archermarks

9 ms·

61.
by archermarks 4y ago
That's a cool idea! That way if you miss the leading indent you can still tell a block of text is indented.
62.
by archermarks 4y ago
This movie is one of my favorites. It's absolutely hilarious and so so 90s in the best way.
63.
by archermarks 4y ago
In this case, we know they would be able to interact via electromagnetic waves. So we would not need to invoke quantum wavefunctions in order to get the right behavior. The tricky bit is predicting the type of wave, their growth, and their
64.
by archermarks 4y ago
I still don't know if i really follow here. We are not detonating anything, and there is no precise time required. The confinement is magnetic in nature and not really a property of the gas species.
65.
by archermarks 4y ago
Appreciate the clarification. I am familiar with RANS modeling to a reasonable extent but not with a lot of the modern developments. We're still kind of at the stage of trying to find something that works as well as Prantdl's mixi
66.
by archermarks 4y ago
Ok, so looking at that phase diagram, we operate in a drastically different regime than you might be thinking. The pressures we get to are maybe 10^-3 Torr at best. The propellant is extremely rarified and not particularly hot.
67.
by archermarks 4y ago
Unless I misunderstand your meaning, I guess in a certain sense you could frame it in that way, where you have a rotational drift which provides energy to an axially-propagating wave. I'm not well-versed in black hole plasma physics. I
68.
by archermarks 4y ago
Both of those, but also additional mass due to extra plumbing and such. It's definitely a thing we could do but it's not without it's problems. Also, Hall thrusters don't tile well as they're annular/ring-shape
69.
by archermarks 4y ago
That's what we do! But that's also what we've been doing for 40 years and it's nice to have some theoretical grounding to why stuff works.
70.
by archermarks 4y ago
I'm really not following what you're talking about. What is the phase diagram you're referring to?
71.
by archermarks 4y ago
I mean density in terms of amount of plasma through the device. You can cluster these together too but that gets complex from a systems design perspective. It's something that's being researched though
72.
by archermarks 4y ago
MHD is a specific set of a assumptions you can make to reduce the plasma fluid equations to something more tractable. This includes things like assuming infinite conductivity and combining all of your species into a single "fluid"
73.
by archermarks 4y ago
Yes, thank you. It's a closure problem in the former sense.
74.
by archermarks 4y ago
They could help with improving magnetic confinement on high power density thrusters. Yes, it is. There's a lot of small thruster startups out there. See Orbion, Thrustme, and Applied Ion Systems for examples.
75.
by archermarks 4y ago
VASIMR is a specific type of magnetic nozzle thruster built by Ad Astra and which has never flown. Hall thrusters have been flown since the 70s and 80s and have been rapidly developed since the mid 2000s to fill a variety of niches. Magneti
76.
by archermarks 4y ago
No. Hall thrusters are low temperature plasma devices, and operate in a completely different plasma regime than fusion devices. The ions dont get that fast, only a few tens of thousands of meters/second. The electrons only reach 10-100
77.
by archermarks 4y ago
We build them all the time. The difficulty is measuring the right regions of the plasma with the right precision. The plasma is pretty sensitive to perturbations so you can't always just stick a probe in them. This often restricts us t
78.
by archermarks 4y ago
They're really cool to see running. Often not so dim either.
79.
by archermarks 4y ago
The main constraint is power usage. In principle you want to accelerate your fuel particles as fast as possible. At a fixed electric power though, the faster you accelerate each individual particle, the less particles you can accelerate. Th
80.
by archermarks 4y ago
The "material" in this case is vacuum and plasma. Yes, something small and electromagnetic is affecting the conductivity of the plasma, and we have an idea what it is, but that doesn't mean we know how to simulate it or predi
81.
by archermarks 4y ago
To scale up thrusters you can simply make them bigger, but that leads to a lot of wasted space as the thrust is only produced by a ring-shaped region of the device. To improve thrust density, you can nest these inside each other (see this p
82.
by archermarks 4y ago
Depends on what you mean by order i suppose. The simplest are algebraic (zero-order) models where we prescribe the anomalous transport as an explicit function of other plasma parameters. More complex ones are coupled systems of hyperbolic P
83.
by archermarks 4y ago
Hall thrusters do not involve any form of detonation or condensation. They're run on inert rarified gases. There are ionization instabilities in Hall thrusters for which I suppose you could make an analogy to detonation. Rotating spoke
84.
by archermarks 4y ago
It's pretty unlikely that anomalous transport comes down to quantum fields. The instabilities that probably cause it are complex but are classical in nature.
85.
by archermarks 4y ago
In this case, it's different than lift. We can run CFD simulations of wings and get accurate estimations of lift/drag etc. We cannot do that for Hall thrusters without already having run the thruster, as we need to calibrate the
86.
by archermarks 4y ago
I actually work directly on this problem as part of my PhD. I work in designing simple "closure models" for Hall thruster anomalous transport that can be implemented in simulations to improve how well they match with experiment. I
87.
by archermarks 5y ago
This doesn't have basically anything to do with the linked article. This study suggests that the oldest known Homo Sapiens fossils in Africa are even older than previously thought, which gels with other evidence. Here's the abstra
88.
by archermarks 5y ago
Oh I'm well aware, I work on this stuff, but I'm still curious about their system, and any on-orbit data they might have. We're working on krypton Hall thrusters right now in our lab and trying to characterize the differences
89.
by archermarks 5y ago
This is really cool. Electric propulsion for small satellites is a hot field and has been advancing rapidly, and this is no exception. The rising cost of Xenon is a real problem in the field right now so it's great to see the work bein