Seriously? Wow, I should add CNC machines to my bland.is (Icelandic craigslist/ebay) search list. I've always thought it'd be great to own one but the price tag for a new system has always been astronomical.
I'm not sure if you watched the new movie, but Fin's whole motivation is freedom from the oppressive regime that kidnapped him, nobody but hard core First Order devotees want them to take over the galaxy, the main antagonist on-screen fights a constant struggle between his dedication to the dark side being thrown off by stiil having feelings for his father, and his father risks his own life to try to get him back.
And apparently you're a fan of the concept of "women as prizes"? Win a battle, get a woman FREE, right? Because women are not independent beings with their own motivations, rather simply rewards to be given out to male protagonists who achieve some objective? Heck, even the original Star Wars lampshaded this concept - Luke "won" in A New Hope and became close to Leia, only to have it later revealed that she's (SPOILER ALERT!) his sister,.
Indeed. It makes one wonder, as Robot Chicken did, whether he's really secretly a Sith master who deliberately sought to gain a position where he could put Palpatine in power and pull Anakin into Palpatine's web, with his slapsticky character designed to throw people off of suspecting him and to be appealing to the young Anakin.
I've not seen a lot of their recent stuff. But I saw tangled and was impressed at how the "bad guy", Rapunzel's stepmother Gothel, is multifaceted, not just some one-dimensional incarnation of Evil(TM) or Greed(TM) or whatnot. She had a legitimate grievance with the kingdom (they killed the flower she'd been carefully using and nurturing for hundreds of years to save their queen), and while she did kidnap Rapunzel as a child, she does seem to genuinely have feelings for her - despite also being dependent on using her as well. Not so much a "wicked stepmother" as a "passive-aggressive stepmother". I really felt Disney had matured in that regard.
Exactly. If they want the stats on their rocket to be comparable to SpaceX's, they need to reduce it to a quarter of its current weight (to match the wet/dry mass ratio of Falcon 9's first stage) and have it reverse about a thousand meters per second of lateral momentum and land without the ability to hover. Because these things are the consequences of SpaceX having to make something that functions as an actual first stage of a launch vehicle, rather than a joy ride for rich people.
There's a couple side effects of this capability that I haven't seen discussed in regards to abort as well.
1) First stage partial failure abort to ground: If there's a non-catastrophic problem on the first stage that will prevent the payload from being injected into the proper orbit (for example, multiple engine failure), there's the potential to abort to ground. Now, this isn't exactly the same - they've still got a rather lot of weight on them (and correspondingly a lot of fuel inside); it'd help if the second stage were able to jettison its propellant (otherwise the nitrogen gas jets and grid fins have to work harder). But it might be possible to re-land the whole rocket, payload and all, so that they can fix it and then re-launch.
2) Second stage hard abort to ground/sea: If there's a catastrophic problem on the first stage but successful separation of the second stage intact, they could try to "land" the second stage and provide partial potential for recovery of the payload. This is more difficult - the second stage has no grid fins, no nitrogen gas thrusters, no landing legs and only one engine. But burned out of propellant it's quite light, it probably has enough thrust, even with the payload attached - and if it just separated from the first stage, it certainly has enough propellant to get back to the pad and line itself up for a gentle, fully vertical descent. The lack of nitrogen gas thrusters would make stability much more difficult, they'd have to land just from gimbaling... but it's probably doable if crosswinds aren't too strong. And they have no landing legs, so they're going to damage the nozzle, and the thing may well fall over. But it's only 1/3rd the length of the first stage, so maybe not, it depends. At sea it'd fall over into water. In short, you could actually get your payload back not at a speed of "500 meters per second smack into the ground", but either "less than 1 meter per second" or "less than 1 meter per second, then a secondary lateral thud at several meters per second followed by the explosion of whatever residual propellant remains" Depending on the payload and how it's stowed, it could potentially be partially or completely reusable.
Color me confused, but if it does on its 10th launch then how are they supposed to store it? Do you mean "store the wreckage"? Rockets aren't like cars that just break down on the side of the road.
1) Recovery is only possible on launches where there's enough capacity left over to compensate for the altitude/velocity of the stage at separation (it's not a simple mass issue, lighter payloads that need more delta-V end up with the first stage moving faster than heavy / low delta-V payloads).
2) In theory, vastly reduced launch prices mean a vastly larger market growing for long periods of time.
3) Rockets don't last forever.
4) Updates to the design provide better safety, capacity, and other features
Concerning #2-4, one should think of the airline industry - airplanes are far more reusable than these rockets will be (if I recall right, SpaceX is targeting a couple dozen uses per rocket), but there's still mass market need for continuous production, for the same reasons.
5) Falcon Heavy upper stages are not recoverable, so that's a merlin and tank per upper stage. If you do actually have said vastly reduced launch prices and said vastly larger market, then you have to make a lot more upper stages.
6) SpaceX would be taking over a large chunk of the world's launch market with those prices, so even if there was no market growth, SpaceX would still grow significantly.
