Debris risk mitigation during landings on Mars or Moon

[dkovacic]

I have a question regarding risk mitigation techniques of equipment damage during moon/mars landings.

For any lunar/mars base, it is necessary to have landing zone quite near the rest of equipment, especially during initial infrastructure deployment. Propulsive landings on Mars (and especially Moon) involve hot, high velocity exhaust hitting vertically into a surface. Since such material contains dust and small regolith particles, I would expect that they can get significant kinetic energy during landing.

The question is how to estimate or model probability of hitting equipment deposited in the previous landings?

Only actual similar event is Apollo 12 landing near Surveyor 3, but as far as I understood, there was no direct line of sight nor direct exposure to the dust spray caused by the landing.

[rpapo]

I would think you could mitigate this by bulldozing a ring of material up around the landing zone, or between the landing zone and any structures.  Alternatively, you choose a landing zone that is over or around a hill from any structures.  Both alternatives have their problems, though.

[dkovacic]

Your solution does make sense when you have bulldozer/rover/transporter onsite. But having all that, probably you could make a flat surface from regolith. So this solution would not be suitable for initial equipment deployment.

[rpapo]

Your solution does make sense when you have bulldozer/rover/transporter onsite. But having all that, probably you could make a flat surface from regolith. So this solution would not be suitable for initial equipment deployment.

You don't need debris mitigation for the first landing.  The problem is once you have something on the ground that you don't want punctured or otherwise damaged by random rocks flying around.

And in any case, the "problems" I was referring to, I meant specifically: (1) the cost of getting a bulldozer or something functionally equivalent down there, along with fuel for it, or (2) the problems involved with any landing site that has barriers of any sort nearby.  Either way, you've got problems.

[the_other_Doug]

I would suggest that what is really wanted for such an application is concrete, or something like it, for your landing pads.  Once you have a permanent location, you can use either radar landing guidance or, when a constellation is available, GPS guidance to land equipment onto the concrete landing pads.

A concrete equivalent will also, of course, be extremely useful in building many other structures we want to build, both for habitation and other uses, on the Moon, Mars and elsewhere off of the Earth.

The issue with concrete, of course, is that it has an aqueous phase that requires water at some point in its processing, to achieve the chemical hardening.  Since a Moon or Mars base is going to be water-poor for some time after establishment, I doubt that conventional concrete is going to be the answer.

The person, or company, coming up with a "dry concrete" process that will work on the Moon/Mars (i.e., without a lot of water, and in a near- to full vacuum) will literally lay the foundation of our future extra-terrestrial homes...

[MattMason]

This abstract of a 2005 NASA workshop on lunar regolith simulants and construction thoughts might be of interest. I recall that a Japanese firm, probably using simulants from Mt. Fuji, were making bricks in a test process years ago.

[rpapo]

This abstract of a 2005 NASA workshop on lunar regolith simulants and construction thoughts might be of interest. I recall that a Japanese firm, probably using simulants from Mt. Fuji, were making bricks in a test process years ago.

Yes, but were those bricks made in a vacuum chamber?  Much of the unique quality of lunar dust comes from the fact that there is next to no atmosphere there, and there is a constant rain of solar wind.

[Eric Hedman]

I seem to remember somebody had the idea to use either lasers or microwaves to melt and harden surfaces for dust mitigation on the Moon.  I wonder if the concept would work well enough for creating a landing pad.

[dkovacic]

As far as I have seen, for initial landings (for example, human landing needs to be close to a habitat and return vehicle. In one EDL design document I have read that the landing site should be less than hundred meters from the previously landed infrastructure. I don't see the proposed solutions to be really good fit for initial missions. Though laser beam surface melting from orbit would be cool (putting aside obvious military aspects of such technology).

Skycrane concept used for Curiosity seem to avoid close contact with the surface material. In vacuum exit pressure of the exhaust seem to drop rapidly with distance from the nozzle, but cannot be reused for ascent.

I wonder how will MCT design addresses this issue. Landing on Earth will be easy compared to that, since the landing surface will always be prepared up front.

[JasonAW3]

Three basic solutions here. 

     One, build a berm around the landing site high enough that that most debris will not make it past the wall.

     Two, build the colony on an elevated portion of terrain, (or would that be Areain?) with a ramp structure to it, (again, bulldozed regolith) so debris kicked up won't reach the colony.

     Three, Build the colony underground, with entrances behind berms high enough to act as debris catchers.

     To minimize debris kicked up under the landing craft, place the engines around the perimeter of the craft, with the exhaust canted outwards at an angle.  This would essentially shove any debris kicked up away from the craft.

     The debris can further be minimized by raising the engines to either mid height along the side or just below the top of the craft, minimizing any actual exhaust impingement on the landing site at all.  This latter part is much the same as the technique used with the Sky Crane technique used landing when landing the MSL.

[Coastal Ron]

For any lunar/mars base, it is necessary to have landing zone quite near the rest of equipment, especially during initial infrastructure deployment.

The landing zone should be separate always, or at least until we have a very mature space transportation system.  It's important to note that today we have airports in crowded areas, but they didn't start that way - they were well away from population centers, but the populations grew into them.

But for safety sake, and not just debris but crashes, the landing zones should not be next to inhabited areas.

Propulsive landings on Mars (and especially Moon) involve hot, high velocity exhaust hitting vertically into a surface. Since such material contains dust and small regolith particles, I would expect that they can get significant kinetic energy during landing.

On the Moon ejected or accelerated material only has to deal with gravity, so it would probably be easy to calculate the ejection zone of a landing area once you understand what type of landing engine layouts are to be expected.  For instance for Apollo style lunar landers that only have a single engine which is close to the surface, that will probably push the most amount of mass out of the way, and at the highest velocities.  However if you have an ACES type horizontal lander, which would have an array of smaller engines high off the ground, the ejecta zone would be much smaller.

And to a degree, I don't think berms or walls make much of a difference, since anything that gets over them will be a flying projectile that has to be accounted for.  But a hill that provides a significant vertical barrier would probably suffice - just drive around it to get to the base.  That's doable.

[sghill]

I seem to remember somebody had the idea to use either lasers or microwaves to melt and harden surfaces for dust mitigation on the Moon.  I wonder if the concept would work well enough for creating a landing pad.

That technique is called "soil vitrification"

http://forum.nasaspaceflight.com/index.php?topic=37466.msg1376434#msg1376434

[Hotblack Desiato]

How precise will landing on mars be?

SpaceX currently lands first stages on very small spots (they just don't remain upright every time).

So how about landing directly on a crawler (an autonomous spaceport drone crawler?). That thing should be made on mars (it's clearly too big for transportation), and carry the landed craft to the base. No problem with debris, no problem with rocks stuck in engines, and so on. It's just not an option for the first few crafts.

Maybe it looks like the lander stage of the Apollo missions, but on wheels and with a larger surface area? Maybe it's even possible to combine several landers to form one larger platform?