Jump to content

zolotiyeruki

Members
  • Posts

    794
  • Joined

  • Last visited

Everything posted by zolotiyeruki

  1. What we'all are saying is that SpaceX have a history of taking ideas that sound a bit on the far side of crazy to doubters like you, and then making them happen, while you consistently post doubts that appear to be founded on nothing but intuition. The shoulder analogy fails on even a superficial level. It'll be a hinge, not a ball and socket joint. It'll be made from steel or titanium, not bone and cartilage. Super heavy can hover, or nearly hover, when empty, while the human body does not have that ability. The catching tower will have shock absorption, if not outright active suspension, while the steel beams in your analogy do not.
  2. I can answer that. Airliners are typically pressurized to about 8,000 feet. That's a high enough pressure to keep everyone alive and cogent (10,000 ft is where some people start getting hypoxia), while decreasing how much pressure the fuselage has to maintain. Atmospheric pressure at 35,000 ft is about 3.5 psi, at 8,000 ft it's about 10.9, and at sea level, 14.8. Instead of withstanding (14.8-3.5 = ) 11.3psi, the fuselage only has to hold up to (10.9-3.5=) 7.4psi.
  3. I would argue that catching fairings in a net *did* work. SpaceX just came to the conclusion that making the fairings water-tolerant was a better approach. Even if the Merlin engine wasn't originally designed for relight, I'd be shocked if its design hasn't evolved to better facilitate relight. And Raptor's failures on landing have generally been the fault of the fuel tanks, rather than Raptor itself.
  4. You're right that ULA would likely have to do a whole bunch of redesign in order to recover their boosters, but I wouldn't call SpaceX "lucky." Reusability was a primary goal from Day 1 for Falcon, and a whole lot of engineering (and money, and explosions) went into making that happen. As a disposable launch vehicle, F9 has been pretty doggone reliable from the beginning.
  5. When engaging in this sort of debate, it's helpful if you have a similar historical situation to refer to by comparison. ...and we do, at Cape Canaveral, where the ecosystem doesn't seem to be terribly bothered by the presence of the world's largest rocket launch complex. Also, six acres is a drop in the bucket compared the size of the area it's in. Pull it up in Google Earth, and you can see just how small a footprint the SpaceX facilities are. Also also, if SpaceX blow up a starship prototype, they scatter liquid oxygen, liquid methane, (or maybe a whole lot of CO2 and straight carbon), and stainless steel, plus a tiny fraction of other materials. With the exception of the "other materials," the local ecosystem isn't going to care--methane and oxygen evaporate, stainless steel isn't going to taint the environment, and the rest of the stuff is generally at the back of the rocket and stays on or near the crash landing pad.
  6. It reminds me of the short story Superiority by Arthur C Clarke.
  7. "Heavy" and "Super" are terms used by Air Traffic Control when referring to particularly large aircraft--"Heavy" for aircraft over 300,000 lbs, and "Super" for two types: the Airbus A380 and the Antonov An-225
  8. I didn't see anything there about the duration of the first stage burn, only that SpaceX are basically going to keep reusing boosters until they break.
  9. Is it normal for the 1st stage to burn until 2:35 or so? I was under the impression that MECO is usually around 2:20.
  10. If a hypothetical dragon landing burn failed, wouldn't the landing legs be moot? I mean, if a capsule impacts at terminal velocity, I don't know that having the landing legs retracted is gonna save the occupants. Ah, I suppose if you had a mostly-good landing burn and the engines started just a bit late or cut out just a bit early, but that seems like a pretty narrow risk probability. Although I supposed Starship is proving me wrong, here.
  11. The "cg toward the nose" is applicable if you're 1) in the atmosphere, and 2) intending to fly nose-first. Neither are true on the moon. The concern about CG on the moon is a valid one, though-- the SS prototypes up to this point have all been landing very tail-heavy, with nothing but empty space and a header tank in the nose. On the moon, there won't be a need for a header tank in the nose (no bellyflop), which should help shift the CG toward the engines, but it *will* have a whole bunch of cargo in the nose, which will shift the CG way up.
  12. "so ever-freaking close" is right. Honestly, the engines are doing pretty well, as long as they're properly fed. Sure, one caught fire on SN11, but SpaceX are iterating so rapidly that they can handle failures and slipstream the fixes into later models. Contrast this to SLS, where it absolutely has to work perfectly the very first time. That rapid iteration really synergizes well with their design--welded sheet metal tanks/fuselages are cheap. Their goal is $250k per Raptor. Let's say they're at $2m right now. For a couple dozen million dollars, tops, they're getting to basically test the entire spacecraft through just about every regime, from launch to hover to flop to descent to flip to hover to landing, all in actual real space under real conditions.
