Why do people think the Moon is a safer choice than Mars?

[Albert VDS]

The most common response(besides we need to spend the money here on Earth) to a Mars mission is something like "We should go back to the Moon because it safer".

But is it really safer? Let's explore how much safer a Moon mission is compared to a Mars mission.

Travel time might be the number 1 response, it's only takes 3 days to get to the Moon.

So that's the travel time, but how much time do you need to get a rocket on the pad to safe a Lunar crew in serious trouble?

Because it's not like they'll have a rocket on the pad containing the exact equipment for the emergency at hand.

Assuming you have all the hardware for the following mission and you only need to stack it, fill it up and launch it, how much time would that take?

I couldn't find info on how long it takes to put together a rocket other than this video from ESA assembly their Soyuz:

In that video it took them 6 days, maybe experienced crew could do it in half that time? Maybe even 2 days?

That's 5 days to send your rescue mission and that's not considering mission planning and other pre-launch requirements.

But let's go with 5 days.

In which scenarios can a crew be saved after 5 days?

Of course the Moon has the advantage of a free return trajectory but there are suggested Mars missions which have either a free return trajectory or a backup ERV.

Apollo 13 is a good example of why a backup like that is important.

Zero G is also a big problem. A 6 days trip to and from the Moon in total compared to 360 days for Mars. Of course you could stop bone and muscle loss by having a rotating spacecraft,

but it hasn't been tested in the real world(or space). Radiation would be manageable according to this article: http://www.space.com/23875-mars-radiation-life-manned-mission.html

Both could be using soil on their bases to add more shielding, a Moon base needing much more soil though.

So the Moon has it's proximity to Earth going for it. So what does Mars have?

It's atmosphere, it can stop micro meteorites, reduce the radiation and it has CO2 ready to be plucked from it.

It can also help slowing down with entry and descent.

It has water in it's soil, which can be used to make oxygen and hydrogen and the CO2 can be made into methane.

The Moon has areas with water ice, but nowhere near as much as Mars and it's mostly in dark places.

Not an ideal place if you want to use solar panels or want to use the Sun to illuminate the area.

Mars also has a 24h 40m day, instead of 29.5 days.

It's gravity, it's still only 1/3rd of Earth's gravity. Again we don't know what the real world implications, but that's still better than 1/6th which the Moon has.

To conclude; this is not a which is a better destination. They both are for different reasons.

[vger]

It's not just a matter of safety. It's just a logical step.

We're completely "out of practice" in the "visiting other worlds" hobby, and our technology has changed a LOT since the Apollo days.

Unfortunately, a little bit of "reinventing the wheel," and short-term tests of our new concepts should be attempted before we try making the jump to Mars. In fact, even if someone showed up with a viable and affordable plan for a manned Mars mission, I STILL wouldn't want to risk sending astronauts way out there until we played with the moon again first. A lot can go wrong in a year on a space ship that's out in the middle of nowhere.

Since we need to test the viability of long-term voyages anyway, we might as well take advantage of the moon while we're at it, and do some of the things we never got around to before.

Polar landing, anyone?

Edited March 6, 2015 by vger

[Scotius]

Well, for one: ship transporting 10 people to the Moon can be much smaller (cheaper) than a ship required to transport the same 10 people to Mars. Life support system required for Mars mission will have to be much more robust and capable than lunar one. Additional supplies can be delivered to lunar base every few days. To Mars base such transport can arrive twice per year at best. If there will be medical emergency martian crew will be beyond any physical help from Earth, while sick or injured astronaut on the Moon can be evacuated back home - or, if his condition is too serious a doctor can be sent from Earth relatively quickly.

That's from the top of my head.

[Superfluous J]

Apollo 13 would have been a very different story if they were heading to Mars.

[Bill Phil]

Um... There are areas on the Moon that are in permanent sunlight. The Peaks if Everlasting Light or something.

Plus, you can see the Earth. Great view, and you don't quite feel alone.

[Dkmdlb]

In which scenarios can a crew be saved after 5 days?

The scenario in which you give the moon base enough independent emergency life support equipment and systems to last enough time to deliver a rescue payload to the surface. Which is something you would do. Because it's obvious.

[Nibb31]

So that's the travel time, but how much time do you need to get a rocket on the pad to safe a Lunar crew in serious trouble?

