December 13th 05, 12:03 AM
http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_current.html
The PI's Perspective
Next Month, We Aim to Fly!
Alan Stern
December 2005
I have been working on seeing the United States fly a mission to Pluto
since early in 1988. After a few weeks of discussions with colleagues
and a little scheming and ritual screwing up of a 31-year-old's
courage,
my first meeting with NASA officials on this was held on May 8, 1988,
in
the office of Geoff Briggs. Dr. Briggs was NASA's Director of Planetary
Exploration at that time.
In that meeting I asked Geoff, "With Voyager about to arrive at
Neptune,
why isn't NASA even planning a mission to Pluto?" His deceptively
simple
response lulled me into a false sense of security: "Alan, we should be.
I'll see about a study of how we might do that. We'll get back to you."
If I and my "Pluto underground" colleagues had known then what it would
take, how many meetings, proposals, presentations, reversals, setbacks,
and outright cancellations it would take to get that study turned into
flight hardware at the launch pad, we probably would not have had the
courage to take on the task. But who could have known? It sounded so
easy after Geoff's positive reaction to a simple question. And so we
began.
Of course, it wasn't easy. But here we are, about 6,060 days, or 211
months later, and it's finally possible to say: "Next month, we set
sail
for Pluto."
In November, New Horizons made some more great strides forward,
including:
* For the first time, we powered the spacecraft with our flight
radioisotope thermoelectric generator (RTG), and everything
worked
- perfectly.
* Our third stage was completed and delivered for mating to New
Horizons.
* Our Atlas launch vehicle completed erection at Launch Complex 41
and went undertook its "wet" (that is, fueled) dress rehearsal of
the launch count.
* We conducted our final mission simulations and final spacecraft
testing.
* We conducted our final spin balance testing. From the results
obtained, we predicted the mass of the trim weights needed for
balancing the spacecraft for flight, and then from that, derived
a
final hydrazine fuel mass load allowance of 77 kilograms.
* We fueled then the spacecraft with hydrazine propellant for
flight
and checked the fueled balance of the spacecraft with final trim
weights installed.
Regarding fuel, we were able to load 77 kilograms of hydrazine on New
Horizons. The theoretical maximum - that is, a full fuel load - is 80
kilograms. But that's a lot more than we require to fly the mission.
Calculations show we probably only need about 60 kilograms, and we have
long said that our warm-and-comfy zone began at anything over 68
kilograms - some 85% of the maximum possible load. Well, 77 kilograms
is
96% of the max possible load, so we are all very happy indeed.
What made this possible? Simply put, the spacecraft came in a little
light in its final mass, after spin balance weights had been added.
This
is a credit to our spacecraft and payload engineering team in general,
and most notably to Steve Vernon, the mechanical engineering lead
engineer for New Horizons from the Johns Hopkins Applied Physics
Laboratory.
We are now on the heels of launch. And like any flight mission, we're
dealing with a few final demons. For New Horizons, these include some
increased testing of our "autonomy" subsystem - a software package
designed to handle fault detection and correction when we're far from
Earth, some delays in closing out the thousands of checks, reports and
verifications necessary to prove we're ready to be certified for
flight,
and some concerns about rare but real commands that are "dropped" (or
unprocessed) by the spacecraft's Power Distribution Unit (PDU).
All that in mind, we're still on track for the opening of the
Jupiter-Pluto launch window, which opens at 2:11 p.m. Eastern time, on
Jan. 11, 2006.
Ahead of us lies another launch countdown practice drill, some
remaining
testing of the autonomy system under more wide-ranging conditions that
the original test plan allowed for, a lot of paperwork to close out,
and
a series of NASA pre-flight spacecraft and mission assurance reviews to
ensure they are ready to authorize us to count down and launch.
All that said, our little speed demon spacecraft is buttoned up for
flight and its launch vehicle is assembled. There isn't much more good
we can do for our baby here on Earth. Like a child leaving for college,
it's time for the parents to let go and see how she does on her own.
Graduation day is coming. And if all goes well, the Pluto encounter
will
begin just 3,300 days later...
-- Alan Stern
p.s. I plan to increase the rate of my postings to this Web site to
once
every week or so. I also plan to continue that pace through launch, and
during the first few, critical weeks of flight as well. So get used to
more frequent postings.
You might also think about getting used to something else: A spacecraft
en route to Pluto and the Kuiper Belt.
