Selected Articles from the
October 1999 Odyssey
Editor: Craig E. Ward
Editors Note: OASIS is a chapter of the National
Is an economically self-sufficient space settlement feasible on the
Moon or Mars or other bodies in the solar system?
NSS recognizes that the directions and timetable
of human space settlement may very well depend on whether such settlement
can be commercially profitable, or at least economically self-sufficient.
To date, space activists have assumed that sooner or later such favorable
economics would exist, but no one has set forth any scenario that would
rigorously confirm such an assumption.
Accordingly, NSS is challenging the aerospace, economic and university
communities to test the proposition of economic viability by making it
the featured subject of a Special Call for Papers for its International
Space Development Conference, to be held in Tucson over Memorial Day
weekend, May 26-29, 2000.
"There is no question that private enterprise will play a major role
in the development of the high frontier," said Lawrence D. Roberts, Chair
of NSS's Policy Committee. "The papers presented will help to clarify
the issues vital to such development, help formulate international and
domestic space policy and enhance the prospects for commercial success."
THE CALL FOR PAPERS
National Space Society invites abstracts for Papers at its 19th Annual
INTERNATIONAL SPACE DEVELOPMENT CONFERENCE on the subject of: An Economically
Self-Sufficient Settlement on Another Body in the Solar System (e.g.,
the Moon, Mars, Asteroid or Comet). The Paper should describe a space
settlement that is either:
- a "closed" system that, after start-up, is physically self-sufficient
and thus able to function indefinitely without imports which would have
to be paid for; or
- an "open" system that will require the import of resources and the
means to generate income to pay for them. Ideally the space settlement
should generate enough revenue to pay off all start-up costs (including,
e.g., launch vehicles, transportation costs, settlement materials),
but a Paper will be acceptable if it describes a settlement that is
marginally profitable on an annual basis after writing off all start-up
Papers should include technical, regulatory, economic and commercial
assumptions, the anticipated stages of development, with timetables, and
reasonably detailed projected income and expense statements validating
the self-sufficiency in the relevant time periods.
The abstracts must be in English, must not exceed two 8-1/2 x 11 inch
pages (with 1 additional page of graphics if necessary), must summarize
a Paper suitable for presentation at the Conference, May 26-29, 2000,
in Tucson, AZ, and should estimate the length of the Paper. Those submitting
accepted abstracts will be invited to send the complete Papers for selection
and presentation. A Proceedings CD is anticipated. Three copies of each
abstract must be submitted. Abstracts should be submitted prior
to November 1, 1999, but may be accepted on a rolling basis through March
31, 2000. Mail to:
NSS 2000 ISDC
c/o Jeffrey Liss
180 N. LaSalle Street, Suite 2401
Chicago, IL 60601.
of intention to submit an abstract would be appreciated. E-mail inquiries
should be sent to JGLJGL@aol.com.
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By Robert Gounley
takes teamwork to fly a spacecraft. I've had privilege to belong to such
teams at NASA's Jet
Propulsion Laboratory. Unlike the crew of the starship Enterprise,
we seldom encounter life-threatening adventures while exploring new worlds.
Mostly, we endure long hours of tedium punctuated by moments of excitement
- like feeling your stomach unknot when equipment millions of kilometers
away works as well as it did when you tested on the other side of the
However, sometimes the excitement can be completely different.
No one ever said that flying robotic spacecraft isn't rocket science.
It requires a ground-based flight team to plan, test, and radio instructions
to a computer onboard. There's little room for error, especially when
the mission calls for flying past another body. Then the spacecraft, flying
tens of kilometers per second, must sail past a planet or asteroid or
comet, itself flying tens of kilometers per second in a different direction,
at the precise moment when their crossed paths permit a friendly "hello."
All the while, the spacecraft must capture once-in-a-lifetime pictures
using a telephoto lens with a view narrow as a soda straw.
Ironically, encounters can be anticlimactic for the flight team. Beforehand,
uncounted days, nights, and weekends have gone into preparations. By encounter
day, virtually anything that could be done has been done. Now its time
for the engineers to watch their spacecraft perform a graceful minuet
designed to return a wealth of scientific data.
That is conventional wisdom. Deep Space 1 is an unconventional mission.
DS1, as we call it, was built to test fly new technologies for future
deep space missions. No interplanetary spacecraft ever used ion propulsion,
so DS1 is doing it. The same is true for concentrating solar array, autonomous
navigation, and nine other engineering experiments. We built it quickly
and inexpensively. When DS1 launched in October 1998, the small team that
built and tested it handed over the keys to the even smaller team that
would fly it.
