84 thoughts on “Lunar Lander Problems”

    1. The Moon gets impacted by many small impactors, and a small impactor would cause more dust than a lander.

  1. I assume the mascons will sweep LLO clear given time?

    The SpaceX entrant has landing thrusters up high. It looks to me like Blue Origin’s entrant might be more effected.

    The obvious mitigation strategy is to build a landing pad but you have to get there first.

    1. None of the dust will go into LLO. It will either land somewhere on the moon, or escape.

      Yes, you have to get there first, but my point is that building one should be of the highest priority after landing, for future activity, to minimize creation of more.

      1. And I see what you mean. Anything kicked into lunar orbit will have its perilune near the ejecta site one go around and impact near there. It’s escape or bust.

        1. Worse. Anything ejected upward will have a perilune well below the moon’s surface and it will impact far away on the descending leg. Potential hazards to hardware far removed from the landing site!

  2. Is that like the Star Trek episode (Next Generation? DS-9? Voyager?) where too much space travel above Warp Factor 5.5 put too much wear-and-tear on Sub Space and the Federation has to impose the “double-nickle” speed limit on itself and hope the Romulans would observe similar restrictions?

        1. The lesson is don’t dig yourself into a hole with lazy writing. The set up this ‘thing’ and proceed to essentially ignore it.

          1. Yeah, the only lasting impact of that story line was Voyager’s variable-geometry nacelles. Then again, it wasn’t completely ignored like the aliens from ST:TNG “Conspiracy”, so there’s that.

          2. Then again, it wasn’t completely ignored like the aliens from ST:TNG “Conspiracy”, so there’s that.

            They are saving that plot line for Star Trek: The Last Generation…

          3. The lesson I had in mind is that starting with the The Original Series, Star Trek was about one or another social concern. I am surprised that whatever Star Trek spinoff doesn’t have a villain with comb-over hair and orange tinted skin who says, “Chy-nah!”

            I guess Force of Nature predates the current setting of our hair on fire over CO2 emissions while the Romulans, er, I mean the Chinese keep building coal-fired power plants. But it had the same sanctimonious air (“we beamed aboard two scientists who are blaming the disappearance on those ships on damage to sub space caused by warp fields.”

    1. ‘cause you need another season of episodes rather than risk a subspace collapse and everyone gets stranded somewhere when warp drive no longer works.

      Star Trek -> Lost In Space… Danger Will Riker….

      *The medication is strongest in the morning…

      1. What is that makes Lost in Space so cringe-worthy whereas we suspend cringing for Star Trek?

        How is Dr. Smith whinging “the pain, the pain” makes a viewer wince whereas in the Star Trek episode Devil in the Dark, Spock mind-melding with the rock creature and calling out “the pain, the pain” is a premise we accept, even after having seen that episode multiple times in re-runs?

        I remember as a kid that I thought Lost in Space was cringe-worthy whereas I thought the other Irwin Allen project Voyage to the Bottom of the Sea was kind of cool. I saw part of a badly acted episode of Voyage on TV recently and thought that too was stupid, but what is it about Lost in Space that makes it even worse?

        Is it that in Lost in Space, thet Robinsons don’t actually go anywhere but just exist as a dull, suburban family, where the aliens show up as bad neighbors who encroach on their property with their tacky landscaping, explaining they were forced to do so because the Robinson’s don’t use Weed-and-Feed on their lawn?

        1. What is that makes Lost in Space so cringe-worthy whereas we suspend cringing for Star Trek?

          It’s pretty clear why. One system runs on dutronium, the other dilithium. If that makes no sense to you, play this song twice.

  3. Why not just take some water with to spray down the landing site on descent for dust suppression? This would stand a better chance of working with high mounted rocket nozzles I would think.

      1. well could use super cooled water, which would be rather tricky. Or you have salt added to water, and the water can kept easily well below 0 C.

