Its probably possible to capture some of the energy via MHD generators, essentially if you imagine a cylindrical magnet/spacecraft any charge-exchanged particles that pass through the middle magnets can be converted. The intercepted particles outside of the magnet are just captured (drag only). When we did a back of the envelope it was much easier to just use off-the-shelf batteries rather than cryogenic superconductors. Now, if someone works up an efficient, non-superconductor MHD generator . . . .
Quote from: IRobot on 05/14/2016 06:14 pmQuote from: jongoff on 05/14/2016 04:47 pm The other option that seems to make sense to me is some sort of combustion or fuel cell APU if you have chemical propellants on-board.Mercedes Diesel engine? I was thinking more along the lines of the GOX/GH2 piston engine APU that ULA is doing for IVF.~Jon
Quote from: jongoff on 05/14/2016 04:47 pm The other option that seems to make sense to me is some sort of combustion or fuel cell APU if you have chemical propellants on-board.Mercedes Diesel engine?
The other option that seems to make sense to me is some sort of combustion or fuel cell APU if you have chemical propellants on-board.
Quote from: jongoff on 05/14/2016 08:01 pmQuote from: IRobot on 05/14/2016 06:14 pmQuote from: jongoff on 05/14/2016 04:47 pm The other option that seems to make sense to me is some sort of combustion or fuel cell APU if you have chemical propellants on-board.Mercedes Diesel engine? I was thinking more along the lines of the GOX/GH2 piston engine APU that ULA is doing for IVF.~JonIf you're carrying that much cryogenic liquid, couldn't you just use it to chill down superconductors instead just before entry interface? Cheers, Martin
So because this technology works with plasma, it's best for thin upper-atmospheric conditions. Could it ever be suitable for upper stage recovery? Like, for example, could this tech somehow be refitted onto the upper stage of F9R, to help it "fly" back for a hoverslam? Could it even help lower stage for RTLS? Musk has previously said that he views flying as simply a matter of achieving particular L/D numbers, regardless of how they are achieved. So would magnetoshell be able to achieve the required L/D to assist reusability/recovery?Is magnetoshell being investigated for Mars EDL, since Mars has that taller and much thinner atmosphere? If the magnetoshell approach was used for Mars EDL, would it be able to significantly reduce your retropropulsion requirements, and by how much? In what ways could this translate into improvements for the MCT/BFS?
One thing to keep in mind (also discussed up-thread) is that it isn't clear yet if MAC can provide useful lift. Which means worst, case you may have to assume a ballistic flight profile (albeit a ballistic flight profile with a very low and actively controllable ballistic coefficient).~Jon
Quote from: jongoff on 05/16/2016 09:19 pmOne thing to keep in mind (also discussed up-thread) is that it isn't clear yet if MAC can provide useful lift. Which means worst, case you may have to assume a ballistic flight profile (albeit a ballistic flight profile with a very low and actively controllable ballistic coefficient).~JonSo you guys were saying that Magnetoshell seems to behave like a volumetric parachute only, and perhaps doesn't provide deflection necessary for lift.But magnetic fields can deflect things, bending the charged particles along their field lines. Why isn't that useful deflection? It's just a matter of shape. (Also, why do you only want to exploit magnetism, as compared to overall Lorentz force?)Just as an airfoil with the correct shape can re-direct the force of an oncoming flowstream in an orthogonal direction to provide lift, likewise magnetic field lines should also be able to deflect the plasma flow orthogonally, if the field lines have the right shape. Sure, the coupling between the plasma and a magnetic field is weaker and thus it's not an immediate/abrupt deflection like with a solid airfoil surface, but you've got that large volume to buffer/accumulate your interaction anyway.The analogy to your "Volumetric Parachute" would be the "Volumetric Airfoil".Seems like you should want to focus on getting the magnetic field lines into the correct contour shape, to effectively do what an airfoil does and provide the lift. And you'd want your field to be acting on a large enough volume to provide enough buffer for interaction because of the weaker coupling.The volumetric-parachute/pure-drag thing sounds like the basic simple case scenario, and then the lifting-airfoil thing would be the more custom-contoured case.
How does this stuff get tested anyway - in wind tunnels?
And if Magnetoshell is useful for EDL, couldn't it also provide at least a small benefit during ascent as well?
