attitude systems should
emphasize
replacement (and improvement) of the capabilities now provided by the
Space
Vector gyro systems. We wonder if the
development of the NSROC(a) has been largely driven by the
applicability of
this system to non-NASA missions.
B.
Fine Pointing ACS and the StarTracker 5000
The SRWG is concerned
about the lack of progress toward implementing the
ST5000 fine pointing star tracker (which has been discussed at several
previous
SRWG meetings) as well as the apparent reluctance of NSROC to fully
investigate
its potential for Lost-in-Space (LIS) tracking. The
report of the flight performance of the ST5000
from last December is
encouraging, despite the failure of the camera lens.
However, no additional test opportunities
were discussed or appear to be scheduled except for the initial flight
of the University of Wisconsin FUSP payload in late 2003. This schedule is troubling, because of the
importance placed by both the SWRG and NSROC on transitioning from the
aging
Ball trackers to a more modern system.
The SRWG expects the
ST5000 to provide a dramatic improvement in
attitude control by permitting the targeting of fainter guide stars and
potentially the direct acquisition of the star (science) field without
slewing
between two fields (via LIS mode). The
latter
capability has the potential to increase time available for science
operations
by 10% or more. The ST5000 also
represents a physical change from the Ball trackers. Several members of
the
science community are also in the design phase of new experiments where
they
must make the decision as to whether they can use the ST5000 or must
make the
necessary compromises to accommodate the existing units.
The SRWG believes
that the approach to the development of the ST5000
could be greatly improved. Funding
levels are low, timelines are ill defined, and only minimal NSROC
resources
appear to be committed to this urgently needed, valuable sub-system. This compares poorly with the effort level
expended on the NSROCa system, for example, which the SRWG regards as
having
much lower priority than the ST5000. In
this regard, the SRWG make several specific recommendations:
1. An implementation plan for the ST5000
should
be developed that clearly outlines the roles that NSROC and the
University of
Wisconsin (UW) will play in the flight qualification of the ST5000. This should include a timeline of development
including potential test launches, stages of use (Ball replacement
only,
followed by LIS), and a target date for the replacement of the Ball
tracker.
2. A line of
communication between NSROC and
experimenters should be opened concerning the availability of the
ST5000 for
testing. Many community members are
willing to support test flights that advance this program.
3. A feasibility study
with UW
should be conducted concerning the different ways in which LIS tracking
can be
used with the existing ACS and what costs would be involved.
C.
DS-19 and the S19-D Guidance System
The
SRWG shares NSROC's and White Sand Missile Range’s (WSMR's) concern
over the
recently identified possibility of a Black Brant IX vehicle exiting the
range
boundaries in the event of a hardware failure on the DS-19 that results
from a
``hardover'' canard condition after T+15 seconds. Range
safety is the highest priority of any
mission and the possibility that a vehicle could exit the range within
the 3
second window required for the missile flight safety officer to
activate the
command destruct is cause for the highest concern.
However, the SRWG
points out that the envisioned solution, namely
restricting the control loop to the old S19 control loop (guidance
through T+15
seconds), is not the only possible solution. We
note that at least four other solutions were
proposed after NSROC's
DS-19 return-to-flight presentation at the June 11 SRWG meeting. These included: (1)
computer activation of the command
destruct issued from the ground; (2) autonomous destruct issued from
the vehicle;
(3) a canard hardover condition detect and cable cutout system; and (4)
a
creeping canard angular range restricter that gradually reduces canard
authority towards the end of the burn where the full angular range is
not
required for control.
The SRWG believes
that at the present time the parameter space for a
possible solution has not been fully explored. We
also believe that reverting to the old S19
control loop is a waste of
a highly desired feature of the DS-19, namely full guidance through
Black Brant
burn-out and the resulting low impact dispersion, which is
in-and-of-itself a
safety feature. Hence, we strongly recommend that NSROC and WSMR pursue
a
solution for the full return of DS-19 capability (full guidance through
BB
burnout at T+44 seconds)that will provide the required safety margin
for
missile flight safety.
II.
New Technology Currently Being Implemented at
Wallops
A. GPS Based Altitude
Event Triggers
The
SRWG applauds NSROCs proactive development of the GPS Event Module
(GEM) by the
telemetry group. This technology has the
potential to significantly increase the observing time for science
payloads. The experimenter will no
longer have to make conservative estimates based on historical booster
performance to set timer events with large (2 or 3 sigma) margins. This allows instruments to turn on, open
doors,
deploy booms, or begin maneuvers and observations earlier than with
timer
events. Similarly on descent, the GEM allows experiments to be shut
down and
parachutes deployed at a later time than conservative timer settings
would have
allowed. Finally the GEM obviates the need for experimenters to include
altitude sensors as fail-safes or event triggers in their payloads,
reducing
cost and complexity. This is potentially
a major development by NSROC and promises to be a great benefit to the
experimenter. That said, the SRWG would
like to see more information on this system including reliability
estimates and
data, the possibility of adding redundancy and how exactly the
traditional
timer events will be used as backups. The
system will not add value to the experiment
unless the timer backups
are set using optimistic values for motor performance.
Thus redundancy and reliability are keys for
making this highly desirable technical development a success for
science payloads.
B. Patriot Rocket
The
SRWG was very pleased to learn of the recent development of the Patriot
rocket
to provide an alternative launch system to the Brant, including both
the single
stage Brant and the Terrier Brant system. In
addition to the higher performance (i.e., broader
payload capacity),
the cost savings are important for the program overall.
