Passive shielding

This isn't really the magnet blog, so I'll relay Space Startup News who knows better. He's talking radiation-shields. To replace his overview, here is one from 2025.

What appears to have inspired our boy is Zenno. They announced a few weeks ago they'd loaded Supertorquer on "Starburst-1". The latter is Portal Space, which rideshares Transporter-18. Present plan: Falcon-9 next month. Portal are trying to shift sats between MEO and GEO, which engine they grandiosely term "Supernova".

Zenno's Supertorquer in this, confusingly termed a "flagship", is the actuator for this ship. It's a superconductor: a passive magnet at 3,500 A·m. Contrast, the usual passive shielding of lithium-hydrates which then add to the dry mass. SSN points out that superconductors are now a commodity, made more-or-less cheaply. (This is because of the work done in the fusion field. If those customers go away, as they well might, this application will keep superconductors in business.)

Although the Zenno magnet be passive it must be kept below 100 K or so. The mission is going to use power (by solar), if nothing else for the "TRL11" diagnostics also on board. It is in fact sun-sync so will be in daylight for a full year. Basic thermodynamics will heat up the chassis, and that heat is not going to be blowing propellant all the time. One assumes radiators will be brought.

Portal's aim is to use Earth's magnetic field for control authority. That's the "torque" part, to turn itself about. This leaves, for propellant, only shifting orbits. I imagine it also simplifies the design as the engine(s) shouldn't need gimbals (the solar and radiators get their own torque). In a future when sats might use the spicy-meatball for higher I_sp, any improvement on shifting cargo about is good.

Naturally the torque part works only over planets with dynamo. Such include the four big'uns, plus Mercury and Ganymede-why-not. We gotta start somewhere so, Earth it is.

This mission already-excellent hasn't even got to SSN's stake in it. Zenno want to test how well this magnet, which again is passive so always-on, keeps out the radiation. That can help scale to such human-rated habitats as can't bury themselves under regolith. Thinking here not so much of longterm space-stations outside Van Allen (Jensen imports regolith - and hydrates), as the shuttles to/from those stations or, perhaps, the stations-under-construction. Meanwhile all those LEO stations are likely going to stay lightweight (so micrograv) so will need the shields too. So much for those BVDs!

Cheaper syngas

Syngas is a mix of carbon-monoxide and hydrogen. I expect Martians can get the hydro' from ice; Venerians must scoop the acid clouds. I hadn't really checked how the chem would work, I'll probably ask Copilot. Where carbon and hydrogen can't be had, or they can't just loot an errant comet for its methanol, I've suggested breaking plastics. Waste Not Want Not.

Some planets by contrast are awash in methane. This study, mostly Chinese, proposes an alumina-based catalyst. This is just bauxite sent through the Bayer process (or, hell, pulverised soda cans) and should be cheap. A little pure nickel is added, like 0.8%, which at that concentration can't be expensive either.

Why the Samaritans didn't want our Joshua

Bible-believers as with Jeremiah and others contend, further, with two Joshuas - or, perhaps, four. For the JudaeoChristian community the main two are the MT (> Vulgate and near everyone else) and the Greek (> Old Latin). The Dead Sea is less helpful than you'd think - or hope: it has a MT (with a few variants) and "4Q Joshua a". The latter might be a retelling, like the Samaritans have their own "Joshua"; albeit, here, perhaps based on an earlier Joshua edition. This topic is colossally complex, but it seems not complicate.

Ernst Knauf, generally-respected at this blog, is respected enough on better fora to be allowed there a summary (pdf).

The story (of the story) begins with a Joshua 6 and 9-10. This, per Knauf page 359-60 #1-3, is what arrived in Achaemenid Jerusalem 500-450 BC with chapter 11 as supplement. Also arriving was the Holiness redaction of Leviticus, which got notorious enough that Ezekiel will read it. The Deuteronomic History from 1 Reigns/Samuel 9+ also by-then was extant. This is where Knauf #4 kicks in, assigning the bulk of Joshua 1-21 as the Greeks will know it.

Copilot is telling me that Holiness has infused Joshua chapters 3, 5, and 7 (also 24 but everyone agrees it's late). Knauf doesn't cite what Copilot is citing, nor say much of these earlier chapters at all; but they independently come to the same conclusion that these chapters be postexilic and [Holiness-]priestly. For Knauf, Joshua 1:6-21:45 was entwined with the prior five "Mosaic" books in a Hexateuch.

