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Everything posted by sevenperforce

  1. Yes, but it's generally hard to get at. Oh, I have no idea. I just imagine that some particularly clever inorganic chemist might be able to come up with a crystalline microchip design which would be able to substitute for precious-metal-based microchips. For example, imagine some microchip that needs platinum or gold in order to work. Pure silicon is a semiconductor, while silicon dioxide is an insulator. It's possible that you could design some sort of silicon+silicon dioxide crystal structure which would provide the same functionality as the platinum or gold microchip, but without needing the platinum or gold. It's also possible that such a structure would require microgravity in order to grow.
  2. Mildly off-topic -- my ex moved our kids to a house without internet service (long story lol) so I promptly ordered Starlink for them. It says they are targeting mid to late 2021 for this service area (rural Virginia) which I believe ought to be now. Has anyone else used Starlink or does anyone else have an idea of what the turnaround time is like?
  3. A killer app for off-planet manufacturing would be the production of microchips and other tech components without the use of precious metals. We are running low on our reserves of palladium and nickel and copper and so many other metals. If someone comes up with a way to grow silicon crystals in zero-gravity that will replace those tech components without the use of rare metals, THAT will be huge.
  4. I thought that, but the aircraft were clearly at max altitude and the loops were easily 80-100 miles in diameter. I can’t imagine why they would be in a holding pattern at cruising altitude. But maybe that’s something that happens.
  5. Hey, so I was in DC watching the sky lazily and spotted an aircraft making an extremely wide turn at around 35,000 feet. It was heading west towards DC but performed a full loop headed back out toward the Atlantic. Kept watching and saw two planes basically making one single loop with the western edge over the Chesapeake and the eastern edge over the Atlantic. Both aircraft were white and generally appeared to be commercial, but I suppose they could have been AWACS or something. They both did two full loops before disappearing over the horizon for good. Any idea what this could have been and why?
  6. I believe the only reason that worked was because they were doing a fit check. They had no way of detaching the LR13500 from the top of Starship. None of the worker lift baskets go that high. Once they are actually ready to launch, they will want to use the chopstick arms to lift and place Starship. That way, they can finish tiling the nose cone while it is still close to the ground. Current rumor is that there are lift points in the sides of Starship 20 which will not need any independent thermal protection because they are recessed. Agreed. Although I would’ve expected them to do booster fit checks with the QD arm and B4 right away, before adding the chopsticks.
  7. Also keep in mind that the catching infrastructure is double-duty. The chopsticks provide a landing mechanism for Superheavy, but they are also used to stack Starship. So they need to be operational in order to have an actual launch at all, even though B4 is destined for a watery grave.
  8. If lower cost and just a taxi is not part of the requirements, it's the same requirements, except for the "sustainable" part. Meaning sustainable and 4 crew being mandatory. The alternative requirement/need might be something like "low-mass space taxi and lifeboat independent of SpaceX". As powerful as the SpaceX system is, it does depend on a large Earth/LEO infrastructure, and so if we are going to have a sustained crew presence on the lunar surface then it would be a good idea to have an independent contingency system in place.
  9. Really good point on the capsule doing the maneuvering. However, pointing is still an issue. The camera would need a reaction wheel. I mean, I suppose they could simply toss a single starlink into the trunk and use that.
  10. NASA will now allow crew to be launched on both reused capsules and reused boosters. However, the heat shielding will be replaced between each flight, so the capsules will look brand new each time. The bottom of the capsule is not the only heat shield; the aeroshell also has ablative shielding. They were originally planning on using PICA-X for Starship back when it was still going to be carbon-fiber. It would have eroded over time but slowly, at least for LEO fueling flights. Starship is much fluffier than a capsule so the load on the heat shield would have been lower. But once they switched to stainless steel, the acceptable substructure temperature came way up, meaning that they could afford to use non-ablative silica tiles which weigh much much less. This approach is more like the “hot structure” plan for Dyna-Soar.
  11. Probably from this article... https://www.airspacemag.com/space/is-spacex-changing-the-rocket-equation-132285884/?page=2 “In fact, says Musk, a single PICA-X heat shield could withstand hundreds of returns from low Earth orbit; it can also handle the much higher energy reentries from the moon or Mars.” This was a long time ago and was in reference to the heat shield on Dragon 1. Probably some light exaggeration here by Musk. Presently, crew dragon and cargo dragon heat shields are single-use, not because they could not be reused, but because saltwater incursion tends to ruin them.
  12. Agreed. They’re hitting the water at 15 mph; the capsule is going to displace approximately half its volume in water and the displaced water is going to be ejected tangentially at impact speed. This looked substantially the same as past Crew Dragon landings as well as Apollo landings.
