DART Webcast:
Mission Overview and Q&A
Tiffany Nail: As I mentioned at the top
of the program, DART is a test of new NASA spacecraft technology.
Here's NASA DART project manager, Jim Snoddy, to give us
a closer look at the mission's goal in advanced technology.
Jim Snoddy: Hi, my name's Jim Snoddy, manager of the Demonstration
of Autonomous Rendezvous Technology program. The DART spacecraft
started here at Marshall in 2001 with our prime contactor,
Orbital Sciences Corporation in Dulles, Va. Marshall Space
Flight Center has provided a key role in testing the facilities
and flight software to support the DART program. The DART
program has consisted of many testing throughout the country,
from Florida to California to Huntsville. All these components
have now been tested. The spacecraft is approximately 6 feet
in height and 3 feet in diameter and weighs approximately
800 pounds. It consists of three compulsion systems to carry
out the mission objectives. It has two reaction control systems
made up of cold gas systems and a hydrazine system for the
circularization and de-orbit phases of the mission. The Demonstration
of Autonomous Rendezvous Technology consists of four major
events. The first event being the drop from the L-1011, the
second event is the actual rendezvousing with the existing
satellite and locating it on orbit. The third phase of the
mission is the actual rendezvousing and the proximity operations,
culminating in the de-orbit completion of the mission.
Nail: Were happy to have Mr. Jim Snoddy here with us on
NASA Direct! Welcome.
Snoddy: Well, thank you, Tiffany, it's exciting to be here.
Nail: Jim, we just saw an overview of the
science and technology behind the DART mission. What is your
role with the DART mission?
Snoddy: I’m what's known as the NASA project manager.
I'm responsible for all the budget and schedule and technical
performance and all the risk for the mission. I have the
luxury of also working with all the other various centers
-- KSC, Goddard Space Flight Center and all the other centers
-- to make the mission come together. So I get the joy of
bringing all the money and making it all come together.
Nail: Tell us what we can expect 24 hours after launch.
Snoddy: Well, 24 hours after launch, we should have advanced
the technology for NASA to go on a crew exploration vehicle
one day.
Nail: Our DART mission question boards have been abuzz
over the past few weeks. You've been kind enough to help
us answer many of those questions, so let's get started right
now.
Snoddy: Fantastic.
Nail: Our first question comes from Tom from Huntsville.
Will the DART mission's capabilities be used in the CEV?
Snoddy: Well, DART is the first thing out for the new exploration
initiative, so the intention is, DART is a technology development
program to enable the CEV to do one of the things we need,
which is to autonomously rendezvous and dock in space. With
that capability, we'll be able to many objects together in
space and DART is the first thing out of the gate, so it's
anticipated to have a major impact on the CEV program.
Nail: David from Melbourne: What if the
rendezvous does not take place due to a technical hitch or
other interference, such as a solar flare or otherwise?
Snoddy: That's a very good question. We
have requirements, so we can not launch unless the solar
flares are within a certain requirement. We assessed that
requirement today, currently for the launch date we are currently
projecting no solar flare activity will interfere with us,
but we'll assess it again before the launch.
Nail: Al from Burlington: What are the differences between
the DART, the European Automated Transfer Vehicle (ATV) and
the Russian Progress/Soyuz Automated Approach and Docking
systems? Are the spacecraft compatible with the universal
docking ports on the ISS?
Snoddy: There's many ways to dock in space. The Europeans
and the Japanese and the Russians are all developing technologies
to dock in space. DART is one application of a technology.
We use what's called an advanced video guidance sensor. The
sensor is an optical sensor that looks at the signal and
bounces back and forth to calculate the differences. The
Europeans are doing similar things, so they use actual visual
recognition, and the Russians use radar frequencies. They're
all applications of technologies. DART is taking it one step
farther. DART is a total autonomous mission. Everything is
done automatically, once we let go of it from the L-1011,
there's no human intervention, so it's trying to take it
one step farther with total automation on the part of NASA.
Nail: Junichi from Japan: Is DART going to take the
place of the Russian Progress cargo ship for ISS without
Space Shuttle missions in the near future?
Snoddy: Well, DART is a technology program
to advance the technology. DART is trying to take what we
currently do and make it better. The current systems are
heavier, take large antennas; DART is small and compact,
so it is a technology development program to advance the
state of the art to one day make it better. I mean currently,
pilots do it, there's automated ways of doing it with onboard,
with pilot intervention. DART goes to totally automate all
those systems for future applications.
Nail: Junichi has another question. Could you tell me the
difference between the Russian Progress cargo vehicle and
DART?
Snoddy: Well, again, DART is a technology demonstrator to
take these activities one step further. Many systems now
are remote, pieces of it are automated. DART takes it from
end to end from the time we drop it from the L-1011, DART
automates everything. Many systems have to go in and take
input from the ground with lots of engineers and many tweaks
to automate things. DART does that all. And DART also has
a six degree of freedom, it can control X, Y and Z, pitch,
yaw and roll to precisely come in with a fine-tuned docking
and bring two objects together and gently touch them together.
Nail: Frank from KSC: Why demo the spacecraft by approaching
to only 5 meters? Why not even closer? If it's because of
limitation of the AVGS tracking system, what other sensor
systems would be used for closer ranges towards docking?