Recently one Erasmus Gass has posted "The Land Distribution in Joshua 13-19". This stands to fine-tune #4. Trickling through the Temple circles was a census of cities and, also, of Tribes. The Tribes numbered... seven (18:9). These were Judah, Ephraim, Benjamin, Zebulun, Issachar, Asher, Naphtali. Gass can understand the absences of outliers Simeon, Dan, Reuben (and Machir although nobody asked him). He cannot so understand Manasseh's absence. Gass posits that our Joshua 18:1-10a, then lacking MT v. 4 (as Greek lacks it), omitted Manasseh at the time of composition. Manasseh was Samaritan territory. The "document" had excommunicated this tribe.

Now as we all know, the Samaritans came to find all manner of ways to harmonise Numbers with Deuteronomy. So did the Greeks, even unto Joshua 5:6. Gass is arguing the same process for the Jews. This antiSamaritan document now in our Joshua 18 was accreted, with reference to ... Numbers and Deuteronomy. These were never the same book, as the Samaritans knew, so the accretions were done in different stages. First was another "Priestly" (sic) redaction, to enholify the Tribes. Gass thinks Joshua 18 here got repurposed, to introduce 15-17 also 19:1-48. This chunk was to follow Numbers 34:2-12. Gass argues for the same "ideolect" of Hebrew in these pericopae. Copilot, incidentally, is telling me that Numbers 34:2-12 if not quoting Holiness Code shares Holiness ideology. I expect that serving this ideology, Numbers 14:6-9,38 inject Joshua (and Caleb) to that episode of the Scouts.

Then Joshua 15-19 got reassembled, between 14:1-5 and 19:49f as "frame". From here out, I'll let to others. I'll just note that Gass doesn't see Ezekiel as influencing the assemblage or redaction of Joshua in any way.

Overall, I'll note that the Holiness Code was a Jerusalem project and that Joshua 18:1-10a may, indeed, have been structurally antiSamaritan. The Samaritans accepted Numbers 34 on their own terms, with a lot of redaction. They simply refused the Jewish Joshua; incidentally adding some small evidence toward the lateness of this project. Maybe the men of Gerizim could have accepted Joshua 6 and 9-11 (and 1 Samuel 1-8 la-de-da), but the first scroll proffered to them had the accursed chapter 18 therein. Knauf and Gass ponder if the Jews had attempted to soften Joshua for the north. The north chose instead to write their own "Joshua".

Meanwhile the Jews shrugged; they broke their own holy Joshua into its own book, offset from Torah. Thus Joshua 1:1-5 were born. And the stuff which connects Joshua to Judges and beyond, which the Jews were also assembling.

TL cyclers

ToughSF has linked muh cuz S. D. Ross, along with his minion Michael Roberts-Tsoukkas, on prograde Earth-Moon cycler orbits. Prograde means we can inject sats into there more easily.

The key as ever is the Jacobi. First you have to raise that sat. This altitude - potential-energy - is high, in order to shift toward the Moon easily. It also meanwhile has to be kicked to an orbital cycler trajectory.

Once done, a class of TL cyclers opens up. Among them: (1,1) and (2,1) and (3,1). Last is thrice about Tellus here; once, Luna there. 45, 84, 64 days period respectively. The (3,1) cuts closest Earth and Moon; also doesn't skim the direct Earth-Moon line. Former two intersect close to L1, so will need diverted from any spaceline. Third one looks pentagrammy, skating the far edges of L4 and L5 haloes. Ross with Abdullah Braik lately suspect (2,1) as hard-access. (1,1) retains the lowest flight time so prioritises small journeys toward the Moon and back, like Aldrin to/from Mars.

The team might be settling upon (3,2) although this does clip the spaceline.

As for their use, I expect that's for what Mike Collins was doing in 1969, picking up and dropping off, in a safely-shielded capsule. Maybe big enough to be shielded and have spin'grav.

To test, that's standard Falcon-9 injection into orbit followed by space-tuggery; we're doing a lot of similar Lunar orbitals. For the cyclers proper, would require something more. Like the SLS, but I don't really like that. An assemblage in some HEO shipyard would be better.

1/137

I haven't poasted on the Fine Structure Constant, which approximates 1/137. So, let's.

It's a ratio; no units are here. By convention we denote 1/137 by "α", confusingly since we also use that miniscule hellenism for other ratios like thrust/weight, but this one may deserve that pride-of-place. DEEP2 was observing it back in time (meaning: space) and in 2005 revealed that it hadn't changed in seven billion years. To put another way, the laws of physics had not changed in the whole saga of the formation of our solar system, probably from some nebula expelled by supernovae of stars preceding it by maybe millions of years. Inasmuch as creationists had put into question the antiquity of physical laws, this was one of several findings which let the air out of the movement in Dover that year.

