Tuesday, October 8, 2019

Some ideas for small lunar landers

I am a big supporter for the well thought out return to the moon with the goal of establishing a permanent presence.  I am also of the opinion that it is better to start now with what we have than to wait for years for something better.  Meaning, that I’d rather split up a mission to launch on three currently flying rockets than to wait a few years for the superbig rocket in development that could launch it in one go.  Because rocket developments never hit snags.

We are also starting an era of small landers.  Beresheet was a secondary payload on a Falcon 9, and Vikram was just part of the Chandrayaan-2 mission.  While not successful, there are plenty more small landers planned, either to launch as secondary payloads or on small rockets like the Electron.  Hopefully, most of them will be successful. 

So for the past few months I’ve been wondering what missions could be flown with small landers that would help prepare the way for a permanent human presence on the moon.  A big reason I think this would be great is because it is an opportunity for countries with small, or even no, space agencies, private companies, even universities to contribute something to our return to the moon.  Country D may not be able to launch a rocket that could carry their citizens to the moon, but they could finance a lander – maybe launched by Country G’s rocket – that would deliver some useful cargo for a future base. 

These are some of the ideas I’ve had.  Most are for “dumb” cargo.  As long as it is in a container and protected from micrometeorites, it should be able to sit on the lunar surface for years until needed.  Now, I’m not an engineer, so these are just ideas from an armchair spacecraft designer. 


The idea for this is to have three or four, identical, robust small landers that can launch on one rocket.  They would land fifty or so kilometers from the general area you want to start building a base.  Hopefully, one or two of them would land successfully.  They would have cameras to photograph the area so we could pinpoint their location from satellite maps, and they might have some sensors, but that’s not their job.  And after they land, they’d wait.

The big challenge would be surviving the lunar night, although Chang’e 3 – with a radioisotope heater – is still going after almost six years.  Since the majority of lunar landers are from the 1960’s, it’s hard to say if we could build a purely solar powered lander that could survive several lunar nights.  Hopefully, that’s something the currently planned small landers will answer.

Anyway, whenever another mission would be landing, the beacons would turn on.  These wouldn’t replace other landing systems, they would just be an additional way for future landers to know where they are.  There is also the possibility that the beacon’s cameras could record part of the new lander’s landing.  While cool, they could also help determine what happened if there are incidents.

And a new batch of beacons could be launched every year or so – depending on the expected lifespan – with whatever upgrades are needed, filling in coverage gaps or expanding the landing area.

Pure ice

One resource that future astronauts will mine on the moon is water.  This comes from ice that has survived in permanently shadowed craters at the poles.  But it will take time – probably years – to conduct the basic science investigations, figure out how to mine the ice ore, remove all the regolith from it, and the ad nauseam tests to make sure it is completely safe.  All the while the astronauts will need water to drink and to water their plants.  All of this will need to be sent from Earth.  It will be recycled, but you can only recycle so much water so fast.  And to do more stuff on the moon, you’ll need more people there.  To have more people there, you’ll need more water.  Water is rather bulky, which means we’ll want to send as little as necessary.  But, we don’t want to short them on water.  It would be great to have an emergency supply.

These landers would carry maybe fifty kilograms of ice and land in a permanently shadowed crater.  They might have a spotlight to see the surrounding area, but then they’d just turn off and freeze.  They’d sit there until they are needed and collected.  And if there was a landing mishap – depending on how energetic it was – some of the ice could be recovered.  It could be a learning experience separating the regolith out of it.

Spare parts

One issue that’s come up with Martian rovers are their wheels are damaged from driving over rough terrain.  I’m not sure if any of the lunar rovers have lasted long enough to suffer such damage.  But since it is likely that a swarm of rovers will be around any lunar base – building, maintaining, conducting research, etc. – it is likely that some components will wear out or break.  So if we plan ahead and make sure that all the Type D maintenance rovers and Type II science rovers have the same wheel design, we could launch a small lander full of wheels and other spare parts. 

At first I thought maybe the spare part lander could have the robotic arms to do the repairs, but then I figured – if we thought ahead – all the Type Ds and IIs would already have manipulator arms and the lander would just need to have a tool attachment.  A rover could roll up to the spare part lander, grab the right tools, and fix their own wheels.

Cable spools

Broadly speaking, there are four areas to set up a base near the lunar poles.  The first is inside a permanently shadowed crater.  That’s a bad idea because of probable psychological effects on the crew.  The second is on one of these mountain peaks that’s always in sunlight.  That’s bad because it will probably be tough to land on a peak, and you’re not going to want to waste solar panel space for your habitat.  (To establish a lunar power grid – with solar stations around the moon all connected – you either have to launch everything from Earth, or build it from lunar resources.  To build up that level of lunar industry and infrastructure, you’ll need all the power you can get which means putting as many square meters of solar paneling on these peaks as will fit.)  The third place for a base is a relatively flat area not facing Earth.  That’s bad because why would you want to be difficult when placing your first lunar base.  So that leaves the fourth area, a relatively flat area facing Earth, meaning you can stay in constant communication.

