Siderophobia

Nathan Cofnas got things to say 'bout THE JOOS.

I will preface this post, because I must, to disclose that legally I am Jewish but by religious choice, am now Catholic. This means that I disagree with the Judaic claim to salvation-history, which contradicts the Catholics'. I also must be fair when I think about Jews in the past who done messed it up, most recently Béla Kun. I ran a series a few months ago on Mark Cohen's perspective on Islamic rule, which I hope I was fair about, because I really did appreciate Cohen's work.

As for historic antiSemites in my adopted tradition: I had to put in a good word for John so-called Chrysostom where he opposed the truly evil Cyril; although, I do not consider the truly good Gregory of Nyssa in Chrysostom's ranks. Some of the Patristic attacks concerned the practice of usury unfortunately lawful for Talmud Jews when applied to outsiders. Gregory, so far as I have read him, did not himself write so far as to blame the Jewish bloodline. Chrysostom, most agree, went that extra mile, to his shame.

What I find in Kevin MacDonald's circles is a form of siderophilia. Iron loves iron, and other metals of that sort; in an iron meteorite, you will always find nickel as well. In MacDonald's circles you will find Vox Day and Ron Unz. Alongside the wishes that one could go back in time and drown American Jewry in the Atlantic - which makes one wonder about, forward in time - one also finds the theories that masks do not stop the coronavirus and that vaccines are deadly. One finds other theories here as well, equally noxious.

The "association fallacy"? Maybe. But in these days of plague, Israel did better than most nations. I should sooner associate with Jews than with antiSemites, despite my apostasy.

Baishiya Woman

Via hbdchick, Tibet may have its missing link. This is a Denisovan - not a para'Sovan like the Melanesia got - in Baishiya Cave. This is in Tibet proper, 60kBC.

As noted, it's not (yet) obvious that the Tibetans today mated with these girls up in Tibet. After all, their mitochondrion is not found in modern Tibetans. It is getting more obvious that, at least, the Tibetans followed these tribes up there, before or after doing the thing, presumably spawning males among the Tibetans.

Curium-247

Whilst I'm (still) figuring Lambert curves, without much luck - here's a piece on primordial Curium. This got me, er, curious. Because I didn't think we had any. Benoit Côté et al. doi 10.1126/science.aba1111

Curium-247 is the isotope in question and is, it turns out, not very radioactive. Half of it will decay to our dear friend ²³⁵U ... after 15.6 million years. This is still a short time from the perspective of a 4567 million year old solar-system so, as noted, I do not expect to see any today. I do expect the Uranium-235 in its grave but Côté's team say more; they've found the traces of the original. Alongside Iridium-129 which decays about the same.

I read that the Curium / Iridium ratio found in meteorites looks a lot like the ratio of their decay-product. So these elements have not been subjected to further baryon irradiation in space. Further, when these elements were created in the first place, the Curium wasn't created in any great quantity. This is telling Côté that the Creator (as it were) was stingy with His neutrons. He concludes: not a neutron-star merger.

I wonder about using any neutron emitter to create some Curium-247 right here today, or at least in some orbital factory. Besides firing it off for the usual Atomic Rockets, it might be good in a power-generating reactor.

Cm-247 stores for a long time, as noted, so isn't a hazard in small doses. And when it decays it decays into something you can still use. As I look around I see that its own critical mass is 7 kg (pdf): compare U-235 at 52 kg or even U-233 "thorium" at 15 kg. (Take that, NuScale!) Out in space every one of these masses decreases if you goose it with a little antimatter.

One issue of course is that whatever hits something with one neutron will likely hit it with a second neutron, especially if the target sticks around... which Curium-247 will do. Cm-248 also sticks around, 348000 years here, and she has some research value; but she is not useful for blowing sh!t up, like fusion rockets. And a third neutron will make californium which will fire more neutrons around the place and really mess you up.

Circling back to the original post, perhaps one reason we don't see Cm-247 in high doses today may well be exactly because wherever it collected into 7 kg packages, it went boom. That might put neutron-stars back on the table.

UPDATE 7/27: considering NuScale. VERY belatedly . . .

