sevenperforce

A little look at how having all four flaps allow for multiplanar control authority: If you were to only have the forward fins actuated and have the aft fins fixed, then yaw and roll would be coupled: you couldn't yaw in one direction without rolling in that direction too.

Oh, blowing it up would be out of the question. The goal is to nudge it out of the impact zone. The hypo specified an interstellar object. Not sure how we'd have ten years lead time for something like that, but if we did, we're talking about rather high velocities. The Chicxulub impactor did enough damage to render the Earth uninhabitable for humans as we exist today and it was less than 80 km in diameter with an impact velocity of around 20 km/s. An interstellar impactor would have an impact velocity of easily up to 50 km/s or higher, meaning that it could mass only 1/4 the size of the Chicxulub impactor and delivery the same-size punch. Definitely not a large planetoid.

If you want to make it an interesting hypo, then say something like this: "Assume the existence of stable, self-supporting bases on both the moon and Mars, capable of accepting the majority of human life between the two of them. Assume further that you are restricted to current technology in actually getting humans to the off-world bases. How do you do it in ten years?" Because building a stable off-world colony is the work of a century, not a decade.

I don't think you'd want to mess with engine start transients during the flip recovery and terminal descent. I've thought about this a lot, actually, and I think it's a potential failure mode hedge. If you have only two actuated control surfaces and one of them locks up, you're screwed. If you have four, then you can lose one and compensate with the other three. It also allows broader control range for different entries. Remember that the ship which goes to Mars needs to be able to return to Earth. The Earth return is also going to be the highest-energy entry, so you want the most data on it. Therefore you want the Mars return to use the same EDL mode as your basic ship so you get the most data. That also means your Mars EDL needs to be incorporated in the same system. EDIT: Moreover, if you only have two forward canards, yaw is strongly coupled with roll and so you will have very little yaw authority. Honestly, yaw is challenging to control even with four actuated surfaces.

Tsar Bomba and the B41 were technically 4.5-stage devices: (boosted) fission primary for the first 1.5 stages, fusion secondary, fusion tertiary, and optional fission(able) tamper. Both the two-stage W56 (MUCH smaller) and the B41 had a yield to weight ratio of approximately 5 kt/kg, although declassified documents suggest even potentially higher (and cleaner) yields. But whether you build a multistage device or just clustered smaller warheads, using that yield to weight ratio suggests you could potentially fit up to one gigaton TNT yield equivalent on a SINGLE expendable Starship.

It looks like it has a reasonable degree of passive stability. My suspicion is that with the gimbal kick from those engines it can perform the tail flip even if the aft fins aren't fully folded. Just might take a little more thrust than normal.

Yep, exactly. There is no theoretical upper limit to the size of a multistage thermonuclear device. With just the US, Russia, and China working together we could easily build a dozen gigaton nukes. Throw in nuclear engineers from Israel, France, and the UK and we can probably double our output. Ten years is a long time, even when you're dealing with interstellar velocities. I would say we could launch the first interceptor in under 24 months and send backup interceptors every six months thereafter. Ten years is not enough time to develop off-world closed-loop life support for any significant segment of the human race, however. On the other hand, if you specify that you already HAVE closed-loop life support available (moon or Mars base, for example), the hypo becomes much more interesting.

They won't do this. I agree. It's really nontrivial and the amount of back-and-forth they've done suggests it's still unsolved. Yep, I agree. God, I'm excited.

e cannot be changed but π could be different in a non-Euclidean universe. Of course if you define π as "the ratio of a circle to its circumference in Euclidean space" then that's unchangeable, although only tautologically.

That's the whole problem with controlling fundamental constants. It has to be a local effect or you break the universe. If you can screw around with fundamental constants locally, then you simply make curvature of the distortion field arbitrarily great.

Adding the magnet can alter the baseline state of the system but it cannot continuously maintain a temperature difference to function as an endless heat sink. The reason a magnet doesn't work is because of the same reason the Brownian ratchet doesn't work. A magnet will have a continuous field, and so even though the orbitals on one end will be strengthened and orbitals on the other end will be weakened, the continuity of the field means there is no actual point where the more energetic particles are induced to cluster more on one side than the other. On the other hand, if you have a system where you have shifted the parameters in both boxes with an actual discontinuity at the center (and only at the center) then you will have the endless heat sink effect. If it was possible to construct a magnet with a discontinuous field, then building an overbalanced wheel would be trivial.

BE-4 doesn't need subcooled propellants to reach its highest performance levels. BE-4 runs at lower turbopump pressures and thus may be more readily reusable than Raptor. BE-4 has a single turbopump rather than two turbopumps and therefore has fewer failure modes. Of course all these are trade-offs.

The best explanation for light speed ramming, I think, is to suppose that the mass budget for missiles is better used for packing hypermatter warheads than anything else. All of the engines in Star Wars are supposed to run on hypermatter. So while it would be theoretically possible to build a missile that functions on light speed ramming, it should actually deliver much more energy by simply using the same mass budget for a hypermatter warhead. The only reason that Holdo was able to cripple the Supremacy using light speed ramming was that the Raddus was an enormous ship.

All SW ships, even the very small ones, have repulsorlifts which act only along a gravitational gradient but consume very little energy. So the ion engines are only used for flying out of the atmosphere or flying back down into it. And there's no orbiting, either; you just fly out of the atmosphere and hover up there. Hyperspace drives are for moving large distances through space. Of course they sort of broke that in TROS when the Falcon was lightspeed skipping, but I suppose it did a lot of damage to the ship so there's that. You can tell this is the way it's all conceptualized. In Revenge of the Sith, General Grievous sabotaged the Invisible Hand and hopped out in an escape pod, leaving the ship to plummet toward Coruscant. If it was in orbit, it would have remained in orbit. You can also see this in Rogue One during the Battle of Scarif, when three Y-wings disabled the engines on the Persecutor, causing it to suddenly begin dropping. Its backup generator reactivated the repulsorlifts, but the Lightmaker was able to push it into the Intimidator and all three ships subsequently dropped like stones directly into the Shield Gate, destroying it. Finally it's also visible at the beginning of The Last Jedi during the bombing runs; the bombers all attempt to fly over the Fulminatrix in order to simply drop their bombs but only the Cobalt Hammer manages to release the bombs before being destroyed. Once it does so, however, the Fulminatrix begins to explode and it immediately starts to plummet. If the ships were in orbit; dropping the bombs would do nothing. This also means that there typically isn't actually antigravity being used. If you had a repulsorlift and could hover above the surface of a planet, you'd still be subject to gravity whether you were in the atmosphere or not.