On-board variable propulsion

Ion drives like VASIMR, and adjustable NERVA like the shockwave rotor, can squeeze more efficiency from their drives by feeding in energy and/or adjusting the exhaust throat. It occurs to me that this means recalculating the rocket equation in real time. As in: on the rocket, not outsourced to orbital data. That drinks more energy for compute, which then must be controlled somehow; probably by radiating out.

These are exponent and logarithm equations. If we were using a TSR-80 extended BASIC processor, welcome to Taylor series.

Needless to say, that is some bull-tish. Don't we have some tricks to turn a float into a longint? Just shift the integer over bro. *(long*), subtract some magic number, then <<= bro. Like when the exponent was -1/2.

That'd be great if the ratios were all integers. They... probably aren't. Because they aren't, this method requires to poll the ratio until it reaches an integer and then run the calc.

We'd hope to force integers on all four values of the Tsiolkovsky to some cromulent unit-length, like millimeters and grams. We'll see. Instead of exp(dv/ve) it's exp(dv) × root-ve(e). One multiplication operation. Gotta be better than Taylor(8). Ln(m0/mf) meanwhile is [lb(m0) - lb(mf)] × ln(2). Now we have to ponder overflow: 32-bit integers go only to 2³¹. So, no; these are going to be km/s maybe even Mm/s which we have to rescale after the calc.

Depending on the unit-lengths I might even consider storing the exponent-powers and the e-roots in tables. Data got corrupted on Voyager but I suspect our triage is better today; so's our shielding. On arrival at the destination our need to punch the engine shouldn't be as dire, so the memory used in the tables can be wiped, for reüse in the actual mission.

This was imprecise for q_rsqrt and will be imprecise now. Those 1990s gamers applied Newton's method upon that approx "y", thus: y * ( 1.5F - ( x * 0.5F * y * y ) ). Lotsa multiplications, here. And that's second-order because this was just a square. And, to remind: we're talking about high exponents and high roots. May as well devolve to Taylor.

Kasper Nielsen's cheat-sheet of "float tricks" may offer an out. We have NVIDIA's "piecewise linear approximation" which shouldn't overflow. Ian Stephenson does one better for Pow2 which "approximates the error with a quadratic".

There are other unsafe-code solutions in the roster, some just straight assembler with no overflow checks. Good news: I doubt we need 'em for the floating fractions. The mass ratio as wet/dry[-er] even at some Apolloesque 96 isn't going to have ln(x) all that high (4.6ish here), and this is going down as we drive. The velocity ratio working with inner-system delta-V and as-good exhaust as they'll allow us (like, 14 km/s) should also be low, enough for exp[x] anyway.

Types... deletes... and stuff

Sydney Sweeney should not be supporting gambling in sports. This support is a failure of character on her part.

I recall when Instapundit lambasted Busey for appearing in the Turkish film Valley of the Wolves. I recall he called Busey a "whore". Euphoria, I propose, was just as disgusting a project. So it is not like Sweeney hasn't already telegraphed that she, like Busey, was willing to appear in whatever paid.

If you think I am being cheap: some of the shots which Insta is levelling at her detractors are cheap. (And if we must Go There, the lady northwest would probably look about as good as 30-year-old Sweeney sans makeup and airbrush. I've personally dated northeast.)

I might further ask, from the support of Instapundit and others, to what degree they have been bought off too.

So you want 70 tonnes in Venus-Earth Hohmann

The Superheavy has pushed a 75 tonne load into LEO; maybe some krauts have pushed 70 t. This load is headed for Venus. v_inf, for that, is 2.5 km/s. Leviathan expect to pay Elon Musk MONEY to send it all in a 160 tonne Starship; and MO' MONEY, for the fuel top-up in LEO. Presently the paper hasn't stated how much fuel they need but Google has told me, 400 t (megagrams). In this poast, I compete for that blank cheque. We are all about branching paths here.

An interplanetary Hohmann operates by regular launch windows, Earth/Venus on that pentagram synod of 583.92 days. In this case we're not sending any time-sensitive cargo (like monkeys): Leviathan is supposed to work for a year, so what's a coupla'more months. This means I don't have to blast immediately after getting to LEO and topping up. I can afford to wait; to adjust my cargo's trajectory from LEO to something better nudged into.

