Lessons from Mars: Inside Two Decades of Rover Design and Operation
How Lessons-Learned Contribute to Future Success
by Peter Illsley, Principal Mechanical & Thermal Engineer
Many organizations make deliberate effort to capture lessons-learned in order to improve, usually with mixed success. In order to truly learn a lesson, we must first recognize that lessons are being taught to us all the time – the little setback, the major failures, surprise discoveries, the seemingly random advice that comes to us from peers and colleagues. These are all lessons.
The real trick is learning the lesson. It's not enough to receive the information, we have to pursue it. We have to be curious enough to follow every part of the lesson and ask the all-important “why” questions. On the surface, the lesson may seem obvious. However, the real crux of the issue may be many layers deep. We have to admit our biases and acknowledge our ignorance in order to let go and clear our minds. We can then get much more proactive about educating ourselves and others about the details. Only then can the lesson be truly learned.
Past experiences are a treasure-trove of lessons if we’re tuned in. The single most valuable experience that has guided me in my career has been to create a design and follow it from cradle-to-grave, a path I've taken many times.
“Traveling down the winding road from paper sketches and cardboard mock-ups to initial designs and prototypes, pressing onward through final detailed analysis and rigorous testing, and then having to integrate the hardware into the final spacecraft assembly flow on the way to the launch pad has been invaluable in approaching the next designs.”
Living this path provides exposure to vast array of experiences – some painful, some ecstatic, and all thrilling. The key is to pay attention to the details of these moments and draw from them the real truths of cause and effect. It's a curiosity that's hard to teach sometimes, but the benefit becomes very clear once you pass through the cradle-to-grave experience even once.
The Lessons of Spirit and Opportunity Mars Exploration Rovers
An experience that will stick with me forever is the build of the hardware for Spirit and Opportunity on the Mars Exploration Rovers (MER) missions and how it affected our choices as we went on to design the Curiosity Rover – launched in late 2011 and landed on Mars on August 5th, 2012.
Early on in the design of the internal packaging of the MER Rover systems, we made a decision to treat the rover body as a box and install the Rover Electronics Module from the top and then close the box with the Rover's structural lid on top which held the solar arrays, the communications antennae, and science camera mast. Further, we had located the Rover's battery in the bottom of the body, underneath the electronics module to help the center of mass a little bit lower to the surface.
The processes for installing all of that equipment were lengthy and very risky with damage to hardware always a concern and a constant threat to the immovable launch date. I personally lost many nights of sleep every time I knew we were either installing or removing that hardware from the Rover.
In the course of the build and test of the Rover, the test battery had to be swapped out for the one intended for flight. To get to it, we had to remove the equipment deck and the electronics module in several shifts of harrowing work only to take out the battery and put in a new one. Had we decided in the design phase to question our earlier assumptions about the battery location, we could have cut down the number of highly-risky operations and saved a lot of time and stress-driven gray hairs.
In addition, a late discovery was made that could have killed the mission and a rework had to be made to one of the electronics boards inside the Rover. We had to pull off the Rover equipment deck and remove the board from the inside of the Rover while it was stowed on the lander. This was something we had never done before, never planned to do, and was one of the riskiest things we had ever done with the hardware. This unexpected late hardware access drove us to ensure we'd be better prepared in the future.
Reaping the Rewards of Lessons-Learned in Curiosity’s Design
In designing Curiosity, we faced a whole new set of challenges, but we knew we never wanted to repeat some of the MER experiences ever again. This forced us to take a look at our designs through the lens of the past. We made a conscious decision to give ourselves access to any one component inside the Rover as late as humanly possible in the spacecraft build so that if the worst should happen, we could deal with it and still make the launch date.
The idea was that if we needed to repair something very late in the spacecraft testing, we could de-mate the heat shield from the spacecraft, exposing the Rover's bottom panel and all the internal components in just a single shift of operations. We also placed components in the Rover such that the removal of any one component would not require the removal of any other. This philosophy literally turned the Rover design upside down. Instead of a box with a lid like MER, the Rover body was now a box in which we had to install all the components from the bottom to hang them from the lid. Nobody else liked it initially. It went against everyone's common sense to have the Rover upside down all the time, but we stuck to our hard-earned position and in the end our tenacity and critical planning paid off, sometimes in unexpected ways.
During initial testing of the Curiosity Rover's electronics in the spacecraft cruise configuration, a serious thermal problem was discovered on one of the Rover's power electronics modules. The bolts holding it in were slightly too long and prevented the module from being properly clamped to the thermally conductive structure and the unit was overheating badly, putting a stop to the very expensive spacecraft thermal vacuum test. Had the component not been hanging from the lid, we never would have found this issue until in flight when it would have been potentially fatal to the mission.
Much later in the testing of Curiosity's drill and sampling hardware, an electrical short was found in the drill mechanism. The flight Rover was already in Florida at the launch site, days away from being closed out and ready for the spacecraft's final stack. A board had to be removed to add in a protection circuit element and a ground path had to be added to the Rover. In a shift and a half, we were able to remove the bottom panel, remove the board for rework, and install the new ground path.
Two days later, after rework we re-installed the board and panel and were able to send the Rover on its way to the pad. This ability greatly reduced the amount of risk in such a late operation and was enabling in making the launch date.
Objectivity is Key to Understanding What Lessons Need to Be Learned
Many times, we need to reflect on the successes just as much as the failures to be able to do even better in the future. Being able to take an objective, dispassionate look at our own successes and identify the points where we truly made an impact, and the points where we may have fallen short of expectations, or those close calls where we were lucky is crucial.
We must internalize those differences in our successful endeavors in order to prepare ourselves for the next challenges. It instills in us a practice of looking far ahead and plotting out how our decisions in the early phases may enable us or constrain us.
“This practice is equal parts creativity, fear, imagination, and recall”.
As we've built our experience base, we are continually refreshing and educating ourselves to pull from the past to guide us into the future. We constantly ask, "how will I have to react to the decision I'm making now when I'm living with the problems it creates even years in the future?" This mindset will continue to serve us very well in solving some of our next seemingly-impossible challenges.