Dr. Greg Chavers, Test Lead, Marshall Space Flight Center, Huntsville, AL
- Thursday, 01 November 2012
NTB: Through that whole process, what was your biggest technical challenge?
Dr. Chavers: There are two challenges. This optical guidance is very similar to an automated rendezvous and capture requirement, in order to provide autonomous updates to a vehicle on orbit. We were developing techniques and algorithms using a very inexpensive camera that we have onboard. We had challenges to go through with the image processing because our onboard computer has limited processing capability. We’re actually using a RAD750, which is a spaceflight-qualified processor. It is very sturdy, but limited in processing capability for such a small package. One challenge was to process the images with that computer, while still proving the controllability. The computer does operate all the onboard systems.
The other challenge is to make sure all the subsystems work correctly, because this is a vehicle system. Any subsystem can malfunction and cause the whole system to have a bad day. Having flown almost 30 times, one of the challenges is to make sure our younger, new engineers pay attention to the trends of the performance system and treat it almost like a launch vehicle.
NTB: How many engineers worked on this project, and how did these teams work together?
Dr. Chavers: When we first started, we were building this as a demonstrator for our controllability, but we also had assembled a design team to design the real spaceflight implementation of this. We were put on hold because of budget shortfalls within the Lunar Quest Program. We had the team assembled from Marshall Space Flight Center and Johns Hopkins University Applied Physics Lab, and we had not built hardware directly with each other before. We had to go through the processes of how each organization designs hardware, integrates hardware, and operates hardware. That’s how we intentionally went about with the teaming.
And we actually included as much of the spaceflight implementation we could afford at the team. We did landing legs with energy absorption, which was very similar to what we would do on the moon. We used the same software and ground system implementation we would use when we were going to the moon. We did not use the exact same propulsion system, because the propulsion system for the moon is very high performing and a little more costly than what we use for the test vehicle. For the test vehicle, we’re using 90 percent hydrogen peroxide -- very simple system, very green, and not expensive at all, so we can do many test flights with a low budget. It does simulate what the high performance thrusters would do, in that they’re pulsed operation. It’s just that the specific impulse is not good. In other woods, the gas mileage is not as good for that propellant.
We also included the Von Braun Center for Science & Innovation. The Teledyne Brown Engineering here in Huntsville also participated in the testbed, to actually go fabricate these non-flight like thrusters that we were using. It was a diverse team, and organizationally challenging to do a small quick project like this. The people who were on the team were all behind it, so we were successful just because the people on the team wanted it to be successful, and we all worked together. The organizational diversity was challenging, but we clearly stated who the lead on the team was, and who had the technical authority. Everyone on the team recognized that, and we were able to move forward quickly.
NTB: How do you see these being used in the future?
Dr. Chavers: For this testbed, we’ve already demonstrated controllability. We’ve already demonstrated that we can update the guidance autonomously in real time. One of the challenges is to demonstrate that we can do hazard avoidance with the testbed. Our friends that are working Morpheus are planning to demonstrate the Autonomous Landing and Hazard Avoidance (ALHAT) technology.
This technology is built for small robotic landers, so for hazard avoidance, it would have to be a very low-mass, low-power system to do that technique. We’re thinking about ways to do that, and working with our friends at Jet Propulsion Laboratory and the Applied Physics Lab as well.
The future for this testbed is allowing engineers to get some hands-on hardware [experience] using the full six-degree of freedom vehicle. It would be a demonstration, not a verification or validation unit for demonstrating other sensors. For the robotic lander project at Marshall, this has been a very low percentage of our investment: About five percent of the total investment on small robotic landers went to the testbed. We have other subsystems that we are maturing, and that are ready for infusion into a real spaceflight implementation.
NTB: You mentioned debris capturing. Are there other applications for a lander that has the autonomous rendezvous and capture capabilities?
Dr. Chavers: Maintenance on satellites. Refueling the satellites. Actually getting to assets on orbit if there are communication issues with those satellites, to retrieve them and get them back to a space station to be repaired and redeployed.
Landing on the moon or rendezvousing with an asteroid is one application. Landing on the moon, trying to navigate to a specific target on the moon, is an application. There are both landed and free-flight orbiting applications for this technology.
NTB: What are you working on now? What are your day-to-day responsibilities?
Dr. Chavers: The Science Mission Directorate at headquarters is what has funded this effort for the past several years. Due to the budget challenges that we currently have, my day-to-day activities now include informing the leaders at NASA of the capabilities that we’ve acquired, and the knowledge that we’ve learned through this testbed, as well as the testing of other subsystems, to infuse these to accomplish NASA’s near-term mission. In particular, we understand that we have enough technology now to build a small lander to land on the moon within the next three years, and the challenge is basically funding. There aren’t technical challenges involved in that right now.
NTB: What is your favorite part of the job?
Dr. Chavers: The actual test of the Mighty Eagle is very exciting. It’s a big adrenaline rush to know that something you’ve worked on, something that we’ve built on very low budget, is actually operating. It’s exciting when the system works. But the best part of the day is the team that I have to work with. Everybody is very optimistic and wants to contribute. It’s nice being a part of something that’s bigger than you -- a team that’s bigger than the sum of the parts.
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