3 ms·
> After the base layer is deposited, alumina particles of approximately 0.024 millimeters in diameter would be required to heat up and liquify as they pass thro
by LeifCarrotson 5y ago
> After the base layer is deposited, alumina particles of approximately 0.024 millimeters in diameter would be required to heat up and liquify as they pass through the engine.... The pad would then require 2.5 seconds to cool before the vehicle touches down for a safe landing.
That's really, really fast solidification. I'd be worried about inadvertently sinking in or brazing the landing legs into the pad and making takeoff impossible. On investigation, though, a 6 meter diameter disc has a surface area of 28 square meters. Building that disc with 186 kg of alumina, which has a density of about 4 g/cm^3, would give you a plate with a thickness of only about 1.6 mm.
I think this is just a one-time-use landing pad, not a landing-and-takeoff pad. Its purpose is to prevent lander damage and contamination of the research area by ejecta.
The tech is still cool, don't get me wrong, but I guess I imagined something more like a spaceport runway with a massive slab of steel-reinforced concrete. This is more like dropping a Nomex blanket to land on than what I had in my head when I read "landing pad".
- SideburnsOfDoom 5y ago> a massive slab of steel-reinforced concrete. There will not (initially) be a steel-reinforced concrete structure on the moon. The best that can be done in the short term would be e.g. a covering blanket, or a application of (solar?) heat to fuse the surface.
- trhway 5y agoDrop a small Wall-E with solar powered laser sinter few days before big landing. On a general note - a Dr. Evil can make Moon much less accessible just by kicking some amount of dust into low Moon orbit. One can imagine future fight tactic in an environment like this.
- OneTimePetes 5y ago? Thin foil in space, forming a covex mirror, ray of light focused on the surface, melting the spot over and over until its flat glass?
- LeifCarrotson 5y agoHolding that foil in a well-focused lens shape, and keeping it focused on one spot on the surface while in orbit around the moon, would be pretty tough. Even though a mirror surface can be like 90% efficient, I think you'd have a better chance of putting down more energy by collecting the energy with 30% efficient solar panels, and transmitting it with a tightly collimated, easily focused, easily aimed laser that may only be 30% efficient. That's only 9% of your incident energy output to do useful work, but I doubt you could be as successful with a foil mirror. And when you've got those constraints, why would you not land it on the surface as a rover and work from a meter away instead of working in orbit many kilometers above the surface? The latter saves some landing energy and rover mechanisms at the cost of collimation requirements. It gains you the freedom to put your landing pad anywhere on the surface instead of having to drive there, but I don't think we need that yet.
- robbles 5y agoI was wondering how they'd handle the 2.5 seconds without landing, given that the engine plume is going to heat it back up again. Are the particles being released from a much higher point than the pictures suggest? Otherwise you'd think it would drop into the still molten pad after less than a second, right?
- marcellus23 5y agoIf the engines run long enough for the lander to start going up again, it could be more than 2.5 seconds until it impacts the ground.