Manifold manoeuvres in the dark

Oliver Morrison has a master's thesis: "Use of Manifolds in the Insertion of Ballistic Cycler Trajectories".

We have all been assuming a craft in orbit around Earth, or on Earth, to get to Mars by a Hohmann or cycler trajectory. From Earth to Mars, Hohmann is bad enough for delta-V and cyclers are worse. You must do a "direct burn" - against a trajectory of longer amplitude than a Hohmann would be. So high thrust; damn the impulse. Hence Zubrin's warning that Bush and Ibn Saud will soak you on the shuttle fee. Elon Musk is assuming as much, too; from getting straight off Earth into a Mars Hohmann with his Starship. I was talking up tethers not long ago to get from orbit on out, or even Orion from northern Baffin Island. Gravity wells are a pain, yo.

What Morrison offers which is new: if (somehow) we've started from [Solar-Earth's] L2 halo, and we're going not for one-and-done Hohmann but for "S1L1-B" (Earth-Mars n=2): we might save on delta-V at least on that cycler. Morrison wonders what if someone's got a spaceship factory up in L2. L2 is metastable and its halo will kick you out if not station-kept. Morrison says: if you want into a cycler trajectory, find the planet's station at solar L2 halo, disconnect the craft, and let the halo's manifold do the work.

Same might hold for L1, or for Lyapunov or Lissajous closer to the nexus; but Morrison's not looking at these. Earth-Moon L2 looks interesting, as well. Morrison cited R. P. Russell and C. A. Ocampo but not, I think, 2006 "Optimization of a Broad Class of Ephemeris Model Earth-Mars Cyclers"; they'd endorsed S1L1 and Aldrin, adding only another n=2 "8.049gGf2" to be launched July 2042.

My site is all about SVL2 so... Venus-Earth might have a non-Hohmann cycler analogue. [UPDATE 3/1: If we ever get a delta-V under 10 km/s...]

This implies that high-mass cycler construction be done in L2, whence delta-V costs are least; and that low-mass shuttles should take Earthlings (and Loonies, and Venerean-orbitals) to L2. Once off L2 the cycler doesn't return to L2, because drrrr it's a cycler which needs gravity-wells to correct its trajectory.

Lambert's boomerang

On topic of cyclers I am revisiting James M. Longuski 2002 (pdf). For this purpose I am not looking at a permanent cycler - just a trajectory where Planet A boosts cargo that goes by B and comes back.

Longuski starts with these six axiomata, which I abstract out thusly:

1. The [A-B] synodic period S is [some rational fraction of A’s sidereal years].
2. [A]’s orbit, [B’s] orbit, and the cycler trajectory lie in the ecliptic plane.
3. [A] and [B] have circular orbits.
4. The cycler trajectory is conic and prograde (direct).
5. Only [A] has sufficient mass to provide gravity-assist maneuvers.
6. Gravity-assist maneuvers occur instantaneously.

For Earth-Venus, the S fraction is 13/8 Earth years. For Venus years, we need 583.92/224.701 = 2.59865; 13/5 would do it.

Axiom 2 gave Longuski a two-dimensional system, which for Venus and Earth happens only once every 243 Julian years. (For Earth and Mars, his third assumption comes close to killing his project...)

Venus' mass at Venus Express's 250 km is inferior to Earth's at that height. I read #5 as "only Venus has nothing we care about crashing a large artificial asteroid into". If we are using Venus for a gravity-well then my beloved SVL2, although also hitting ecliptic in halo, is a million km high at a right angle to Venus' orbit: pretty darn safe, the safer the closer I huddle Lissajous.

Per Longuski, This is a Lambert problem. Given [natural] n, we want to find a solution R(t) to the two-body problem that connects R₁ = (1, 0) to R₂ = (cos(2πnS), sin(2πnS)) in a time of flight T = nS. R₂ although an oversimplification for E-M is not so bad for V-E.