[caveat: Dave's the expert, I'm just a semi-educated fan, but I'll try to give an answer based on my best understanding.]It's more complicated than that. You start with a neutral particle that's nearly at rest relative to the fast moving spacecraft. Once it charge exchanges with an ion in the magnetized plasma, it's now a charged particle at rest relative to moving magnetic field lines, which then cause the charged particle to start spiraling around the field lines in a direction driven by Lorentz Forces. The problem is that after a short period this newly ionized particle will end up charge exchanging with another atmospheric neutral, resulting it in it being neutralized and then flying off in whatever direction it was going in, at whatever velocity it had picked up by that point. The timing of when it has its next collision depends on how dense the atmosphere is and how fast the spacecraft is moving, and the timing has a distribution to it, it's not a precise thing. To make things more complicated once it's been neutralized by that first charge exchange collision, it has the chance of being collided with again before it leaves the magnetized plasma volume. In fact for large MAC volumes, you might very well have a single particle ionized and reneutralized several times between when it first enters the volume and when it finally leaves. In the end, the momentum transfer is going to depend on the final velocity and direction of the particles as they leave the plasma volume relative to when they entered it. Is there some way to shape the magnetic field such that more particles emit in some off-track direction? Possibly. But it's a really, really non-trivially complex problem to model, since you're talking about interactions of huge numbers of particles. Unless I'm missing something.
Mostly in vacuum chambers--we're talking hypersonic flow regimes that tend to be really hard to mimic in a wind-tunnel. Dave hinted above at his super-hypersonic tests they're looking at doing in this Phase II.
QuoteAnd if Magnetoshell is useful for EDL, couldn't it also provide at least a small benefit during ascent as well?Huh? How?~Jon
Quote from: jongoff on 05/17/2016 05:23 pmQuoteQuoteAnd if Magnetoshell is useful for EDL, couldn't it also provide at least a small benefit during ascent as well?Huh? How?~JonHow about when you're ascending through the upper atmosphere? Maybe it would be better for a scramjet traveling at high Mach for prolonged period.
QuoteQuoteAnd if Magnetoshell is useful for EDL, couldn't it also provide at least a small benefit during ascent as well?Huh? How?~JonHow about when you're ascending through the upper atmosphere? Maybe it would be better for a scramjet traveling at high Mach for prolonged period.
I think that you misunderstand the purpose of the Magnetoshell. it INCREASES drag to slow down and protect the craft using it. Unfortunately, this means that it would likely increase drag for any craft trying to use it to go hypersonic.
Quote from: JasonAW3 on 05/17/2016 06:57 pmI think that you misunderstand the purpose of the Magnetoshell. it INCREASES drag to slow down and protect the craft using it. Unfortunately, this means that it would likely increase drag for any craft trying to use it to go hypersonic.Well, I get that it produces drag - it's meant for reentry deceleration in upper atmosphere - but I thought it could be used for steering as well.But, gee, I wonder how much it could radically improve MCT? Maybe MCT wouldn't have to be as fat, like some are saying it will be, since a magnetoshell could provide instant virtual ''fatness" or drag on demand.
That might be an option, but as Boeing owns the patent, I seriously doubt that SpaceX would use it or be allowed to use it.
Well, I get that it produces drag - it's meant for reentry deceleration in upper atmosphere - but I thought it could be used for steering as well.
Ouch - that's too bad - that's like patenting the tokamak or the parachute
So that kind of sounds like "mean free path" - how long you typically go without bumping into something.Since it's a "control volume" rather than a "control surface", I guess you can't really talk about a "boundary layer" for flow separation, but surely there are certain geometries (cusps?) that would be more conducive to throwing off the particles in particular directions, ejecting/expelling them from the field.
Cool - when does Phase II happen?
Somebody should bring this idea to Elon Musk, because it sounds like it would be great for his MCT. Imagine if they spend all that time and effort developing MCT, and then this Magnetoshell thing comes out soon afterwards, and shows huge performance advantages they missed at on.
Quote from: sanman on 05/17/2016 07:08 pmQuote from: JasonAW3 on 05/17/2016 06:57 pmI think that you misunderstand the purpose of the Magnetoshell. it INCREASES drag to slow down and protect the craft using it. Unfortunately, this means that it would likely increase drag for any craft trying to use it to go hypersonic.Well, I get that it produces drag - it's meant for reentry deceleration in upper atmosphere - but I thought it could be used for steering as well.But, gee, I wonder how much it could radically improve MCT? Maybe MCT wouldn't have to be as fat, like some are saying it will be, since a magnetoshell could provide instant virtual ''fatness" or drag on demand.That might be an option, but as Boeing owns the patent, I seriously doubt that SpaceX would use it or be allowed to use it.