T-FINER, the alpha dog

The starfire / sunbird engines fuse elements to make helium propellant. You know what also emits helium plasma: α-decay. In 2024, quite the year for deep-space rocket ideas, Loura Hall posted how to do it. A yuuge wall poster of its powerpoint can be downloaded (pdf); the project released an update last year.

Thin Film Isotope Nuclear Engine Rocket. But not TFI-Ner[va], oddly, they prefer T-FINER.

This is a sail of (foully) radioactive metal, maybe 36 m². This sail provides its own propulsion, backward. Alpha particles, which are helium-4 ions, blast away up to 0.05c. That calculates to specific-impulse you... you might not even believe if I told you; in the millions (refer to PDF). Mass-ratio would be the mass of the radioactive metal (+ cargo) over the mass of the waste (+ cargo). This ratio would decline by half-life of the element, rather than the rate of burn.

The structure would be to drag the cargo behind. The sail is thin, like 20-50 μm for Thorium-228.

I didn't do the delta-V maths, but NIAC has, and they say they can get 100 km/s. That's a ticket to anywhere in the Solar System. ²²⁸Th (1.9 years) might get us to the 550 AU solar-lens in 25 years. Cf-254 is advertised as 300 AU in one year! (After which, they can maybe flip-and-drag, to 550 AU.) Outside that, this system will stall out so it's not a serious Centauri candidate.

Launching rolls of thin sheets of radioactive sail from Earth is less a problem, I suspect, than making it all in the first place. Alpha-emitters are neutron-deficient and trend heavy. Those meatballs we can spice in space are the opposite. The consortium is talking about skimming reactors or making in cyclotrons (e.g. Ac-227... and Ra-228). That's done on Earth.

Initial thrust remains a problem, unless we just use this to putt around various Earth orbits. One option is to bring layers of this stuff.

Cargo will have to be low-mass; they aim for 8.2 kg. I don't see a comm relay onboard. So I don't know how well it can beam data from Sedna or wherever. This would compete with the sunsail. Because there isn't 'nuff sun out there and, better, the vessel can be steered.

Meanwhile they hope for demo missions. Uranus, with Ra-228, to launch 2034. If someone else sends a full relay to orbit that planet, T-FINER will demand less comms.

Going bananas

Kalium-40 famously has one too many neutrons, β-decaying to argon-40. Not quite radioactive enough to give you argon burps; so it comes up from the mantle with normal potassium in eruptions. How radioactive, is the trick; if it's too long, as with bismuth-209 (2.01×10¹⁹ years) the halflife gets imprecise.

Pumice is telling us more-exactly how radioactive is ⁴⁰K: from Vesuvius. This is done in tandem with recent work verifying the Plinian Eruption against the first months of Titus' imperium.

The latest coins in situ predate 24 June AD 79. I guess the Romans wanted to wait a bit in case someone assassinated the likely heir. It turned out his bro Domitianus liked the guy, better than he liked anyone else in Latium anyway. I don't know any coins got minted in Campania for a year or so after the eruption; Roman coins after 8 September get the "IMP XV" sigil, the fifteenth acclamation of their new imprah. Also "P P", pater-patriae.

The town with the pumice in question was Oplontis. With the assumption of a July-August eruption - Pliny says 24 August - the halflife is narrowed. 1.2044×10¹⁰ years, twelve billion. Give/take 88 million.

Which they then overlay back on the eruption for 1,938 ±13 years before 2025. Which is AD 87. So uh. I guess they added these calcs to some others to get the halflife. The precision is still not what we'd prefer, but ¹⁴C is also a pest.

A spirit-haunted church

It's October! And a new year on Mars...

The position of Orthodox Christianity, in history, has held that natural processes and the movements of the planets are driven by angels. In the past few hundred years, scientists - with mathematicians' help - have dispossessed most of our universe. Some questions remain, yes. But increasingly beyond the purview of, say, the accretion of our Milky Way galaxy.

Modern Orthodoxy seems to be arguing that, yeah, we were a bunch of superstitious ignorants up to Epiphanius and John Damascene. But you can totally follow us when we do necromancies!!

Unlike the veneration for the angel of planet Malacandra, or maybe for the angel who is that planet; necromancy is contradictory in the Bible. On the one hand it's forbidden. On the other hand, as Alex Sorin points out, you can call upon the Sancti for intercession; and the saints are not restricted to the angelic movers of wind and planet, but include also (certain of) the dead. Somewhere in between: king Saul, then barred from asking intercession himself, once called upon a woman in Endor who might bring up a saint on his behalf. That differs from a sinner begging a nun at Agnes' convent to pray for him because... because.

