4 ms·

Watching this as a maritime archaeology student, I was reminded of ancient seafarers, who built massive sailing platforms to support siege engines that frequent

Watching this as a maritime archaeology student, I was reminded of ancient seafarers, who built massive sailing platforms to support siege engines that frequently capsized in rough weather. Does anyone have insight into the thinking (and/or mathematics) that motivated this approach to landing a rocket?

trothamel 11y ago
When the rocket stages, it has significant horizontal motion (which is what matters - after the rocket is high enough to get out of the atmosphere, it has to speed up horizontally to achieve a stable orbit). Returning to the launch site requires cancelling that velocity out (and applying more horizontal velocity to return), while stationing the ASDS downrange means you mostly don't.
- pol0nium 11y ago
  That, plus the fact that landing far from inhabited regions is safer.
  - seanccox 11y ago
    I guess my question wasn't as clear as I thought it was. I understand landing it vertically, and I also understand the safety value of landing the rocket on a floating platform. What I don't understand is: Why it isn't obvious that a rocket of X height will fall over when landing on a boat of Y size in Z waves? Can you explain that element? In general terms, tall things on boats that aren't fastened down are the most likely things to tip over. That's something any sailor can tell you. I'm interested in what considerations were at play leading up to this accident. I don't know anything about rocketry, so I kinda need that explained to me in simple terms.
    - abeld 11y ago
      Someone mentioned before (in a comment on another similar news item) that although the rocket is tall, after landing most of its mass is at the bottom: the engines are heavy, while the rest of the rocket is mostly empty fuel tanks. Hence it is feasible to keep it upright with the relatively small legs.
      - seanccox 11y ago
        OK, that clears that up for me. Cheers!

trothamel 11y ago

When the rocket stages, it has significant horizontal motion (which is what matters - after the rocket is high enough to get out of the atmosphere, it has to speed up horizontally to achieve a stable orbit). Returning to the launch site requires cancelling that velocity out (and applying more horizontal velocity to return), while stationing the ASDS downrange means you mostly don't.

pol0nium 11y ago
That, plus the fact that landing far from inhabited regions is safer.
- seanccox 11y ago
  I guess my question wasn't as clear as I thought it was. I understand landing it vertically, and I also understand the safety value of landing the rocket on a floating platform. What I don't understand is: Why it isn't obvious that a rocket of X height will fall over when landing on a boat of Y size in Z waves? Can you explain that element? In general terms, tall things on boats that aren't fastened down are the most likely things to tip over. That's something any sailor can tell you. I'm interested in what considerations were at play leading up to this accident. I don't know anything about rocketry, so I kinda need that explained to me in simple terms.
  - abeld 11y ago
    Someone mentioned before (in a comment on another similar news item) that although the rocket is tall, after landing most of its mass is at the bottom: the engines are heavy, while the rest of the rocket is mostly empty fuel tanks. Hence it is feasible to keep it upright with the relatively small legs.
    - seanccox 11y ago
      OK, that clears that up for me. Cheers!