Giant lunar landers like the SpaceX Starship pose a range of risks, from high-velocity ejecta abrasion damaging the lander to ejecta damaging other lunar landers or orbital assets, or even creating a crater under the lander as deep as the columnated engine plume. Masten proposes putting alumina particles in the fuel so that a landing pad is formed from the landing vehicle’s rocket plume.
Above – How FAST Landing Pad would be deployed during a mission. Credits: Matthew Kuhns
NASA Artemis landers propose a landed mass of ~20-60mT versus the ~10mT Apollo lunar module. Small landers in the ~1-5mT range, such as those expected to fly on upcoming NASA Commercial Lunar Payload Service (CLPS) missions, are also at risk from ejecta plumes, albeit a smaller risk than the large landers. In all cases, scientific payloads could be damaged due to abrasion from high-velocity regolith ejecta.
FAST Particle injection in the lander engine (left) and deposition on the surface (right). Credits: Matthew Kuhns
There are multiple schools of thought for mitigating lander plume effects. Ideas include choosing locations with more favorable surface conditions and controlling vehicle throttling and descent trajectories, but the solution that retires this risk long-term to establish a sustainable lunar presence is developing lunar infrastructure to land on. There are many approaches to landing pad design, some using in-situ resources and sintering regolith into a hardened surface, others involving bringing pad materials from Earth. These methods are reliant on multiple systems that are at low development phases and require one or more dedicated lunar missions to establish.
The Masten in-Flight Alumina Spray Technique (FAST) Landing Pad changes the approach to landing on planetary bodies by mitigating the landing plume effects by creating a landing pad under the lander as it descends onto a surface. This approach uses engineered particles injected into the rocket plume to build up a coating over the regolith at the landing location. The hardened regolith would have greater thermal resistance and ablation resistance to reduce regolith erosion rates and deep cratering. This innovation would enable large and small landers to safely perform transportation to any region on the Moon without major risks posed by engine plume effects. A lander could land in relatively close proximity to other surface assets without pre-existing infrastructure, which greatly expands potential landing locations and minimizes the need for pad construction missions. Using a traditional landing pad concept, vehicles would be constrained to land in specific lunar regions, which restricts the ability to gather science across the lunar domain. The FAST concept enhances overall lunar access and access to other planetary surfaces, including Mars, where loose regolith characteristics pose critical mission risks. The cost savings of this innovation is clear, for every dedicated lunar pad building or preparation logistics mission that does not need to be sent saves $120+ million. Providing mission assurance for crewed landings by mitigating deep cratering effects and reducing required shielding saves mass and cost for the Artemis program.
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The only way this could work is if you had a separate engine for just the last bit of the landing. Otherwise your ablative inner liner would mostly ablate long before you got anywhere near the ground.
See my idea to have an inner engine bell liner that ablates and makes the pad.
Drill holes in the bell = no-no.
Exhaust gases spread out from the rocket engine and don’t have as much energy. What takes a fraction of a second inside the rocket engine takes a second or two outside due to the dispersed plume.
So you’d melt and scatter some pad right as you are landing. Its a niche either way.
I find this injection idea to be a bit too much. Stop drilling holes in rocket bells. Why not design an ablative inner liner for your engine nozzle that evaporates and makes your pad when it hits regolith?
Now I Can Haz Grant Moniez? Or is the secret to grant money having a wire frame CAD drawing in a PPT?
Actually thrust would be increased because you are ejecting more mass. Efficiency would definitely be decreased.
That was my thought. A kind of rocket propelled “flying carpet”.
The exhaust plume is fairly dense and hypersonic, you’re not going to be injecting those particles very far into it if they start from the side.
Maybe just under the bell edge? Can be mounted from outside as an add-on component.
As I recall, gases cool when they expand, so it’s hotter inside the nozzle than outside. That said, the title image suggests that some ablation of the instapad is expected (and probably accounted for).
Logical question. If the heat of the exhaust is required to melt whatever material they’re using into an ‘insta-pad’, what prevents the next exhaust plume from remelting it and creating a gooey mess?
Why reduce the engine thrust with additives?
Design a port pad that ejects from the space ship, lands and fasten itself to the surface before the spaceship lands.
This strikes me as too much of a niche optimization.
The vast majority of cargo will go to established pads at established bases with infrastructure to mitigate dust abrasion.
Exploration craft won’t be coming in directly from Earth, likely could be topped off with ISRU source at either a base on the moon or the gateway station (lol). Either way some kind of “exploration lander” could be designed to survive dust.
Is it feasible to inject the particles somewhere else than through the side of the engine bell? That’s not a good place if you want good engine life. Not a good place on any other basis, either.
Nor do you particularly want to modify the engine if it’s going to be mostly used for things other than “first landing on unprepared lunar surfaces”.
I suppose the pintel could have a port for injecting the particles down the center, where laminar flow would keep them from coating the engine interior. Still a specialized engine, but it could be developed for lunar landings.
But SpaceX’s engines run at pretty high pressure, the injection pressure would have to be even higher to keep the particles entrained. As James says, why not silane? They’ve already been researched as fuels.
Why not silane?