        1. Ie:
          “The world’s saltiest body of water is tucked away in a valley in one of the most extreme environments on Earth. It rarely snows and never rains in the McMurdo Dry Valleys. Winter temperatures can drop to -50 degrees Celsius (-58 degrees Fahrenheit), and the few ponds and lakes in the valleys are capped by ice that is several meters thick.

          Then there’s Don Juan Pond. The ankle-deep pond in the lowest part of Upper Wright Valley is so salty that its calcium-chloride rich waters rarely freeze. Salt particles lower the freezing point of water by moving between water molecules and impeding the formation of the crystal lattice structure of ice.

          With a salinity level over 40 percent, Don Juan is significantly saltier than most of the other hypersaline lakes around the world. The Dead Sea has a salinity of 34 percent; the Great Salt Lake varies between 5 and 27 percent. Earth’s oceans have an average salinity of 3.5 percent.”
          I was thinking of Death Sea levels which is more salty than ocean. Average seawater freezes at about -2 C.

        2. Of course could just use off shelf anti-freeze.
          But could you just flow it [like garden hose flow of very salty water into rocket exhaust {and it adds thrust, as you are accelerating the speed of the salty water}. And leaves salty crust on lunar surface- or you make a launch pad of salt.
          It would require a lot salt to make a pad, but after many landing, you get more of a pad.
          Simple table salt could useful on the Moon, or use something else which is has other uses.

    1. Work on creating regolith-based concrete has been going on for some time, and there are actually samples of some early mixes attached to the exterior of ISS to test their durability in vacuum and extreme thermal cycling. They don’t use water, but mineral polymers.

      I personally think that a 179 mile long runway would ultimately be best. The lander is put on a very shallow descent trajectory, and touches down on skids which dissipate energy by ablation. At 1/2 g deceleration, 179 miles would suffice to bring it to a stop with no rocket braking at all.

      Maybe add two 500 foot overruns, to be on the safe side.

        1. Donald Kingsbury wrote an SF novel “The Moon Goddess and the Son” in the early 1980s. The central gimmick was a thing called a spaceport which was a linear accelerator which could work both ways. The spaceports were in LEO and you get in your rocket fly upwards, enter the end of the spaceport and are accelerated to orbital velocity. Landing was the opposite which greatly eases the heatshield problem. Also useful for trans lunar injection and return.
          I really liked the characters in the novel.

          1. Doesn’t appear to be Kindled. A pity. Maybe I’ll buy the print version.

            I had heard of this kind of thing before. Only the version I heard of was an accelerator being held high aloft in the thin upper atmosphere by helium balloons, but the same idea with smaller rockets. It was supposed to be powered by ground based lasers, IIRC.

        2. A shorter version was serialized in Analog along with an article explaining the spaceport concept in detail.

      1. Couldn’t we dust off (sorry) some of the old “nuke the moon” plans? Maybe a small device very near the surface, at least enough to generate radiated heat could melt some of the surface into a stable glass?

    2. Masten Space had a contract to examine the injection of solids into the rocket plume during landing to flame-spray a coating onto the regolith. Not sure what ever happened with that.

  4. Just gently place aerogel blocks to wall off a landing area. Super easy. Barely an inconvenience. Don’t worry about it.

    Use a lunar lightning rod to create a static charge that attracts the dust.

    Am I eNgenEErinG right?

  5. There’s something wrong with all of this, but I am nowhere near numerate enough to attempt to understand what. Musk seems to think so too, so I guess I will sit back and see what happens.

    On the other hand, there’s nothing wrong with the idea of a large, permanent Moon base with a large, vacuum-competent concrete landing pad. Explore the Moon with long-range rovers and maybe “thruster helicopters?”

    1. 2001 A Space Odyssey is looking more prescient by the day. But what I really want is the technology they used to create those perfectly square ham sandwiches they were handing out on the “moon bus”…

  6. Lunar dust was a major problem for the Apollo astronauts, who suffered various respiratory ailments as a result of exposure. They were fortunate enough to not have it so severely infiltrate the LM as to keep the hatch from sealing, or clog switches to the point of failure. Any long-term habitat on the Moon will have to deal with it quickly.

