Low temperature capacitor

This release, in Fahrenheit, is suggesting how to store energy when it is cold. They are looking at Mars, to reduce rover heating (and energy) requirements at night.

DOI 10.1021/acs.nanolett.0c04780 has an abstract that gives the Centigrade. But I prefer Kelvin: 200 K.

As anywhere else goes, I am unsure. Most space craft are rarely in shade for long, so don't need much in capacitance anyway. Statites in umbra (like Venus') will get this low; so would craft beyond that 2.5 AU snowline (e.g. Ceres).

However any craft in vacuum is also a candidate for nuclear power, whose energy becomes heat by thermodynamics. In vacuum is no atmosphere to carry heat away: see all those radiators on the Space Station? And don't talk to me about wormholes.

As for the (few) atmospheric worlds near here, Titan (which really is not near here) might still be too cold at 90 K. I more wonder about high-atmo floaters on Venus' night side. Also the Moon: power storage for rovers on night-missions.

Ludicrous speed

The Well of Souls is op'ed and all the devils are... being posted about, here.

Our first bit of silly comes from Göttingen where Dr Lentz is talking "solitons". Apparently with conventional sources of energy (as in: not Alcubierre's negative mass) we can create a Warp Bubble, keeping the ship aging in normal time as it carries on to Alpha Centauri. The "twin paradox" is no longer in place. The press-release is less clear about the causality paradox. And the conventional mass we need to burn is a red dwarf star hundreds of times Jupiter mass. Oooookay then. UPDATE 3/31: Martire-Bobrick.

Then there is this from Portugal: traversible wormholes. They are not very big wormholes... yet. The Portuguese think they can use them to deliver FTL messages. Also (I'd add) one might use such to drain heat from a ship toward, well, nowhere and thereby create a cloaking-device. But again I ask - what about causality.

I don't wish to waste more time on all this than I have to, but maybe some science fiction authors might get a kick out of it, if they are not very good authors.

NAH IT'S SHITE 1/16/22: Give it up, dude.

Microgravity crops

On the way Arizona (not Thanga) posted another note on microgravity crops. THAT, I'll take seriously.

I expect us monkeys will be living on the outer edge of the tin cans. Suppose, though, our cans aren't the rim of a wheel; suppose they're a big cylinder. We'll have lower gravity hubward. Be nice to use the space for something since we're not living there. I mean other than the sort of fun monkeys might get up to in low gravity for ten minutes at a time . . .

Also what if we have tied these spinning habitats onto an asteroid. Maybe the asteroid's surface could be purposed for farming - again, because we're not living there.

Food in microgravity (or an asteroid's milligravity) also may get bacteria.

Loony

Jekan Thanga has got his Arizona uni into space science news twice this week. Mostly he's looking into the Moon. One article has something on prospecting for water, inoffensive enough.

In the meantime Thanga wants to use the lava-tunnels as a DNA museum for species from Earth. Powered by solar. Not considering that solar panels degrade especially when exposed to micrometeors on the Lunar surface.

Sigh.

Doctors of the other two churches

Jacob Tate over at OnePeterFive is reminding us Latins of Thomas Aquinas. I am considering if the non-Chalcedonians own anyone close to him.

To start with the Miaphysites, I shall expand the net to the early Maronites also. This, then, starts with Cyril of Alexandria (not one of us!). The two councils of Ephesus were a great victory for that side. Following the Chalcedon reaction, officially Severus and Jacob bar Addai are credited with founding the independent Ephesian church. Among the west-Syrians (using Andrew Palmer's hyphen): Bar Salibi, Michael the Syrian, Bar Hebraeus. Jacob of Edessa's correspondence amounts to an excellent practical guide for a Christianity under alien rule. And there was Dionysius of Tel Mahré among the historians.

I am less familiar with the rest, but the Coptic tradition can certainly look to Severus ibn al-Muqaffa', and of course the Copts are persistent to the present (writing mostly in English). The Tawahedo in Ethiopia was heroic at least to preserve this line of work. Then there's the Caucasus, although over the Middle Ages they have inclined to the Greeks and then to the Russians.

