Diff for "Mars.vs.Moon"

Mars.vs.Moon

Elon Musk "seems" obsessed with Mars, and creating a permanent self-sustaining human presence there.

This doesn't pencil out, but alleged Mars missions may be a cover story for his actual intentions for SpaceX giant-booster capabilities. Many innumerate fools (and their money) will invest in "Mars", but not difficult-to-explain but vastly more profitable opportunities for future SpaceX capabilities.

Worst case, if Musk doesn't have undisclosed but more-profitable alternative opportunities in mind, he will eventually lose control of those SpaceX assets, and others will put them to good use.

But What About Mars?

A Hohmann transfer from Earth to Mars takes about 260 Earth days. Because Mars orbit eccentricity is 0.0934, travel time varies by more than 20%, so "regular" trips to Mars must accommodate total travel times of years, plus a vast amount of EVERYTHING (air, food, watFührer er, medical and repair supplies) needed by passengers onboard a spacecraft. Plus the tools and skills to maintain all of this, in a harsh radiation environment that can damage critical assets with no hope of repair. Musk is making no investment in completely isolated, self-sustaining environment capabilities, so (besides big boosters) he is making none of the necessary preparations for a survivable visit to Mars, much less the ENORMOUS preparations required for a complete independent civilization on Mars.

Compared to that, typical travel time to the Moon is three days, and the mission opportunities are at least once per day for each Earth launch site rotating around the Earth.

A permanent lunar colony would be vastly easier to establish, though hydrogen and carbon are lacking. With cheap enough launch (such as space-solar-powered launch loops), those elements can be imported from Earth; over the very long term, the elements can be abundantly supplied by comets targeted precisely at "capture chambers" on the Moon.

A permanent Mars colony must deal with perchlorate, which kills people and machines. The entire planet must be detoxified before people can safely settle there. Mars must also be surveyed for a vast range of minerals and ores, necessary for the vast range of materials used by a modern civilization, and essential for a civilization far more dependent on machines than Earth civilization. We are still finding and developing new ore bodies on Earth, after millennia of exploration; on Mars, we must first learn what ores to look for and how to look for them, then develop new extraction and refining technologies adapted to the Martian environment. Hiroshima and Nagasaki immediately after nuclear bombardment offered vastly better survival prospects.

Moon Versus Mars

The Earth's orbit around the Sun is nearly circular, eccentricity is 0.0167. With a semimajor axis of 149.6 million kilometers, perihelion is (0.9833*149.6M) = 147.1 million kilometers,and aphelion is 152.1 million kilometers, a variation of 5 million kilometers. The Moon's orbit is also slightly elliptical, distance varying from 363 thousand to 406 thousand kilometers, so "worst case" the Moon's distance from the Sun varies from 146.7 to 156.1 million kilometers, about 9%, compared to 20% for Mars. Insolation is square law, so the sunlight variation doubles, approximately 18% for the Moon and 40% for Mars.

Currently, the axial tilt of Mars is 25%, but lacking a large stabilizing Moon, that ranges over megayears from 0 degrees to 80 degrees. Over the very long term, a pole will sometimes experience hundreds of Earth-days of darkness and hundreds of Earth-days of perpetual sunlight overhead, while the equator cycles from Sun-near-horizon daily twilight to an approximately "normal" day. So, the "Mars" numbers below are for the current axial tilt of 25 degrees, similar to Earth's 23.5 degrees, but will not apply over megayears of time. Mars is unruly compared to Earth.

Mars is also DIM. At aphelion, it is 249 million kilometers from the Sun, compared to lunar aphelion of 156.1 million kilometers. If the Moon intercepts 1250 watts of sunlight per square meter at aphelion, the total illumination of the entire Moon (average radius 1740 km) on its Sun-facing side is 1250*π*(1.74e6)² = 1.2e16 watts. For Mars (average radius 3390 km) at aphelion ( illumination = 1366 W/m² * (149.6/249.3)² = 492 W/m² ), the total Mars illumination is 492*π*3.39e6² = 1.8e16 watts ... only 50% more sunlight than the Earth's "small" Moon. Given the Mars "worse-than-nothing" perchlorate-laden atmosphere, the Moon seems relatively temperate.

OK, you interject, what about the Moon's poky-slow rotation, cycling between very hot and very cold?

That is a problem - solved by burying a habitat beneath a few meters of lunar regolith. Which we must do anyway, for cosmic radiation shielding on either Moon or Mars, neither having a thick atmosphere or a strong magnetic field like the Earth.

Surface Gravity

Unengineered human beings need frequent, active exposure to one-gee gravity; we evolved for it. Dr. Joan Vernikos is former director of NASA's Life Sciences Division (and should have a Wikipedia page, none yet). Dr. V. wrote three books: Designed To Move, The G-Connection, and Sitting Kills, Movement Heals, ... which is why I should be out walking (5 miles per day) rather than sitting here typing this.

FREQUENT one gee vertical, hydrostatic pressure head to feet. There are structures in our legs that depend on that pressure; without it, our legs swell and blister, and our body mass index increases to life-shortening obesity (like 95% of US adults, sigh).