We look forward to more information
concerning the introduction of the Patriot rocket into NASA’s inventory.
C. Advance
Engineering Computer Design
The SRWG applauds the
use of state-of-the-art advanced engineering
computer aided design tools (e.g., SolidWorks@3D)
in the mechanical design of payloads. Such
software provides a better design, saves time,
and calculates mass
properties and other engineering parameters. Furthermore,
by encouraging the users to submit
their experiment lay
outs in the same (or compatible) computer packages, the payload design
is not
only improved, but also fit checks can be made on the computer and the
design
optimized in a more efficient manner.
III.
Technology for the Future
A.
Technology Roadmap
The
SRWG is encouraged by the efforts that WFF has made recently concerning
implementation of new technology and new techniques, and updating of
older
hardware. We are concerned, however,
that if undirected and unplanned, these efforts may not be used to
optimally
advance the research efforts of the NASA science community. Further, we recognize that NSROC may focus on
developing technology that enhances their ability to acquire non-NASA
new
business at the expense of the NASA science community needs. We would like to better understand how NSROC
delineates, if at all, between R and D efforts for NASA projects and
those, for
example, for DoD. Are their development
resources for each effort that are accounted for separately?
From
the perspective of the NASA research scientist, the insistent science
requests
for "more time on target" and "more and smaller sub-payloads to
higher altitudes" appear to be most effectively addressed with
innovative
hardware and clever software. Indeed,
the NSROC engineers can implement just about anything, given enough
time and
money. However, a balance must be struck
between the endless requests of scientists and the limited resources of
engineering design time and funds for prototypes and testing.
To
achieve such a balance we look to the NASA Sounding Rocket Program
Office
(SRPO). One way of organizing such
information is a technology "roadmap". Inputs
to this roadmap include (a) science
needs requests from the user community, including priorities, and (b)
engineering technology ideas and possibilities from the NSROC
engineering
community, including costs. The output
of such a roadmap from the SRPO should be a balance between the urgency
of the
science need and its expected scientific impact in the community, and
the costs
of the engineering implementation. An
important consideration is the length of time needed to implement the
new
technology, as some small projects can be completed quickly to meet a
specific
goal and other longer-term developments can be done more slowly and in
parallel. Such a roadmap, once
initiated, should be perpetuated as a "living document", wherein
NSROC engineers (or others) can post potential new technology ideas,
and
scientists can post wish-lists.
At
the last meeting, the SRPO stated its intention to facilitate this
endeavor. The SRWG fully endorses this
initiative and believes that the SRPO is uniquely suited to both create
and
monitor a sounding rocket technology roadmap, matching up needs and
possibilities,
and optimizing the use of our limited community resources.
For our part, we believe that the SRWG can
help define and communicate scientific user input to the roadmap. We look forward to working with the SRPO on
this exciting new aspect of the program.
B.
The “Big Gun”
The ability to fire
small ballistic payloads from a large gun, developed
by the DOD during the 1960's, presents potentially significant new
capabilities
to NASA's suborbital program, particularly with regard to lower
thermospheric/ionospheric and mesospheric investigations requiring
multiple
payloads launched at regular intervals over a period of several hours
or
several days. The proposed gun launcher
augments a particular strength of the sub-orbital program
-- namely providing the
only means of directly sensing
the region of the
earth’s upper atmosphere between 40-180 km. Furthermore, the types of
experiments made possible by this technique loom important as
NASA-sponsored
researchers are pressed to better understand space weather and
climatology of
this region and others.
The SRWG heard an
excellent
presentation introducing the idea of using the large gun and some of
the
expected science return if it could be returned to use as a scientific
investigative tool. The SRWG strongly
recommends that NASA undertake a feasibility study to determine whether
it is
possible to return the remaining big gun (in Yuma, Arizona) to operation, and
what are the
costs of doing so. This
study should be conducted as soon as
possible, because DOD support of the facility may lapse in the near
future. This implies that urgent action
may be needed in order to preserve the facility and make it operational.
IV.
Welcome To Phil Eberspeaker
The SRWG extends a
very warm welcome to the new Chief of the Sounding
Rocket Program Office, Mr. Phil Eberspeaker. Many
of us remember Phil as a payload manager and as
the leader of the
development team that helped implement NSROC. We
believe that Phil Eberspeaker is very well
qualified to serve as the
Chief of the Sounding Rocket program. He
brings much knowledge of how sounding rockets work, management skills
necessary
to keep the program on course, and leadership skills to guide the
program to
new and fruitful directions. The SRWG
looks forward to working with Phil to advance the unique scientific
research
tools that sounding rockets provide to the nation’s space program.
NASA Sounding Rocket
Working
Group
Dr.
Robert F. Pfaff, Jr. (Chair)
NASA/Goddard Space Flight Center
Dr. James Clemmons
Aerospace Corporation
Dr.
Joseph Davila
NASA/Goddard Space Flight Center
Dr.
Walt Harris
University of Wisconsin
Dr.
James LaBelle
Dartmouth College
Dr.
Kristina Lynch
University of New Hampshire
Dr.
Stephan McCandliss
Johns Hopkins University
Dr.
Scott Porter
NASA/Goddard Space Flight Center
Dr.
Charles Swenson
Utah State University
Dr.
Erik Wilkinson
University of Colorado
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