[HN Gopher] Mitigating Lunar Dust: Masten Completes Fast Landing...
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Mitigating Lunar Dust: Masten Completes Fast Landing Pad Study
Author : radley
Score : 85 points
Date : 2021-09-22 15:51 UTC (7 hours ago)
(HTM) web link (masten.aero)
(TXT) w3m dump (masten.aero)
| ch4s3 wrote:
| This seems like a super cool approach for early landers prior to
| the construction of dedicated landing pads.
| RobertRoberts wrote:
| Why not drop a smaller lander first that can form the pad?
|
| Complicated solutions are a dime a dozen...
| macintux wrote:
| This seems less complex than your idea. And much faster, and I
| would wager much cheaper.
| ChuckMcM wrote:
| Oh I like this very much. The previous idea I read about was a
| crawler that had essentially a giant microwave antenna pointed
| down that would "pave" where it drove by melting regolith under
| the antenna and then letting is cool.
|
| Of course that required landing the paver near where you wanted
| your payload to land, and then it had to finish before you lander
| came in. This is, I suspect, the "$120M" solution they alluded to
| on that web page.
| lmilcin wrote:
| I wonder if the problem is as big as they are painting it.
|
| There is no atmosphere and very little gravity.
|
| The exhaust gasses expand out in a hurry and any particles
| should not be spending time in any kind of vortices -- should
| travel outward in a straight line along with the exhaust.
| tastyfreeze wrote:
| That is a damn clever solution for one off landing pads. I wonder
| if a man portable "pad gun" could use the same idea, without
| throwing the human off the surface, to make a more permanent pad.
| NortySpock wrote:
| Might be able to do a slower deployment method for that.
|
| A little like pouring concrete, you'd pour molten aluminum (or
| molten steel?) into a prepared area or crater and let it settle
| and cool.
| ch4s3 wrote:
| Probably pretty expensive to get that to the moon from earth
| WJW wrote:
| It'll be pretty expensive no matter what the construction
| material is if you have to ship it from Earth, since
| transportation costs will dwarf any costs for the actual
| materials.
| ChrisMarshallNY wrote:
| It won't come for free, though.
|
| As anyone that has ever had to work with sandblasters will tell
| you, running powder through things has its own challenges.
| skykooler wrote:
| Particularly alumina, which is literally the abrasive used in
| sandpaper.
| NortySpock wrote:
| Masten Aerospace keeps doing super cool stuff with really elegant
| designs.
|
| I hope they keep winning (and keep their mojo) in the growing
| space race.
| LeifCarrotson wrote:
| > 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 wrote:
| > 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 wrote:
| Drop 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 wrote:
| ? 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?
| [deleted]
| CarVac wrote:
| I wonder how this impacts the reusability of the engine the
| alumina is fired through.
| burnte wrote:
| Little to none as it's injected into the nozzle. Engines are
| designed to extract maximum energy from the propellant, so the
| expansion curve of the nozzile is made to direct exhaust
| directly aft with no further expansion. When you see a rocket
| taking off wth a plume bigger than the nozzle, that's lost
| energy, but unavoidable due to the changing pressure of the
| atmosphere. Once you're in orbit, you can use vacuum-designed
| engines. Youd' inject these into the nozzle further enough down
| that they go directly down and out, not to the sides. You don't
| need to inject them with very much force at all, just enough to
| keep it away from the injector and near wall. You can design it
| so that virtually none of the material ever hits the nozzle
| walls.
| lmilcin wrote:
| > so the expansion curve of the nozzile is made to direct
| exhaust directly aft with no further expansion.
|
| Exactly the opposite. The gasses will _INFINITELY_ expand as
| the atmospheric pressure on the Moon is for all intents and
| purposes exactly zero.
|
| > Engines are designed to extract maximum energy from the
| propellant, so the expansion curve of the nozzile is made to
| direct exhaust directly aft with no further expansion.
|
| Engines are _NOT_ designed to extract maximum energy. Engines
| are designed for _COMPROMISE_ between extracting maximum
| energy and other parameters like mass of the rocket.
|
| For example, the engine could extract more energy from the
| propellant if the bell was larger. But that would make it
| also heavier and would reduce the performance of the rocket
| as a system.
|
| Another example, part of the fuel is wasted to create screen
| to protect the engine from overheating. It is injected on the
| sides of the engine and does not burn. This waste is a
| planned compromise because better cooling mechanism would be
| much heavier and so wasting a little bit of fuel is best way
| to improve total performance of the rocket.
|
| > Youd' inject these into the nozzle further enough down that
| they go directly down and out, not to the sides. (...) You
| can design it so that virtually none of the material ever
| hits the nozzle walls
|
| No, you can't.
|
| You mister, need to learn some physics.
|
| The way engine works is by creating pressure. That pressure
| acts on the bell ( _the sides_ ) and transfers to the rocket.
|
| The "sides" aren't there to ornament the rocket, they serve a
| very important purpose as they are the surfaces on which the
| pressure of the gasses act to propel the rocket.
|
| The vacuum regime isn't any different. There is positive
| pressure within the bell and this propels the rocket forward
| as the gasses expand backwards.
|
| If you injected (ejected) fuel directly down and out you
| would get pitiful thrust the likes of your bottle of coke
| gets when a mint is dropped in it.
|
| There are engines that do what you describe (ion engines) but
| they work in a very different way.
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(page generated 2021-09-22 23:01 UTC)