Let's not downplay it, a lot of things have gotten easier with space technology. We have more efficient engines, vastly smaller, faster computers, far superior communications equipment, far superior power generation and storage hardware, and a whole laundry list of things on pretty much every technology front.
That said, the overall picture isn't "orders of magnitude better" today. It's indeed improved, but not by some vast margin, in the big picture. And unfortunately, Mars is a vastly more difficult mission target than the Moon.
... though my personal pet concept (which I'm actually working on an OpenFOAM simulation of right now) is a caseless rocket of a type that doesn't really have a name (although most closely resembles a hybrid). Like the above, it's LOX/Al/paraffin, but the aluminum is thin extruded honeycomb, aka structural. The aluminum is coated by paraffin (also extruded by the same extrusion head), and inside that, filling up each channel, a dense open cell polyurethane foam (optionally with a small amount of fused silica thickener) - also injected at the end of the extrusion head after the paraffin cools. The foam is designed to hold the (optionally thickened) LOX like a sponge, with enough pore space that it can still outgas. So the rocket can be stored and shipped empty (effectively zero fire risk), and then filled with LOX at the last minute before launch.
During combustion, heat of combustion boils off the LOX and burns away the foam - this forms the deepest point of the burn inside each channel. The heat and swirling gases, like in a hybrid, melt the paraffin along the walls, forming a liquid pool and swirling it into droplets which burn in the LOX. The further down you get in the channel the more of the paraffin you've burned off (paraffin has a rather high specific heat and aluminum is a good conductor of heat and IR reflector, so you basically have the aluminum protected until the paraffin is gone). Beyond that you get to exposed aluminum, which quickly heats, erodes, softens, thins, and breaks into droplets which continue combusting out into the exhaust stream. Up until the very end, the aluminum provides containment allowing for high chamber pressure, furthered by the great strength of your propellant itself being an aluminum honeycomb. The droplets burning in the exhaust stream - and then later releasing latent heat of condensation - boost its temperature.
Okay, so that's combustion, but we're kind of missing a key aspect: *a nozzle*. So we start with the throat: it turns out, you don't actually need a throat, a sort of "virtual throat" forms. This costs you some chamber pressure, but since the correlation between chamber pressure and ISP isn't that strong, it only costs you about 1,5% of your ISP - not a big deal. More of a big deal, however, is the expansion nozzle - as your exhaust stream will never move through the "throat"" (virtual or not) faster than its speed of sound. However, there are a variety of "virtual expansion nozzle" designs which don't actually require an outer containment structure. The most famous and efficient of these is the aerospike engine. The simplest is simply having a ring of thrusters around a relatively thruster-devoid center. There's a great deal of variety between these two. And the burning engine itself defines the shape (which can be fixed or changeable as it burns down). So the goal would be to find a design that maximizes performance while minimizing production complexity. For example, a simple straight annular shape would be easiest to extrude (the insides and outsides of the annulus would be extra thick to help resist the internal pressure and to take longer to burn away). With only a little more complexity you could have the annulus spiral and create a central vortex. With yet more complexity you could have exhaust jets angled somewhat in or out. With more complexity you could have non-linear exhaust channels and varying burn rates, even tracking along an aerospike shape if you really wanted. And on and on.
Hence the need for a good CFD simulation.
Hence what I'm working on.:) It's a bit tricky though because I can't just model it as frozen combustion - the aluminum in particular will continue to burn in the exhaust stream, and there's also potential for fuel-rich mixtures to get some additional bonus in-atmosphere from combustion with atmospheric oxygen in the bow shock. Where and how it burns does indeed matter quite a bit. And aluminum combustion isn't nearly as well categorized as hydrocarbon combustion. But the
Hybrid rockets are not new - they're actually very old (some of the early rocket research focused on things like peroxide/bitumen). The problem with them has always been thrust - since the oxidizer isn't integrated into the fuel like with solids, they're much more burn-rate limited. So you have to heavily core them out to make many channels to try to get thrust into something workable, but then you make them unstable and less predictable in burndown.
That said, there is progress being made. The current research suggests that probably the best near-term way to go is LOX with an aluminized fuel of either paraffin wax or polyethylene. You want a hydrogen-rich hydrocarbon which is stable and relatively strong at room temperature but which melts into a very fluid liquid at relatively low temperatures above that and which can be readily blown into a spray of droplets. And like with solids, aluminum adds a lot of heat to the burn and stabilizes combustion against instabilities. Straight polyethylene alone has something like 3-4 times the burn rate of polybutadiene, and aluminum significantly increases it further.
Hardly. Just as an example, performance could be improved by use of a gelled hydrogen containing aluminum powder. Or significantly improved by aluminum-coated lithium powder (or liquid lithium injected as a triprop). Or dramatically improved by that plus FLOX as the oxidizer (although you probably wouldn't want to light that up until you got far enough up). And these are just examples of materials available today that we can use. FLOX/Li/H2 triprop is over 100 sec ISP better than LOX/H2. Not that big of a deal on first stages, but when you're talking half a dozen stages later like for a manned return from Mars....