  13. The shuttle had a lifting body and wings because 1) one of the requirements was for 1000 miles of crossrange capability, i.e. it could land anywhere within 1000 miles of its intended target, and 2) it needed to be rapidly reusable (which never happened), and a horizontal landing had the potential for minimizing how much refurbishment was required before relaunch.
  14. If you're going to catch SS in a net, you could also add parachutes to slow the descent. Since stopping distance is proportional to the square of the starting speed, assuming constant deceleration, dropping the terminal velocity, say, in half would reduce the stopping distance by 75%. The approach seems a bit odd to me, given SpaceX's decision to scrap a similar approach with the fairings. Of course, the fairings have a much lower vertical velocity, and are presumably much more susceptible to wind, and SpaceX have figured out how to fish them out of the ocean without damage. I *would* be concerned about potential damage to heat shield tiles with a Giant Net approach. How much lighter would SS be without the propellant needed for the flip, hover, and landing? How much would that affect its terminal velocity?
  15. Is there a corrosion issue with storing LOx in a mild steel tank?
  16. So....no big net to catch F9 fairing halves, but yes to a really, really big net for catching SS? That's gonna be somethin' to watch... WRT the tanks, it might also just be a matter of "Hey, the welding crew has a couple days with nothing on the schedule. Since we're paying them anyway, why don't we get them to build us a GSE tank?"
  17. It may also be an issue of delivery timing. With the pace of fabrication on-site, SpaceX may have realized that, setting cost aside, it would be faster to build their own tanks than to bid it out, select a supplier, wait for the supplier to get the materials, fit it into the supplier's schedule, and then somehow ship a 9m-diameter tank across some distance. Time is money, after all, so even if it ends up being more expensive, they'd get it WAY sooner, and wouldn't have to worry about the specs/requirements being misinterpreted.
  18. Well, I suppose all the accoutrements could be packed into the payload section, as you'd do with a moving truck, and then unpacked into the larger volume once it's in orbit and the fuel has been vented. It'd be a bit like building a house from the inside.
  19. I LOVE the idea of using spent SS's as a space station, but question the cost. I mean, the whole raison d'etre of Starship is reusability, which entails bringing it back down to earth to save money. If you just leave it in LEO, that sorta defeats the purpose. Is there a way to loft large, empty vessels into orbit AND bring SS back to earth? Deployable somethings like that inflatable module they put on the ISS? Some way to decouple the engines and avionics from the tanks, and then recover the expensive bits? Or, since they're currently just disposing of F9 second stages, maybe they could modify that design so it could dock with some sort of truss, and the F9S2 tanks could be finished into hotel rooms. Eh, if you're going through that much trouble, it'd make more sense to just load four cylindrical, purpose-built, pre-finished hotel room modules into a SS and launch 'em that way. Or just design your new space station to use 8m-diameter modules, and launch 'em on SS.
  20. And the LOX header tank in the nose shifts the CoM higher, away from the engines, making the gimballing even more effective
  21. Given that they're planning to land on 1-2 engines anyway (i.e. center of thrust is offset), plus the gimbal range, I'm not particularly concerned about the small shift in CoM due to the tiles. Besides, if you double-hull the windward side, that would shift the fuel leeward, but you'd be adding a whole second layer of stainless steel on the windward side, too, therefore adding more weight where you don't want it.
  22. Hehehe, this can be interpreted at least three ways off the top of my head, and all of them are gloriously humorous!
  23. I'm not terribly concerned about the "landing between towers" issue, because: 1) The towers are likely to be removed. They were originally designed for drilling oil wells, and are unlikely to be suitable for SpaceX's operations. In fact, very little of the existing topsides equipment and structure are likely to be useful. These rigs are going to get stripped down. 2) F9 landings are remarkably accurate, and I believe the same will become true for SS. Heck, with their two attempts to date, they've already been really close. 3) Any new towers could retract a la F9's strongback 4) OCISLY endured multiple hard landings. Sure, SS/SH will be dramatically heavier, but the fact remains that you can build a structure to take it.
×
×
  • Create New...