The PI's Perspective
Next Month, We Aim to Fly!
Alan Stern
December 2005
I have been working on seeing the United States fly a mission to Pluto
since early in 1988. After a few weeks of discussions with colleagues
and a little scheming and ritual screwing up of a 31-year-old's
courage,
my first meeting with NASA officials on this was held on May 8, 1988,
in
the office of Geoff Briggs. Dr. Briggs was NASA's Director of Planetary
Exploration at that time.
In that meeting I asked Geoff, "With Voyager about to arrive at
Neptune,
why isn't NASA even planning a mission to Pluto?" His deceptively
simple
response lulled me into a false sense of security: "Alan, we should be.
I'll see about a study of how we might do that. We'll get back to you."
If I and my "Pluto underground" colleagues had known then what it would
take, how many meetings, proposals, presentations, reversals, setbacks,
and outright cancellations it would take to get that study turned into
flight hardware at the launch pad, we probably would not have had the
courage to take on the task. But who could have known? It sounded so
easy after Geoff's positive reaction to a simple question. And so we
began.
Of course, it wasn't easy. But here we are, about 6,060 days, or 211
months later, and it's finally possible to say: "Next month, we set
sail
for Pluto."
In November, New Horizons made some more great strides forward,
including:
* For the first time, we powered the spacecraft with our flight
radioisotope thermoelectric generator (RTG), and everything
worked
- perfectly.
* Our third stage was completed and delivered for mating to New
Horizons.
* Our Atlas launch vehicle completed erection at Launch Complex 41
and went undertook its "wet" (that is, fueled) dress rehearsal of
the launch count.
* We conducted our final mission simulations and final spacecraft
testing.
* We conducted our final spin balance testing. From the results
obtained, we predicted the mass of the trim weights needed for
balancing the spacecraft for flight, and then from that, derived
a
final hydrazine fuel mass load allowance of 77 kilograms.
* We fueled then the spacecraft with hydrazine propellant for
flight
and checked the fueled balance of the spacecraft with final trim
weights installed.
Regarding fuel, we were able to load 77 kilograms of hydrazine on New
Horizons. The theoretical maximum - that is, a full fuel load - is 80
kilograms. But that's a lot more than we require to fly the mission.
Calculations show we probably only need about 60 kilograms, and we have
long said that our warm-and-comfy zone began at anything over 68
kilograms - some 85% of the maximum possible load. Well, 77 kilograms
is
96% of the max possible load, so we are all very happy indeed.
What made this possible? Simply put, the spacecraft came in a little
light in its final mass, after spin balance weights had been added.
This
is a credit to our spacecraft and payload engineering team in general,
and most notably to Steve Vernon, the mechanical engineering lead
engineer for New Horizons from the Johns Hopkins Applied Physics
Laboratory.
We are now on the heels of launch. And like any flight mission, we're
dealing with a few final demons. For New Horizons, these include some
increased testing of our "autonomy" subsystem - a software package
designed to handle fault detection and correction when we're far from
Earth, some delays in closing out the thousands of checks, reports and
verifications necessary to prove we're ready to be certified for
flight,
and some concerns about rare but real commands that are "dropped" (or
unprocessed) by the spacecraft's Power Distribution Unit (PDU).
All that in mind, we're still on track for the opening of the
Jupiter-Pluto launch window, which opens at 2:11 p.m. Eastern time, on
Jan. 11, 2006.
Ahead of us lies another launch countdown practice drill, some
remaining
testing of the autonomy system under more wide-ranging conditions that
the original test plan allowed for, a lot of paperwork to close out,
and
a series of NASA pre-flight spacecraft and mission assurance reviews to
ensure they are ready to authorize us to count down and launch.
All that said, our little speed demon spacecraft is buttoned up for
flight and its launch vehicle is assembled. There isn't much more good
we can do for our baby here on Earth. Like a child leaving for college,
it's time for the parents to let go and see how she does on her own.
Graduation day is coming. And if all goes well, the Pluto encounter
will
begin just 3,300 days later...
-- Alan Stern
p.s. I plan to increase the rate of my postings to this Web site to
once
every week or so. I also plan to continue that pace through launch, and
during the first few, critical weeks of flight as well. So get used to
more frequent postings.
You might also think about getting used to something else: A spacecraft
en route to Pluto and the Kuiper Belt.