    1. Compressed air is your friend. We will need lots and lots of it on the moon. Should we chemically manufacture it from liquid feed-stocks as wouldn’t that be more economical?

      I feel the need to review Andy Weir’s Artemis again…

      1. Anybody that’s ever dealt with lots of fine, possibly flammable, possibly toxic dust will will knock that blow gun out of your hand and attempt to strangle you with the hose in self defense. All compressed air does is relocate the dust into the atmosphere at high speed and maximum dispersal which is not helping.

        There are oils with extremely low vapor pressures that might help or just make an almighty mess.

        The gas exiting from thrusters higher above the surface will disperse but it won’t slow down. This might reduce the problem from larger particles but the greater area might make the problem of smaller particles worse.

        1. You really believe lunar regolith is flammable?
          We’re talking about the Moon here.

          ChatGPT says otherwise:

          Lunar regolith itself is not flammable in air. Lunar regolith is primarily composed of silicate minerals, which include materials such as pyroxene, plagioclase, and olivine. These minerals are non-flammable and do not burn in air.

          However, there are some considerations to keep in mind:

          1. **Metallic Iron Particles**: Lunar regolith contains small amounts of metallic iron particles due to the constant bombardment of micrometeorites. While metallic iron can oxidize (rust) when exposed to oxygen, this process is typically slow and does not result in combustion.

          2. **Elemental Composition**: While lunar regolith contains elements like silicon, aluminum, calcium, and magnesium, these are typically in oxidized forms (such as silicates and oxides) and are not prone to burning.

          3. **Dust Behavior**: While not flammable, lunar dust is extremely fine and can pose inhalation hazards. It is also highly abrasive and can pose mechanical risks to equipment and human tissue.

          In summary, lunar regolith is not flammable in air. The materials it is composed of are stable and do not support combustion.

          We’re talking mostly silicate minerals here, not soy dust.
          Nor are we doing this inside, but outside. Maybe with a dust barriers to catch the blow-off. Aerogel has been mentioned.

          Better than bringing it into the hab and breathing it.

          And mixing it with any kind of liquid is going to make mud, even more nasty.

          1. Now maybe there are easier gases to obtain on the moon to use other than air. I’m open to suggestions.

      2. LOX tank boiloff. Outside the airlock, methane could also be used because it can’t contaminate the air inside.

        Use every part of the pig, including the squeal.

    2. The first thing they need is a mud room(s). Likely a cleaning station outside the airlock and one on the other side.

  7. I was talking of long experience with terrestrial dust of all kinds. Keeping it out of habitats probably comes down to using downdraft laminar flow chambers combined with such high tech accessories as brushes and carefully controlled air blasts to dislodge dust from nooks and crannies. The same as entrances to terrestrial clean rooms.You’ll not be wearing your outside clothes inside. Inside, you’ll want good vacuum cleaners with very good filters. Sticky surfaces so whatever dust settles, stays put. At least on the Moon there’s gravity and the dust eventually settles rather than the case of the ISS.

    Outside, gas blasting will only increase the ambient dust from other activities, not helping. The big problem is designing things like suit seals that will survive and machinery of all sorts. I’ve designed a lot more farm machinery than space craft or lunar rovers but you generally have two choices. One is hard steel and cast iron joints “lubricated” by the ambient medium, that inevitably, grinds itself away until it’s replaced. The other is to use intricate and fragile seals, which also fail regularly and replace slow attrition with sudden seizure.

      1. I’d think CO2 would be good for purging seals. It liquefies easily for storage and has to be removed from the breathable air anyway. Gas purged seals are common on machine tools. It wouldn’t take much, just enough pressure so to prevent dust infiltration. It’s hardly more reactive than argon up to fairly high temperatures and non toxic at low concentrations.