Over the centuries, then, the Miaphysites mustered a formidable intellectual defence against our Church and then against Islam.

Looking at the Church of the East, I cannot think of as many great names offhand. Here it should start with the Antiochene tradition, Theodore of Mopsuestia (less so Nestorius himself); Aphrahat, perhaps, among the para-Nicenes. The "catholicoi" popes Babai the Great, Isho'yahb III, and Timothy II produced impressive literatures. The school of Nisibin was also productive, partly as countervail. Among their historians were Elias bar Shenaye and all the contributors to Siʿrt.

The Orient suffered by contrast with the nearest East. This is not entirely their fault: there was always something of an iron-curtain keeping their literature even from crossing the Euphrates, much less into Greek and Latin. Over there, first the Iranians and then the Muslims sporadically suppressed their libraries. And the Portuguese did no favours for the native Christianity in India.

Also, though, I find the Eastern Church to be riven with schism of its own. Isho'yahb III exerted much more energy against heretics and the breakaway provinces than he did against (pre?-)Islam right under his nose. Other churchmen had Henana's Origenism with which to deal, and various strange ideas seeping out of Nisibin.

The Eastern Church had trouble even defining what it was, beyond "not Ephesian" and, later, "not Islamic". Should they accept a subordinative Christology, like Arius and their own Aphrahat? (Once the Muslims came along, that proposal was an embarrassment.) To revive Origen, like Henana? (Babai killed this one dead.) What of Bar Sauma's "Baptist Convention" theory of a seminary-run Church? Above all, what to make of Chalcedon?

Where do we put the tethers?

2L4 is not a Hohmann free-return cycler so needs to adjust its angle, by 108°.

That 2L4's aphelion rose as the angle decreased means the angle spans that line between the Sun, SVL1, Venus, and SVL2. On its first trip, it starts like SVL1 ahead of Venus heading to perihelion. On return its angle must return to that first angle - to bend that 108°, forward. (Earth's L1 is forward, to which the cycler must catch up.)

Cycler perihelion is 1,586,931,492 km toward the Sun, usually. Given Venus' own 0.007 eccentricity, the cycler always runs by that one's own L1 halo (if aimed right). Also the cycler starts angled to perihelion. SVL1 is a fine place to park the cycler before it starts on its way. Or, park a tether up there so a craft in orbit or in Hohmann can access it, and become that cycler.

Between any L1 and L2 there's a planet. We'd like to use the planet to boost us and, hey, that's where we're reloading outbound cargo.

After its full orbit - hitting a moving target, understand - the angle is called "gamma" (γ) and is -3.57° where 0° is the direction of Venus' orbit. We expect that low value, so close to perihelion: note, it's just Math.Acos(Vector3.Dot( Vector3.Normalize( velocities.Vf) , r2)) * 180 / Math.PI - 90.

That low gamma means that either Libration Point's tether, once initially used, is not of use twice. Stations at either might be available to focus more Solar radiation at the cycler's sails.

Vinf

I've been talking about v_inf, or v_∞, or hyperbolic excess velocity despite not knowing what the heck I've been talking about.

I admit I still don't. But I did find something I can understand: black-box equations.

Erik Francis explains it all: from any orbit, which goes at v_cir velocity, you want into some other orbit... Hohmann, probably; then off-Hohmann. What's the delta-V? And no, you don't get just to subtract one from the other; we're doing astrophysics here. We're not sailing around interstellar space. We're in a solar system, probably a planetary system. We're locked in an orbit.

Where escape-velocity is the velocity just to get off that first orbit (if angled directly away), you're in orbit - and if it's a circular orbit, you are decidedly angled 90° from that. v_inf looks at other angles - like the angle to get to Hohmann, or to 2L4.

Francis says: √(v_inf² + v_esc²) - v_cir. That assumes you don't have the kick-ass thrust needed for an Oberth manoeuvre.