sevenperforce

Separation takes place high enough that aerodynamic effects are minimal.

My best guess is that we see an overlap joint where the TPS on the fixed skin/chine extends out a few feet to cover the seam, leaving a gap. It's going to be difficult for them to get Starship anywhere close to orbital speeds without achieving full orbit, too, because they need to get back to Boca Chica. They can't do a half-speed EDL because that would put the Starship landing zone off the coast of Africa. And I doubt Starship would have enough dV for a sufficiently high-energy boostback.

Trouble with using "properties of the body in question" is that we end up with a bunch of planets orbiting Jupiter and Saturn. But I agree that "clearing an orbit" is a hackneyed test, because it has the same problem. If you apply Jean-Luc Margot's planetary discriminant Π to a moon like Ganymede, it receives a score of 3.2 making it indisputably a planet (though less of a planet than Mars and much less of a planet than Mercury). Even Titan receives a Π score of 1.4, so it is a planet too.

I agree. If you transported Mercury to the outer solar system it would cease to be a planet. Then again if you transported Earth to an orbit of Jupiter it would also cease to be a planet and I expect we are all okay with that. Pluto, Eris, Makemake, Haumea, and other TNOs should not be planets because their orbits are dominated by the influence of Neptune. Ceres and Hektor should not be considered planets because their orbits are dominated by the influence of Jupiter (and, in the latter case, because Hektor is not large enough to be gravitationally rounded). I think we should define planets based on their relationship to other solar system bodies, not based on a function of their size and semi-major orbital axis. Spherical bodies in orbits with high eccentricity or high inclination like Sedna and Biden could be classified as "irregular planets". I can get behind this.

I wonder what their odds calculations on booster-capsule recontact are like. And what type of separation mechanism they use.

!!!!! wow that's dark

My efforts multiplied the signatures by 4x and I was able to reach out to the company. They told me to tell my son that they probably won't bring the Lost Island back but it's in dev right now so there's a chance. And they gave him in-game swag and sent him a free t-shirt so he is ecstatic.

How exactly did the shuttle solve this problem? The rudder was completely in the leeward side of the vehicle during re-entry but the aft control surface seams experienced some of the highest heat fluxes anywhere on the vehicle. Squid fins!!

Why? You can define antigrav anyway you want. I am pretty darn certain that grappling asteroids and using them to provide RCS via laser ablation thrust will NEVER be the most efficient option for RCS.

It is a dwarf planet just like all the other Solar System bodies which are large enough to be gravitationally rounded but are not large enough to clear their orbit around the sun.

The gas-gas RCS thrusters on Starship will have three times as much thrust as the Kestrel rocket engine on the Falcon 1. By your standard, Starship is "too heavy". The primary RCS thrusters (not the OMS engines) on the Space Shuttle Orbiter produced 7.8 kN of thrust...more than the upper stage of the Juno I booster that launched Explorer 1. By your standard, the Space Shuttle is "too heavy". The R-4D RCS thrusters used on the Apollo lunar module produced 490 N of thrust...more than four times the thrust of the engine on the Electron's upper stage. By your standard, the Apollo lunar module was "too heavy". And as @Scotius pointed out, a civilization with antigravity is going to have no trouble coming up with attitude control SLIGHTLY more refined than pushing compressed gas out of a tube. In a sci-fi world, a spaceship is precisely as large as it needs to be. Remember that the square-cube law always favors larger vehicles over smaller ones for pure performance (although you might want smaller vehicles for other reasons).

Now THAT is a %$#@ money shot.

If you want an analytical equation of state, you're going to need to know atmospheric density. Density is a function of altitude. In your equation, altitude is going to be equal to displacement, which is ultimately a function of velocity and time. You're also going to need to know the coefficient of drag for your rocket. That's difficult because the drag coefficient is velocity-dependent, so you'll either need to take an approximation and treat it as a constant or you'll need to use a discontinuous function.