We start by renting the Tamil Tether. This yanks my cargo into HEO, here standing for high eccentric orbit. Apogee 200-300 megameters well over GEO. Weee!

That is delta-v 2.83 km/s; if I'm shifting only 75t, momentum 2.1e8 kgm/s. This can be spread over a minute or two so most tether materials would work. The 2.3 terajoules of total energy will, however, lower the tether's altitude. Raja's tax must be paid.

From this apogee, I'm in range of a possible second tether which promises up to 100 t - although here the tether material must be ... stiff. In this case I must spend the remnant 25 t budget on a dedicated Venus-entry vessel because I'll not fit a full Starship on that poor thing. Copilot didn't even suggest the idea.

Instead Copilot adds solar-electric tugs operating for several weeks in that 200-300 Mm domain. I could even have a near-empty spare 160 t Starship hanging around up there (which is why we discussed only the 75 t above). We don't need to park them on the spaceline although that will be nice too.

Above all (heh) the tugs can push my 235 tonnes into a Molniya trajectory, that almost hits Earth. It is at perigee, the velocity is highest, yay Kepler, at 10.8-11 km/s. At the right moment, we do the Crazy Hermann off to Hohmann. This delta-V is 248 m/s. For this push, propellant mass runs just 16.1 metric tons. With 16.5 MN thrust allowed by six Raptors, it is burned in 3.65 s.

Leviathan conceded a multiple-launch mission, the moment they mooted refueling. My mission architecture reduces the launches to two. One sends the load, which competitors can bid for; tethers hurl this into HEO. The other sends a whole Starship (under)laden, which... tethers hurl into HEO. The 16.1 t (plus) of fuel is probably in the latter, for simplicity. The load and the 'ship, they dock (because Leviathan assumes docking is possible) in HEO. At some point, I send my mission via Oberth with much less fuel than that for which SpaceX will charge them. I do assume infrastructure, but that infrastructure is available for future missions. Like for that Sunbird > Saturn mission.

I might add that Elon could use something like this architecture to get his 'ships back. Could be he's loaded enough propellant for a cycler-trajectory, to drop off the cargo and keep goin', so Earth gets it back... whenever. 3-0-2-9 promises 4.8 sidereal years; Hop David's scheme awaits the whole eight year metonic. Maybe Elon doesn't want to let his 'ship rot in the Solar well for years so sends over propellant, to load onto the 'ship, which waits in high Venus ellipse-orbit for the next direct Hohmann.

Either way there's likely to be additional burn, for 3-0-2-9 probably on its next return at Venus, to adjust the angle as to intersect Earth. I say likely because over eight years, cap'n Hop David might be able to trim thar sails.

Coxon was an op

I don't desire to speak much on the topic of AI dangers, so I'll just flag a few people not to heed. Not ever.

First up is the oh-so-principled Coxon whose resignation was coördinated with news announcements all over the Google-approved outlets. All this doomerism is being Dustin Moskovitz funded. It is all an op.

It turns out that the whole "Hugging Face" hack was, likewise, an op; driven by nefarious (human) agents. For those who still think "effective altruists" are human.

Anthropic, we learn elsewhere, may be trying to get AI nationalised, or - more likely - attain a state-ordered monopoly. The latter has an ideology and the ideology has a name. It is not such a name as online fora much allow to use.

So I'll keep watching my slop kthxbai.

The Median myth

Two decades ago Karen Radner floated a key thesis about the "Medes" - Madayë in Aramaic - down to the late 600s BC. The Assyrians never quite could tell that the hillfolk were coalescing into some "Median Empire". Skip ahead a few centuries and Herodotus has all manner of lore to relate about these "great kings". Most of these Medes overlap the Babylonians, starting with breakaway king Nabopolassar. But the Babylonians say much less of these hillmen than will the Greeks. They do know some latter leaders: Kashtariti, Umakištar, finally Ištumegu.

Theories of "secondary state formation" may apply here. Alongside the Romans, "tribal confederations" along the Rhine and Danube limes start taking on the character of kingdoms; we may say the same for the later Arabs between Iran and the Rhomania. I'm thinking here especially of the Libyans who enlisted "Sea Peoples" against the house of Ptah at Memphis. Nabopolassar, here, struck a deal with "Medes". These weren't his granddaddy's dirty hill bandits anymore. Copilot leans toward a real kingdom at Ecbatana/Hamadan.