This blog is a post 2019 project so hasn't cared to revisit DEEP2. Two decades later, we should consider other findings to suss out the validity of modern physics before all that.

Google AI points to quasar absorption-lines and (naturally) the Cosmic Microwave Background. This has a recent validation here, within 1%; the observable physical laws constrain what scalar dark matter can be, in terms of mass. Like neutrinos have mass but we can measure only the upper bound per particle.

We - not I - should use this paper in discussions with the Catholics of July 2023. Dr Rudolf Hilfer notes Pius XII positing the universe at five billion years ago, holding that to ridicule, which is a mite unfair to that late-1940s bishop, inasmuch as he (prophetically?) marked a time before what we know of our formation, if not DEEP2-before. Hilfer in fact cedes past even DEEP2, to the Cosmic Microwave Background. He (implicitly) allows that the laws of physics apply throughout pretty much everything Milky Way. I counter: before all that, we can at least constrain what went on.

Now, this is not a cosmology blog. Those exist; we can bring Turtle Island and Woit and Triton Station. Which I do against-interest. On one hand I know that Turtle hates me, that Woit counts me as a supporter of a fascist dictator, and that Triton counts me as a racist. On the other hand I know that Dr Hilfer is commanded to love me. And Hilfer can in fact prove that he loves me, by conceding that alternate theories exist against the Λ-CDM consensus. He can even agree that I'm a fascist racist worthy of hate by others, some not even pagans.

Calling Big Bang a "narrative" in the context of terms like "pagan cosmology" implies dishonesty driven by animus. And what do pagans deserve, Herr Doktor...? Let us just say, Hilfer shows his own animus thereby. And if not dishonesty; a certain disingenuosity.

Falcon Heavy + Sunbird: evaluated

Starfire and I assume Sunbird promise high-alpha thrusts, such that they could push their own engines into orbit and beyond. Their problems are twofold: they use expensive helium-3; and their thrust isn't all that high, in the teens of newton. The Merlin series, which the Falcon rockets use, each runs 845 kN at sea level. Falcon 9 therefore must use several rockets - nine Merlins. The Falcon Heavy uses two sets of Falcon 9s and a bigger one in the middle. The US military sometimes uses the latter and buys the discardation of the boosters for extra thrust.

SpaceX has earmarked Falcon Heavy for retirement once the Starship is ready. And when they can do one Starship a week, the whole Falcon series is done. But what if...?

Today I pondered firing the FH triple blast except to swap out the colossal core rocket. Instead we are lifting the fusion rocket. The Falcons on either side can possibly use methalox or even hydrolox for more boost and les soot. These rockets can be retrieved as per usual. Fusion rocket doesn't need as much thrust after those detach - we'll put a button on this.

If hydrolox, I call in the Germans. Their RLV-C5 as boosters are rated 1972 kN. Although not as mighty as the 2700 kN Raptor-3; RLV-C5 uses ten apiece. Both my boosters would, then, glide to pickup allowing more efficiency.

We are here buying horizontality over verticality. These should be safer and cheaper to assemble on the ground. Buys some international goodwill also. As a direct small-load mission, we here RETVRN to Gajeri's 2010 thesis to Saturn or whith'rever other 5+ AU destination.

So: let's run this by Copilot. Even at LEO, the fusion rocket still has to blow out extra fuel and must take many days to get to escape-vel. Layla Mohsen, sorry to pick on her but she's tagged her name to the mission rather than to the engine, assumes a space infrastructure fit to assemble interplanetary manned craft in that LEO and, we must assume, push it outward. I don't know that we have that. Will we have that in 2030? Will any of the proposed stations want to do that?

If our mission is for a light cargo, and if we're assuming orbital infrastructure: a better investment be to hoist that Tamil Tether. The orbital station maintains tether, at most (which scales better than being a direct shipyard). Tether catches our fusion mission and drags it higher. Fusion lights the fuse.

Starfire

Princeton haven't abandoned Sam Cohen's direct-fusion project. All they did was rename it: Starfire. They got new hire Layla Mohsen to deliver the youtube, covering much of what Marco Gajeri's old Turin thesis did (pdf).

The design is for D+³He, output ⁴He and a proton - ionic plasmata. A little secondary happens, where D+D passes a neutron making H+T, or just fuses into He-3... and a neutron. The former tritium can fuse too and give off more neutrons. These secondary reactions are well-studied and deemed nonproblematic for this design (the tritium is exiting the back door in time).