Snoddy: DART is using the existing satellite which is currently
in orbit, called MUBLCOM. It was put up in 1999 for the potential
one day application to go up and rendezvous with a satellite.
At the time, no docking mechanisms existed, so DART was never
intended to dock. We would love to dock with it. Other programs
in the future will go ahead and dock.
Nail: Our next question comes from Rich from Elk Grove.
During the recent ground tests, a number of maneuvers were
demonstrated, including a collision avoidance maneuver, horizontal
approaches toward the target satellite, and moving to a docking
and hold position to within 16 feet of the target satellite.
How were these tests conducted on Earth to simulate what
happens in space?
Snoddy: We have at Marshall Space Flight Center what's known
as a flight robotics laboratory, where we actually take the
flight computer and the AVGS and we bring them into the facility
and run through all the simulations from the ground and make
sure they can all talk together. We brought it in from 50
meters into 5 meters and made it do all the maneuvers it
needed to do on ground, which insures that when we get in
orbit, all these things will work. So we do everything we
can on the ground to prove the success as we get into the
orbit.
Nail: Pawan from Sharjah: What type of engine will be used
to propel the DART, and what will be the maximum speed attained
by the spacecraft when it reaches the polar orbit? Also,
what type of technology has been applied on the spacecraft
to prevent it from the solar flares and other harmful radiation
in space?
Snoddy: Well, starting from the end of it, all the compounds
in DART are radiation hardened and gone through the test
to make sure we don't have any radiation effects or what
we call single-event upsets. The DART system is powered by
many systems. We actually utilize the fourth stage of the
Pegasus system, which has a hydrazine system we call HAPS,
so we take advantage of the fourth stage of Pegasus to fly
with DART. We also have two other systems called RCS, reaction
control systems, which are cold gas nitrogen systems that
actually are in a tank and they have a blow down to prepare
the propulsive force to do roll control and to actually tweak
and move the vehicle right up to the spacecraft.
Nail: Pawan has another question. What is the mission plan
after the docking takes place? Will it have the technology
to detect any problem in the spacecraft it's docking with?
Snoddy: DART is programmed to think of all the contingencies.
It is a total autonomous mission, so we've thought of all
the scenarios it could possibly have and we've run what we
call Monte Carlo simulations, and we run thousands and tens
of thousands of cases over the last year to simulate everything
that could happen. So DART has the ability to see this happen,
it knows to go do this. So it can move through all the steps,
so basically it's totally autonomous, and has been factored
all the things we can think of humanly possible to make the
mission successful.
Nail: Ron from London: Since this is an orbital rendezvous
mission and not an Earth resources one, why does it need
a polar orbit?
Snoddy: Well, DART doesn't necessarily need a polar orbit,
but the MUBLCOM satellite was already in orbit in a polar
orbit, so satellites cost hundreds of millions of dollars,
so it was cost-effective to use the existing satellite. The
technology, whether it be a low Earth orbit or polar orbit
or on Mars or on the Moon, once you've demonstrated the technology
in space, the application will apply to all. It was just
a cost-effective technique to use an existing satellite that
was already in polar orbit.
Nail: Pawan wants to know more information. The Space Shuttles
will retire after 2010, as said by Mr. Bush, and a new exploration
vehicle will be made which can travel in space as well as
even land on planets. If the DART test is successful, how
will it be helpful to such an exploration vehicle which has
not been invented until now, and for which the research is
still going on?
Snoddy: Well, one of the reasons we do research is to get
the technology ready for when the crew exploration vehicle
comes online. One of the things is to reduce the risk and
have the technology on the shelf when the CE vehicle is eventually
built. We already know from our trade studies we need to
do dockings, whether they be on Earth or on Mars or on the
Moon, things have to come together in space and be able to
come apart, touch each other... We also have the need for
cargo vehicles to go into space without a pilot, so DART's
kind of like an autopilot on an airplane. It'll be able to
take things into space very easily, without having to have
a man in the loop or anything, so it'll be instrumental no
matter what thing we end up doing for the president's vision.
Nail: Junichi from Japan asks: Is DART going to play an
important role to assemble the modules of spacecraft that
will explore NASA's future on missions to the Moon and/or
Mars?
Snoddy: That's one of the exciting things about DART is,
it works for whether it's space station, CEV vehicles, when
we go to Mars or Moon, you always have to take objects and
put them back together, from the Apollo and Gemini days,
one of the key things is always bringing objects together
in space and going down to lunar surfaces back into orbit.
So things always have to come together in space and the greater
the distance gets from the Earth, the more autonomy we’ll
need to do these things in space.
Nail: Our last question comes from Matt from Radford: I
know that DART will carry with it a video camera designed
to give visual confirmation of rendezvous with MUBLCOM. Unfortunately,
this rendezvous will take place hours after the launch coverage.
Is there any way we will be able to see this video?
Snoddy: Yes, we put the camera on there to independently
verify what the AVGS -- which is the eye of DART -- will
be having lasers, but it will only have dots telling the
distance. The camera will be located side by side to see
exactly what it will see. We'll get that data telemetry during
the night, we'll have it on the webcast, it'll be available
and it'll come out about every hour during the night. So
we'll have that data available as it comes out.
Nail: That concludes our Q&A session today. Thank you,
Jim, for being with us today at NASA Direct.
Snoddy: Thanks, Tiffany.
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