Exactly. You run into air just as catastrophically as you run into rock. Compared to a vacuum, air is just as dense as a rock. It really depends on the type of teleport mechanism you use. If you are forming a superluminal path through space that displaces whatever is in your way, you have one set of problems. If you are folding space and swapping the destination atoms with your body, you have a different set of problems.

Rockets often have stubby noses because they spend very little time in dense parts of the atmosphere during supersonic flight. A supersonic fighter jet needs low drag for sustained level supersonic flight.

I don't understand -- what do you mean?

This is the fun bit -- the Coulomb force is MASSIVELY powerful. Calling it "nuclear energy level storage" doesn't even come close. If you took just 4% of the electrons out of a potato, it would have a specific energy density of 2e20 J/kg, making it 25 MILLION times more energy-dense than the most powerful thermonuclear bomb ever detonated. Take all of the electrons out of a potato (or any chunk of matter) and the specific energy becomes 220,000 times more than the specific energy of PURE ANTIMATTER. Obviously it is nonsense to imagine an energy storage mechanism which contains more energy than the mass-energy of the storage device. In fact a 180 gram potato with all the electrons taken out of it would lose about 16 milligrams of mass (from the lost electrons) but would gain about 40 tonnes of mass due to the Coulomb mass-energy it contained, making it approximately 7% as dense as a white dwarf star. I agree. White dwarf material comes from dead stars -- exoplanets don't get that dense. A white dwarf is 10,000 times denser than lead.

In the image above you can see its fins articulate. I believe there was a video a few pages back of a fin articulation test. They flap quite merrily.

I know the fairings are huge, but man, they are huge.

All of this nonsense about metastable metallic hydrogen reminds me of something I once heard about electrons and protons. It was remarked to me that if one were to remove the electrons from a single potato, the Coulomb force between all of the protons in that potato would result in enough destructive energy to blow up the moon. It seemed awe-inspiring and almost unbelievable. But how would one actually go about that? You can’t just “delete” electrons. The Coulomb force between electrons and protons is the very thing which keeps matter solid. Even if you set aside the ionization energies of all the atoms in all the molecules in the potato, the act of removing all the electrons from the potato one by one would require exactly the same amount of energy that would subsequently be released. Each electron would be harder and harder to pull out due to the growing positive electric field and the nucleon cloud left behind would become more and more difficult to contain. There is no free lunch. Imagining that we’ll have metastable metallic hydrogen energies is like imagining that we’ll be able to levitate by “simply” pulling pockets of air underneath ourselves and hovering on them. "Yes, if you could do something you cannot do, then you could do something you cannot do." Welcome to the tautology club.

The MVac pushes 348 seconds of specific impulse; 311 is the sea level version in vacuum. But I think your math is off. At 311 seconds you'd need 3,286 tonnes of propellant for a 10 m/s reboost; at 348 seconds you'd need 2,937 tonnes. But more to the point, a civilization capable of building a million-tonne space station would be reboosting it with something a hell of a lot more energetic than kerolox. One VASIMR concept was originally envisioned for reboosting the ISS. VX-200 had a specific impulse of 5000 s. A million-tonne space station would have gigantic power requirements anyway so it would make sense to have scheduled brownouts for allocating power to the onboard VASIMR for reboosting. A more realistic 5 m/s boost to a million-tonne space station would require 102 tonnes of VASIMR propellant. @sevenperforce, that's your cue. The reason metallic hydrogen gets everyone excited is that it's monatomic rather than diatomic. In other words, you can essentially burn it with itself and produce diatomic hydrogen with a huge energy release. Yay! But there's simply no evidence that metallic hydrogen can exist in a metastable state at meaningfully low pressures. All the maths that show a workable metallic hydrogen engine simply assume that it could conceivably be. For example, the 2010 Harvard paper that got everyone excited about it said, "We assume that metallic hydrogen is a metastable solid or liquid at ambient conditions, that it is compatible with launch vehicle propulsion environments, and that it can be safely and affordably produced and handled in large quantities." That's a hell of a lot of assumptions. It's rather like saying "If we could compress plasma from the core of the sun and store it at room temperature then it would be a very good way to cook food." I mean, yes, but that's not really helping us. In some models, metallic hydrogen can form at several hundred GPa but remains metastable to 10-20 GPa. And while that may seem like a huge jump, it doesn't help us, either. The 643 bar pressure inside Raptor's CH4 turbopump is just 0.0643 GPa. The physics of metallic hydrogen simply do not allow it to remain metastable at pressures achievable on a macroscopic scale.