Each n - number of synods - has multiple solutions. I expect the venerable Hollister cycler for a n=1. And here any astrologer can tell you that n=5 is, exactly, that metonic with the Hohmann orbits: 13 Venus years, 8 Earth years wherein Earth can expect a return on its fourth year. For that what McConaghy and Longuski say about Earth-Mars is equally applicable to Venus-Earth:

Since taxi spacecraft must rendezvous with the cycler spacecraft as it passes A and B, we want the A V_∞ and the B V_∞ to be as small as possible. This typically rules out trajectories with a small number of revs (r) per repeat interval. The orbit that achieves the lowest possible sum of V_∞ at A and V_∞ at B is the Hohmann transfer orbit.

You can see why Hop David loves this one. Some course-correction is needed, so from Earth its first run by Venus has to run into the well; same with its next go 'round Earth. Not, though, notably far down the well; I think even Earth's geostationary satellites might be safe, and Venus just has statites which float anywhere.

SHORTFALL 3/4: I can follow their work now. For circular orbits (admittedly not the case for Mars) I dispute only aphelion. I target outer planet's L1 as if it were a planet too.

Chad Galactic

Zimmerman has a roundup of space news, mostly on companies not going to space this week.

Yesterday Casey had dropped by his own blog for the first time this year trashing NASA's Senate Launch System, which even Senators don't want anymore. Today we learn Bezos' Blue Origin is delayed. UPDATE 2/26: extra-virgin Galactic is not busting its space cherry; Tim Ellis is still vaporware. At least muh boiz Rocket Lab are out of the headlines...

Tomorrow we might be seeing SpaceX doing another Starship launch. We don't expect it to land, but they're getting a lot of experience in doing anything but land. [UPDATE: Probably Tuesday. Landing the thing is a... thing, and it's windy. So, Elon needs to account for wind.]

This may well explain how come Bezos Press aka Washington Post is running hitpieces on Musk and his company, and why the US's 3LAs are mounting Serious Investigations. Nice company ya got there.

Marrying Pluto with Venus

I am musing about the unobtainia around a Pluto Ramjet for a low-density mostly carbon-dioxide atmosphere. The Project's design in the 1950s was for Tory II-A, a solid reactor running about in the 1500s K (Wiki: 2330 °F). The SLAM ladz had a "Tory III" lined up before the whole project was cancelled... for Earth. Here we are at the Venus blog. Let's talk Tory IV.

I am wondering if I can raise its temperature, for an alternative to chemical scram. Higher temperature means faster exhaust, which I will need to raise my ramjet to higher altitudes and speeds. Aiming to catch up to Mach 28.

We don't need Coors anymore. The 21st Century ramjet's nuclear core can be surrounded with tantalum-hafnium-carbide (TaHfC) which stays solid up to 4488 K. This allows a liquid core, like LARS UPDATE 7/27 but that's silly - luckily, we can probably get a vapourised core out of most heavy metals below this temp.

As for the Venerean ambience, ToughSF a couple years back did a relevant piece, on reverting global warming. At 3000-4000 K the ramjet would be breaking the atmo into carbon monoxide and oxygen. Above 4000 K: pure carbon and oxygen. Hence ToughSF's interest.

As they say for NERVA, the propellant is the coolant. Either way I'll want oxygen ions not to corrode my ceramic - nor carbon to clog the exhaust with soot. I don't care as much about neutrons. I only want the thing up for maybe 48 hours.

The molten core would start to cluster further back but at its cruising speed would sink to the bottom - leaving a low-pressure vapour at the top like the empty part of a thermometer. To keep the core more evenly distributed around the ring: consider spinning it. There is certainly the incoming air to turn the fan. This does slow the exhaust a bit, and it adds mass - the heat-resistant ceramic also, I hear, is dense. To mitigate, we add magnets to keep the ions, maybe even the neutrons, where they should be - outside. And we can siphon electricity for the cockpit.

Overall this design doesn't look like Mach 28. It looks more like a Mach 8. Still a rival for the scramjet and it will stay up longer and higher. A platform, in low atmospheric pressure, to push the Lightcraft rocket(s) toward Mach 28.

UPDATE 3/19: Compartments, with low critical masses. 7/27: LOL! Let's skip right to vapour.