We last hear from these Iranian plateaux in the "Nabonidus chronicle", recording a war between an "Ištumegu" (Iranic v->m in this script) and a Cyrus. Cyrus won, so got to relay his genealogy, that he was the grandson of a man with an Elamite name - which name he also took. Cyrus' ancestral lands were important, but not the heartland of the Medes. So who was *R̥štivaigah? - apart from a man perhaps more Iranian than the Cyruses.

The Greeks record elsewhere that "Astyages" also came from a dynasty of sorts. His father Cyaxares fought the Lydians until "the eclipse of Thales" today marked 28 May 585 BC (usually). This name is widely distributed, showing up even in Phrygian, albeit a common name for Medes. Nabopolassar commanded his Medes under their headman "Umakištar" who must correspond to Herodotus' Cyaxares.

Later Darius must contend with the family of Cyaxares, rebelling against him from the east. One was Fravartish "Phraortes" the Mede, who took the name Khshathrita when he got crowned; this regal name is known in Babylon ("Kashtariti") where, interestingly, Herodotus' Fravartish is not. Another pretended Cyaxarid was one Tritantaechmes of Sagartia; we should take him less seriously.

Herodotus got his data from Darius' successors, mainly Artaxerxes Longhand. Of course these successors were steeped in Darius' lore; Artaxerxes is going to be succeeded by Ochus who'll call himself the new Darius.

I propose here that Fravartish remembered that Cyrus had posed as the Assyrians' heir. Fravartish invented a legendary past around Kashtariti and Cyaxares, those great liberators of the Medes therefrom. Darius, reconquering his usurping lying ass, left-alone that particular fib. Darius would give them the Cyrus they deserved, putting down this upstart neoAstyages "this time as farce". Meanwhile the Persians as a whole could inherit the glory of the Medes, again; which Fravartish had lately made more glorious.

As evidence for Herodotus taking his Median lore from this filter, I bring his name for Cyaxares' father. He relates nothing like "Kastrites" but instead delivers "Phraortes" - close the truename of the late Kashtariti usurper, but a false name for the history-book.

Hand, shown

Beale:

Intelligent Genetic Manipulation. We have no idea by whom. But I suspect all the recent alien disclosure stuff is because it is fairly obvious that the genetic record is going to prove that the human species, at the very least, was constructed. With a few more advancements in genetic science, we may even be able to figure out more or less when it happened.

I've unbolded the silly. We've more-or-less been over this. But in light of new findings let's return to this vomit:

When humans emerged from Africa, and for that matter when contemporary humans in Africa emerged into other African environments, the environment hit us but hard. We couldn't control how to handle the coronavirus, nor the malarial parasite. So it was, until came the Late Glacial Maximum, or "Mesolithic", or whatever you call the slip from the general suck of the Pleistocene into 24kBC's full-on Ice Age. Selection was natural. Over hundreds of thousands of years, sometimes supplemented by distant relatives who had been out there for millions.

By that point humans of all sorts still hadn't domesticated any of our neighbouring animals. Well okay: so Alpha (2018). That movie hasn't much been deboonked. Maybe some coëxistence happened with scavenging wolves in the 30skBC. Don't care.

It's in the Neolithic we start seeing goats, sheep, oxen, donkeys, llamas. Again: this isn't the poast to pick apart millennia. Just to point out that, after the Ice Age, a slew of animals got selected - by intelligence. Our intelligence.

It would be a surprise if we hadn't intelligently designed ourselves as well. We had the smarts to pick friendly sheep; why not friendly farmers. To a Sumerian king, a farmer is just another beast of burden.

Or, for Beale... a Cahokian or Chaco Canyon king.

Ebrahimi progress

A subset of the VASIMR process is the Ebrahimi, alfvén recombination. This is being evaluated in the lab. I'd not say "tested" yet.

They can get 10-20 km/s upstream. This scales with the strength of the magnetic field, for which they got good tests up to 9 kV. Thrust in turn correlates with plasma density which their equipment kept low, 1-3e-6 kg/m³; and with the velocity-squared of the exhaust; and with the area of the plasma column cross section. It has so far transpired that their speedy upstream velocities suffer interference, and that they want a bigger lab but they would say that.

Keep in mind the very physics are still young and may involve Navier-Stokes.