The earlier mission-architecture was for Saturn [UPDATE 1:11 PM for which I have mine own ideas]. Princeton are now promoting a Martian landing and takeoff. I'm going to LARP Zack Moussaoui and not care about any of that. Let's just order them to dock with Deimos or otherwise stick in high Mars orbit.

This design, they say, doesn't have to turn off. If they snap the exhaust-pipe shut, and replace the radiators with a Brayton cycle, they have a modest fusion electrical generator. And yeah, they're getting helium in that exhaust they've bottled; tritium too but this won't be in position to be fusing anymore. Maybe they burn the hydrogens in oxygen (oxygen is common in any planet's regolith). So it's kind of a ⲛⲑⲉⲡ.

Tritium extracted will beta-decay halflife 12.3y. This means electrons. I hear they are low-energy, so low-energy magnets can keep them at bay. Also, the byproduct is He-3 which is half our fuel. That helium is what you'll want to save, for the trip back home.

That assumes they haven't already guzzled all this propellant/fuel to get here. Along with 70% helium of whatever isotope, they want 30% xenon. The xenon must be imported, or added to the manifest; and so must additional helium, because the helium waste isn't nearly the amount they need. Good news is that in high orbit, the video itself assumes supply with nonfragile cargo from all manner of Earth low-speed (Hohmann) runs. This includes canisters of liquid volatiles, solar cells, extra radiators, solid foods. At Mars in perfect daylight, you can also use 43% of the Sun's radiation. You don't even need a fusion reactor.

They have two options for cargo and for crew. The crew might use the onboard rocket to crank it the rest of the way out our well. That would be a high-thrust option which I expect to slash I_sp. They promise 5-10 N/MW powered by 1-10 MW. This may sound like weak newtons, and I warn that many typoes clutter this presentation. This may not be one of them; for 2 MW Sunbird's 2xDFD aims 10 N (up to 101) and here Gajeri had projected 8 N. Gajeri's thrust-to-weight α (you know, the N/N stuff you don't see in I_sp) ran 0.75. This compares with Ebrahimi's wild 2021 VASIMRlike which, of course, drinks its power from outside.

Cargo... might not use this engine at all. That can take a whole year which sounds, basically, chemical.

Specific-impulse blows past any of those dangerous fission NΘP we've seen. One chart has exhaust velocity up to 25000 km/s - which is silly, and should be ignored. Gajeri - aiming to Saturn on a fairly lowthrust vector - expected 9.6ks. Matthew Chu Cheong follows Gajeri in using Rognlien's UEDGE: more like 88 km/s calculating 8.6-9.2ks, about half a Sunbird let alone θ-pinch. That exhaust can rise to 300 km/s. Mohsen also boasts α>1 (prosaically, 0.5-2) which - technically - can get you offa Earth (if we had cheap He-3). The lower I_sp bounds - they claim - deliver in 67 days to Mars which compares well with the fission Shockwave Exhaust (afterburner). Sunbird might not be fit for orbital test in 2027, note.

For Mars, contrast Saturn, needs assemble the whole ship in orbit. Princeton want three "SLS-class" launches. One of these launches would store the Starfire engines (I expect plural, for thrust) each-which is only 2m diameter; the other launches take up whatever cargo is to be delivered, including the propellants. I suspect they can get more launches off of Starships for cheaper. On assembly I see no radioactives on board; but fast exhaust, neutrons, and some tritiums will happen in the exhaust. Not much of a worry in the upper thermosphere which we're sideswiping (toward lower atmo, pretty sure cosmic rays would swamp this) but a worry for all those LEO sats. I'd let them do it maybe 700 km. Absent skyhooks Copilot is saying 3.5-3.7 km/s for delta-V to intercept Mars on Hohmann.

For Mars-system-injection, fun part is that Copilot recommends an elliptic orbit for additional 1.3-1.6 km/s (this may depend on adjusting inclination to equatorial). Thence I can transfer-burn to Deimos 150-250 m/s, that's meters lads. (As noted here, some mission-archies prefer Phobos, but we don't.) 5.3 km/s total would have mass-ratio, by Tsiolkovsky (or Moore, for Brits) and lowball 8000s: 1.07. 7% of my rogget would be propellant. That's like an epstein drive. (And as noted, Earth would be sending supplies, for the trip home.)

Princeton are presently testing the power-source mode. They'd be building the models 2028-35 which I assume includes testing at 700 km (Starship should be online 'round then). Production happens 2035-8 (Princeton's plan includes a large share of the mission, which itself makes Assumptions, on what we'll be able to do in orbit) and then they go to Mars in '40. If we assume Sunbird is on the level, 2028-35 seems like about when they'd be building models as well.