These are just examples of improvements from propellants, but improvements don't just stop at propellants - there are lots of potential improvements in each aspect of engine design that can be done. SSME was a great leap forward in terms of performance, but it's not the be-all end-all.
Yep, it actually could - although somewhat underpowered versus what you see in the movies due to the limitations of the power source with modern technology, cooling issues, field strength limitations, etc. But the basic technology is already there - just a magnetically constrained plasma cutter with the core (telescoping solenoids) as the electrical return on your circuit. There's no reason it wouldn't work, it's not much different from how we already cut things today. The plasma on plasma cutters doesn't extend to "sabre length", but that's because it diffuses - constrain it in a solenoidal field and it should have no trouble doing so. You'd probably even get the standard random crackling sparks when two "sabres" hit each other (not from shorting between the cores - they're not closing a circuit - but from plasma-leaking to the cores during magnetic reconnection of kinks from the interaction of the two nonaligned fields.)
Sorry, you mentioned CCDev, not COTS. But Commercial Crew is basically COTS phase II, in progress, and there's no reason to think that it's going to fare any worse than COTS.
The model has worked poorly in what regard? SpaceX is actively delivering cargo to ISS for about 40% the per launch cost of ULA (without reuse) and has meet certification to deliver crew. A whole Dragon launch is going to cost NASA about as much as a single seat on Soyuz, and the whole COTS program, yielding two launch vehicles and two automated transfer vehicles cost about the same as a single Shuttle flight. The NASA final report on the program basically goes through every combination of phrases meaning "unqualified success" in the English language in describing the results of the program.
I'm a big believer in this too. Welfare systems are big expensive patchworks, and you can simplify or eliminate vast chunks of them. Think of all of the different things that could be partially or completely subsumed by basic income:
Welfare Social security Unemployment benefits Disability benefits Minimum wage Healthcare support for low-wage earners (US medicaid, for example) Food stamps Parental leave pay Subisidized housing
*... and about 50 other things. Think of all of the overhead in running these programs and all of the headaches for participants and gaps that they can fall through. Think of the burden on private companies for dealing with all of this. The reality is that, for better or for worse, most societies have decided on the principle that we don't want people starving in the streets and tried to set up safety nets - one group at a time - to prevent this from happening.
It's about time we just consolidate it to a single basic payment and get rid of all of these programs and corporate requirements that effectively amount to an inefficient approximation of the same thing. And then most of the debates between the left and right will simplify down to simply whether to increase or decrease that base level of income.
The consolidation process can be simple and relatively painless.
1) Start out by baselining it at near the middle of typical Social Security payments - call it "Social Security for All" if you want. Benefits paid out should be relatively constant from person to person, but include benefits for dependents.
2) Deduct every individual's basic income payment from all other forms of government support. This will effectively eliminate the majority of people from all forms of government subsidy, while not reducing the net benefit for any citizen.
3) For any program in which a person hasn't received benefits from in several years, automatically unenroll them from it. The membership roles on most forms of subsidy will plummet, vastly reducing their overhead - many will become so devoid of enrollees that there will be no point to keeping them around, further reducing overhead. Such benefits programs should be culled automatically when their budget drops to, say, 1% of its pre-basic-income budget.
4) Eliminate minimum wage requirements, and impose a corporate tax that approximates what companies had previously been paying in terms of minimum wage baselines on everyones' salaries, with the expectation that corporations will reduce salaries correspondingly with the tax.
Steps 1-4 should be implemented in one block and be approximately revenue neutral.
5) Step by step, phase out each remaining welfare program, funneling the funds into raising the basic income payments; however...
6) Programs that were specifically "pay-in", and were paid in unevenly (such as Social Security) should ideally instead be "cashed out", so that recipients feel a sense of fairness.
The above should still be relatively "status quo, but with greater efficiency, fairness, and less headaches for everyone"
7) Conservatives should now be expected to begin trying to reduce basic income to lower taxes on the corporations and top income earners, while liberals should now be expected to begin trying to raise basic income at the expense of higher taxes on corporations and top income earners. Basically the same struggle that's always played out, but on greatly simplified terms.
Isn't this something that both liberals and conservatives could support? I mean, liberals, come on, everybody in the country having a safety net? And conservatives, isn't your dream to drown the government in a bathtub? If you want to shrink it down, here's your chance. To both: it's just the status quo, only more efficient and fair. You can then change it from there.
So the womp rats were armed with turbolasers and were shooting him, and some of them were sith lords trying to gun him down in the Empire's most advanced fighter craft? Sorry, but we're specifically told that his success was due to him using the Force. He pulls the exact same thing that Rey does - closing his eyes, reaching some sort of inner peace, opening them and then doing some seemingly miraculous Force-guided action. The whole point of both of these movies is about an untrained but Force-gifted individual learning to make use of their latent abilities for the first time.