Catacombs and tombs tend to survive the ages and, indeed, Christians could be found down there doing veneration - and begging intercession - from very early years. So Sorin wins on points. The intercession of saints has existed from the earliest days, and extended to dead humans from scarcely-later days. For "great apostasy" restorationists, this happened (I think) too early to extricate from Christianity as the first authors intended. Note that the most notorious restorationist sect, the LDS, goes as far as to post their dead righteous to rule over exoplanets.

Some Christians did attempt to eject necromancy from the faith. Vigilantius is here noted. Jerome had taken him to school, as mah boi does.

To invoke practical necessity, as Gavin Ortlund might, I sometimes dispute Jerome. Jerome was one who preferred the dead to the living. That can be a problem.

I propose here that it is not a problem at base; there is indeed wisdom to be had from the departed, if not from the process of departing. Here I think practical necessity supports Jerome. So - perhaps Sorin could have stopped there.

Aphrodite's girdle

Stephen Kane gets cited a few times around here, mostly for exoplanets. But he also sometimes ponders planets close to Earth. So here is something making waves in the Youtube sphere, alongside Sean N Raymond. It's about whether Venus had a moon.

I don't pretend competence in these fields. At any rate Kane's paper is talking about a hypothesis: if Venus had a moon early-enough in her history, then that moon would have been crushed and would have fallen by now.

I will, however, note that Venus is presently rather flat. We do except those volcanoes, mighty Maxwell Montes (the rare male exception to the naming rules there), and the Alpha/Beta Regiones. But widest of all, lies Aphrodite Terra. The "continent".

Aphrodite Terra tracks the Venereal equator. This always has stricken me as strange. Venus orbits extremely slowly, and that retrograde; such that the planet is more spherical than Earth's geode. Earth can run solar-synchronous satellites in orbit; for Venus, I guess they can stationkeep something with a sail at SVL1.

If a moon disintegrated in low Venus orbit more-or-less coplanar with Venus' ecliptic, that might account for colossal masses atop Venus' equator. Venus has resurfaced much of its plaons, yes. But maybe Aphrodite Terra was simply too massive for this effect to cover it all up. (Alternatively the moonfall happened recently.)

Nestorius and Cyril in context

As an occasional "Nestorian" blog, and certainly a pro-east-Syriac blog, I have some interest in that history. Matt Crawford traces the history to Nestorius' roots in Antioch. Good luck to Crawford; I hope he fares better than some others.

Cyril is meanwhile (somewhat) rehabilitated as not just making up theotokos (Latin, deipara) himself. Most people (like me, and Candida Moss) have seen Cyril as a base opportunist. We here have inherited Schwartz in 1928. Even if, of late, we have had to back off some of the Agora slanders against this Miaphysite saint.

Emperor Julian, born to Christian (Eunomian!) emperors, among his Christian foils had to address such as were saying theotokos or something like that. As a pagan, he recognised this term as pagan, like a mortal-ess birthing Heracles or Dionysus. The Eunomians weren't saying this; only a Miaphysite could say this. So Cyril was heir to a Miaphysite tradition. Gregory of Nazianzus knew this as of Apollinaris; later authors would see Eutychianism or "Julianism". Nevertheless Gregory (somehow) affirms theotokos.

Nestorius (and, I could add, John Chrysostom before him; and Diodore of Tarsus) grew up where Apollinarianism was staking its last redoubt. Theotokos could be tolerated anywhere else. Not in Antioch, says Crawford.

My reading of Crawford suggests he personally supports theotokos, or at least some form of Christian unity without taking that seriously. He wants to humanise Nestorius without accepting him. Maybe he can. I'll leave that aside for now.

The story may start with Paul of Samosata, all the way back in the middle 200s AD. He had posed, perhaps clumsily: for the Word is from above; Jesus Christ, a human being, is from here. The Council of Antioch shut him off AD 268. Eunomian subordinatism owes to this thought - if taking Paul's words literally. Athanasius devoted at least half his career against Eunomianism, maybe more than half. Nestorius' dyophysic might descend from Paul, also; but I think it turned out better, and I don't know how far Athanasius would have disliked Nestorius.