But if your base is a hundred kilometers from these sunlight peaks, how do you get the power to the base?  You get a hundred kilometers of power cable and lay it across the lunar landscape.  Do you send up the hundred kilometers in one section, or in one kilometer sections?  A case could be made for either.  For the hundred kilometer option, you’d have the cable without a hundred splices in it.  But the big landers would probably only land at the base, and then you’d have to transport the spool and figure out how to deploy it all.  Smaller landers, on the other hand, could land nearer to where the cable is needed.  If you’re willing to risk possibly losing a one kilometer section, you could even try to land it in a rough location.  And while launching a hundred landers – you may be able to get a few on one rocket – would take time, having multiple sections worked on at the same time might be faster.  If you hit a snag with your hundred kilometer spool, you’re stuck until you figure it out. 

Of course, if we start with a few one kilometer sections and work all the kinks out, you could fly some medium landers (one lander launched on something like a Falcon 9) with ten or twenty kilometer sections, so it’s not an either/or option.  And how long a section we can land depends on several factors.  How much power do we expect to be on this cable?  Do we just use copper, or some other conductor?  How much insulation do we put on the wires?  All these factors – which smarter people than I can figure out – will determine how long a section we could land on small landers.  I’ve just been using a kilometer as a general length.

Originally, my idea was for a power cable combined with a fiber optic cable.  But I don’t think splicing fiber optic cable every few kilometers is a good idea.  But since fiber optic cables are lighter than and not as bulky as power cables, you might get ten kilometers on a small lander, or maybe the whole hundred kilometers on a medium lander and you’d just lay it next to the power cable.

As I said above, landing on a mountain peak is probably tough, so we’d find a levelish area at the base of one of these peaks.  Why not put the base there?  Well, such an area may only get an Earth day or two of sunlight every lunar day, which might be psychologically tough on the crew.  Also, such areas might not be large enough to land the big landers and build out the base.  So you’d land equipment at this base camp, and haul it up the mountain.  This would likely be largely done with robots.  But how do you power them?  Do they have to climb the mountain every time they need to recharge?  Or do you land a one kilometer cable and let them recharge at the base camp?

Besides robots maintaining the landing area – dragging any expendable landers out of the way – you’d also have other robots surveying the route for the power cable.  These could also prepare landing spots, or even act as beacons for the landers.  Now would they have to go all the way back to the base camp to recharge, or would it be better to have recharging stations every kilometer along the way?  Unless there is an area to land the hundred kilometer spool near the power station, you might be landing it at the wrong end. 

Of course, just having a cable laying across the lunar surface wouldn’t be the end of it.  You’d have a robot start at one end, pick the cable up, scoop up some regolith, process it, and 3D print a shell.  This would probably be a few centimeters thick to protect it from micrometeorites.  Speaking of 3D printing, depending on how it is done, it might require some binding agent, which might be something we could land in advance, depending on the shelf life in lunar conditions.

Now, does this first cable need to carry a lot of power?  Given that you’re not going to land on the mountain top and instantly have a 1,000 MW power plant up and running, the power station will be slowly built up.  And if, while you’re doing that, you’re also building a series of recharging stations for all the construction robots, by the time – or better yet, before – the power station is fully built you’d be all set to lay a high power cable.  This first power cable would just be for the recharging stations and to keep the base from freezing during the night.  Given that this high power cable will most certainly be in a 3D printed shell and thus won’t be heated during the day, it may be a superconducting power cable.  Something that expensive we’ll leave to the big landers.  

Parts to reuse/recycle

Without electricity for a moon base, you can’t communicate with Earth, you don’t have heating or cooling, you don’t have lights to grow food.  So protecting the power cable will be important.  Above I spoke of a 3D printed shell around the cable to protect it from micrometeorites.  Within the shell there will probably be sensors to detect cracks resulting from moon quakes or nearby meteorite impacts.  The shell may even be big enough to have mini maintenance bots constantly checking the cables.  But one way to get a quick overview of the cable, would be to have security cameras. 

Now we could send up a lander full of cameras with their mounts, or we could make do with what we have.  If we think ahead, we could design the landing legs of these spool landers to be removed and connected into a two or three meter tower.  And all the landers would have cameras for their landing system, or to photograph the immediate area of the lander.  They may not be the best choice for a security system, but it’s better than nothing.

Now there wouldn’t be a bank of screens at the base where some bored guard watched – in all likelihood – nothing happen.  Instead, maybe once an hour the cameras would take a picture and send it to a program that would compare it to a master photo for the given sun angle and check to see if anything is different.  If there is a change – say a boulder rolled down a cliff and stopped a few meters from the cable – that would be flagged and an email sent to someone.  But what about during the long lunar nights?  Well, I did mention that the ice landers could have spotlights to give them a quick look around their landing area.  These could be used to light up the area for a picture to be taken.

All of these landers would have small solar panels to power themselves.  These could be used to power remote science stations, or maybe linked together to form a small power station.  This probably wouldn’t be used on the mountain peaks because you’d want to use high quality systems there, but these jury rigged systems would be fine at the main base or any secondary bases.

These landers would probably also have batteries.  Small ones, yes, but they could be linked together to form a backup power storage system.  I say backup, because you’d want your main battery storage system to be a high quality, Earth-made one.

All of these landers would also contain components made of aluminum or plastics, which the residents of a lunar base would love to have to fashion into needed items.  And if we think ahead, we might want to design these landers to use materials that will be in demand on the moon.  They might end up with more aluminum than they can use, but be short on plastics. 


So those are some of my ideas.  It’s unlikely any of them will happen, but I’d love to be surprised.

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