I mean, I suppose if you have ENOUGH water pouring out at the bottom then you should be okay. The Saturn 1B was high enough on the milkstool that its interaction with the flame diverter was minimal. We're waiting on Word of Elon again, I guess.

Gimbal won't be enough to do the trick under abort circumstances, but differential thrust might. There's a bit of a dV problem. Of course, with a landing failure, you don't need quite as much dV. Full-envelope abort for Starship would have quite a few different modes: Pad Abort. Triggered by S2 failure before launch. Needs high thrust to be clear of the fireball; needs to boost far enough to be clear of pad debris; needs reliable landing mode. Max-Q Abort. Triggered by S2 failure at approximately Mach 1. Needs high thrust to be clear of the fireball; needs reliable landing mode. Terminal Abort. Triggered by S2 failure outside of atmosphere. Needs passively-stable re-entry capability; reliable landing mode. Entry Abort. Triggered by heat shield or aft flap failure during re-entry. Needs high thrust to be clear of debris, passively-stable re-entry capability, reliable landing mode. Landing Abort. Triggered by aft flap failure or relight failure. Needs highly controllable thrust to clear debris, reorient, and boost far enough to be clear of impact debris; needs reliable landing mode. Then the landing mode impacts more stuff. If you're going to be using chutes, then you have to make sure your landing abort boosts you high enough to use them properly. If you're going to be using thrusters, that means more dV. My guess is that a severed forward payload compartment with the canards folded halfway would be passively stable in the correct orientation for re-entry, but I don't know for sure. You certainly don't want it to lawn dart.

Dammit. Then again, this is why they test.

It makes a LOT of sense to have this kind of crew variant, but there are a lot of challenges. For one thing, they can't use the header tank with the gas-gas thrusters. I had speculated upthread about whether the meth-gox thrusters would use accumulator tanks which also fed tank pressures. I also suggested that if they did use accumulator tanks, they could easily modify the baseline Starship model -- more accumulator tanks for longer on-orbit persistence as well as for the lunar landing version. Such a design would also permit the development of a dedicated launch abort system: throw extra accumulator tanks in the payload section and hook them up to extra meth-gox thrusters. Additionally, because Starship is designed to fly rapidly and reusably, you don't have to worry about your payload section having independent lifeboat capabilities a la Crew Dragon; if there is a non-catastrophic on-orbit failure it is easier to just send up a replacement Starship. Some problems, however: The forward canard-flaps make the payload section aerodynamically unstable. They'd either need to add pop-out grid fins (like the Soyuz LAS) or figure out a different way to feather the canards. The separation system becomes a new failure mode -- you really don't want the separation system to fail, but you also don't want it to trigger or otherwise initiate at the wrong time. It's nice to not have to worry about lifeboat capability, but will it be able to survive a failure during entry? What if the aft flaps lock up? What if the forward canards lock up? One of the really unpleasant failure modes for Starship is an engine relight failure at the moment of the kick-flip. In that situation, you're dropping toward the ground at 60 m/s and firing your LAS would only propel you sideways, not vertically. How do you deal with that? What's the landing mode -- giant chutes? Independent thrusters? A gliding splashdown on a steerable chute like the fairing halves?