Because it's not like they'll have a rocket on the pad containing the exact equipment for the emergency at hand.

Of course not, but if for some reason you have to evacuate your outpost due to some technical mishap or if a crew member develops a medical condition, you're only 3 days away from safety.

And if some critical spare needs being sent, it can come up on the next logistics or crew rotation flight in a month or two, instead of having to wait 2 years for the next launch windows to Mars.

You also don't put yourself into an "ISRU or die" situation. You can develop and test your closed loop life support systems in an actual space environment while still having regular logistics deliveries as a backup. You can develop dust mitigation techniques, radiation shielding, study biology in partial gravity. If anything goes wrong, you can easily evacuate and return to safety.

Going to the Moon is all about learning how to live on the surface of another world, developing the techniques to survive and learning from mistakes in a more forgiving environment. We have very little experience with this stuff, it's just too big a risk to put human lives on a line that we don't even know how to draw.

Edited March 6, 2015 by Nibb31

[PB666]

The most common response(besides we need to spend the money here on Earth) to a Mars mission is something like "We should go back to the Moon because it safer".

But is it really safer? Let's explore how much safer a Moon mission is compared to a Mars mission.

Travel time might be the number 1 response, it's only takes 3 days to get to the Moon.

So that's the travel time, but how much time do you need to get a rocket on the pad to safe a Lunar crew in serious trouble?

Because it's not like they'll have a rocket on the pad containing the exact equipment for the emergency at hand.

Assuming you have all the hardware for the following mission and you only need to stack it, fill it up and launch it, how much time would that take?

I couldn't find info on how long it takes to put together a rocket other than this video from ESA assembly their Soyuz:

In that video it took them 6 days, maybe experienced crew could do it in half that time? Maybe even 2 days?

That's 5 days to send your rescue mission and that's not considering mission planning and other pre-launch requirements.

But let's go with 5 days.

This is a red herring argument. With the moon we have proven technology to get people off, with mars Nope, not by a long shot. The hope I see would be a VASIMIR that over several years transports a lander and drops it close to a station, with a station in Mars SOI then the lander to hop its way back to Earths SOI. In an emergency, Mars is a suicide trap.

In which scenarios can a crew be saved after 5 days?

Of course the Moon has the advantage of a free return trajectory but there are suggested Mars missions which have either a free return trajectory or a backup ERV.

Apollo 13 is a good example of why a backup like that is important.

Zero G is also a big problem. A 6 days trip to and from the Moon in total compared to 360 days for Mars. Of course you could stop bone and muscle loss by having a rotating spacecraft,

but it hasn't been tested in the real world(or space). Radiation would be manageable according to this article: http://www.space.com/23875-mars-radiation-life-manned-mission.html

Both could be using soil on their bases to add more shielding, a Moon base needing much more soil though.

So the Moon has it's proximity to Earth going for it. So what does Mars have?

It's atmosphere, it can stop micro meteorites, reduce the radiation and it has CO2 ready to be plucked from it.

It can also help slowing down with entry and descent.

It has water in it's soil, which can be used to make oxygen and hydrogen and the CO2 can be made into methane.

The Moon has areas with water ice, but nowhere near as much as Mars and it's mostly in dark places.

Not an ideal place if you want to use solar panels or want to use the Sun to illuminate the area.

Mars also has a 24h 40m day, instead of 29.5 days.

It's gravity, it's still only 1/3rd of Earth's gravity. Again we don't know what the real world implications, but that's still better than 1/6th which the Moon has.

To conclude; this is not a which is a better destination. They both are for different reasons.

1. Any mission to the moon begins with returnable lander on the moon. This is not there to rescue 100 people, its there to take folks back who have a medical need that cannot be treated on the moon.

2. dV. THe moon is a few hundred dV, mars is a few 1000 to land. Getting a lander back in space and back to earth is a challenge. This challenge to a mars landing can be circumvented if Phobos is selected instead of mars. Mars may slow down reentry (not much for the really heavy people movers) but it has alot more dV to stop, more with aerobraking than the moon has without, but the big killer is getting off. On the moon we can do a suicide burn with accuracy, on Mars you going to have to burn above the target and then reburn to land.