  13. Looks like a golden retriever, heralding some children's hospital mascot.
  14. Are these what the "tank treads" have become? Perhaps instead of tank treads they are going with this lego-like rail filled with holes for pegs, that could be actuated to slide back and forth along the top of the chopstick arm. Having those mounts wrap all the way around the tower does seem cool. However, I'm still a little concerned about the placement of the lift point. The cable lift point needs to go through the arm rotation axis, IMO.
  15. Oh, I agree. I'm not saying that we know for sure that the drag while folded is greater than the drag while extended. I'm just saying that it's clearly close enough to the balance point that the added weight of a folding system wouldn't be worth it. Also, drag on ascent is fairly low, all things considered. Grid fins are draggiest during the transonic regime due to shock interactions, and the transonic phase on ascent is at a very high altitude.
  16. Remember that there are three engines at the very center of Superheavy. Those three engines can control roll by differential gimbal with pinpoint accuracy. No worries at all. Unlike Starship, which needs to drop to two or even one engine at landing, Superheavy needs all three engines to land and so it has AMPLE yaw, pitch, and roll control at the moment of catch. A curved catching claw wouldn't solve the problem unless it was itself able to rotate around a plane. Grid fins have a pretty substantial chord length by design (that's how they function, after all). Fold that chord over by 90 degrees, and you've got a very draggy object clinging to the side of your rocket. The grid fins are constructed of relatively thin stainless steel. Their cross-sectional area when deployed is not very high; it's their rotation (increasing the AoA into the airstream) which offers control authority. Their cross-sectional area while folded is probably close to or higher than their deployed cross-section, and so the added weight of an actuation system would only be parasitic. Imagine holding an empty toilet paper tube out your car window with the hole pointed into the airstream. The air will flow through the hole and the drag will be minimal. If you now turn that toilet paper tube sideways, the drag will be much greater. The same will be true of two dozen toilet paper tubes all glued together (which is basically what the grid fins are).
  17. We know the chopsticks will catch the booster by the pegs. No need for a claw. Also, you don't want a circular claw anyway, because that results in fewer degrees of freedom. Parallel chopsticks can catch the booster anywhere as long as it comes down between them; a circular claw can only catch at a single point in 3D space. The lift point remains a thorny problem. You need the rotation axis of the chopstick arms to be directly under the Drawworks cable lift point. So it HAS to be further out than that.
  18. Here's my latest render for how the new arms could connect. If we assume there are yet-unseen hinges at the rails and at the points where the W-shaped system and its arm extensions are currently welded together, then the entire blue frame can rotate while keeping the chopstick-arm attach point substantially underneath the cable lift point of the Drawworks. It looks flimsy, but if the cable is lifting the whole assembly, all the blue frame is really providing is stabilization. The actuators simply rotate; they aren't load-bearing at all. Also depicted is the hypothetical tank treads to translate the booster catch pegs. Full image here. Wow. That's just absolutely gorgeous. I ream really, really liking the tile work across the top of the cowling on the forward eloneron. We know they can use the Frankencrane to stack Starship on top of Superheavy using those load points, but there is no lift truck that can reach the top of Starship when it is fully stacked. I don't know whether Frankencrane is human-rated or not; if so, they could dangle a work platform there so that workers could remove the load hooks and glue on the remaining tiles (but that seems super sketchy). I'm very curious about the missing tiles underneath S20's forward elonerons. It seems like that might be a place to attach lift pegs similar to the ones on Superheavy. If so, then they can remove the load hooks and finish the heat shield while S20 is still on the ground, then wheel it over to the launch tower and use the chopstick arms (once installed) to lift Starship on top of Superheavy. They'd just have to expect the lift pegs to burn off on re-entry. Elon has said they need the QD arm fully installed and functional in order to properly stabilize Superheavy during the final stacking for launch (and to provide propfill for Starship), but I don't think he has said for sure whether the chopstick arms are required. If Frankencrane is human-rated then maybe they will leave the chopstick arms off for the time being and just launch that way.
  19. Nope, the QD arm is at the production site and still horizontal . That's the section with two of those V placed a few meters apart that should go parallel to the tower Whoops, yes, you're right; I see that now. Yes, looks like it.
  20. Are you sure? That looks like the QD/stabilization arm extension.
  21. Yeah, I doubt the orbital launch table can handle 29 Raptors without a water deluge. Of course, that doesn’t mean we can’t have a water deluge installed in the next week.
  22. They are the same HFSI aerogel-esque silica-based ceramic that the Shuttle used, except thinner, tougher, and with a different waterproofing chemical. Most importantly they are (mostly) mechanically-affixed rather than glued on, which solves most of the Shuttle tile problems.
  23. They’re not TUFROC but otherwise yes I agree.
  24. This was my render from the beginning of August predicting a tank-tread mechanism to translate the booster via its catchpoints: This was back when we thought the arms were actually the sliding tower frames, but no matter. You can see how the tank tread mechanism operates: a sloped section to drop the catchpoints between one of the teeth, and then teeth that rotate around in a loop to move the booster forward or backward.
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