And seriously, "massive immediate mastery"? Luke is the only one who had "immediate mastery". Rey reached it incrementally - first being totally dominated mentally by Kylo Ren in the forest, then being somewhat dominated mentally but ultimately learning to shut him out during the interrogation, then failing to give commands to the storm trooper, then succeeding, and ultimately, after losing to Kylo Ren (who only kept her alive because his mission was to bring her to his master), learning how to make use of it during a sabre battle. She was given repeated incremental rounds of practice. And it was anything but "mastery", she was fighting a wounded teenager apprentice who was in so much pain that he had to stop periodically, breathing heavily and hitting is side to control the pain.
And Fin held his own against Kylo Ren? Perhaps you weren't watching the same movie as me. Or perhaps to you "held his own" means "taking more than 15 seconds to be slaughtered by a badly wounded opponent".
Kylo Ren is no master. Far from it, it's a point made many times. He himself talks about it. Snoke talks about it. He makes many screwups, including being so emotionally invested in overcoming his resistance to killing his father that he lets himself get shot in the process. He's no Vader, despite how much he desperately wants to be.
I like the concept that light sabers are nothing more than a plasma sheath over a solid (or, since this is Star Wars, "force field") core, magnetically constrained by a solenoidal field around the core, and with the ability to impart bursts of plasma and/or surges of high-amperage electrical current when there's a short between the plasma and the core (aka it strikes another object - except another corresponding magnetic trap, such as another lightsaber)**. In such a case then it's perfectly reasonable that there would be different power settings or that small details of the target might influence its performance.
** - The only problem with this hypothesis is that there would be a really bright flareout whenever a lightsaber was cutting something substantial, which you don't see. But really that's unavoidable in the real-world - you don't, say, burn through thick steel blast doors without a huge amount of light being given off, that's why people welding and cutting steel need goggles to protect their eyes. Also, we don't know what "blaster" shots are, so it's hard to say why or if they'd be deflected in such a hypothetical lightsabre design - they certainly seem to be subluminal, so they're not just laser beams. But in general the "magnetically constrained plasma cutter" design makes sense. It even makes expanding/retracting the lightsabre easy, as a nested collection of solenoids works out to be a linear motor - it'd automatically telescope when you turned it on, and retract when you reversed the field on alternating elements. And the color would require nothing more than a slow leak of gases from the core that tend to glow with certain colors when ionized, such as for coolant or simply to increase the visibility of the plasma. Really, the main hindrance to making such a thing in the real-world that comes to mind is the vast amounts of power and energy required in such a small device.
Actually, that's a reference to The Force Awakens. Rey mistakenly says "This is the ship that made the Kessel Run in 14 parsecs!", annoying Han who shouts back "12!"
Rather than hiding the oddities/cheesinginess in the original trilogy, the Force Awakens really seemed to embrace them. Gonk makes a reappearance. Chewie's much-maligned crossbow turns out to actually be a good weapon. The Force being used as a deus ex machina to all problems is lampshaded with Fin's response to being called out on the fact that he hadn't at all thought through his rescue plan (Fin: "We'll use the Force!" Han: "The Force doesn't work that way!") Pretty much everything that the original trilogy got called out on, the new movie embraces or lampshades it.
As for the parsec issue - according to Lucas, traveling through hyperspace isn't moving in a straight line, it requires navigation to avoid being thrown offcourse by effects from stars and other obstacles, so the fastest route is generally the shortest, riskiest route. In particular the expanded universe the Kessel system is near the very dangerous Maw black hole cluster, so a short Kessel Run time means those foolhardy enough to take a route skimming close to the cluster.
(We of course have to take for granted that superluminal travel is possible in the Star Wars universe without time dilation effects - it's a fundamental aspect of the canon Star Wars universe; without it, nothing that happens in the Star Wars universe makes any sense)
The Resistance is much smaller than the Rebellion - they don't have a lot (or lot of variety) of craft at their disposal. And in the original trilogy you rarely saw tie fighters maneuvering in atmo at all (ever?), while you did see X-wings doing so.
No, they should give into their hate. Their hatred makes them strong. They should feel it flowing through them... let it guide them. Let it make them powerful.
I've noticed that light sabers do seem to have some sorts of safety features. For example, when a person goes flying through the air out of control, their light saber usually retracts. I don't know whether the canon is that this happens on its own or whether the wielder calls the retraction, but it seems to be a general thing. Also, when a person loses their grip on a light saber (such as when it gets knocked from their hand), it also retracts automatically.
Nobody seems to be really concerned about novices injuring themselves with light sabers... heck, in Ep 4, Obiwan didn't even react when Luke started handling his father's lightsaber with it pointed at his head, or when he turned it on and started swinging it around in a crowded space right next to him without any sort of training.
But she makes more progress in half a movie (and years less time in the story) than Luke
You mean, when Luke, whose previous dogfighting experience was shooting womp rats, evaded turbolasers down a long trench pursued by a mature Sith lord and destroyed the death star by nailing a tiny target without his targeting computer on?
Versus when Rey nearly lost to a badly wounded teenage sith apprentice?
