Rocketdoc Notes – Week of August 30, 2020
Comparison of Moon versus Mars Development Programs
If there was ever an in-house space argument its, should we go back to the moon or forget the moon and go on the Mars? The NASA, plus Bob Zubrin and the Mars Society, want to forget the moon (been there, done that), and go onto Mars. But, some of us old timers who have spent years running trajectories and designing landers for both the moon and Mars under contract have some observations nobody asked for. First, Mars presents some real issues that may not have been truly appreciated. Travel time to the moon is three to five days. For Mars we will assume Conjunction-Class missions which have quick transit times, 180 to 230 days depending on the year, and low Delta-Vs. These advantages are balanced by the long stay times on Mars to wait for the launch window back to Earth to open (~ 440 days). I’m going to assume that we’re going to Mars for colonization, so we want a reusable system for cost reasons, and we need to return it to Earth orbit for reuse. The issue with Mars is that once you depart Earth orbit you are gone for 2.2 to 2.5 years and if something goes wrong there is literally no chance of rescue or resupply. You are on your own!
Bob Zubrin, an old friend by the way, gets around this problem by sending everything the astronauts will need to survive and return home ahead of time via robotic launches during the previous launch window. The astronauts then return home using the previous landed equipment and their equipment becomes the survival gear for the next batch of astronauts. This works, but multiple failures caused by previously unknown conditions could cause serious problems during a 440 day stay. This is why me, and others, think that we should use the moon as our long-term testbed for Mars, and workout the bugs in the equipment before we embark on a 2.5-year journey. If anything, the Moon has a vacuum harder than Mars, its dust is more abrasive, and the temperature extremes are greater. If the equipment survives 440 days in the Lunar environment, we are ready for Mars. Plus, if problems show up rescue is only 3.5 days away!
The counter argument is that because the Moon is a harsher environment, we could easily get bogged down developing the Lunar resources and not have enough money left to go on the Mars. My counter would be that if we get bogged down operating on the Moon, we were not ready for Mars anyway!
I taught classes to seniors in the Aeronautics and Astronautics Department at the University of Washington where we looked at how to develop the Moon (2012) and Mars (2014). Because we have visited the Moon and returned 900 kg of samples, we have a pretty good idea how to develop its resources. For Mars we are largely clueless, which is why the current rover sample-return mission is vital. I think Mr. Musk is very premature in planning colonization flights to Mars without any in-depth knowledge on availability of its resources or even its geology.
How would I go about colonization of Mars? Easy, I would depend on a fleet of teleoperated industrial Mars Rovers and launch them to Mars along with a team of astronauts to dig in at Phobos, the innermost moon of Mars. Phobos is tidal-locked and just under 6000 km above Mars so a base facing Mars would be protected from both Galactic and solar radiation. With a handful of Communication satellites at the same altitude the astronauts could remote-control the rovers in real time and speed up the data return on investment by orders of magnitude. Now we could drill for liquid water (Water is frozen down to a depth of about one kilometer over most of Mars) and examine the samples for Mars-based life. This way we could solve for once and all if Mars had life before it froze over and do it before we brought humans to the surface. We could also pursue mining with large excavation-type rovers. Both types of rovers are dual-purpose in that after a successful exploration for resources we will use them to build habitats, greenhouses and transportation resources. These teleoperated heavy-duty rovers would be based on machinery previously developed for Lunar mining. This is all discussed in detail in Chapter 8 of my book.
What are the advantages of my approach? The principal advantages are cost and risk. If done properly the 2nd Lunar Exploration would pay for itself and even provide enough profit to fund the Mars exploration. There is a concentration of vital mineral resources on the Moon’s near side and these can be delivered to Earth for costs less than the same mined ores on Earth. See Chapter 8 for the details. If our tele-operated mining rovers can successfully operate on Lunar surface for a year or two, then very minor changes will allow them to operate on Mars with very little additional expense or risk. Not landing astronauts on Mars eliminates a ton of cost (remember I designed Mars Landers for NASA for a living), and the Phobos base is essentially built with updated components of the ISS with little additional cost or risk.
If the tele-operated Lunar development works, we have everything we need for permanent lunar bases and have proven the technologies to move on to Mars. If the teleoperated Mars exploration works and proves the resources required for colonization, then we build Mars infrastructure using the same equipment and start building the reusable Mars space transportation systems. If the resources found are not adequate, or too difficult to develop, then we go to Plan B and move on to asteroid mining. Meanwhile, we haven’t wasted a lot of capital on dead-end projects and have made serious progress on moving humanity onto space.