sevenperforce

For a perfectly circular ring of twenty 1.3m engines that are welded bell-to-bell, you need an outer diameter of at least 9.58m. You can, as you show above, reduce the diameter by insetting the engines. If SpaceX forgoes the skirt altogether there MIGHT be enough room for gimbal at the center but it would be super tight.

Starship is 9m standard and I believe the official renders show a 10m skirt. He says the outer ring are fixed and do not gimbal at all. So you only need space for TVC in the middle. They want a LOT of control authority on Starship, so we could conceivably be looking at 10 degrees or more in any direction, and they wouldn't do different engines on the booster. Do you mean centimeters? Or are you talking about something different?

Yeah, I truncated the leg length intentionally shorter for the sake of showing more detail on the inner engine arrangement. My larger curiousity is whether they will inset four engines in order to place the reinforcement for the legs further inside the skirt. He referenced an "outer ring" but the above configuration would certainly qualify as a ring, I think. I also wonder whether the inner engines will be in a pure ring a la N-1 or a configuration more like the one above. He said they will only need two engines for the initial hop tests, which suggests it can land on 2-3 engines easily enough, so you'd think they would put them as close to the center as possible. Also, it has more gimbal range than a pure ring. They could also do a 2+6 configuration, with two inline engines at the center and six in a ring around them.

With a 10-meter skirt, four legs, and 28 engines, I wonder if we end up with a configuration that looks like this: Congrats on having the first post of page 1000!!!

If it was in fact impossibly rigid it would probably go right through you without noticeably interacting. If it was not impossibly rigid it would shred at the slightest touch.

IKR? People think the combustion chamber is the crazy part, but first you need to get the propellants to an even higher pressure for injection! In a FFSC engine, yes. For a GG cycle, I believe the highest pressure is usually in the chamber (or at least in the chamber inlet); the GG pressure drop is used to mechanically drive the turbine that pushes the propellants into the chamber. The FFSC engine uses the pressure drop from the preburner into the chamber to drive the propellants into the preburners! Dear god in heaven

Well technically you can "move" a 1 ly bar with any impulse at all. It just won't move very fast. As far as the minimum...assume an impossibly rigid steel "bar" one single atom thick (that's the minimum) and one lightyear long. Metal-metal bonds are on the order of 1.6 angstroms, so we're looking at 5.84e25 atoms, or a "bar" weighing about 5.42 kilograms. Lots of good answers have been given already, but I just have to say that I really like this question and I'm glad you asked it! Keep it up.

Brains (or any other information storage and retrieval mechanism capable of evolving intelligence) are VERY metabolically expensive. They take a long time to grow and therefore they become so very valuable that they must be protected at enormous metabolic cost. So while intelligence itself can subsist on very low levels of energy, you're right: you need ENORMOUS selection pressure to evolve an intelligent brain, and therefore you need a very large ecosystem, able to support ongoing competition for resources.

I have an odd problem. I cannot build a Blok D that looks right without emptying tanks, or it will have too much dV.

At 20:38 in the SAOCOM 1B launch, is the white dot on the S1 view the moon, or the second stage? Amazing to see the two fairing halves separating from the ground tracking cam, though. And absolutely fantastic view of the vapor shock formation during transonic phase. You can really see why grid fins are so effective. Those single-engine-all-the-way-down burns are shockingly long.

Not to mention the extremely draggy interstage and the mass of landing propellant (which is forced down by drag acceleration). Plus hot-gas thrusters to help the grid fins do their thing. And having only four rather than six.

Thank you! Up until the Making History expansion, decoupler colliders were solid. Back then I would invert a decoupler (so that it dropped what was under it without detaching) and then attach a hollow piece underneath it if I wanted to do a fire-through parallel stage (e.g. Atlas-Mercury). But post Making History the decouplers have been hollow even though I think the hollow is a square and not a circle. The panels are in 6x2 symmetry. Made it hard to attach the landing legs but I managed. The landing ladder even deploys using a hinge.

Whoa. They only need TWO ENGINES to do hop tests for Superheavy. Is this the first regeneratively-cooled vacuum nozzle? Other than the SSME, which was an altitude-compensating nozzle.

Couple more WIP shots. I think I am happy with the LOK and LK now. Time to start working on the Blok D stage.

My latest one actually uses two clipped Mercury capsules with a fairing and no soviet-style capsules at all but we will see how it goes!

I will never not cringe at the landing gear. It feels so small!!!!

I went back to the drawing board and let's just say I am having entirely too much fun with this. Fully actuated rotating and extending telescoping boom for crew transfer. It is impossible to EVA from the re-entry module; you must transfer to the orbital module first. There is a vent to dump monopropellant after the drogue deploys. The heat shield is jettisoned after the drogue deploys and there are four solid fueled thrusters underneath it to soften the landing. No reaction wheels on the re-entry module; the thrusters (not shown) are set to provide roll control only in order to steer through the skip re-entry.

Nebula EVA Handrails You can’t get in and out of a command chair from a ladder, but you could potentially put the ladders sideways to translate and produce a different animation.

This uses hella mods but wow is it cool:

It's blurry, but it looks like they did use a basic carabiner to transition. The closer photo looks really really good. That is definitely a telescoping rod...you'd clip a carabiner to it and just slide along it. So in the cutaway, the telescoping rod is actually at the bottom right, not the top left. I think I may keep the LK design but rebuild the LOK from scratch to make it look more like this one. Interesting how they had the transfer rails along the top as well. Recall that the LK-LOK never did the "flip and extract" maneuver of the Apollo CSM, so the cosmonaut would have to EVA down across the service module to enter the LK, then would climb along the front/top of the LOK after docking post-sortie. I wonder what all those spikes are at the transition between the re-entry capsule and the service module.

That looks REALLY good.

I think this is a very big factor. One single engine is more likely to produce high jerk transients, with a lot of sudden acceleration associated with gimbal and throttle variation. What human beings perceive as a roughness is not actually peak acceleration, but the rate at which acceleration changes. We can handle a lot of acceleration as long as it does not happen suddenly. There are no perceptible start up transients for the Falcon 9 first stage, because all the engines are lit on the pad. Small variations in pitch and yaw are done with multiple small engine gimbal movements, and are further damped by aerodynamic forces and the overall size of the stage combination.

I wonder what the spacewalk procedure was. I’m guessing a series of carabiner clips placed on the boom prior to LOK egress, transferred down gradually, and then removed after LK ingress.

I mean you would need a LOT of engines shutting down.

Yes, I think you are right. I will probably replicate it using simple deployable ladders because I suspect using pistons and ladder sections would be too heavy and too bulky. I wonder: what is that shroud that goes part of the way around the base of the flared portion of the service module?