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Seriously? Wow, I should add CNC machines to my bland.is (Icelandic craigslist/ebay) search list. I've always thought it'd be great to own one but the price tag for a new system has always been astronomical.
I'm not sure if you watched the new movie, but Fin's whole motivation is freedom from the oppressive regime that kidnapped him, nobody but hard core First Order devotees want them to take over the galaxy, the main antagonist on-screen fights a constant struggle between his dedication to the dark side being thrown off by stiil having feelings for his father, and his father risks his own life to try to get him back.
And apparently you're a fan of the concept of "women as prizes"? Win a battle, get a woman FREE, right? Because women are not independent beings with their own motivations, rather simply rewards to be given out to male protagonists who achieve some objective? Heck, even the original Star Wars lampshaded this concept - Luke "won" in A New Hope and became close to Leia, only to have it later revealed that she's (SPOILER ALERT!) his sister,.
Indeed. It makes one wonder, as Robot Chicken did, whether he's really secretly a Sith master who deliberately sought to gain a position where he could put Palpatine in power and pull Anakin into Palpatine's web, with his slapsticky character designed to throw people off of suspecting him and to be appealing to the young Anakin.
I've not seen a lot of their recent stuff. But I saw tangled and was impressed at how the "bad guy", Rapunzel's stepmother Gothel, is multifaceted, not just some one-dimensional incarnation of Evil(TM) or Greed(TM) or whatnot. She had a legitimate grievance with the kingdom (they killed the flower she'd been carefully using and nurturing for hundreds of years to save their queen), and while she did kidnap Rapunzel as a child, she does seem to genuinely have feelings for her - despite also being dependent on using her as well. Not so much a "wicked stepmother" as a "passive-aggressive stepmother". I really felt Disney had matured in that regard.
Exactly. If they want the stats on their rocket to be comparable to SpaceX's, they need to reduce it to a quarter of its current weight (to match the wet/dry mass ratio of Falcon 9's first stage) and have it reverse about a thousand meters per second of lateral momentum and land without the ability to hover. Because these things are the consequences of SpaceX having to make something that functions as an actual first stage of a launch vehicle, rather than a joy ride for rich people.
Good luck with that, BO.
There's a couple side effects of this capability that I haven't seen discussed in regards to abort as well.
1) First stage partial failure abort to ground: If there's a non-catastrophic problem on the first stage that will prevent the payload from being injected into the proper orbit (for example, multiple engine failure), there's the potential to abort to ground. Now, this isn't exactly the same - they've still got a rather lot of weight on them (and correspondingly a lot of fuel inside); it'd help if the second stage were able to jettison its propellant (otherwise the nitrogen gas jets and grid fins have to work harder). But it might be possible to re-land the whole rocket, payload and all, so that they can fix it and then re-launch.
2) Second stage hard abort to ground/sea: If there's a catastrophic problem on the first stage but successful separation of the second stage intact, they could try to "land" the second stage and provide partial potential for recovery of the payload. This is more difficult - the second stage has no grid fins, no nitrogen gas thrusters, no landing legs and only one engine. But burned out of propellant it's quite light, it probably has enough thrust, even with the payload attached - and if it just separated from the first stage, it certainly has enough propellant to get back to the pad and line itself up for a gentle, fully vertical descent. The lack of nitrogen gas thrusters would make stability much more difficult, they'd have to land just from gimbaling... but it's probably doable if crosswinds aren't too strong. And they have no landing legs, so they're going to damage the nozzle, and the thing may well fall over. But it's only 1/3rd the length of the first stage, so maybe not, it depends. At sea it'd fall over into water. In short, you could actually get your payload back not at a speed of "500 meters per second smack into the ground", but either "less than 1 meter per second" or "less than 1 meter per second, then a secondary lateral thud at several meters per second followed by the explosion of whatever residual propellant remains" Depending on the payload and how it's stowed, it could potentially be partially or completely reusable.
Color me confused, but if it does on its 10th launch then how are they supposed to store it? Do you mean "store the wreckage"? Rockets aren't like cars that just break down on the side of the road.
Not really, for a number of reasons.
1) Recovery is only possible on launches where there's enough capacity left over to compensate for the altitude/velocity of the stage at separation (it's not a simple mass issue, lighter payloads that need more delta-V end up with the first stage moving faster than heavy / low delta-V payloads).
2) In theory, vastly reduced launch prices mean a vastly larger market growing for long periods of time.
3) Rockets don't last forever.
4) Updates to the design provide better safety, capacity, and other features
Concerning #2-4, one should think of the airline industry - airplanes are far more reusable than these rockets will be (if I recall right, SpaceX is targeting a couple dozen uses per rocket), but there's still mass market need for continuous production, for the same reasons.
5) Falcon Heavy upper stages are not recoverable, so that's a merlin and tank per upper stage. If you do actually have said vastly reduced launch prices and said vastly larger market, then you have to make a lot more upper stages.
6) SpaceX would be taking over a large chunk of the world's launch market with those prices, so even if there was no market growth, SpaceX would still grow significantly.
