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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 contractor, 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 five 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 five 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.