3. CO2 without water does not make mars a better choice than the Moon. You can, with difficulty make O2 from CO2, its simply easier to make O2 from water, and you get hydrogen, which can react with CO2 at high temperature. Even if you use plants to make O2, the reaction requires water. Just because Mars has an atmosphere does not make it a better choice. Unless you have a probe that has discovered liquid or frozen water on mars at a high enough density, making fuel for return trip is nearly impossible. The water that is in the martian soil would be depleted quickly for any productive effort without a full fledged surface manipulation technology designed for that application.

4. Establishing a base on Mars moons first makes alot more sense, it is essentially a grounded space station.

5. Time, time is essentially. I am scientist, my objective is collect science, not spend 18 months in flight time doing nothing for a 20 day mission. I would suspect that the type of science done on moon now would be of a probative or astro-observational, the second has a 15 day cycle no need to keep scientist there full time.

6. Micrometeors - dig down on moon, kill 2 birds with one stone, radiation and micrometeors. Or transport a moon dozer and doze moon sand on top of a grounded station. Need to get Dozer to mars through the atomsphere but we see from our studies, Mars does not have enough hv to run serious equipment off of solar. The moon has 15 days of 1.3 kw/m²

7. Both Moon and Mars have O and H trapped in their rocks, it a matter of finding an efficient way of getting it out. If you dug a hole deep enough into the moon you could create an atmosphere that would easily be trapped by a trapdoor or lasers.

Drawbacks of the Moon, it solar cycle is 30 days, which mean that solar needs either a massive lithium Ion battery or nuclear assists

8. Technological proving ground-Most important. Its not about CO2 or O2, this is overemphasized, its about surface manipulation. The tools you apply on the moon will fail, but new technologies can be brought in a cycle of a few weeks, and structural failures can be returned to earth within a few days for analysis. You bring a tool to mars it breaks, you make a new one on Mars it breaks again, finally you can't make any tools. It breaks on the moon, send it back on a space teather to a space station, see if the can figure out why it broke, if not place it on a small scale re-entry vehicle and send it back to earth for analysis.

9. Productivity, once again tether the space station to an orbit between the earth and the moon and if you can manipulate the moon surface it can be potentially be used to create new objects in space.

[Bill Phil]

Not only is the Moon closer, but it's easier to get on and off of. It's not very massive compared to Mars or, well, anything.

[vger]

Drawbacks of the Moon, it solar cycle is 30 days, which mean that solar needs either a massive lithium Ion battery or nuclear assists

Actually, we probably have a spot on the moon that almost ALWAYS gets sun. And conveniently right near suspected water sources.

http://www.space.com/957-perfect-spot-moon-base.html

Edited March 6, 2015 by vger

[tater]

PB666 pretty much nailed the answer to this.

I'd add that while the dv budget for Phobos/Deimos is comparable to the lunar surface, the travel time is certainly a big deal, and without a rotating station/spacecraft, even the moon might prove to be a medical issue over long time frames, so the near 0-g of the 2 martian moons would possibly be a medical issue.

I recall reading a paper (a couple decades ago) about using Phobos/Deimos as places to mine propellants instead of the moon because the dv budget is similar, but it's far easier to leave the ,martian moons once tanked up.

[dryer_lint]

Because you could return from a Moon trip.

[Aghanim]

Moon: We have a problem! Go to the escape rocket now!

Mars: We have a problem! But we cannot use the escape rocket because its not the transfer window time

[EzinX]

You can obviously have prebuilt rockets that only need their payloads loaded ready to launch rescue missions for a Moon colony.

You're going to have to build a lot more rockets either way, which would mean that you'd have a big line of rockets in various stages of assembly at several factories around the world. It would be a lot easier to find a rocket to launch an unscheduled payload if the world production of rockets were 10 times higher.

Also, Moon has actual economic value. We can envision some day building massive self replicating robot plants on the Moon that spread out to cover the entire surface. Any products produced by these plants could be easily put into lunar orbit or even earth orbits. It is _much_ easier to reach orbit from the Moon : a pure vacuum, so electromagnetic accelerators should work perfectly. Or you can build a lunar elevator using kevlar as the elevator cable.

With full or partial self replicating machinery, the Moon represents a source of limitless raw materials with no human beings to get in the way or whine about environmental damage. You could power your electric grid with barely shielded fission reactors and dump toxic waste wherever you like. Since the Moon is a big blob of materials that is thought to have come originally from the Earth, all the elements should be there with similar prevalence.