Let's not downplay it, a lot of things have gotten easier with space technology. We have more efficient engines, vastly smaller, faster computers, far superior communications equipment, far superior power generation and storage hardware, and a whole laundry list of things on pretty much every technology front.
That said, the overall picture isn't "orders of magnitude better" today. It's indeed improved, but not by some vast margin, in the big picture. And unfortunately, Mars is a vastly more difficult mission target than the Moon.
I'd call it about a draw.
... though my personal pet concept (which I'm actually working on an OpenFOAM simulation of right now) is a caseless rocket of a type that doesn't really have a name (although most closely resembles a hybrid). Like the above, it's LOX/Al/paraffin, but the aluminum is thin extruded honeycomb, aka structural. The aluminum is coated by paraffin (also extruded by the same extrusion head), and inside that, filling up each channel, a dense open cell polyurethane foam (optionally with a small amount of fused silica thickener) - also injected at the end of the extrusion head after the paraffin cools. The foam is designed to hold the (optionally thickened) LOX like a sponge, with enough pore space that it can still outgas. So the rocket can be stored and shipped empty (effectively zero fire risk), and then filled with LOX at the last minute before launch.
During combustion, heat of combustion boils off the LOX and burns away the foam - this forms the deepest point of the burn inside each channel. The heat and swirling gases, like in a hybrid, melt the paraffin along the walls, forming a liquid pool and swirling it into droplets which burn in the LOX. The further down you get in the channel the more of the paraffin you've burned off (paraffin has a rather high specific heat and aluminum is a good conductor of heat and IR reflector, so you basically have the aluminum protected until the paraffin is gone). Beyond that you get to exposed aluminum, which quickly heats, erodes, softens, thins, and breaks into droplets which continue combusting out into the exhaust stream. Up until the very end, the aluminum provides containment allowing for high chamber pressure, furthered by the great strength of your propellant itself being an aluminum honeycomb. The droplets burning in the exhaust stream - and then later releasing latent heat of condensation - boost its temperature.
Okay, so that's combustion, but we're kind of missing a key aspect: *a nozzle*. So we start with the throat: it turns out, you don't actually need a throat, a sort of "virtual throat" forms. This costs you some chamber pressure, but since the correlation between chamber pressure and ISP isn't that strong, it only costs you about 1,5% of your ISP - not a big deal. More of a big deal, however, is the expansion nozzle - as your exhaust stream will never move through the "throat"" (virtual or not) faster than its speed of sound. However, there are a variety of "virtual expansion nozzle" designs which don't actually require an outer containment structure. The most famous and efficient of these is the aerospike engine. The simplest is simply having a ring of thrusters around a relatively thruster-devoid center. There's a great deal of variety between these two. And the burning engine itself defines the shape (which can be fixed or changeable as it burns down). So the goal would be to find a design that maximizes performance while minimizing production complexity. For example, a simple straight annular shape would be easiest to extrude (the insides and outsides of the annulus would be extra thick to help resist the internal pressure and to take longer to burn away). With only a little more complexity you could have the annulus spiral and create a central vortex. With yet more complexity you could have exhaust jets angled somewhat in or out. With more complexity you could have non-linear exhaust channels and varying burn rates, even tracking along an aerospike shape if you really wanted. And on and on.
Hence the need for a good CFD simulation.
Hence what I'm working on. :) It's a bit tricky though because I can't just model it as frozen combustion - the aluminum in particular will continue to burn in the exhaust stream, and there's also potential for fuel-rich mixtures to get some additional bonus in-atmosphere from combustion with atmospheric oxygen in the bow shock. Where and how it burns does indeed matter quite a bit. And aluminum combustion isn't nearly as well categorized as hydrocarbon combustion. But the
Hybrid rockets are not new - they're actually very old (some of the early rocket research focused on things like peroxide/bitumen). The problem with them has always been thrust - since the oxidizer isn't integrated into the fuel like with solids, they're much more burn-rate limited. So you have to heavily core them out to make many channels to try to get thrust into something workable, but then you make them unstable and less predictable in burndown.
That said, there is progress being made. The current research suggests that probably the best near-term way to go is LOX with an aluminized fuel of either paraffin wax or polyethylene. You want a hydrogen-rich hydrocarbon which is stable and relatively strong at room temperature but which melts into a very fluid liquid at relatively low temperatures above that and which can be readily blown into a spray of droplets. And like with solids, aluminum adds a lot of heat to the burn and stabilizes combustion against instabilities. Straight polyethylene alone has something like 3-4 times the burn rate of polybutadiene, and aluminum significantly increases it further.
Hardly. Just as an example, performance could be improved by use of a gelled hydrogen containing aluminum powder. Or significantly improved by aluminum-coated lithium powder (or liquid lithium injected as a triprop). Or dramatically improved by that plus FLOX as the oxidizer (although you probably wouldn't want to light that up until you got far enough up). And these are just examples of materials available today that we can use. FLOX/Li/H2 triprop is over 100 sec ISP better than LOX/H2. Not that big of a deal on first stages, but when you're talking half a dozen stages later like for a manned return from Mars....
