Planetary landings are a messy business that can be dangerous for anything nearby, but they can also be risky for the landers themselves. Engine plumes can kick dust, dirt, and rocks back up towards the spacecraft, endangering engines, science payloads (this happened to a weather instrument on the Curiosity Mars rover), and potentially even astronauts.
We’ve managed so far because most unmanned probes, and even the Apollo lunar landers, have been light enough that their engine plumes have been relatively mild. But as we look towards scaling up our presence on the moon, we’re going to need rockets that are much, much bigger. NASA’s proposed Artemis landers will be somewhere between double and quadruple the mass of Apollo, and modeling suggests that one of these could displace something like 470 tons (!) of lunar soil during landing.
Through NASA’s Innovative Advanced Concepts (NAIC) program, the space agency is funding a creative new approach towards making planetary landings safer for large spacecraft. Masten Space Systems is developing a concept for “Instant Landing Pads,” where a spacecraft builds its own landing pad as it descends towards the surface. By not requiring landing pads to be constructed in advance, this technique would be safer, cheaper, and help us establish a base on the moon as quickly and efficiently as possible.
In all of the renderings of lunar landings that we’ve seen so far (from folks like Blue Origin, Boeing, SpaceX, and NASA itself), the landers themselves have touched down on the lunar surface directly, without a landing pad. It’s certainly possible to do this with large landers, if you’re choosy about where you land and add enough shielding to your vehicle for it to be able to withstand whatever it might kick up. And depending on the size and power of the engine (or engines) and the surface that they’re interacting with, this can be a lot of material—Masten has been doing some testing on Earth, and you can see how much of a problem this can be:
Finding the right landing location to avoid effects like this, and adding enough shielding to protect the lander, would be restrictive to any lunar program. Shielding is a significant amount of mass that takes away from payload, and if there’s no safe landing area near where you want your moon base to be, you’re out of luck.
The conventional solution is to send smaller landers first, and use local material to construct a landing pad. A project called PISCES is working on doing this with robots, for example. This could certainly work, but you’re adding months or years of lead time to your overall mission, and Masten estimates that it would cost over $100 million for every dedicated lunar pad building or preparation logistics mission.
What Masten wants to do instead is to put a pad, instantly, on a planetary surface underneath any rocket just a few seconds before landing.
The system that Masten is developing with NIAC funding is called FAST, or in-Flight Alumina Spray Technique. Here’s how it would work: a few hundred meters above the surface of the moon (or Mars, or anywhere else you want to land), your lander comes to a hover. Alumina pellets are then fed into the engine exhaust nozzle, where they get partially melted in the engine plume and blasted down onto the surface. Most planetary surfaces that a spacecraft would be landing on are cold enough that the alumina cools and hardens on contact, and over the course of about 15 seconds, something like 300 kg of alumina gets layered into a totally functional landing pad. You then land as normal, ablating the pad a little bit but not digging a crater under yourself or blasting dirt and rocks all over the place.
Masten has been testing rockets on Earth for years; their fleet of terrestrial test vehicles has accumulated more than 600 rocket powered landings (on landing pads). This idea came directly out of testing how rocket engine plumes kick up material, Masten Chief Engineer Matthew Kuhns tells us. “I started brainstorming ideas around ways you could land without needing a precursor mission to create landing pads. Lots of crazy ideas later, this one stood out.”
NIAC is all about funding ideas that seem crazy, but that have enough technical feasibility that they could ultimately pay off.
“We will spend the next 9 months looking at how this would benefit the Artemis moon landings,” Kuhns says. “NIAC projects as a rule are very ambitious and usually 10+ years out to use, but in this case since we can build on a terrestrial technology I think we can move a bit faster.”
Masten will be teaming up with Honeybee Robotics to figure out exactly how engines can be modified to use FAST. FAST requires a system to transport the landing pad material into the engine, which is basically the opposite of a pneumatic sampling system that Honeybee has been working on. Testing is still to come, says Kuhns, but with Masten’s rocket experience, we’re hoping that moving “a bit faster” is a bit of an understatement.
We also asked Kuhns if he sees any problem with leaving these instant landing pads scattered about on the moon. “That would be a good problem to have,” he told us. “It would mean many many missions to the moon, a sustainable presence, and lots of science. Depending on their location and material, you could actually do science with the FAST landing pads and use them as laser or radio reflective arrays.”
NIAC projects are typically funded through three different phases as their technology readiness level increases. A year from now, we hope to see these Instant Landing Pads make it to phase two, which will bring them that much closer to helping us return to the moon.
Source: Spectrum