        All this does bring up the question of just what do we need from the Moon anyway? Maybe Farside for radio astronomy, but what’s near the surface that we probably can’t find on an asteroid without the pesky gravity? Will it really be easier to establish the infrastructure to produce water on the Moon rather than lift it from Earth? That’s assuming there is water available in quantity and accessible.

        1. All this does bring up the question of just what do we need from the Moon anyway?

          Andy Weir says cheap aluminum and Zero Attenuation Fiber Optic (ZAFO) Cable.

          Duncan Jones and Nathan Parker say Helium-3 for fusion reactors on Earth.

          Gerard K O’Neill says raw material to manufacture Space-based Solar Power Satellites in order to finance a space colony at L5.

          Yusaku Maezawa says someplace to fly over.

          NASA’s Ranger 4 as someplace to crash into, we calculate.

          1. Plentiful, non-artificial 0.166g, alongside plentiful building materials? Colonies if 0.166g is enough, vacation resorts, otherwise. People pay good money to ride around in floating hotels like Icon of the Seas…

          2. Going to center of Earth, seems rather difficult, going near to the center of the Moon, could be far less difficult.

    1. As a user of farm machinery I always appreciate it when the engineers and designers realize there is a difference between maintenance in the field (literally 🙂 vs assembly in the factory. And make machines and parts thereof such that partial disassembly and repair is possible without assuming that once a machine is manufactured that access to critical repair areas is no longer needed.

      If you’ve done this is the past kudos and my thanks to you.

      1. I should say past user of farm machinery. It has been awhile. And the machines today make the machines I used look like toys by comparison.

        I understand now why my grandfather back in the day was comfortable driving any single letter tractor from A to M, but left the 706, 956, 1066 and 1566 to Dad and I….

          1. Are you talking about the young-farmer woman in full eye makeup who wears tall boots with short-shorts as her unseen partner drives her around in an ATV, taking video as she gets soaked leaving the ATV cab to make repairs to a center-pivot irrigation system while it is operating?

            Who gushes in amazement and wonder at a freshly germinated corn seedling? (Yes, the crop was corn.)

      2. Briggs & Stratton knew (or used to). Metal fatigue took the muffler off my mower yesterday. Turns out I can just buy a new one and screw it on. The mower is 15 years old.

      3. I’ve seen the same sort of design philosophy with a large and expensive lab instrument. The machine had a proprietary single board computer inside that communicated to assorted other boards, that in turn were connected to and/or controlled various functions on the machine. The real time software control was a giant leap forward compared to older machines that had banks of dials and potentiometers. The onboard master computer in turn communicated to a user operated computer running Win7 via a usb connection. Upgrading to Win10 was a real nail biting experience, but required by IT.

        All was great, except some times the internal master computer would mysteriously stop talking to one of the critical sub assemblies. I suspect it was due to integer overflow of a timer in the proprietary firmware. This machine would take the better part of a week to settle down if you just turned it off, so alternatives were vital. The brilliant engineers in Germany, who were bright but did not actually use there machines, never allowed for either a soft or hard reset.

        All we could do was to open up the system and power down the internal usb communications card by pulling its Molex connector, which basically performed a hard reset. Things usually were OK if you got things running again before various parts of the system cooled down. I’m glad I’m retired.

        1. Now take that idea and translate it to a literal nuts and bolts scenario. You are trying to take apart a piece of a combine harvester in order to get at a bearing that has failed and in the process of removing the various bolts holding in place an access panel to gain access to that bearing you hear a “spling” sound and a piece of the machinery inside all of a sudden slumps to one side. And that was some 50-60 odd years ago. Nowadays, farmers don’t work on these machines. They haul or drive them back to the farm machinery dealer, or they may request an emergency house call and the dealer may attempt a field fix by having their on-call mechanics drive their repair truck out to the field to have a look. The shop manual for these things consist of a dozen or more three ring binders. I’m glad I don’t try to fix these machines anymore.

