SpaceX: “Close, but no cigar. This time”

Post by grecy » Sat, Jan 17, 2015, 3:34 AM UTC

ggonweb wrote: post #127

ufmace wrote: post #4

Cool video! Just what we've been waiting to see. I wonder what actually exploded there? Part of the argument for why the landing was supposed to be relatively safe was that the stage would be mostly empty of fuel by the time that it landed, so there wouldn't be much to explode if something went wrong. So is that an explosion of the remaining fuel in the rocket, or something on deck?

This is the tweets by Elon Musk on this "Tks. Turns out we recovered some impact video frames from drone ship. It's kinda begging to be released…" " Before impact, fins lose power and go hardover. Engines fights to restore, but …" "Rocket hits hard at ~45 deg angle, smashing legs and engine section" "Residual fuel and oxygen combine " "Full RUD (rapid unscheduled disassembly) event. Ship is fine minor repairs. Exciti…

Post by schiffern » Sat, Jan 17, 2015, 3:43 AM UTC

jacquesm wrote: post #246

schiffern wrote: post #244

Earlier quoted context omitted.

FWIW, Musk makes no mention of expansion joints in the tube, only at the ends. He's also stated elsewhere (sorry, no source) that you'll probably need to run a polishing robot through the tube to get it microscopically smooth. That doesn't sound like a surfacing requirement that would tolerate gaps. If you care to, check out the conversation that sillysaurus3 and I had down-thread. I would love to have someone experi…

It might be, but if you did want to use expansion joints to alleviate some or all of the problem you most likely could. There are other alternatives too, such as allowing the tubing to move sideways a bit in a long curve. That would change the overall shape of the trajectory but the air cushion they talk about could take care of that. If they do end up using expansion joints they could actually use the fact that some…

Post by pjscott » Sat, Jan 17, 2015, 4:35 AM UTC

narag wrote: post #196

downandout wrote: post #176

Could an aeronautics person kindly explain why it's so hard to get this thing to land as it's supposed to? I'm not being judgmental at all here; I am saying that as a software engineer with no aeronautics experience, I simply don't understand the problem. Assuming all of the sensors indicating tilt, altitude, etc. are accurate, the software portion coordinating where and how much thrust needs to deployed to keep it l…

I wonder if the thin cylinder shape is to blame and if it would be easier to land if it sported a stabler shape. Can aerodynamics be compatible with something like a tetraedron mesh?

Post by shasheene » Sat, Jan 17, 2015, 4:58 AM UTC

32faction wrote: post #141

I feel if the 1st stage booster had an attitude control system toward the top like the BRAHMOS missile [1], the lean could've been corrected to at least have the rocket be upright when it impacted the platform. Although the choice to add an attitude control system would probably take up more space and add mass which is critical for a stage rocket. [1] http://i.imgur.com/5RWkvem.gif

Post by Hytosys » Sat, Jan 17, 2015, 5:47 AM UTC

sillysaurus3 wrote: post #243

jacquesm wrote: post #240

Earlier quoted context omitted.

You're not being insulted, you merely are trying to argue about things that you admit that you have no clue about and you persist in doing so regardless of the effort made to show you that you are wrong. So either stop arguing (I do know a thing or two about mechanical engineering) or start researching what I gave you above as the bits and pieces of the solution. What else do you want? A blueprint? A cad design?

To have an enjoyable conversation with an interested colleague, rather than someone whose tone is "shut up and listen to your elders." Besides, having a crotchety back-and-forth makes for boring reading, and we should be respectful of the community. Thanks for the pieces you've provided so far. I'll bring up my objections elsewhere. Hopefully anyone who's been having my same concerns will be able to do the same.