zolotiyeruki

Most people don't realize that charge dissipation is actually a lightning rod's primary method of protection. Charges like to congregate on a sharp point, and that makes it easier for them to hop off into the air, reducing the potential between clouds and ground. If it doesn't work out, then yeah, the cables provide a current path to ground.

What's the status of SpaceX's R&D for producing fuel on Mars? An offshore launch pad, with nearby floating solar/wind farm (free real estate!) might be an interesting test bed.

Yeah, I noticed the (significant?) difference in separation time between the two boosters. I suppose it helps keep them from knocking into each other on the way back to shore? That was super, super cool to watch, and the camera shot from the lagging booster, showing the leading booster's landing burn, was sweet!

Here's a guess about the lower part of the image: the part near the checkered line looks a little like a game of Snake, or a spaceship dodging asteroids or maybe going through some sort of hyperspace gate, or getting multiple gravity assists from planets. Or maybe the checkered line symbolizes a finish line, a race perhaps? Maybe Kerbin is going to blow up and you have to resettle the entire species to another solar system before you run out of time?

Yeah, it totally looks like it's going to miss. It doesn't help that they *aim* to miss until after the landing burn starts and everything is nominal. At that point it adjusts its trajectory to land on the ASDS. The trajectory for RTLS is very different from a droneship landing--an RTLS launch is much steeper, so MECO/separation/SES happen much closer to the pad, horizontally. So the booster has (and needs) a lot less horizontal velocity to get to the landing pad, compared to an ASDS landing.

I'm skeptical that a 0.22" hole in a tank the size of Starship's would cause any huge issues by itself. The fuel and oxidizer flow is waaaaay higher than what you could squeeze out that hole, and the pressure isn't that high anyway--under 100 psi. Reentry is short enough that the volume you'd lose through such a hole wouldn't accumulate to an appreciable quantity, compared to the total amount in the tank. Even if the hole was in the vapor space, the volume in that tank is huge by comparison. I'd be more concerned about the bullet getting stopped by the liquid fuel, sucked into a turbopump, and blowing up an engine.

I wonder how much mass the soot adds.

Ok, dumb question: Is it worth it to push the engines that far, rather than just slapping a few more engines on? Musk is talking about an 8% increase in thrust from each engine, which is nothing to sniff at. But a few extra tons of engine mass on a launch vehicle weighing thousands of tons makes me wonder if it wouldn't be more prudent to baby the engines in order to improve reliability.

Ok, as a moderator for a previous circumnavigation challenge, I feel like I need to lawyer this one a bit: 1) Do we have to hold a Kerbal? 2) Only one Juno, but are other engines allowed? 3) camacju's entry uses a neat exploit that drastically reduces drag. Is that allowed?

In the video clip, Elon is talking about pressure stabilizing the fairing. And I'm confused, because I think of a fairing as a (historically) disposable aerodynamic cover that is not pressurized. Can someone enlighten me?

The idea of launching materials from the lunar surface is intriguing. The lack of atmosphere and shallow gravity well make it ...well maybe not practical, but perhaps less-unfeasible? I mean, you can use the Flats on Minmus to get to orbital velocities with no gravity losses, right? Let's see, it's about 1700 m/s dV to get from the Lunar surface to LLO. If you built a long, very straight track, and accelerated craft at 50m/s (5G), it would take about 34 seconds, and require a track (0.5 * 50m/s^2 * (34s * 34s) )= 29km long. That'd be a pretty substantial civil engineering project. But using such a system would eliminate most of the need for fuel, along with the nasty issue of kicking up the regolith on launch. If you wanted to go whole hog and get the payload on an escape trajectory back to earth, you'd need 2400m/s, and a 58km rail...

I suspect/hope that dramatically reduced launch costs will dramatically increase demand, for two reasons: 1) Supply and demand curve. Drop the price of something, and you'll get more customers. The lower price, IMO, will unleash all sorts of ideas that have never been considered before because of high launch costs. 2) Lower launch costs per ton will have a compounding effect on the cost of the actual payload, because your launch costs per kilogram are now $333 instead of $10,000 (or $2,500ish on F9). You no longer have to spend boatloads of money on engineering the lightest parts with the strongest (expensive) materials in order to fit within a tight weight budget. Since you can now launch 10x as much payload for the same cost, you don't have to worry quite as obsessively about failure rates, either. It may also enable more of a "throw science at the wall and see what sticks" approach. I watched the Smarter Every Day video about how they measured each layer of JWST's sun shield, within a few thousandths of an inch, in a clean room environment, just so they could validate their computer simulation model of how it would behave in space. This effort took several people several years, and is a teeny tiny portion of the overall engineering cost of the project. If SS/SH reduces costs as much as it's projected to, all sorts of lower-engineering-cost alternatives become viable. If I were NRO, I would be salivating right now. Apply JWST's folding mirror approach to a spy satellite, scale it up so it just barely fits in SS, and all of a sudden you're reading Putin's mail.

I think Hubble's a bit unique in that 1) It's still close to earth, and 2) still operational, and 3) it's famous to people of today. Here's a probably-silly idea: Launch a hubble replacement on SS into the same orbit, and recover Hubble on the same mission!

Can someone explain to me why EVA is safer at a lower altitude? I mean, you're still inside the Van Allen belts, and if something goes wrong, you're in the same trouble at 310km as you are at 850 miles.

I suspect this is a floating point issue, and not something that can be fixed.