    2. Alternate histories always claim that many of the things done today could have been done in the past, and that may be true in some cases, but SpaceX was able to do what they did because of advancements in many other industries and workforce skills.

      Thanks for the great perspective.

      People like to denigrate farmers and farm work but they provide valuable advancements that can be used elsewhere. We are where we are today because of a tangled web of advancements that couldn’t have been predicted in the past with any specificity, and certainly not centrally planned.

      1. Farming is easy, or at least according to Michael Bloomberg.

        “You dig a hole, (makes gesture) drop in a seed, cover it up with dirt, water it and up comes the corn.”

        1. “You dig a hole, (makes gesture) drop in a seed, cover it up with dirt, water it and up comes the corn.”

          Damn, that was supposed to be soybean…

  8. The amazing thing about living on Earth is that you can fill a bucket from the tap and it will be inhospitable for sustaining life but if you let it sit for a month then ingredients to sustain life appear on their own.

    We have to bring all that bacteria and microorganisms with us. Or at least I assume so.

    No one has let a bucket of water sit for a month (in a place safe from sublimation and temperature) on the lunar surface or mars to see what happens.

  9. “And the machines today make the machines I used look like toys by comparison.”
    We did some precision agriculture work on a broad acre farm some years ago. With acquistions and amalgamations the owner now counts his land in square kilometers not hectares.
    After listening to the woes of each new (short) generation of equipment I concluded the cabs should have the word EXPERIMENTAL in 2″ high letters visible at each door.

    1. lol. The thing of it is these machine all feature access LADDERS just to get to the cab. The wheels alone are about as tall as I am. If they have wheels (as opposed to tracks).

  10. Just spitballing a proto-idea, but instead of relying on nozzle height and cosine angles, what if the lander was shaped like a frisbee with the exhaust coming entirely from the rim, somewhat like an aerospike engine, and when nearing the surface the exhaust is canted somewhat inwards toward the center of the lander.

    One conception is that all the dust kicked up is trapped by the curtain of exhaust coming down and in from the rim, trapping a giant cloud of it right under the lander. The exhaust gases and dust of course aren’t going to remain trapped by an air curtain in a vacuum, but particles aren’t going to maintain high velocities traveling the wrong (upstream) direction through an exhaust plume, either.

    Whatever happens would be radially symmetric, given the geometry, so it should be fairly easy to model, including the overall exhaust pressure under the vehicle versus altitude, as it might act like a very leaky air cushion vehicle.

    1. Are you suggesting an exploratory lunar lander study grant be awarded to Stoke Space out of Kent WA?

      Sounds somewhat akin to what they are working on.

      1. It does look very similar.

        The notion that was going through my mind was to maximize the footprint for a given weight, to keep the lunar surface at a low peak or average exhaust pressure (lbs/sq foot). As Phil Metzger showed, the dust doesn’t start flying until there’s enough high-velocity gas density to get it unstuck and entrained in the exhaust stream.

        Regarding any dust getting into lunar orbit, just lower the engine ISP down to around 160 seconds and the exhaust won’t have enough velocity to get to LLO.

  11. The other idea to consider, is that with a high cosine angle of high mounted landing rockets, you might be able to keep the ISP low enough to prevent deep erosion into the compacted layer by also relying on pneumatic landing legs to absorb some of the impact force of a higher speed landing as well as for lander leveling. We should seriously consider this as a more robust approach for multiple landings regardless. Another consideration is a ring berm around the landing site to force the ejecta into a more vertical trajectory normal to the surface so that lunar gravity can limit the dispersion. One would assume soil moving technologies will be included as one of the desired first missions after the initial second round of flags and footprints.

    Building some sort of structural landing pad I would think would be a top priority.

    1. Of course soil movement could make matters much worse than simple rocket erosion. The ring berm might have to be something brought up from Earth and constructed on site. Those that want to tunnel into the moon’s surface to build habitat on a large scale might have to consider that.

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