[vger]

You're going to have to build a lot more rockets either way, which would mean that you'd have a big line of rockets in various stages of assembly at several factories around the world. It would be a lot easier to find a rocket to launch an unscheduled payload if the world production of rockets were 10 times higher.

Also, Moon has actual economic value. We can envision some day building massive self replicating robot plants on the Moon that spread out to cover the entire surface. Any products produced by these plants could be easily put into lunar orbit or even earth orbits. It is _much_ easier to reach orbit from the Moon : a pure vacuum, so electromagnetic accelerators should work perfectly. Or you can build a lunar elevator using kevlar as the elevator cable.

Putting these two paragraphs together and coming at a fun conclusion, if we can find the necessary materials, it just makes more sense to run a space program from the Moon. The dV is so much less than Earth, and the gravity has less of an impact on structural integrity. If you wanted to launch a huge rocket bound for a distant planet, launching it from the moon would be more practical.

[PB666]

You can obviously have prebuilt rockets that only need their payloads loaded ready to launch rescue missions for a Moon colony.

You're going to have to build a lot more rockets either way, which would mean that you'd have a big line of rockets in various stages of assembly at several factories around the world. It would be a lot easier to find a rocket to launch an unscheduled payload if the world production of rockets were 10 times higher.

Also, Moon has actual economic value. We can envision some day building massive self replicating robot plants on the Moon that spread out to cover the entire surface. Any products produced by these plants could be easily put into lunar orbit or even earth orbits. It is _much_ easier to reach orbit from the Moon : a pure vacuum, so electromagnetic accelerators should work perfectly. Or you can build a lunar elevator using kevlar as the elevator cable.

With full or partial self replicating machinery, the Moon represents a source of limitless raw materials with no human beings to get in the way or whine about environmental damage. You could power your electric grid with barely shielded fission reactors and dump toxic waste wherever you like. Since the Moon is a big blob of materials that is thought to have come originally from the Earth, all the elements should be there with similar prevalence.

I could imagine building a trackway on the moon that accelerates objects to lunar orbit - circularization energy via mass accelerator.

[PakledHostage]

PB666 pretty much nailed the answer to this.

Except for the delta-V part... It takes far more than a couple hundred m/s delta-V to land on the moon. Real life isn't KSP. The Apollo LEMs had almost 5000 m/s. 2220 m/s for the ascent stage and 2470 m/s for the descent stage. (Ref: http://www.braeunig.us/space/specs/lm.htm)

[PB666]

Yeah but the problem is getting hydrogen from those rocks. Every fuel that we have is a redox reaction of some sort. You can use aluminum such as in the shuttles SFRBs but really you need to crack hydrogen off of something. If you could turn the entire moon into a solar hydrogen scavenger (still terribly slow) you might be able to combine hydrogen with aluminum and other light metals harvested on the moon to create a reactant.

- - - Updated - - -

Except for the delta-V part... It takes far more than a couple hundred m/s delta-V to land on the moon. Real life isn't KSP. The Apollo LEMs had almost 5000 m/s. 2220 m/s for the ascent stage and 2470 m/s for the descent stage. (Ref: http://www.braeunig.us/space/specs/lm.htm)

How much did the chinese use on their most recent descent unmanned mission?

[vger]

I could imagine building a trackway on the moon that accelerates objects to lunar orbit - circularization energy via mass accelerator.

Huh, I wonder how tall a structure we could put there, with engineering and materials we have today.

[EzinX]

I figure you'd use a hybrid system. A mass accelerator would fling the payload into a ballistic arc. Then, as it hurtles above the lunar surface (in a nice clear vacuum with no atmosphere to get in the way), you precisely focus a large laser focusing mirror on the back of the payload capsule and vaporize some of the material. The laser impingement would lase off vapor at very high velocity, giving you just enough of a push to make it to an elliptical orbit.

After that, you'd probably use some kind of electric space tug to move these capsules around to their ultimate fates.

[WestAir]

I just came to leave one specific comment to the OP,

"It's not like we have a rocket on the pad with emergency equipment ready."