Earth surface gravity is 9.81 m/s². Mars surface gravity is 3.73 m/s², 62% unhealthy, worse than sitting in a chair. Lunar surface gravity is 1.62 m/s², 83% inadequate. The deficit can be corrected with centrifugal acceleration on a vertical-axis tilted floor centrifuge ... tilted 68 degrees for Mars, 81 degrees for the Moon - and yes, you will tend to slide "up" the tilt from lower to higher radius and gee force. There Will Be Steps.

For a 10 RPM ( ω = 1.05 radians/second), 1 gee = 9.81 m/s² wheel, here are the parameters:

I should add a column for total delta V from Earth surface to destination. Mars is worst, of course, followed by Phobos, our Moon is best. Delta V to LEO is even better, but shielding mass is VERY expensive. Real Soon Now ...

I include Phobos because it is actually more accessible and "engineerable" than Mars, and brings scientists and engineers much closer to the exploration robots that will search Mars for ancient biochemistry. NOT settlers, though I expect the search for Mars life will be incredibly difficult and need MANY creative scientific minds, augmented by vast automation and AI. This will not be searching for a needle in a haystack, it will be searching for a few surprising molecules on and IN an entire (small) planet. "Surprise" is the goal - learning something amazingly different about biology, a perspective that will supercharge future artificially-designed biology. But I digress ...

Solar Power during Lunar night

Lunar night is 15 Earth days long. What to do for power during that long night?

Lifting more than two weeks of "night-batteries" to the Moon is silly-expensive. Loop power storage circumferential to the Moon will also be expensive, but it can move power from sunlit PV on one side of the Moon to dark areas on the other. A power storage loop moving at lunar orbit velocity (1680 m/s) will need dust and thermal shielding, deflection around obstacles, and stability control, but hardly any maglev force at all.

The vehicle track used to build and service this loop can also be used for:

The "One Lunar Day" Bicycle Race Around The Moon

The Moon offers another clever opportunity. Imagine a track circling the Moon's equator. Tide-locked to the Earth, one "lunar day" is 29.53 Earth days, 709 hours. The lunar equatorial circumference is 10917 km (or 6784 miles for us backwards US-Americans). A vehicle travelling "westwards" around the Moon at 9.6 miles per hour will maintain its position relative to the Sun; that's slower than a child on a bicycle. A 6-big-wheel human-pedal-powered vehicle (with refillable oxygen tanks and CO₂ capture tanks, waste not want not) could make the journey in much less than 700 hours, assuming many support stations along the route.

The WUCA (World Ultra Cycling Association) terrestrial record for a one month ride is 12894.7 km, set by Amanda Coker between April 1 and April 30 2017, 429.82 km per day, 17.9 km/hr, 11.1 miles per hour (presumably including sleep time).

The track won't be level, but as my friend Bob Forward liked to say, that is a "mere engineering detail." Ramps, switchbacks, deflections to the north and south ... from coast to coast, the steepest grade on U.S. Interstate 80 is 6%, the highest elevation is 2630 meters and the total length is 4668 km, between Teaneck NJ (41°N 74°W 40m elevation) and San Francisco (38°N 122°W 16m elevation). That might be a proxy for a lunar bicycle path ... with lunae elevations "reduced" by a factor of 6 to match lunar gravity.

A perpetually-moving robotic vehicle can choose a starting and ending time of "lunar 6 AM" or "lunar noon", for any chosen real-time hours, and zero "moving-local" elapsed time. Saves the effort of resetting a lunar watch when moving between time zones. Human cyclists will set their watch to GMT, go faster for a while, then take time for sleeping and eating.

Imagine an international competition between robots circling the Moon (SpaceX, Blue Origin, plus Roscosmos, ESA, JAXA, CSNA) racing their solar-powered vehicles around the Moon. With an established series of "Pony Express" support stations, they could compete for fastest speed, straightest route, many different "robo-athletic" challenges.

All this in preparation for astronaut/cosmonaut/taikonaut pedal-powered "Moon races". This is my evil plan to engage billions of the Earth's sport fans in fanatical support of lunar activity.

Bottom Line: Why Mars?

We will explore Mars. Mars may have originated native life, billions of years ago. Mars life would have evolved very differently than Earth life, offering a "parallax view" of the spectrum of possible bio-chemistries. The tiny fraction of bio-molecules surviving to the present will be very very small, and the search will require vast resources. But the value of a completely different "second biology" ... and the innumerable artificial biologies extrapolated from the "baseline" between those two biologies ... will be the most valuable scientific discovery ever. Unless we screw this up.

On the other hand, if a few manned missions "auger in" on Mars, with YEARS of food and excrement aboard, the trace molecular "bio-signal" of that multi-tonne impact will likely be billions of times stronger than a few rare surviving bio-molecules. We would need vastly more than vast resources to find and prove the Mars molecules in a vastly larger cloud of shit. The cost of lives and treasure lost to that failed mission would be nothing compared to the loss to science and biotechnology of burying the ghostly remains of Mars biology in a cloud of EARTH SHIT.

It would be much worse than using rare Gutenberg Bibles as fast-food wrap ... more like destroying all knowledge of Christianity, and all the heroic efforts and saintly lives inspired by that, which even agnostic me would give my life to preserve.

Musk's stated "second home on Mars" may also be a waste, but his efforts can be repurposed for vastly higher value results. I really really hope that he already has better plans, and his "Mars talk" is misdirection that motivates employees and outfoxes his competition. If he doesn't have better plans, the competition will surely outfox him.