Keep me honest here. I do not want this post to get mired any political entanglements. Let me know if I stray from that goal.
How do we get to Mars? No, I’m not talking about orbital trajectories. No, I’m not talking about the 26 month interval for missions. All of that is pretty well understood. What I’m asking about is the best path to go from where we are now in the manned and unmanned exploration of space to where most agree we need to be – boots on the surface of Mars. Everyone also agrees that the safest approach to attack the challenge is in phases. These phases will be used to develop, test and prove new deep space vehicles and develop operations procedures. This approach requires time and patience and that can be frustrating. I’d like nothing more that have the confidence to send humans to land on Mars at the very next opportunity. But given the state-of-the-art of our spaceflight technology and spacecraft systems you’d likely spin up such a program only to have it fail to ever launch because of insurmountable weight, power and safety challenges. Or worse, designing a one-way ticket for our astronauts. So a phased development approach it is – build a little, test a little. With that guideline in place we need to draw the outlines of the picture. And here is where differing opinions split the community in the factions. Getting right to the hard questions – what is the best proving ground to test and learn what we need to learn to be successful at landing people on Mars and returning them safely to Earth? What should the sequence of missions look like? Do we use the moon or an asteroid as an intermediate step? Do we use the moons of Mars? Do we use an orbital-only mission to Mars? NASA has a current plan in place, but I would do it differently.
NASA’s current plan is referred to as the Evolvable Mars Campaign. I like the name, but don’t exactly agree with the details. The EMC calls for the use of an Asteroid Retrieval Mission as a proving ground for new spacecraft and deep space habitats. The latest version of the ARM looks like this: a robotic probe will rendezvous with an asteroid, retrieve a boulder off its surface, and tow it back to a more convenient location near Earth. A crewed spacecraft would then rendezvous with the robotic probe to retrieve and study the asteroid sample. The expectation is that by performing the ARMs that we will develop the new systems and gain much needed experience in longer duration, exo-LEO spaceflight, rendezvous and EVAs. I don’t argue that those benefits would come from this plan, but I question if these are the right priorities. Are the goals of ARM truly the most important priorities to be spending our limited resources on? Will the payoff from ARM really prepare us for landing people on Mars and returning them safely to Earth? My opinion is that they aren’t and it won’t.
We need to focus our resources where we are weakest. In broad terms, in my opinion, these areas are: alien Surface landing and takeoff, long duration alien surface operations, and Exo-LEO spaceflight operations. I’m using ‘alien’ to refer to planetary bodies other than Earth because there are options. I would propose that we design the next generation spacecraft and lander for missions to Mars, but test with missions to the Moon. Many people in the industry share the opinion that a return to the moon should come before going to Mars. The distinction I am making here is that I’m recommending a MARS program that uses the moon as part of a test and verification program. The effort will need to be dedicated and focused. We could easily get off track and end up with a Moon program followed, much later, by a Mars program. We need to avoid that trap.
A manned mission to Mars is dangerous. There are many ways in which a crew could get killed or stranded in such an endeavor. Doubtless, engineers will try to design out as many of those paths as possible but it will be challenging. Power, mass, volume, schedule and cost will all vie for kingship over these good intensions. The result will be that some risks will need to be accepted. The environmental Control and Life Support system is a poster child for these trades. These systems need to reliable with certain degree of redundancy to ensure the survival of the crew even after several failures. These systems are constantly in dynamic motion. Pumps are running continuously. Valves are opening and closing many times a day. Fans are running continuously. They also are hit with dirty and/or corrosive liquids that cause clogs or wear and tear on machinery. Experience in the ISS program has taught us a lot about what these systems need to look like going forward but those systems need to be rigorously tested. Of course ECLSS is not alone. Propulsion systems and power systems experience a lot of stress as well. You certainly can’t carry a fully redundant propulsion system can you? It wouldn’t be practical to carry 2 or 3 times the solar arrays that you might need either. Computer failures on the ISS have also taught us a few lessons in redundancy. Just because you have three of the same computer doesn’t necessary mean you are safe from a single, common cause failure from bringing them all down. And when these systems fail nine months from home, or worse, on the surface of Mars, calling the problem home to Houston won’t do you a lot of good. You’re on your own.
The moon provides a decent analog for Mars. Mars’ atmosphere is so thin that surface operations will treat it pretty much like a vacuum except for siphoning off some CO2 to make rocket fuel. On the moon we can test landing and take-off systems that we can’t test anywhere else. On the surface of the moon we can perform repeated sorties on foot to exercise the EVA systems and the ECLSS systems to see if they can’t stand the heavy use on Mars. These are missions that would take place not over a few days as during Apollo, but over the course of weeks as they would on Mars. Mitigation efforts to reduce introduction of dust into the habitable space can’t be tested anywhere else and these systems need to work well the first time they are put on Mars. Halfway through a 300 day stay on Mars is not the time to find out that your hatches, valves, and pumps are seizing up due to contamination from dust.
The challenge in this program will be to limit what has to be designed to accommodate the differences is the Moon versus Mars. There will be some systems that will have to be variant from the Mars design because of the difference in gravity, thermal environment, non-existent atmosphere, solar environment, etc. I believe these can be accommodated but the process will need to be judicious about them because, as I mentioned, you do not want this turning into a MOON program. One of the primary hurdles will be the different mission profile that for the Mars would involve the pre-staging of a return vehicle with in-SITU manufactured fuel. Since the Moon does not provide the CO2 for that process the ascent vehicle will need to land with fuel enough to take off again which may impact its structural design. From the onset of the program a detailed study should be done to understand drivers, like the return vehicle, and what would be impacted with different design driving requirements to enable Moon-first operations. If the moon capability drives the design of a system or part then a trade study will need to determine if a redesign is required for going to Mars or keep it as is, even it is overdesigned for Mars.
Finally, I would incorporate an orbit-only mission to Mars in the timeline. In keeping with our goal such a mission could be the ultimate shakedown for the spacecraft, the crew and mission control. We’ll also be able to test our ability to put a ship that large in orbit about Mars and to depart for Earth again. This mission cannot be taken lightly. The crew on this mission will be in space for a very long time. Imagine also the emotional impact of traveling that far only to stay in orbit around the red planet and not land on it. It took me some time to warm up to the idea of this mission, but it may in fact be critical to the program. The mission would first be ‘simulated’ by a trip to the moon and long orbit stay in lunar orbit before returning to Earth. Then, just at time when Lunar landings are being planned to test the surface systems, a crew will take the proven spacecraft to Mars and back. The next trip to Mars would then include the lunar tested landing and launch systems as well as a tested habitat design. This approach is a logical progression of built-a-little, test-a-little as well as the good practice of fly-as-you-test, test-as-you-fly mentality that has proven successful in many programs.
The path to Mars is a challenging one, but it can be done. We need to put the right plan in place to develop the capability. The priorities in the EMC are misaligned with our key weaknesses. Our priorities need to be focused on something we haven’t tried to do in over 40 years – land, work, and take-off again from an alien planetary body. The very nature of a Mars mission demands that we test and prove those systems before we subject people to too much risk. It’s time we put this detailed plan on paper – all of it. Only then can requirements be derived so that real assessments and designs can be traded and discussed. Only then can we truly say we are on our way to putting boots on Mars.