In a perfect world (Like in our scenario), we would delay the launch of a moon mission until we had appropriate contingencies available, up to and including a ready second rocket. It's not insane to ask we scrub the launch for 6 months while we prep a ready spare. That's in a perfect world, though, and it's only applicable to a Lunar mission - not a Mars one.

[dryer_lint]

Moon: We have a problem! Go to the escape rocket now!

Mars: We have a problem! But we cannot use the escape rocket because its not the transfer window time

This.

And besides, it just feels logical to colonize the moon first. I mean, it's right there, less than a week away. Think like a KSP player. Why go for an interplanetary trip when the Moon is right there?

[Pixel of Life]

Huh, I wonder how tall a structure we could put there, with engineering and materials we have today.

I think at least 5 times as high as the Burj Khalifa (830 meters tall), since the Moon's gravity is roughly 0.17g. Probably more since you can just leave wind out of the equation. Somebody correct me if I'm wrong.

In theory, wouldn't it be possible to build a space elevator from the Moon's surface, through Lagrange point L1 and all the way to Earth GSO? Such a structure would be nearly 350 thousand kilometers tall. I know this is what Liftport is trying to do, but their elevator only extends from the surface to L1.

Edited March 7, 2015 by CaptainKorhonen

[Newt]

Another difficulty is communications. Earth bound technicians and engineers can conduct conversations with people on the Moon, with a slightly awkward but easily managed delay. If the People on the Moon have an issue, Earth can know in a second, and immediately start helping to troubleshoot. When the Mars base has a problem, Earth knows in a few minutes at best, and can only start to help troubleshooting after the astronauts should have made some response on their own. Astronauts are well trained people, and they will not do something damaging just because they do not get that help, but having additional guidance and feedback from fellow astronauts, the people who built and designed your vehicle, and the people who operate and monitor it on Earth, would help a lot.

Building bases on the Moon would be helpful so that when the 'training wheels' of rapid communications are let off, we will already know better how to deal with astronauts on a ground base, and with fixing problems that can arise there.

[Kibble]

Travel time might be the number 1 response, it's only takes 3 days to get to the Moon.

So that's the travel time, but how much time do you need to get a rocket on the pad to safe a Lunar crew in serious trouble?

In the event of a failure of the habitat, or if an astronaut requires medical attention, you can swiftly and easily abort back to Earth. At Mars if an astronaut requires urgent medical attention they will most likely die, and if the habitat fails when its not a TEI launch window, then they will all die when the resources for the return trip are exhausted. Id est the Moon return vehicle quickly brings the astronauts home, such that life support is only required for a few days, rather than many months.

In which scenarios can a crew be saved after 5 days?

If the lander ascent stage doesn't work. If the ascent stage does work, you can just abort back to the Earth.

It's atmosphere, it can stop micro meteorites, reduce the radiation

Earth's atmosphere is not the thing that blocks all that solar radiation, its the magnetic field, which Mars doesn't have. Plus the atmosphere of Mars is less than 1% as dense as ours.

It has water in it's soil, which can be used to make oxygen and hydrogen and the CO2 can be made into methane.

The Moon has areas with water ice, but nowhere near as much as Mars and it's mostly in dark places.

Not an ideal place if you want to use solar panels or want to use the Sun to illuminate the area.

Water isn't the only valuable resource out there. Even if excavating water and Moon poles turns out a little too hard for vaguely near-term operations, the dirt on both Mars and Moon is made mostly of aluminium oxide, which can be split for oxygen, and burned with the aluminium as rocket fuel. If you really want volatiles like water, the best place to look is the Minor Planets.

Mars also has a 24h 40m day, instead of 29.5 days.

We've proven space hardware can survive Lunar nights.

It's gravity, it's still only 1/3rd of Earth's gravity. Again we don't know what the real world implications, but that's still better than 1/6th which the Moon has.

It would suck to go all the way to Mars just to find out the gravity isn't enough, and the astronauts return years later with major health problems. OTOH Kirk Sorenson's wonderfully effective, brilliant xGRF concept both makes rotating piloted orbital facilities viable, and makes testing the human body's response at different levels of acceleration easy. If one sixth of a gravity is enough, that would be the best news for human spaceflight since Buzz Aldrin proved manual labour in micro-gee environments is possible.

Edited March 7, 2015 by Kibble