We've learned a lot flying DS1. Not everything worked as expected, but
we found ways to deal with the quirks. By summer 1999 planned testing
was complete. There was only one item left for the prime mission - that
was to fly past a small, near-Earth asteroid named 1992KD1 and collect
An asteroid flyby isn't like testing an individual piece of spacecraft
equipment. 1992KD1 is so small, at most a few kilometers wide, that DS1's
cameras could not possibly discern much more than a speck except when
very close. The only chance to capture high-resolution pictures last for
only minutes on either side of DS1's closest approach to the asteroid.
Then, it would be less than 15 kilometers away.
The asteroid, only visible through a handful of large Earth-based telescopes,
was discovered in 1992. That's too little data to chart the orbit to the
precision we required. The best we could do was to keep DS1 aimed for
the center of a 1000 kilometer sphere where asteroid 1992KD1 would most
probably be when DS1 passes by. Only when DS1's cameras detect its moving
target, can the final course be set for rendezvous. At best, DS1's first
detection of 1992KD1 might occur a few days before encounter.
Before this summer, we tended several different activities each week.
Now everyone concentrated on a single, short command sequence to fly DS1
past the asteroid, take pictures, and transmit them back to Earth. Long
design meetings each day were followed by long nights testing the changes
that had just been made. Commands were added, rearranged, and deleted;
with each new version the revision letter crept farther down the alphabet.
Months of preparation would have been normal. The team was doing the
lion's share of the work in weeks.
All the while, DS1 kept coasting towards the asteroid. Periodically,
we'd command a course correction, referred to as a trajectory correction
maneuver or "TCM". Only a few brief pulses from the spacecraft's chemical
thrusters were needed to keep it on target. That is, if we had accurately
judged where the target would be.
|Deep Space 1. NASA artwork
My duties were to direct three TCMs scheduled for 48, 24, and 18 hours
prior to closest approach. All of them would be preceded by an Optical
Navigation activity (OPNAV). This routine turns DS1 so its camera can
sight several large main-belt asteroids against a backdrop of known stars.
These are DS1's landmarks to chart its way. Like a seafaring navigator
with his sextant, DS1 automatically measures angles, computes its course,
compares that course against its desired one, then determines the adjustments
required. If allowed to do so, DS1 even performs the TCM by itself. This
is the work of DS1's autonomous navigation system - another deep space
All this independent action comes with a price. Being a low-cost spacecraft,
DS1 has only a high-gain antenna and it is bolted to one side. Whenever
DS1 turns away from Earth, our flow of data slows to a trickle. We know
little about what is happening until high-rate radio contact is regained
at the end of each OPNAV or TCM. If something were going wrong, it could
be hours before we'd know.
The autonomous navigation system worked well in flight test, but now
the stakes were higher. By definitions set when the DS1 project started,
our mission of testing technologies was complete. An asteroid flyby was
a convenient final validation being done with far less preparation than
conventional missions. Officially, we were doing a best effort encounter.
Unofficially, we all knew that DS1 would be remembered by the asteroid
1992KD1 was a temporary name selected for the date of its discovery.
When DS1 announced it would be flying past this undistinguished object,
a scientific committee met to choose a permanent name from among hundreds
of suggestions. A few days before encounter, a scientific committee released
their decision. The asteroid would be called "Braille" after the inventor
of printed material for the blind. The irony of this name was not lost
on the flight team.
We hoped Braille might be visible before the 48 hour TCM. Indeed, OPNAV
pictures showed an indistinct dot in about the right place that could
possibly be Braille. No one felt comfortable with this identification.
Once more we aimed DS1 for the center of the imaginary sphere where Braille
should be. The TCM went flawlessly.
From the next OPNAV pictures, we saw that the suspicious dot had grown
brighter. It was Braille! We sent DS1 messages to set course for its target.
The 24-hour TCM went off without a hitch.
Post-TCM results encouraged us. From what we could see, DS1 was about
as close to its target point as the most recent images could tell us.
We'd have to wait until the spacecraft was closer before making finer,
but necessary adjustments. We cancelled the 18-hour TCM and set our plans
on what the next OPNAV would tell us. That information would go into the
12 hour TCM. After still more OPNAVs, DS1 would make its last corrections
at 6 and 3 hours before closest approach.
That night, things could hardly look better. Having done my night's
duties, I went home anticipating a quiet encounter day.
I was still thinking that when I arrived back at JPL early the next
morning. There I saw several flight team members huddled over their monitors.
Something had rebooted DS1's computer during the last OPNAV. Onboard recovery
routines placed the spacecraft into a slow spin to await further instructions.
The spacecraft was safe, but unprepared for the encounter.
Ready or not, DS1 would cross Braille's vicinity in less than 15 hours.
There was a lot of work to be done.
TO BE CONTINUED...
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