These are just examples of improvements from propellants, but improvements don't just stop at propellants - there are lots of potential improvements in each aspect of engine design that can be done. SSME was a great leap forward in terms of performance, but it's not the be-all end-all.
Yep, it actually could - although somewhat underpowered versus what you see in the movies due to the limitations of the power source with modern technology, cooling issues, field strength limitations, etc. But the basic technology is already there - just a magnetically constrained plasma cutter with the core (telescoping solenoids) as the electrical return on your circuit. There's no reason it wouldn't work, it's not much different from how we already cut things today. The plasma on plasma cutters doesn't extend to "sabre length", but that's because it diffuses - constrain it in a solenoidal field and it should have no trouble doing so. You'd probably even get the standard random crackling sparks when two "sabres" hit each other (not from shorting between the cores - they're not closing a circuit - but from plasma-leaking to the cores during magnetic reconnection of kinks from the interaction of the two nonaligned fields.)
Sorry, you mentioned CCDev, not COTS. But Commercial Crew is basically COTS phase II, in progress, and there's no reason to think that it's going to fare any worse than COTS.
The model has worked poorly in what regard? SpaceX is actively delivering cargo to ISS for about 40% the per launch cost of ULA (without reuse) and has meet certification to deliver crew. A whole Dragon launch is going to cost NASA about as much as a single seat on Soyuz, and the whole COTS program, yielding two launch vehicles and two automated transfer vehicles cost about the same as a single Shuttle flight. The NASA final report on the program basically goes through every combination of phrases meaning "unqualified success" in the English language in describing the results of the program.
Good... good...
I'm a big believer in this too. Welfare systems are big expensive patchworks, and you can simplify or eliminate vast chunks of them. Think of all of the different things that could be partially or completely subsumed by basic income:
Welfare
Social security
Unemployment benefits
Disability benefits
Minimum wage
Healthcare support for low-wage earners (US medicaid, for example)
Food stamps
Parental leave pay
Subisidized housing
* ... and about 50 other things. Think of all of the overhead in running these programs and all of the headaches for participants and gaps that they can fall through. Think of the burden on private companies for dealing with all of this. The reality is that, for better or for worse, most societies have decided on the principle that we don't want people starving in the streets and tried to set up safety nets - one group at a time - to prevent this from happening.
It's about time we just consolidate it to a single basic payment and get rid of all of these programs and corporate requirements that effectively amount to an inefficient approximation of the same thing. And then most of the debates between the left and right will simplify down to simply whether to increase or decrease that base level of income.
The consolidation process can be simple and relatively painless.
1) Start out by baselining it at near the middle of typical Social Security payments - call it "Social Security for All" if you want. Benefits paid out should be relatively constant from person to person, but include benefits for dependents.
2) Deduct every individual's basic income payment from all other forms of government support. This will effectively eliminate the majority of people from all forms of government subsidy, while not reducing the net benefit for any citizen.
3) For any program in which a person hasn't received benefits from in several years, automatically unenroll them from it. The membership roles on most forms of subsidy will plummet, vastly reducing their overhead - many will become so devoid of enrollees that there will be no point to keeping them around, further reducing overhead. Such benefits programs should be culled automatically when their budget drops to, say, 1% of its pre-basic-income budget.
4) Eliminate minimum wage requirements, and impose a corporate tax that approximates what companies had previously been paying in terms of minimum wage baselines on everyones' salaries, with the expectation that corporations will reduce salaries correspondingly with the tax.
Steps 1-4 should be implemented in one block and be approximately revenue neutral.
5) Step by step, phase out each remaining welfare program, funneling the funds into raising the basic income payments; however...
6) Programs that were specifically "pay-in", and were paid in unevenly (such as Social Security) should ideally instead be "cashed out", so that recipients feel a sense of fairness.
The above should still be relatively "status quo, but with greater efficiency, fairness, and less headaches for everyone"
7) Conservatives should now be expected to begin trying to reduce basic income to lower taxes on the corporations and top income earners, while liberals should now be expected to begin trying to raise basic income at the expense of higher taxes on corporations and top income earners. Basically the same struggle that's always played out, but on greatly simplified terms.
Isn't this something that both liberals and conservatives could support? I mean, liberals, come on, everybody in the country having a safety net? And conservatives, isn't your dream to drown the government in a bathtub? If you want to shrink it down, here's your chance. To both: it's just the status quo, only more efficient and fair. You can then change it from there.
So the womp rats were armed with turbolasers and were shooting him, and some of them were sith lords trying to gun him down in the Empire's most advanced fighter craft? Sorry, but we're specifically told that his success was due to him using the Force. He pulls the exact same thing that Rey does - closing his eyes, reaching some sort of inner peace, opening them and then doing some seemingly miraculous Force-guided action. The whole point of both of these movies is about an untrained but Force-gifted individual learning to make use of their latent abilities for the first time.