Gregory and (maybe) Athanasius could have threaded this needle. Real problems started emerging out West. Not the problems I'd expect.

One Leporius of Marseilles had propounded a notion of Christ as the merger of God and man. We don't really have the exact words he said, but the Masillians booted him out. Leporius then met Augustine in Africa and, basically, did the apology tour. The ensuing libellius survives through extensive quoting by John Cassian who brought it back to Gaul, with Augustine's personal imprimatur (if mostly an antiPelagian text, here). Cassian's aim was to rebut "Nestorians" who may well have preserved Leporius' earlier work.

Crawford carries over recent scholarship on Cyril's oeuvre, also: On the Incarnation of the Only-Begotten and that There is One Christ and Lord according to the Scriptures. This - for De Durand - preceded the whole feud with Nestorius. Nestorius' accession as the Patriarch of Constantinople, for Crawford, was unlucky for Nestorius, because Cyril was already an enemy of the dyophysitism who also shared his antiApollinarian credentials (or so he claimed).

I admit, I think Leporius got it right first-time. Augustine was always a momma's-boy who could easily have fallen in with the Ephesus councils, had he been born that late. I like to think - say - Jerome would have known better, hence why his work got translated to Syriac and passed East.

Some high-Isp experiments

ToughSF posted a few avenues of research, early last weekend. Both definitively drawing-board. I'd have said something but I couldn't click the link to one of the actual papers then, so - you get my take on them, today.

One is laser-hits on a liquid propellant. It splashes. As far as ToughSF knows, nobody's solved this one. Then he went on to note how lasers sploot droplets. Next!

The University of Surrey is asking about magnesium rockets. I'd heard of burning aluminium (as Surrey spell it) in oxygen, or maybe some even stronger oxidant like ozone. Burning metals isn't for Earth or LEO, but it intrigues me for low-grav takeoffs like our Moon - once bermed. Magnesium is just as common over there. But again, this looks rife with Unsolved Problems. The link will be here (pdf).

Absent a pdf, we do get an illustration. It looks like AI and makes little sense to my mortal eyesight. I just see magnesium is not planned for surface-to-orbit roggets the way some were talking aluminum. They want mass drivers, to take this fuel into orbit which rockets burn it up there. Into that topic, PlanetaryEngSys has butted: that mass drivers should start small, such that the capsule then fire the engines on that (parabolic) trajectory, to bring it to orbit. Seems more reasonable than Surrey's proposal frankly. ESA should pay that grant to them.

Quirinius

This blog has had some occasion to look into The Third Gospel's use of material and into its general tendency. Some of Luke's changes can be illustrated with textual-strain. Among the more-diverting results is Jesus' long gestation: he was conceived in Herod's reign (d. 4 BC) as in Matthew, but he came out among us during Quirinius' census (r. AD 6). Mary bore a burden quite unlike those of most women.

Miracles, or snark, aside: at least Joslin McDowell never entertained that notion, Protestant as he is (yeah, he's still alive). He prefers that Quirinius was there several years before. And maybe this Roman was; but he wasn't doing census in someone else's kingdom. Especially not Herod's.

Michael Kochenash explains Luke's plan. Luke knew of Roman-Jewish talk that the census was a flashpoint of rebellion, and this rebellion in particular. Kochenash goes further: he notes Josephus (a Galilean friend of Herod Agrippa II) in The Jewish War and Antiquities. The former, Josephus completed before the Campanian volcano buried Agrippa's sister; this eruption received note only in the latter.

TJW is well aware of Quirinius' census and of the revolts around it. But this book does not connect those events with the Revolt. The connexion becomes explicit only in JA. Kochenash does not see Josephus, here, arguing that point for or against other historians like Justus. It seems an idea that Josephus had just... come up with. A reasonable idea, to my mind anyway; but never mind that.

Kochenash does not think that Saint Luke had come up with that idea, either, by himself. Instead - Kochenash argues - Luke made of it a trope. Roma and Judaea came into serious Imperial contact through that census. Luke associates this contact with Jesus' infancy. What the Jews do to Jesus, is going to post a milestone to the Ninth Of Av; which the Jews perhaps could have averted, by embracing him as Christ.

Crossan would supplement, here, the Holy Spirit as Divine gloría. This has abandoned the Jews to settle upon the Apostles, and - finally - upon Peter and Paul who are headed westward.