And seriously, "massive immediate mastery"? Luke is the only one who had "immediate mastery". Rey reached it incrementally - first being totally dominated mentally by Kylo Ren in the forest, then being somewhat dominated mentally but ultimately learning to shut him out during the interrogation, then failing to give commands to the storm trooper, then succeeding, and ultimately, after losing to Kylo Ren (who only kept her alive because his mission was to bring her to his master), learning how to make use of it during a sabre battle. She was given repeated incremental rounds of practice. And it was anything but "mastery", she was fighting a wounded teenager apprentice who was in so much pain that he had to stop periodically, breathing heavily and hitting is side to control the pain.
And Fin held his own against Kylo Ren? Perhaps you weren't watching the same movie as me. Or perhaps to you "held his own" means "taking more than 15 seconds to be slaughtered by a badly wounded opponent".
Kylo Ren is no master. Far from it, it's a point made many times. He himself talks about it. Snoke talks about it. He makes many screwups, including being so emotionally invested in overcoming his resistance to killing his father that he lets himself get shot in the process. He's no Vader, despite how much he desperately wants to be.
I like the concept that light sabers are nothing more than a plasma sheath over a solid (or, since this is Star Wars, "force field") core, magnetically constrained by a solenoidal field around the core, and with the ability to impart bursts of plasma and/or surges of high-amperage electrical current when there's a short between the plasma and the core (aka it strikes another object - except another corresponding magnetic trap, such as another lightsaber)**. In such a case then it's perfectly reasonable that there would be different power settings or that small details of the target might influence its performance.
** - The only problem with this hypothesis is that there would be a really bright flareout whenever a lightsaber was cutting something substantial, which you don't see. But really that's unavoidable in the real-world - you don't, say, burn through thick steel blast doors without a huge amount of light being given off, that's why people welding and cutting steel need goggles to protect their eyes. Also, we don't know what "blaster" shots are, so it's hard to say why or if they'd be deflected in such a hypothetical lightsabre design - they certainly seem to be subluminal, so they're not just laser beams. But in general the "magnetically constrained plasma cutter" design makes sense. It even makes expanding/retracting the lightsabre easy, as a nested collection of solenoids works out to be a linear motor - it'd automatically telescope when you turned it on, and retract when you reversed the field on alternating elements. And the color would require nothing more than a slow leak of gases from the core that tend to glow with certain colors when ionized, such as for coolant or simply to increase the visibility of the plasma. Really, the main hindrance to making such a thing in the real-world that comes to mind is the vast amounts of power and energy required in such a small device.
Actually, that's a reference to The Force Awakens. Rey mistakenly says "This is the ship that made the Kessel Run in 14 parsecs!", annoying Han who shouts back "12!"
Rather than hiding the oddities/cheesinginess in the original trilogy, the Force Awakens really seemed to embrace them. Gonk makes a reappearance. Chewie's much-maligned crossbow turns out to actually be a good weapon. The Force being used as a deus ex machina to all problems is lampshaded with Fin's response to being called out on the fact that he hadn't at all thought through his rescue plan (Fin: "We'll use the Force!" Han: "The Force doesn't work that way!") Pretty much everything that the original trilogy got called out on, the new movie embraces or lampshades it.
As for the parsec issue - according to Lucas, traveling through hyperspace isn't moving in a straight line, it requires navigation to avoid being thrown offcourse by effects from stars and other obstacles, so the fastest route is generally the shortest, riskiest route. In particular the expanded universe the Kessel system is near the very dangerous Maw black hole cluster, so a short Kessel Run time means those foolhardy enough to take a route skimming close to the cluster.
(We of course have to take for granted that superluminal travel is possible in the Star Wars universe without time dilation effects - it's a fundamental aspect of the canon Star Wars universe; without it, nothing that happens in the Star Wars universe makes any sense)
The Resistance is much smaller than the Rebellion - they don't have a lot (or lot of variety) of craft at their disposal. And in the original trilogy you rarely saw tie fighters maneuvering in atmo at all (ever?), while you did see X-wings doing so.
No, they should give into their hate. Their hatred makes them strong. They should feel it flowing through them... let it guide them. Let it make them powerful.
I've noticed that light sabers do seem to have some sorts of safety features. For example, when a person goes flying through the air out of control, their light saber usually retracts. I don't know whether the canon is that this happens on its own or whether the wielder calls the retraction, but it seems to be a general thing. Also, when a person loses their grip on a light saber (such as when it gets knocked from their hand), it also retracts automatically.
Nobody seems to be really concerned about novices injuring themselves with light sabers... heck, in Ep 4, Obiwan didn't even react when Luke started handling his father's lightsaber with it pointed at his head, or when he turned it on and started swinging it around in a crowded space right next to him without any sort of training.
You mean, when Luke, whose previous dogfighting experience was shooting womp rats, evaded turbolasers down a long trench pursued by a mature Sith lord and destroyed the death star by nailing a tiny target without his targeting computer on?
Versus when Rey nearly lost to a badly wounded teenage sith apprentice?
Um, said stormtrooper lost every lightsaber battle he entered into.